Estimation of crossbreeding parameters between Large White and Meishan porcine breeds. III. Dominance and epistatic components of heterosis on reproductive traits

Abstract

A crossbreeding experiment using Large White (LW) and Meishan pigs was conducted. Dominance, additive x additive and dominance x dominance epistatic components of direct and maternal heterosis effects were investigated for various litter productivity and sow traits: total number born (TNB), number born alive (NBA), number weaned (NW), litter weight at birth (LWB) and at 21 days of age (LW21), either adjusted or not adjusted for litter size, sow weight loss (SWL), sow total and maximum feed consumption (SFC and SFCM respectively) , sow feed efficiency (computed as SFC per piglet weaned (SFC/NW) or per unit of litter weight (SFC/LWG) during lactation). Data on 1148 litters from 250 sows were analysed. Models involving all possible combinations of dominance and epistatic parameters were compared for goodness of fit on the basis of their mean squared error (MSE). The model with the lowest MSE was then used to estimate crossbreeding parameters. Models involving dominance effects only for maternal heterosis had the lowest MSE for all litter productivity traits. Dominance also appeared as the main component of direct heterosis effects on litter productivity traits. Favourable dominance and unfavourable epistatic effects contributed to direct heterosis effects for all sow traits except SFCM. Epistatic effects were additive x additive for SFC/NW and dominance x dominance for SWL, SFC and SFC/LWG. Estimates of direct maternal and grand-maternal breed effects were obtained. A contribution of cytoplasmic effects to between-breed variation is hypothesized.