Selection for Growth and Feed Efficiency : The Australian Experience

Profitability in beef production is influenced by a number of traits, including growth and feed efficiency. This paper reviews key Australian selection experiments on growth and feed efficiency, and the beef industry adoption of selection for these traits. Response to selection for growth has been demonstrated by a divergent selection experiment. Five generations of divergent selection for growth resulted in 19% divergence in yearling weight and 18% in weaning weight, and no effect on carcass composition at maturity. Selection for growth in industry herds started in the 1980s, with a steady rate of genetic gain being achieved. In Australian Angus seedstock population, for example, the annual genetic gain in estimated breeding values (EBVs) for 400-day weight was 0.15 standard deviation units from 1998 to 2003. As with growth, selection for feed efficiency has been demonstrated by a divergent selection experiment for residual feed intake (RFI). Two generations of selection produced an annual divergence of 0.25kg/day of 10MJ ME feed with no correlated responses in growth and meat quality of young cattle. Cow weight and reproduction were not affected, however, High RFI cows tended to have higher subcutaneous fat depth relative to Low RFI cows. Testing for RFI in industry herds started in 1996, and from 2002, RFI EBVs are provided for seedstock Angus and Hereford cattle. Several studies have indicated substantial economic benefit from selection for low RFI, however the initial high cost of testing to identify superior animals is an impediment to industry adoption