The efficacy of supplying supplemental cobalt, selenium and vitamin B 12 via the oral drench route in sheep

Cobalt and selenium are essential trace elements required for ruminants. There are many different methods of supplementation available to sheep including boluses, in feed, free access minerals, pasture dressing and oral drenches. Recent changes in European legislation have resulted in a reduction in the maximum permitted level (MPL) of cobalt to be included in ruminant diets from 2 mg/kg at 88% DM to 1 mg/kg at 88% DM with a suggested supplementary rate of 0.3 mg Co/kg at 88% DM. This study aimed to determine the efficacy of cobalt plus/minus vitamin B₁₂ and selenium supplementation from oral drenching over a 13 day time period. Seven groups of grass silage fed Suffolk cross mule lambs (n=56) were randomly allocated to one of 7 treatments, a 5 ml oral drench containing 700, 2300, 12000 mg Co/l, with or without 2300 mg vitamin B₁₂/l in a factoral design, with an additional control group which received no drench. All drenches also contained selenium at 625 mg/l. Lambs were weighed on days 0 and 13. The lambs were sampled by jugular venepuncture on days 0, 1, 2, 3, 4, 5, 6, 7, 9, 11 and 13, with samples analysed for plasma selenium and cobalt by ICP-MS, erythrocyte glutathione peroxidase by colourimetric assay and vitamin B₁₂ by immunoassay. The results showed that cobalt via a drench was able to raise plasma cobalt in a dose dependent manner, with each dose level significantly higher than the previous level at all post drenching time points (P