PSXII-18 - Genome-wide Association for Behavioral Anestrus in Swine

Abstract: Gilts represent a significant portion of breeding females, and producer success largely depends on lifetime prolificacy and number of lifetime litters produced. Expression and precise detection of first estrus are key components for successful breeding. Failure to express behavioral signs of estrus, also known as prebreeding anestrus, affects 10-30% of gilts resulting in premature culling. Behavioral anestrus (BA), that is ovulatory cycles of the ovary without signs of estrus, is a major type of prebreeding anestrus that affects up to 5% of the gilt population at the U.S. Meat Animal Research Center. Examination of ovaries revealed that 38% of BA gilts had exhibited more than one ovulatory cycle. Identification of genomic predictors of BA could minimize prebreeding anestrus in gilts. Data collected from normal cyclic (n=2,421) and BA gilts (n=515) from a multigeneration Yorkshire-Landrace-Duroc composite population were used for a case-control genome-wide association to identify candidate genes and cell signaling pathways associated with BA in gilts. The genomic heritability for BA in the population was 0.35. Fifty-six genome-wide significant SNP were identified with proportion of phenotypic variance explained by each SNP ranging from 0.009 to 0.06. Quantitative trait loci identified for BA harbor candidate genes involved in olfaction (OR13H1) and behavioral disorders (PLCB4). Biologically this is expected because, activation of olfactory pathways by boar pheromones is important to stimulate female lordosis behavior and sexual receptivity to boar. Several candidate genes identified for BA (IGSF1, MSTN, RXRG) were previously reported for age at puberty in humans and cattle suggesting the pleiotropic nature of these genes influencing multiple estrus related traits in different species. To our knowledge this is the first large scale association analysis performed for BA in pigs and these data are an important first step to facilitate future studies to identify functional polymorphisms regulating estrus behavior in gilts.
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