摘要
The objective of this study was to estimate the breed, heterosis, and recombination effects on different components of the lactation curve of Girolando cattle. The dataset used consisted of 12,121 purebred cows of Holstein (H) and Gyr (G) breeds, and six H×G crossbred cows (Girolando). The model used presents random effects of herd and cow, regression coefficient associated with linear effect of proportion of H breed, regression coefficient associated with the linear effect of heterosis between H and G breeds, regression coefficient associated with the linear effect of recombination between H and G breeds, and random effect of residual. Dijkstra's (DJ), Nelder's (ND), Wilmink's (WL), and Wood's (WD) models were tested to fit production records of these different genetic groups. These models were then tested according to evaluation criteria of quality of fit (AIC, BIC, and RMSE), and the two best models (WD and WL) were chosen for estimation of 305-day milk yield (MY305), peak yield, time to peak, and persistency of milk yield. The breed effect was significant for all traits and components of the lactation curve. The heterosis effect was significant for all traits, and was more significant for MY305 (945.62±79.17 kg). Peak yield was the component of lactation curve that presented the most significant heterosis effect, partially explaining the heterosis effect (12 to 21%) found for MY305. The recombination effect was positive only for lactation period and time to peak of lactation in Girolando cows.
摘要译文
这项研究的目的是评估吉罗兰多牛泌乳曲线不同组成部分的繁殖，杂种优势和重组效应。使用的数据集由12121头荷斯坦（H）和吉尔（Gyr）品种的纯种奶牛和六只H×G杂交奶牛（Girolando）组成。使用的模型显示了牛群和母牛的随机效应，与H品种比例的线性效应相关的回归系数，与H和G品种之间的杂种优势的线性效应相关的回归系数，与H和G重组之间的线性效应相关的回归系数G品种，并有残留的随机效应。对Dijkstra（DJ），Nelder（ND），Wilmink（WL）和Wood（WD）模型进行了测试，以适合这些不同基因组的生产记录。然后根据拟合质量的评估标准（AIC，BIC和RMSE）对这些模型进行测试，并选择了两个最佳模型（WD和WL）来估算305天的产奶量（MY305），峰值产量，时间达到峰值，以及牛奶产量的持久性。对于泌乳曲线的所有特征和组成，育种效果都很显着。杂种优势对所有性状均显着，对MY305（945.62±79.17 kg）更为显着。峰值产量是泌乳曲线的组成部分，表现出最显着的杂种优势，部分解释了MY305的杂种优势（12％至21％）。重组作用仅在泌乳期和泌乳高峰期的鸡中是阳性的。
DALTRO; Darlene dos Santos et al.. Breed, heterosis, and recombination effects for lactation curves in Brazilian cattle.[J]. Revista Brasileira de Zootecnia, 2021,50(50)