Developments in quantitative genetics and genomics relevant for poultry breeding

Developments in genetics and genomics relevant for poultry breeding are reviewed, focusing on the use of molecular information in breeding programmes and the potential for improving traits affected by social interactions among individuals. QTL mapping studies have resulted in almost 700 QTL for a wide variety of traits, showing that they have been successful. However, few applications of marker-assisted selection in commercial poultry breeding exist, mainly because evidence for the QTL is often not conclusive and confidence intervals for QTL locations are large, making utilization in practice difficult. Moreover, moving from QTL to causal mutation has been successful only in a few cases. Thus, neither MAS nor selection for known genes will greatly increase responses to selection in the near future. Genome-wide selection (GWS), however, may offer a solution. Basically GWS is a method to estimate breeding values. Simulation studies suggest that accuracies of EBVs in the range of 0.7-0.8 are feasible. Tests of GWS on real data are currently ongoing, and initial results are promising. The second section of this chapter shows that social interactions create considerable heritable variance that is hidden in classical analyses. Results show that social effects contribute more than half of the heritable variance in mortality due to cannibalism in laying hens, and in growth rate and feed intake in growing pigs. We present statistical models and breeding strategies to utilize this extra heritable variation for genetic improvement. Though social genetic effects may not always be important or may be difficult to use in some cases, the promising results observed in laying hens and pigs should be sufficient incentive for further research in this area.