Toghiani S, Hay E, Fragomeni B, Rekaya R, Roberts A J
USDA Agricultural Research Service, Fort Keogh Livestock and Range Research Laboratory, Miles City, MT59301, USA.
Department of Animal Science, University of Connecticut, Storrs, CT06269, USA.
Animal. 2020;14(8):1576-1587. doi: 10.1017/S1751731120000531. Epub 2020 Mar 31.
Extreme weather conditions such as cold stress influence the productivity and survivability of beef cattle raised on pasture. The objective of this study was 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 modelled as the accumulation of total cold load (TCL) calculated using the Comprehensive Climate Index units, considering three TCL classes defined based on temperature: less than -5°C (TCL5), -15°C (TCL15) and -25°C (TCL25). A total of 4221 and 4217 records for BW and WW, respectively, were used from a composite beef cattle population (50% Red Angus, 25% Charolais and 25% Tarentaise) between 2002 and 2015. For both BW and WW, a univariate model (ignoring cold stress) and a reaction norm model were implemented. 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 of top bulls (n = 79) using univariate and reaction norm models across TCL classes showed some re-ranking in direct and maternal effects for both BW and WW particularly for TCL5 and TCL15. In general, cold stress did not have a big impact on direct and maternal genetic effects of BW and WW.
寒冷应激等极端天气条件会影响牧场饲养的肉牛的生产力和存活率。本研究的目的是确定并评估在一个复合肉牛群体中，由于寒冷应激导致的基因型与环境互作对出生体重（BW）和断奶体重（WW）的影响程度。寒冷应激的影响被建模为使用综合气候指数单位计算的总冷负荷（TCL）的累积，考虑根据温度定义的三个TCL类别：低于-5°C（TCL5）、-15°C（TCL15）和-25°C（TCL25）。分别从2002年至2015年的一个复合肉牛群体（50%红安格斯、25%夏洛来和25%塔兰泰拉）中使用了总共4221条BW记录和4217条WW记录。对于BW和WW，分别实施了一个单变量模型（忽略寒冷应激）和一个反应规范模型。随着冷负荷增加，TCL5类别的BW和WW的直接遗传力略有增加；然而，在TCL25类别的冷负荷范围内，这种遗传力保持一致。相比之下，BW的母体遗传力在所有TCL类别中随着冷负荷增加而保持不变，尽管在TCL5和TCL15类别中观察到母体遗传力略有增加。所有TCL类别之间不同冷负荷下BW的直接和母体遗传相关性以及WW的母体遗传相关性都很高（r>0.99），而WW观察到的最低直接遗传相关性在TCL5时为0.88，在TCL15时为0.85。使用单变量和反应规范模型在TCL类别中对顶级公牛（n = 79）的估计育种值之间的斯皮尔曼等级相关性显示，对于BW和WW，特别是对于TCL5和TCL15，在直接和母体效应方面有一些重新排名。总体而言，寒冷应激对BW和WW的直接和母体遗传效应影响不大。
