Bertocchi L, Vitali A, Lacetera N, Nardone A, Varisco G, Bernabucci U
1 Istituto Zooprofilattico Sperimentale, Lombardia ed Emilia Romagna, Brescia, Italy.
2 Dipartimento di Scienze e Tecnologie per l'Agricoltura, le Foreste, la Natura e l'Energia (DAFNE), Università degli Studi della Tuscia, Viterbo, Italy.
Animal. 2014 Apr;8(4):667-74. doi: 10.1017/S1751731114000032. Epub 2014 Feb 11.
A retrospective study on seasonal variations in the characteristics of cow's milk and temperature-humidity index (THI) relationship was conducted on bulk milk data collected from 2003 to 2009. The THI relationship study was carried out on 508 613 bulk milk data items recorded in 3328 dairy farms form the Lombardy region, Italy. Temperature and relative humidity data from 40 weather stations were used to calculate THI. Milk characteristics data referred to somatic cell count (SCC), total bacterial count (TBC), fat percentage (FA%) and protein percentage (PR%). Annual, seasonal and monthly variations in milk composition were evaluated on 656 064 data items recorded in 3727 dairy farms. The model highlighted a significant association between the year, season and month, and the parameters analysed (SCC, TBC, FA%, PR%). The summer season emerged as the most critical season. Of the summer months, July presented the most critical conditions for TBC, FA% and PR%, (52 054 ± 183 655, 3.73% ± 0.35% and 3.30% ± 0.15%, respectively), and August presented higher values of SCC (369 503 ± 228 377). Each milk record was linked to THI data calculated at the nearest weather station. The analysis demonstrated a positive correlation between THI and SCC and TBC, and indicated a significant change in the slope at 57.3 and 72.8 maximum THI, respectively. The model demonstrated a negative correlation between THI and FA% and PR% and provided breakpoints in the pattern at 50.2 and 65.2 maximum THI, respectively. The results of this study indicate the presence of critical climatic thresholds for bulk tank milk composition in dairy cows. Such indications could facilitate the adoption of heat management strategies, which may ensure the health and production of dairy cows and limit related economic losses.
对2003年至2009年收集的散装牛奶数据进行了一项关于牛奶特性季节性变化及温度-湿度指数（THI）关系的回顾性研究。THI关系研究是基于意大利伦巴第地区3328个奶牛场记录的508613条散装牛奶数据项展开的。利用40个气象站的温度和相对湿度数据来计算THI。牛奶特性数据涉及体细胞计数（SCC）、总细菌计数（TBC）、脂肪百分比（FA%）和蛋白质百分比（PR%）。对3727个奶牛场记录的656064条数据项评估了牛奶成分的年度、季节和月度变化。该模型突出显示了年份、季节和月份与所分析参数（SCC、TBC、FA%、PR%）之间存在显著关联。夏季成为最关键的季节。在夏季月份中，7月对于TBC、FA%和PR%呈现出最关键的条件（分别为52054±183655、3.73%±0.35%和3.30%±0.15%），8月的SCC值更高（369503±228377）。每条牛奶记录都与最近气象站计算出的THI数据相关联。分析表明THI与SCC和TBC之间呈正相关，并且分别在最大THI为57.3和72.8时斜率出现显著变化。该模型表明THI与FA%和PR%之间呈负相关，并且分别在最大THI为50.2和65.2时模式出现断点。本研究结果表明奶牛散装罐牛奶成分存在关键气候阈值。这些迹象有助于采用热管理策略，这可能确保奶牛的健康和生产并限制相关经济损失。
