GENETIC AND PHENOTYPIC PARAMETER ESTIMATES OF PELVIC MEASUREMENTS ANDBIRTH-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 para meter estimates involving birth weight and pelvic measurements. Data i ncluded records on 629 Angus, 325 Simmental, and 256 Salers representi ng 93, 49, and 22 paternal half-sib sire groups, respectively. Heritab ilities 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, respec tively. Corresponding values for Simmental and Salers heifers were 0.1 4, 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 pos itive (0.25 to 1.03) except for the estimate of -0.07 for PH-PW in Sim mentals. 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 e stimates of 0.53 (BW-PW) and 0.26 (BW-PA) in Simmentals and 2.84 (BW-P H) and 0.39 (BW-PA) in Salers. Phenotypic correlations among pelvic me asurements ranged from 0.16 to 0.80. Phenotypic correlations between b irth weight and the 3 pelvic measurements were consistently lower (-0. 02 to 0.09) than the genetic correlations.