81,630 – This is the number of progeny registered with Angus Australia from sires used in the ASBP.
To take a step back, one of the main objectives of the Angus Sire Benchmarking Program (ASBP) is to build a reference population of modern Angus cattle. An effective reference population is important as it enables the Angus breed to take full advantage of genomic technologies. Building the ASBP reference population involves focussed recording of genotypes, pedigree and phenotypes, particularly for hard-to-measure traits such as feed intake, carcase yield, beef quality attributes, heifer fertility and immune competence.
To date, the ASBP has produced 8 Cohorts of progeny as summarised in the table 1. 299 sires have entered to produce 9,023 progeny. All progeny have been comprehensively performance recorded from birth to slaughter (steers) and birth to first-parity (heifers). Importantly, they are also all genotyped (DNA profiled) and have pedigree recorded.
For a reference population to be useful, particularly for genetic evaluation, it must be representative of the population from which breeding animal selection is occurring, in this case the Australian Angus population. So, on this basis, is the ASBP an effective reference population?
As a first step to answer this question, it has been identified that across the 299 sires used in the ASBP they collectively have 81,630 progeny registered across 719 member herds. This is an average of 273 progeny per sire and 114 progeny per herd. Additionally, 155 of the ASBP sires have 100 or more progeny registered with Angus Australia.
The ASBP sires have also come from all major Angus bull breeding regions of Australia (figure 1). The sires have been bred, on a state basis, in NSW (n=155), Victoria (n=64), Western Australia (n=17), Tasmania (n=9), Queensland (n=7) and South Australia (n=6). Several overseas bred bulls have also entered including New Zealand (n=30), USA (n=8) and the United Kingdom (n=3).
While the above indicates that the ASBP includes sires that are reflective of modern Angus genetics, this has recently been validated through a more technically sophisticated approach. A study undertaken by Vinzent Borner et al (2017 unpublished) looked at the degree of relatedness, on a DNA level, between the ASBP sires to all Angus animals genotyped and registered with Angus Australia (n=32,659). Using principle component analysis, the study revealed that the ASBP sires had strong and significant relatedness across the Angus population that are genotyped.
Although it is important for ASBP sires to be diverse and representative of the overall Angus population, it is also important to balance this with the aim for genetic progress. This is the focus of another major objective of the ASBP which is to progeny test modern Angus bulls.
The progeny test component of the ASBP facilitates selection of sires and Angus genetics to help drive genetic progress for the Angus breed, industry and supply chain such as commercial herds, feedlots, abattoirs and ultimately the consumer. Figure 3 shows that the sires average Angus Breeding Index (ABI) has been increasing across each Cohort and more noticeably from Cohort 6. The Cohort 8 sires average +$142 on ABI placing them in the top 5% of the breed.
While on average the ASBP sires are a high-performance group, particularly in more recent Cohorts, within each Cohort there is a planned range of EBVs on a trait basis. This is in consideration of selection that occurs in Angus herds on trait specific basis, as well as assisting research where trait variation is required. An example of the EBV variation in the Cohort 8 sires in listed in table 2.
A challenge for the ASBP is to ensure it maintains momentum and continues to build the Angus reference population. For example, for hard-to-measure traits at different levels of heritability (h2) the following numbers of phenotyped and genotyped animals are required in the reference population to achieve an Estimated Breeding Value (EBV) accuracy of 70% for a genotyped only animal (Figure 4) is:
For comparison, Cohorts 1 to 8 to the ASBP will deliver approximately 4,000 steers that have been measured for net feed intake and carcase traits such as MSA marbling score. A similar number of heifers will be measured for days-to-calving to their first calving.
It is also essential to continually update the reference population with phenotypes and genotypes from modern animals due to the occurrence of linkage disequilibrium decay. This means a reference population produced today may be less effective for breeding value calculation for animals of tomorrow, unless the reference population is continually seeded with modern Angus animals.
With the challenges in mind, Angus breeders can be confident that the ASBP is achieving its objective to build an effective reference population of Angus cattle while also progeny testing modern Angus sires for genetic progress.