CHARACTERIZATION OF DNA POLYMORPHISMS IN 3 POPULATIONS OF HEREFORD CATTLE AND THEIR ASSOCIATIONS WITH GROWTH AND MATERNAL EPD IN LINE-1 HEREFORDS

Three populations of Hereford cattle differing in inbreeding levels an d genetic potential for growth were genotyped for seven DNA polymorphi sms. The populations were compared to determine differences in allele frequency and genetic variation. Significant differences in allele fre quency among the populations were found at six of the seven polymorphi sms genotyped, and average genetic variation differed as expected when inbreeding levels were considered. Effects of several polymorphisms o n growth and maternal EPD were evaluated for one population (Miles Cit y Line 1 Herefords) using regression analysis. Substitution of a B all ele for an A allele of the kappa-casein polymorphism accounted for sig nificant decreases in direct birth weight and maternal 180-d gain from birth to weaning EPD, explaining 15% and 8%, respectively, of EPD var iability. Several other significant effects accounting for small porti ons of EPD variability were also detected.