Female reproductive performance and its relationship with age at puberty in beef heifers of two tropically adapted genotypes in northern Australia

Abstract

Improved female reproductive performance (FRP) of beef breeds in northern Australia is an important means to increase profitability. However selection to improve FRP has proved difficult due to low heritabilities and late expression of traits. One trait that may influence maiden calving performance is age at puberty. Several studies have shown age at puberty is heritable in beef cattle, particularly in 'Bos taurus' breeds (e.g. Gregory et al. 1995), but limited studies (and numbers) exist for 'Bos indicus' genotypes. Vargas et al. (1998) reported, from a small study, a heritability for age at puberty in Brahmans of 0.42. However the relationship between age at puberty and subsequent measures of female fertility are inconclusive. Some studies show a favourable relationship between improved pregnancies and earlier age at puberty (Morris et al. 2000). However several others (e.g. Dow et al. 1982) have observed no relationship. The aim of this study was to estimate the heritability of FRP traits and the genetic correlation with age at puberty in 2 tropically adapted genotypes raised in northern Australian environments.