Department of Animal Science, Iowa State University, Ames, Iowa 50011, USA.
J Anim Sci. 2012 Jan;90(1):127-41. doi: 10.2527/jas.2011-4293. Epub 2011 Aug 26.
Gompertz growth functions were fitted to longitudinal measurements of daily feed intake (DFI) and BW of 586 boars and 495 gilts from a selection experiment in Yorkshire pigs for residual feed intake (RFI). The selection experiment consists of a line selected for low residual feed intake (LRFI) for 5 generations and a randomly selected control line (CTRL). The objectives of this study were to use Bayesian methods to estimate genetic parameters of the Gompertz curve parameters for DFI and BW, to evaluate the effect of selection for reduced RFI on the Gompertz parameters and shape of curves for DFI and BW, and to develop methodology for quantifying genetic variation at the level of the original phenotypes for DFI and BW based on the Bayesian analysis of the nonlinear model. Separate analyses were done for boars and gilts and for BW and DFI. A hierarchical model was specified in 2 levels: in the first level, the Gompertz function was modeled for each pig, and at the second level, a 3-trait linear mixed model was fitted to the 3 Gompertz parameters (asymptotic value, inflection point, and decay parameter), with fixed effects of line by generation and random effects of additive genetic and environmental effects. Bayesian methods were used to combine the 2 levels of modeling. A total of 30,000 random samples of the posterior distributions after convergence of Markov chains were used for inference. Posterior means of heritability within the first level of the model for the asymptotic value, inflection point, and decay parameter for DFI were 0.74, 0.66, and 0.82 for boars and 0.79, 0.70, and 0.57 for gilts; corresponding estimates for BW were 0.64, 0.58, and 0.60 for boars and 0.46, 0.35, and 0.33 for gilts. For DFI, LRFI boars had a reduced mature DFI (2.91 vs. 3.20 kg/d) and an earlier inflection point (85 vs. 95 d) compared with CTRL boars. For BW, LRFI boars had a lighter mature BW (279 vs. 317 kg), an earlier inflection point (184 vs. 198 d), and a decreased decay parameter (127 vs. 134 d) compared with CTRL boars. In contrast, LRFI gilts had a later inflection point (225 vs. 200 d) and a greater decay parameter (172 vs. 143 d) than CTRL gilts for BW. The other Gompertz curve parameters for DFI and BW for boars and gilts were considered not different between lines, with posterior probabilities of the line differences being greater than zero ranging from 0.1 to 0.9.
我们为残余采食量（RFI）选择试验中的 586 头公猪和 495 头母猪拟合了戈梅茨生长函数，以进行每日采食量（DFI）和体重（BW）的纵向测量。选择试验包括为低残余采食量（LRFI）选择的 5 个世代的品系和随机选择的对照系（CTRL）。本研究的目的是使用贝叶斯方法估计 DFI 和 BW 的戈梅茨曲线参数的遗传参数，评估减少 RFI 选择对 DFI 和 BW 的戈梅茨参数和曲线形状的影响，并开发基于 DFI 和 BW 的非线性模型贝叶斯分析的原始表型水平上遗传变异的定量方法。为 BW 和 DFI 分别对公猪和母猪进行了单独的分析。在 2 个水平上指定了分层模型：在第一个水平上，为每头猪建模戈梅茨函数，在第二个水平上，拟合 3 个性状线性混合模型来拟合 3 个戈梅茨参数（渐近值、拐点和衰减参数），具有世代的线性固定效应和加性遗传和环境效应的随机效应。使用贝叶斯方法来组合 2 个水平的建模。在马尔可夫链收敛后，共使用 30,000 个后验分布的随机样本进行推断。模型第一级渐近值、拐点和衰减参数的遗传力后验均值为 DFI 公猪 0.74、0.66 和 0.82，母猪 0.79、0.70 和 0.57；BW 公猪 0.64、0.58 和 0.60，母猪 0.46、0.35 和 0.33。对于 DFI，与 CTRL 公猪相比，LRFI 公猪的成熟 DFI（2.91 公斤/天对 3.20 公斤/天）和拐点（85 天对 95 天）更早。对于 BW，LRFI 公猪的成熟 BW 较轻（279 公斤对 317 公斤），拐点较早（184 天对 198 天），衰减参数较低（127 天对 134 天）与 CTRL 公猪相比。相比之下，LRFI 母猪的拐点（225 天对 200 天）和衰减参数（172 天对 143 天）大于 CTRL 母猪的 BW。对于公猪和母猪的 DFI 和 BW 的其他戈梅茨曲线参数，线间差异被认为没有差异，线差异的后验概率大于 0 的范围为 0.1 到 0.9。
