Abstract：
Locally produced food is becoming popular among Swedish consumers. One product that has increased in popularity is artisan-manufactured goat cheese, and although the dairy goat industry in Sweden is small-scale, production is gradually increasing. In goats, the CSN1S1 gene regulates expression of the protein αS1-casein (αS1-CN), which has been found to be important for cheese yield. Over the years, breeding animals have been imported to Sweden from Norway. Historically, a high frequency of the Norwegian goat population carried a polymorphism at the CSN1S1 gene. This polymorphism, called the Norwegian null allele (D), leads to zero or significantly reduced expression of αS1-CN. Using milk samples from 75 goats, this study investigated associations between expression of αS1-CN and genotype at the CSN1S1 gene on milk quality traits from Swedish Landrace goats. Milk samples were grouped according to relative level of αS1-CN (low: 0-6.9% of total protein; medium-high: 7-25% of total protein) and genotype (DD, DG, DA/AG/AA). While the D allele leads to extremely low expression of αS1-CN, the G allele is low expressing and the A allele is highly expressing for this protein. Principal component analysis was used to explore the total variation in milk quality traits. To evaluate the effect of different allele groups on milk quality attributes, 1-way ANOVA and Tukey pairwise comparison tests were used. The majority (72%) of all goat milk samples investigated showed relative αS1-CN content of 0% to 6.82% of total protein. The frequency of individuals homozygous for the Norwegian null allele (DD) was 59% in the population of sampled goats, and only 15% carried at least one A allele. A low relative concentration of αS1-CN was associated with lower total protein, higher pH, and higher relative concentration of β-casein and levels of free fatty acids. Milk from goats homozygous for the null allele (DD) showed a similar pattern as milk with low relative concentration of αS1-CN, but total protein was only numerically lower, and somatic cell count and αS2-CN were higher than for the other genotypes. The associations between levels of αS1-CN and the investigated genotype at the CSN1S1 gene indicate a need for a national breeding program for Swedish dairy goats.
摘要：
当地生产的食品在瑞典消费者中越来越受欢迎。一种越来越受欢迎的产品是手工制造的山羊奶酪，尽管瑞典的奶山羊产业规模很小，产量逐渐增加。在山羊中，CSN1S1基因调节蛋白质αS1-酪蛋白（αS1-CN）的表达，已发现这对奶酪产量很重要。多年来,繁殖动物已从挪威进口到瑞典。历史上,挪威山羊种群的高频率携带CSN1S1基因的多态性。这种多态性，称为挪威零等位基因(D)，导致αS1-CN的表达为零或显著降低。使用75只山羊的牛奶样本，这项研究调查了αS1-CN的表达与CSN1S1基因基因型对瑞典长白羊奶质性状的相关性。根据αS1-CN的相对水平（低：总蛋白的0-6.9％；中-高：总蛋白的7-25％）和基因型（DD，DG,DA/AG/AA）。虽然D等位基因导致αS1-CN的极低表达，对于该蛋白,G等位基因是低表达的,而A等位基因是高表达的。采用主成分分析探讨了牛奶品质性状的总变异。为了评估不同等位基因组对牛奶质量属性的影响，使用单向ANOVA和Tukey成对比较测试。所研究的所有山羊奶样品中的大多数(72%)显示相对αS1-CN含量为总蛋白的0%至6.82%。在采样山羊种群中，挪威无效等位基因（DD）纯合的个体频率为59％，只有15%携带至少一个A等位基因。较低的相对浓度的αS1-CN与较低的总蛋白有关，更高的pH，β-酪蛋白的相对浓度和游离脂肪酸的含量较高。纯合的山羊的无效等位基因（DD）的牛奶显示出与αS1-CN相对浓度低的牛奶相似的模式，但是总蛋白质只是在数字上更低，体细胞计数和αS2-CN高于其他基因型。αS1-CN的水平与CSN1S1基因的研究基因型之间的关联表明需要针对瑞典奶山羊的国家育种计划。
