Abstract The experiments reported in this research paper were aimed at assessing the genetic responses of a Holstein cow population, as a response to the variations in environmental temperature, through the analysis of the effects resulting from the genotype by environment interaction (GEI), based on reaction norms. Therefore, milk production data was collected from the database of the Paraná Holstein Breeders Association in Brazil for 67,360 primiparous cows born between 1990 and 2015, with the purpose of evaluating the temperature effect, considered as an environmental variable, distinguished under six gradients (17 ºC to 19.5 ºC) over the region. A random regression model was adopted, utilizing the fourth order under the Legendre polynomials, applying the mixed models of analysis by the REML method, and using the WOMBAT software. Additionally, the breeding value of the 15 most representative bulls was assessed, in response to the changes in the temperature gradient. The total milk production on average was estimated at 8,412.83 ± 2,012.08 kg. The heritabilities estimates were found in the low to moderate range, from 0.18 to 0.23, displaying a decline with a rise in the temperature, highlighting the influence it exerted on the heritabilities. Variations in the genetic expression of some bulls were noted to show differences of up to 289 kg of milk in response to the increase in the temperature from 17 ºC to 19.5 ºC. However, all the genetic correlations between the gradients for milk yield were above 0.80, in the range of 0.873 to 0.998, revealing no remarkable interaction between the genotype and environment. This result indicates that the application of the temperature variable in the models of genetic analysis in southern Brazil is not required.

中文翻译：

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通过环境相互作用通过巴西南部荷斯坦牛产奶量的反应规范评估基因型

摘要 本研究论文中报告的实验旨在评估荷斯坦奶牛种群的遗传反应，作为对环境温度变化的反应，通过分析环境相互作用 (GEI) 基因型产生的影响，基于反应规范。因此，从巴西巴拉那荷斯坦育种者协会的数据库中收集了 1990 年至 2015 年间出生的 67,360 头初产奶牛的产奶数据，目的是评估温度效应，该效应被视为环境变量，在六个梯度（17 ºC到 19.5 ºC）在该地区。采用随机回归模型，利用勒让德多项式下的四阶，应用REML方法的混合分析模型，并使用WOMBAT软件。此外，根据温度梯度的变化，对 15 只最具代表性的公牛的育种价值进行了评估。平均总产奶量估计为 8,412.83 ± 2,012.08 kg。遗传力估计值在低到中等范围内，从 0.18 到 0.23，随着温度的升高而下降，突出了它对遗传力的影响。一些公牛的基因表达变化被注意到，随着温度从 17 ºC 升高到 19.5 ºC，牛奶的差异高达 289 公斤。然而，产奶量梯度之间的所有遗传相关性都在0.80以上，范围在0.873到0.998之间，表明基因型与环境之间没有显着的相互作用。