Reproductive performance of sows selected for divergent social genetic effects for growth

Social genetic effects (SGE) are genetic effects of an individual that affect the phenotype of its social partners. We determined the reproductive consequences of selection for SGE on growth in pigs. To investigate the influence of social genetic effects on growth, gilts were divided into two groups based on their estimated SGE: positive SGE sows (+SGE) and negative SGE sows (-SGE). At the time of selection, gilts were contemporaries and similarly managed. We recorded the reproductive performance of the two groups based on parity until culling. Reproductive performance included the total number of piglets born (TNB), number of piglets born alive (NBA), average piglet birth weight (BW), coefficient of variation for birth weight (CVBW), age at first farrowing (AFF), weaning to estrus interval (WEI), and gestation length (GL). TNB was 0.5 higher for +SGE sows (13.8) than for -SGE sows (P = 0.03, SEM = 0.06), and NBA exhibited a higher tendency in +SGE sows (P = 0.07, SEM = 0.06). Positive SGE for growth was expressed at an earlier AFF (P = 0.04, SEM = 1.10), and shorter WEI (P < 0.01, SEM = 0.08) and GL (P = 0.03, SEM = 0.03). Collectively, the results of this study highlight the opportunities to improve litter size, the age at first farrowing, gestation length, and weaning to estrus interval using SGE.