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首页> 外文期刊>Journal of dairy research >Repeatability estimates for milk coagulation traits and non-coagulation of milk in Finnish Ayrshire cows
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Repeatability estimates for milk coagulation traits and non-coagulation of milk in Finnish Ayrshire cows

机译：芬兰埃尔郡奶牛的乳凝特性和非凝乳重复性估算

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摘要

Effects of systematic environmental factors and milk production and quality traits on milk coagulation properties (MCP), and on repeatability of those traits were estimated from 979 milk samples collected once a month over a period of 2 years from 83 Finnish Ayrshire cows. Estimation was based on a multitrait animal model and REML methodology. In addition, persistence of non-coagulation of milk in individual cows, and factors associated with it were established from a sub sample of 24 cows producing non-coagulating (NC) milk at least once. MCP were at their best during the first lactation, at the beginning and at the end of lactation, and during grazing seasons. Variation in MCP with systematic environmental factors was partly due to variation in composition and quality of milk, especially in pH and In (somatic cell count, SCC). Coefficients of repeatability for milk coagulation time and curd firmness were 0.65 and 0.68. These estimates were of the same magnitude as those for protein content, but were higher than those for daily milk yield, fat content, pH, and SCC. Based on the repeatability estimates for the milk coagulation traits and effects of the environmental factors, cows should be sampled at least three times during a lactation to estimate reliably breeding values for the milk coagulation traits. A total of 10% of the milk samples did not coagulate in 30 min after addition of rennet. Cows that produced NC milk at least once (30% of the cows) could be classified into those that produced NC milk only a few times during a lactation and those that produced NC milk at almost every sampling. Based on logistic regression analyses, peak and mid-lactation, high milk yield, low protein and fat content and high pH increased the risk of non-coagulation of milk.
机译：系统性的环境因素以及产奶量和品质性状对牛奶凝结特性（MCP）以及这些性状的可重复性的影响，是根据在两年内每月从83头芬兰Ayrshire奶牛中每月采集一次的979份牛奶样本估算得出的。估计基于多特征动物模型和REML方法论。此外，从至少生产一次非凝结（NC）牛奶的24头母牛的子样本中，确定了个体母牛的非凝结牛奶持续性以及与之相关的因素。在第一次哺乳，哺乳开始和结束以及放牧季节，MCP处于最佳状态。 MCP随系统环境因素的变化部分是由于牛奶的成分和质量（尤其是pH和In）（体细胞计数，SCC）变化所致。牛奶凝结时间和凝乳硬度的重复性系数分别为0.65和0.68。这些估算值与蛋白质含量的估算值相同，但高于每日牛奶产量，脂肪含量，pH和SCC的估算值。根据对牛奶凝结性状的可重复性估算和环境因素的影响，泌乳期间应至少对母牛取样3次，以可靠地估算出牛奶凝结性状的育种值。添加凝乳酶后30分钟内，总共有10％的牛奶样品未凝结。至少生产一次NC牛奶的母牛（占母牛的30％）可分为泌乳期间仅几次生产NC牛奶的母牛和几乎每次采样都生产NC牛奶的母牛。根据逻辑回归分析，高峰和中期泌乳，高产奶量，低蛋白和脂肪含量以及高pH值会增加牛奶不凝结的风险。

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