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首页> 外文期刊>Livestock Science >Improvement of lactation milk and persistency using the eigenvectors of the genetic covariance matrix between lactation stages
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Improvement of lactation milk and persistency using the eigenvectors of the genetic covariance matrix between lactation stages

机译：在哺乳阶段之间使用遗传协方差矩阵的特征向量改善泌乳和持久性

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First lactation milk production of Japanese Holstein cows was partitioned into ten stages. A quartic Legendre polynomial (k=S) under an animal model was used to estimate the additive genetic covariance matrix between these ten stages. Various selection indexes with or without restrictions were constructed using the eigenvectors of the genetic covariance matrix. These eigen indexes were designed to improve lactation milk and persistency defined as difference in milk between DIM 280 and DIM 55. Two sets of economic weights between lactation milk and persistency and three levels of restriction on the intended gains in persistency were applied. The unrestricted index based on the first three eigenvectors achieved more than 99.9% of the net merit of theunrestricted index based on the first five eigenvectors. The advantage of unrestricted index over conventional selectiontoased on lactation EBV increases with increasing economic weight assigned to persistency. The construction of the restricted eigen index does not require economic values between lactation milk and persistency and thus is more practical than the unrestricted eigen index which requires information on the economic values of both. The index coefficients of the eigen indexes reveal the relative selection emphasis among various stages of the lactation. When the degree of restriction or economic value for persistency increases, a greater selection emphasis was placed on the later part of the lactation than on the early part in order to realize the desired persistency. The developed eigen indexes provide useful information and easy understanding of the selection practice. A numerical example was given to illustrate the construction of the restricted eigen index.
机译：日本荷斯坦奶牛的第一次泌乳生产分为十个阶段。动物模型下的四次Legendre多项式（k = S）用于估计这十个阶段之间的加性遗传协方差矩阵。使用遗传协方差矩阵的特征向量构建各种选择索引，无论有无限制。这些本征指标旨在改善泌乳期和持久性，定义为DIM 280和DIM 55之间的乳汁差异。应用了两组泌乳期和持久性之间的经济权重，以及对预期持久性收益的三个限制级别。基于前三个特征向量的无限制索引实现了基于前五个特征向量的无限制索引的净优点的99.9％以上。相对于常规选择，无限制指标的优势在于哺乳期EBV随持久性分配的经济权重的增加而增加。限制性本征指数的构建不需要泌乳和持久性之间的经济价值，因此比非限制性本征指数更实用，后者需要有关两者的经济价值的信息。本征指标的指标系数揭示了泌乳各个阶段之间的相对选择重点。当对持久性的限制程度或经济价值增加时，为了实现所需的持久性，与早期相比，对哺乳后期的选择重点更大。已开发的特征索引可提供有用的信息，并易于理解选择实践。给出了一个数值例子来说明受限特征指数的构造。

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