Management factors and cow traits influencing milk somatic cell counts and teat hyperkeratosis during different seasons

The objective of the study was to analyze the effect of season, parity, stage of lactation and milking procedures on teat-end condition, cow cleanliness and milk somatic cell count (SCC) and identify risk factors associated with milk somatic cell counts greater than 100,000 cells/mL. A group of 15 Italian dairy farms were visited three times during different seasons: the cold (3.8 °C), the hot (23.5 °C) and the mild (12.1 °C) seasons. Hygiene of udder, flanks and legs was scored on 2,330 cows based on a 4-point scale system, from very clean (score 1) to very dirty skin (score 4). On the same cows, a total of 9,201 teats were assessed for teat-end condition and assigned to four different classes of hyperkeratosis: No lesion (N), Smooth ring (S), Rough (R) and Very rough skin (VR). The average percentage of teats classified in the worst classes of hyperkeratosis (R and VR) equaled 15.9%. Teat hyperkeratosis, cow cleanliness and milk somatic cell count were significantly affected by the season. Teat condition was significantly better in primiparous than in multiparous cows and deteriorated during lactation. Cows with the lowest values of SCC, better teat conditions and better hygiene scores were found in the farms where more than one milking practice (among forestripping, pre-dipping and post-dipping) were performed. Multivariate logistic analysis confirmed that parity and days of lactation significantly influence the risk of high somatic cell count. Among environmental and management aspects, clean udders and pre-dipping are associated with a reduced likelihood to have individual cows with milk SCC greater than 100,000 cells/mL. Teat hyperkeratosis does not seem to be a risk factor of high SCC. Milk somatic cell count can be lowered by means of simple actions such as improvement of hygiene condition of cow environment and adoption of pre-dipping.

本研究旨在分析季节、胎次、泌乳阶段及挤奶流程对乳头末端状态、奶牛清洁度及牛奶体细胞计数（Somatic Cell Count）的影响，并识别牛奶体细胞计数超过100,000个/mL的相关风险因素。研究团队于不同季节——低温季（3.8℃）、高温季（23.5℃）与温和季（12.1℃）——对15座意大利奶牛场开展了三次走访调研。研究人员基于4分制评分体系（从极清洁的1分至皮肤极脏的4分），对2330头奶牛的乳房、侧腹及腿部的卫生状况进行评分。针对同批次奶牛，共计对9201个乳头的末端状态进行评估，并将其划分为四种角化过度等级：无病变（N）、平滑环（S）、粗糙（R）及极粗糙（VR）。被归类为角化过度最严重等级（R与VR）的乳头平均占比为15.9%。季节因素对乳头角化过度、奶牛清洁度及SCC均存在显著影响。初产奶牛的乳头状态显著优于经产奶牛，且随泌乳进程逐渐恶化。在同时采用至少两项挤奶操作（包括挤奶前弃奶擦拭、挤奶前药浴及挤奶后药浴）的奶牛场中，其奶牛的体细胞计数更低、乳头状态更佳且卫生评分更高。多变量逻辑回归分析证实，胎次与泌乳天数对高SCC风险存在显著影响。在环境与管理维度中，清洁的乳房及挤奶前药浴可降低个体奶牛SCC超过100,000个/mL的概率。乳头角化过度似乎并非高SCC的风险因素。通过改善奶牛养殖环境的卫生状况、采用挤奶前药浴等简单措施，即可有效降低牛奶体细胞计数。