Segregation analyses for presence of major genes affecting growth, backfat, and litter size in Dutch Meishan crossbreds.

Presence of major genes was investigated for two growth traits, backfat thickness, and two litter size traits in the F1 and F2 population of a cross between Meishan and European "White" pig lines. Segregation analyses were performed in a Bayesian setting, estimating the contribution of background polygenes and the contribution of a possible major gene to the expression of the traits considered. In a first analysis, F1 and F2 crossbred data were evaluated; different error variances were fitted for F1 and F2 observations. In the first analysis, significant contributions of major-gene variance were found for the two growth traits, backfat thickness, and litter size at first parity. In a second analysis, F2 data were evaluated to determine whether biases were introduced in the joint analysis of F1 and F2 data. In the second analysis, no major genes were found for growth traits. Major genes affecting backfat and litter size at first parity were confirmed. The gene identified to affect backfat is a dominant gene; the homozygous recessive genotype has approximately 6 mm of additional backfat. The gene identified to affect litter size at first parity also is a dominant gene; the homozygous recessive genotype produces five to six fewer pigs per litter.