A comparison of the vitamin B12and cobalt contents of livers from normal lambs, cobalt-dosed lambs, and others with a recent history of mild cobalt deficiency disease

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Abstract
Vitamin B12 and cobalt concentrations were determined in the livers of 3 groups of lambs. One group, not given supplementary cobalt, was grazed on cobalt-sufficient pasture. A second group was dosed at the rate of 7 mg Co a lamb a week and grazed on pasture that had remained generally low in cobalt until about 2 months before the end of the trial. The third group was given no supplementary cobalt, grazed the same pasture as the second group and showed evidence of mild cobalt deficiency disease followed by a recovery within the last 2 mon ths of the trial. The mean vitamin B12 value for livers from unsupplemented lambs on cobalt-sufficient pasture was 0.65 εg / g of wet tissue. Cobalt dosing approximately doubled the mean vitamin B12 concentration in livers from lambs grazing pasture previously low in cobalt to a level approaching that for unsupplemented lambs on cobalt-sufficient pasture. The mean vitamin B12 value for livers from the group with a previous history of cobalt deficiency was 0.31 εg / g. Consideration of all the results suggests that cobalt deficiency in individual lambs is not likely to be associated with liver vitamin B12 concentrations ranging upward from about 0.30 εg / g, but concentrations of the order of 0.20 to 0.30 εg / g could be consistent with a recent history of mild cobalt deficiency. Most (in some cases virtually all) of the cobalt in the livers of lambs on cobalt-sufficient pasture which had not received supplementary cobalt was in the form of vitamin B12. By contrast most of the cobalt in the livers of cobalt-dosed lambs tended to be in some form other than vitamin B12. There was some indication that cobalt deficiency had resulted in a greater reduction of vitamin B12 cobalt than of non-vitamin B12 cobalt.