Buzanskas M E, Pires P S, Chud T C S, Bernardes P A, Rola L D, Savegnago R P, Lôbo R B, Munari D P
Departamento de Ciências Exatas, Faculdade de Ciências Agrárias e Veterinárias, UNESP-Univ Estadual Paulista, Jaboticabal, São Paulo, Brazil.
Departamento de Zootecnia, Núcleo de Pesquisa e Conservação de Cervídeos, Faculdade de Ciências Agrárias e Veterinárias, UNESP-Univ Estadual Paulista, Jaboticabal, São Paulo, Brazil.
Theriogenology. 2017 Apr 1;92:204-209. doi: 10.1016/j.theriogenology.2016.09.057. Epub 2016 Oct 6.
The aim of this study was to estimate genetic parameters for scrotal circumference at 365 (SC365) and 450 (SC450) days of age, age at first calving (AFC), ribeye area (REA), backfat (BF) thickness, and rump fat (RF) thickness, in order to provide information on potential traits for Nelore cattle breeding program. Genetic parameters were estimated using the Average Information Restricted Maximum Likelihood method in single- and multitrait analyses. Four different animal models were tested for SC365, SC450, REA, BF, and RF in single-trait analyses. For SC365 and SC450, the maternal genetic effect was statistically significant (P < 0.01) and was included for multitrait analyses. The direct heritability estimates for SC365, SC450, AFC, REA, BF, and RF were equal to 0.31, 0.38, 0.24, 0.32, 0.16, and 0.19, respectively. Maternal heritability for SC365 and SC450 was equal to 0.06 and 0.08, respectively. The highest genetic correlations were found among the scrotal circumferences. Testing for the inclusion of maternal effects in genetic parameters estimation for scrotal circumference should be evaluated in the Nelore breeding program, mostly for correctly ranking the animal's estimated breeding values. Similar heritability estimates were observed for scrotal circumference, as well as favorable genetic correlations of this trait with AFC and carcass traits. Thus, scrotal circumference measured at 365 days of age could be a target trait for consideration in the Nelore selection index in order to improve most of the traits herein analyzed.
本研究的目的是估计365日龄（SC365）和450日龄（SC450）时的阴囊周长、初产年龄（AFC）、眼肌面积（REA）、背膘（BF）厚度和臀脂（RF）厚度的遗传参数，以便为内洛尔牛育种计划提供潜在性状的相关信息。在单性状和多性状分析中，使用平均信息约束最大似然法估计遗传参数。在单性状分析中，对SC365、SC450、REA、BF和RF测试了四种不同的动物模型。对于SC365和SC450，母体遗传效应具有统计学意义（P < 0.01），并纳入多性状分析。SC365、SC450、AFC、REA、BF和RF的直接遗传力估计值分别为0.31、0.38、0.24、0.32、0.16和0.19。SC365和SC450的母体遗传力分别为0.06和0.08。阴囊周长之间的遗传相关性最高。在内洛尔牛育种计划中，应评估在阴囊周长遗传参数估计中纳入母体效应的测试，主要是为了正确排列动物的估计育种值。观察到阴囊周长的遗传力估计值相似，以及该性状与AFC和胴体性状的有利遗传相关性。因此，365日龄时测量的阴囊周长可能是内洛尔牛选择指数中考虑的目标性状，以便改善本文分析的大多数性状。
