Recent advances in nutrition for improving liveweight gain

Abstract

The beef industry faces on-going economic challenges with returns from cattle often not keeping pace with the increasing costs of production. Increases in the growth rate of cattle can lead to both improved gross margins, especially when associated with shifting the time of sale to one of price premium, and higher product quality, e.g., better compliance with Meat Standards Australia
{MSA). In terms of nutritional strategies for increasing growth rates, all rely on improving the feed base with options around pasture improvement and supplementation being most practical. Recent research in this field includes defining the growth response relationships to major supplement types for young (weaners; <12 months) and older, finishing cattle on low quality tropical forages and defining the most appropriate phase of the growth path, from a cost-efficiency viewpoint, in which to undertake such nutritional interventions. Responses by both young and older steers were higher with protein meals compared with energy sources (e.g., grains and molasses mixes) at lower intakes (up to 1%W/day) but were similar at higher intakes, and were higher for older compared with younger steers overall. Identifying novel, low cost protein sources remains a priority for the north Australia beef industry and will probably require the source being grown on-property. The growth path can be manipulated either pre- or post-weaning. Studies from NSW indicate that restricted pre­ natal and pre-weaning nutrition reduces calf weight at weaning but does not affect post-weaning growth rate on pasture, though age to finishing is extended. In a current grazing study in north Queensland the cost of supplementation of steers to a similar weight at the end of the second dry season post-weaning {24 months of age) was $60 more when a high-input molasses-based supplement was fed in 2 dry seasons compared to just the second one. The alternative of finishing steers on improved leucaena/grass pasture reduced the age of slaughter by 3 months. The need is for these studies to be more widely tested across seasons and to include a genotype overlay t exploit genotype x nutrition interactions. There is potential to improve growth rate in the future by applying new techniques now available, for instance molecular-based methods to understand and potentially manipulate the rumen microbial ecosystem and produce more microbial protein, or to examine and target by nutritional manipulation the expression of genes likely to enhance ruminant production.