Changes in serum concentration of methylmalonic acid and vitamin B12 in cobalt-supplemented ewes and their lambs on two cobalt deficient properties

Tini M. Gruner, Southern Cross University
J R. Sedcole, Lincoln University, Canterbury
J M. Furlong, Lincoln University, Canterbury
N D. Grace
Stephen D. Williams, Southern Cross University
G Sinclair
A R. Sykes, Southern Cross University

Abstract

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

supplementation.

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

B12 supplementation.

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.