Shepard H H, Green R D, Golden B L, Hamlin K E, Perkins T L, Diles J B
Department of Animal Science and Food Technology, Texas Tech University, Lubbock 79409-2162, USA.
J Anim Sci. 1996 Apr;74(4):761-8. doi: 10.2527/1996.744761x.
Ultrasonic measures of backfat thickness (BFT) and longissimus muscle area (LMA) taken on Angus bulls (n = 805) and heifers (n = 877) ranging in age from approximately 8 to 20 mo in a production setting in western Nebraska were used to estimate genetic (co)variances. Further information used in the analyses, including weaning weight (WWT), postweaning ADG, and scrotal circumference (SC), was obtained from the American Angus Association, St. Joseph, MO, for these individuals and for animals from the same herd and contemporary groups. Data were analyzed using single-trait, sire model, restricted maximum likelihood (REML) procedures to estimate starting variances for later two-trait analyses. These two-trait analyses were done to estimate variance components for WWT coupled with BFT, LMA, SC, and ADG, also using REML procedures, but with a sire-maternal grandsire model for WWT and a sire model for the other trait(s). Heritabilities for BFT, LMA, WWT direct, WWT maternal, SC, and ADG were .56, .11, .19, .24, .56, and .51, respectively. Genetic correlations between WWT direct and WWT maternal, WWT direct and LMA, WWT maternal and LMA, WWT maternal and BFT were -.57, .42, .01, and -.69, respectively. Genetic parameters from this study were used to calculate possible genetic change with a typical selection scenario, and it was shown that among WWT, BFT, and LMA, BFT could be affected the most by selection, relative to its mean.
在内布拉斯加州西部的一个生产环境中，对805头安格斯公牛和877头安格斯小母牛（年龄约8至20个月）进行了背膘厚度（BFT）和最长肌面积（LMA）的超声测量，以估计遗传（协）方差。分析中使用的进一步信息，包括断奶体重（WWT）、断奶后平均日增重（ADG）和阴囊周长（SC），是从密苏里州圣约瑟夫市的美国安格斯协会获得的，这些信息涉及这些个体以及来自同一牛群和同期组的动物。使用单性状、父系模型、限制最大似然法（REML）程序分析数据，以估计后续双性状分析的起始方差。这些双性状分析旨在估计WWT与BFT、LMA、SC和ADG的方差分量，同样使用REML程序，但WWT采用父系-母系祖父模型，其他性状采用父系模型。BFT、LMA、直接WWT、母系WWT、SC和ADG的遗传力分别为0.56、0.11、0.19、0.24、0.56和0.51。直接WWT与母系WWT、直接WWT与LMA、母系WWT与LMA、母系WWT与BFT之间的遗传相关性分别为-0.57、0.42、0.01和-0.69。本研究的遗传参数用于计算典型选择方案下可能的遗传变化，结果表明，在WWT、BFT和LMA中，相对于其均值，BFT受选择的影响可能最大。
