Shiotsuki L, Silva J A V, Tonhati H, Albuquerque L G
Faculdade de Ciências Agrárias e Veterinárias, São Paulo State University, 14884-000, Jaboticabal, São Paulo, Brazil.
J Anim Sci. 2009 May;87(5):1591-7. doi: 10.2527/jas.2008-1173. Epub 2008 Dec 19.
The objective of this study was to determine the possible use of heifer pregnancy at 16 mo as a selection criterion and its possible genetic associations with hip height, yearling weight, and visual scores of conformation, finishing, and muscling. The data set contained records of 56,458 Nelore yearlings for the traits described above. Covariance components were estimated by bivariate animal models assuming a linear model for hip height, yearling weight and conformation, and finishing and muscling scores, and a nonlinear (threshold) model for heifer pregnancy. Variance components were estimated using Bayesian inference. Flat distributions were used for all (co)variance components and genetic correlations. The first 5,000 rounds were considered as the burn-in period and discarded. The heritability estimate of heifer pregnancy indicates that the trait can be used as a selection criterion. Long-term selection for heifer pregnancy will result in a reduction of animal height. However, selection for increasing yearling weight should be possible in this population of Nelore cattle without having major effects on fertility. Selection for increasing visual scores of conformation, finishing, and muscling will result in small or no response in heifer pregnancy at 16 mo.
本研究的目的是确定16月龄小母牛怀孕情况作为选择标准的可能用途，以及它与体高、周岁体重以及体型、育肥和肌肉的视觉评分之间可能的遗传关联。数据集包含了56458头内罗尔牛周岁犊牛上述性状的记录。通过双变量动物模型估计协方差分量，其中体高、周岁体重和体型以及育肥和肌肉评分采用线性模型，小母牛怀孕情况采用非线性（阈值）模型。使用贝叶斯推断估计方差分量。对所有（协）方差分量和遗传相关性使用平坦分布。前5000轮被视为预热期并舍弃。小母牛怀孕情况的遗传力估计表明该性状可作为选择标准。长期选择小母牛怀孕情况将导致动物身高降低。然而，在这群内罗尔牛中选择增加周岁体重应该是可行的，且对繁殖力没有重大影响。选择增加体型、育肥和肌肉的视觉评分，在16月龄时小母牛怀孕情况的反应很小或没有反应。
