by ionophores and was slightly greater (P < 0.05) for ionophores at 1.0 than at 0.5 mg kg-' of BW.Digestible organic matter intake with bermudagrass was slightly greater with ionophores at 1.0 than at 0.5 mg kg t of BW, but an opposite difference between ionophore levels occurred with bromegrass (ionophore level x forage source interaction; P < 0.07). The concentration of total volatile fatty acids in rumen fluid at 4 h post-feeding was lower (P < 0.05) for monensin than for lasalocid; the acetate/propionate ratio was decreased by ionophores and was lower for monensin than for lasalocid (P < 0.05). In exp. 3, lasalocid at 0.5 mg kg-'of BW did not affect intake or digestion or interact with supplemental corn (7.2 gkg-'of BW) or forage source. In conclusion, level of ionophore maximizing digestible organic matter intake may vary with characteristics of source of low-quality forage.However, when present, effects of ionophores on digestibility or energy intake may be relatively small.

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).

No abstract

~-Forty-two crossbred lambs (33.4 kg initial body weight; twenty-four wethers and eighteen ewes) were used in a 42 d experiment with a 2 x 3 factorial treatment arrangement to determine effects of forage level and source on splanchnic tissue mass. Diets were 250 and 750 g/kg of chopped lucerne (Medicago sativa) (A), ryegrass (Lolium multzjlovumFwheat ( Tviticum aestivum) (RW) or bermudagrass (Cynodon dactylon) (B) hay, with the remainder being maize-based concentrate. Five lambs per treatment were slaughtered at the end of the experiment and measurements made of internal organs and contents of the gastrointestinal tract (GIT). Digestible organic matter intake (DOMI) on the In summary, differences in properties of forage A and the grasses at 250 g/kg diet may have influenced GIT mass independent of energy intake and digesta mass. Conversely, with 750 g dietary forage/kg, higher digesta mass for diet B than diet RW appeared responsible for high reticulo-rumen mass relative to DOMI. Greater digesta mass for 750 than 250 g forage/kg may have elevated intestinal tissue mass/DOMl with diets A and B but not with diet RW, for which NDF digestibility was highest.

Effects of animal gender and age, use of a growth stimulant, and supplementation with grain alone or grain plus other substances on ADG by growing beef cattle grazing bermudagrass paddocks with sod-seeded rye, wheat, and ryegrass were determined. Two grazing experiments (Exp. 1: late winter through mid-spring; Exp. 2: late spring through mid-summer) were conducted. Experiment 1 used 96, 12- to 13-mo-old Simmental-cross calves (heifers, 240 kg; steers, 272 kg), half of which were implanted with zeranol. Within each implant treatment, cattle received no supplement or .5% BW (DM) of ground corn alone or plus a mix of protein meals, zinc sulfate, thiamin-HCl, or salt. Daily gain was higher (P less than .05) with than without supplementation and was similar (P greater than .10) among supplement treatments. In Exp. 2, 96 crossbred beef steers, approximately 7 (230 kg) or 15 mo old (250 kg), were not supplemented (control) or received .5% BW (DM) of ground corn on d 1 to 84 (C-C), corn plus a protein meal mix on d 1 to 84 (CP-CP), corn on d 43 to 84 (O-C), corn plus the protein meal mix on d 43 to 84 (O-CP), or corn on d 1 to 42 and corn plus the protein meal mix on d 43 to 84 (C-CP). Daily gain on d 1 to 84 was affected (P less than .05) by supplement, age, implant, and the supplement x implant interaction (nonimplanted: .37, .56, .68, .40, .49, and .49; implanted: .37, .62, .54, .49, .70, and .71 kg for control, C-C, CP-CP, O-C, O-CP, and C-CP, respectively).