Department of Animal Sciences, School of Veterinary Medicine and Animal Sciences, University of São Paulo (USP), Pirassununga, SP, Brazil.
Business Economics Group, Wageningen University, Hollandseweg 1, 6706 KN, Wageningen, The Netherlands.
Vet J. 2020 Aug;262:105473. doi: 10.1016/j.tvjl.2020.105473. Epub 2020 May 22.
This study aimed to evaluate the effects of chronic subclinical mastitis (CSM) on milk production and component yields in dairy cows. A total of six herds located in the Midwest area of São Paulo State, Brazil were selected. Herds were visited once every 2 weeks to measure milk yield and to collect milk samples from lactating Holstein cows. Milk samples were collected at two stages (1 and 2), and each stage comprised three milk samplings. In stage 1, a total of 117 of 647 cows were diagnosed with CSM based on at least two of three repeated somatic cell counts (SCC) > 2000,000 cells/mL and positive bacterial milk culture results (BC). Cows with CSM were selected for the second stage. In stage 2, selected cows had quarter sampling aseptically collected for BC analyses prior to milking, and quarter milk yield was measured. Milk components (total protein, fat, lactose, and total solids) were measured using mid-infrared spectroscopy. Mammary quarters were considered healthy if all three repeated SCC results were ≤ 200,000 cells/mL and no bacterial growth was detected on BC. All quarters with positive bacterial growth were classified as having (non-chronic) subclinical mastitis when only one of three SCC results were > 200,000 cells/mL, and CSM when at least two of three SCC results were > 200,000 cells/mL. The effects of CSM by type of pathogen on milk and components yield were assessed using a linear mixed model. Mammary quarters with CSM caused by major pathogens had milk loss of 1.1 kg/quarter milking in comparison to healthy quarters. Milk losses were 0.8 and 1.3 kg/quarter milking when CSM was caused by Staphylococcus aureus or environmental streptococci, respectively. In addition, healthy quarters produced more milk components than quarters with CSM caused by major pathogens. Minor pathogens causing CSM (non-aureus staphylococci and Corynebacterium spp.) had no effect on milk yield. Quarters with CSM had lower milk and component yields when compared with healthy quarters. Milk losses varied according to the type of pathogen and were higher when associated with major pathogens such as S. aureus and environmental streptococci compared with healthy quarters.
本研究旨在评估慢性亚临床乳腺炎（CSM）对奶牛产奶量和成分产量的影响。选择了位于巴西圣保罗州中西部地区的六个牛群。每两周访问一次牛群，以测量产奶量并从泌乳荷斯坦奶牛中收集牛奶样本。牛奶样本在两个阶段（1 和 2）收集，每个阶段包括三次牛奶采样。在第 1 阶段，根据至少两次重复的体细胞计数（SCC）>2000000 个细胞/ml 和阳性细菌奶培养结果（BC），共有 647 头奶牛中的 117 头被诊断为 CSM。选择患有 CSM 的奶牛进入第 2 阶段。在第 2 阶段，在挤奶前对选定的奶牛进行无菌性四分体采样进行 BC 分析，并测量四分体产奶量。使用中红外光谱法测量牛奶成分（总蛋白、脂肪、乳糖和总固体）。如果所有三次重复 SCC 结果均≤200000 个细胞/ml，并且在 BC 上未检测到细菌生长，则认为乳腺四分体健康。当只有一次 SCC 结果>200000 个细胞/ml 时，所有具有阳性细菌生长的四分体被归类为（非慢性）亚临床乳腺炎，当至少两次 SCC 结果>200000 个细胞/ml 时被归类为 CSM。使用线性混合模型评估 CSM 按病原体类型对产奶量和成分产量的影响。与健康四分体相比，由主要病原体引起的 CSM 乳腺四分体的产奶量损失为 1.1kg/四分体挤奶。当 CSM 由金黄色葡萄球菌或环境链球菌引起时，产奶量损失分别为 0.8 和 1.3kg/四分体挤奶。此外，健康四分体比由主要病原体引起的 CSM 四分体产生更多的牛奶成分。引起 CSM 的次要病原体（非金黄色葡萄球菌和棒状杆菌属）对产奶量没有影响。与健康四分体相比，患有 CSM 的四分体的产奶量和成分产量较低。与健康四分体相比，CSM 四分体的牛奶和成分产量较低。根据病原体的类型，产奶量损失不同，与金黄色葡萄球菌和环境链球菌等主要病原体相关时，产奶量损失高于健康四分体。
