The requirement for cobalt of sheep grazed on cobalt-deficient pastures

Abstract

Experimental proof is presented that cobalt injected intravenously or into the abomasum at the rate of 1 mg/day is without any measurable effect on the cobalt deficiency syndrome in sheep. Similarly, depot therapy with colloidal cobalt is of no benefit. It is confirmed that, to be effective, cobalt supplements must be introduced frequently into the rumen, by mouth or by direct injection; although administration by other routes leads to a considerable accumulation of cobalt in the tissues this does not reach the rumen in effective amounts, if at all. For sheep grazing grossly cobalt-deficient pastures the total intake of cobalt necessary to ensure optimum growth and haemoglobin production was found to be equivalent to almost precisely 0.08 mg/day when supplementary cobalt was provided three times each week; in growing lambs the requirement was greater. Analytical evidence is presented in support and the findings are discussed in relation to certain conclusions arrived at by others.