Vitamin B₁₂ and cobalt in livers from grazing cobalt-deficient lambs and from others given Various Cobalt Supplements

Summary

Vitamin B₁₂ and cobalt concentrations were determined in the livers of 4 groups of lambs. Three groups were grazed on cobalt-deficient pastures. Of these groups one received no cobalt treatment and developed marked cobalt deficiency disease. Of the other two groups on cobalt-deficient pastures, one received oral doses of cobalt and the other cobaltic oxide pellets. The fourth group was grazed on cobalttopdressed pastures.

Vitamin B₁₂ concentrations in the livers of markedly cobalt-deficient lambs ranged from 0.026 to 0.097 μg/g of wet tissue, with a mean of 0.062 μg/g. Cobalt dosing and cobaltic oxide pellets increased liver vitamin B₁₂ concentrations about fourfold and sevenfold respectively. Vitamin B₁₂ concentrations in the livers of animals from cobalt-top-dressed pasture were of an order similar to those for lambs given cobaltic oxide pellets.

Effects of cobalt deficiency disease and of cobalt treatments on B₁₂ Co/total Co ratios are discussed.

From all the information available it is concluded that vitamin B₁₂ concentrations should provide a more sensitive indication of the presence or absence of cobalt deficiency disease than do cobalt concentrations. For sheep a value of 0.20 μg/g is suggested as an approximation to the minimal liver vitamin B₁₂ concentration (“critical level”) consistently associated with freedom from cobalt deficiency disease. Tentative vitamin B₁₂ diagnostic criteria are given.