Multivariate analysis relating milk production, milk composition, and seasons of the year

Abstract Our objective was to quantify the relationship between seasons of the year, milk production, and milk composition of a dairy farm based on data for 48 consecutive months, using multivariate statistical analyses. The dataset contained information on productive indexes and milk composition from the bulk tank milk, which was measured from milk samples, collected monthly and used to determine the total dry extract and defatted dry extract, lactose, fat, protein, somatic cell count, and total bacterial count. Seasons of the year and milk production/hectare were also considered. Factor, cluster, and discriminant analysis were used to study the relationships between the above-mentioned variables. A positive relationship was noted between season and total dry extract, defatted dry extract, milk fat, and protein, with higher values being observed in winter and spring. Similarly, a positive relationship was noted between season and milk production/hectare, lactose content, with an increase in milk production and lactose content in winter and spring, which was negatively related to the somatic cell count and total bacterial count. Milk production and composition varied mainly with seasons. Multivariate analyses facilitated a better understanding of the relationship between milk production and composition on this dairy farm.

摘要 本研究旨在基于连续48个月的监测数据，结合多元统计分析方法，量化某奶牛场的年度季节、牛奶产量与乳成分三者间的关联。本数据集涵盖了从每月采集的乳样中测得的散装罐奶（bulk tank milk）生产指标与乳成分相关信息，测定指标包括总干物质、脱脂干物质、乳糖、乳脂肪、乳蛋白、体细胞数以及总细菌数。此外还纳入了年度季节与单位公顷牛奶产量两项变量。本研究采用因子分析、聚类分析与判别分析，对上述变量间的关联展开探究。研究发现季节与总干物质、脱脂干物质、乳脂肪及乳蛋白含量呈正相关，上述指标在冬、春两季数值更高。同理，季节与单位公顷牛奶产量、乳糖含量亦呈正相关，冬、春两季的牛奶产量与乳糖含量均有所提升；而体细胞数与总细菌数则与上述指标呈负相关。牛奶产量与乳成分主要随季节变化而波动。多元统计分析有助于更深入地理解该奶牛场牛奶产量与乳成分间的关联机制。