Performance of growing cattle grazing moderate quality legume–grass temperate pastures when offered varying forage allowance with or without grain supplementation

This research evaluated the effect of supplementation with cracked corn grain (0 or 1% of liveweight) on the performance of Hereford steers grazing a mixed pasture of legume and grass at 3 forage allowances (3, 6 or 9 kg DM/100 kg liveweight). The experiments were conducted in West Uruguay over 2 consecutive summers, with 72 Hereford steers (282 ± 15.3 kg; n = 36/year) randomly allocated to 1 of the 6 treatments in a factorial arrangement. Cattle were supplemented in individual pens and weighed every 14 days. Grain intake did not differ (P>0.05) between forage allowances. Both supplementing and increasing forage allowance reduced (P<0.01) forage utilisation. Year effect was significant (P<0.01) for liveweight gain and grain intake, but neither the 2- nor the 3-way interaction of year with forage allowance or supplementation was significant (P>0.05). Increasing forage allowance only improved (P<0.01) liveweight gain of non-supplemented cattle (0.299, 0.483, 0.667 kg/day for forage allowance of 3, 6 or 9%, respectively). Hence, response to supplementation decreased with forage allowance, increasing the grain (kg)/gain (kg) conversion ratio. These results provide a quantitative basis on which to decide upon the best feeding management option for summer.