Application of aggregate genotype in beef cattle breeding

Abstract

When developing total merit indices (TMI's), estimated breeding values (EBV's) may be lacking for several traits. Methodology exists to address these challenges, calculating index weights using economic values and genetic (co)variances between traits included in the TMI and aggregate genotype. TMI's including production and functional traits were developed for beef breeds in the Norwegian breeding scheme, and potential for genetic gain was evaluated. Selection based on the TMI developed in this study was found to improve growth and carcass quality, while genetic deterioration was expected for calving difficulty. Alternative selection indices were applied to avoid these effects, but reduced the genetic gain for production traits. The results of our study show that is possible to achieve genetic gain in most economically important traits for beef cattle by using a TMI. When additional EBV's and genetic correlations become available, these should be included into the TMI for further improvement.