Influence of the swine major histocompatibility complex on reproductive traits in miniature swine

Three swine leukocyte antigen (SLA)-defined strains of miniature swine and one recombinant strain were examined to evaluate the influence of the SLA Complex on litter size and piglet survivability. To separate the effects of sire and dam SLA haplotype from other sire and dam effects, a general linear model was employed to analyse data from 58 litters. Analysis of variance showed that sire and dam haplotype each contributed significantly to the variability observed in litter size among the sire and dam SLA combinations examined (P less than 0.0001, P less than 0.05, respectively). Sow SLA-haplotype as well as sire and dam effects other than those related to haplotype were significant factors contributing to survival until weaning (8 weeks) (P less than 0.10, P less than 0.07, P less than 0.001, respectively), but sire SLA-haplotype did not contribute significantly to this trait. Expected and observed haplotype frequencies of offspring in each litter were compared using chi-square analysis. A discrepancy was observed only in offspring from SLAa/d by SLAa/d matings, for which significantly fewer SLAa/a piglets were weaned than expected (P less than 0.06). Laparotomy during day 35-50 of pregnancy suggested that litter size was not an accurate estimate of ovulation rate and that ovulation rate was similar for dams of ad, ac and dd haplotypes.