The milk fatty acid (FA) profile is far from the optimal fat composition in regards to human health. The natural sources of variation, such as feeding or genetics, could be used to increase the concentrations of unsaturated fatty acids. The impact of feeding is well described. However, genetic effects on the milk FA composition begin to be extensively studied. This paper summarizes the available information about the genetic variability of FAs. The greatest breed differences in FA composition are observed between Holstein and Jersey milk. Milk fat of the latter breed contains higher concentrations of saturated FAs, especially short-chain FAs. The variation of the delta-9 desaturase activity estimated from specific FA ratios could explain partly these breed differences. The choice of a specific breed seems to be a possibility to improve the nutritional quality of milk fat. Generally, the proportions of FAs in milk are more heritable than the proportions of these same FAs in fat. Heritability estimates range from 0.00 to 0.54. The presence of some single nucleotide polymorphisms could explain partly the observed individual genetic variability. The polymorphisms detected onSCD1 andDGAT1 genes influence the milk FA composition. TheSCD1 V allele increases the unsaturation of C16 and C18. TheDGAT1 A allele is related to the unsaturation of C18. So, a combination of the molecular and quantitative approaches should be used to develop tools helping farmers in the selection of their animals to improve the nutritional quality of the produced milk fat.

中文翻译：

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乳脂肪酸的遗传变异性。

就人类健康而言，牛奶脂肪酸 (FA) 分布远非最佳脂肪成分。变异的自然来源，例如喂养或遗传，可用于增加不饱和脂肪酸的浓度。喂养的影响得到了很好的描述。然而，开始广泛研究对牛奶 FA 组成的遗传影响。本文总结了有关 FA 遗传变异性的可用信息。在荷斯坦奶和泽西奶之间观察到 FA 成分的最大品种差异。后一个品种的乳脂含有较高浓度的饱和脂肪酸，尤其是短链脂肪酸。根据特定 FA 比率估计的 delta-9 去饱和酶活性的变化可以部分解释这些品种差异。选择特定品种似乎有可能改善乳脂的营养质量。通常，牛奶中 FAs 的比例比这些相同 FAs 在脂肪中的比例更具遗传性。遗传力估计值在 0.00 到 0.54 之间。一些单核苷酸多态性的存在可以部分解释观察到的个体遗传变异性。检测到的多态性SCD1和DGAT1基因影响牛奶 FA 组成。所述SCD1等位基因（V）增加C16和C18的不饱和度。所述DGAT1 A等位基因涉及C18的不饱和度。因此，应结合使用分子和定量方法来开发工具，帮助农民选择动物，以提高所生产乳脂的营养质量。