THE VALUE OF CROSSBREEDING INFORMATION IN SELECTION OF POULTRY UNDER A DOMINANCE MODEL

A stochastic simulation teas used to investigate the value of crossbre eding information in a two line crossbreeding system in poultry under different genetic scenarios. Populations consisted of 25 sires and 250 dams, which were mated to produce both purebred and crossbred progeny . The next generation parents were selected either based on purebred i nformation (PLS) (sib means, and own performance for females) or addit ional crossbred sib means were included (CCPS). The trait under select ion was controlled by 20 loci with varying degree of dominance. Pure l ines differed in initial allele frequencies. If the trait was controll ed by loci with partial dominance, little or no extra benefit was obta ined from including crossbred information over the pure line informati on. Under complete dominance and overdominance CCPS outperformed PLS. As a practical rule, CCPS is better than PLS if the ratio between domi nance variance and total genetic variance is around 0.3 or higher. In this case the most probable cause of the dominance variation is loci w ith full or overdominance.