Synthesis of Certain B-Vitamins in the Cobalt Deficient Sheep, with Special Reference to Vitamin B12

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Abstract
Microbiological assays with Lactobacillus lcichmannii for the vitamin B12 activity of the blood, livers, and rumen ingesta of cobalt-deficient sheep, cobalt-fed, full-fed sheep, and cobaltfed, limited-fed sheep have been presented. The blood of sheep early in cobalt deficiency contained only about one-fifth the vitamin B12 activity of the blood from cobalt-fed, full-fed sheep. Liver storage of vitamin B12 was very low in the cobalt-deficient sheep; about 30 times more “true” vitamin B12 activity was present in the livers of cobalt-fed animals. The alkali stable vitamin B12 activity of liver seemed to be higher for the deficient sheep and the cobalt-fed, limited-fed sheep than for the cobalt-fed, full-fed sheep. Rumen synthesis of vitamin B12 in the cobalt-deficient animals was about one-fifteenth of that encountered in the sheep given supplemental cobalt. Microbiological assays indicated that the rumen synthesis of nicotinic acid and riboflavin was essentially the same per gram of dry rumen material in deficient and cobalt-fed animals.