The objectives of this work were to evaluate how population genetic and phenotypic components for dry matter intake and respiration rate in beef cattle changed as a function of temperature humidity index, to determine whether genotype-by-environment interactions (G × E) influenced selection decisions when breeding values (BV) were sourced from disparate environments, and to evaluate model-derived accuracy of BV at specific values of the temperature humidity index. Results indicate that selection for stable performance in both traits may be possible, though at the expense of overall performance at the onset of heat stress. Furthermore, the magnitude of the additive genetic variance available for selection decreased as the temperature humidity increased, indicating that the potential for selection progress for dry matter intake is slower under extreme temperature humidity index conditions. Genetic re-ranking of animals based on estimated dry matter intake BV for different environments was evident. This finding indicated that the optimal animal for selection may change depending on the environment. Similarly, an estimated BV may not reflect performance in different environments if G × E is not considered.

Read the full article in the Journal of Animal Science.