Mulim Henrique Alberto, Pinto Luis Fernando Batista, Valloto Altair Antônio, Pedrosa Victor Breno
Department of Animal Science, State University of Ponta Grossa, Ponta Grossa, PR, 84030-900, Brazil.
Department of Animal Science, Federal University of Bahia, Salvador, BA, 40170-115, Brazil.
Anim Biosci. 2021 Apr;34(4):499-505. doi: 10.5713/ajas.20.0031. Epub 2020 May 12.
The objective of this study was to evaluate the genetic behavior of a population of Holstein cattle in response to the variation of environmental temperature by analyzing the effects of genotype by environment interaction (GEI) through reaction norms for the somatic cell score (SCS).
Data was collected for 67,206 primiparous cows from the database of the Paraná Holstein Breeders Association in Brazil, with the aim of evaluating the temperature effect, considered as an environmental variable, distinguished under six gradients, with the variation range found being 17°C to 19.5°C, over the region. A reaction norm model was adopted utilizing the fourth order under the Legendre polynomials, using the mixed models of analysis by the restricted maximum likelihood method by the WOMBAT software. Additionally, the genetic behavior of the 15 most representative bulls was assessed, in response to the changes in the temperature gradient.
A mean score of 2.66 and a heritability variation from 0.17 to 0.23 was found in the regional temperature increase. The correlation between the environmental gradients proved to be higher than 0.80. Distinctive genetic behaviors were observed according to the increase in regional temperature, with an observed increase of up to 0.258 in the breeding values of some animals, as well as a reduction in the breeding of up to 0.793, with occasional reclassifications being observed as the temperature increased.
Non-relevant GEI for SCS were observed in Holstein cattle herds of southern Brazil. Thus, the inclusion of the temperature effect in the model of genetic evaluation of SCS for the southern Brazilian Holstein breed is not required.
本研究的目的是通过分析体细胞评分（SCS）反应规范中的基因型与环境互作（GEI）效应，评估荷斯坦奶牛群体对环境温度变化的遗传行为。
从巴西巴拉那荷斯坦育种者协会的数据库中收集了67206头初产奶牛的数据，旨在评估温度效应（作为环境变量），该变量在六个梯度下区分，该地区的变化范围为17°C至19.5°C。采用反应规范模型，利用勒让德多项式的四阶模型，通过WOMBAT软件的限制最大似然法进行混合模型分析。此外，评估了15头最具代表性公牛对温度梯度变化的遗传行为。
在区域温度升高时，平均评分为2.66，遗传力变化范围为0.17至0.23。环境梯度之间的相关性证明高于0.80。根据区域温度升高观察到不同的遗传行为，一些动物的育种值观察到高达0.258的增加，以及高达0.793的育种减少，随着温度升高偶尔会观察到重新分类。
在巴西南部的荷斯坦牛群中未观察到与SCS相关的GEI。因此，在巴西南部荷斯坦品种的SCS遗传评估模型中不需要纳入温度效应。
