Molecular basis for residual feed intake in beef cattle.

Feed provision is one of the greatest costs of beef production and, with the increasing costs of feed, will remain so for the foreseeable future. Improvement in efficiency has the potential to not only increase profits for cattle producers, but also to decrease the environmental footprint of beef cattle production. Both are important in addressing the challenges of increasing feed costs and land pressure. Residual feed intake (RFI) has increasingly become the measure of choice when evaluating feed efficiency in beef cattle, especially because it is independent of growth and BW. The main inhibitor to adoption of RFI remains the cost and technical difficulty in measuring the trait. This makes RFI a prime candidate for marker-assisted selection because the trait is moderately heritable and DNA or other predictive markers could be used in selection schemes. Although multiple markers have been described over several studies, no major gene affecting RFI has been found. However, a combination of genetic markers, when examined jointly, can explain a large proportion of the genetic variation. Two main barriers remain before full adoption of markers for genetic evaluation and marker-assisted selection can be implemented. First, the genetic interaction of genes affecting RFI on other traits is, as yet, not fully understood. Second the numbers of animals with high quality estimates of RFI remains small. However, current developments indicate that these challenges will soon be overcome.