The aim of this study was to estimate genetic parameters for weaning weight (WW) and udder score (US) of 186,151 Nellore animals raised in extensive systems. The (co)variance components and estimated breeding values (EBVs) were obtained by two-trait analyses using Bayesian inference. The maternal effect (ME) was expressed as the maternal additive genetic variance of the calf's weaning weight (WW). The direct heritabilities were 0.13 ± 0.012 and 0.23 ± 0.012 for WW and US, respectively. The maternal heritability was 0.11 ± 0.012 for WW. The genetic correlations between WW and US (0.48 ± 0.053), WW and ME (0.41 ± 0.067), and US and ME (0.31 ± 0.041) were positive and moderate. Cows with maternal udder scores (US_M) 3 and 4 showed higher EBVs for ME (2.58 ± 0.070 and 2.88 ± 0.214, respectively) and their progeny had higher EBVs for WW (4.58 ± 0.058 and 5.07 ± 0.168) and US (0.20 ± 0.001 and 0.26 ± 0.005). The genetic trends demonstrate genetic progress in the selection program over the years, with values of 0.19 kg and 0.01 points for WW and US, respectively. The genetic trend in ME was 0.04 kg for WW. In addition, a positive genetic correlation was observed between these traits, as well between the traits and ME, i.e., selection would result in positive genetic gains. The use of US_M may help improve body weight and udder quality in the progeny. Furthermore, the trends indicate that the selection adopted on the farms has been effective in promoting genetic progress.

这项研究的目的是评估在广泛的系统中饲养的186,151例内洛尔动物的断奶体重（WW）和乳房分数（US）的遗传参数。使用贝叶斯推断通过两性状分析获得（共）方差成分和估计的育种值（EBV）。母体效应（ME）表示为犊牛断奶体重（WW）的母体加性遗传方差。WW和US的直接遗传力分别为0.13±0.012和0.23±0.012。WW的产妇遗传力为0.11±0.012。WW和US（0.48±0.053），WW和ME（0.41±0.067），US和ME（0.31±0.041）之间的遗传相关呈正相关。母乳得分（US_M）为3和4的母牛对ME的EBV较高（分别为2.58±0.070和2.88±0.214），其后代对WW的EBV（4.58±0）。058和5.07±0.168）和美国（0.20±0.001和0.26±0.005）。遗传趋势证明了这些年来选择方案的遗传进展，WW和US的值分别为0.19 kg和0.01点。WW中ME的遗传趋势为0.04 kg。另外，在这些性状之间以及性状和ME之间观察到正的遗传相关性，即选择将导致正的遗传增益。使用US_M可能有助于改善后代的体重和乳房质量。此外，趋势表明，在农场采用的选择对促进遗传进步是有效的。WW中ME的遗传趋势为0.04 kg。另外，在这些性状之间以及在性状和ME之间观察到正的遗传相关性，即选择将导致正的遗传增益。使用US_M可能有助于改善后代的体重和乳房质量。此外，趋势表明，在农场采用的选择对促进遗传进步是有效的。WW中ME的遗传趋势为0.04 kg。另外，在这些性状之间以及在性状和ME之间观察到正的遗传相关性，即选择将导致正的遗传增益。使用US_M可能有助于改善后代的体重和乳房质量。此外，趋势表明，在农场采用的选择对促进遗传进步是有效的。