The genomics of fat and fertility in pigs

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Over two decades, selection pressure in commercial pig populations has improved the efficiency of protein deposition at the expense of fat accumulation.   Reduction in body fat has been accompanied by later puberty, reduced litter size and a longer period for return to estrus after piglets are weaned.  This proposal has been developed to test the hypothesis that genes expressed predominantly or exclusively in adipose tissue in the pig serve as polymorphic genetic markers of reproductive traits and regulate reproductive processes. Our overall objective is to determine the influence and the mechanisms of adipose-associated genes and gene products on reproductive performance in swine.  The results will provide markers for genetic selection to improve fertility, along with insight into the role of fat in modulation of reproduction.   We will identify genomic markers in adipose tissue that predict reproductive traits, including puberty, litter size and weaning to estrus interval.  A multigenerational DNA bank derived from >3000 pigs of known reproductive phenotype will we screened for polymorphisms useful for genetic selection.  We will screen with known adipose genes, with unknown genes derived from our previous gene discovery efforts, and with genes from regions of chromosomes associated with reproductive traits.   We will further compare populations of pigs of elevated fertility (>16/litter) with subfertile populations (<9/litter) to establish reproductive characteristics and expression profiles of known and novel candidate genes in adipose and reproductive tissues.  We will determine the bases for variant fertility by studies of the ovary, uterus and embryo.  We will examine gene expression in subcutaneous and visceral fat depots to seek adipose correlates to prolificity.  A further goal is to determine the effects of subcutaneous and visceral adipose gene products on pig reproductive traits.  These studies will employ important endpoints including ovarian changes indicative of ovulation, embryo development to the blastocyst stage, and attachment of the embryo to the uterus.   This multifaceted project will yield new information on the genetics and functional genomics of pig reproduction valuable to the pig industry and to Canada.