Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista, 14884-900, Jaboticabal, São Paulo, Brazil.
J Anim Sci. 2011 Jul;89(7):2061-7. doi: 10.2527/jas.2010-3525. Epub 2011 Mar 7.
The objective of this study was to evaluate the possible use of biometric testicular traits as selection criteria for young Nellore bulls using Bayesian inference to estimate heritability coefficients and genetic correlations. Multitrait analysis was performed including 17,211 records of scrotal circumference obtained during andrological assessment (SCAND) and 15,313 records of testicular volume and shape. In addition, 50,809 records of scrotal circumference at 18 mo (SC18), used as an anchor trait, were analyzed. The (co)variance components and breeding values were estimated by Gibbs sampling using the Gibbs2F90 program under an animal model that included contemporary groups as fixed effects, age of the animal as a linear covariate, and direct additive genetic effects as random effects. Heritabilities of 0.42, 0.43, 0.31, 0.20, 0.04, 0.16, 0.15, and 0.10 were obtained for SC18, SCAND, testicular volume, testicular shape, minor defects, major defects, total defects, and satisfactory andrological evaluation, respectively. The genetic correlations between SC18 and the other traits were 0.84 (SCAND), 0.75 (testicular shape), 0.44 (testicular volume), -0.23 (minor defects), -0.16 (major defects), -0.24 (total defects), and 0.56 (satisfactory andrological evaluation). Genetic correlations of 0.94 and 0.52 were obtained between SCAND and testicular volume and shape, respectively, and of 0.52 between testicular volume and testicular shape. In addition to favorable genetic parameter estimates, SC18 was found to be the most advantageous testicular trait due to its easy measurement before andrological assessment of the animals, even though the utilization of biometric testicular traits as selection criteria was also found to be possible. In conclusion, SC18 and biometric testicular traits can be adopted as a selection criterion to improve the fertility of young Nellore bulls.
本研究旨在评估使用生物计量睾丸性状作为青年内罗尔公牛选择标准的可能性，采用贝叶斯推理估计遗传力系数和遗传相关系数。进行了多性状分析，包括 17211 个在睾丸评估（SCAND）期间获得的阴囊周长记录和 15313 个睾丸体积和形状记录。此外，还分析了 50809 个 18 月龄阴囊周长记录（SC18），用作锚定性状。使用 Gibbs2F90 程序通过动物模型进行 Gibbs 抽样估计（协）方差分量和育种值，该模型包括当代群体作为固定效应、动物年龄作为线性协变量以及直接加性遗传效应作为随机效应。SC18、SCAND、睾丸体积、睾丸形状、小缺陷、大缺陷、总缺陷和满意的睾丸评估的遗传力分别为 0.42、0.43、0.31、0.20、0.04、0.16、0.15 和 0.10。SC18 与其他性状之间的遗传相关系数分别为 0.84（SCAND）、0.75（睾丸形状）、0.44（睾丸体积）、-0.23（小缺陷）、-0.16（大缺陷）、-0.24（总缺陷）和 0.56（满意的睾丸评估）。SCAND 和睾丸体积与形状之间的遗传相关系数分别为 0.94 和 0.52，睾丸体积和形状之间的遗传相关系数为 0.52。除了有利的遗传参数估计外，SC18 被发现是最有利的睾丸性状，因为它可以在动物的睾丸评估之前进行测量，尽管还发现可以将生物计量睾丸性状用作选择标准。总之，SC18 和生物计量睾丸性状可以作为选择标准，以提高青年内罗尔公牛的繁殖力。
