Variations in the Amount and Relative Distribution of Vitamin B12 and its Analog in the Bovine Rumen

Abstract

The effects of various factors upon the amount and nature of vitamin B12-active material in the rumen of dairy heifers were studied. Animals fed silage contained a significantly higher (1.4× to 2.7×) concentration of vitamin B12 activity in their rumen contents than those fed chopped or pelleted hay; heifers fed hay-grain contained less of the vitamin. The dorsal rumen possessed more vitamin B12 activity than the ventral rumen or reticulum on the wet but not dry matter basis. Depending upon the ration, sampling position, and experiment, there was a tendency for the vitamin B12 concentration to increase up to a point with time of collection of sample after feeding. Amounts of the vitamin in rumen contents were 12 to 663 times those available from the food. Correlation coefficients were calculated between vitamin B12 concentrations and other rumen constituents. The highest of those tested was between vitamin B12 activity and total bacterial counts. Estimates of the approximate relative distribution of vitamin B12 and its analogs in rumen contents indicated little variation of most of them with ration. Fifteen to 20% consisted of vitamin B12 itself. The analog composition represents the net contribution of a number of various microorganisms. © 1971, American Dairy Science Association. All rights reserved.