PERFORMANCE OF CATTLE OFFERED WHOLE-CROP BARLEY OR WHEAT SILAGE

Factors affecting the nutritive value of whole-crop cereal silage for beef cattle were examined. In Experiment 1, finishing steers offered barley silage, harvested at the milky (262 g dry matter (DM)/kg) or mealy (347 g DM/kg) stages of grain ripeness, for 95 days, had carcass gains of 292 and 442 (s.e. 33.2) g/day, respectively. Animals offered no supplement, 3 kg rolled barley, 3 kg of a barley plus soyabean meal mixture (154 g crude protein (CP)/kg DM) or 1 kg soyabean meal (470 g CP/kg DM) per head daily had carcass gains of 173, 442, 529 and 324 (s.e. 46.9) g/day, respectively. In Experiment 2, untreated (340 g DM/kg) or urea (19 kg/t DM) treated barley silage, supplemented with 2.9 kg concentrates per head daily, supported carcass gains of 629 and 634 (s.e. 20.5) g/day, respectively, in heifers during a 101-day finishing period. In Experiment 3, finishing heifers offered barley silages, made with no additive, urea (34 kg/t DM) or urea (30 kg/t DM) plus NaOH (21 kg/t DM) had carcass gains of 374, 477 and 534 (s.e. 23.0) g/day, respectively, over an 84-day experimental period. Supplementation with 2 kg concentrates per head daily increased mean carcass gain from 355 to 568 (s.e. 18.8) g/day. In Experiment 4, whole-crop wheat silage made without additive (431 g DM/kg; pH 4.1), with 56 kg urea/t DM (pH 5.6) or 111 kg urea/t DM (pH 7.6), and grass silage (218 g DM/kg; pH 4.1), all supplemented with 2 kg barley per head daily, supported liveweight gains in young beef heifers, over 112 days, of 645, 509, 362 and 719 (s.e. 34.7) g/day, respectively. It is concluded that (1) the carcass weight gain of cattle offered whole-crop barley silage was higher when harvesting was later, when the DM concentration of the silage was high (greater than or equal to 460 g/kg) and when the silage was treated with urea or urea plus NaOH, and (2) the intake and performance of cattle offered extensively fermented whole-crop wheat silage were reduced by excessive urea addition at ensiling.