Nutritional options and implications for maximum growth rate of steers

Abstract

Estimates of age and weight at mature size are required for the development of decision-support and mathematical models to describe beef growth. Interim results from an experiment designed to quantify the liveweight gain of steers from weaning to mature size are reported in this paper. Three groups of 28 steers have been fed for 2 years from weaning (8 months) to 32 months of age on the following treatments: resident, ryegrass-white clover based pasture (R); a high quality pasture option based on annual ryegrass in winter and spring, and red clover and lotus in summer and autumn (HQ); and a 70% maize grain : 30% silage diet offered under feedlot conditions (F). Average daily gains from weaning to 30 months of age and liveweight at 30 months were 0.69 kg/hd/day, and 709 kg, 0.78 kgfhdlday and 772 kg, and 0.91 kglbdlday and 858 kg for R, HQ and F treatments, respectively. Feedlot steers had a greater fat depth over the 12113th rib than either of the pasture fed treatments, when measured at the same age. In addition, both pasture groups have shown seasonality in liveweight gain, with periods of low liveweight gain in late autumn and winter of the second and third years. Results are discussed in relation to the nutritional contrasts between treatments. Keywords: feedlot, cattl.e, liveweight gain, potential growth