| The cost of feeding beef cattle accounts for more than 70% of the total variable cost in most production systems. Feed efficiency of beef cattle is therefore an economically relevant trait, which impacts the profitability and global competitiveness of the beef industry. Studies were conducted to characterize the metabolic and genomic mechanisms leading to variations in beef cattle feed efficiency. We employed the state-of-the-art radio-frequency-based GrowSafeRTM system to record the individual feed intake and behaviour of 464 Composite cattle over three years using the University of Alberta's experimental cattle population. Genetic and phenotypic parameter estimates for feed intake, feed efficiency, feeding behaviour, and temperament in beef cattle, and their genetic and phenotypic relationships with measures of growth and carcass merit are reported. It is demonstrated that differences among animals in heat production, digestibility, methane production, feeding behaviour, and energy retention may be responsible for a major part of the variation among animals in feed efficiency. It is further shown that the concentration of serum leptin in beef cattle is heritable, and there is moderate to high genetic and phenotypic correlations between serum leptin and carcass merit of beef cattle. However, correlations of bovine serum leptin with feed intake and feed efficiency were either low or not different from zero. The study reports associations of polymorphisms in the bovine leptin gene and its promoter with measures of growth, feed intake, feed efficiency, and carcass merit. Finally, the study reports a Bos taurus autosomal genome scan to locate quantitative trait loci for feed intake, feed efficiency, feeding behaviour, and temperament using genotypes from 455 genetic markers across 16 paternal half-sib families. The results of this study demonstrate ample opportunities for genetic improvement of beef cattle feed efficiency using metabolic- and genomics-based technologies. |
