Genetic evaluation of longevity in Australian Angus cattle using random regression models

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Beef Cattle Production

Background:

• Cow longevity is crucial for beef industry profitability and sustainability.
• Early selection for longevity is challenging as true longevity is unknown until the end of a cow's life.

Purpose of the Study:

• Estimate variance components and genetic parameters for traditional longevity (TL) and functional longevity (FL) in Australian Angus cattle.
• Investigate the impact of censored data on estimated breeding values (EBV) of bulls.

Main Methods:

• Applied a single-trait random regression model using a Bayesian Gibbs sampler.
• Analyzed five datasets based on different culling reasons for ages 2 to 11 years.
• Evaluated the impact of excluding censored data on sire EBVs.

Main Results:

• Heritability estimates for TL and FL were generally low (0.02–0.20), peaking between ages 4–6 years.
• Genetic correlations between early and late life longevity were low, indicating they are not the same genetic trait.
• Excluding censored data underestimated sire EBVs, with a larger negative impact on younger sires.

Conclusions:

• Additive genetic factors significantly contribute to longevity variability in Australian Angus cattle.
• Genetic improvement of longevity is achievable by incorporating it into long-term breeding objectives.
• Accurate genetic evaluation requires accounting for censored data in longevity analyses.