L.GEN.1817 - Quantifying the benefits of breeding for immune competence in high disease risk feedlots
Steers that are below-average for immune competence are three times more likely to die during feedlot finishing than steers above-average for immune competence.
| Project start date: | 30 May 2019 |
| Project end date: | 30 August 2022 |
| Publication date: | 02 May 2024 |
| Project status: | Completed |
| Livestock species: | Grain-fed Cattle, Grass-fed Cattle |
| Relevant regions: | National |
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Summary
Selection for production traits with little or no emphasis on health-related traits has led to an increase in the incidence of disease in many production animal systems. Further, ever-changing climatic conditions experienced in production environments are seeing animals exposed to disease challenges not previously encountered. Therefore, we have developed a testing procedure to assess the immune competence of beef cattle on-farm which we expect will allow producers to select animals in their herds that are both highly productive and have an enhanced ability to cope with general disease challenges. In the current project we aimed to further validate the benefits of selecting beef cattle for immune competence, realised through reduced health associated disease and mortalities, in an Australian commercial feedlot environment.
Objectives
The main objective of this project was to further validate the benefits of selecting beef cattle for immune competence in Australian commercial feedlot environments.
Specific key objectives of the project were:
• to further assess the benefits of genetic selection for immune competence, realised through reduced health-associated disease and mortalities, in higher disease risk environments than animals were exposed to in previous MLA project, B.STU.0244
• to generate additional immune competence phenotype data to be used in future studies to improve the accuracy of genetic parameter estimates for immune competence traits in beef cattle and inform future GWAS to identify major genes associated with enhanced immune competence in beef cattle
• to further explore relationships between immune competence, other resilience-related traits including stress responsiveness and temperament, growth and carcase traits in beef cattle
• to develop a pen-side test to replace the laboratory test currently used to assess antibody-mediated immune responses as part of immune competence phenotype testing.
Key findings
• A significantly favourable association between immune competence phenotype and mortalities during feedlot finishing was observed, with steers below average for immune competence being three times more likely to die during feedlot finishing than steers above average for immune competence.
• Enhanced immune competence was associated with a reduced 'pull rate' during feedlot finishing; however, the effect was not significant.
• Immune competence phenotype was not significantly associated with number of offal defects or lung lesion scores observed at processing. However, when the number of offal defects observed was treated as a binary trait (zero or ≥1 defect detected) a trend suggesting that immune competence was unfavourably associated with offal defects being detected at processing.
• There was strong evidence to support the notion that a FAVOURABLE xx WAS associated between immune competence phenotype and weight change over weaning: however, the observed relationship was not strong.
• Immune competence phenotype was not associated with carcase traits, suggesting selection for immune competence will not compromise carcase characteristics or eating quality.
• A ‘pen-side assay’ which can be used to assess anti-body-mediated immune responses as part of immune competence phenotype testing was developed. This development will allow immune competence phenotype testing to be conducted in ‘real time’ into the future.
Benefits to industry
Results from the current study further validate the benefits of selecting beef cattle for immune competence, realised through reduced health associated disease and mortalities in Australian commercial feedlot environments. Genetic strategies aimed at improving the inherent ability of animals to cope with disease challenges experienced in their production environment, used in conjunction with effective vaccination strategies and targeted management practices to reduce exposure to pathogens, have the potential to significantly reduce disease incidence and subsequent reliance on antibiotics to treat disease in Australian feedlots. Reducing reliance on antibiotics in feedlots, while maintaining optimal animal welfare standards, will be key to maintaining consumer confidence in Australian beef products moving forward and ensuring the industries continued social license to operate.
MLA action
MLA has invested in additional work to collect immune competence data on southern multibreed cattle.
Future research
The recommendations from this project for future research include:
• Further validate the benefits of selecting for immune competence in both commercial grassfed and grainfed production systems.
• Continue to refine immune competence testing procedures to reduce testing costs and improve practicality.
• Continue to investigate additional measures of immune competence which could be incorporated into testing procedures to improve the ability of the phenotype to predict favourable health outcomes.
• Genotype animals enrolled in the current study to enable immune competence phenotype data collected here to contribute to the identification of genetic markers associated with improved immune competence and be included in reference populations to improve the accuracy of genomic predictions for immune competence in beef cattle and improve the accuracy of genomic predictions for the trait through inclusion of study animals in relevant reference populations and b) allow genetic associations (based on genomic estimated breeding values) between immune competence and other traits to be investigated.
More information
| Project manager: | Clara Bradford |
| Contact email: | reports@mla.com.au |
| Primary researcher: | CSIRO ANIMAL FOOD & HEALTH SCIENCES |
