THE EFFECT OF DIETARY COBALT INTAKE ON THE PLASMA VITAMIN B₁₂ CONCENTRATION OF SHEEP

Abstract

Summary The plasma vitamin B 12 concentration of sheep progressively increased as the dietary cobalt level was raised from 0·04 parts per million to 0·34 parts per million. With rations containing more than 0·10 parts per million cobalt (8·1 μg. Co/day) plasma vitamin B 12 concentrations of sheep were more variable than those with lower cobalt intakes. This variability may have been due to variations in the rate of synthesis of cobalamins in the rumen. and hence the amount presented for absorption in the post‐ruminal alimentary tract. In two sheep fed a diet containing 0·04 parts per million cobalt, marked signs of cobalt deficiency appeared when the plasma vitamin B 12 concentration declined to 0·2 m. μg./ml. A plasma vitamin B 12 concentration of 0·2m. μg./ml., or less, also occurred in two sheep fed a diet containing 0·06 parts per million cobalt without the appearance of any other signs of a deficiency.