Preputial Eversion in Young, Tropically Adapted Bulls is a Useful Genetic Indicator Trait for Improving Female Reproduction

Abstract

Beef CRC research showed that a measure of preputial eversion (PEV: an estimate of the length of preputial mucosa (mm) exposed while a bull stands freely) in tropically adapted bulls at 18 months of age was heritable, and had significant genetic associations with female reproduction performance. The current study examined the sensitivity of genetic parameters for PEV to age by expanding the analysis to include measures at 12 and 24 months. For Brahman bulls, the incidence of non-zero PEV increased with age, from 45 to 59 to 71% at 12, 18 and 24 months respectively. For Tropical Composite bulls, the incidence of PEV was lower and less influenced by age (27 - 31%). Heritabilities for PEV at 12 and 24 months were comparable to those previously reported at 18 months (h² = 0.23 to 0.34). These results confirm that if breeders of tropically adapted beef cattle wished to apply selection to improve PEV, this could be undertaken successfully. Genetic correlations of PEV with female age at puberty, lactation anoestrous and lifetime annual weaning rate showed that if PEV were to be exploited as a genetic indicator for female reproductive performance, measures at 18 and 24 months would be more useful than those collected at 12 months of age. Compared to female reproduction traits, preputial eversion is easy to measure and this study suggests it would be a useful trait to add to the genetic evaluation for tropical breeds.