Abstract Milk protein genes are known to be highly polymorphic. Several studies have shown the influence of milk proteins genetic variants and casein haplotypes on milk nutritional and technological properties. From 1990, the analysis of caseins polymorphism gained new attention due to the concern about possible negative effects of CSN2*A1 on human health. As a consequence, the CSN2*A2 variant gained interest and milk produced by with A2A2 β-casein cows is now available in different countries. Aim of the present paper was to analyse how casein variants’ and haplotypes’ frequencies changed in the Italian Holstein breed, due to the health ‘claims’ about CSN2*A2, and the possible effects on milk technological properties. Data were compared also with Italian Jersey cattle. A total of 223,655 Holstein and of 622 Jersey were genotyped using Illumina beadchips and data of 62 SNP in the casein cluster were analysed to reconstruct casein genotypes and haplotypes. The results demonstrate that although the selection towards β-casein A2 is not so effective in Italy, an increase of the frequency of this allele to the disadvantage of A1 and B alleles, included in the most favourable genotypes and haplotypes for cheese making, is occurring and should not be forced. Indeed, although a selection for the favourable κ-casein B allele, and against the unfavourable E allele, is occurring and is limiting the general loss of haplotypes associated with good technological properties, the sharp decrease of the favourable B-B and I-B β- κ-haplotypes, is an alert of the risk of losing useful biodiversity. Highlights After the concern about the β-caseinA1 variant on human health, a selection favoring the A2 allele was carried out in different countries. In Italy milk is mostly destined to cheese-making and even without a direct selection for theβ-casein A2 caseins allelic frequencies are changing. Genotyping data should be used to monitor and maybe contrast the reduction of variants associated with milk favorable technological properties.

中文翻译：

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选择对意大利荷斯坦牛酪蛋白遗传多态性和单倍型的影响

摘要 众所周知，牛奶蛋白基因具有高度多态性。几项研究表明，牛奶蛋白质遗传变异和酪蛋白单倍型对牛奶营养和技术特性的影响。从 1990 年开始，由于担心 CSN2*A1 对人类健康可能产生的负面影响，酪蛋白多态性的分析获得了新的关注。因此，CSN2*A2 变体引起了人们的兴趣，现在不同国家都可以使用 A2A2 β-酪蛋白奶牛生产的牛奶。本论文的目的是分析由于 CSN2*A2 的健康“声明”以及对牛奶技术特性的可能影响，意大利荷斯坦品种中酪蛋白变体和单倍型的频率如何变化。数据还与意大利泽西牛进行了比较。共有 223 个，655 Holstein 和 622 Jersey 使用 Illumina beadchips 进行基因分型，分析酪蛋白簇中 62 个 SNP 的数据以重建酪蛋白基因型和单倍型。结果表明，虽然对 β-酪蛋白 A2 的选择在意大利不是那么有效，但这种等位基因的频率正在增加，而不是 A1 和 B 等位基因，包括在最有利的基因型和单倍型的奶酪制作中，正在发生并且不应该被强迫。事实上，虽然对有利的 κ-酪蛋白 B 等位基因和不利的 E 等位基因的选择正在发生，并且限制了与良好技术特性相关的单倍型的普遍丧失，但有利的 BB 和 IB β-κ-单倍型，是对失去有用生物多样性风险的警告。亮点 在关注 β-caseinA1 变体对人类健康的影响之后，在不同国家进行了有利于 A2 等位基因的选择。在意大利，牛奶主要用于制作奶酪，即使没有直接选择β-酪蛋白 A2 酪蛋白等位基因频率也在发生变化。应该使用基因分型数据来监测和对比与牛奶有利技术特性相关的变异的减少。