Association of PITl Polymorphisms with Growth and Carcass Traits in Pigs'f2

PIT1, a member of the POU-domain family of genes, is a positive regulatory factor of growth hormone, prolactin, and thyrotroph-stimulating hormone /3 in several mammals. Therefore, PITl was chosen as a candidate gene to investigate its association with growth and carcass traits in pigs. The five Iowa State University referencehesource threegeneration families consisting of crosses of Meishan x Duroc, Meishan x Hampshire, Meishan x Landrace, Minzhu x Hampshire, and Minzhu x Landrace were used. The three PITl polymorphisms were based on two RFLP using a PITl POU-domain cDNA probe and the restriction enzymes BamHI and MspI and a PCW RFLP using RsaI. Birth, 21-d, and 42-d weights, average daily gain, several backfat measurements, longissimus muscle area, muscle color, marbling, and firmness scores were evaluated for their association with the three PITl polymorphisms. Mixed-animalmodel analyses were used with the informative family data in which the PITl polymorphisms were segregating. Results from mixed-model analyses revealed that pigs with the MspI CC genotype ( P < .01) were associated with heavier birth weight (. 12 kg) than DD genotype pigs. The MspI CC genotype pigs were also significantly associated with greater average backfat ( .41 cm, P < . O l ) , greater first-rib backfat (.45 cm, P < .Ol), greater last-rib backfat (.32 cm, P < .07), and greater last lumbar backfat (.46 cm, P < . l o > than the DD genotype pigs. The CC genotype represents primarily Chinese alleles and may be useful for future genetic improvement in synthetic lines involving Chinese and American pigs. Results from this study suggest that PITl may be a candidate gene for a quantitative trait locus in pigs.