ASSOCIATION OF PIT1 POLYMORPHISMS WITH GROWTH AND CARCASS TRAITS IN PIGS

PIT1, a member of the POU-domain family of genes, is a positive regula tory factor of growth hormone, prolactin, and thyrotroph-stimulating h ormone beta in several mammals. Therefore, PIT1 was chosen as a candid ate gene to investigate its association with growth and carcass traits in pigs. The five Iowa State University reference/resource three-gene ration families consisting of crosses of Meishan x Duroc, Meishan x Ha mpshire, Meishan x Landrace, Minzhu x Hampshire, and Minzhu x Landrace were used. The three PIT1 polymorphisms were based on two RFLP using a PIT1 POU-domain cDNA probe and the restriction enzymes BamHI and Msp I and a PCR/RFLP using RsaI. Birth, 21-d, and 42-d weights, average da ily gain, several backfat measurements, longissimus muscle area, muscl e color, marbling, and firmness scores were evaluated for their associ ation with the three PIT1 polymorphisms. Mixed-animal-model analyses w ere used with the informative family data in which the PIT1 polymorphi sms were segregating. Results from mixed-model analyses revealed that pigs with the MspI CC genotype (P <.01) were associated with heavier b irth weight (.12 kg) than DD genotype pigs. The MspI CC genotype pigs were also significantly associated with greater average backfat (.41 c m, P <.01), greater first-rib backfat (.45 cm, P <.01), greater last-r ib backfat (.32 cm, P <.07), and greater last lumbar backfat (.46 cm, P <.10) than the DD genotype pigs. The CC genotype represents primaril y Chinese alleles and may be useful for future genetic improvement in synthetic lines involving Chinese and American pigs. Results from this study suggest that PIT1 may be a candidate gene for a quantitative tr ait locus in pigs.