Pelvic and Scrotal Measurements in Test Station Bulls

Abstract

Pelvic measurements, scrotal circumference, birth weight, 365-d weight, and age were obtained on 422 test station bulls representing three breeds. Breed groups were comprised of 175 Angus, 94 Hereford, and 153 Salers bulls that completed the 1990 performance trial at the Midland Bull Test Station at Columbus, MT. Breed effects were evaluated for pelvic height (PH), pelvic width (PW), pelvic area (PA: product of PH and PW), and scrotal circumference (SC). Linear and quadratic covariates for age or 365-d weight (WT365) and their interactions with breed were also evaluated. Salers were analyzed separately to evaluate the effects of percentage (percent) Salers. Residual phenotypic correlations were calculated among PH, PW, PA, SC, birth weight (BW), and WT365. Breed and linear age effects were significant (P<.05) for PA and PW. Salers had the largest PA followed by Angus and Hereford (P<.01). The linear regression of PA on age was .201 cm2/day. The interaction of breed with age was significant only for PH. Linear effects of WT365 were significant (P<.05) for PA and PH, while quadratic effects of WT365 were significant for PW and SC. The linear regression of PA on weight was .100 cm2/kg. Phenotypic correlations between pelvic dimensions and WT365 and SC were low to moderate. Percentage of Salers breeding was only a significant source of variation for SC. In conclusion, differences between breeds existed for pelvic dimensions. Differences among bulls in PA were independent of differences in SC. Differences between different percentage Salers bulls were small.