STATUS OF MAPPING BOVINE QTL AT THE U.S. MEAT ANIMAL RESEARCH CENTER

USDA-ARS, U.S. Meat Animal Research Center, Clay Center, NE, USA

Three resource families have been developed for the identification of carcass trait and reproduction QTL. Phenotypic data for carcass and growth traits have been obtained on 300 progeny from a Brahman x Hereford sire. A QTL affecting Warner-Bratzler shear force at day 14 in steers was identified on BTA15 with an effect of one standard deviation . A QTL allele on BTA5 of Brahman origin increased the amount of rib bone and decreased dressing percentage. Other suggestive QTL included loci on BTA12 and 13 that affected percent retail product and component traits, a locus on BTA14 that affected rib eye area, and a locus on BTA1 that affected birth weight. The quantitative effect of these loci will be assessed when the genotyping is completed on all of the progeny. In a second resource family segregating the myostatin allele (Belgium and Piedmontese origin) for double muscling, selective genotyping of 94 progeny has identified putative loci for marbling on BTA27 and birth weight and yearling weight on BTA6. Additional statistical evidence for these loci may be obtained by genotyping 350 additional progeny of similar germplasm. A third population that was selected for increased ovulation and twinning rate was genotyped to identify components of follicular recruitment, growth, and development. Loci on BTA5 and 7 have been identified and additional markers will be genotyped to resolve the location of these loci. Preliminary analysis in the two carcass trait populations indicate that most segregating QTL identified thus far appear unique to one population or the other.