Effect of milking hygiene, herd size, water hardness and temperature-humidity index on milk quality of dairy farms

ABSTRACT The objective of this study was to evaluate the effect of milking hygiene practices, herd size, water hardness, and temperature-humidity index (THI) on the physicochemical and microbiological characteristics of raw milk, and standard plate count (SPC) in milking machines of dairy farms in the central region of Mexico. Data were collected from fifty-three dairy farms during one year. The evaluated effects included milking hygiene conditions (good, medium, poor), herd size (1-50, 51-100, 101-150, ≥151 heads), water hardness (soft or moderately hard), and THI (comfortable or stressful). The increase in milking hygiene produced greater milk yield (MY) and energy corrected milk (ECM) but lower protein content, and decreased the individual bacterial count (IBC) and somatic cell count (SCC). The MY, ECM, protein content, IBC, and SCC were higher on bigger farms. The use of soft water reduced MY, IBC, and SCC, but improved fat, lactose, total solids (TS), and non-fat solids (NFS). Heat stress negatively affected fat, protein, TS, NFS, acidity, freezing point (FP), SCC, and methylene blue dye reduction test. Poor milking hygiene contributes to higher SPC in milking machine parts. Water hardness and THI did not affect SPC in all milking machine parts. Proper milking hygiene practices, larger herd size, softer water, lower THI, and adequate cleaning and disinfection of the milking machine parts benefits the physicochemical and microbiological quality of the milk.

摘要 本研究旨在评估墨西哥中部地区奶牛场的挤奶卫生操作、畜群规模、水硬度以及温湿度指数（THI）对原料乳理化与微生物特性，以及挤奶设备部件标准平板计数（SPC）的影响。研究数据采集自53家奶牛场，采集周期为一年。本次评估的影响因素包括挤奶卫生状况（优秀、中等、较差）、畜群规模（1~50头、51~100头、101~150头、≥151头）、水硬度（软水或中度硬水）以及THI（舒适状态或应激状态）。挤奶卫生状况提升可提高产奶量（MY）与能量校正乳（ECM）产量，但会降低乳蛋白含量，同时减少个体细菌计数（IBC）与体细胞计数（SCC）。畜群规模越大，产奶量、能量校正乳产量、乳蛋白含量、个体细菌计数与体细胞计数均越高。使用软水可降低产奶量、个体细菌计数与体细胞计数，但可提升乳脂肪、乳糖、总乳固体（TS）与非脂乳固体（NFS）含量。热应激会对乳脂肪、乳蛋白、总乳固体、非脂乳固体、乳酸度、冰点（FP）、体细胞计数以及亚甲蓝还原试验结果产生负面影响。挤奶卫生状况较差会导致挤奶设备部件的标准平板计数数值升高。水硬度与温湿度指数并未对所有挤奶设备部件的标准平板计数产生影响。规范的挤奶卫生操作、更大的畜群规模、更软的水质、更低的温湿度指数，以及对挤奶设备部件进行充分的清洁与消毒，均有助于提升原料乳的理化与微生物品质。