The effect of level of environment on sex differences in pre-weaning growth rate in beef cattle

Abstract

SUMMARYUsing pre-weaning records of 3822 calves from 11 Victorian herds, mean male and female growth rates and corresponding sex differences were calculated for each dam age and herd-year class. From these means simple regression equations relating sex differences and growth rates were calculated. There was a close similarity between equations based on dam age means and those based on herd-year means while correlations between sex differences and male growth rates were high.These results showed that sex differences and female growth rates could be predicted reliably from the level of environment as measured by male growth rate. Sex differences predicted by these regression relationships differed markedly from those predicted by the simple multiplicative and simple additive models generally used in adjusting for sex differences in selection.The results also suggested that other differences such as breed differences may be predictable in the same way and that such differences are determined primarily by the level of environment per se rather than differences in the nature of the components contributing to that level.

Erratum to: Genetics of heifer performance in 'wet' and 'dry' seasons and their relationships with steer performance in two tropical beef genotypes

“…vary between environments (Hopkins 1977;Herring et al 2005). Also, B. indicus are widely thought to have a greater ability to utilise, partition or acquire feed on low quality or restricted diets, and a lesser ability on high energy or ad libitum diets (Moore et al 1975;Frisch and Vercoe 1980;Turner 1980;Ferrell et al 2005;Forbes 2005).…”