Changes in serum concentration of methylmalonic acid and vitamin B12 in cobalt-supplemented ewes and their lambs on two cobalt deficient properties
AIM: To determine concurrent changes in serum methylmalonic
acid (MMA) and vitamin B12 concentrations of ewes and
their lambs on cobalt-defi cient properties, subsequent to cobalt
METHODS: Three experiments were carried out on two farms.
Groups of ewes (n=25–50) were either supplemented with cobalt
bullets during late pregnancy, 23–47 days before the mean
lambing date, or left unsupplemented. In two experiments,
lambs from within each group were supplemented directly by
vitamin B12 injection at 3-weekly intervals from birth, and in
the third experiment by injection with micro-encapsulated vitamin
B12 at tailing and 3 months later. Pasture samples were
obtained for analysis of cobalt content at each sampling time.
Blood samples were obtained and liveweight recorded from ewes
and lambs at approximately monthly intervals. On one farm
(two experiments), liver and milk samples were obtained from
ewes and liver samples from lambs.
RESULTS: Serum vitamin B12 concentrations in unsupplemented
ewes fell below 250 pmol/L during early lactation in
all experiments and mean concentrations as low as 100 pmol/L
were recorded. MMA concentration was maintained below
2 μmol/L in serum from supplemented ewes but increased to
mean concentrations ranging from 7 to14 μmol/L at the nadir
of serum vitamin B12 concentration during peak lactation.
A signifi cant liveweight response to supplementation was recorded
in ewes on one property, and the vitamin B12 concentration
in the ewes’ milk and in the livers of their lambs more
than doubled. No liveweight-gain response to supplementation
was observed in lambs on this property. Mean serum MMA
concentrations in lambs ranged from <2 in>supplemented, to
19.2 μmol/L in unsupplemented lambs, and the latter had concurrent
serum vitamin B12 concentrations of >300 pmol/L. Pasture
cobalt concentration was lowest at 0.04–0.09 μg/kg dry
matter (DM) on the property on which responses in lambs occurred
but considerably higher (>0.09 μg/kg DM) on the property
on which responses in ewes occurred.
On the second property, serum vitamin B12 concentrations in
lambs at tailing were extremely low (100 pmol/L), irrespective
of supplementation of dams with cobalt. Mean serum MMA
concentration was increased to 20 and 42 μmol/L in lambs
from supplemented and non-supplemented ewes, respectively.
Weight-gain response to direct supplementation of lambs with
vitamin B12 occurred during suckling in the latter, but not
the former. Lambs from ewes supplemented with vitamin B12
showed a much bigger increase in serum vitamin B12 concentrations
a month after supplementation than did lambs from
unsupplemented ewes (+1,400 pmol/L vs +650 pmol/L).
CONCLUSIONS: Serum MMA concentration gave a more precise
indication of responsiveness to vitamin B12 or cobalt supplementation
than serum vitamin B12 concentrations in ewes
and lambs. Neither very low serum vitamin B12 nor elevated
MMA concentrations were necessarily indicative of responsiveness
to supplementation in suckling lambs, but the latter gave
an early indication of impending responsiveness. Supplementation
of the ewe with a cobalt bullet appeared to protect the
growth performance of the lamb for 90 days and infl uence the
subsequent serum vitamin B12 response in the lamb to vitamin
CLINICAL SIGNIFICANCE: Supplementing ewes with cobalt
bullets in late pregnancy can improve the vitamin B12 status of
their lambs, and modify their response to vitamin B12 supplementation.
Gruner, TM, Sedcole, JR, Furlong, JM, Grace, ND, Williams, SD, Sinclair, G & Sykes, AR 2004, 'Changes in serum concentration of methylmalonic acid and vitamin B12 in cobalt-supplemented ewes and their lambs on two cobalt deficient properties', New Zealand Veterinary Journal, vol. 52, no. 3, pp. 117-128.
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