Departamento de Producción Animal, Universidad de Córdoba, Córdoba 14071, Spain.
Departamento de Producción Animal, Universidad de Córdoba, Córdoba 14071, Spain.
J Dairy Sci. 2018 Dec;101(12):10733-10742. doi: 10.3168/jds.2018-14752. Epub 2018 Oct 11.
In Spain, ewe milk is mainly used for cheesemaking, and farming systems have traditionally been based on the use of autochthonous breeds. However, in recent years, the progressive introduction of highly productive foreign breeds in Spanish farms has led to an increasing interest in the characterization of dairy sheep breeds to evaluate whether genetic selection schemes should focus on productivity or milk technological aptitude. The purpose of this work was to explore milk composition and coagulation to classify 4 of the main dairy sheep breeds used in Spain. This study included 832 individual ewe milk samples from the breeds Manchega, Assaf, Merino de Grazalema, and Merino de Los Pedroches. Samples were analyzed for native pH, composition (fat, protein, lactose, and total solids), coagulation properties, and individual laboratory curd yield. An indicator of coagulation efficiency was also determined. Canonical discriminant analysis was performed to establish differences and similarities among breeds based on the measured variables. In addition, cluster analysis was performed to study and quantify the concrete relationships among the discriminated groups. Discriminant analysis proved to be a powerful tool to accurately draw distinctions between breeds. In all cases, discrimination among breeds was evident and the 4 breeds could be easily differentiated. Cluster analysis showed greater similarity between Merino de Grazalema and Assaf compared with the other breeds, and F-statistics indicated a higher discriminating ability for the variables related to milk composition. However, Merino de Grazalema and Manchega were difficult to separate according to milk composition, but the coagulation process differenced them clearly. Coagulation also evidenced similarities between Manchega and Merino de Los Pedroches, although the latter was revealed to be the most different breed of all 4, which could lay the ground for its differentiation as an independent breed in the Official Catalogue of Spanish Livestock Breeds.
在西班牙，绵羊奶主要用于奶酪制作，养殖系统传统上基于使用本土品种。然而，近年来，西班牙农场中高度生产力的外国品种的逐步引入，导致人们越来越关注奶绵羊品种的特征，以评估遗传选择方案是否应侧重于生产力或牛奶技术适应性。本研究的目的是探索牛奶成分和凝固特性，以对西班牙使用的 4 种主要奶绵羊品种进行分类。本研究包括来自 Manchega、Assaf、Merino de Grazalema 和 Merino de Los Pedroches 品种的 832 个绵羊奶样。对样本进行了天然 pH 值、成分（脂肪、蛋白质、乳糖和总固体）、凝固特性和个体实验室凝乳产量分析。还确定了凝固效率的指标。采用典范判别分析根据测量变量建立品种间的差异和相似性。此外，还进行了聚类分析，以研究和量化判别组之间的具体关系。判别分析被证明是一种准确区分品种的有力工具。在所有情况下，品种之间的区分都很明显，4 个品种可以轻松区分。聚类分析表明，Merino de Grazalema 和 Assaf 之间的相似性大于其他品种，并且 F 统计数据表明与牛奶成分相关的变量具有更高的判别能力。然而，根据牛奶成分，Merino de Grazalema 和 Manchega 难以区分，但凝固过程清楚地区分了它们。凝固还表明 Manchega 和 Merino de Los Pedroches 之间存在相似性，尽管后者被证明是 4 个品种中最不同的品种，这可能为其在西班牙官方牲畜品种目录中作为一个独立品种进行区分奠定基础。
