Reproduction rate is a key profit driver in northern Australia, but some producers are weaning less than 50pc while the average is still only at 72pc. A new genetic tool will help make selecting for fertility much easier.
An MLA-funded Beef CRC project has measured the performance of 3500 Brahman and Tropical Composite bulls and identified which male fertility traits correlate to female reproductive performance.
The University of Queensland’s Dr Brian Burns said the research gave producers a cost-effective solution to make genetic and economic gains across their entire herd.
Producers already have access to Estimated Breeding Values (EBVs) for scrotal size and days to calving for making genetic progress in reproductive performance. These new results will likely lead to an integrated EBV for reproductive performance that combines the existing EBV traits with data on traits such as age at puberty, post-partum anoestrus interval (PPAI) – the period from calving to starting to cycle again – and percentage of normal sperm.
“Identifying these early-in-life predictors of a bull’s fertility will help reduce the number of bulls required for breeding by up to 50% and increase the number of calves born,” Brian said.
“Selection for sperm motility alone could achieve a 6% increase in lifetime weaning rate over 10 years. PPAI is also heritable, so producers can improve herd fertility – especially in Brahman cattle – by selecting bulls whose daughters will have shorter PPAI.”
Traditionally, selection for cow fertility in northern herds could only be applied to females after they had been through several mating periods, so genetic gains were slow. Tropically adapted beef breeds had little genetic information for male reproductive traits which influence female reproductive performance.
This project evaluated bulls from birth to 24 months of age for 109 traits to assess heritability and correlation to female reproduction traits.
Researchers found that:
- key components of fertility (age of puberty, post-partum re-conception interval, scrotal circumference and semen quality) are heritable in these two breeds;
- bull reproductive traits (especially sperm morphology) are genetically linked to female reproduction, so selecting for male fertility will genetically improve their daughters’ fertility;
- selection for fertility doesn’t come at the cost of other economically important traits, so multi-trait selection is possible;
- significant variation exists for key bull traits such as semen quality and scrotal circumference;
- genetic and in-herd economic benefits can accrue if seedstock producers record scrotal circumference and conduct bull breeding soundness evaluations on young bulls.
Brian said this information was critical for northern cattle producers who faced different challenges than their southern counterparts, such as extensive management systems, harsher environments, parasite burdens and breed differences.
“Commercial producers should use genetically superior bulls which are sound and tested to increase calving rates and reduce the number of bulls required.”
“Selecting these bulls for the key traits will improve male and female reproductive performance and increase the profit potential of the entire herd.”
Where to now?
The Next Gen Beef Breeding Strategies Project, funded by the Queensland Government, is now working with key seedstock herds to develop commercially viable recording mechanisms for the traits measured in this Beef CRC project.
A tool kit for northern cattle producers:
- use EBVs to identify superior bulls;
- only use Bull Breeding Soundness Examination tested, sound and fertile bulls;
- select male and female replacements from calves born early in the calving season, from cows that have not missed a call;
- for faster progress, use superior genetics – select fertility EBVs: scrotal size in males, days-to-calving in females;
- combine EBVs with selection indexes, structural soundness and temperament assessments to maximise genetic gain and herd functionality;
- consider using MateSel, a tool which helps to optimise matings to reflect breeding goals and make long-term sustainable genetic gains.
MLA News is a regular snapshot of recent market and industry news provided by Australia's producer levy-funded industry service organisation Meat & Livestock Australia