DIGESTION, FEED-INTAKE, AND LIVE WEIGHT-GAIN BY CATTLE CONSUMING BERMUDAGRASS AND SUPPLEMENTED WITH DIFFERENT GRAINS

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 com (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).