Genetic and phenotypic parameter estimates of pelvic measurements and birth weight in beef heifers

Data on 1210 spring-born (1983 to 1988) yearling heifers were analyzed by paternal half-sib procedures to obtain genetic and phenotypic parameter estimates involving birth weight and pelvic measurements. Data included records on 629 Angus, 325 Simmental, and 256 Salers representing 93, 49, and 22 paternal half-sib sire groups, respectively. Heritabilities for birth weight (BW), pelvic height (PH), pelvic width (PW), and pelvic area (PA) for Angus were 0.30, 0.61, 0.28, and 0.43, respectively. Corresponding values for Simmental and Salers heifers were 0.14, 0.34, 0.44, 0.37, and 0.18, 0.02, 0.29, 0.15, respectively. Genetic correlations among pelvic measurements (PH-PW, PH-PA, PW-PA) were positive (0.25 to 1.03) except for the estimate of -0.07 for PH-PW in Simmentals. Genetic correlations between BW and the 3 pelvic measurements (BW-PH, BW-PW, BW-PA) were negative (-0.18 to -0.36) except for the estimates of 0.53 (BW-PW) and 0.26 (BW-PA) in Simmentals and 2.84 (BW-PH) and 0.39 (BW-PA) in Salers. Phenotypic correlations among pelvic measurements ranged from 0.16 to 0.80. Phenotypic correlations between birth weight and the 3 pelvic measurements were consistently lower (-0.02 to 0.09) than the genetic correlations.