Efficiency of food utilization in traditional and sex-controlled systems of beef production

Abstract

ABSTRACTAn empirically based equation for voluntary food intake, obtained from a multibreed cattle experiment, was used to develop formulae for evaluating the overall efficiency of food utilization of beef production n i a production unit consisting of a dam and her progeny. With these formulae the dependence of overall efficiency on degree of maturity at slaughter was studied, with reproductive rate, dam food costs, terminal sire size and number of calvings per dam allowed to vary.The formulae were used to study efficiency of food utilization in a traditional beef production system. Maximum efficiency values ranged from 2·3 to 3·5 g of lean tissue per MJ of metabolizable energy. These maximum values were affected to a small extent when progeny were slaughtered much earlier or later than the optimal degree of maturity. In a single-sex, bred-heifer (SSBH) system, the maximum value that could be attained with high technological efficiency and a reproductive rate of unity was 5·2 g, which was 0·5 times more efficient than the highest achievable traditional value. With a reproductive rate of 0·85, the highest efficiency value in an SSBH system was 4·8 g.Overall efficiency of food utilization was also examined in a sex-controlled system where all offspring for slaughter were male and in a modified traditional system where every surplus female was bred once. Both these systems could give higher efficiency (up to 1·08 times) than in a traditional system, but neither could compete with a well-operated SSBH system.Formulae to deal with multiple births, partial sex control and other factors are given in the APPENDIX.