Understanding the Genetics of Lactation Anoestrus in Brahman Beef Cattle to Enhance Genetic Evaluation of Female Reproductive Traits

Abstract

Female reproduction is an important profit driver in northern Australia beef production systems. However low weaning rates are common, and are mainly the result of extended post-partum anoestrus intervals, especially in 'Bos indicus' cattle (Entwistle 1983). Research, mainly in dairy, has established that measures of postpartum anoestrus, such as calving to ovulation interval, are moderately heritable and may offer means to genetically improve female reproduction. Age at puberty has also been shown to be highly heritable in Brahman cattle (Johnston et al. 2006). Currently world-wide, genetic evaluation of female reproduction in beef cattle is limited. In Australia days to calving is used (Graser et al. 2005) and some other countries have analyses for heifer pregnancy. The aim of this work was to determine the amount of genetic variation in measures of lactation anoestrus in Brahmans, and its relationship to age at puberty, and to discuss implications for the genetic evaluation of female reproduction.