A Study of the Function of Cobalt in the Nutrition of Sheep I

T HE essentiality of cobalt in the diet of sheep has been proved by Underwood and Filmer (I93~), Marston et al. (I938), Bowstead and Sackville (i939), Bowstead et el. (I94z), Pope et al. (1947), and by Keener et al. (I948). Numerous workers in this country and abroad also have identified cobalt deficiency m cattle. Little progress appears to have been made, however, in determining the function of cobalt in the diet of ruminants until Rickes et al. (1948) isolated vitamin B12 and found that it was a cobalt complex. Although the role of cobalt in vitamin B~ synthesis may not be the one which is involved in cobalt deficiency, this discovery apparently marks an important advance in determining the overall function of cobalt in animal nutrition. It is believed generally that cobalt has an essential function in the product/on of some sort of appetite-stimulating factor by the flora of the rumen. The principal reasons for this are that cobalt deficiency has been found only in ruminants and that, as reported by McCance and Widdowson (I944), injected cobalt, unlike that administered orally, has not been effective in relieving the deficiency. Ray et al. (t947) reported that the concentrations of both nicotinic acid and the vitamin B6 group were lower in the blood of cobalt deficient sheep than in that of normal sheep. There was a suggestion of a similar lowering of riboflavin, but the levels of folic acid and pantothenic acid were not affected. Ray et al. (i948) reported that the oral administration of cobalt salts to cobalt deficient sheep brought about a rapid increase in appetite and body weight, but that the injection of cobalt salts gave a slower response. Thiamin injections also were reported to have brought about a definite improvement in rate of body gain and in appetite. If cobalt deficiency is to be eliminated completely as a problem in the