THE resilience of cattle to disease has long been recognised as a major driver of productivity, welfare and profitability in the Australian beef industry.

While producers are accustomed to focusing on growth, fertility and carcase traits when buying bulls or making breeding decisions, research from the Southern Multibreed Project has highlighted the importance of cattle resistance to disease and the effects of stress on productivity and profitability.

Published in late 2024, the Southern Multibreed Immune Competence Project presented key findings from the first large-scale assessment of immune competence across Australia’s major beef breeds.

More than 3000 calves from Angus, Brahman, Charolais, Hereford, Simmental, Wagyu and crossbred lines were tested at weaning. Researchers measured how effectively each animal mounted both antibody-mediated and cell-mediated immune responses.

Data on temperament and stress-coping ability was also collected, providing a more complete picture of how resilience traits operate within and between breeds.

The results confirmed that immune competence is heritable and variable across every breed, and that it has a genetic relationship with productivity. In practice, this means that disease resilience can be selected for in the same way as growth or fertility.

While this is not necessarily a new concept, the project provided evidence of a small but clear negative correlation between immune competence and growth. This finding reinforces that if breeding programs focus only on faster growth without considering immune system function, herds may gradually lose resilience to health challenges.

Economic evidence

Earlier Angus-specific research funded by Meat & Livestock Australia (project B.STU.0244) provided the first hard economic evidence of the financial impact of immune competence.

That study classified calves into high, average and low immune competence groups. High immune competence calves recorded no mortalities and health costs of just four dollars per head. Average immune competence calves had a mortality rate of 1.2 percent and health costs of $28 per head, while the low immune competence group recorded a mortality rate of 6.1pc and incurred health costs of about $103 per head.

While the Southern Multibreed study did not attempt to place updated dollar values on the trait, its broader scope confirmed that the same variation exists in every breed. It also showed that distributions overlapped, with no breed proving consistently “better” or “worse.”

Highs and lows

Within each breed tested, some animals ranked high for immune competence and others low. For producers, this is an important point to consider. That is resilience is an individual animal trait, not a breed-wide advantage or weakness.

Another important outcome was the development of a multibreed genomic prediction equation for immune competence. By combining immune response measures with genomic data, researchers showed it is possible to estimate immune competence values across breeds.

While there is not yet a commercial breeding value available to producers, it is a critical research step toward including resilience traits in future selection indexes. The report makes it clear that immune competence can be measured; that it is moderately heritable; and that genomic tools can be developed to predict it.

The study also demonstrated that immune competence should not be thought of in isolation. It needs to be considered alongside temperament and stress-coping ability as part of a broader picture of animal resilience.

By measuring these traits together, researchers showed they are distinct. Immune competence was not strongly correlated with temperament or with weight change during weaning. This means producers need to assess each trait on its own merits, rather than assuming, for example, that a quiet calf is necessarily more resilient to disease.

In the longer term, a resilience index combining immune competence, temperament and stress response may provide a practical way to balance these factors.

For producers, the message is clear: resilience matters as much as productivity. Selecting only for growth risks weakening herd disease resistance over time.

The MLA research makes it clear that immune competence can and should be part of the broader conversation about breeding and management.

 

Alastair Rayner

Alastair Rayner is Principal of RaynerAg and an Extension & Engagement Consultant with the Agricultural Business Research Institute (ABRI). He has over 28 years’ experience advising beef producers and graziers across Australia. Alastair can be contacted here or through his website: www.raynerag.com.au