The effect of pregnancy in heifers on voluntary intake, total rumen contents, digestibility and rate of passage

Abstract

In two experiments using twin heifers with one of each pair pregnant, the effect of advanced pregnancy on the voluntary food intake, dry matter digestibility and rate of passage of food residues, was studied. In the first experiment sorghum silage was fed ad lib. In the second experiment lucerne chaff was fed at ad lib. and restricted levels and, in addition to the measurements listed above, the quantity of reticulo-rumen contents was determined in each animal. In both experiments each of the pregnant heifers ate less than their non-pregnant CO-twins, and, on analysis of all the data on ad lib. feeding, the differences were significant (P<0.01). The mean coefficients of dry matter digestibility for the pregnant heifers were significantly (P<0.01) less than those for non-pregnant heifers. This caused a significantly (P<0.01) lower intake of digestible dry matter by the pregnant heifers. Measurements of the contents of the reticulo-rumen and the rate of passage of food particles gave inconclusive results. These experiments demonstrated that there was a depression of voluntary intake in late pregnancy the cause of which is not known. This would be nutritionally significant only when the quality and voluntary intake of food were marginal.