Genotype by environment interactions for growth in Red Angus

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Reproductive Biology

Background:

• Accurate sire selection in livestock is crucial for genetic improvement.
• Environmental factors significantly influence animal performance, complicating selection decisions.
• Understanding genotype × environment interactions (G×E) is vital for optimizing breeding strategies.

Purpose of the Study:

• To evaluate G×E for birth weight (BiW) and weaning weight (WW) in Red Angus cattle within the United States.
• To assess sire performance stability across different environmental regions.
• To quantify the extent of genetic correlations between different environmental conditions.

Main Methods:

• Defined nine US regions based on temperature-humidity indices as distinct environments.
• Estimated reaction norms (RN) for individual sires using sire progeny means regressed on regional means.
• Calculated genetic correlations between BiW and WW across all region pairs.

Main Results:

• Heritability estimates for BiW and WW RN were 0.40 and 0.39, respectively.
• Phenotypic and genetic correlations between BiW and WW RN were 0.19 and 0.54.
• Few instances of significant G×E were detected (2/36 for BiW, 12/36 for WW), with most genetic correlations between regions exceeding 0.80.

Conclusions:

• Red Angus sires generally exhibit consistent ranking for BiW and WW across different US environmental regions.
• G×E for BiW and WW in this population does not appear to be a major limitation for sire selection.
• The findings support the use of current selection methods while acknowledging the need for continued environmental characterization.