Ovine Clinical Hypocalcaemia (so-called
“Lambing Sickness” in Ewes)
Phil
Rogers MRCVS, Grange Research Centre, Dunsany, Co. Meath
A
seminar for Teagasc Sheep Advisers, Teagasc Office Athenry,
Feb 22nd,
2003
SUMMARY
Hypocalcaemia
means subnormal Ca in blood. The most common clinical manifestations of
severe hypocalcaemia are "Lambing Sickness", a misnomer for
clinical hypocalcaemia in ewes: it is RARE at lambing, and it has a very WIDE
"onset time-window". Onset may be from 8 weeks before to 6 weeks
after partus, but most frequently 2-4 weeks
prepartum.
Clinical
hypocalcaemia usually occurs in pregnant or recently-lambed ewes, but can
arise in non-pregnant ewes, and in lambs & wethers
under adverse conditions of diet: sudden changes of feed to grazing on lush
green oats, barley or wheat; heavy cereal intakes; housing in dark pens (Vit D deficiency); feeding excess of beet pulp may induce
secondary hypocalcaemia.
An
energy deficit (which can also trigger ketosis, especially in ewes carrying
multiple lambs), low Ca intake (3.5g/ewe/d) &
excessive P in concentrates (6.9g/kg DM) can trigger hypocalcaemia.
Excess
Ca throughout pregnancy may trigger hypocalcaemia in late pregnancy,
Excess
Mg supplements in late pregnancy & stress before lambing are predisposing
factors.
Scan
ewes early in pregnancy; identify those with twins & triplets; ewes
carrying 2 or 3 lambs need more nutrients (especially energy & protein)
than those carrying singles.
Avoid
having ewes overfat in the last 6 weeks of
prepartum.
Avoid
stress, where possible, especially: sudden changes of feed, sudden
introduction of concentrates, sudden food scarcity.
Ensure
good management after introduction of concentrates to minimise
problems due to unequal feed intake.
|
Hypocalcaemia means subnormal calcium (Ca) in blood. It
often exists without clinical signs (non-clinical form). The most common
clinical manifestations of severe hypocalcaemia in ewes and cows are “Lambing Sickness” in ewes and “Milk Fever” in cows.
On February
17 2004, a search of the Commonwealth Agricultural Bureau abstracts database (CABI)
for the terms: "(OVINE OR EWE OR EWES OR SHEEP).TI. & (HYPOCALCAEMIA
OR HYPOCALCEMIA OR LAMBING- SICKNESS OR LAMBING ADJ SICKNESS).TI." found disappointingly
few (circa 30) abstracts on the problem. This is in marked contrast to the high
number of abstracts on bovine hypocalcaemia & milk fever.
The paucity of scientific literature on
ovine hypocalcaemia reflects the low priority given to nutritional research in
ewes, as compared with cows. It also means that Teagasc must rely for national
advice on methods of control on wobbly foreign data plus uncontrolled field
observations under Irish conditions by David Poole & his team in the Field
Investigations Dept of An Foras Taluntais.
KEY BULLET POINTS
Lambing Sickness in
ewes
|
Milk Fever in cows
|
This is a misnomer for clinical hypocalcaemia
in ewes:
- it is RARE at lambing,
- and it has a very WIDE "onset
time-window".
|
This is a misnomer for clinical hypocalcaemia
in cows:
- there is no fever,
- and it usually has a precise “onset time window”.
|
Onset may be from 8
weeks before to 6 weeks after partus, but most
frequently 2-4 weeks prepartum (Mosdol & Waage, 1981).
About 80% of cases
occur in the last 6 weeks prepartum; worse in overfat
ewes.
|
Onset usually is at partus +/- 1 day.
About 95% of cases
occur then; worse in overfat cows.
|
AVOID routine high
magnesium (Mg) supplementation of ewes (>2g Mg/ewe/d) in late pregnancy (prelambing).
High Mg supplements in
late pregnancy reduce gastrointestinal Mg absorption and exaggerate hypocalcaemia.
|
Routine supplementation
with 0.0g Ca + 15g Mg (30g Calmag)/d to COWS in the
last 4-6 weeks prepartum helps to maintain maximal bone Ca-turnover.
This is an important
part of milk fever prevention, because it ensures that the fall in blood Ca
on the day of calving is not as severe as it would be without the Mg supplement.
|
CLINICAL HYPOCALCAEMIA IN EWES
Between-farm prevalence of hypocalcaemia 2-6 weeks before lambing
ranged from 1 to >10% after the drought broke in
1983 in Victoria. During the outbreaks herbage had low
contents of Ca & DM. Predisposing factors could have been Ca deficiency (inadequate
supplementation with limestone) during the drought & the stress of routine crutching before
lambing (Larsen et al., 1986).
There are TWO forms of clinical hypocalcaemia in ewes:
- (a) hypocalcaemic paresis, the most common form;
- (b) hypocalcaemic tetany,
a hyperaesthetic form (rare in ewes but not uncommon
in bitches, cows and mares);
- Common signs in affected ewes include ataxia,
recumbency, depression, loss of anal reflex, tachycardia,
tachypnoea, hyposensitivity, ruminal stasis,
ruminal tympany, salivation & constipation (Cockcroft
& Whiteley, 1999; Popov, 1979).
- Hypocalcaemia, especially at lambing (Elias, 1991), predisposes to prolapse of uterus & intestine (Tindall, 1986), & to higher ewe & lamb mortality (Daniels & Moodie, 1979; Daniels, 1980; Mosdol & Waage, 1981).
BACKGROUND & PREDISPOSING FACTORS
- Clinical hypocalcaemia usually occurs in pregnant or recently-lambed ewes, but
can arise in non-pregnant ewes,
and in lambs & wethers under adverse conditions of diet:
- sudden changes of feed to
grazing on lush green oats, barley or wheat;
- heavy cereal intakes;
- housing in dark pens (Vit D deficiency);
- feeding excess of beet pulp may
induce secondary hypocalcaemia.
- Fat ewes are especially susceptible.
- Increased
feed intake,
especially by older ewes, may lead to acidosis, followed by inappetence & hypocalcaemia. Good management after
introduction of supplementary rations is necessary to minimise
problems due to unequal feed intake (Pickard et al., 1988).
- An energy
deficit (which can also trigger ketosis, especially in ewes carrying
multiple lambs), low Ca intake (3.5g/ewe/d) & excessive P in concentrates
(6.9g/kg DM) can trigger hypocalcaemia (Sweeney & Cuddeford,
1987). Gross dietary Ca deficiency predisposes to ewe hypocalcaemia.
- Massive
intakes of oral Ca in early pregnancy did not raise the
risk of hypocalcaemic paresis (Luthman, 1977), but excess Ca throughout
pregnancy may trigger hypocalcaemia in late pregnancy (Jonson et al., 1973).
- Temporary inhibition of bone resorption
may induce hypocalcaemia (Luthman, 1977).
- Normal concentration of Mg in ewe rations (5g/kg)
does not predispose sheep to hypocalcaemia (Pickard et al., 1988). However, high dietary Mg
levels can trigger an outbreak, especially when Ca intakes are low; high
Mg can reduce the availability of dietary Ca (Tindall, 1986).
- Plasma
inorganic P may
be high (Papasteriadis, 1973), normal (Luthman, 1977;
Fenwick & Daniel, 1992), or low (Jonson et al., 1973). Plasma Mg also may be high (Mosdol & Waage, 1981), or normal (Elias, 1991; Luthman, 1977; Vihan & Rai, 1985). Hypomagnesaemia is very rare
in classical cases of lambing sickness.
TREATMENT
Note that many late-pregnant ewes present
with a COMBINATION of ketosis & hypocalcaemia, & that these disorders
are very difficult to differentiate on clinical grounds, EVEN if one does ketone tests on urine (Bickhardt et al., 1998).
The practical implications of this are
that downer ewes, or ewes with either paretic or tetanic
signs in late pregnancy, usually receive “shotgun” treatment for BOTH ketosis
& hypocalcaemia. Treatment of clinical hypocalcaemia in ewes may consist of
- + s/c injection of Vit
D analogue (cholecalciferol),
+ Vit E (alpha-tocopherol),
+ Na selenite + oral Na propionate (Bickhardt et al., 1998).
- Add 15g
DICAL/ewe/d (22%
Ca, 18% P) to the supplement for TREATED ewes (Tindall, 1986).
- If hypomagnesaemia is present also [very rare in
the literature], also inject Mg sulphate s/c and
feed or dose TREATED ewes with 3-5g Mg (6-10g Calmag)/ewe/d
for a week or so. This may be useful to prevent RELAPSE in ewes ALREADY
TREATED for hypocalcaemia. However, simultaneous hypomagnesaemia is
uncommon in hypocalcaemic ewes. Therefore, Mg
injection (and the subsequent oral Calmag)
actually may add relatively little to the clinical outcome in ewes with
normal blood Mg levels.
- Even for ewes at grass AFTER lambing, a supplement of 5g Mg (10g Calmag)/ewe/d
is adequate to PREVENT GRASS TETANY in most flocks. One might increase the
Mg supplement to 7-14g Mg (0.5-1.0oz Calmag)
under conditions of very high risk of tetany.
Note, however, that, adjusting for a 10-fold difference in liveweight
between cows & ewes, a dose of 7g Mg/ewe/d is very high relative to
the effective tetany-prevention dose in cows
(30-40g Mg/cow/d).
PREVENTION
There are very few definitive papers on
control of ovine hypocalcaemia. The most recent refers to a novel idea – Calcigard (Wilson, 2001; Wilson et al., 2003), a patented product based on Soya Oil.
The product successfully prevented experimental fasting-induced hypocalcaemia
in ewes. Unfortunately, it has little if any practical application in preventing
Lambing Sickness. This is because Calcigard was
developed for use in COWS, in which the “time window” for hypocalcaemia is very
narrow (partus +/- 1 day).
The idea is to feed the oil to cows for 3 weeks prepartum to boost Ca
absorption capacity by complexing dietary Ca, thereby
reducing the bio-availability of Ca from pasture & stimulating the
homeostatic mechanisms by so doing.
- Scan ewes
early in pregnancy; identify those with twins & triplets; ewes carrying 2 or 3 lambs
need more nutrients (especially energy & protein) than those carrying
singles.
- Segregate ewes carrying singles v multiple
lambs & feed accordingly.
- Minimise unequal
feed intake; this causes problems.
- Avoid having ewes overfat in the last 6 weeks of prepartum.
- Avoid underfeeding, even
short-term underfeeding.
- Avoid
excessive Ca intakes in pregnancy; this exaggerates the risk of hypocalcaemia in
ewes as well as in cows (Jonson et al., 1973). However, also avoid
excessively low Ca intake, and excessively high P intake. High P reduces Ca
absorption, and vice-versa.
- Avoid high
Mg supplements in pregnancy: Excessive oral Mg reduces Ca absorption. I
do NOT recommend 0.5-1.0oz (14-28g) of Calmag/ewe/d
prelambing. That amount provides 7-14g
Mg/ewe/d; it is grossly excessive.
- If farmers want to feed Mg routinely, keep it
down to 1-2g Mg/ewe/d until lambing.
- Avoid
stress,
where possible, especially:
- sudden changes
of feed,
especially sudden introduction of concentrates.
- sudden food
shortage,
even short-term; fasting or seriously reduced feed intakes can
precipitate clinical hypocalcaemia within 2-3 days.
- cold-stress; housing in harsh weather may help but
hypocalcaemia can arise in housed sheep also (Tindall, 1986).
- rough handling for crutching, etc.
- any handling that causes fear or fright.
- Consider
acidification of the diet (Grant et al., 1992), but there are no
other data on that method in the past 12 years.
REFERENCES
Barzanji-A-A-H,
Daniel-R-C-W.
| 1987
| Effect of hypocalcaemia
on blood flow distribution in sheep.
| Research
in Veterinary Science; vol 42; no 1; pp 92-95; ISSN:
0034-5288; 9 ref.
| Dep Vet Med, Univ,
Brisbane
,
Queensland
,
Australia
.
| Cardiac
output, the proportion of blood passing through arteriovenous
shunts & blood flow distribution to various organs were measured &
compared in 5 normocalcaemic & 5 hypocalcaemic
sheep using radioactive microspheres. Hypocalcaemia
was induced by infusing Na EDTA solution intravenously for 2h. There was
evidence that microspheres were leached from liver,
muscle, adrenal & thyroid tissues during the induction of hypocalcaemia.
Hypocalcaemia reduced blood flow rates by more than 58% in all tissues
examined except kidney (48%), heart (53%), lung (10%) & bladder (47%) &
reduced cardiac output from 3.70+/-0.19 litres/min to 2.39+/-0.14 litres/min.
Approximately 2.2% of cardiac output passed through arteriovenous
shunts. This % was unaffected by hypocalcaemia.
Bickhardt-K,
Henze-P, Ganter-M.
| 1998
| Clinical
findings & differential diagnosis of ketosis & hypocalcaemia in sheep.
| Deutsche Tierarztliche
Wochenschrift; vol 105;
no 11; pp 413-419; ISSN: 0341-6593; 25 ref.
| Tierarztliche
Hochschule, D-30173
Hannover
,
Germany
.
| 454 sheep
with metabolic disorders were examined during a 20-year period (1978-1998),
including 214 ewes with ketosis (pregnancy toxaemia), 195 ewes
with hypocalcaemia, & 40 ewes with
both disorders. There was little difference between the 3 groups in clinical findings,
neither could they be distinguished by the occurrence of acetonuria.
A universal treatment, regardless of the underlying condition, consisted of
oral administration of Na propionate, Ca lactate & K chloride, commencing
with s/c injection of Ca borogluconate, cholecalciferol,
alpha-tocopherol & selenium. Prevention by
appropriate feeding is discussed.
Cabello-G,
Wrutniak-C.
| 1989
| Effects of
transient, corrected ovine maternal hypocalcaemia on neonatal
endocrine & metabolic function.
| Research
in Veterinary Science; vol 47; no 1; pp 54-59; ISSN:
0034-5288; 28 ref.
| Unite Differentiation Cellulaire Croissance,
INRA-ENSA, 9 place Viala,
34060
Montpellier
,
France
.
| The
newborn changes in plasma levels of thyroid stimulating hormone, iodothyronines,
cortisol, insulin, glucose, urea & representative parameters of lipid
metabolism, were monitored in 8 control lambs & 10 lambs born from hypocalcaemic
mothers. 8h after lambing, plasma total lipid, free fatty acids, cholesterol
& phospholipid levels were higher in animals
from hypocalcaemic mothers than in control lambs.
Moreover, these lambs were clearly hyperthyroid during, at least, the first 48h
of life. In lambs born from hypocalcaemic mothers,
plasma insulin levels were depressed, despite normal glucose concentrations.
Plasma cortisol levels were higher than in control lambs, suggesting an
endocrine response to a prolonged stress. All these results showed that hypocalcaemic
& related metabolic events occurring near the term of pregnancy in ewes
could induce newborn hyperthyroidism, hypoinsulinaemia
& metabolic alterations in their offspring.
Cockcroft-P-D,
Whiteley-P.
| 1999
| Hypocalcaemia
in 23 ataxic/recumbent ewes: clinical signs & likelihood ratios.
| Veterinary
Record; vol 144; no 19; pp 529-532; ISSN: 0042-4900;
5 ref.
| Department
of Clinical Veterinary Medicine,
Madingley
Road
,
Cambridge
CB3 0ES
,
UK
.
| 23/2000 ewes
in a
UK
flock were
identified as having acute onset ataxia and/or having become recumbent in late
pregnancy & early lactation. The presence or absence of
15 clinical signs were recorded. 13 of the ewes (57%) were hypocalcaemic
& 10 (43%) were normocalcaemic. In the hypocalcaemic
group, loss of anal reflex, constipation, tachycardia, hyposensitivity, ruminal
stasis, ruminal tympany, salivation & tachypnoea
were recorded in 50% or more of the cases. In the normocalcaemic
group, tachycardia, tachypnoea & ataxia were
recorded in 50% or more of the cases. Constipation, ruminal stasis, salivation
& hyposensitivity had likelihood ratios of 3 & above for being
associated with hypocalcaemia. Ruminal stasis & hyposensitivity had
the likelihood ratios of 0.10 & 0.11 respectively for not being associated with hypocalcaemia.
Daniels-R-C-W.
| 1979
| (I)
Changes in bromosulphalein fractional clearance
& plasma volume in induced hypocalcaemia in cows. (II The effect of
reducing plasma Ca levels on some plasma enzyme levels in cows & sheep.
| British
Veterinary Journal; vol 135; no 1; pp 25-39; ISSN:
0007-1935; 23 ref.
| Dep
Vet Med,
Univ
,
St Lucia
,
Queensland
4067,
Australia
.
| Induction
of hypocalcaemia to a mean plasma Ca level of 0.82+/-0.60 mmol/l
(mean+/-SEM) in 5 cows did not change BSP fractional clearance rates
significantly, but reduced plasma volumes by approximately 24%. This reduction
did not appear to be due to the effects of recumbency resulting from the hypocalcaemia.
Elevations of plasma AAT, CPK & LDH occurred in cows in which hypocalcaemia
was induced by the infusion of 4.7% Na2EDTA. Levels of alpha HBDH during the
same period did not differ significantly from those obtained during a control
infusion of 0.9% saline in the same cows over a similar period, suggesting that
the rise in LDH levels was due to isoenzymes other
than LDH-1 & LDH-2. The rises in AAT, CPK & LDH were due to release
from skeletal muscle tissue & the effects of recumbency may have
contributed. In 6 wethers increase of plasma CPK
activity, which was not due to the effects of recumbency, occurred in
hypocalcaemia induced by the infusion of 4.7% Na2EDTA solution.
Daniels-R-C-W,
Moodie-E-W.
| 1979
| Induced hypocalcaemia
in cows & sheep. 1. Changes in plasma inorganic P levels.
| British
Veterinary Journal; vol 135; no 5; pp 440-451; ISSN:
0007-1935; 22 ref.
| Dep
Veterinary Medicine, Univ
Queensland
,
Brisbane
,
Australia
.
| There were
8 cows aged 4 years or over, not lactating, either not pregnant or pregnant for
less than 3 months. Hypocalcaemia was induced in each cow until the
recumbent comatose stage by infusion of 4.7% Na ethylenediamine
tetraacetate (Na2EDTA). The cows were allowed to
recover spontaneously except that 2 had to be treated to prevent death. The 7
controls got saline infusion. A 2nd group of 6 cows had hypoglycaemia induced to
a stage just preceding recumbency then each was treated with Ca borogluconate
intravenously. The 3rd group of 8 cows were cast & restrained in sternal
recumbency for 3 h; the 3 controls remained standing. 6 sheep 15-30
months old had hypoglycaemia induced but were
supported to prevent recumbency. They were allowed to recover spontaneously; 6
controls got saline. Blood was collected before infusion & 1, 2, 3, 4, 5, 6,
10 & 22h after it began from cows of the 1st group & the sheep,
& at 30-min intervals from cows of the 2nd group with another sample taken
within 5 min of the infusion of Ca borogluconate.
Plasma Ca & inorganic P were estimated in blood taken initially & 2, 3
& 4h after start of infusion of Na2EDTA. Regression coefficient of plasma
inorganic P concentration on plasma Ca concentration calculated from pooled
results for the 8 cows during induction of hypocalcaemia was 0.400 (p
<0.01) with correlation coefficient 0.843. For the total period of induction
& spontaneous recovery in the 6 cows of the 1st group there was a similar
relation & a regression coefficient of 0.448. Results for the 2nd group of 6
cows supported that relation but the more frequent sampling showed that
regressions differed significantly between cows. There was no significant
difference in response of inorganic P between treated sheep &
controls although changes in inorganic P tended to follow those of Ca in the
treated sheep & there were significant differences between individual
regression coefficients. Inorganic P had a significant mean increase of
0.46 mmol/litre for 6
cows immediately after treatment with Ca borogluconate.
Forced recumbency of cows resulted in a significant fall, p <0.001, in
inorganic P. Possible reasons for the changes in inorganic P are
discussed.
Daniels-R-C-W.
| 1980
| Induced hypocalcaemia
in cows & sheep. 2. Changes in plasma K levels. 3. Changes in plasma
Mg levels.
| British Veterinary Journal; vol 136; no
1; pp 45-56; ISSN: 0007-1935; 22 ref.
| Dep
Vet Med, Univ,
Brisbane
,
Queensland
,
Australia
.
| Mean
plasma K levels were significantly lowered by 0.39 mmol/1 & 0.48 mmol/1,
respectively, for a decrease of 1 mmol/1 in EDTA titratable
plasma Ca level in 2 groups of cows in which hypocalcaemia was induced to
the 'recumbent comatose' stage by the infusion of Na2EDTA over approximately 3h.
In these cows plasma K levels did not return to normal in parallel with plasma
Ca & did not start to rise until at least 2h after the nadir of hypocalcaemia.
Plasma K levels remained relatively constant in a control experiment in which
saline infusions over a similar period of time were carried out in the larger
group of cows. Analysis of variance of the results in this group of cows showed
a significant cow x infusion interaction. No difference in response of plasma K
levels was observed in 2 groups of 6 wethers, one of
which was infused with 0.9% saline & acted as a control group while the
other was infused with Na2EDTA & hypocalcaemia induced. The possible
roles of parathormone & stress in producing the
observed changes in plasma K levels are discussed. (Observations on changes in
plasma Mg concentration in cows in which hypocalcaemia (plasma Ca down to
1.10 mmol/1) was induced by the infusion of Na2EDTA failed to show any
significant mean differences in response when compared with changes in levels in
the same cows infused over a similar period of time with 0.9% saline. A
significant cow x infusion interaction suggested between-cow variation in
differences in response of plasma Mg to the 2 infusions. Regression coefficients
of plasma Mg on plasma Ca differed significantly between cows during the
induction of hypocalcaemia. In a group of 6 merino wethers,
a significant mean fall in plasma Mg occurred in association with induced
hypocalcaemia when compared with a control group infused with saline. The
regression coefficients of plasma Mg on plasma Ca concentrations from the pooled
results were 0.072+/-0.024 (+/-Sb) &
0.054+/-0.021 mmol/1 (+/-Sb) for the induction phase
& induction-plus-recovery phases of hypocalcaemia,
respectively.
Elias-E,
Shainkin-Kestenbaum-R.
| 1990
| Hypocalcaemia
& serum levels of inorganic P, Mg, parathyroid & calcitonin
hormones in the last month of pregnancy in Awassi
fat-tail ewes.
| Reproduction, Nutrition, Development; vol
30; no 6; pp 693-699; ISSN: 0926-5287; 29 ref.
|
Ben
Gurion
University
of the
Negev
,
PO Box 653
,
Beersheva
84105
,
Israel
.
| Serum
levels of Ca, inorganic P, Mg , parathyroid (PTH)
& calcitonin (CT) hormones of fat-tail Awassi
ewes were determined during the last month of pregnancy. The incidence of
hypocalcaemia (HCE) was 13.4% of the obstetrical cases examined. 26
(81.3%) of 32 ewes with HCE were >/= 4 yr of age or older. Significant
decreases in serum Ca levels (normal values or controls; 10.04+/-0.22% (w/w)) to
pathological values (4.30+/-0.35% (w/w)) caused severe clinical manifestations
in 75% of affected ewes. This HCE was accompanied by a significant
increase in the PTH level (142.6+/-9.1 pmol/litre
in comparison to 99.7+/-9.3 pmol/litre)
in controls, & significant decrease in serum CT level (98.2+/-7.6 pg/ml in
comparison to 144.6+/-25.7 pg/ml in controls). Ca borogluconate
i/v yielded normal Ca values which were accompanied
by a decrease in serum PTH & an increase in CT to normal values.
Elias-E.
| 1991
| Hypocalcaemia
& oestradiol-17 beta levels in Awassi fat-tail ewes
with uterine prolapse.
| Israel Journal of Veterinary Medicine; vol
46; no 4; pp 134-137; ISSN: 0334-9152; 18 ref.
| Isan
Center for Comparative Medicine, Ben Gurion
University of the Negev, PO Box 653, Beer Sheva
84105, Israel.
| Blood
samples were taken from 34 Awassi ewes in
Bedouin flocks, presenting uterine prolapse. Serum levels of Ca, inorganic P, Mg
& oestradiol-17 beta (E2) were measured in these ewes & in 6
control ewes after normal lambing. Serum Ca concentration was
significantly reduced with no accompanying changes in P or Mg levels, in ewes
presenting uterine prolapse 13h or more after lambing. Levels of
oestradiol-17 beta displayed a normal pattern of decrease after lambing without
correlation to serum Ca levels. Parturient hypocalcaemia may play a major
role in the aetiology of uterine prolapse.
Fenwick-D-C,
Daniel-R-C-W.
| 1992
| Investigation
of some pathophysiological effects of prolonged hypocalcaemia
in sheep induced by infusing Na3EDTA solution for 4h daily on 3
consecutive days.
| British Veterinary Journal; vol
148; no 4; pp 301-313; ISSN: 0007-1935; 29 ref.
| Department
of Physiology & Pharmacology,
University of
Queensland
,
St Lucia
4072,
Australia
.
| Hypocalcaemia
was induced in a group of 5 aged Merino ewes (with low erythrocyte K
status) by the i.v. infusion of 4.7% Na2EDTA
solution for 4 h/d on 3 consecutive days. A similar control group was infused
with 5.0% dextrose solution (10 ml/h) for the same period. Blood samples were
taken immediately before infusion each day, hourly for 7 h, then at 8:00 each
morning for a further 5 d. Studies were made on the changes in plasma (P) Ca, PNa,
PK, PMg, PProtein (PProt),
inorganic P (PiP), erythrocyte (E) Na, EK, EMg,
PCVs, & mean corpuscular cell volumes (MCV). Significant
decreases occurred in PiP concentrations but these
were only temporary, suggesting that PiP is unlikely
to be involved in the complications of prolonged hypocalcaemia. Significant
prolonged decreases in PNa, PK & EK &
significant prolonged decreases in PNa, PK & EK
& significant prolonged increases in PCVs
suggested that fluid replacement therapy supplemented with Na & K may be
worthy of further study in the treatment of ruminants affected by apparent
biochemical or physiological complications to prolonged hypocalcaemia.
Fenwick-D-C,
Daniel-R-C-W.
| 1992
| Blood pathophysiological
changes in sheep following a prolonged (18-hour) period of hypocalcaemia
induced by Na2EDTA solution.
| British
Veterinary Journal; vol 148; no 5; pp 425-434; ISSN:
0007-1935; 19 ref.
| Department of Physiology & Pharmacology,
University
of
Queensland
, Qld
4072,
Australia
.
| 6 aged
Merino ewes were used in an experiment in which 5 were infused with 4.7%
Na2EDTA solution i.v. for 18h at a rate designed to
produce hypocalcaemia & maintain recumbency, & 5 with 0.9% Na
chloride solution at the same rate for the same period (4 were infused at
different times with both solutions). Blood samples were collected every 3h
& analysed for plasma Ca, Na, K, Mg, & inorganic P (PiP),
erythrocyte Na, K & Mg, & PCV. 3 of the hypocalcaemic
sheep took 36-64h to regain their feet. Plasma Ca & K,
& erythrocyte Na showed significant decreases in the group infused with
Na2EDTA compared with the group infused with saline while PCVs
were significantly greater in the former group. The sheep model used
could be suitable for the study of the effects of prolonged hypocalcaemia
& recumbency in cows.
Grant-I-M,
Bingham-A-M, Caple-I-W.
| 1992
| Acid-base
balance & susceptibility of ewes to hypocalcaemia.
| Proceedings
of the Australian Society of Animal Production; vol
19; pp 412-415; 11 ref.
|
University
of
Melbourne
, Department of
Veterinary Science, Werribee, 3030,
Australia
.
| The effect
of acid-base balance on the susceptibility of ewes to hypocalcaemia
was studied in groups of ewes fed on diets in which the fixed cation-anion
balance (Na + K - Cl) was -4.1, 29.1 & 82.3
mequiv/100g DM, respectively. Ewes fed on the diet with a fixed cation
excess (82.3 mequiv/100g DM) had higher urine pH & lower urine Ca
concentration. They also had lower blood ionized Ca concentration after an
overnight fast, & tended to develop hypocalcaemia more rapidly during
EDTA infusion than ewes fed on a diet with a fixed anion excess (-4.1
mequiv/100g DM). Dietary fixed cation-anion
balance may be a factor which predisposes pregnant ewes to hypocalcaemia.
Jones-B,
Luthman-J.
| 1978
| Feeding-induced
hypocalcaemia. Studies on the uptake of 47Ca from the GIT of sheep.
| Acta
Veterinaria Scandinavica;
vol 19; no 2; pp 204-214; ISSN: 0044-605X; 9 ref.
| Dep
Medicine II, Swedish Univ Agricultural Sciences,
S-750 07
Uppsala
,
Sweden
.
| Ewes
2-6 years old in 4 groups of 8 were taken from pasture & fed only on hay for
1 month. Then concentrate was added to the ration of 3 groups at 0.2, 0.4 or 0.6
kg/d. The pelleted concentrate was oats & barley
each 41% soya bean oilmeal
8%, rapeseed oilmeal 3.6% & cottonseed oilmeal
6.4%. Blood was sample at regular intervals. The hay had Ca 4.9, P 1.3 & Mg
1.3g/kg & the concentrates had 1.5, 4.0 & 1.6g/kg. Values for metabolizable
energy & digestible protein were calculated. 6 rams about 7 months old,
26-32kg LW, were used to study the gastrointestinal absorption of 47Ca given
into the rumen. They were fed only on hay for 1 month then got 100 mu
Ci 47Ca. 10d later concentrate up to 0.6 kg/d was
given. 5d later a 2nd injection of 47Ca was given. Twelve yearling heifers were
used to study the effect of concentrate on blood Ca. 6 animals were controls
given hay to appetite, & the others got hay to appetite & 3kg
concentrate a day. Serum Ca, inorganic P, Mg & alkaline phosphatase
were estimated. Concentrate 0.4 kg/d was required to induce a profound drop
in serum Ca. The same changes occurred in heifers at 3 kg/d. The isotope
studies showed that the fall in serum Ca was probably not caused by a reduced
gastrointestinal uptake of Ca.
Jonson-G,
Luthman-J, Mollerberg-L,
Persson-J.
| 1973
| (Feeding
of minerals to flocks of sheep affected with hypocalcaemia).
| Nordisk
Veterinaermedicin; vol
25; no 2; pp 97-103.
| Veterinarhogskolan,
Stockholm
,
Sweden
.
| Serum
values of Ca, P, Mg & alkaline phosphatase were
measured in samples from 14 ewes which required treatment for hypocalcaemic
paresis, & the mean values of the same parameters
were determined for 3 flocks in which cases of hypocalcaemia had
occurred. The results are tabulated. Serum Ca values were very low in the
paretic ewes, a mean of 3.4+/-1.3mg/100 ml. Some ewes showed
pronounced hypophosphataemia. One of the affected
flocks showed a low mean serum Ca value, 8.2+/-1.3mg/100 ml. Records &
analysis of the feed of the 3 flocks showed that all had been fed an excess of
Ca during the whole of pregnancy, & it is suggested that this may have
contributed to the development of hypocalcaemia towards the end of
pregnancy.
Jonsson-N-N,
Daniel-R-C-W.
| 1997
| Effects of
hypocalcaemia on blood flow to the ovaries of the sheep.
| Journal
of Veterinary Medicine. Series A; vol 44; no 5; pp
281-287; ISSN: 0931-184X; 24 ref.
| Queensland Department of Primary Industries, Mutdapilly
Research Station, MS 825 Peak Crossing 4306,
Queensland
,
Australia
.
| The effect
of hypocalcaemia on blood flow to the ovaries was studied in 6 Merino
cross sheep 12-18 months old, non-pregnant, in
Queensland
,
Australia
. Different levels
of hypocalcaemia were induced in 5 sheep by i.v.
infusion of 4.7% Na2-EDTA at a rate of 60-90 ml /h. The control sheep was
infused with 60 ml of 0.9% NaCl. Blood flow to the
ovaries was measured before & after the induction of hypocalcaemia
using 113Sn & 46Sc radiolabelled microspheres.
The plasma Ca++ decreased from 1.07-1.35 mmol/litre
before infusion to 0.39-1.17 mmol/litre after
infusion & ovarian blood flow decreased from 39.9-177 ml 100 g-1 min-1 to
39.6-152 ml 100 g-1 min-1. The following model was developed: ovarian blood flow
(% of resting)=0.54 Ca++ (% of resting)+58.4.
According to this model, a reduction in plasma ionized Ca of 50% would reduce
ovarian blood flow by 16%.
Larsen-J-W-A,
Constable-P-D, Napthine-D-V.
| 1986
| Hypocalcaemia
in ewes after a drought.
| Australian Veterinary Journal; vol 63;
no 1; pp 25-26; ISSN: 0005-0423; 8 ref.
| Dep
Agric, Vet Field Serv, State Government Office, Ballarat,
Vic 3350,
Australia
.
| The
prevalence of hypocalcaemia ranged from 1% to over 10% 2-6 weeks before lambing
in flocks in western
Victoria
after the drought
broke in 1983. Serum Ca values were 1-1.2 mM, &
the response to Ca borogluconate was rapid. The
dominant pasture species were Trifolium subterraneum
(usually rich in Ca & Arctotheca calendula).
Samples of herbage collected during the outbreaks had low contents of Ca, Mg,
K & DM. Predisposing factors could have been inadequate supplementation
with limestone during the drought & the stress of routine crutching before
lambing.
Luthman-J.
| 1977
| Hypocalcaemia
in ewes in late pregnancy: a cultural disorder?
| Svensk
Veterinartidning; vol
29; no 6; pp 217-221; ISSN: 0346-2250; 12 ref.
| Inst Medicin
II, Klinikcentrum, Veterinarhogskolan,
750 07
Uppsala
7,
Sweden
.
| Several
trials & studies on ewes are reported. In late pregnancy normal ewes
had Ca 9.67, P 4.79 & Mg 2.64mg/100 ml serum & alkaline phosphatase
35 mU/ml & ewes with paresis had 3.63,
4.04 & 2.64 mg & 18 mU. Sometimes in flocks
with cases of paresis all sheep had low blood Ca, but without clinical
sign, & slight stress might induce paresis. Serum P was generally high in
flocks with hypocalcaemia. Massive overdoses of Ca in early pregnancy
did not increase the risk of hypocalcaemic paresis.
Abrupt introduction of concentrate of any type reduced serum Ca, in one test
after 3-10d. As hypocalcaemia developed, hydroxyproline
decreased in blood. It was thought that hypocalcaemia might be induced by
temporary inhibition of bone resorption; that was
supported by testing the reaction to protamine by
vein.
Luthman-J,
Persson-J.
| 1977
| Feeding-induced
hypocalcaemia. Preliminary studies in sheep.
| Nordisk
Veterinaermedicin; vol
29; no 2; pp 90-95.
| Dep
Medicine II,
Veterinary
College
, S-750 07
Uppsala
,
Sweden
.
| 30 ewes
aged 4-8 years were accustomed to being fed 1.5kg hay/d & got a supplement
of pelleted concentrate at 0.5kg/d at the time of
mating. After about 3 months of pregnancy, controls continued on hay alone &
others got also 0.5kg crushed oats or pelleted
concentrate for 30d. Hay had Ca 6.2 & P 1.8g/kg, crushed oats had 0.9 &
3.6g/kg & concentrate had 7.4 & 5.6g /kg. In another
experiment 6 nonpregnant ewes
1-2 years old got 1.5kg hay/d for 3 weeks then 0.5kg concentrate was added.
Serum Ca, P, hydroxyproline, total protein, urea N
& alkaline phosphatase were estimated at
intervals & results are presented graphically. There was hypocalcaemia
about 2 weeks after the addition of oats or pelleted
concentrate to diets of pregnant or nonpregnant ewes
although concentrate increased the intake of Ca/d by about 40%.
Matthews-M,
Editor: Budge-G.
| 1999
| Hypocalcaemia in ewes post drought in
Hawkes
Bay
.
| 29th
Seminar of the Society of Sheep & Beef Cattle Veterinarians NZVA,
Hastings, New Zealand, 1-3 March 1999; Publication - Veterinary Continuing
Education, Massey University; no 189; pp 131-133; ISSN: 0112-9643; 1 ref.
| Veterinary
Services (HB) Ltd,
Hastings
,
New Zealand
.
|
Mosdol-G,
Waage-S.
| 1981
| Hypocalcaemia
in the ewe.
| Nordisk
Veterinaermedicin; vol
33; no 6/8; pp 310-326; 59 ref.
| Dep
Obstetrics,
Veterinary
College
of
Norway
, PB 8146 Dep,
Oslo
1,
Norway
.
| Hypocalcaemia
was defined as a disorder in which the plasma Ca was less than 2 mM.
Of 78 female sheep with clinical signs of hypocalcaemia 74.4% had hypocalcaemia
judged by their plasma Ca; of 99 with an uncertain clinical diagnosis of hypocalcaemia,
21.2% had it, judged by their plasma Ca. The disorder occurred from about 2
months before to 1.5 months after parturition, but most frequently 2-4 weeks
before parturition. Tendency to hypocalcaemia increased with age &
parity. Plasma Ca was highest in affected sheep that remained standing &
lowest in those with tetany. ASAT (asparaginic
acid aminotransferase), ALAT (alanine
aminotransferase), bilirubin,
Hb & packed cell volume (PVC) were significantly
higher in sheep with hypocalcaemia than in normal controls. With hypocalcaemia,
plasma Ca was related negatively to PCV & positively to plasma P
concentration. About 20% of affected sheep died; those had higher mean plasma Ca
& lower Mg at 1st treatment than those that recovered. Mortality rate was
greater in sheep treated after than in those treated before parturition. Of
those that recovered, 25% required more than 1 treatment. Among sheep that
developed hypocalcaemia while pregnant 22% of their young died; the main reason
was probably premature birth. The differential diagnosis of hypocalcaemia
is discussed in the light of clinical & biochemical findings in sheep
with normal serum Ca, in which hypocalcaemia had been diagnosed
clinically, with or without certainty of the diagnosis.
Papasteriadis-A.
| 1973
| Hypocalcaemia
in sheep in Greek conditions.
| Epistemonike
Epeteris Kteniatrikes Sholes,
Aristoteleion Panepistemion
Thessalonikes; vol 14;
pp 1-32.
|
| Of all sheep
brought to the medical clinics of the Veterinary College of Thessaloniki
for examination, 20% had metabolic disorders & 42.8% of those, 8.4% of the
total, had hypocalcaemia. Hyperphosphataemia
was constantly associated with the condition. Nutritional factors & dark
pens were incriminated. Parenteral administration of
vit. D gave beneficial results. The principal causes
in adult sheep were: heavy cereal intakes resulting in primary hypocalcaemia
& hyperphosphataemia; excess of beet pulp
inducing secondary hypocalcaemia; sudden changes of feed to grazing on
lush green oats, barley or wheat. In addition, lambs were kept in dark pens
leading to vitamin D deficiency. Values for serum minerals are tabulated.
Preventive management is discussed.
Persson-J,
Luthman-J.
| 1975
| Further
studies on theophylline-induced hypocalcaemia
in sheep.
| Acta
Veterinaria Scandinavica;
vol 16; no Fasc.1; pp 39-50; ISSN: 0044-605X.
| Dep
Med II, Royal Vet Coll, S-104 05
Stockholm
50,
Sweden
.
| The
effects of various doses of theophylline on the
plasma levels of Ca, inorganic P & Mg were studied in sheep. The dose
of 0.25mg/kg /min during 40 min produced a hypocalcaemia, which was
abolished by thyroidectomy. At a higher dose
(1mg/kg/min) thyroidectomy reduced, but did not
block the hypocalcaemic effect of theophylline.
Young sheep showed a greater Ca response than adult ewes. The
decrease in plasma Ca was in no case accompanied by hypophosphataemia.
Plasma Mg decreased in all groups after 1mg/kg/min, & was not influenced by thyroidectomy.
Theophylline increased the urinary
excretion of Ca & Mg. It is concluded that theophylline-induced
hypocalcaemia in sheep is in part a result of increased calcitonin
secretion but that also other mechanisms must be involved, e.g. a direct effect
of theophylline on bone.
Pickard-D-W,
Field-B-G, Kenworthy-E-B.
| 1988
| Effect of
Mg content of the diet on the susceptibility of ewes to hypocalcaemia
in pregnancy.
| Veterinary Record; vol 123; no
16; pp 422; ISSN: 0042-4900; 1 ref.
| Dep
Anim Physiology, Univ,
Leeds
,
LS2 9JT
,
UK
.
| In a flock
of 120 ewes, 4 weeks before the expected lambing date, rations
containing 2g Mg & 5g Ca/kg (Group 1), 2 mg Mg
& 15g Ca/kg (Group 2), 5g Mg & 15g Ca/kg (Group 3) or 10 mg Mg
& 15g Ca/kg (Group 4) were introduced in 2 feeds/d at a rate of 400g/ewe/d,
increasing to 500g/d after 3d. All rations contained 7g P/kg. 7 ewes (4
in Group 4, 2 in Group 2 & one in Group 1) showed clinical hypocalcaemia
after 4d. However, when 6 of these ewes were transferred to individual
pens & fed the same rations at up to 900g/d, no further incidents of hypocalcaemia
were seen. In another flock of 96 ewes, fed the same rations as above
with supervised feeding, only one case of hypocalcaemia occurred in a ewe
fed 10 mg Mg & 15g Ca/kg. The normal
concentration of Mg in ewe rations (5g/kg) does not predispose sheep to
hypocalcaemia. The authors suggest that increased feed intake, especially by
older ewes, may lead to acidosis, followed by inappetence
& then hypocalcaemia, & that good management after supplementary rations
have been introduced is necessary to minimise problems due to unequal feed
intake.
Popof-M.
| 1979
| Uses of
biochemical tests on urine & blood in diseases of sheep. II.
Analytical study in ketosis, hypocalcaemia, enterotoxaemia &
urolithiasis.
| Point Veterinaire; vol
9; no 43; pp 65-70; ISSN: 0335-4997.
| 44, Rue de
Cronstadt, 750015
Paris
,
France
.
| Symptoms
in 59 ewes with ketosis ranged from slight locomotor
disorder & withdrawal from the flock, through posterior paresis to coma.
Frank ketonuria with acid pH was pathognomonic.
All 15 ewes with acute hypocalcaemia were extremely depressed.
Most showed very alkaline urine & glycosuria.
Blood Ca was as low as 48mg/litre (100mg/litre is normal). Enterotoxaemia was
observed in 46 adult sheep & 77 lambs. Symptoms ranged from sudden tympanites,
through opisthotonos with pedalling movements, to
coma. The urine in this condition showed acid pH & the presence of glucose,
but ketones were usually absent. Hyperglycaemia was
common. Urolithiasis was observed in 4 rams, 5 ram lambs & 2 ewe
lambs. Urinary pH was neutral or alkaline.
Saba-N,
Cunningham-N-F.
| 1971
| Plasma
corticosteroid levels in ovine pregnancy toxaemia & hypocalcaemia.
| Research
in Veterinary Science; vol 12; no 5; pp 483-485;
ISSN: 0034-5288.
| Central Vet Lab, Weybridge,
Surrey
.
| Both
pregnancy toxaemia & clinical hypocalcaemia can cause sufficient
stress in ewes to raise plasma adrenal steroid levels.
Smith-F-G-Jr,
Alexander-D-P, Buckle-R-M, Britton-H-G, Nixon-D-A.
| 1972
| Parathyroid
hormone in foetal & adult sheep: the effect of hypocalcaemia.
| Journal of
Endocrinology; vol 53; no 3; pp 339-348; ISSN:
0022-0795.
| Dept Physiol, St Mary's Hospital Med Sch,
London
, W2.
| Radioimmunoassay
revealed parathyroid hormone (PTH) in the plasma of 2/5 foetuses, 3/5 ewes
& all 3 non-pregnant adults. Induction of hypocalcaemia by EDTA
infusion increased PTH concentration & urinary phosphate excretion in all 5
foetuses & non-pregnant adults. During induction of hypocalcaemia
plasma Ca was inversely related to PTH, except in ewes. The parathyroid
glands appear to be active from an early stage in foetal life & they
responded to changes in serum Ca.
Sweeney-H-J,
Cuddeford-D.
| 1987
| An
outbreak of hypocalcaemia in ewes associated with dietary
mismanagement.
| Veterinary
Record; vol 120; no 5; pp 114; ISSN: 0042-4900; 4
ref.
| Royal
(Dick) Sch Vet Studies, Easter Bush, Roslin,
Midlothian
,
UK
.
| 43/350
purebred Llyn ewes became comatose & 5
died within 12h. The ewes were within 2 weeks of lambing &
most carried twins. All but 2 of the remainder responded to injection of
Ca borogluconate (40 ml of 40%
solution i/v plus 40 ml s/c). The diet consisted of swedes
for 3h/d, hay & 0.3kg of a mixture of whole barley & fish-meal pellets. The
supplement was inadequately mixed & had a mean Ca & P content of 4.8
& 6.9g/kg DM, respectively. Serum Ca ranged from 0.74-1.18 mmol/litre
(normal 2.86-3.24), inorganic phosphate was correspondingly low, & Mg
normal. An energy deficit was indicated by elevated 3-hydroxybutyrate
(1.30-2.09 mmol/litre) representing a deficit of
3.5 MJ metabolisable
energy/d. Ca intake/ewe was 3.5g/d whereas 10.1g/d is recommended for a
60kg ewe carrying twins. Also contributory to the condition was the variation in
the Ca content of the concentrate.
Tindall-J-R.
| 1986
| Hypocalcaemia
in housed ewes.
| Veterinary
Record; vol 118; no 18; pp 518-519; ISSN: 0042-4900.
| Prospect
House, Church Brow, Clitheroe,
Lancs
,
UK
.
| Muscular incoordination
with a high incidence of prolapse of the uterus & intestine occurred in
40/800 intensively fed, housed ewes in late pregnancy. 12 ewes
died. Blood Ca was subnormal. When Dical was fed at
15g/ewe/d, the condition subsided, & blood Ca returned to normal. Analysis
of the feed showed that Ca & P levels in the previous diet were adequate but
Mg levels were high. It was concluded that the availability of dietary Ca was
reduced by Mg.
Vihan-V-S,
Rai-P.
| 1985
| Studies on
blood serum changes in experimental hypocalcaemia in sheep.
| Indian
Veterinary Journal; vol 62; no 7; pp 573-576; ISSN:
0019-6479; 11 ref.
| Dep Med, CSA Univ Agric Technol,
Mathura
Campus,
Uttar Pradesh
,
India
.
| Hypocalcaemia
induced in sheep by intravenous jugular infusion of 5% Na EDTA was
followed by a significant decrease in blood Ca from 12.3+/-0.47mg/100 ml to
3.5+/-0.29mg/100 ml in 2 h, significant decreases in inorganic P (from
6.1+/-0.35 to 2.1+/-0.06), total proteins (8.0+/-0.44 to 3.9+/-0.09g/100 ml)
albumin (5.1+/-0.28 to 2.5+/-0.12) & globulin (2.9+/-0.1-1.4+/-0.1g/100 ml)
& significant increase in serum aspartate aminotransferase
(from 40.7+/-4.34 to 75.3+/-4.06 units/ml). Glucose & Mg concentrations
were not affected.
Wilson-G-F.
| 2001
| Stimulation
of Ca absorption & reduction in susceptibility to fasting-induced hypocalcaemia
in pregnant ewes fed vegetable oil.
| New
Zealand Veterinary Journal; vol 49; no 3; pp
115-118; ISSN: 0048-0169; 14 ref.
|
Institute
of
Veterinary
, Animal &
Biomedical Sciences,
Massey
University
, Palmerston
North,
New Zealand
.
| This study
tested the hypothesis that susceptibility to fasting-induced hypocalcaemia
could be reduced by prior stimulation of the ability of late-pregnant ewes
to absorb Ca from the GIT (GIT) by feeding of vegetable oil supplement. The
supplement was expected to decrease the availability of the Ca supplied from a
pasture diet, & stimulate the animals' homeostatic system. Mature ewes
pregnant with twins (n=28) & grazing at pasture, were randomly allocated to
treated or control groups, 6 weeks prior to their expected date of parturition
(d0). Treated ewes (n=14) were drenched with 25 ml soyabean
oil twice/d for 3 weeks. Plasma Ca concentrations were determined on d0, 8
& immediately before & after a 20h fast that began on d21, which was
intended to simulate the reduced feed intakes that occur on the day of
parturition. An index of the ewes' ability to absorb Ca from the GIT was
obtained using orally dosed Sr as a tracer & the
extent of Ca mobilization from bone was assessed by measuring hydroxyproline
concentrations in plasma before fasting on d21. Plasma Ca concentrations were
significantly higher in treated than control ewes after fasting
(P<0.001). The Ca absorption index was also higher in treated than control ewes
at the end of the 3 week treatment period (P=0.014), but degree of bone
mobilization assessed by concentration of hydroxyproline
in plasma did not differ significantly between groups. Susceptibility of
late-pregnant ewes to fasting-induced hypocalcaemia was reduced using a soyabean
oil supplement. The inclusion of one or more dietary ingredients capable of
binding or forming complexes specifically with Ca in the diet of late pregnant
ruminants may provide a novel, practical method of reducing periparturient
hypocalcaemia.
Wilson-G-F,
Editor:
Enemark-J-M-D,
Thilsing-T,
Jorgensen-R-J.
| 2003
| Development
of a novel concept (Calcigard) for activation of Ca
absorption capacity & prevention
of milk fever.
| Proceedings of the Abildgaard
Symposium on hypocalcaemia,
acidosis & Ca homeostasis, 16-17 August 2001, The Royal Veterinary &
Agricultural University, Frederiksberg, Denmark; Acta
Veterinaria Scandinavica,
Supplementum; no supp. 97; pp 77-82; ISSN:
0065-1699; Publisher: The Danish Veterinary Association; Vanlose;
Denmark; 16 ref.
|
Institute
of
Veterinary
, Animal &
Biomedical Sciences,
Massey
University
, Palmerston
North,
New Zealand
.
| The
background to the development of a novel concept for the prepartal
activation of Ca absorption capacity as a means of preventing
parturient hypocalcaemia
& milk fever in grazing ruminants is described. It was hypothesised that
this objective could be achieved by decreasing the bio-availability of Ca from
pasture for a 3 week period. Soya bean oil was chosen as a supplement, from a
number of potential binding agents, to form poorly digestible Ca soaps in the
GIT. 28 mature twin-pregnant ewes
in late pregnancy were used as assay animals to test the hypothesis, & they
proved to be a sensitive experimental model for dairy cows. Following the
treatment period, overnight starvation was used to challenge Ca homeostasis. Ca
absorption capacity was assessed indirectly by measuring strontium
concentrations in plasma following oral dosing with strontium chloride. Strong
support for the hypothesis was obtained as the 14 Treated ewes
were protected from severe fasting-induced hypocalcaemia (P=0.002), & this
was associated with a greatly increased capacity of the ewes
to absorb Ca. The feeding strategy developed in this experiment led to the
production of a Calcigard concentrate supplement
which was subsequently shown to protect cows from hypocalcaemia & milk fever,
& stimulate production.