Reproduction rate is one of the main drivers of herd productivity and profitability and substantial scope exists to improve the gross value of northern beef production. The main factors affecting herd reproductive efficiency in northern Australian herds relate to delays in breeding females returning to oestrous after calving (lactational anoestrous / prolonged post-partum anoestrus interval) and age at puberty in Bos indicus breeds. As weaning rates of 50% or less are not uncommon in some northern herds, there is an urgent need to optimise beef production efficiency through the identification and implementation of efficient reproduction strategies.
The objective of this study was to define the genetic control of traditional and novel measures of male reproductive performance and their genetic correlations with critically important female traits, including age at puberty, post-partum anoestrous and traits associated with female lifetime reproductive performance. New traits in tropically adapted males to indirectly improve reproductive performance of male and female progeny were identified. The Beef CRC project generated 4063 male progeny weaned from Brahman and Tropical Composite breeds over 7 years (3648 progeny evaluated to 24 months of age). The data collected allowed the estimation of breed-specific heritabilities and genetic correlations for male fertility traits and were subsequently used to estimate genetic correlations with female reproduction traits using dam/son relationships. The progeny were generated by natural mating of the cows involved in the female reproduction experiment established in Beef CRC II.
Forty Brahman and Tropical Composite sires were used across years and locations to generate genetic linkage. Progeny were bred on Department of Employment, Economic Development and Innovation (DEEDI) Research Stations (Brian Pastures, Belmont, Toorak, Brigalow and Swan's Lagoon) and CSIRO Belmont Research Station. Bull progeny were evaluated for a range of traits at Brigalow and Belmont Research Stations from approximately 6 months of age (weaning) until 24 months of age.