Digestion, feed intake, and live weight gain by cattle consuming bermudagrass and supplemented with different grains.

Abstract

The objectives of this study were to determine whether type of supplemental cereal grain, with a relatively high level of supplementation, affects feed intake, characteristics of digestion, and live weight gain by cattle consuming bermudagrass (BER). In Exp. 1, five beef steers (423 +/- 22 kg average BW) with cannulas in the rumen and duodenum were used in a Latin square design experiment. Steers consumed BER hay (1.5% BW; 10.1% CP, 75% NDF, and 6% ADL) alone (Control) or with approximately .7% BW (DM) of ground corn (GC), whole corn (WC), ground sorghum grain (SG), or ground wheat (W). At 8 h after supplementation, ruminal pH was lower for W than for Control, WC, and SG (P < .05). True ruminal OM digestion was lowest for SG and highest for W (P < .05; 49.4, 50.7, 51.0, 42.0, and 57.3% for Control, GC, WC, SG, and W, respectively). In Exp. 2, five Holstein steer calves (187 +/- 9 kg average BW) were used in a Latin square design. Bermudagrass hay (9.7% CP, 72% NDF, and 6% ADL) was consumed ad libitum alone (Control) or with approximately 1% BW of grain (same as in Exp. 1). Digestible OM intake was similar among grain treatments. In Exp. 3, 96 crossbred beef steers (256 +/- 2 kg initial BW) grazed BER (clipped forage samples: 13 to 16% CP, 68 to 73% NDF, and 4 to 5% ADL) for 85 d and received the same grain treatments as in Exp. 2 plus a barley (B) treatment. Live weight gain was .47, .84, .80, .68, .81, and .51 kg/d for Control, GC, WC, B, SG, and W, respectively (SE = .028). In conclusion, when growing cattle grazing BER were supplemented once daily with grain at approximately 1.0% BW, grain that degraded in the rumen slowly (GC, WC, and SG) resulted in live weight gain greater than that resulting from grain that degraded rapidly (B and W).