Fonseca Mariana, Kurban Daryna, Roy Jean-Philippe, Santschi Débora E, Molgat Elouise, Dufour Simon
Department of Pathology and Microbiology, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, QC, Canada J2S2M2; Regroupement FRQNT Op+lait, Saint-Hyacinthe, QC, Canada J2S2M2.
Regroupement FRQNT Op+lait, Saint-Hyacinthe, QC, Canada J2S2M2; Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, QC, Canada J2S2M2.
J Dairy Sci. 2025 Apr;108(4):3900-3916. doi: 10.3168/jds.2024-25402. Epub 2025 Jan 6.
Mastitis is the most common disease affecting dairy cattle and is associated with substantial milk loss. Somatic cell count has been widely used as an indicator of udder inflammation (e.g., subclinical mastitis). More recently, differential somatic cell count (DSCC) has become available as an auxiliary tool for milk quality control, with the potential to indicate different stages of inflammation when combined with SCC. This paper aimed to investigate the association of SCS and DSCC with milk yield and milk components at the quarter level. A convenience sample of 5 dairy herds using an automated milking system (AMS) was selected and visited every other week for milk sample collection. Fat, protein, and lactose content were analyzed at Lactanet (Canadian Network for Dairy Excellence, Sainte-Anne-de-Bellevue, Quebec, Canada) by mid-infrared spectroscopy using a MilkoScan FT6000. Determination of SCC and DSCC was also performed by Lactanet using a CombiFoss 7 DC instrument. Milk yield data were retrieved from the AMS. Given the hierarchical structure of the data, a linear mixed model was built with either milk yield or milk components as the outcomes. The results showed that elevated SCS, in combination with lower proportions of DSCC, was associated with the highest milk loss for primiparous and multiparous cows. For instance, the estimated milk loss for a quarter with a SCS of 7 and a DSCC of 55% was 1.45 kg/d compared with a quarter with a SCS of 2 and DSCC of 65% in multiparous cows. The association was similar when the outcome was the lactose content. Quarters with elevated SCS and lower DSCC had the lowest lactose percentage. No notable changes in fat content were observed across different SCS levels in multiparous cows, and quarters with higher DSCC had the lowest fat percentage in primiparous and multiparous cows. Protein content tended to be lower in quarters with increased SCS and low DSCC. In quarters from primiparous cows with DSCC levels above 70%, protein content showed slight variation across SCS levels. For multiparous cows, however, protein content remained relatively stable across different SCS and DSCC levels. In conclusion, our findings revealed that the combination of elevated SCS and low DSCC was associated with the most substantial milk loss. These results could be used to optimize udder health management.
乳腺炎是影响奶牛的最常见疾病，且与大量的产奶量损失有关。体细胞计数已被广泛用作乳房炎症（如亚临床乳腺炎）的指标。最近，差异体细胞计数（DSCC）已成为牛奶质量控制的辅助工具，与体细胞计数（SCC）结合使用时有可能指示炎症的不同阶段。本文旨在研究季度水平上体细胞评分（SCS）和DSCC与产奶量及牛奶成分之间的关联。选取了5个使用自动挤奶系统（AMS）的奶牛群作为便利样本，每隔一周进行一次访问以采集牛奶样本。脂肪、蛋白质和乳糖含量在加拿大魁北克省圣安妮-德-贝尔维尤的Lactanet（加拿大卓越乳业网络）通过使用MilkoScan FT6000的中红外光谱法进行分析。SCC和DSCC的测定也由Lactanet使用CombiFoss 7 DC仪器进行。产奶量数据从AMS中获取。鉴于数据的层次结构，构建了以产奶量或牛奶成分作为结果的线性混合模型。结果表明，SCS升高，再加上DSCC比例较低，与初产和经产奶牛的最高产奶量损失相关。例如，在经产奶牛中，SCS为7且DSCC为55%的一个季度的估计产奶量损失为1.45千克/天，而SCS为2且DSCC为65%的一个季度则为1.45千克/天。当结果是乳糖含量时，这种关联是相似的。SCS升高且DSCC较低的季度乳糖百分比最低。在经产奶牛中，不同SCS水平下未观察到脂肪含量有明显变化，在初产和经产奶牛中，DSCC较高的季度脂肪百分比最低。SCS升高且DSCC较低的季度蛋白质含量往往较低。在DSCC水平高于70%的初产奶牛的季度中，蛋白质含量在不同SCS水平之间显示出轻微变化。然而，对于经产奶牛，蛋白质含量在不同的SCS和DSCC水平之间保持相对稳定。总之，我们的研究结果表明，SCS升高和DSCC较低的组合与最严重的产奶量损失相关。这些结果可用于优化乳房健康管理。
