Supplied by Angus Australia — AngusPRO Magazine 2025
Recently, during the 2024 TACE Enhancements, the mature cow height and mature body condition traits transitioned from RBVs to EBVs. These traits are only available on animals recorded with Angus Australia – AngusPRO.
Profit drivers for beef producers are commonly linked to growth and carcass traits. However, to continue to make more informed selection decisions for overall herd profitability, consideration of mature cow traits that impact the performance of the cow herd will be essential. Mature Body Condition score (MBC), Mature Cow Height (MCH), and Mature Cow Weight (MCW) should be considered for their impact on the efficiency of the cow herd and tailored to your environmental conditions and market demands.
Current selection practices often rely on traits measured in younger animals, such as live ultrasound and carcass fat depth, to infer mature cow body condition and the ‘doing ability’ of females. To enhance our understanding of future selection decisions, Angus Australia’s genetic improvement team have been exploring the genetic correlations between mature cow traits and fat-depth traits, aiming to determine how selection for fat depth in young cattle affects mature cow characteristics, helping breeders make better-informed decisions for their breeding programmes.
Key Points
- Mature Body Condition and Mature Cow Height RBVs have been transitioned to EBVs.
- They join the suite of Maternal EBVs, including Mature Cow Weight and Milk.
- Members have responded to the “Breed Better Breeders” project by recording more body condition scores, hip heights and weights on the cow herd.
- Mature cow body condition is a different trait genetically to ultrasound scan and carcase rib or rump fats, with genetic correlations ranging from 0.08 to 0.35.
Angus Australia has been publishing Mature Body Condition (MBC) and Mature Cow Height Research Breeding Values (RBVs) for over 5 years. This started from regular member feedback asking for further genetic understanding of traits related to the productivity and profitability of the Angus cow herd. From this feedback, a collaborative project was developed with the University of New England known as “Breeding Better Breeders”, with the main output being the publication of the cow body composition traits, the MBC and MCH RBVs, as part of the routine TACE evaluation.
In the December 2023 TACE Enhancements, the model and parameters used to generate the MBC and MCH RBVs were enhanced significantly with the key points being;
- Significantly more animals display the Mature Body Condition and Mature Cow Height RBVs
- The variance components, including the heritabilities, for both traits were re-estimated, and
- Genomics was included through a single step evaluation model for both RBVs.
Based on the 2023 enhancements which ramped the evaluation up to ‘state-of-the-art’, and the response from members in recording significantly more weights, body condition scores and hip heights on their cow herds (figure 1 below), the MBC and MCH RBVs have been transitioned to EBVs.
With the transition to EBV status, the evaluation for these traits remains the same, but they are now reported consistently with other EBVs. This includes the animal listings, tables and graphs on angus.tech (figure 2 below) and listed in the relevant herd specific reports and files (TACE Herd EBV report, EBV extended file, Genetic Benchmarking Report) produced at each TACE evaluation.
As a reminder, for interpretation:
- Mature Cow Body Condition (MBC) EBVs provide estimates of genetic differences between animals in the body condition of mature females. Mature Cow Body Condition EBVs are calculated from a subjective assessment of an animal body condition and are expressed in score units. Higher Mature Body Condition EBVs indicate an animal is expected to produce daughters with more body condition as mature females.
- Mature Cow Height (MCH) EBVs provide estimates of genetic differences between animals in the height of mature females. Mature Cow Height EBVs are calculated from height measurements taken at the hip and are expressed in cm units. Higher Mature Cow Height EBVs indicate an animal is expected to produce daughters that are taller as mature females.
The genetic parameters for the MBC and MCH traits were recently calculated and reviewed and are a large part the reason for the transition from RBVs to EBVs.
Heritability
The traits are heritable (figure 3 above). Only part of the variation that we observe among animals is due to genetic differences. The majority of the variation is generally due to non-genetic factors such as differences in environment and nutrition. The degree to which genetic differences influence performance varies from trait to trait. This is explained by differences in the “heritability” of the traits.
The moderate to high heritability of the mature cow composition traits indicates that there is an opportunity for genetic improvement of these traits via genetic selection.
Genetics Correlations
Genetic correlations between two traits describe how much the same genes influence the two traits. In other words, how the two traits change in relation to each other. This relationship is expressed as a number between -1 and +1.
Genetic correlations can be either positive or negative. A negative correlation indicates that as one trait increases, the other decreases, whereas a positive correlation implies that both traits tend to increase or decrease together.
Additionally, genetic correlations can be described as strong or weak. Correlations closer to the absolute figure of -1 or +1 describe cases where a change in one trait is strongly associated with a change in the other, while lower figures (closer to 0) basically mean that for those pairs of traits,3 there will be no pattern to how one changes in relation to the other.
In relation to the fat traits, the genetic correlations (figure 4 below) show that MBC is genetically a very different trait compared to the bull and heifer fat ultrasound scans and steer carcase fat measurements. This means that more genetic progress or change can be made to cow herd body condition through direct selection, rather than via a correlated effect by selecting on the carcase fat EBVs. It also means that Angus producers can select to move the traits (cow body condition and steer carcase fat) in different directions if beneficial to the breeding objective.
