COBALT - VITAMIN-B-12 DEFICIENCY AND THE ACTIVITY OF METHYLMALONYL COA MUTASE AND METHIONINE SYNTHASE IN CATTLE

Cobalt deficiency was induced in cattle by feeding two groups of anima ls either a basal diet that was very low in Co (12.9-17.6 mu g Co per kg), or the same diet supplemented with cobalt, for a total of 64 week s. Vitamin B-12 deficiency was induced, as judged by hepatic concentra tions of vitamin B-12 and plasma concentrations of MMA. However the ac tivity of holo-methylmalonyl CoA mutase was significantly reduced only in brain. This was reflected in very minor alterations in the tissue concentrations of branched chain- and odd numbered-fatty acids. The ac tivity of holo-methionine synthase was significantly reduced in liver and brain, but there were no consequent alterations in the concentrati ons of phosphatidyl choline and phosphatidyl ethanolamine. This study confirms that cattle are less susceptible to the effects of cobalt def iciency than sheep, and concludes that prolonged cobalt deficiency had little significant effect on tissue metabolism.