Lopes Fernando Brito, Magnabosco Cláudio Ulhôa, Paulini Fernanda, da Silva Marcelo Corrêa, Miyagi Eliane Sayuri, Lôbo Raysildo Barbosa
Embrapa Cerrados/Capes, Goiânia, Goiás, Brazil.
PLoS One. 2013 Sep 10;8(9):e75423. doi: 10.1371/journal.pone.0075423. eCollection 2013.
Components of (co)variance and genetic parameters were estimated for adjusted weights at ages 120 (W120), 240 (W240), 365 (W365) and 450 (W450) days of Polled Nellore cattle raised on pasture and born between 1987 and 2010. Analyses were performed using an animal model, considering fixed effects: herd-year-season of birth and calf sex as contemporary groups and the age of cow as a covariate. Gibbs Samplers were used to estimate (co)variance components, genetic parameters and additive genetic effects, which accounted for great proportion of total variation in these traits. High direct heritability estimates for the growth traits were revealed and presented mean 0.43, 0.61, 0.72 and 0.67 for W120, W240, W365 and W450, respectively. Maternal heritabilities were 0.07 and 0.08 for W120 and W240, respectively. Direct additive genetic correlations between the weight at 120, 240, 365 and 450 days old were strong and positive. These estimates ranged from 0.68 to 0.98. Direct-maternal genetic correlations were negative for W120 and W240. The estimates ranged from -0.31 to -0.54. Estimates of maternal heritability ranged from 0.056 to 0.092 for W120 and from 0.064 to 0.096 for W240. This study showed that genetic progress is possible for the growth traits we studied, which is a novel and favorable indicator for an upcoming and promising Polled Zebu breed in Tropical regions. Maternal effects influenced the performance of weight at 120 and 240 days old. These effects should be taken into account in genetic analyses of growth traits by fitting them as a genetic or a permanent environmental effect, or even both. In general, due to a medium-high estimate of environmental (co)variance components, management and feeding conditions for Polled Nellore raised at pasture in tropical regions of Brazil needs improvement and growth performance can be enhanced.
对1987年至2010年间出生、在牧场饲养的无角内罗牛在120日龄（W120）、240日龄（W240）、365日龄（W365）和450日龄（W450）时的校正体重的（协）方差成分和遗传参数进行了估计。使用动物模型进行分析，考虑固定效应：出生的畜群-年份-季节和犊牛性别作为当代组，母牛年龄作为协变量。使用吉布斯采样器估计（协）方差成分、遗传参数和加性遗传效应，这些因素在这些性状的总变异中占很大比例。生长性状的直接遗传力估计值较高，W120、W240、W365和W450的平均直接遗传力分别为0.43、0.61、0.72和0.67。W120和W240的母体遗传力分别为0.07和0.08。120日龄、240日龄、365日龄和450日龄体重之间的直接加性遗传相关性很强且为正。这些估计值范围从0.68到0.98。W120和W240的直接-母体遗传相关性为负。估计值范围从-0.31到-0.54。W120的母体遗传力估计值范围从0.056到0.092，W240的母体遗传力估计值范围从0.064到0.096。本研究表明，对于我们研究的生长性状，遗传进展是可能的，这对于热带地区一个即将出现且有前景的无角瘤牛品种来说是一个新颖且有利的指标。母体效应影响120日龄和240日龄体重的表现。在生长性状的遗传分析中，应将这些效应作为遗传效应或永久环境效应，甚至两者都考虑在内。总体而言，由于环境（协）方差成分的估计值中等偏高，巴西热带地区牧场饲养的无角内罗牛的管理和饲养条件需要改善，生长性能可以提高。
