Effect of Intake on Digestive Efficiency

Abstract

Digestive efficiency predicted from measurements of nonproducing ruminant animals overestimate by at least 12% the digestibility of the same ration fed to the lactating dairy cow. Additional data demonstrate that much of the reduced digestive efficiency of the lactating dairy cow is correlated with the amount of diet consumed per unit of time. Limited data suggest that digestibility of all fractions of the diet are not depressed equally. Digestibility of cellulose and hemicellulose is depressed 2 to 3 times digestibility of soluble carbohydrate at high intake. Most of the systematic bias in the present system of feed evaluation for lactating dairy cows can be removed by adjusting for the effect of intake on digestive efficiency. More research on factors affecting digestive efficiency of the structural carbohydrate of plant cell walls is needed to develop a precise method for predicting total ration nutritive value of diets fed to the high producing dairy cow.