Crude Protein in Rumen Contents and in Forage

Rumen-fistulated steers consistently selected a diet higher in crude protein than hand-clipped samples of the major available perennial grasses. The excess of rumen protein over grass protein depended on the availability of higher-protein shrubs and annual forbs that supplemented the perennial grasses, and on selection of high-protein parts of the grasses. Since the abundance of these high-protein forages varied greatly with time, the protein content of grass clippings did not reliably indicate the protein level in the steer's diet.