Angus Days to Calving Validated in Northern Australia

July 6, 2022 4:17 pm

Fertility is widely acknowledged as the most important profit driver for northern cattle production systems, with significant economic gains to be made from incremental increases in conception, branding and weaning rates.  

Currently, according to ABAREs farm survey data, the average weaning rate in northern Australia is estimated to be 63% – significantly lower than the 78% average in southern Australia. Estimations from the Australian Beef Report (2020) and ABAREs farm survey data reveal that with every percentage point increase in reproductive rates (one extra weaner per 100 breeders), an average operation’s herd income increases between $1,098 and $42,377 depending on the region – on average representing an estimated increase in profit of $109 million across the Northern Beef Industry. 

Angus genetics are being progressively incorporated into breeding programs across the north – not only to take advantage of the market premiums for Angus and Angus cross animals, but for the inherent Angus female fertility coupled with the ability to utilise fertility Estimated Breeding Values and make genetic gain in fertility related traits such as days to calving and scrotal size. 

This poses the question, do Trans Tasman Angus Cattle Evaluation (TACE) fertility EBVs relate to expected performance differences in the north, given that the majority of performance recording and genetics are based in southern production environments? 

To answer this question, Angus Australia undertook a research project in partnership with the University of Queensland to understand if there was the opportunity to improve fertility EBVs to better reflect northern performance. Utilising fertility performance data collected in Angus and Angus cross herds from 54 properties across Queensland, the Northern Territory and Western Australia collected in UQ’s Northern Genomics Project, the projects aims where to: 

  • Produce new Research Breeding Values to focus on the genetic description for the northern production environment,
  •  Assess the TACE Days to Calving EBV’s ability to predict differences in progeny performance in a northern setting, and
  • Consider the value of the inclusion of the Northern Genomic Project reference population data into TACE. 

New traits, new opportunities: 

By determining the relationship between the animals included in UQ’s Northern Genomics Project and the Australian Angus reference population, Research Breeding Values for a range of new traits developed by UQ could be generated for 5,123 Angus bulls. 

These RBVs included; 

  • Heifer Puberty: Heifer cycling or not cycling at 600 days, as determined by ovarian scanning. The presence of a corpus luteum indicates that the heifer has reached puberty or absence of a corpus luteum when scanned indicates that the heifer has not reached puberty. Heritability is estimated to be 22% and the more positive the RBV the earlier puberty can be expected in progeny. 
  • P4M: First calf heifer’s ability to re-conceive and are pregnant within 4 months of calving. Heritability is estimated to be 11% and the more positive the RBV the more likely the heifer progeny are to reconceive after their first calving. 
  • Tick Resistance: The more negative the RBV, the more tick resistance can be expected in the progeny. This trait is 33% heritable.
  • Buffalo Fly Lesions: The more negative the RBV, the less buffalo fly lesions can be expected in the progeny. This trait is 14% heritable. 

The results for the “top 10” registered Angus sires, sufficiently connected to the Northern Genomics Project reference population to have research breeding values generated on them are listed in the below table. 

Table 1: Top 10 sires (sufficiently connected to the Northern Genomics Project Reference Population for Heifer Fertility, P4M, Tick Resistance and Buffalo Fly Leision Reseach Breeding Values 


These new traits pose significant opportunity for the Australian Angus population, particularly as they may provide a greater description of fertility performance in Northern Australia and resilience to parasites unique to the northern production environment which, anecdotally, are a limiting factor in Angus usage. 

Days to Calving’s performance in the north: 

The genetic correlations between the Angus Australia Days to Calving EBV and Northern genomics traits from a full multi-trait analysis were favourable (Days to Calving was negatively correlated with heifer puberty and P4M). This means that by selecting Angus sires that have shorter Days to Calving EBVs, their heifer progeny in Northern Australia are likely to reach puberty earlier and have increased rates of re-conception after their first calf. Due to the predominantly cross-bred and Bos indicus influenced nature of the Northern reference population, the favourable relationship between Days to Calving were stronger when a subset of the Northern Genomics data, where only heifers with less than or equal to 50% Bos indicus content was used. 

Table 2: Genetic Correlation between Days to Calving and Heifer Puberty and P4M based on the phenotypes collected on Northern Genomics Project reference population females with less than 50% Bos indicus content 


The project also showed that the accuracy of the Days to Calving EBV could be increased by including the Northern Genomics reference population data in TACE. This would result from additional modelling, and building in the Heifer Puberty and P4M records as genetically correlated traits to Days to Calving. 

Where to from here: 

There are a number of opportunities to consider arising from this project, which include; 

  • Continued effort in collection of Days to Calving data, particularly in northern environments. Due to the predominate use of AI in the Australian Angus herd, Days to Calving is considered a hard to measure trait. Greater data collection will ensure that Days to Calving continues to allow for accurate selection for fertility in the Australia production system, coupled with extension promoting the benefits of Days to Calving. 
  • Leveraging genomic technology to gain tick and fly resistance values. Genomics is likely to play a vital role in gaining robust genetic evaluation for northern focused RBVs such as tick and fly. 
  • Investigating the potential to include data from existing sources such as UQ’s Northern Genomics Project into TACE 

It also illustrates the potential for further research and validation for new traits to be conducted in northern Angus populations. These opportunities will be further assessed during 2022. If you have any feedback that you would like considered, please contact Angus Australia’s Northern Development Officer Jen Peart – M: 0417 219 405 or E: or the Northern Development Consultative Committee.