Breeding for improvement of functional traits in dairy cattle

Abstract

Selection programs for increasing milk production per cow have been very successful over time. This success has been partially due to the consideration of few other traits. Unfortunately, many traits related to costs of production and cattle functionality (i.e., "functional traits"), such as fertility and health, are antagonistically correlated with milk yield. Therefore, the average merit for these traits has decreased over time. The decline in functionality, along with increased awareness of the costs of production and animal well-being, has spurred interest in breeding for improvement in functional traits. Unfortunately, factors such as low heritability and lack of data make the selection for functionality more difficult than for production. Research has been able to overcome some of these limitations, at least to some extent, through the development and application of advanced statistical analyses and through indirect selection on genetically correlated traits. Possibilities exist in the future for additional refinement of selection procedures for improvement of functional traits. Computing capacities are continually increasing and more complex but statistically appropriate analysis methods are being developed. Furthermore, genome scans have identified chromosomal regions that have putative associations with functional traits. The bovine genome has been recently sequenced, so the possibility to identify the genes affecting functional traits exists, at least in theory. With low heritabilities and difficulties in measurement, functional traits are the ideal candidates for the application of marker-assisted selection.