Cobalt-vitamin B12 deficiency and the activity of methylmalonyl CoA mutase and methionine synthase in cattle.

Cobalt deficiency was induced in cattle by feeding two groups of animals either a basal diet that was very low in Co (12.9-17.6 micrograms Co per kg), or the same diet supplemented with cobalt, for a total of 64 weeks. Vitamin B12 deficiency was induced, as judged by hepatic concentrations of vitamin B12 and plasma concentrations of MMA. However, the activity 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 activity of holo-methionine synthase was significantly reduced in liver and brain, but there were no consequent alterations in the concentrations of phosphatidyl choline and phosphatidyl ethanolamine. This study confirms that cattle are less susceptible to the effects of cobalt deficiency than sheep, and concludes that prolonged cobalt deficiency had little significant effect on tissue metabolism.