Paudyal Sushil, Pena Gustavo, Melendez Pedro, Roman-Muniz Ivette Noa, Pinedo Pablo J
Department of Animal Sciences, Colorado State University, Fort Collins, CO.
Advanced Animal Diagnostics, Morrisville, NC.
Transl Anim Sci. 2018 Jun 5;2(3):231-240. doi: 10.1093/tas/txy065. eCollection 2018 Sep.
The use of milk leukocyte differential () test has been proposed as a complement to somatic cell count () to assess the presence and the severity of intramammary infection. However, detailed information regarding the behavior of MLD under different physiological or pathological stages of the cow is nonexistent. The objective was to analyze the association between milk leukocyte proportions provided by a commercial automated MLD test and multiple cow and quarter-level variables. The study population consisted of 104 Holstein cows (32 primiparous and 72 multiparous) in one farm. Cows were categorized by days in milk as early (<50 DIM; =29), middle (50-250 DIM; =25), and late lactation (>250 DIM; = 50). Milk from 416 quarters was collected and analyzed for lymphocytes (), neutrophils (), and macrophages () counts using an automated milk fluorescence microscopy system. Concurrently, a sterile composite milk sample was collected from each cow for pathogen identification through microbiological culture. Culture results were classified as no growth (), gram-negative (), gram-positive (), or other (). Milk leukocyte proportions varied depending on the level of total leukocyte counts (; < 0.001). Similarly, leukocyte ratios (NEU:LYM, NEU:MAC, and phagocyte:LYM) were different for multiple TLC categories ( < 0.05). There was no association between parity number and MLD; however, cows in early lactation had the greatest proportions of NEU and LYM. Leukocyte ratios varied depending on parity number and stage of lactation. Cows in the medium milk-yield category had the smallest proportions of NEU and LYM, and there was significant variation in leukocyte ratios, depending on the level of milk yield. In healthy quarters, MLD were not associated with quarter position; however, the NEU:MAC ratio was greater in rear quarters than in front quarters. In quarters with TLC >100,000, NEU% was greater in rear quarters than in front quarters ( = 0.03). For quarters with pathogen growth, TLC was greatest for GN followed by OTH and GP ( < 0.001). Milk LD depended on the isolated pathogen group, although the magnitudes of the differences were small. Although the changes in the proportions of leukocytes in milk were associated with categories of TLC, levels of milk yield, and mastitis-causing pathogen groups, the deviations were small in magnitude. Additional research is necessary to determine the potential applications for this methodology.
牛奶白细胞分类（MLD）检测已被提议作为体细胞计数（SCC）的补充，用于评估乳房内感染的存在和严重程度。然而，关于奶牛在不同生理或病理阶段MLD表现的详细信息并不存在。目的是分析商业自动化MLD检测提供的牛奶白细胞比例与多个奶牛和乳区水平变量之间的关联。研究群体包括一个农场的104头荷斯坦奶牛（32头初产牛和72头经产牛）。奶牛按泌乳天数分为早期（<50天；n = 29）、中期（50 - 250天；n = 25）和晚期泌乳（>250天；n = 50）。收集了416个乳区的牛奶，使用自动化牛奶荧光显微镜系统分析淋巴细胞（LYM）、中性粒细胞（NEU）和巨噬细胞（MAC）计数。同时，从每头奶牛收集无菌混合牛奶样本，通过微生物培养进行病原体鉴定。培养结果分为无生长（NG）、革兰氏阴性（GN）、革兰氏阳性（GP）或其他（OTH）。牛奶白细胞比例因总白细胞计数（TLC）水平而异（P < 0.001）。同样，多个TLC类别中白细胞比率（NEU:LYM、NEU:MAC和吞噬细胞:LYM）也不同（P < 0.05）。胎次与MLD之间没有关联；然而，早期泌乳的奶牛NEU和LYM比例最高。白细胞比率因胎次和泌乳阶段而异。中等产奶量类别的奶牛NEU和LYM比例最小，并且白细胞比率因产奶量水平存在显著差异。在健康乳区，MLD与乳区位置无关；然而，后乳区的NEU:MAC比率高于前乳区。在TLC >100,000的乳区中，后乳区的NEU%高于前乳区（P = 0.03）。对于有病原菌生长的乳区，TLC在GN组中最高，其次是OTH组和GP组（P < 0.001）。牛奶LD取决于分离出的病原体组，尽管差异幅度较小。虽然牛奶中白细胞比例的变化与TLC类别、产奶量水平和引起乳腺炎的病原体组有关，但偏差幅度较小。需要进一步研究来确定该方法的潜在应用。
