Control of Mineral Imbalances in Cattle and Sheep:
A Reference Manual for Advisers and Vets

Phil Rogers MRCVS⁽¹⁾ & Tom Gately MAgrSc, MS, PhD⁽²⁾

Contents | Tables | Acknowledgements | Comparative costs |

CONTENTS

Introduction | Background to the Teagasc Farm Nutrient Profile Service

PART 1: METHODS OF SUPPLEMENTATION

Minerals and Vitamins

Mineral stores in the body and timing of supplementation

Methods of mineral supplementation of cattle and sheep

Free-access systems (blocks, licks, loose minerals)

Rates of oral supplementation of stock with minerals

Trace element supplements for cattle and sheep

1. Effective oral trace element supplements for cattle and sheep
2. Periodic pasture dressing with trace elements
3. Oral trace elements via the water supply to grazing cattle
4. Veterinary products for trace element supplementation
5. Soil fertilisation with trace elements
6. Periodic drenching with trace element supplements
7. General warnings in connection with trace elements

PART 2 : CONTROL OF SPECIFIC MINERAL IMBALANCES IN STOCK

Control of Calcium (Ca) Imbalance, Hypocalcaemia and Milk Fever in Cattle and Sheep
Control of Cobalt (Co) Deficiency in Cattle and Sheep
Control of Copper (Cu) Deficiency/Molybdenum (Mo) Excess in Cattle and Sheep
Control of Iodine (I) Deficiency in Cattle and Sheep
Control of Magnesium (Mg) Deficiency, hypomagnesaemia and tetany in Cattle and Sheep
Control of Manganese (Mn) Deficiency in Cattle and Sheep
Control of Phosphorus (P) Deficiency in Cattle and Sheep
Control of Selenium (Se) Deficiency in Cattle and Sheep
Control of Selenium (Se) Toxicity in Cattle and Sheep
Control of Sodium (Na) Deficiency in Cattle and Sheep
Control of Zinc (Zn) Deficiency in Cattle and Sheep
Addendum: Comparative costs of mineral supplements for cows from 1 month pre- to 4 months post- calving

Summary

1. Commercial mineral-vitamin mixes
2. Oral trace element supplements alone
3. Veterinary products
4. Methods of last resort

Tables

Abbreviations used in the text
Suppliers of Trace Element Salts
Acknowledgements

This manual provides necessary information to be used in conjunction with the Teagasc Farm Nutrient Profile. It describes the various methods that may be used to correct and prevent mineral imbalances in cattle and sheep. The text will be used mainly by Teagasc advisers, to help them to make specific recommendations to their clients on the control of any mineral problem identified in the Farm Nutrient Profile.

The text will be useful also to other professionals who serve our cattle and sheep farmers: vets, agricultural consultants, nutritionists and specialists in the mineral mix and feed-compounding trade.

The information presented in the manual is both detailed and technical. It is not written for casual "lay" readers, but it will be useful to some of the progressive farmers who use the Teagasc Farm Nutrient Profile, or the Grange Blood Analysis Service. Therefore, farmers who read this manual are urged to discuss the various methods of control with their Teagasc advisers and veterinary surgeons, in order to select the most appropriate method for their farm and in order to have the calculations of the dose rates checked by competent professionals.

The manual is presented in two major parts:

1. METHODS OF SUPPLEMENTATION

Part 1 outlines the various the various appropriate methods and systems of mineral and trace element supplementation for cattle and sheep.

2. CONTROL OF MINERAL IMBALANCES

Part 2 presents the specific control measures for mineral imbalances, including rates of supplementation for each of the methods addressed in part 1.

BACKGROUND TO THE TEAGASC FARM NUTRIENT PROFILE SERVICE
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Apart from economic factors (low market prices, high input costs), the main causes of low profit margins in cattle and sheep enterprises are: reduced feed intake, poor quality winter feed, poor grassland management, parasitism and chronic infections.

Nationally, mineral imbalances are far less important to profit margins than those factors. However, mineral imbalances can cause major loss of profit to some farmers.

The Teagasc Farm Nutrient Profile is especially useful in investigating and correcting ongoing animal disorders associated with suspected mineral imbalances. It may be used also as a periodic check of the mineral status of farms, in order to forestall possible problems in the future.

Control and prevention of mineral imbalances are usually straight-forward, once the underlying imbalances and their causes are identified. Correction of the imbalances can help farmers to maximise the efficiency of their livestock enterprise.

The provision of a high-quality mineral-vitamin mix is the cheapest way of supplying a balanced cocktail of minerals and vitamins to stock. The most reliable way is to incorporate the correct amount of mineral-vitamin mix into the daily allowance of concentrate ration. The second best way is to divide the correct daily allowance of mineral-vitamin mix into 2 or 3 parts and to sprinkle the mix over the easy-feed or roughage diet in 2 or 3 times /d.

Mineral-vitamin mixes are based on simple compounds: salt, limestone, di-calcium phosphate, calcined magnesite, sodium selenite, potassium iodide or iodate and sulphates of copper, cobalt, manganese and zinc. Sweeteners and Vitamins A, D3 and E are usually added, together with agents to prevent rain-damage.

The formulation and blending of complex mixes is a specialist task. Farmers are advised not to undertake the task themselves but to use products from reliable manufacturers.

Commercial retail prices of mineral-vitamin mixes range from IR 200-1000/ tonne. The cheapest are not necessarily the worst, nor are the dearest necessarily the best. Some commercial mixes do not provide a good balance of minerals and vitamins. Therefore, farmers should discuss the suitability of various commercial products with their Teagasc advisers. Our advisers, backed up by specialists and research workers, are trained to assess, from the specification and the proposed daily allowance of the mix, the suitability of any commercial mix for different types of stock and for different diets. Farmers, having got this expert opinion, can select a cheap but effective mix to solve their problems. Alternatively, they may discover that they do not need to feed any minerals. For example, dairy cows are often fed 150 g of extra minerals/d for 90-120 days after calving (13.5-18.0 kg/cow at a cost of, say, IR 500/tonne). A dairy farmer with 80 cows could save 1-1.4 tonnes of expensive minerals (IR 500-700) per season if the minerals were not needed on silage and good dairy ration.

Many excellent veterinary products to correct mineral imbalances are available but they are expensive for routine control of multiple mineral imbalances. Although general dose rates of veterinary products and their usage are suggested in this manual, they may need alteration in specific cases. Farmers are urged to consult their own local vets as regards the most applicable and economic methods for their farm.

ESSENTIAL NUTRIENTS: Certain nutrients are essential for optimal animal health. They are in three classes: vitamins, major elements and trace elements.

Vitamins: Table 5 shows suggested daily vitamin supplements (iu/head/d) for stock. Most mineral mixes and blocks, especially those used in winter and spring, contain Vitamins A, D3 and E. Vitamins B1 and B12 are added occasionally. Vitamin activity usually declines with storage time in mineral supplements and compound feeds. In an effort to ensure that the product contains not less than the stated amount after some months of storage, many compounders add double the stated amount and some mineral-vitamin mixes contain 3-10 times more vitamins than are needed.

Vitamin A: Good pasture contains adequate levels and grass silage and green hay usually have adequate levels. However, cereals, bleached hay, straw, roots and byproducts of the alcohol-sugar industries can be low in vitamin A.

Vitamin D3: Sunlight, interacting with the skin, allows animals to synthesise their requirements of vitamin D3. A supplement is needed in winter when sunlight is scarce or animals are housed.

Vitamin E: Good pasture usually contains adequate levels of vitamin E. Though the level in freshly ensiled material may be high, fermentation processes and spoilage may reduce the vitamin E level before the silage is fed. Wet cereals or grains, bleached hay, straw, root crops and byproducts of the alcohol-sugar industries can be low in vitamin E. Storage of grain, especially that treated with propionic acid, can reduce vitamin E levels markedly. Some authorities recommend 100-1000 iu vitamin E/d for cows. These supplementation rates are much higher than those shown in Table 5 (240-300 iu/d). High levels of vitamin E are said to reduce mastitis incidence and milk cell counts.

B vitamins: Rumen microbes usually synthesise enough vitamins B1 and B12 to meet the animal's needs if the cobalt supply is adequate and if anti-vitamin factors (such as thiaminases) are absent. Thiaminases in the rumen can cause vitamin B1 deficiency, which can lead to cerebrocortical necrosis (CCN), blindness and nervous signs.

Vitamin supplements at pasture: Vitamin supplements (A, D3, E, B1 or B12) rarely are needed by cattle or sheep on good pasture. Possible exceptions are:

(a) As grass tetany is usually associated with stress and vitamin requirements can be increased by stress, it is advisable to include a vitamin supplement in mixes designed for tetany control in cows and ewes.

(b) High levels of vitamin E in the month before mating may improve fertility in cows and ewes and high levels of vitamin E may help to reduce the incidence of subclinical mastitis.

(c) If vitamin B1 or B12 deficiency is diagnosed, the relevant vitamin can be given, especially by injection, pending correction of the Co deficiency or removal of the anti-vitamin factors.

Vitamin supplements on winter feeds: Grass silage and cereal-protein concentrates are the most common winter feeds. Other feeds include hay, straw, byproducts (brewers' and distillers' grains, molasses, beetpulp etc), brassicas (rape, kale) and roots. Because winter feeds are so varied, it is difficult to formulate a minimum vitamin supplement to suit all situations. At least part of the daily total requirement of Vits A, D3 and E should be supplied during the winter. Depending on the feeds used, between 20 and 100% of the total daily requirement of the vitamins should be provided. (Total daily requirements for vitamins are usually higher than the daily rates of supplementation suggested in Table 5). There is no need for routine inclusion of B vitamins in winter supplements if Co status is adequate and if thiaminase levels are normal in the rumen.

Vitamin A: One should add 20-60% of the total daily requirement of vitamin A on diets of silage + concentrates and 50-100% of total daily requirement on other diets.

Vitamin D3: One should add 50-100% of the total daily requirement of vitamin D3 in winter.

Vitamin E: One should add 20-60% of the total daily requirement of vitamin E on diets of silage + concentrates and 50-100% of total daily requirement on other winter diets. High levels of vitamin E are needed when high levels of roots (e.g. fodder-beet) or grains (especially wet or propionic acid-treated grain) are fed.

Major elements: The major elements include calcium (Ca), phosphorus (P), magnesium (Mg) and sodium (Na). Nitrogen (N), potassium (K) and sulphur (S) can act as antagonists to other minerals.

Trace elements: The trace elements include cobalt (Co), copper (Cu), iodine (I), manganese (Mn), selenium (Se) and zinc (Zn). Molybdenum (Mo) and iron (Fe) are powerful Cu-antagonists.

Mineral imbalances and deficiencies are common in Irish herds and flocks. Mineral imbalance has 3 forms: (a) non-clinical, (b) sub-clinical and (c) clinical. Non-clinical imbalance is widespread and is more common than sub-clinical imbalance, which is more common than clinical imbalance.

(a) Non-clinical imbalance: Herd health and productivity are normal. Diagnosis is based on mineral imbalance in blood, feed or soil in the absence of health problems. Confirmation is by the absence of response to supplementation with the deficient mineral(s). If the price is cheap, mineral supplements are justified as an insurance against the possibility that non-clinical deficiency can become sub-clinical or clinical. A Pre-Calver mineral mix is a good investment, even in healthy herds, as it costs only 2.5-5.0 p/cow/d for the last month before calving.

(b) Sub-clinical imbalance: There are few or no clinical signs but productivity (fertility, growth rate, milk yield, milk quality) is depressed in 20-50% of the group. Diagnosis is difficult: other causes of poor performance (poor grassland quality or management, poor quality or quantity of winter feed, parasitism, chronic infections, sequels to calfhood diseases etc) must be eliminated. Then, a severe mineral imbalance in blood, feed or soil is suggestive. Confirmation is by a dramatic response in productivity to supplementation with the deficient mineral(s). Some herds with uncorrected sub-clinical signs may develop clinical signs later.

(c) Clinical imbalance: Some or all of the clinical signs are present in 10-30% or more of the herd and another 10-40% usually have lower product-ivity (subclinical signs). Diagnosis is based on the history, clinical signs and, sometimes, post-mortem findings. It is confirmed by blood, feed and soil tests and by a dramatic response to supplementation with the deficient mineral(s).

Mineral imbalances may arise singly or in various combinations. Imbalances of major elements (Ca, P, Mg, Na) may cause rickets, lameness, milk fever, lambing sickness, tetany, reduced appetite, reduced milk yield and depraved appetite. Deficiency of trace elements (Co, Cu, I, Mn, Se, Zn) may cause illthrift, abortion/placental retention/perinatal calf and lamb deaths, reduced immunity in calves, lambs, cattle and sheep, susceptibility to bacteria and parasites, infertility in cows and ewes, reduced fertility in bulls and rams, lowered milk yield, lameness, slow healing of wounds and poor skin/hair/fleece quality.

Differential diagnosis: Such clinical and subclinical problems can arise due to many causes other than mineral imbalances. Therefore, before the cause of such problems is attributed to mineral imbalances, the vet should examine the herd or flock (to eliminate other disorders, such as chronic poisoning, parasitism, infection etc). Meanwhile, the Teagasc adviser should examine the management, housing, farming practices etc. Finally, laboratory tests (blood, feed, soil, as in the Teagasc Farm Nutrient Profile) can identify specific mineral imbalances.

In herds or flocks with clinical or subclinical disorders, once the nature and severity of the mineral imbalances are recognised, they usually can be treated and prevented by provision of the correct balance of mineral supplements. However, in herds or flocks with non-clinical disorders, mineral supplementation usually does not improve profitability in the short-term. However, if the price is cheap, mineral supplements may be justified as an insurance against the possibility that non-clinical deficiency can become sub-clinical or clinical.

Mineral mix formulations: Examples of mineral mix formulations, suggested rates of oral supplementation with minerals and vitamins, suggested levels of trace element levels in finished rations and carriers, Mg levels in cow and ewe rations and the mineral content and price of common trace element compounds are given in Tables 1 to 10.

Mineral stores in the body: Minerals can be classed into three types as regards effective stores and recycling in the body:

Good stores and recycling (Ca, P, Na, Cu, Se): These elements can be short in the diet for weeks or months without causing observable problems, provided that the body stores were "full" before the period of shortage. In that period, mobilisation from the stores helps to maintain normal levels in blood, body fluids of cells that need those minerals. If a period of plentiful supply of the element follows a period of shortage, the stores are replenished again. Thus, months of supplementation with Cu and Se indoors confers good protection for a period after turnout, even if the supplements are removed at turnout. As a rough guide, 1 month indoors on a high Cu or Se supplement before turnout confers about 1 month's cover after removal of the supplement at turnout.

Medium stores and recycling (I): These elements have medium stores, which give protection for only 2-3 weeks in periods of shortage. Thus, months of supplementation with I indoors may not maintain I status during the breeding period at grass if I supplements are removed at turnout to I-deficient pasture. In I-deficient groups, oral I doses are needed daily, but doses at 1-2 week intervals also are effective.

Poor stores and recycling (Mg, Co): Although bone and other body cells contain a lot of Mg, those stores are "locked", i.e. are not available for release in times of Mg shortage. Thus, provision of Mg supplement for weeks before the tetany risk period has little value, except to train the animals to take the supplement. Mg supplement is needed daily throughout the risk period. Co has no effective recycling in ruminants and no effective store exists in the body. Therefore, Co-deficient animals need Co supplement very frequently, preferably daily, although dosing at intervals of 14 days is effective in Co-deficient stock.

Timing of administration of mineral supplements (including veterinary products) depends on the timing of the clinical or subclinical problems.

In chronic conditions, such as illthrift, infertility, depressed milk yield, chronic scour etc, give supplements in time to allow them to act for some weeks before the expected onset of the problem.

In herds or flocks with problems confined to late pregnancy, parturition or early calf/lamb losses, the dams are treated in late pregnancy. For example, to prevent stillbirth in calves due to I deficiency, the dams are treated with I (orally or by skin application) for 4-5 weeks before calving; to prevent swayback in lambs in Cu-deficient flocks, the ewes are treated (preferably by Cu oxide capsules) at mid pregnancy; to prevent stillbirth/weak calf syndrome/placental retention in cows, due to Se deficiency, the cows are treated about 1 month before calving; to prevent infertility in cows, due to Mo-induced Cu deficiency, the cows are treated soon after calving, as Cu given pre-calving is diverted to the foetus and little remains for the cow post-partum; to prevent infertility in cows, due to Se deficiency, the cows are treated soon after calving, or about 1 month before breeding. To prevent illthrift or scouring in calves, yearling cattle and lambs, due to Cu deficiency, begin treatment about 1 month before the expected onset of the problem.

Dosage and frequency of administration of veterinary products as mineral supplements depends on the weight of the animals, the degree of challenge to the mineral status and the chemical potency and form of the compound to be administered. Although general dose rates of veterinary products and their usage are suggested in this manual, they may need alteration in specific cases. Farmers are urged to consult their own local vets as regards the most applicable and economic methods for their farm. Heavier animals need larger doses. More frequent doses are needed in groups exposed to high challenge, such as on feeds that contain antagonists to the deficient mineral. Some products are short-acting; others are long-acting. See the sections on the Control of specific deficiencies (below).

Mineral mix formulations: Examples of mineral mix formulations, suggested rates of oral supplementation with minerals and vitamins, suggested trace element levels in finished rations and carriers, Mg levels in cow and ewe rations and the mineral content and price of common trace element compounds are given in Tables 1 to 10.

Normal mineral status in animals usually can be ensured if adequate mineral supplements are given. These are justified if the health history suggests clinical or sub-clinical signs of deficiency. They may also be justified in high-yielding healthy (non-clinical) herds, as a preventative to non-clinical deficiency becoming sub-clinical or clinical. Methods of Mineral Supplementation

Warning: Mineral supplements for use in calved cows have different formulations to those for use in dry-cows or dry stock. Mineral supplements for use in lambed ewes have different formulations to those for use in dry-ewes or lambs. Do not feed cattle minerals to sheep and vice-versa.

General methods of mineral supplementation: Mineral supplements may be given in many ways (oral supplements, water medication, veterinary products, foliar dusting or spraying or mineral application to soil). Whichever method is chosen, the correct dose or application rate is essential.

Mineralised concentrate rations: If mineral mixes are not fed, ensure that Co, Cu, I, Mn, Se and Zn (at least) are included in the concentrate feed for cows (see Table 6).

Mineral mixes are best fed in the concentrate ration or sprinkled over easy-feed silage 2-3 times/d, or mixed with 3-4 times their weight of palatable carrier (say molassed beet pulp, or rolled barley 94% + molasses 6%). Use reputable minerals and feed at the recommended rates only.

Free-access systems (blocks, licks, loose minerals): Daily intake of minerals by free-access to blocks, licks and loose minerals in troughs is very variable between animals. Free-access systems (wet or dry licks, blocks, loose minerals in troughs etc) are not as reliable as fixed-rate daily mineral supplementation. This is especially so in winter, when fixed-rate mineral feeding is easy. Even at grass, fixed-rate mineral feeding in feed, palatable carrier, or water is more reliable than free-access systems. Fixed-rate feeding of supplements is much more reliable in preventing mineral/vitamin deficiency in animals.

Table 1 shows mineral mix formulations for cows and ewes. Table 2 shows mineral mix formulations for drystock (cattle and lambs). Table 3, Table 4 and Table 5 show suggested optimum supplementation levels of Major Elements, Trace Elements and Vitamins respectively for Irish livestock. In the absence of other mineral sources, such as in compound ration or as veterinary medication, supplements for long-term routine use that provide less than the minimum amounts of major- or trace elements in the daily intake are inferior.

Levels of oral mineral/vitamin supplements advised by different National Advisory Groups vary considerably. The rates given in Table 3, Table 4 and Table 5 are guidelines for cattle reared under Irish conditions. Irish research showed that the Cu and Se requirement of cattle is higher than in other countries. Thus, the suggested supplementation rates of Cu and Se are higher than "international standards". (Pending a 2-year reassessment of the daily requirements for Se, the rates in Table 4 are recommended). The suggested vitamin allowances are also higher than those from some other authorities.

The best methods of trace element supplementation are:

1. effective oral supplements;
2. foliar spraying;
3. chelated trace elements in the drinking water;
4. effective veterinary products.
5. Soil application may be considered in simple deficiency of Co, Se or Cu.
6. Periodic drenching at intervals of 2-3 weeks may be considered also.

 

1. Effective oral trace element supplements for cattle and sheep
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   Daily oral supplementation rates: Optimum daily oral supplementation rates of trace elements for cattle and sheep under Irish conditions are shown in Table 4.

   Optimum daily oral supplementation rates for cows are: Se 3-5 mg; Co 5-10 mg; Cu 150-450 mg; I 12-60 mg; Mn 335-415 (and maybe 980) mg; Zn 335-750 mg/cow/d. These dose rates ignore the trace element levels in forage and roughage. Oral supplements (in compound feed, mineral mixes, blocks, etc.) that give those amounts daily ensure normal trace elements status pre- and/or post-calving.

   Oral supplements that provide less than the minimum daily allowance are unlikely to be effective. If in doubt, choose medium levels, i.e. 300 mg Cu, 4 mg Se, 7.5 mg Co, 45 mg I, 563 mg Zn and 400 mg Mn/cow/d. However, the upper levels were used widely without problemsin recent yearsprovided that no other supplements were used.

   European Community (EC) Regulation on Trace Elements in feed: The EC (Additives in Feedingstuffs) (Amendment) regulation, 1991, S.I. No. 124 of 1991 gives the following as the maximum content of trace element in the complete feedingstuff for cattle and sheep, and the value converted to mg/kg DM, assuming a DM content of 88% in "complete feeds":

   Element	Animal type	Max level (mg/kg) permitted in complete feed	Max level (mg/kg DM) permitted (assuming 88% DM in "complete feed")
   Cobalt (Co)	Cattle/sheep	10	11.36
   Copper (Cu)	Sheep	15	17.05
   	Calves, milk replacer	30	34.09
   	Calves, other complete feedingstuffs	50	56.82
   	Other species and categories (cattle)	35	39.77
   Iodine (I)	Cattle/sheep	10	11.36
   Manganese (Mn)	Cattle/sheep	250	284.09
   Selenium (Se)	Cattle/sheep	0.50	0.57
   Zinc (Zn)	Cattle/sheep	250	284.09

   Assuming a dry matter (DM) of 88% in complete feedingstuffs and a DM intake of 2-3% of liveweight (LW), maximum daily trace element intake from the complete diet allowed for 650 kg cows under EU regulations are: Se 7.4-11.1 mg; Co 143-215 mg; Cu 515-776 mg; I 143-215 mg; Mn 3693-5540 mg; Zn 3693-5540 mg/cow/d.

   Thus, the supplementation levels that we recommend for Co, I, Mn and Zn are well within the maxima permitted under current EC regulations, even at the lower DM intake (2% of LW) and the recommended supplementation levels for Se and Cu are just below the maxima permitted under current EC regulations at the lower DM intake (2% of LW), and are well below the maxima allowed at DM intakes of 3% of LW. [Our Se and Cu recommendations are higher than those used in many other countries but they are made on the basis of years of research in cattle under Irish conditions and the recommendations are under continuing review]

   Minerals in the concentrate ration: Accurate formulation of the concentrate diet is the best and cheapest way to give oral supplements. No other mineral supplement is needed if the diet is properly balanced. Table 6 shows the trace element levels in compound dairy concentrate to give the daily allowances shown in Table 4.

   Carriers for trace elements: Small amounts of carrier can be used to supply cattle and sheep with optimum amounts of trace elements. The carrier can be rolled barley or beet pulp, to which the correct amount of minerals are added. If the carrier is to be group-fed in troughs, it is essential to allow adequate trough-space and to add molasses (5% total weight) to make it very palatable. The amounts of carrier (including minerals and molasses) needed are:

   Cows and adult cattle	450 g
   Yearling cattle	350 g
   Weanling cattle	250 g
   Ewes	112 g
   Lambs	6 g/10 kg LW

    

    

   Table 7 shows the formulation of carriers to supply the daily trace element allowances in Table 4.

   Dairy or beef cows pre-calving

   If cows have mineral-related problems at calving (milk fever in more than 8% of cows or retained placenta in more than 4% of cows) or total calf losses above 8% (including late abortion + perinatal calf deaths + deaths within 3 weeks of birth), then a pre-calver (dry-cow) mineral, high in trace elements, fed for 4-6 weeks before calving may be used. As the cost is small, a Pre-Calver mineral is a good insurance against perinatal problems in intensive dairy herds and in pedigree beef cows.

   Minerals in concentrate ration: Beef cows seldom, if ever, are fed concentrates pre-calving. Although most dairy farmers feed no concentrates pre-calving, some do. If concentrates are fed, the feed compounder may be persuaded to adjust the levels of trace elements in the dry-cow concentrate, so that the daily supply of concentrate gives the desired amounts (see Table 4). For example, if the farmer normally feeds 2 kg of concentrate/cow/d, ensure that it contains 75-225 mg/kg Cu, 1.5-2.5 mg/kg Se, 2.5-5.0 mg/kg Co, 15-30 mg/kg I, 188-375 mg/kg Zn and 175-225 mg/kg Mn, as fed. If less than or greater than 2 kg is fed, adjust the mineral/vitamin levels up or down (as in Table 6), so that the desired amount of mineral/vitamin goes into the daily allowance of concentrate.

   Minerals in a palatable carrier: A good quality pre-calving mineral mix can be fed in a palatable carrier to dairy cows (total allowance 450 g/cow/d. If the pre-calving mineral is to be fed at 100 g/cow/ day, the formulation of the medicated carrier is: 100 g pre-calving mineral + 329 g rolled barley + 21 g molasses) = total 450 g/cow/d. This can be fed once/d in the parlour. It can be fed also in troughs, provided all cows can get access together. Alternatively, it can be sprinkled over the easy-feed 225 g/cow, twice/d).

   Pre-calving mineral mixes: The usual feeding rate is 100 g of mineral mix/head/d. To reduce milk fever risk, insist on low-Ca (0-6%) and high-Mg (13-17%) levels in pre-calving mineral mixes. P levels are optional in the range (0-14%), depending on the forage. (Cows on good silage need little or no P supplement pre-calving). Na (as salt) is the usual "filler". The Na content can range from 5-18%.

   Insist on high trace element levels (especially Cu, Se, Co and I) in pre-calving mineral mixes, i.e. 1500-4500 mg/kg Cu, 30-50 mg/kg Se, 50-100 mg/kg Co, 300-600 mg/kg I, 3350-5000 mg/kg Zn and 3350-4150 mg/kg Mn if the feeding rate is 100 g/cow/d. Sprinkle the mix 2-3 times/d (50-33 g/cow each time) over the easy-feed silage. See Table 1, which also shows mineral mix formulations for ewes in late pregnancy.

   Lactating dairy or beef cows indoors

   After calving, the demand for Ca, P and Na increases for lactation. Many silages are marginally low in P and Na and high-yielding cows should normally get Ca, P and Na supplements on silage. Consider feeding mineral mixes high in trace elements during the winter, unless the compound feed is known to supply adequately high levels of trace elements.

   Minerals in concentrate ration: Dairy cows usually get concentrates indoors after calving but beef cows seldom do. The feed compounder may be persuaded to adjust the levels of trace elements in the dairy concentrate, so that the daily supply of concentrate gives the desired amounts (see Table 4). For example, if the feeding rate is normally 6 kg concentrate/cow, insist on 25-75 mg/kg Cu, 0.50-0.85 mg/kg Se, 0.84-1.67 mg/kg Co, 5-10 mg/kg I, 63-125 mg/kg Zn and 58-75 mg/kg Mn in the concentrate, as fed. If less than or greater than 6 kg is fed, adjust the mineral/vitamin levels up or down, so that the desired amount of mineral/vitamin goes into the daily allowance of concentrate. Table 6 shows the correct formulation of dairy rations to provide the amounts of trace elements recommended in Table 4.

   Post-calving mineral mixes for housed cows: If usual feeding rate is about 125 g of mineral mix/head/d use a mineral mix with 7-17% Ca, 7-17% P, 4-10% Mg, 7-20% Na, depending on the type of forage and concentrate fed.

   Ensure that post-calving mineral mixes are high in trace elements (especially Cu, Se, Co and I). If fed at 125 g/cow/d, use a mineral mix with 1200-3600 mg/kg Cu, 24-40 mg/kg Se, 40-80 mg/kg Co, 240-480 mg/kg I, 2680-6000 mg/kg Zn and 2680-3320 mg/kg Mn. If less than or greater than 125 g/cow/d is fed, adjust the mineral/vitamin levels in the mix up or down, so that the desired amount (see Table 4) of mineral/vitamin goes into the daily allowance of mix. See Table 1, which also shows mineral mix formulations for ewes in post-lambing.

   Lactating cows at grass: During the period of tetany risk, dairy and beef cows need a daily supplement of Mg (see Control of Mg deficiency, hypomagnesaemia and tetany). Most farmers reduce or stop the feeding of concentrates after cows go to grass, but many are prepared to feed minerals in a carrier.

   Mineral mix in a carrier for cows at grass: To guarantee mineral intake by cows at grass, a good quality post-calving mineral mix can be fed in a palatable carrier (total allowance 450 g/cow/d. During the period of tetany risk, if Mg supplements are not given in another way, use a mineral mix with 13-31% (say 21%) Mg, in order to supply 20-40 g (say 30 g) Mg/cow/d in 130-150 g (say 150 g) of mineral mix/cow/d. If fed at 150 g/cow/d, use a mineral mix with 1000-3000 mg/kg Cu, 20-33 mg/kg Se, 33-67 mg/kg Co, 200-400 mg/kg I, 2500-5000 mg/kg Zn and 2200-2767 mg/kg Mn. If less than or greater than 150 g/cow/d is fed, adjust the mineral/vitamin levels in the mix up or down, so that the desired amount (see Table 4) of mineral/vitamin goes into the daily allowance of mix. If the post-calving mineral is to be fed at 150 g/cow/d, the formulation of the medicated carrier is: 150 g post-calving mineral + 281 g rolled barley + 19 g molasses) = total 450 g/cow/d. This can be fed once/d in the parlour. It can be fed also in troughs, provided all cows can get access together. See Table 1, which also shows mineral mix formulations for lambed ewes at risk of tetany.

   High I supplements for cows: If it is difficult to locate mineral mixes with I levels 400-600 mg/kg for use in cows, one may use a good standard mix (300 mg/kg I), plus a special iodised salt (1000 mg/kg I), 30 g of which supplies 30 mg I. Alternatively, 5% tincture of I (1 ml/cow, giving 50 mg I/cow) can be mixed in the trough water each day, or 7 ml of 5% tincture of I can be painted onto the thin skin of the pocket of the flank fold once per week for 5 weeks before calving or breeding.

   Mineral mixes for drystock (cattle and lambs): Table 2 gives formulations of trace elements in mineral mixes for drystock (cattle and lambs). The usual feeding rate of minerals to cattle is about 20 g/100 kg LW (110 g to fattening cattle at 550 kg). The usual feeding rate of minerals to lambs is about 8 g/20 kg LW (24 g to fat lambs at 60 kg).

   As with cows and ewes, mineral mixes can be fed to cattle and lambs in many ways: incorporated in the concentrate ration, sprinkled over easy-feed silage 2-3 times/d, or mixed with 3-4 times their weight of palatable carrier (say molassed beet pulp, or rolled barley 94% + molasses 6%).

    

    

2. Periodic pasture spraying with trace elements
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   Table 4 gives the suggested optimum oral supplementation levels of Trace Elements for stock. Oral supplementation (Part 1.a above), is the usual method of supplying trace elements but periodic pasture spraying may be a practical alternative for some farmers.

   Periodic pasture spraying with soluble salts of specific trace elements (such as Zn, Mn, Co, I, Se and Cu** (see footnote) can be used to provide those elements to grazing cattle or sheep that are confirmed to be deficient in them. The method has the advantage of being easy to use. [** Administration of oral Cu oxide capsules is the safest way to supplement sheep with Cu. While Cu may be administered to sheep by pasture spray, there is a risk of Cu-poisoning, especially in susceptible breeds, such as Texels, some continental breeds, and their crosses]

   Pasture spraying avoids the need dose each animal individually. For safe and effective control by pasture spraying, the following criteria must be met:

   Suitable sprayers: Usually, tractor-mounted sprayers are needed. This limits the usefulness of the method, as many farmers may not have the equipment.

   Frequency of spraying: Co and I have little or no storage or recycling in ruminants. Therefore, they must be given very regularly. For best results, repeat the spraying at intervals of 2 weeks.

   Adequate grass cover: The plots, just large enough to be grazed out in 1-2 days by the affected group, must have 9-11 cm grass cover (to hold the spray). Short grass or open swards may not hold the spray effectively.

   Optimal pasture height for intensive sheep production is 4-6 cm. Mean sward height of 6 cm or less may not have enough leaf area to hold 50% of the spray. In that case, a value of 2.5-3.0 may need to be assigned to factor (F) in the calculation of the amount of salt to apply (see method of calculation of spray rate, below). But, increasing the value of factor (F) increases the risk of toxicity if retention rate of the spray is much higher than expected. Thus, drenching sheep with trace element solutions every 2 weeks may be safer than pasture spraying on closely grazed swards.

   Dry weather only: Spraying may be considered only in dry weather. Soluble salts sprayed on grass are washed off easily by rain. The grass must remain dry during the period of supplementation.

   Trace element content of the salts used: Before calculating the amount of spray, double-check the mineral content in each salt to be used. See Table 10.

   Calculation of correct spraying rates for a 2-week supply

   Apply the correct amount of each salt evenly as a spray to the whole plot every 2 weeks. Excessive amounts or uneven spraying may carry a risk of toxicity. The calculation for each trace element salt is:

   T = (S.F.D.N.100/P)/(1000), where:

   T = total amount of the salt (g) for the group every 2 weeks

   S = supplementation rate of the element (mg/head/d), as in Table 4

   F = factor to allow for loss of salt by spraying. A loss of 50% is usually assumed. Thus the value of f is 2.

   D = number of days supply. This is usually set at 14.

   N = number of stock in each category to be supplemented

   100/P = factor to convert element to its common salt (100/percentage of element in the salt used)

   1000 = factor to convert milligrams of the salt to grams.

   Example 1: A group of 750 strong lambs is confirmed as needing routine Co and Cu supplement. The owner wants to spray grass with Co sulphate, (21% Co) and Cu sulphate (25.4% Cu) and to take the risk of Cu poisoning. The suggested Co and Cu supplement (see Table 4) for strong lambs is 0.4-1.0 mg Co/head/d (say 1 mg/head/d) and 0-12 mg Cu /head/d (say 6 mg Cu/head/d for strong lambs). The calculation of T is:

   (Co sulphate)

   T = (S . F . D . N . 100 /P ) / (1000) =

   (1 X 2 X 14 X 750 X 100 /21 ) / (1000) = 100.0 g

   (Cu sulphate)

   T = (S . F . D . N . 100 /P ) / (1000) =

   (6 X 2 X 14 X 750 X 100 /25.4) / (1000) = 496.1 g

   Thus, a spray of 100 g Co sulphate and 496 g Cu sulphate (see footnote 5) in water would be applied evenly to a well-grown sward in a plot large enough to carry 750 strong lambs for 1-2 days. This is enough for the 750 lambs, assuming that no rain falls while the lambs are in the sprayed plot. The procedure would be repeated once every 2 weeks.

   Example 2: A group of 75 cows at pasture is confirmed as needing I and Se supplement routinely (sprayed on grass as potassium iodide, 76.4% I and Na selenite, 30% Se). The suggested I and Se supplement (see Table 4) for cows is 12-60 mg I/head/d (say 50 mg/head/d) and 3-5 mg Se/head/d (say 5 mg/head/d). The calculation of T is:

   (Potassium iodide)

   T = (S . F . D . N . 100 / P ) / (1000) =

   (50 X 2 X 14 X 75 X 100 / 76.4) / (1000) = 137.4 g

   (Na selenite)

   T = (S . F . D . N . 100 / P ) / (1000) =

   (5 X 2 X 14 X 75 X 100 / 30 ) / (1000) = 35 g

   Thus, a spray of 137 g potassium iodide and 35 g Na selenite in water would be applied evenly to a well-grown sward in a plot large enough to carry 75 cows for 1-2 days. This is enough for the 75 cows, assuming that no rain falls while the cows are in the sprayed plot. The procedure would be repeated once every 2 weeks.

   Warning as regards pasture spraying: If too much spray is applied, there is a risk of poisoning stock. If too little is applied, full benefit may not be got. If the correct amount of spray is applied evenly to herbage, there is little risk of toxicity from elements such as Co, I, Mn, Zn. However, spraying with Cu or Se may be dangerous unless Cu or Se deficiency is confirmed beforehand. See also the warnings re the danger of oral Cu in sheep. Pasture spraying has the disadvantage that suckling lambs or calves may eat little grass and, thus, may get little or no supplement from sprayed grass.

    

3. Oral trace elements via the water supply to grazing cattle
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   Water medication successfully controls parasitism, bloat, hypomagnesaemia and other conditions in grazing cattle if the correct levels of additives or drugs are added to drinking water. Water intake by cattle varies by up to 15-fold between days, depending on the weather. For example, cows may drink only 5-10 l (1-2 gal) on cold, wet days but may drink 50-75 l (10-15 gal) on hot, sunny days.

   Pumps versus simple dispensers: Soluble medicaments can be added to the water in two ways: by a pump (plumbed into the mains supply) or by a simple plastic dispenser floated in the trough.

   Pumps usually maintain a fixed concentration of medicament in the water. As weather conditions vary widely between days, intake of water and the water-soluble medicament also varies by up to 15-fold between days. Therefore, pumps delivering a fixed dose/water ratio can not ensure an even intake of medicament on a day-to-day basis.

   Dispensers: Water medication, via a Ruakura-type plastic dispenser, with compounds that remain in solution has advantages over pumps and over oral free access supplements. (Dispensers are technically better than pumps. Due to wide variation in water intake between days, day-to-day variation in mineral-dose intake can be 7-14-fold, or more, from water medicated by pumps that maintain a constant dose level in water). A predetermined daily dose can be added to the water trough. This reduces day-to-day variation in mean intake of dose to almost zero, irrespective of day-to-day variation in mean water intake. Between-animal variation in dose intake in any given day is likely to be as little as 2 to 4-fold, as compared with 10 to 30-fold or more on free-access supplements.

   Inorganic trace elements in water: Up to 85% of some compounds (say Cu sulphate) precipitate in water troughs. Cattle that drink the water may get only a small fraction of the intended dose. Also, the precipitate can accumulate in the troughs, posing a risk of toxicity after some months. Thus, water medication with some inorganic trace element compounds can be dangerous.

   Water medication with chelated trace elements: Soluble chelates stay dissolved in water for long periods. They do not precipitate, as do inorganic trace elements. However, chelation may increase or decrease the absorption of the minerals by animals, depending on the chemical form of the chelate. Also, 40-90% of water drunk by cattle may by-pass the rumen, via the oesophageal groove. [Rumen by-pass of medicated water has been used to supply nutrients such as protein and B vitamins direct to the abomasum of cattle]-. Thus, water-borne minerals could be poorly utilised by cattle if the main site of absorption is in the rumen.

   Teagasc is researching a new commercial product (Flotrace) that contains chelated trace elements (Cu, Co, Se, I). A trial in drystock in 1990 gave very good results via Ruakura dispensers in the water troughs but blood samples in 1991 from dairy cows on the product gave disappointing results. The dose rate needed by cows may be higher than was provided.

   Water medication with tincture of I: If I deficiency is the only trace element deficiency on the farm, medication of water with 66 mg potassium iodide or 1 ml of tincture of I (5% I)/cow/d is effective. Amounts for other stock or sheep would be pro-rata by body weight. The daily dose should be divided in 2 or 3 parts, added 2 or 3 times/d to ensure that all stock get an even share of the dose.

   Clean troughs: To ensure that water intake remains high and to reduce the risk of chemical interaction with added medication (especially inorganic salts, such as potassium iodide or tincture of I), troughs should be cleaned out regularly.

    

4. Veterinary Products for Trace Element Supplementation
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   Effectiveness of veterinary products: Some veterinary products are excellent; others are not. Before they are used, deficiency of the specific mineral(s) should have been confirmed by blood or other tests.

   The correct dose or frequency of administration of each product must be used. If the dose is inadequate or is not given frequently enough, otherwise excellent products can give poor results. For example, because of the severity of challenge to Cu status (high Mo in feed or high soil/Fe intake), the required dose rate of Cu (or its frequency of use) in Irish herds is often 2-3 times the dose or frequency that is recommended in the United Kingdom. If excessive doses are used, there may be a risk of toxicity, especially with Cu products.

   Excellent products that supply a single trace element include: Cu-EDTA injection (100 mg Cu (subcutaneous) gives 6-12 weeks protection in cattle, but is a less preferred way to supplement with Cu) and CuO capsules (24 g CuO orally gives 2-4 months protection in cattle). Barium selenate injections (100 mg Se/100 kg LW (subcutaneous) gave disappointing results after a change of manufacturer in 1991, but gave satisfactory results in later years. [Sodium selenate or selenite injection (up to 10 mg Se/100 kg live weight, s/c) is much cheaper than barium selenate, but is short-acting. Protection lasts only 4-6 weeks. Depending on the herd-health history, frequent sodium selenate / selenite injections may be needed].

   If only one trace element deficiency (say Cu or Se deficiency) exists in a herd, effective veterinary products have advantages over oral supplements. However, some are expensive if used at the dose or frequency of administration needed in Irish herds.

   Bullets that supply 3 or more trace elements are available on the Irish market. They are given orally by a special bulleting gun. The products include "Cosecure" and the post-1991 "Alltrace". The special glass matrix of the bullets is slowly soluble in the reticulo-rumen and releases its supplement over a period of about 6-10 months. "Cosecure" and the new "Alltrace" are similar as regards control of Co, Se and Cu deficiencies. "Ionox" is a new bolus, released on the Irish market in autumn 1996. The bolus was developed in cooperation with Teagasc, Grange.

   "Cosecure" (Cooper Pitman-Moore), average weight 100 g/bullet; contains 500 mg Co, 300 mg Se and 13400 mg Cu/bullet. Three to five bullets/year would meet the Co, Se, Cu requirements of cows in severely deficient herds.

   "Alltrace" (Agrimin): In September 1991, Agrimin improved the formulation of their bullets. Each weighs 107 g and contains 240 mg Co, 245 mg Se and 16532 mg Cu. Three to five bullets/year would meet the Co, Se, Cu requirements of cows in severely Cu-deficient herds. As they are so low, its levels of other trace-elements (I, Zn etc) can be ignored.

   "Ionox" (Bayer Ireland): This cattle bolus is designed to remain in the reticulorumen during its period of trace element release; it contains 3500 mg I, 500 mg Se and 350 mg Co/bolus. Assuming linear release over a mean time of 28 weeks, mean release would be 18, 2.6 and 1.8 mg I, Se and Co/bolus/d respectively. This should be adequate for yearling cattle on pastures that pose a risk of severe deficiency of I, Se or Co. If no other I, Se or Co supplements were given, adult cows would need 2-3 boluses every 5-6 months on similar high-risk pastures.

   Multiple trace element deficiency often occurs in Irish herds. In that case, routine use of multiple veterinary products can be very expensive. Even if "Cosecure", "Alltrace" or "Ionox" bullets can be used, as 3-5 bullets/cow/year are needed under Irish conditions, oral mineral supplements may be considered as a good alternative on economic grounds. Note that Ionox contains no Cu; it is not for use as a Cu supplement.

   Poor veterinary products: Under Irish law, veterinary surgeons may prescribe any permitted product that they think fit. Most products are effective and safe if the correct dose is used in the correct circumstances. However, some are less effective than others: the manufacturer's recommended dose is too small to release the amount of required active ingredient per day to meet the animal's needs.

   Three products of questionable value in cows are: Mg bullets (to prevent hypomagnesaemia), "Alltrace" bullets (to prevent deficiency of Mn, Zn or I) and Iodine injection (to prevent I deficiency).

   Mg bullets: To give 20-40 g Mg/cow/d from Mg bullets that release 1 g Mg/d/bullet would require 20-40 bullets/cow. The usual dose of 2-4 bullets/cow is too small by a factor of 10. Mg bullets may be considered for use in suckler cows on outfarms but 4-6 bullets/cow are advisable every 4-5 weeks.

   "Alltrace" bullets: In 1991, Agrimin improved the formulation of their bullets. They now weigh 107 g/bullet and contain 0.22% Co, 0.23% Se and 15.45% Cu by weight. As discussed above, these can be considered in Cu, Se and Co deficiency, if 3-5 bullets/cow are used. Over an expected life of 8 months (240 days), the mean daily release from 4 Alltrace bullets would be 275 mg Cu, 4 mg Co and 4 mg Se. These would be useful supplements of Cu, Co and Se under Irish conditions (somewhat below the optimum values in Table 4).

   Each bullet also contains 12.7% Zn, 8.3% Mn, 0.236% I, 557000 iu Vit A, 111500 iu Vit D3 and 1115 iu Vit E but the levels of these components released from 4 Alltrace bullets are too low to be useful in seriously deficient Irish herds, as they are well below those recommended in Table 4 and Table 5. About 6-30 bullets would be needed to supply enough Zn, Mn, I, and vitamins to rectify deficiency of those elements in cows. The cost would be prohibitive and the Cu and Se release from 6-30 bullets would be too high in any case.

   Iodine injection: [Lipiodol is not registered as a veterinary therapeutic product by the National Drugs Advisory Board]. Oil-based I injections (such as Lipiodol, 40% I) sometimes are used to supply I in I-deficient herds. The oil-based products are slow-acting and we are unaware of controlled work published in refereed scientific journals that shows that they prevent neonatal problems in cows. We are also aware of failure of I injection to prevent stillbirth in calves, which was controlled within days by oral I supplements.

    

5. Soil fertilisation with trace elements
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   Why apply trace elements to soil ? The main reason for applying trace elements to soil is to try to raise the level of trace element in herbage, in an attempt to correct the economic effects of the deficiency in animals. However, soil application fails to control severe induced or secondary trace element deficiency in animals, such as that due to antagonists in the feed. Trace element fertilisation does not eliminate antagonists from the feed nor does it increase grass growth.

   Soil application may be effective in simple deficiency of Co, Se and Cu.

   In simple Co deficiency, where soil Co levels are low and soil Mn levels are normal (below 500 mg/kg), application of Co sulphate (2.24 kg/ha every 3-4 years) can raise herbage Co to normal levels. [Only 1/15^th to 1/30^th of the soil applied-Co would be effective if given directly to stock as an oral supplement (20-40 mg Co sulphate/cow/d X 365 d = 7.3-14.6 g/cow/year)].

   In simple Se deficiency, annual application of Na selenite (150 g/ha) can raise herbage Se to normal levels. Herbage Se levels above 3 mg/kg DM (the toxic level) can arise for some weeks after application. Serious over-application of Se salts can lead to Se toxicity in stock. [Only 1/8^th to 1/17^th of the soil applied-Se would be effective if given directly to stock as an oral supplement (12-24 mg Na selenite/cow/d X 365 d = 4.38-8.76 g/cow/year)].

   In simple Cu deficiency, application of Cu sulphate (22 kg/ha) can increase herbage Cu to marginal or normal levels for 7-12 years after application. As Cu hydroxide is less subject to leaching, it may last longer than Cu sulphate on sandy soils.

   Warnings: The correct amounts of trace elements must be mixed carefully in sand or fertiliser before application with a spreader or pneumatic drill. If too little is applied, the method may fail to control the animal problem. If too much is applied, there is risk of toxicity. Trace element salts should be applied to bare pasture. To limit the risk of accidental toxicity, allow time for the salts to be washed into the soil. Herbage regrowth should not be grazed for some weeks afterwards. Because of the risk of Cu toxicity, do not apply Cu to soils on sheep farms.

    

6. Periodic drenching with trace element supplements
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Simple trace element drenches and anthelmintics with added trace elements: Simple trace element drenches can be made up by veterinary surgeons or chemists. They may contain Se, I, Co and Cu, singly or in various combinations. Some commercial anthelmintic drenches also contain added trace elements, such as Co and Se. Such drenches can be used to prevent or control trace element deficiency under most circumstances in Irish flocks and herds, provided that they contain nutritionally effective levels of the required trace element(s) and are given at intervals of 2-3 weeks.

Warnings on the use of periodic drenches of trace elements: The label or accompanying leaflet on the drench should contain the following warnings:

* Shake container well between every few doses. Many drenches, especially those combining anthelmintics and trace elements, are not solutions: they are colloidal suspensions. If the container is not shaken frequently during use, de-mixing of the colloidal suspension can cause sedimentation of trace elements. The upper layer of the suspension may contain low concentrations of trace elements and the lower layer may contain toxic levels. Animals dosed from the upper layer may get too little supplement. Those drenched from the lower layer can die of acute poisoning within 1-3 days of drenching.

* Copper poisoning: Sheep, especially Island breeds (Texel, Ronaldsay, Soay breeds etc) are easily poisoned with copper. Sheep should not receive copper in drenches, mineral mixes, licks etc unless Cu deficiency has been diagnosed in the flock by a veterinary surgeon, on blood test and/or on clinical/post-mortem findings. If sheep need a Cu supplement, dosing with oral Cu oxide capsules or Cu-containing glass boluses is safer than feeding/drenching/ injecting copper compounds. For example, CuO particles in a gelatin capsule can be given at doses of 4 g (ewes), 2 g (store lambs) or 1 g (lambs 1-2 months of age). Dose once or twice/year, as needed.

Cattle can die following Cu drenches if they inhale part of the drench or if the dose is too high.

* Selenium poisoning: Se poisoning occurs in a few localised areas in Ireland, due to toxic Se levels in soil and herbage. Do not dose with Se compounds within 5 miles of known Se-toxic areas, unless Se deficiency has been diagnosed in the flock or herd by a veterinary surgeon, on blood test and/or clinical/post-mortem findings.

Formulation of a trace element drench for sheep: In practice, depending on the specific deficiencies identified on the farm, only 1-3 of the ingredients are used together and the unwanted ingredients are omitted from the formulation. (See warnings on copper and selenium above). The following can be used:

17.5 g Sodium selenite (30.0% Se) = 5.25 g Se

61.0 g Potassium iodide (76.4% I) = 46.6 g I

100.0 g Cobalt sulphate (21.0% Co) = 21.0 g Co

413.4 g Copper sulphate (25.4% Cu) = 105.0 g Cu**

Add water to 15 litres. Shake until ingredients are fully dissolved.

** Omit Cu except on veterinary advice. See Warning above.

Label for the drench: The drench should be labelled clearly, as follows:

1. Poison. For animal treatment only. Keep away from children. Use only in sheep and only as directed. See warnings on attached leaflet. Shake the drench well between every few doses.
2. Fifteen litres of Stock Solution is sufficient for 2 weeks for 750 ewes, 1071 store lambs or 2143 weaned lambs. Do not exceed the recommended dose rates. Overdosing may poison sheep.
3. When all four compounds are included, the Stock Solution contains 7 mg Cu, 3.1 mg I, 1.4 mg Co and 0.35 mg Se per ml. The fortnightly dose (20 ml/ewe) contains 140 mg Cu, 62 mg I, 28 mg Co and 7 mg Se. This is equivalent to an average daily dose of 10 mg Cu, 4.4 mg I, 2 mg Co and 0.5 mg Se per ewe. The fortnightly dose is 14 ml for stores and 7 ml for weaned lambs).
4. Drench every 2 weeks for best results in flocks at risk of Co and I deficiency. Dosing at intervals of more than 3 weeks may not control those deficiencies fully.
5. Dose:

 

Ewes	20 ml/head/2 weeks (or 30.0 ml/head/3 weeks)
Store lambs	14 ml/head/2 weeks (or 21.0 ml/head/3 weeks)
Lambs at weaning	7 ml/head/2 weeks (or 10.5 ml/head/3 weeks)

Formulation of a trace element drench for cattle: In practice, depending on the specific deficiencies identified on the farm, only 1-3 of the ingredients are used together and the unwanted ingredients are omitted from the formulation. (See warnings on copper and selenium above). The following can be used:

35.0 g Sodium selenite (30.0% Se) = 10.5 g Se

100.0 g Cobalt sulphate (21.0% Co) = 21.0 g Co

137.4 g Potassium iodide (76.4% I) = 105.0 g I

2480.3 g Copper sulphate (25.4% Cu) = 630.0 g Cu**

Add water to 30 litres. Shake until ingredients are fully dissolved.

** Omit Cu except on veterinary advice. See Warning above.

Label for the drench: The drench should be labelled clearly, as follows:

1. Poison. For animal treatment only. Keep away from children. Use only in cattle and only as directed. See warnings on attached leaflet. Shake the drench well between every few doses.
2. Thirty litres of Stock Solution is sufficient for 2 weeks for 150 cows, 300 stores or 900 weanlings. Do not exceed the recommended dose rates. Overdosing may poison stock.
3. When all four compounds are included, the Stock Solution contains 21 mg Cu, 3.5 mg I, 0.7 mg Co and 0.35 mg Se per ml. The fortnightly dose (200 ml/cow) contains 4200 mg Cu, 700 mg I, 140 mg Co and 70 mg Se. This is equivalent to an average daily dose of 300 mg Cu, 50 mg I, 10 mg Co and 5 mg Se per cow. The fortnightly dose is 200 ml for cows, 100 ml for 300 kg stores and 33 ml for 100 kg weanling calves).
4. Drench every 2 weeks for best results in herds at risk of Co and I deficiency. Dosing at intervals of more than 3 weeks may not control those deficiencies fully.
5. Dose

 

1. General warnings in connection with trace elements
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1. Products high in trace elements may be toxic. Avoid products high in trace elements, unless they are labelled clearly with instructions as to their correct use: the species, type and age of animal for which they are intended (cattle, sheep; young or adult; dry or lactating) and the daily feeding rate, for example: "Feed only to (specify dry or lactating) cows. The allowance is "X" (specify g or kg/cow/d). Do not exceed that amount".
2. Correct doses: Adhere strictly to the recommended daily allowances or dosages. Commercial concentrate rations, mineral supplements and veterinary products may give too little trace elements if used at low levels, or too much if used at high levels. Incorrect doses pose a risk of under-dosing or toxicity.
3. Iron (Fe) is a strong Cu-antagonist. Keep Fe < 2500 mg/kg in mineral mixes for cows on green feeds/roots, or omit it altogether.
4. Specific warnings: See Part (f), above, for warnings on the use of periodic drenching with trace elements. See also the specific warnings under the sections on each element below.

Summary: The main methods of routine prevention are: to control body condition at calving; to minimise Ca intake in late pregnancy; to ensure adequate Mg intake pre-calving; to minimise stress at calving; to optimise feed intake on the day of calving. If all else fails, give large doses of oral Ca +/- P supplement just before and after calving. Calcium carbonate (34% Ca) and di-calcium phosphate (22% Ca, 18% P) are common Ca salts.

Body score at calving: Control of energy intake pre-partum is essential. Feed cows so that they calve in good body condition (not too fat, not too thin). If body condition is too good, restrict energy intake and if cows/heifers are too thin, supplement energy intake.

Minimise Ca intake by cows in late pregnancy. Total intakes of 25-50 g Ca/d are ideal but are unattainable, as most common pre-partum diets of herbage or silage supply more than 55 g/cow/d. However pre-partum Ca intake can be reduced by feed restriction (if this is appropriate, considering the body condition of the cows and the quality of the forage on offer) and/or the use of low-Ca feeds (such as grains and roots). Reduced Ca intake pre-partum ensures maximal Ca absorption percentage from the digesta. If the forage has Ca > 0.4% in DM, avoid Ca supplements pre-calving, or keep them below 6 g Ca/cow/d. Pre-calver mineral mixes with 0% Ca are preferable in herds with a milk fever history. Avoid mineral mixes pre-calving if the Ca level exceeds 6%.

Mg supplements pre-calving: Inclusion of 10-20 g Mg/cow/d (say 15 g) in dry-cow supplements (about 15% Mg in mineral mixes fed pre-calving), ensures high turnover of bone Ca pre-partum.

Minimise stress at calving: Minimising stress reduces adrenalin release and fat mobilisation at calving and their adverse effects on blood Ca levels. Comfortable calving boxes and provision of shelter and warmth at calving help. Keep interference to a minimum by use of closed-circuit TV monitors and careful use of calving jacks.

Palatable feed on the day of calving: Molassed concentrates + good silage or hay enhances feed and Ca intake.

P supplements pre-calving: The most common diets of pre-partum cows are herbage and grass silage. These have ample P for dry cows. If low-P forages (such as beetpulp, fodderbeet etc) are fed, up to 20 g P/cow /d may be added. P supplements pre-calving have little effect in preventing parturient hypocalcaemia, except at impractically high levels (30-50 g P or more/cow/d).

Oral Ca +/- P on the day of calving: If parturient hypocalcaemia or milk fever occurs in spite of the methods suggested above, dosing or feeding susceptible cows with a very high Ca supplement on three occasions close to calving helps: 125 g feed-grade limestone flour (42.5-45.0 g Ca) is given 12-24h prepartum; the dose is repeated just after calving and at 12h later. If low blood P levels coexist with low blood Ca levels, 3 doses of 180 g di-calcium phosphate can be used instead of the limestone.

Ca supplements during lactation: After calving, give high yielding cows (especially those on low-Ca feeds (roots, high cereal diet)) a supplement of 7-25 g Ca/cow/d. A Ca level of the order of 0.90% is advisable in dairy concentrates fed at 7 kg/cow to high yielders. If the dairy ration has > 6% fat, it is advisable to increase Ca levels to 1.0-1.2% in the concentrate and to add Zn at high levels (750 mg Zn/cow/d).

Veterinary Products to prevent Milk Fever: Vitamin D3 injection: Injection of vitamin D3 or its synthetic analogues (cholecalciferol etc) within 8 days pre-calving was claimed to improve Ca absorption from the gut, to increase Ca mobilisation from bone to blood and to reduce the incidence of milk fever. The claims are contentious. Results are mixed; side effects may arise and milk fever may be delayed, only to arise 10 days later. The method is expensive but may be used together with the methods described above in valuable cows with a history of milk fever in previous calvings.

Summary: Co deficiency can be simple (low levels in soil and feed) or induced by high soil manganese (Mn), which prevents uptake of Co by herbage. Oral Co is the main method of correction of Co deficiency. Co sulphate (21.0% Co) is a common Co salt. Co by injection has no value.

Effective oral Co supplements: Co has no effective recycling in ruminants and no effective store exists in the body. Therefore, Co-deficient animals need Co at very frequent intervals. Co can be given in the concentrate ration or forage, in a carrier or in mineral mixes. Oral Co is usually cheaper than Co-fertilisation. See also Part 1.a, above.

Daily supplement: An oral supplement of 5-10 mg Co/cow/d can be used to rectify or prevent Co deficiency, under Irish conditions. A supplement of 5.0-7.5 mg/cow/d may suffice in mild deficiency but 7.5-10.0 mg/cow/d may be needed in severe deficiency. Table 4 shows the suggested optimum supplementation levels of Co for other classes of stock.

Co in the concentrate ration: If the concentrate is properly balanced, no other Co supplement is needed while ration is fed. See Table 6 for Co levels in dairy concentrate to provide cows with 5-10 mg Co/head/ day. If weanling cattle (250 kg) need Co supplement (2-4 mg Co/head/ day), and 1 kg concentrate is to be fed, it should contain 2-4 mg Co/kg. If ewes need Co supplement (0.5-2.0 mg Co/head/d), and 0.8 kg concentrate is to be fed, it should contain 0.63-2.5 mg Co/kg. If lambs need Co supplement (0.2-0.7 mg Co/head/d), and 0.4 kg concentrate is to be fed, it should contain 0.5-1.75 mg Co/kg.

Co in a small amount of carrier: Table 7 shows carrier formulations for cows, ewes, cattle and lambs. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers).

Co in a mineral mix: Table 1 shows mineral mix formulations for cows and ewes. Table 2 shows mineral mix formulations for drystock (cattle and lambs). See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Drenching sheep or cattle with Co: Periodic drenching with oral Co sulphate is effective if adequate doses are given often enough. A 14 to 21 day supply of Co can be given in drenches every 2-3 weeks during the grazing season. A dose of 111.1 mg Co sulphate (23.33 mg Co)/100 kg LW every 2 weeks or 166.7 mg Co sulphate (35 mg Co)/100 kg LW every 3 weeks is enough for cattle. A dose of 133.3 mg Co sulphate (28 mg Co)/70 kg LW every 2 weeks or 200 mg Co sulphate (42 mg Co)/70 kg LW every 3 weeks is enough for sheep. (For further details and warnings, see Part 1.f and Part 1.g, above).

Pasture spraying with Co Sulphate: Foliar spraying of "hospital plots" with Co sulphate (21% Co) in water every 14-21 days may be considered in simple Co deficiency and in Mn-induced Co deficiency. The basic daily supplement is about 7.93 mg Co sulphate/100 kg cattle LW or about 9.5 mg Co sulphate/70 kg sheep LW. To allow for Co falling to the ground, the basic amount of Co is doubled. A suggested dose for foliar spraying every 14 days is 222.1 mg Co sulphate/100 kg cattle LW or 266 mg Co sulphate/70 kg sheep LW. (See Part 1.b, above, for details).

Oral Co via the water supply to grazing cattle: Co can be given in chelated form in the water supply to grazing cattle (see Part 1.c, above). The daily Co supplement for cattle is shown in Table 4.

Co bullets may also be considered, especially in Co-deficient sheep. Some bullets may become coated and some may be regurgitated. For optimum results, give enough bullets to release 1-2 mg Co/d in lambs and ewes respectively.

"Cosecure" bullets (Cooper Pitman-Moore): Each cattle bullet contains 500 mg Co/bullet. In severely Co-deficient herds, 1-2 bullets per year meet the Co requirements in calves, 2 bullets per year in yearling cattle and 4 bullets per year in cows.

"Alltrace" bullets (Agrimin): Each cattle bullet contains 240 mg Co/bullet. The daily release of Co from 2 "Alltrace" bullets (2 mg Co/d) is enough for calves in severely Co deficient herds but 4-6 bullets (4-6 mg Co released/d) would be needed to control Co deficiency in cows and adult cattle.

"Ionox boluses" (Bayer Ireland): Each cattle bolus contains 350 mg Co. Mean daily Co release would be 1.8 mg Co/d respectively. This should be adequate for yearlings on pastures that pose a risk of severe deficiency of Co. If no other Co supplements were given, adult cows would need 2 boluses every 5-6 months on similar high-risk pastures.

Vitamin B12 injection: In Co deficiency, with severe anaemia or other signs in sheep or cattle, vitamin B12 injection of affected cases may save life. Then give all animals an adequate Co supplement.

Soil fertilisation with Co sulphate: Simple Co deficiency: The method is useful in simple Co deficiency. See Part 1.e, above.

Secondary Co deficiency induced by soil Mn above 500 mg/kg: Application of Co sulphate to soil is of little or no value if soil Co is normal to low and soil Mn is high. In that case, if there are signs of Co deficiency with decreased animal productivity, supplementary Co must be given directly (orally) to the affected groups of animals.

Summary: Cu deficiency can be simple (low levels in soil and feed) or induced by high levels of Cu-antagonists in the diet (Mo, soil, Fe, factors in lush grass, S in sheep). Use of veterinary Cu products and oral Cu are the main method of correction of Cu deficiency. Cu sulphate (25.4% Cu) is a common Cu salt. One may use pasture management to reduce the intake of Cu-antagonists also. In simple Cu deficiency, soil application of Cu may be considered.

Warning: Some breeds of sheep are easily poisoned with Cu. Give oral Cu to sheep only on specific veterinary advice. Cu sulphate drench, if it accidentally enters the lungs, can cause shock and death in cattle as well as sheep.

Effective oral Cu supplements: Cu can be given in the concentrate ration or forage, in a carrier or in mineral mixes. See also Part 1.a, above.

Daily supplement: An oral supplement of 150-450 mg Cu/cow/d can be used to rectify or prevent Cu deficiency, under Irish conditions: 150-300 mg Cu/cow/d may suffice in mild deficiency but 300-450 mg Cu/cow/d (and, occasionally more) may be needed in severe deficiency, such as in high Mo areas. Table 4 shows the suggested optimum supplementation levels of Cu for other classes of stock.

Cu in the concentrate ration: If the concentrate ration is properly balanced, no other Cu supplement is needed while ration is fed. See Table 6 for Cu levels in dairy concentrate to provide cows with 150-450 mg Cu/head/d. If weanling cattle (250 kg) need Cu supplement (68-182 mg Cu/head/d), and 1 kg concentrate is to be fed, it should contain 68-182 mg Cu/kg. If ewes need Cu supplement (0-18 mg Cu/head/ day), and 0.8 kg concentrate is to be fed, it should contain 0-22.5 mg Cu/kg. If lambs need Cu supplement (0-14 mg Cu/head/d), and 0.4 kg concentrate is to be fed, it should contain 0-35 mg Cu/kg.

Cu in a small amount of carrier: Table 7 shows carrier formulations for cows, ewes, cattle and lambs. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers).

Cu in a mineral mix: Table 1 shows mineral mix formulations for cows and ewes. Table 2 shows mineral mix formulations for drystock (cattle and lambs). See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Drenching sheep or cattle with Cu: Periodic drenching with oral Cu sulphate may be considered if adequate doses are given often enough. A 14 to 21 day supply of Cu can be given in drenches every 2-3 weeks during the grazing season. A dose of 2.8 g Cu sulphate (700 mg Cu)/100 kg LW every 2 weeks or 4.2 g Cu sulphate (1050 mg Cu)/100 kg LW every 3 weeks is enough for cattle. A dose of 560 mg Cu sulphate (140 mg Cu)/70 kg LW every 2 weeks or 840 mg Cu sulphate (210 mg Cu)/70 kg LW every 3 weeks is enough for sheep. For further details and warnings, see Part 1.f and Part 1.g, above.

Pasture spraying with Cu sulphate: Foliar spraying of "hospital plots" with Cu sulphate in water every 14-21 days may be considered in simple and induced Cu deficiency. The basic daily supplement is about 196.8 mg Cu sulphate/100 kg cattle LW or about 39.4 mg Cu sulphate/70 kg sheep LW. To allow for Cu falling to the ground, the basic amount of Cu is doubled. A suggested dose for foliar spraying every 14 days is 5.5 g Cu sulphate/100 kg cattle LW or 1.1 g Cu sulphate/70 kg sheep LW. (See Part 1.b, above, for details).

Warning: Do not use this method for sheep except under veterinary advice

Oral Cu via the water supply to grazing cattle: Cu can be given in chelated form in the water supply to grazing cattle (see Part 1.c, above). The daily Cu supplement is shown in Table 4.

Veterinary products for Cu Supplementation: Veterinary Cu supplements include injections, boluses and bullets containing Cu compounds. Because Mo challenge is high in Ireland, the annual Cu dose needed to control diagnosed Cu deficiency is greater than is the case in the U.K. For general discussion of timing of administration of Cu compounds, see Mineral Storage in the Body and Timing of Administration of Supplements.

Cu treatment of calves: Suckler calves in Cu-deficient herds may show illthrift by 3-4 months of age. In such herds, treatment of the dam in late pregnancy and of the calves from 1 month of age may be needed. Bucket-reared calves usually have a much higher Cu status at birth and at 2-3 months of age than that of suckler calves. They seldom need Cu-treatment before 6-9 months of age.

Cu treatment of lambs: Lambs in Cu-deficient flocks may show illthrift pre-weaning, but especially post-weaning. In such flocks, treatment of the dam in late pregnancy and of the lambs from 1 month of age may be needed. Cu oxide capsules are the safest treatment (see next page).

Dosage and frequency of administration of Cu compounds depends on the weight of the animals and on the degree of challenge to Cu status. Heavier animals need larger doses. More frequent doses are needed in groups exposed to high challenge, such as on high-Mo farms. (See footnote 9).

Cu injections: There are many injectable Cu compounds. Intramuscular injections are not recommended, as they may damage meat. Avoid Cu injections within 4-6 weeks before mating and during the breeding season, as the pain/swellings may reduce conception rates. (Cu bullets, boluses or oral Cu supplements are preferable during the mating period).

Cu-EDTA (sub-cutaneous) is very effective. [Other Cu compounds may be used instead, but Cu-EDTA is the most widely used form of injectable Cu. It gives very good results in normalising Cu status, but has disadvantages that render it undesirable for routine use in the national herd]. Cu-deficient suckler calves 50-100 kg LW are usually given 50 mg Cu. The dose for cattle is 100 mg Cu, repeated as needed. In Irish cattle, one shot lasts 6-12 weeks, depending on the challenge to Cu status. On high-Mo farms, young-stock and yearlings may need 3-4 shots per year. In marginal deficiency, 2 shots/year may suffice. The number of shots per cow depends on the clinical problems in the cows. If abortions, stillbirths and infertility are due to Cu deficiency, at least three shots are needed: one in mid pregnancy, one about 5 weeks before calving and one very soon after calving. (The pregnant cow shunts most of the injected Cu to the foetus and may have little in her reserve depot (liver) after calving).

Warnings regarding Cu injections: All Cu-injections are irritant. If possible, avoid the use of Cu injections in animals destined for slaughter, as abscesses and scarring of tissues can follow injection. Avoid especially Cu-EDTA or other irritant injections during or less than 1 month before the breeding season. Local reaction to irritant compounds may depress conception rates by up to 20 points. If Cu is needed, oral CuO capsules or other oral Cu supplements are preferable at this time. Use Cu injections in sheep only on specific veterinary advice. High mortality from Cu poisoning may occur within days after injection of Cu compounds in sheep.

Cu oxide capsules or boluses are the preferred veterinary product for use as a copper supplement for cattle and sheep. These gelatin capsules contain Cu oxide particles. They are given orally with a special bulleting-gun. Optimum doses for Irish cattle in moderately deficient herds are 8 g Cu oxide/100 kg LW annually. Longer protection can be got from 2 doses/year at 4 g/100 kg LW each time than from the whole dose given at one time. In severely deficient herds, especially on high-Mo farms, 16-20 g Cu oxide/100 kg LW annually may be needed. Longer protection can be got from 4-5 doses/year at 4 g/100 kg LW each time than from the whole dose given at one time. CuO capsules can be used safely during the breeding season, whereas Cu-EDTA injection can depress conception rates.

Treatment with CuO capsules is the safest way to supplement sheep with Cu. The dose of CuO is: ewes 4 g; weaned lambs 2 g; young lambs 1 g. The dose may have to be repeated every 4-6 months, especially if the challenge to Cu status is severe.

Cu bullets: Glass bullets that supply Cu are available ("Alltrace" and "Cosecure"). The bullets are given orally by a special bulleting gun. The special glass matrix is slowly soluble in the reticulo-rumen and releases its supplement over a period of about 6-10 months.

"Alltrace" bullets (Agrimin): Each cattle bullet contains 16532 mg Cu. The daily release of Cu from 2 "Alltrace" bullets (138 mg Cu/d) is enough for calves in severely Cu deficient herds and for store cattle in marginally deficient herds. Cows or adult cattle in severely Cu-deficient herds may need 3-5 "Alltrace" bullets per year.

"Cosecure" bullets (Cooper Pitman-Moore): Each bullet contains 13400 mg Cu. Two bullets to calves (108 kg) gave satisfactory Cu levels in cattle on an Irish high-Mo farm for at least 6 months. The daily release of Cu (149 mg Cu/d) from 2 "Cosecure" bullets is also adequate for calves in severely Cu deficient herds and for store cattle in marginally deficient herds. Cows or adult cattle in severely Cu-deficient herds may need 3-5 "Cosecure" bullets per year.

"Ionox" boluses (Bayer Ireland) are NOT Cu supplements, as they contain no Cu.

Soil fertilisation with Cu: Secondary Cu deficiency induced by Cu antagonists: If Cu antagonists are present (high Mo, lush grass, high soil intake, high sulphate intake in water etc), soil application of Cu seldom if ever is effective in correcting Cu deficiency in stock and it is necessary to give Cu directly to the affected group.

Simple Cu deficiency: The method is useful in simple Cu deficiency. See Part 1.e, above.

Pasture management and reduction of Cu antagonists: The severity of induced Cu deficiency in cattle can be reduced by changes in pasture management and nutrition by:

Minimising herbage Mo levels (by maintaining soil pH below 6.2 (reducing LR by 2-3 tons/ac); by applying S fertilisers; by reducing clover content of pasture);

Minimising intake of Mo (by increasing the conservation of herbage from moory or low-lying or poorly drained high-Mo areas; by shortening the period spent grazing such areas). Winter feed conserved from high-Mo areas can be high in Mo, but usually is less dangerous to Cu status than fresh herbage grazed in situ;

Minimising the intake of other antagonists (reducing stocking rate and soil intake on bare pasture; reducing the intake of Fe-rich water and sulphuric acid additives without added Cu; avoiding excessive use of N and K fertilisers to reduce the lushness of grass etc).

Summary: I deficiency can be simple (low levels in soil and feed) or induced by high levels of I-antagonists in the diet (goitrogens, factors in lush grass, high Ca intake). Oral I is the main method of correction of I deficiency. Potassium iodide (76.4% I) is a common I salt. In addition, reduce the intake of I-antagonists.

Effective oral I supplements: I can be given in the concentrate ration or forage, in a carrier or in mineral mixes. See also Part 1.a, above. Oral I supplements, or 8.4 ml of 5% tincture of I painted or sprayed onto the thin skin of the pocket of the flank fold once per week, for 5 weeks before calving and before and during breeding in cows are the preferred options.

Daily supplement: An oral supplement of 12-60 mg I/cow/d can be used to rectify or prevent I deficiency, under Irish conditions. A supplement of 12-36 mg/cow/d may suffice in mild deficiency but 36-60 mg/cow/d may be needed in severe deficiency, especially on goitrogenic feeds and on diets high in Ca. Table 4 shows the suggested optimum supplementation levels of I for other classes of stock.

I in the concentrate ration: If the concentrate is properly balanced, no other I supplement is needed while ration is fed. See Table 6 for I levels in dairy concentrate to provide cows with 30-60 mg I/head/d. If weanling cattle (250 kg) need I supplement (4-28 mg I/head/d), and 1 kg concentrate is to be fed, it should contain 4-28 mg I/kg. If ewes need I supplement (2.4-6.0 mg I/head/d), and 0.8 kg concentrate is to be fed, it should contain 3.0-7.5 mg I/kg. If lambs need I supplement (0.8-2.0 mg I/head/d), and 0.4 kg concentrate is to be fed, it should contain 2-5 mg I/kg.

I in a small amount of carrier: Table 7 shows carrier formulations for cows, ewes, cattle and lambs. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers).

I in a mineral mix: Table 1 shows mineral mix formulations for cows and ewes. Table 2 shows mineral mix formulations for drystock (cattle and lambs). See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Drenching sheep or cattle with I: Periodic drenching with oral I (as potassium iodide) may be considered if adequate doses are given often enough. A 14 to 21 day supply of I can be given in drenches every 2-3 weeks during the grazing season. A dose of 153.5 mg potassium iodide (117.2 mg I)/100 kg LW every 2 weeks or 230.2 mg potassium iodide (175.9 mg I)/100 kg LW every 3 weeks is enough for cattle. A dose of 81 mg potassium iodide (62 mg I)/70 kg LW every 2 weeks or 122 mg potassium iodide (93 mg I)/70 kg LW every 3 weeks is enough for sheep. (For further details and warnings, see Part 1.f and Part 1.g, above).

Pasture spraying with I: Foliar spraying of "hospital plots" with potassium iodide in water every 14-21 days may be considered in simple and induced I deficiency. The basic daily supplement is about 13 mg potassium iodide/100 kg cattle LW or about 7.8 mg potassium iodide/70 kg sheep LW. To allow for I falling to the ground, the basic amount of I is doubled. A suggested dose for foliar spraying every 14 days is 364 mg potassium iodide/100 kg cattle LW or 218.4 mg potassium iodide/70 kg sheep LW. (See Part 1.b, above, for details).

Oral I via the water supply to grazing cattle: I can be given in chelated form in the water supply to grazing cattle (see Part 1.c, above). The daily I supplement for cattle is shown in Table 4.

Iodine via the water supply: Addition of 1 ml/cow/d of 5% tincture of iodine (or 2 ml/cow/d of 2.5% tincture) to the trough water would supply 50 mg I/cow/d, double the amount released by 24 "Alltrace" bullets (see next section). Add the herd dose in 2 or 3 parts daily, rather than adding it all together. An alternative is to add 66 mg KI or 0.5 ml of 10% linament of I/cow/d to the water supply, preferably in 2 or 3 divided doses. The cheapest method is to add 2 ml of 4% porassium iodide (KI) solution/cow/d.

Aquadyne tablets via trough water: "Slow-release" I-tablets are available from Mayo Healthcare (Westport). Each tablet has 420 mg I. To medicate the trough water for a herd of cattle, the dose (D) of Aquadyne tablets is calculated as follows:

1. Estimate the total liveweight of the cattle to be dosed (TLW, in kg).

2. Decide on the dosing interval (DI, in days). DI should be every 1 to 7 days, say twice/week, or a 3.5-day interval).

3. D = (TLW * DI/4200). Thus, a herd of Friesian cows (or other Friesian cattle), with a total estimated liveweight of about 34500 kg, would need 34500 * 1/4200 = 8.2 (say 8-9) tablets at intervals of 1 d, or 34500 * 3.5/4200 = 28.75 (say 29) tablets twice/week.

At the pre-decided dose interval, fresh tablets are added a to a simple dispenser, which is immersed in the water trough. Spent tablets are removed, as needed, from the opposite end of the dispenser.

 Veterinary products for I supplementation: These include 2.5 or 5.0% tincture of I, or 10% linament of I (from any chemist), I bullets and I injections. I do not recommend I bullets or I injections for cows for the following reasons:

"Ionox boluses" (Bayer Ireland): Each cattle bolus contains 3500 mg I/bolus. Mean release would be 18 mg I/bolus/d. This should be adequate for yearling cattle on pastures that pose a risk of severe deficiency of I. If no other I supplements were given, adult cows would need 2 boluses every 5-6 months on similar high-risk pastures.

Other I bullets: Other bullets are available. The bullets are given orally by a special bulleting gun. The daily release (2.1 mg I/d) from 2 "Alltrace" bullets would not be adequate for store cattle or adult cattle under Irish conditions. To provide 25 mg I/cow/d, about 24 "Alltrace" bullets would be needed.

I injections: Oil-based I injections (such as Lipiodol, 40% I) are used sometimes to supply I in I-deficient herds or flocks. Lipiodol is not registered as a veterinary product. Its injection in ewes in early pregnancy has reduced the incidence of goitrous lambs in some trials abroad. The product is slow-acting and we are unaware of published work in refereed scientific journals that shows that it prevents perinatal calf losses, placental retention or infertility in cows. In a study in Moorepark by the late Dr. Harry Greene, the incidence of stillbirth in 1262 calves from Lipiodol-treated cows was 5.2%, as compared with 3.3% of 1257 calves from untreated control cows. This represented an increased stillbirth incidence of 57% in calves from Lipiodol-treated cows. We also know of farmers who have failed to prevent stillbirth in calves from I-deficient cows injected with Lipiodol but who had success within days by feeding an oral I supplement.

Tincture of I applied to the skin: 7 ml/cow/week of 5% tincture of I (or 14 ml of 2.5% tincture) painted or sprayed onto the thin skin of the pocket of the flank fold weekly for 5 weeks before calving or breeding in cows is a cheap, safe and effective I supplement.

Soil fertilisation with I: If I deficiency reduces animal performance, I supplements must be given directly to the animals. Soil application of I compounds may increase herbage I levels for a period after application. However, plant uptake of applied I is poor and I may be leached quickly from soil.

If I antagonists are present (goitrogens, high feed Ca levels etc), soil application of I seldom if ever is effective in correcting I deficiency in stock and it is necessary to give I directly to the affected group.

In summary, application of iodine compounds to soil is not recommended to treat or control simple or induced I deficiency in animals.

Reduction of I-antagonists: If problems arise on goitrogenic feeds (Brassicas (cabbage, brussels sprouts, rape, kale, turnips), root tops etc, soyabean, groundnut, rapeseed, linseed and some clovers), reduce the allowance of those feeds. If I deficiency is induced by excessive use of slurry, sludge or inorganic fertilisers, reduce the application rates. If dietary Ca is too high, reduce it.

Stock on goitrogenic feeds, especially females in late pregnancy or in the breeding season, should get high levels of supplementary I (for example, 40-60 mg oral I/d to cows or 4-6 mg/d to ewes).

Summary: Grass-tetany is an acute, often fatal condition. Pending veterinary attention, it needs immediate first-aid therapy. Once tetany is confirmed, feed Mg supplements to all lactating comrades in the group and consider other preventative measures.

Warning: Do not give high-Mg cow feeds to calves, dry-stock or sheep. Do not give high-Mg ewe feeds to lambs. This may cause urinary stones and other problems. Cows may eat 112 g Calmag without side effects but 168 g or more can cause scouring, drop in milk yield and urinary stones.

Treatment: Treatment of Grass Tetany is based on restoring blood Mg and Ca to normal.

Ca and Mg injections: The usual way is by very slow intravenous injection of Ca compounds (such as 400-800 ml of 25% calcium borogluconate solution /cow) and subcutaneous injection of Mg compounds (such as 200 ml of 50% Mg sulphate solution, supplying 10 g Mg/cow). Doses for ewes are 10-12% (one 10th to one 8th) of cow doses. Fast i/v Ca can cause death from cardiac arrest. Even slow i/v Mg can do the same and many vets do not use Mg i/v.

Mg enemas: An enema of 60 g of Mg chloride (not oxide, sulphate or acetate) dissolved in 200 ml water is a quick, safe and simple therapy in affected cows. A simple polythene tube, with a rounded tip, is attached to a 200 ml squeeze-bottle. The tip is put gently 10 cm into the rectum; the solution is run in slowly. Keep the tail pressed tightly against the anus for 5 minutes afterwards, to prevent expulsion of the dose.

Supportive therapy may be needed (sedation to stop convulsions; stimulants in coma or depression; warmth and shelter to reduce cold-stress). General nursing (good feeding; turning of the recumbent cow etc) is critical, especially in cases of winter tetany. Oral Mg supplements are recommended at double the preventative rate (see below) to prevent relapse in affected cows for 2-3 days after treatment.

Mg supplements alone may fail to control an outbreak of winter tetany in cows. It is best to house all calved cows, to increase the feed supply AND to give Mg supplements.

Prevention: The main methods of preventing Mg deficiency, hypomagnesaemia and tetany are: to give extra Mg in the diet and to reduce risk factors associated with the disorder. Feed-grade calcined magnesite is the most common Mg supplement. It contains about 85% Mg oxide (MgO), which contains 60% Mg. Thus, calcined magnesite contains 60% of 85% = 51% Mg, range 49-53% Mg. Hereafter, it will be called Calmag.

Effective oral Mg supplements: The best way to ensure normal blood Mg levels is to feed Mg in the concentrate ration or to graze the animals on pasture dusted with Calmag. At pasture, if concentrate is not fed or dusting can not be used, Mg may be provided in a small amount of carrier, in the water, in blocks, or home-mixed with molasses. Note that free-access intake is not as reliable as fixed-rate feeding. Mg bullets are a last resort.

During the winter, it is easy to control Mg intake accurately by feeding it in loose minerals: a half or a third of the daily Mg allowance may be sprinkled over the easy-feed 2-3 times daily or sprayed as a slurry over bales of hay (see footnote 2). Cows in late pregnancy in herds with a history of hypocalcaemia, neonatal calf deaths or birth of weak calves may need oral Mg supplements (10-20 g Mg/cow/d). If fed at 100 g/cow/d, use pre-calver mineral mixes that contain about 15% Mg. Calved cows with high milk yields on silage or low-Mg feeds may need a supplement of 5-15 g Mg/cow/d (5-10% Mg in mineral mixes if fed at 125 g/cow/d post-calving).

 Grass tetany control: Mg absorption may be halved on tetany-prone pasture. Thus, double to treble the minimum Mg intake is needed to maintain Mg levels in blood. Lactating cows and ewes on tetany-prone pasture need a daily Mg supplement. Routine daily Mg supplements are recommended for lactating cows and ewes on rapidly growing spring or autumn pasture (60 g Calmag/cow/d; 10 g of Calmag/ewe/d).

The cheapest method is to give a daily oral Mg supplement of 20-50 g Mg (40-100 g Calmag) to cows and 3-5 g Mg (6-10 g Calmag) to ewes during the risk period. Protection starts 1-2 days after feeding begins and lasts for only 1-3 days after the last Mg dose.

During the tetany season, the feeding rate of mineral mix to cows is usually 130-150 g (say 150 g)/cow/d. At that rate, use a mix with 13-31% (say 21%) Mg (to provide a daily supplement of 20-40 g (say 32 g) Mg/cow/d). If fed at 25 g mix/ewe/d, use a high-Mg ewe mineral mix with 12-20% Mg (say 16%) to provide a daily supplement of 3-5 g Mg (say 4 g)/ewe/d, or with 10-17% Mg (say 13.3%) if 30 g of mix/ewe/ day is fed to supply the same amount of Mg.

Autumn tetany suckler cows at weaning: Weaning stress can cause tetany in suckler cows in the days after weaning, especially if the calves are kept near the cows. Oral Mg supplements for 4-6 days can prevent the problem but pasture dusting is not reliable in autumn.

Winter tetany in calved suckler cows: Nutritional and climatic stress on bare winter pastures can cause tetany in outwintered suckler cows with calves at foot. Oral Mg supplements alone may be ineffective in preventing the problem. See "Reducing the risk factors", below. Pasture dusting is not reliable in winter.

Mg in the concentrate ration: If concentrate rations are balanced properly, no other Mg supplement is needed while they are fed. Table 8 and Table 9 show various Mg target allowances for cows and ewes, and the Mg levels in cow and ewe concentrates needed to provide them at various levels of feeding. The tables show that, for any given concentrate ration, the adequacy of the Mg level in the ration can be assessed only if both target Mg allowance and the feeding rate are known. If high levels of fat (> 6%) are included in the concentrate, the Mg allowance should be increased further by 10 g/cow/d.

Mg in a small amount of carrier: The first column of Table 8 and Table 9 show the Mg level needed in a Mg carrier, to be fed at 0.5 kg and 100 g respectively to cows and ewes. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers).

Mg in a mineral mix: Table 1 shows mineral mix formulations for cows and ewes. Table 2 shows mineral mix formulations for drystock (cattle and lambs). See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Drenching sheep or cattle with Mg: Mg is poorly released from stores in bone. Thus, daily supplementation is needed. If Mg can not be supplied daily, the maximum safe interval between doses is 2 days. In that case, twice the daily dose (see previous section) is used. Intermittent dosing or feeding with Mg supplements at intervals greater than 2-3 days is of no real value and cows or ewes may die of tetany within 3 days of removal of Mg supplement during the risk period.

Pasture dusting with Calmag: Calmag is largely insoluble in water and is not suitable for the simpler systems of water medication. It is available in two forms, fine powder and granular. Only the powder form is suitable for pasture dusting. The dust adheres to the grass, even in rain. Grass cover must be at least 10 cm and dusting is best done after a shower or on dewy grass.

Enough paddocks can be dusted with 17 kg/ha to supply 1 week's grazing. The cows are kept on treated paddocks until the risk is over. Dusting requires a good quality fertilizer spreader. Dusting a few strips in a paddock is not enough as cows may choose undusted grass. Set-stocked systems need 34 kg/ha, repeated every 2 weeks. Dusting is economical at stocking rates of 2.2 cows or more/ha. It is too expensive at low stocking rates.

Pasture spraying: Soluble Mg compounds (sulphate, chloride, acetate) can be used in dry weather. See Part 1.b, above, for the general principles. However, as Mg supplements are needed daily or every second day, a few days of rain during the tetany season can cause an outbreak of tetany by washing off the salts from the grass. This method is potentially dangerous for tetany control.

If used, the application rate for cows is about 40 g Mg (400 g epsom salts or Mg chloride (10% Mg))/cow/d, applied daily (or 80 g Mg applied every second day) to the paddock.

Free access Mg supplements (see footnote 2): Home-mixed Calmag and molasses: The original way was to mix molasses and Calmag in equal parts by weight. Cows eat about 120 g/head/d of that, i.e. 60 g Calmag. The mix can be offered in tubs or half-barrels (one/20-25 cows): 20 kg molasses + 20 kg Calmag would supply 50 cows for 1 week. Stir the mix 1-2 times/d. Calmag settles out, especially if rain dilutes the mix. This allows pooling of molasses on top and the intake of Calmag falls. Train cows to the mix for 1 week before the risk period. This can be done by offering a 5: 1 molasses: Calmag mix at the start and gradually increasing the strength to 1: 1 over 5-7 days. Variants include molasses: Calmag: other cattle minerals in a ratio of 2: 1: 1, fed in tubs or molasses: Calmag in ratios of 3: 1 to 10: 1 fed in ball feeders.

Mg blocks and licks: For adequate prevention of tetany using ad libitum intake of blocks and licks, the farmer needs to know the Mg concentration in the product, the average intake of product/cow/d and the variation in intake between cows and between days. Products that contain too little Mg, or whose intake is small or very variable are not safe. The Mg intake (g/cow/d) can be calculated by multiplying the Mg level (g/100 g product) by the maker's figure for intake of product (g/cow/d). Products that supply much below 30 g Mg/cow/d are not to be recommended.

Oral Mg via the water supply to grazing cattle: Soluble Mg salts can be administered through the drinking water. The common soluble salts of Mg are the chloride, the sulphate (both hydrated, 10% Mg) and a dehydrated chloride (25% Mg). The acetate may also be available but may be more expensive. A few commercial companies market soluble Mg solutions.

Any of the soluble Mg salts can be added to the trough water in one of two ways: by a simple dispenser or by an expensive proportioner/pump device. Both ways require that streams, flood water, ponds etc are not available to the cows. Cows may refuse to drink medicated water if fresh water is available.

The simple dispenser is a 4-20 l plastic drum, with a special nozzle. The required amount of Mg salt is calculated as follows:

Herd allowance (g/d) = number of cows x 20 x 100 / Mg% in the salt.

Example: The dose of Mg sulphate (Epsom salts, 10% Mg) for a 50-cow herd is (50 x 20 x 100 / 10) = 10000 g (10 kg) per day. If the dehydrated chloride (25% Mg) is used, the amount would be (50 x 20 X 100 / 25) = 4000 g (4 kg) per day.

Half the dose is given in the morning and half in the afternoon. The Mg salt is dissolved in water in the dispenser, leaving 1/4 to 1/6 of an air-cap. The nozzle is attached and the dispenser is floated upside-down in the trough. Even on wet days, cows usually drink a minimum of 5-10 litres/head of water. To ensure that the trough is emptied by the cows at least once/d, take up dead-space (using concrete blocks or sand) so that the water capacity in the trough is about 5 l/cow (55 gal for 50-cow herd).

While 20 g Mg (as Mg sulphate)/cow/d is satisfactory, more than this causes scouring, drop in milk yield and other problems. If cows refuse to drink medicated water, dilute the trough with 1-2 times the volume of fresh water and skip the next half day's dose. Then continue as before. If they still refuse to drink, it may be necessary to reduce the dose rate but blood Mg can not be maintained in the normal range if the dose is much below 20 g Mg/cow/d.

Mg chloride solution (5% Mg) is available commercially (NutriBio Ltd, Cork and other companies). When added to the water supply at doses of 400-1000 ml/cow/d (20-50 g Mg/cow/d), the chloride solution was safe and palatable and caused no depression of water intake or scouring.

Veterinary products for Mg Supplementation: Mg bullets: The old Mg bullets for cows release 1 g Mg/bullet/d. If 4 bullets are given together, the daily Mg release (4 g) is only 13% of the amount in 60 g Calmag. The old Mg bullets have little effect on blood Mg levels and are not reliable in preventing tetany in cows.

A new Mg bullet (Optimag, Norbrook Laboratory) gives 3 g Mg/d. Two of the new bullets (IR4 each!) would give reasonable tetany-control in suckler cows on an outfarm, but other methods, giving 20-40 g Mg/cow/d are safer.There are also Mg bullets for ewes but they have the same problem as those for cows, i.e. the daily release of Mg from the bullets is very small compared with optimal supplement of 4 g Mg/ewe/d. They may be used as a last resort if other methods can not be used, for example in suckler cows in disadvantaged areas.

Subcutaneous injections of soluble Mg compounds, while of great benefit in treating hypomagnesaemia, useless as routine Mg supplements. They are very short-acting and would need to be repeated daily or every second day.

Soil fertilisation with Mg: If lime is needed, using magnesian limestone as a source of lime helps to raise herbage Mg levels. However, Mg fertilisation is no substitute for adequate feeding, shelter and Mg supplements on tetany-prone pastures.

Reducing the risk factors: This means reducing stress on the animals, providing adequate nutrition (especially dietary energy and fibre) and giving out-wintered cattle some supplementary feeding and shelter from severe weather. Reduced application rates of K and N fertilisers and autumn application of K (instead of spring application) can help if the hypomagnesaemia is associated with excessive use of those fertilisers. Na (salt) supplements can improve Mg absorption by cows if dietary Na is low.

If Mg supplements fail to control tetany in outwintered beef suckler cows, put the cows into a house or yard and feed a good winter diet. Diets of straw, poor hay or low-Mg silage may need Mg supplements. They may also need supplements of other minerals (salt, phosphorus, trace elements) and vitamins (especially vitamins A and E).

Summary: Simple Mn deficiency is very rare in cattle and sheep in Ireland. When it occurs, Mn deficiency is usually secondary, induced by high soil pH (alkaline). Over-liming can markedly decrease herbage Mn. Avoidance of over-liming can help to reduce the risk but oral Mn supplements are the best method of control. Mn sulphate (32.5% Mn) is a common Mn salt.

Effective oral Mn supplements: Mn can be given in the concentrate ration or forage, in a carrier or in mineral mixes. Oral Mn is usually cheaper and more reliable than Mn-fertilisation, as herbage Mn is more influenced by soil pH/lime status than by soil Mn level. See also Part 1.a, above.

Daily supplement: An oral supplement of 350-450 mg Mn/cow/d can be used to rectify or prevent Mn deficiency, under Irish conditions. American workers advise higher Mn supplementation (up to 980 mg Mn/cow/d) in herds with severe infertility due to Mn deficiency. A pro-rata dose for ewes would by up to 98 mg Mn/ewe/d. Table 4 shows the suggested optimum supplementation levels of Mn for other classes of stock.

Mn in the concentrate ration: If the concentrate ration is properly balanced, no other Mn supplement is needed while the ration is fed. See Table 6 for Mn levels in dairy concentrate to provide cows with 350-450 mg Mn/head/d. If weanling cattle (250 kg) need Mn supplement (150-188 mg Mn/head/d), and 1 kg concentrate is to be fed, it should contain 150-188 mg Mn/kg. If ewes need Mn supplement (33-42 mg Mn/head/d), and 0.8 kg concentrate is to be fed, it should contain 42-51 mg Mn/kg. If lambs need Mn supplement (11-14 mg Mn/head/d), and 0.4 kg concentrate is to be fed, it should contain 28-35 mg Mn/kg. See footnote 17 also.

Mn in a small amount of carrier: Table 7 shows carrier formulations for cows, ewes, cattle and lambs. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers). See footnote 17 also.

Mn in a mineral mix: Table 1 shows mineral mix formulations for cows and ewes. Table 2 shows mineral mix formulations for drystock (cattle and lambs). See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Drenching sheep or cattle with Mn: Periodic drenching with oral Mn sulphate may be effective if adequate doses are given often enough. A 14 to 21 day supply of Mn can be given in drenches every 2-3 weeks during the grazing season. A dose of 2.7 g Mn sulphate (882 mg Mn)/100 kg LW every 2 weeks or 4.1 g Mn sulphate (1323 mg Mn)/100 kg LW every 3 weeks is enough for cattle. A dose of 1.63 g Mn sulphate (532 mg Mn)/70 kg LW every 2 weeks or 2.46 g Mn sulphate (798 mg Mn)/70 kg LW every 3 weeks is enough for sheep. (For further details and warnings, see Part 1.f and Part 1.g, above. See footnote 17 also).

Pasture spraying with Mn sulphate: Foliar spraying of "hospital plots" with Mn sulphate in water every 14-21 days may be considered in Mn deficiency. The basic daily supplement is about 192.3 mg Mn sulphate/100 kg cattle LW or about 117 mg Mn sulphate/70 kg sheep LW. To allow for Mn falling to the ground, the basic amount of Mn is doubled. A suggested dose for foliar spraying every 14 days is 5.39 g Mn sulphate/100 kg cattle LW or 3.28 g Mn sulphate/70 kg sheep LW. (See Part 1.b, above, for details. See footnote 17 also).

Soil fertilisation with Mn: Mn application to soil is unreliable as a method of correcting Mn deficiency in animals. Oral supplements are better and cheaper.

Mn application to soil often is advised by commercial laboratories connected with the mineral/fertiliser industry. This practice has little value, as herbage Mn is more closely related to soil pH than to soil Mn levels.

Summary: Deficiency of P is rare on most well-run farms. The main methods of preventing P deficiency are to give P supplements, especially to lactating females on winter diets and to maintain adequate P levels in forage (grass and winter feed) by P fertilisation of the soil. Di-calcium phosphate (18% P) is a common P salt.

Warning: Do not give high-P feeds for cows or ewes to young calves or lambs, especially castrated males. This may cause urinary stones and other problems.

Effective oral P supplements: Large amounts of P are stored in the skeleton and can be mobilised in times of P shortage. Therefore, P supplements need not be given daily, as long as adequate amounts are given over any given period of days or weeks. The best way to ensure normal P status is to feed P in the concentrate ration or to graze the animals on pasture with a good P level. The cheapest method is to give a daily oral P supplement of 0-30 g P to cows and 0-3 g P to ewes, depending on P levels in the basic feed and on P requirements for late pregnancy, reproduction or milk yield.

Cows at pasture: Cows on well fertilised pasture or dry-stock (other than dry cows) on grass or silage diets seldom need P supplements. If P levels are low in pasture and if concentrate is not to be fed, P supplements can be given in a small amount of carrier or in palatable loose minerals, blocks or licks etc. Note that free-access intake is not as reliable as fixed-rate feeding in concentrate rations, in the forage or in carriers.

Cows in winter: It is easy to control P intake accurately by fixed rate feeding of loose minerals: a half or a third of the daily P allowance may be sprinkled over the easy-feed 2-3 times daily. See footnote 2.

The incidence of simple milk fever is seldom reduced by P supplements at practical rates given to cows in late pregnancy. Thus, a supplement of 0-10 g P/cow/d to dry cows is optional on good silage. Dry cows on very low-P feeds or those in herds with a history of hypocalcaemia, complicated by P shortage, may need larger P supplements (10-20 g P/cow/d) depending on the P intake. If fed at 100 g/cow/d, use a pre-calver mineral mix with about 0-15% P, depending on the degree of P shortage. P doses at calving: If P levels are low in the feed or in blood samples from cows with milk fever, use di-calcium phosphate (22% Ca, 18% P) instead of limestone just before and after calving at 180 g/dose. See Hypocalcaemia.

Excellent grass silage often has suboptimal P levels (0.38-0.28% DM) for high milk yields. Thus, calved cows with high milk yields on silage with suboptimal P levels need moderate P supplements (5-15 g P/cow/ day, or 4-12% P in mineral mixes fed at 125 g/cow/d post-calving). On low-P feeds (those with P levels of 0.28-0.18% DM) such as beet pulp, fodder-beet, roots, straw, stemmy hay and low-P silages etc, high yielders need a large P supplement (15-25 g P/cow/d, or 12-20% P in mineral mixes fed at 125 g/cow/d post-calving). Occasionally even larger P doses are needed, in which case the amount of mineral mix needed to carry the P supplement may increase to 140-200 g/cow/d.

P in the concentrate ration: If the concentrate ration is properly balanced, no other P supplement is needed while ration is fed. P levels of the order of 0.55-0.65% are advisable in dairy concentrates fed at 7 kg/cow to high yielders.

P in a small amount of carrier: To supply 5-20 g P/d to cows in 0.5 kg carrier, the carrier would need 1-4% P. To supply 0.5-2 g P/d to ewes in 100 g carrier, the carrier would need 0.5-2.0% P. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers).

P in a mineral mix: See examples in the last few paragraphs above. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Drenching sheep or cattle with P: This method is not used with major elements, as other methods are easier and better.

Pasture dusting and spraying with P compounds: This method is not used, as other methods are easier and better.

Home-mixed phosphates and molasses: Molasses and phosphate supplement (di-calcium phosphate (18% P) or monoammonium phosphate (24% P)) can be mixed in equal parts by weight: 20 kg molasses + 20 kg phosphate supplement would supply 50 cows for 1 week. The mix can be offered in tubs or half-barrels, (one/20-25 cows). The mix needs to be stirred 1-2 times/d. Phosphate settles out, especially if rain dilutes the mix. This allows pooling of molasses on top and the intake of phosphate falls. Mean intake of mix/cow/d should be restricted to about 120 g, i.e. 60 g of P supplement (11-14 g P/cow/d, depending on whether di-calcium or monoammonium phosphate is used).

P blocks and licks: For adequate prevention of P deficiency using ad libitum intake of blocks and licks, the farmer needs to know the P concentration in the product, the average intake of product/cow/d and the variation in intake between cows and between days. Products that contain too little P, or whose intake is small or very variable are not safe. The P intake (g/cow/d) can be calculated by multiplying the P level (g/100 g product) by the maker's figure for intake of product (g/cow/d). Products that supply much below 20 g P/cow/d are not to be recommended in serious P deficiency.

Oral P via the water supply to grazing cattle: Soluble P supplements to medicate water have been sold commercially. To be of use in P deficiency in dairy cows, they must supply large doses of P (5-30 g/cow/d) in soluble form and they must not make the water unpalatable. Most fail on both counts. Other ways of giving P supplements are cheaper and more practical.

Veterinary products for P Supplementation: P injections: Injection of soluble salts of P are useful in emergency treatment of P deficiency and allied metabolic disorders. However, they are cleared quickly from the body. They have little or no long-term effect on P status and are not practical as a method of routine P supplementation.

Soil fertilisation with P: Adequate application of P fertiliser usually prevents P deficiency in herbage. Depending on the soil P results and the soil type, Teagasc advisers can recommend appropriate application rates.

Reducing risk factors: Ca, P and vitamin D are closely related. Excess Ca can deplete P in the body. The ideal Ca/P ratio in total feed for dairy cows is 1.4/1 but ratios in the range 1/1 to 3/1 are acceptable and wider ratios can be tolerated without adverse effect for a few weeks. Vitamin D deficiency can interfere with Ca and P metabolism. Vitamin D supplements are advisable for all stock in winter or in stock confined to dark or shaded places, such as the north side of wooded mountains.

Summary: Dietary Se requirements of cattle are high in Ireland and the oral Se dose needed to control diagnosed Se deficiency is greater than is the case in the U.K. Na selenite (30% Se in the hydrated form; 45% Se in the anhydrous form) is a common Se salt.

Warning: Se toxicity occurs in a few counties (see next section). Near known Se toxic farms, give high-Se supplements only on veterinary advice, or if deficiency has been confirmed on blood Se test. Outside of from those areas, the risk of poisoning is small. There is a 5-fold gap between the upper safe level of Se in feed (0.6 mg/kg DM) and the level at which Se toxicity may occur in stock (usually >3 mg/kg DM). Because of the widespread occurrence of Se deficiency (with and without loss of animal productivity), there is a strong case for including 3-5 mg Se/cow in the daily allowance of commercial mineral supplements or compound rations.

Effective oral Se supplements: Se can be given in the concentrate ration or forage, in a carrier or in mineral mixes. Oral Se is usually cheaper and more reliable than Se-fertilisation. See also Part 1.a, above.

Daily supplement: An oral supplement of 3-5 mg Se/cow/d can be used to rectify or prevent Se deficiency, under Irish conditions. A supplement of 2.5-3.5 mg/cow/d may suffice in mild deficiency but 3.5-5.0 mg/cow/d may be needed in severe deficiency. Table 4 shows the suggested optimum supplementation levels of Se for other classes of stock.

Se in the concentrate ration: If the concentrate ration is properly balanced, no other Se supplement is needed while ration is fed. See Table 6 for Se levels in dairy concentrate to provide cows with 3-5 mg Se/head/d. If weanling cattle (250 kg) need Se supplement (1.4-2.3 mg Se/head/d), and 1 kg concentrate is to be fed, it should contain 1.4-2.3 mg Se/kg. If ewes need Se supplement (0.3-0.5 mg Se/head/d), and 0.8 kg concentrate is to be fed, it should contain 0.38-0.63 mg Se/kg. If lambs need Se supplement (0.10-0.17 mg Se/head/d), and 0.4 kg concentrate is to be fed, it should contain 0.25-0.43 mg Se/kg.

Se in a small amount of carrier: Table 7 shows carrier formulations for cows, ewes, cattle and lambs. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers).

Se in a mineral mix: Table 1 shows mineral mix formulations for cows and ewes. Table 2 shows mineral mix formulations for drystock (cattle and lambs). See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Drenching sheep or cattle with Se: Periodic drenching with oral Na selenite (30% Se) may be considered if adequate doses are given often enough. A 14-21 day supply of Se can be given in drenches every 2-3 weeks during the grazing season. A dose of 37.2 mg Na selenite (11.67 mg Se)/100 kg LW every 2 weeks or 58.3 mg Na selenite (17.5 mg Se)/100 kg LW every 3 weeks is enough for cattle. A dose of 23.3 mg Na selenite (7 mg Se)/70 kg LW every 2 weeks or 35.0 mg Na selenite (10.5 mg Se)/70 kg LW every 3 weeks is enough for sheep. (For further details and warnings, see Part 1.f and Part 1.g, above).

Pasture spraying with Se salts: Foliar spraying of "hospital plots" with Na selenite (30% Se) in water every 14-21 days may be considered in Se deficiency. The basic daily supplement is about 2.78 mg Na selenite/100 kg cattle LW or about 1.67 mg Na selenite/70 kg sheep LW. To allow for Se falling to the ground, the basic amount of Se is doubled. A suggested dose for foliar spraying every 14 days is 77.9 mg Na selenite/100 kg cattle LW or 46.76 mg Na selenite/70 kg sheep LW. (See Part 1.b, above, for details).

Oral Se via the water supply to grazing cattle: Se can be given in chelated form in the water supply to grazing cattle (see Part 1.c, above). The daily Se supplement for cattle is shown in Table 4.

Veterinary Se supplements include injections and bullets containing Se compounds. For general discussion of timing of administration of Se compounds, see Mineral Storage in the Body and Timing of Administration of Supplements.

Se treatment of calves: In herds that have a high incidence of still-birth or weak calf syndrome due to Se deficiency, give a Se supplement to any cows due to calve. Calves born alive in such herds may also benefit from a Se supplement within 1 week of birth. Injection of Na selenite plus vitamin E is recommended at birth, or within a few days of birth. If Na selenite injection is used, repeat it after 4-5 weeks, or give alternative Se supplements to the calves.

Se treatment of lambs: In flocks that have a high incidence of still-birth or weak lamb syndrome due to Se deficiency, give a Se supplement to any ewes due to lamb. Lambs born alive in such flocks may also benefit from a Se supplement within 1 week of birth. Injection of Na selenite plus vitamin E is recommended at birth, or within a few days of birth. If Na selenite injection is used, repeat it after 4-5 weeks, or give alternative Se supplements to the lambs. Lambs in Se-deficient flocks may show illthrift pre-weaning or post-weaning. In such flocks, treatment of the dam in late pregnancy and of the lambs from 1 month of age may be needed.

Dosage and frequency of administration of Se compounds depends on the liveweight (LW) of the animals and on the degree of challenge to Se status. Heavier animals need larger doses. Larger or more frequent doses are needed in groups exposed to high challenge, such as in severely deficient herds. (See footnote 10).

Se injections: There are three main Se compounds for injection: barium selenate ("Deposel" long-acting depot injection) and Na selenite or Na selenate (both short-acting). Deposel is under review. All products are given subcutaneously. Intramuscular injections are not recommended, as they may damage meat. In contrast to Cu injections, Se injections may be given close to mating, without risk of reducing conception rates.

"Deposel" (Rycovet, Glasgow) is a depot Se injection, using poorly soluble barium selenate. This can maintain normal Se status for 12-16 months after s/c injection of 100 mg Se/100 kg LW. The product is expensive but multiple injections of soluble Se salts would be almost as expensive. Ba selenate injections are under review, as blood GPx tests in 1991 gave evidence of disappointing results in cows treated with the product.

Na selenite or selenate: Soluble Se salts (Na selenate or Na selenite) may be injected s/c in doses up to 10 mg Se/100 kg LW. They give protection for only 4-6 weeks and repeated injections are needed in severe Se deficiency in which prolonged protection may be needed, as in a combination of abortion, stillbirth, placental retention and repeat breeding in a herd due to Se deficiency. Soluble Se salts are cheaper than insoluble salts (see Deposel) but are short-acting. They give protection for only 3-5 weeks after each injection.

Se bullets: Glass bullets that supply Se are available (Cosecure: Cooper Pitman-Moore, Alltrace: Agrimin and Ionox: Bayer). The bullets are given orally by a special bulleting gun. The special glass matrix of the first two is slowly soluble in the reticulo-rumen and releases its supplement over a period of about 6-10 months. The Ionox matrix is insoluble, but releases its Se supplement over a period of up to 8 months.

"Alltrace" bullets each contain 245 mg Se. The daily release from 4 Alltrace bullets (4 mg Se/d) would be adequate for cows and adult cattle under Irish conditions.

"Cosecure" cattle bullets each contain 300 mg Se. Two bullets to calves (108 kg LW) gave satisfactory Se levels in cattle on an Irish low-Se farm for at least 6 months. The daily release (3.3 or 6.6 mg Se/d) from 2 or 4 Cosecure bullets per year would satisfy Se requirements of stores or adult cattle respectively under Irish conditions.

"Ionox cattle boluses" (Bayer Ireland) each contain 500 mg Se. Mean release would be 2.6 mg Se/bolus/d. This should be adequate for yearling cattle on pastures that pose a risk of severe deficiency of Se. If no other Se supplements were given, adult cows would need 2 boluses every 6-8 months on similar high-risk pastures.

Other Se bullets or pellets have been successful in Australia and New Zealand but we are unaware of their use or availability in Ireland.

Soil fertilisation with Se: The method is useful but take care to apply the correct amount of Se compounds. See Part 1.e, above.

Pasture management to raise herbage Se levels: Avoid excessive application of sulphur fertilisers, as they may reduce herbage Se levels. Normal application rates, which may be needed in sulphur-deficient areas, depress herbage Se only slightly. Apart from soil fertilisation with Se, there is little one can do to raise herbage levels of Se.

Identify the problem fields: Intensive sampling of herbage for Se analysis can be used to identify the most dangerous parts of the farm. If these are very localised, as is often the case, consider fencing them off and excluding them permanently from use for grazing/cutting. NOTE: Se-deficient fields may occur within 1 km of Se-toxic fields.

Graze the less dangerous fields: Where possible, use the more dangerous seleniferous fields for conservation for hay or silage. Before feeding, dilute silage or hay from the toxic fields with material from safer areas.

Use S fertilisers at high rates: Soil application of S-containing materials e.g. sulphate of ammonia or gypsum, can reduce the levels of Se in herbage. Sulphate of ammonia probably acts in three ways: dilution effect from increased grass growth; sulphate/selenate antagonism and ammonium/selenate antagonism. Under experimental conditions, sulphate of ammonia (1 tonne/ac) reduced herbage Se from 10 to 1.4 mg/kg DM and gypsum (12 tonnes/ac) reduced herbage Se from 18 to 2 mg/kg DM. While these are heavy application rates, they are not much higher than those used for very intensive grazing.

Limit grazing on toxic fields: In the absence of herbage Se reduction by S fertilisation, if stock must graze known Se-toxic fields, do not allow them to graze the toxic area for more than 2 weeks in any 6 week period.

Remove stock if signs occur: At the first sign of clinical toxicity on known problem farms, remove all stock from the problem fields. An oral sulphate antidote can be tried for 21-50 days, or until clinical signs disappear. Contact Grange for details, if needed.

Reduce Se intake: Should signs of toxicity arise on winter-feed, remove the stock from the toxic feed, or use safe feed to dilute the toxic feed. The oral sulphate antidote can be tried.

Use low-Se mineral supplements: On Se toxic farms, use only low-Se mineral supplements or concentrate rations, for example those supplying 0-2 mg Se/cow/d. Oral Se poisoning in cattle seldom occurs at intakes below 45 mg Se/cow/d over many weeks. Routine supplementation with 3-5 (preferably 5) mg Se/cow/d is advised in Se deficiency.

Blood-test suspect Se-deficient stock within 5 miles of Se-toxic farm: In Counties Carlow, Limerick and Meath, Se-deficient areas were identified within short distances of Se-toxic or Se-subtoxic areas. However, for safety, avoid feeding high levels of Se in supplements or concentrate rations to herds within 5 miles of known Se-toxic farms, unless clinical signs and blood (or herbage) tests confirm Se deficiency in those herds.

Avoid land-spreading of drainage spoil if there is any suspicion that the spoil may contain high Se levels.

Sheep are less susceptible than cattle or horses: Horses are more susceptible than cattle, which are more susceptible than sheep. Graze sheep or cattle in preference to horses in potentially toxic areas.

Summary: Many silages and some herbages are low in Na, especially for lactating animals. The K/Na ratio in feed may exceed optimal values of 20/1 if Na is low, or if K is high. Na shortage may also restrict Mg absorption by cows, thereby increasing tetany risk.

The main methods of preventing Na shortage are to give Na supplements and to avoid excessive K intakes, especially by lactating females. Apart from lambs and young calves on high-concentrate diets, drystock rarely need extra salt, but salt is often used as a cheap carrier for trace elements. Na chloride (common salt, 39% Na) is the most common Na salt.

Avoidance of excessive use of K fertiliser helps to maintain more normal K/Na ratios in forage, especially on spring herbage, when lactation is maximal. Na fertilisation of the soil with Kainit (22% Na) at 0.5 tonnes/ha may increase herbage Na levels.

Effective oral Na supplements: Large amounts of Na are stored in plasma and body fluids and are recycled very efficiently via saliva into the digestive tract for reabsorption. This recycling is useful in times of Na shortage. Thus, Na supplements need not be given daily, as long as adequate amounts are given over any given period of days or weeks.

Na allowances depend on Na levels in the basic feed and on Na requirement for late pregnancy, reproduction or milk yield. Animals with unrestricted access to clean water can handle large excesses of salt without difficulty.

The best way to ensure normal Na status is to feed Na in the concentrate ration or to graze the animals on pasture with a good Na level. The cheapest method is to give an oral Na supplement: 6-23 g Na/cow/d (supplied by 15-59 g salt) are advisable to calved cows, especially in high-yielding herds, on silage or herbage with suboptimal Na levels. If water supply is unrestricted, cows can handle up to 109 g Na (280 g salt) or more/d without problems. Ewes may get 1.0-2.3 g Na (2.6-5.9 g salt)/head/d but they can handle up to 10 g Na (26 g salt) or more/d without problems.

Cows at pasture: If concentrate containing Na is not to be fed, Na supplements can be given in a small amount of carrier or in palatable loose minerals, blocks or licks etc. Note that free-access intake is not as reliable as fixed-rate feeding infoncentrate rations, in forage or in carriers.

Cows in winter: It is easy to control Na intake accurately by fixed rate feeding of loose minerals: a half or a third of the daily Na allowance may be sprinkled over the easy-feed 2-3 times daily (see footnote 2). A supplement of 7.5 g Na (19 g salt)/cow/d to dry cows is optional on silage but higher levels may be fed as a carrier for trace elements. Dry cows on very low-Na feeds may need Na supplements (10-15 g Na (26-38 g salt/cow/d) depending on the Na intake. Pre-calver mineral mixes, if fed at 100 g/cow/d, usually contain 5-18% Na, mainly as a cheap carrier for trace elements and vitamins.

Excellent silage often has suboptimal Na levels (sometimes as low as 0.07% DM) for high milk yields. Thus, calved cows with high milk yields on silage with suboptimal Na levels need moderate Na supplements (12 g Na/cow/d, or 9-10% Na in mineral mixes fed at 125 g/cow/d post-calving). In practice, many herds get more Na supplement than this and the Na content of mineral mixes fed post-calving may range from 7-20%

Na in the concentrate ration: If the concentrate ration is properly balanced, no other Na supplement is needed while ration is fed. Na levels of the order of 0.40-0.50% are advisable in dairy concentrates fed at 7 kg/cow to high yielders.

Ensure that high-concentrate diets for lambs and young calves contain 1-2% salt to reduce the risk of formation of urinary stones.

Na in a small amount of carrier: To supply 8-16 g Na/d to cows in 0.5 kg carrier, the carrier would need 1.6-3.2% Na. To supply 1.0-2.3 g Na/d to ewes in 100 g carrier, the carrier would need 1.0-2.3% Na. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers).

Na in a mineral mix: See examples in the last few paragraphs above. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Free access Na supplements: Although Na-deficient animals can usually find salt, free access systems are not as reliable as fixed rate feeding systems. See footnote 2.

Na blocks and licks: For adequate prevention of Na deficiency using ad libitum intake of blocks and licks, the farmer needs to know the Na concentration in the product, the average intake of product/cow/d and the variation in intake between cows and between days. Products that contain too little Na, or whose intake is small or very variable are not safe. The Na intake (g/cow/d) can be calculated by multiplying the Na level (g/100 g product) by the maker's figure for intake of product (g/cow/d). Products that supply much below 12 g Na/cow/d are not to be recommended in serious Na deficiency.

Drenching sheep or cattle with Na: This method is not used, as other methods are easier and better.

Pasture spraying with Na salts: This method is not used, as other methods are easier and better.

Oral Na via the water supply to grazing cattle: Salt inclusion in mineral mixes, in concentrate rations or in the forage etc is the usual method used. While salt can be given in the water supply, this is seldom used. Cattle and sheep may refuse to drink water with high salt content. Also, salt water may cause salt poisoning if drunk to excess.

Veterinary products for Na Supplementation: Apart from the treatment of severe dehydration, such as in scouring, veterinary treatment of salt deficiency is seldom needed in Ireland. In acute urgent cases, oral or injectable electrolyte solutions, such as saline, glucose saline etc are available. These agents have no practical use as routine Na supplements.

Soil fertilisation with Na: Annual application of 0.5 tonnes/ha (4 bags/ac) of KAINIT (22% Na) to the soil can raise herbage Na content. Satisfactory levels (above 0.15% DM) can be maintained for one grazing season.

Summary: Zn deficiency can be simple (low levels in soil and feed) or induced by high feed Ca levels, which block Zn absorption from the gut. Primary deficiency of Zn is rare in ruminants. Secondary deficiency, due to excess dietary Ca, can occur. Oral Zn is the main method of correction. Zn sulphate (22.7% Zn) is a common Zn salt.

To reduce the risk of secondary deficiency, use Zn supplements at the high level (see Table 4) in cattle diets high in Ca. Avoid excessive Ca intakes. Genetically induced Zn deficiency may be more difficult to correct and it may need much more Zn supplement to prevent it. Culling of the gene carriers helps to eliminate it.

Effective oral Zn supplements: Zn can be given in the concentrate ration or forage, in a carrier or in mineral mixes. See also Part 1.a, above.

Daily supplement: An oral supplement of 375-750 mg Zn/cow/d can be used to rectify or prevent Zn deficiency. A supplement of 375-562 mg/cow/d may suffice in mild deficiency but 562-750 mg/cow/d may be needed in severe deficiency (3.3 g Zn sulphate (22.7% Zn) supplies 750 mg Zn). Table 4 shows the suggested optimum supplementation levels of Zn for other classes of stock.

Zn in the concentrate ration: If the concentrate ration is properly balanced, no other Zn supplement is needed while ration is fed. See Table 6 for Zn levels in dairy concentrate to provide cows with 375-750 mg Zn/head/ day. If weanling cattle (250 kg) need Zn supplement (150-341 mg Zn/ head/d), and 1 kg concentrate is to be fed, it should contain 150-341 mg Zn/kg. If ewes need Zn supplement (33-75 mg Zn/head/d), and 0.8 kg concentrate is to be fed, it should contain 41-94 mg Zn/kg. If lambs need Zn supplement (11-25 mg Zn/head/d), and 0.4 kg concentrate is to be fed, it should contain 28-63 mg Zn/kg.

Zn in a small amount of carrier: Table 7 shows carrier formulations for cows, ewes, cattle and lambs. See Methods of Mineral Supplementation of stock (on feeding of mineral mixes and carriers).

Zn in a mineral mix: Table 1 shows mineral mix formulations for cows and ewes. Table 2 shows mineral mix formulations for drystock (cattle and lambs). See Methods of Mineral Supplementation of stock (on feeding of mineral mixes).

Drenching sheep or cattle with Zn: Periodic drenching with oral Zn sulphate (22.7% Zn) is effective if adequate doses are given often enough. A 14 to 21 day supply of Zn can be given in drenches every 2-3 weeks during the grazing season. A dose of 5.31 g Zn sulphate (1205 mg Zn)/100 kg LW every 2 weeks or 7.96 g Zn sulphate (1808 mg Zn)/100 kg LW every 3 weeks is enough for cattle. A dose of 3.33 g Zn sulphate (756 mg Zn)/70 kg LW every 2 weeks or 5.0 g Zn sulphate (1134 mg Zn)/70 kg LW every 3 weeks is enough for sheep. (For further details and warnings, see Part 1.f and Part 1.g, above).

Pasture spraying with Zn salts: Foliar spraying of "hospital plots" with Zn sulphate in water every 14-21 days may be considered in simple Zn deficiency and in Ca-induced Zn deficiency. The basic daily supplement is about 411.7 mg Zn sulphate/100 kg cattle LW or about 247 mg Zn sulphate/70 kg sheep LW. To allow for Zn falling to the ground, the basic amount of Zn is doubled. A suggested dose for foliar spraying every 14 days is 11.5 g Zn sulphate/100 kg cattle LW or 6.92 g Zn sulphate/70 kg sheep LW. (See Part 1.b, above, for details).

Oral Zn via the water supply to grazing cattle: This method is used elsewhere but not in Ireland.

Veterinary products for Zn Supplementation: Zn injections: Intramuscular depot injections of Zn oxide or Zn dust in olive oil have been used to treat Zn deficiency in sheep abroad but we are unaware of their use in Ireland. The dose was 200 mg Zn for adult sheep and 50 mg Zn for lambs.

Zn pellets: Oral Zn bullets or pellets have been used to treat Zn deficiency in sheep abroad. They were effective for only 7 weeks and are unsuitable for long-term control. We are unaware of their use in Ireland.

Multiple trace element bullets: Some commercial bullets, such as "Alltrace" (Agrimin) contain Zn, but daily release of Zn is at levels far below those recommended as a suitable Zn supplement. A large total daily release of Zn (as large as in Table 4), is needed for maximum effect. Most bullets can not attain that degree of Zn release.

Soil fertilisation with Zn: Zn application to soil is unreliable as a method of correcting Zn deficiency in animals. Oral supplements are better and cheaper.

Table 1. Examples of mineral mix formulations for cows and ewes. The allowance of mix gives a daily trace element supplement, as in Table 4.

** Some authorities double these amounts of Mn for breeding females, especially in groups with severe infertility and suspected Mn deficiency

*** The maximum Se supplement was reduced to 5 mg Se/cow/d, as from January 1 1996. Do not feed high Se minerals to cattle within 5 miles of a known Se-toxic farm unless blood test indicates no risk of Se toxicity.

**** These Vit E levels are 4-6 times higher than usual (underlined values are more usual). Research in USA and elsewhere shows that high levels of Vit E improve immunity and reduce mastitis incidence.

* Mineral Levels in top quality sheep minerals are shown in brackets (). If recommended daily allowances are above or below those shown, the trace element and vitamin levels should be adjusted down or up, accordingly. Never feed ewe minerals to lambs.

** Recommended Se allowances were reduced on 2/1/1996.

*** Do not give Cu to sheep in drenches, mineral mixes, licks etc, except on veterinary advice, following diagnosis of Cu deficiency in the flock by blood test and/or on clinical/post-mortem findings.

**** National Advisory bodies vary widely in their suggested vitamin allowances for sheep. The Vit A and D3 levels suggested here are approximate only. The lower Vit E levels are more usual. The higher levels are suggested in line with research in cows that showed that high Vit E inputs enhanced immunity to infection (especially mastitis).

Table 2. Examples of mineral mix formulations for cattle (drystock) and sheep (lambs). The daily allowance of mix gives a daily trace element supplement, as in Table 4. Values in brackets represent the top specifications.

* If recommended daily allowances are above or below those shown, the trace element and vitamin levels should be adjusted down or up, accordingly. Never feed cow minerals to calves, ewe minerals to lambs, or cattle minerals to sheep.

** To prevent urinary stones in lambs/rams, feed 0-2% (low) levels of Mg in mineral mixes.

*** Do not give Cu to sheep in drenches, mineral mixes, licks etc, except on veterinary advice, following diagnosis of Cu deficiency in the flock by blood test and/or on clinical/post-mortem findings.

$ National Advisory bodies vary widely in their suggested vitamin allowances for sheep. The Vit A and D3 levels suggested here are approximate only. The lower Vit E levels are more usual. The higher levels are suggested in line with research in cows that showed that high Vit E inputs enhanced immunity to infection (especially mastitis).

(*) The optimal Ca and Mg supplements for Dry Cows on silage or grass are 0 and 15 g/cow/d, respectively.

(**) The higher Mg supplements (20-50 g/d for calved cows and 3-5 g/d for lambed ewes) are for use in the tetany seasons. Otherwise a Mg supplement of 5-10 g/d for cows and 1-2 g/d for ewes is enough in lactation.

The lower levels are for routine continuous use. With the following exceptions, the higher levels are advised for national use in the Teagasc 5-month mineral programme for cows (1 month prepartum to 5 months postpartum; see Addendum), or as needed in groups of cattle or sheep at risk of severe deficiency:

Trace element levels (mg/kg) needed in compound dairy concentrate to supply the targets in Table 4, if the daily allowance of concentrate (kg/cow/d) is:

(**) Some authorities double these amounts of Mn for breeding females, especially in groups with severe infertility and suspected Mn deficiency

Rates in the lower half of the scale may suffice for continuous use in mild deficiency but rates in the upper half of the scale are needed in severe deficiency, or in the 5-month Teagasc mineral programme for cows. (See Addendum, and the notes under Table 4, above). For example, in Co. Cork, most Cu deficiency in cows is simple deficiency, with little Mo in the herbage: in such cases, a supplement of 150-300 mg Cu/cow/d may suffice to maintain normal Cu status. However, on reclaimed cut-over peat-land farms, such as in Co. Kildare, Mo-induced Cu deficiency may be severe in cows: in such cases, 300-450 mg Cu/cow/d may be needed continuously. Where cows are fed on herbage or silage + concentrate, the I supplement can be 20-40 mg/cow/d but up to 60 mg I/cow/d is advisable if goitrogenic feeds are used.

Table 7. Trace element levels in carriers to provide animals with optimum daily oral supplements (as in Table 4), assuming that each animal eats the same amount of carrier (g/d), as below:

 (*) Do not give Cu (copper) to sheep in a carrier ration except on the advice of a veterinary surgeon, following diagnosis of Cu deficiency in the flock by blood test and/or on clinical/post-mortem findings.

(***) If the daily ration has > 6% fat, it is advisable to increase Mg allowance further by about 10 g/cow/d in the concentrates.

The following abbreviations are used throughout the text:

Few wholesalers sell direct to farmers as low volume retail sales are troublesome and pure salts of trace elements, if used incorrectly, are toxic to people and animals.

However, the common salts of trace elements are available from some sources, especially in multiples of 25 kg. Sources include:

 Acknowledgements: Technical data does not come out of thin air. The information on which this manual is based came from many sources: research by many other colleagues in the Agricultural Institute (now part of Teagasc) and published research in the international scientific journals, adapted for Irish conditions.

We thank Drs. Garry Fleming, Willie Murphy (Johnstown Castle) and David Poole (Grange), whose research on mineral problems spanned more than 30 years and laid the main foundation for our advice.

We thank our colleagues Kevin O'Farrell, John Mee and John Murphy (Moorepark), Padraig O'Kiely, Michael Drennan and William Enright (Grange) for their additions to the manuscript and all our other Teagasc colleagues (research, advisory, technical and clerical), on whose help we rely daily.

We thank the farmers and their veterinary surgeons in practice and in the Regional Veterinary Laboratories who use Teagasc services. They let us know whether or not the advice that we give is effective in solving their problems.

We thank the representatives of the commercial companies (veterinary pharmaceuticals, feed compounders, mineral compounders, fertiliser compounders etc) who have funded Teagasc research into mineral problems.

We thank Michael Miley and the staff in Teagasc Headquarters for their editorial help and for changing the format of a highly technical text to make it readable by general users.

Finally, we salute the memory of Drs. Tom Walshe and Larry O'Moore, the two great Irish pioneers on mineral disorders in cattle and sheep.

Addendum: My coauthor, Dr. Tom Gately died in 1996; may he Rest in Peace.

1. A routine 150-day supplementation programme, which controls the main mineral-related problems in beef and dairy cows and in their young calves, is described. It supplies optimum allowances of major + trace minerals to cows from 30 days pre- to 120 days post- calving. The carry-over effect of the 150-day programme may fail to control mineral-related problems in cows outside of that period, such as problems at 3-7 months of pregnancy (foetal mummification, abortion; illthrift, low milk yield, scour or grass tetany in late summer or autumn). In that case, the cows may need additional supplements at that time. Also, pre-calver minerals may fail to prevent some mineral-related problems in older calves (calf tetany; Cu, Co, Se or I deficiency after 6 weeks of age etc). In those conditions, the calves may need direct supplementation at that time.

   The programme is based on oral supplements of three different mineral-vitamin mixes. These are: a Pre-Calver Mineral (100 g/cow/d for 30 days) + a Post-Calver Mineral (125 g/cow/d for 80 days) + a Tetany-Control Mineral (140 g/cow/d for 40 days). The total cost is IR 5.43-9.30/cow, or an average of 3.6-6.2 p/cow/d. If 0.5-1.0 kg molassed rolled barley or beetpulp, is used in the tetany period the cost would be about 6.5-16.0 pence/cow/d extra, or IR 2.60-6.40 for 40 days. In that case, the total cost of the 150-day programme would be IR 8.03-15.70/cow, or an average of 5.4-10.5 p/cow/d.

2. A similar 150-day supplementation programme, providing oral supplements of trace element sources alone in 5-8 g/cow/d of trace element compounds costs IR 0.80-1.27/cow (about one seventh of the cost of good mineral-vitamin mixes).
3. For comparative purposes, other 150-day mineral supplementation programmes, based on veterinary products and other methods, are costed also. Good veterinary products (bullets, boluses, injections etc) rapidly treat clinical or subclinical deficiencies in cows. But a routine preventative programme based on veterinary products (at correct doses and frequency for Irish conditions) costs more than routine use of good mineral-vitamin mixes or oral trace element supplements.

The main effects of mineral related problems in spring-calving dairy and beef suckler herds involve the cows and their young calves. The carry-over

(a) Effects in cows include milk fever/slow calving/retained placenta, low immunity (increasing the risk of mastitis/ mastitis), grass tetany and infertility (anoestrus, suboestrus, repeat breeders and early embryonic death). High-yielding dairy cows on grass silage usually need a supplement of Ca, P, Mg and Na to maintain optimum silage intake and milk yield.

(b) Effects in young calves include late abortion, stillbirth, soft/weak calves, early postnatal death, low immunity (increasing the risk of pneumonia, septicaemia, calf scours).

Therefore, in spring-calving cows, the need for mineral supplements is greatest over a 5-month period from 1 month pre- to 4 months post- calving. Adequate supplies of major and/or trace elements during those 5 months can prevent or reduce the incidence of mineral-related effects, as discussed above. Se and I supplements are needed before 1 month of age by calves from Se- or I-deficient dairy or beef cows. Mg supplements are needed by dairy calves fed milk or milk substitute alone. Suckler calves in herds with a history of calf tetany need Mg bullets, the only practical Mg supplement in that case. Cu supplements (injection, CuO bolus) by 1-3 months of age may be needed by suckler calves from Cu-deficient dams to prevent illthrift by 3-4 months of age. (Calves, fed concentrates and weaned onto grass, seldom need Cu supplements before 6-9 months of age).

To compare the costs of some common methods of supplementation, we assume a 5-month (150-day) supplementation programme. Additional periods of mineral supplementation are needed if other mineral-related problems, such as foetal mummification, early abortion, scour, tetany etc arise due to severe deficiency in late summer/autumn.

To help farmers to assess the relative cost of various supplements, retail prices of IR 250-500/tonne are used for Pre-Calver Minerals, Post-Calver Minerals and Tetany Control Minerals. Top quality Irish-manufactured mineral-vitamin mixes can be bought for IR 260-470/tonne. In contrast, some poorly formulated mineral mixes and blocks are being imported from abroad at prices between IR 550-1000/tonne. Some suppliers claim that "protected" trace elements (organic, complexed or chelated forms) improve animal health or performance more than inorganic trace-elements. There is little published scientific evidence to support that claim. The cost of "protected" trace-elements can be 5-20 times the cost of common inorganic trace-elements.

If farmers are offered mineral mixes at prices above IR 470/tonne, they may wish to consult with their Teagasc adviser to locate an alternative supplier.

Below, Section 2 gives the cost of common feed grade trace element sources and Section 3 gives the costs of commercial veterinary products.

The costs of ingredients in top quality mineral mixes for cows on silage or summer pasture (Mix (a)) or cows on tetany-prone pasture (Mix (b) are shown below.

Mix (a): The levels of Ca, P, Mg and Na in the mix are adequate for diets based on grass-silage or summer grass. The trace elements are included at the medium levels (as below) and vitamins A, D3 and E are included also. The total cost of the raw ingredients is 3.7 p/cow/d, provided in 118 g of mineral-vitamin mix.

The cost of the raw ingredients (using retail prices, as shown) would be IR 317/tonne. Allowing extra costs of IR 50-200/tonne for mixing, bagging, labelling, transport and commission, the cost would be IR 367-517/tonne. At a daily allowance of 118 g/cow/d, the cost would, therefore, increase to 4.3-6.1 p/cow/d.

Mix (b): The levels of Ca, P and Na in the mix are higher than are usually provided at grass and the Mg level is adequate for tetany control. The trace elements are included at the top level and vitamins A, D3 and E are included also. The total cost of the raw ingredients is 5.8 p/cow/d, provided in 216 g of mineral-vitamin mix.

Because of the high levels of major- and trace elements provided, the total daily allowance of the mix is higher than is usually provided (120-140 g/cow/d). The cost of the raw ingredients (using retail prices, as shown) would be IR 270/tonne. Allowing extra costs of IR 50-200/tonne for mixing, bagging, labelling, transport and commission, the cost would be IR 320-470/tonne. At a daily allowance of 216 g/cow/d, the cost would, therefore, increase to 6.9-10.2 p/cow/d.

Effective mineral supplementation for the 150-day programme, can be supplied by a good Pre-Calver Mineral for 30 days (sprinkled 2-3 times/d over easy-feed), plus a good Post-calver mineral for 80 days (in the daily ration of concentrate or straights, or sprinkled 2-3 times/d over easy-feed, or in a small amount (0.5-1.0 kg) of palatable carrier), plus a good Tetany-Control Mineral for 40 days, fed in the same way as the Post-Calver Mineral. Table 1 shows typical formulations of each of these three different types of mineral mix. The cost is IR 5.43-9.30/cow.

Pre-calver minerals (Table 1), at IR 250-500/tonne, at 100 g/cow/day, cost 2.5-5.0 p/cow/day, = IR 0.75-1.50 for 30 days. Post-calver minerals (Table 1), at IR 300-500/tonne, at 125 g/cow/day, cost 3.75-6.25 p/cow/day, = IR 3.00-5.00 for 80 days. Tetany control minerals (Table 1), at IR 300-500/tonne, at 140 g/cow/day, cost 4.2-7.0 p/cow/day, = IR 1.68-2.80 for 40 days.

The total cost of this 150-day programme (major elements, trace elements and vitamins) is IR 5.43-9.30/cow, or an average of 3.6-6.2 p/cow/d. This excludes the cost of the farmer's time in collecting and supplying those minerals. A carrier of 0.5-1.0 kg molassed rolled barley or beetpulp, if used (for example, in the tetany period on spring grass), would cost about 6.5-16.0 pence/cow/d extra, or IR 2.60-6.40 for 40 days. In that case, the total cost would be IR 8.03-15.70/cow, or an average of 5.4-10.5 p/cow/d.

Using these retail prices, the total trace element supplement (mid-range to high rate respectively) recommended by Teagasc for cows costs only 0.53-0.85 pence/cow/d. These amounts can be provided in a total of 5-8 g of trace element compounds.

The cost of raw ingredients for a 150-day programme of oral supplementation with the six important trace elements (Co, Cu, I, Mn, Se and Zn) is IR£0.80-1.27/cow. This excludes the cost of the farmer's time and facilities in collecting and supplying feed-grade compounds of those minerals. This cost is about one seventh of the cost of good commercial mineral-vitamin mixes.

If individual intakes are not controlled very carefully, it is dangerous to use trace element salts neat (undiluted). Therefore, trace elements are usually provided in diluted form in a carrier of dicalcium phosphate, calcined magnesite and common salt. These provide useful supplements of Ca, P, Mg and Na, as discussed in Section 1 above.

For comparative costing purposes with oral minerals, we assume that veterinary products must be given in adequate amounts to provide full cover for 150 days.

Excellent products include: Cu oxide boluses; Cu-EDTA injection; Na selenite or selenate injection; trace element bullets (Ionox (I, Se, Co), Cosecure (Co, Se, Cu), Alltrace (Co, Se, Cu)). Products under review include Deposel and Co bullets. Although not recommended, or recommended only as a last resort, iodine injections and Mg bullets are costed also.

Cu sulphate orally for 150 days (1.18-1.77 g/d = 300-450 mg Cu/d): The cost would be 18-27 pence/cow.

Cu oxide boluses: (Copinox, Copacaps, Copporal, Coprite) The wholesale price is IR 1.40/adult dose (21-27 g). The cost of 3 doses (given 4 weeks pre-calving and repeated at 1 and 6 weeks post-calving) is IR 4.20.

Cu-EDTA injections: (Coprin, Bovicoppa). Avoid, if possible, especially close to breeding. The wholesale price is IR 1.00/injection (100-120 mg Cu). The cost of 3 injections (given 4 weeks pre-calving and repeated at 1 and 3 weeks post-calving) is IR 3.00.

Na selenite orally for 150 days (16.7 mg/d = 5 mg Se/d): The cost would be 3 pence/cow.

DIY Na selenate injections (1 mg Se/ml in sterile distilled water (dose 50 ml/cow, 4 times as above): The cost would be 3 pence/cow.

Na selenite or selenate injections: All the soluble Se injections listed in the 1992 Veterinary Drug Update (Ireland) contain vitamin E also ("Selenium + Vitamin E", Vitenium, Vitesel, Duphrafral). The retail price is IR 0.74-1.90/shot (5-15 mg Se). The cost of 4 injections (given 4 weeks pre-calving and repeated at 1, 6 and 11 weeks post-calving) is IR 2.96-7.60. The dose rate recommended by the supplier is very small (5-15 mg Se/cow) as compared with doses used by us, when we made our own injections from sodium selenate and sterile distilled water. Our injection was 1 mg Se/ml, dose up to 50 ml/cow, i.e. 50 mg Se/cow/shot. If commercial injections were to be used at our dose rates, the 150-day cost would increase five-fold, to about IR 14.80-38.00/cow.

Deposel: The annual dose is 10 ml (2 X 5 ml injections = 500 mg Se). A half dose (one injection, 250 mg Se) at 4 weeks pre-calving might last 150 days. The wholesale price is IR 2.00/injection.

Trace element bullets: Cosecure or Alltrace: One dose of 2 bullets, given about 1 month pre-calving, would supply adequate Cu, Se and Co for 150 days. Ionox: One dose of 2-3 bullets, given about 1 month pre-calving, would supply adequate I, Se and Co for 150-240 days.

Oral Cu, Se, Co dosing: The cost of 1.18-1.77 g Cu sulphate + 16.7-24.0 mg Na selenite + 35.7-47.6 mg Co sulphate/cow/d for 150 days (as in the table above) would be 24-35 pence/cow.

Cosecure bullets (100 g bullets, with 0.5% Co, 0.3% Se, 13.4% Cu only): The wholesale price is IR 2.30 each. Two bullets, would cost IR 4.60/cow.

Alltrace bullets (Co, Se, Cu only): The retail price is IR 2.10 each. Two bullets would cost IR 4.20/cow.

Co sulphate orally (35.7-47.6 mg, or 7.5-10.0 mg Co/cow/d) for 150 days (as in the table above): The cost would be 3-5 pence/cow.

Co bullets for cows: (contain 9 g Co oxide only): The wholesale price is IR 1.83 each. Two bullets, would cost IR 3.66/cow.

Tincture of I can be bought in two strengths: 5% and 2.5%. The latter is the more common and retails at IR 8.00-9.20/litre: 2 ml of 2.5% tincture or 1 ml of 5% tincture gives 50 mg I, an I supplement in the top end of Teagasc recommendations. The cost for 150 days would be IR 2.40-2.76/cow.

Potassium iodide (KI) (76.4% I) can be bought at IR 13.50/kg. A dose of 66 mg (supplying 50 mg I) would cost 0.089 p/cow/d. The cost for 150 days would be 13.4 pence/cow.

4. Methods of last resort

Methods of supplementation that are not recommended, or are recommended only as a last resort, include soil fertilisation with Co or Se compounds, iodine injection and magnesium bullets.

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