The vitamin B₁₂ and Se status of lambs during their transition from milk-fed monogastric to grazing herbivore

Abstract

AIM: To estimate how the lamb’s transition from a monogastric at birth to a grazing ruminant at weaning affects its dietary intake of trace nutrients from milk and pasture, and to determine whether its vitamin B₁₂ and Se status changes during that period.

METHODS: We reviewed published reports of field trials in New Zealand where flocks were managed on mixed sward pastures without additional supplements. Information on intakes of milk and pasture was drawn from studies of suckling lambs grazing with ewes for up to 20 weeks. We calculated the quantities of vitamin B₁₂, Co and Se ingested and absorbed by lambs between birth and weaning. Trace nutrient status was based on concentrations of vitamin B₁₂ in serum and Se in blood. Six studies met our inclusion criteria regarding age of lambs, supplementation and sampling frequency. In each, blood had been collected at regular intervals from birth to weaning. Changes over time in concentrations of vitamin B₁₂ and Se were analysed using regression procedures.

RESULTS: Estimated Se intake increased from approximately 5 µg/day near birth to 25 µg/day near weaning, but Se absorbed was less variable, being approximately 10 µg/day. Estimated vitamin B₁₂ intake near birth was approximately 8 µg/day and increased to 90 µg/day by weaning, with the amount being absorbed increasing from 0.8 to 9 µg/day. Concentrations of trace elements in unsupplemented lambs among the six studies varied from deficient to adequate. Linear regressions indicated that there was little change in concentrations of vitamin B₁₂ and Se between birth and weaning in four studies (p>0.05), and mean concentrations measured at docking did not differ from those at weaning in four studies where this could be assessed (p>0.1).

CONCLUSIONS AND CLINICAL RELEVANCE: From newborn to weaned, a lamb’s physiology develops from monogastric to ruminant. The change in diet from milk to pasture presents markedly different chemical forms and concentrations of some trace nutrients. Despite this, the vitamin B₁₂ and Se status of the unsupplemented lambs in these studies changed little during their transition period. This finding supports early monitoring of lambs’ trace element status. If a trace element deficiency is detected in lambs at or before docking, then administering supplements may be appropriate. If status is found to be adequate, then it will likely remain so until weaning, at which time the animals’ trace element status should be re-evaluated.

KEY WORDS:

• Lambs
• selenium
• vitamin B₁₂
• intake
• absorption

Acknowledgements

We thank AgResearch Flock House for providing animals and facilities over many years, and farm manager John Parr, his shepherds and our research assistants for their flexible and cooperative management of these flocks.

ORCID

SO Knowles http://orcid.org/0000-0003-3482-5513

ND Grace http://orcid.org/0000-0001-8532-4378