Evaluating the Predictive Value of Estimated Breeding Values of Piétrain Sires for Uniformity and Survival in Their Crossbred Progeny.

High litter sizes in pigs are associated with lower birth weights and increased within-litter variation, which poses challenges to pig farming. Improving piglet uniformity and survival via genetic selection of terminal boars could be a strategy to enhance these traits. This study evaluated how well estimated breeding values for uniformity and survival of terminal Piétrain sires predict within-litter uniformity and mortality rates in their crossbred offspring from birth until slaughter. We selected six Piétrain boars with contrasting estimated breeding values for uniformity and survival (3 high vs. 3 low) and mated these with 93 hybrid sows, which produced 1421 liveborn piglets. Moderate correlations were observed between crossbred piglets' within-litter uniformity and the paternal estimated breeding values (r = 0.17 to 0.28), indicating that the used estimated breeding values for uniformity and survival of terminal sires have a low predictive value for within-litter uniformity. Nonetheless, significant associations were found between these estimated breeding values and specific survival- and uniformity-related traits, such as pre-weaning survival and uniformity of growth, supporting their potential for selection. When analysing piglets' weights over time, low correlations were observed between the coefficient of variation at birth and later in life (r = 0.05 to 0.24). On the other hand, moderate to high correlations were found between coefficients of variation at weaning and later in life (r = 0.34 to 0.88), indicating stability of the within-litter body weight uniformity after weaning. These findings suggest that pre- and post-weaning within-litter body weight uniformity should be considered as two distinct traits.