Submitted to: Animal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2020
Publication Date: 3/31/2020
Citation: Toghiani, S., Hay, E.A., Fragomeni, B., Rekaya, R., Roberts, A.J. 2020. Genotype by environment interaction in response to cold stress in a composite beef cattle breed. Animal. 1-12. https://doi.org/10.1017/S1751731120000531.
DOI: https://doi.org/10.1017/S1751731120000531

Interpretive Summary: Cold stress negatively impacts the overall productivity of beef cattle production and might affect the genetic basis of cattle’s performance. The existence of genotype-by-environment interaction effects due to cold stress on growth traits were evaluated in a composite beef cattle population. To measure the effect of cold stress, a comprehensive climate index was used to create three different cold load classes. Some evidence of environmental sensitivity of animals across different cold load classes was observed. Additionally, little change in re-ranking of superior bulls was observed for the direct and maternal breeding values of growth traits. Generally, there was a little impact of cold stress on growth-related traits due to the potential adaptation of this cattle population to the cold environment.

Technical Abstract: Extreme weather conditions such as cold stress influence the productivity and survivability of beef cattle raised on pasture. The objective of this study is to identify and evaluate the extent of the impact of genotype by environment interaction due to cold stress on birth weight (BW) and weaning weight (WW) in a composite beef cattle population. The effect of cold stress was modeled as the accumulation of total cold load (TCL) calculated using the comprehensive climate index (CCI) units, and three TCL classes were defined based on temperature: less than -5°C (TCL5), -15°C (TCL15) and -25°C (TCL25). A total of 4,221 and 4,217 records for BW and WW respectively were used in both a univariate model (ignoring cold stress) and a reaction norm model. As cold load increased, the direct heritability slightly increased in both BW and WW for TCL5 class. However, this heritability remained consistent across the cold load of TCL25 class. In contrast, the maternal heritability of BW was constant with cold load increase in all TCL classes, although a slight increase of maternal heritability was observed for TCL5 and TCL15. The direct and maternal genetic correlation for BW and maternal genetic correlation for WW across different cold loads between all TCL classes were high (r >0.99), whereas the lowest direct genetic correlations observed for WW were 0.88 for TCL5 and 0.85 for TCL15. The Spearman rank correlation between the estimated breeding value (EBV) of top bulls (n=79) using univariate and reaction norm models across TCL classes showed some reranking in direct and maternal effects for both BW and WW particularly for TCL5 and TCL15. In general, cold stress did not have as big of an impact on direct and maternal genetic effects of birth and weaning weight.