Responses to grain:sunflower meal supplements by weaned calves grazing mature pasture or eating hay in pens

Abstract

In southern Australia, winter-born calves may not be at marketable weights until 18 months of age and can thus compete with their dams and the next crop of calves for the pasture resource. We investigated supplementary feeding options to improve calf liveweight gains and overcome this problem. Weaned beef calves confined to feedlots for 70 days were fed different ratios (1 : 1 up to 1 : 4) of sunflower meal to oat grain (Experiment 1) or barley grain (Experiment 2) at levels of 3–6 kg air-dry/day, plus either oaten hay (Expt. 1) or pasture hay (Expt. 2) fed ad libitum. Liveweight gains at 3 kg supplement/day were ~1.2 kg/day at all ratios and were slightly higher at the higher feeding levels. The intake of hay varied inversely with the amount of supplement fed and substitution rates were 0.49 with oaten hay and 0.47 with pasture hay. Total DM intakes did not decline in Experiment 1 as supplement intake increased and increased in Experiment 2 with increasing supplement intake. A separate group of calves that had been grazing mature pasture while their cohorts were in the feedlot showed good compensatory growth when transferred to good pasture, whereas calves coming out of the feedlot onto the same pasture initially lost weight before regaining weight. This suggests that such feedlot-reared calves should be sold direct from the feedlot. In a third experiment, over 2 years, weaned calves grazed mature summer pasture for 81 days and were fed 0, 1, 2, 3 or 5 kg/day of a 1 : 2 ratio of sunflower meal : hammer-milled oat grain. Weight gains were less than in Experiments 1 and 2 and responses of gain to supplement intake were curvilinear. Gains did not exceed 0.75 kg/day and peaked at supplement intakes of 4.3 and 2.8 kg DM/day in years 1 and 2, respectively. Liveweight gains/kg supplement consumed were similar to those in previous studies. A preliminary assessment of supplement costs and the economic value of liveweight gain showed a curvilinear response to supplement intake and suggested that the greatest economic return resulted from an intake of 1.9–2.4 kg/day of the supplement, lower than the supplement intakes for maximum liveweight gain.