Genetic improvement of cow reproduction in northern Australia beef cattle breeds

Abstract

<p>Northern Australia is characterised by high temperatures, seasonally fluctuating feed quality and unique parasitic challenges. <i>Bos indicus</i> and <i>bos indicus</i> derived breeds are favoured for their ability to withstand these challenges and produce in the harsh northern Australian environment. Cow reproduction is an important driver for breeding profitable beef enterprises but has typically been difficult to select for with traits generally being lowly heritable, sex-limited and expressed late in life. The key cow reproduction trait in the Australian BREEDPLAN genetic evaluation is days to calving which has been demonstrated to be highly correlated with calving success (i.e. did the cow calve or not). The development of two highly heritable ovarian ultrasound scan traits when implemented as part of genomic selection may be a game changer in creating opportunities for genetic improvement of cow reproduction in northern beef herds. Age at puberty and lactation anoestrus interval are both highly heritable (h² estimates of approximately 0.50 and 0.40, respectively) and correlated to days to calving -the key cow reproduction trait currently analysed in BREEDPLAN. The purpose of this chapter was first to outline the current genetic improvement program for female reproduction in northern Australia beef cattle breeds, and secondly to show how the incorporation of ovarian scan traits and genomic selection are providing a new and exciting opportunity to make significant genetic improvement for female reproduction.</p>