Modelling the consequences of individual animal selection in commercial livestock farming systems

Genetic gain can be enhanced beyond sire selection alone through on-farm selection decisions. The economic implications of animal selection decisions are complicated by environmental constraints and the farm’s current level of performance relative to the industry average (Enns et al. 2010). This paper outlines the rationale for an approach to assess different individual animal selection strategies on enterprise productivity. The approach requires animal genetic potential within a livestock production model to be informed by an individual animal model used to predict changes to traits over time. The findings will be used in a decision support context to explore the interaction between animal genotype and phenotype.

Current livestock production models do not allow the representation of genetic diversity within populations and as such it is difficult to assess the value of selection decisions. Important parameters (such as growth rate) can be adjusted for cohorts but cannot be varied for individuals. This does not allow an accurate assessment of the rate of change of enterprise productivity achievable through selection. In contrast, for the prediction of genetic merit, individual animal phenotypes are corrected for known environmental effects and contemporary group membership whereas, in a production system, we want to predict uncorrected phenotypes (Kinghorn 2012).