Australian Brangus Cattle Association Implement Single-Step BREEDPLAN Evaluation

Nov 2023

The Australian Brangus Cattle Association (ABCA) has become the next Australian breed society to incorporate genomic (DNA) information into their BREEDPLAN genetic evaluations, using a method known as Single-Step. This major upgrade was implemented in the November 2023 Brangus BREEDPLAN evaluation.

The introduction of Single-Step was achieved through collaboration between ABCA and staff at the Animal Genetics and Breeding Unit (AGBU) and the Agricultural Business Research Institute (ABRI). The composite nature of the Brangus breed, where crossing of the original base breeds is on-going, means that there is a much greater diversity expressed within the population compared to a straight-bred population.  

“This creates a more complex scenario than is the case when evaluating one or the other of the base breeds. It is much simpler to determine how one Angus animal might relate to another Angus animal, or one Brahman to another Brahman – than to determine how one animal of high Angus content relates to one animal of high Brahman content in the Brangus population,” explains Dr. Brad Crook, BREEDPLAN Manager Genetics Research and Development.

“Consequently, the introduction of Single-Step BREEDPLAN for the Brangus breed has required a considerable amount of research, testing and validation to ensure the genotypes are used as correctly and accurately as possible.”

What is Single-Step BREEDPLAN?

Single-Step BREEDPLAN uses analytical software developed by AGBU, a joint venture of NSW Department of Primary Industries (NSW DPI) and the University of New England (UNE), funded by Meat and Livestock Australia Limited (MLA). The Single-Step BREEDPLAN evaluation utilises pedigree, performance and genomic information simultaneously. The evaluation takes account of each animal’s actual genetic relationship with all other genotyped animals, including those in the reference population. The reference population is the set of Brangus animals that have genotypes (SNP data) and phenotypes (performance records) for each particular trait.

SNP data is now being used along with pedigree and performance data to calculate BREEDPLAN EBVs and accuracy “in one step”. This applies to all traits in a multi-trait model combining birth, growth, fertility and carcase traits. As such, SNP data provides additional information in these calculations by accounting for the true genomic relationships among animals and how the SNP information relates to the performance records for each trait in the analysis. An important feature of the Single-Step BREEDPLAN approach is that complete use is made of the high density of genotypes recorded by ABCA members.

What are the advantages of Single-Step BREEDPLAN?

There are advantages that come with genomics and the Single-Step BREEDPLAN model. When young animals are genotyped at an early stage in life, they can achieve higher levels of EBV accuracy earlier in life – especially for traits expressed later in life – than is possible with a conventional (non-genomics) BREEDPLAN model. This equates to greater accuracy of selection decisions, at an earlier stage in the growth of animals, for Australian Brangus breeders. Furthermore, for breeders with small herds, accuracy levels are often limited by small contemporary group sizes even when pedigree and performance records are available. If calves are genotyped, however, they can accumulate additional information – and accuracy – via their relationship to the wider genotyped and performance recorded population.

Ultimately, implementation of Single-Step BREEDPLAN for the Brangus breed provides ABCA members with greater returns on their investment in the genotyping of seedstock cattle.