Significance of the Differences in Digestibility of Feeds by Cattle and Sheep

Published data which allow the comparison of the digestive powers of cattle and sheep were analyzed statistically. Comparisons were made for the digestibility of organic matter, crude protein, crude fiber, N-free extract, and ether extract, and the contents of total digestible nutrients in each of the three feed classes, dry roughages, silages, and concentrates. To make the comparisons fair, covariance adjustment for proximate composition was conducted. Specific differences in the digestibility of the organic matter, crude fiber, nitrogen-free extract, and ether extract, and in the total digestible nutrient content of dry roughages were found to be statistically significant. In the case of silages and concentrates, species differences were significant only for ether extract. The interaction, species-by-feeds, was significant for the digestibility of protein in dry roughages and the digestibility of ether extract in concentrates, indicating that the differences in the digestibility favor cattle with certain feeds and sheep with others. Other differences, although not significant, were large enough to suggest a trend. From the results, it was clear that greater accuracy will be attained if digestibility data to be used for cattle are obtained with cattle, and similarly for sheep.