Genotype x Environment Interaction for reproductive traits in brazilian Nellore breed cattle

SUMMARY The objective of this study was to evaluate the effect of the genotype-environment interaction (GEI) for scrotal circumference traits measured at different ages, 365 (SC365), 450 (SC450) and 550 (SC550) days of age, and age at first calving (AFC) for Nellore animals raised in different regions of Brazil. For the evaluation, the herds were grouped in the following regions of the country: North, Southeast and Central-west, using information from 26,619, 28,730, 14,476, 15,397 for the traits SC365, SC450, SC550 and AFC respectively. Genetic parameters, as well as the assessment of GEI were performed using Bayesian inference, using the programs of the BLUPF90. The estimated heritabilities were: 0.465 ± 0.021, 0.500 ± 0.022, 0.492 ± 0.026, 0.117 ± 0.017 for SC365, SC450, SC550 and AFC respectively. The results obtained in the analysis, indicated that this interaction was not significant for SC at different ages (genetic correlation, rg> 0.8). For AFC, significant effect of GEI was observed for combinations involving the Northern region (rg<0.8), indicating that this interaction should be considered by the genetic evaluation programs in this region.

摘要：本研究旨在评估基因型-环境互作（genotype-environment interaction, GEI）对巴西不同地区饲养的内洛尔牛（Nellore）不同日龄（365日龄（SC365）、450日龄（SC450）和550日龄（SC550））的阴囊周径性状，以及首次产犊日龄（age at first calving, AFC）的影响。本次评估将牛群按该国北部、东南部和中西部区域分组，所用SC365、SC450、SC550及AFC性状的样本量分别为26619、28730、14476及15397。遗传参数评估及基因型-环境互作分析采用贝叶斯推断法，并借助BLUPF90程序完成。各性状的估计遗传力分别为：SC365：0.465±0.021，SC450：0.500±0.022，SC550：0.492±0.026，AFC：0.117±0.017。分析结果显示，不同日龄阴囊周径的基因型-环境互作并不显著（遗传相关系数rg>0.8）。对于首次产犊日龄，在涉及北部区域的组合中观测到显著的GEI效应（rg<0.8），表明该区域的遗传评估程序应考虑此互作效应。