Effect of Intake on Chewing Activity of Steers

Abstract

To determine the effect of intake on the roughage index of a diet, six mature steers averaging 503kg were fed a diet containing 90% corn silage and 10% grain mix at 87% (diet 1), 122% (diet 2), and 165% (diet 3) of maintenance net energy milk in a replicated 3×3 Latin square change-over experiment with 2-wk periods. The steers were accustomed to the diets for 4 wk prior to initiation of the experiment; the last 2 wk were used to determine maximum intake, approximately 2.4% of body weight. Steers were fed once daily at 0830h, daily feed intake was measured, and chewing activity was monitored the last 48h of each period. Intakes were 7.4, 10.4, and 12.2kg for the three diets, with corresponding total chewing times of 476, 628, and 706min. Roughage indexes in minutes of chewing time per kilogram of dry matter eaten in increasing intakes were 67.5, 62.8, and 57.1. Intake did influence roughage indexes with indexes decreasing linearly as intake increased. To adjust roughage indexes to intake, the following regression equation was used: Roughage index equals (130 plus 47.22 times kg intake) quantity divided by kg intake.