Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, PO Box 5003, N-1432 Ås, Norway.
J Dairy Sci. 2013 Jun;96(6):3973-85. doi: 10.3168/jds.2012-5972. Epub 2013 Mar 30.
Fourier transform infrared (FTIR) spectroscopy is often used in prediction of major milk components in genetic evaluation of dairy animals. Until now genetic variability of goat milk FTIR spectra has only been known indirectly through their contribution to the major milk components. In this study, genetic and environmental components of goat milk FTIR spectra were examined directly. A data set containing 83,858 milk FTIR spectral observations belonging to 29,320 Norwegian dairy goats of 271 herds was used for the study. Principal components analysis was applied on both unprocessed and preprocessed spectral data, and new traits (latent traits) were defined because a multitrait analysis of all spectral variables for variance components could not be done. Eight and 7 latent variables, explaining approximately 99% of the total unprocessed and preprocessed spectral variation, respectively, were kept from the principal components analysis for genetic analysis. Genetic and environmental variance components were estimated for the latent traits using restricted maximum likelihood. Genetic-to-total phenotypic variance ratios (heritabilities) of the latent traits were between 0.011 and 0.285 for the unprocessed spectra and between 0.135 and 0.262 for the preprocessed spectra. The estimated variance components for the latent traits were back transformed to the spectral variables. Heritabilities of these spectral variables ranged from 0.018 to 0.408 and variance ratios of the permanent environmental effects of goats were between 0.002 and 0.184 of the phenotypic spectral variation. High-to-moderate heritabilities were observed in particular in spectral regions related to major milk components (fat, lactose, and protein): between 1,030 and 1,300 cm(-1), 1,500 and 1,600 cm(-1), 1,700 and 1,800 cm(-1), and 2,800 and 3,000 cm(-1). Our results confirmed that a substantial amount of genetic variation exists in goat milk FTIR spectra. Not all spectral variations are of genetic origin; some FTIR regions are highly influenced by herd test-day variation. The study also pointed out the possibility of using FTIR spectra as a monitoring tool in herd management.
傅里叶变换红外（FTIR）光谱常用于预测奶牛的主要牛奶成分，是奶牛遗传评估中的一种方法。到目前为止，羊奶 FTIR 光谱的遗传变异只能通过其对主要牛奶成分的贡献间接得知。本研究直接检测了羊奶 FTIR 光谱的遗传和环境成分。研究使用了一个包含 83858 个牛奶 FTIR 光谱观测值的数据集，这些观测值来自 271 个挪威奶山羊群的 29320 头奶山羊。主成分分析应用于未处理和预处理的光谱数据，由于无法对所有光谱变量进行多性状分析，因此定义了新的性状（潜在性状）。从主成分分析中保留了 8 个和 7 个潜在变量，分别解释了未处理和预处理光谱总变异的约 99%，用于遗传分析。使用约束最大似然法估计了潜在性状的遗传和环境方差分量。未处理光谱中潜在性状的遗传与总表型方差比（遗传力）在 0.011 到 0.285 之间，预处理光谱中潜在性状的遗传与总表型方差比在 0.135 到 0.262 之间。潜在性状的估计方差分量被反变换回光谱变量。这些光谱变量的遗传力范围在 0.018 到 0.408 之间，山羊永久性环境效应的方差比在 0.002 到 0.184 之间，占表型光谱变异的比例。在与主要牛奶成分（脂肪、乳糖和蛋白质）相关的光谱区域观察到了较高到中等程度的遗传力：1030 到 1300 cm-1、1500 到 1600 cm-1、1700 到 1800 cm-1 以及 2800 到 3000 cm-1。我们的结果证实，羊奶 FTIR 光谱中存在大量的遗传变异。并非所有光谱变化都具有遗传起源；一些 FTIR 区域受羊群测试日变化的影响很大。该研究还指出了将 FTIR 光谱用作牧场管理监测工具的可能性。
