Piepers S, Opsomer G, Meyer E, Demeyere K, Barkema H W, de Kruif A, De Vliegher S
Department of Reproduction, Obstetrics and Herd Health, Ghent University, Merelbeke, Belgium.
J Dairy Sci. 2009 Sep;92(9):4330-9. doi: 10.3168/jds.2009-2029.
Polymorphonuclear neutrophilic leukocytes (PMNL) play an important role in the first line cell-mediated immune defense of the body in general and of the mammary gland against mastitis pathogens in particular. Reduced viability of PMNL close to parturition may explain the high incidence of infectious diseases and the high prevalence of intramammary infections (IMI) in periparturient dairy heifers. Apoptosis of blood PMNL 1 wk before the expected calving date and of blood and milk PMNL at 1 to 4 d in milk was determined using flow cytometry. Information on heifer and gland characteristics was collected before calving and in early lactation. Data were analyzed using multivariable, multilevel regression analysis. Supplementation of a commercial mineral/vitamin mix before calving was associated with less blood (14.4 +/- 2.9 vs. 22.4 +/- 2.1%) and milk PMNL apoptosis (19.0 +/- 1.1 vs. 26.4 +/- 0.9%) near calving, presumably related to higher blood selenium concentrations. Both blood and milk PMNL apoptosis showed seasonal variation with the highest proportion of apoptotic cells between January and March (32.0 +/- 6.1 and 34.6 +/- 2.7%, respectively) and April and June (31.3 +/- 5.7 and 37.8 +/- 2.3%, respectively). Heifers losing 0.25 points or more of their body condition in the periparturient period had higher proportions of apoptotic blood PMNL in early lactation compared with heifers losing less than 0.25 points (24.0 +/- 2.8 vs. 16.6 +/- 1.7%). Milk PMNL apoptosis was less pronounced in quarters having teat orifices colonized with non-aureus staphylococci before calving (18.9 +/- 1.0 vs. 29.4 +/- 1.0%). The variation in blood PMNL apoptosis before and after calving mainly resided at the heifer level (71.4 and 98.4% of the total variation, respectively), whereas the variation in milk PMNL apoptosis mainly resided at the heifer (45.7% of the total variation) and quarter levels (45.5% of the total variation). These data imply that the impaired blood and milk PMNL viability in periparturient heifers can be reduced by optimization of certain heifer management practices such as supplementation of minerals/vitamins, and pasture and feeding strategies.
多形核嗜中性白细胞（PMNL）在机体的一线细胞介导免疫防御中发挥着重要作用，尤其是在乳腺抵抗乳腺炎病原体方面。临产前PMNL活力降低可能解释了围产期奶牛小母牛传染病高发以及乳房内感染（IMI）患病率高的原因。使用流式细胞术测定了预期产犊日期前1周血液中PMNL以及产犊后1至4天血液和乳汁中PMNL的凋亡情况。在产犊前和泌乳早期收集了有关小母牛和乳腺特征的信息。数据采用多变量、多层次回归分析进行分析。产前补充商业矿物质/维生素混合物与临产前血液（14.4±2.9%对22.4±2.1%）和乳汁中PMNL凋亡减少有关（19.0±1.1%对26.4±0.9%），这可能与血液中硒浓度较高有关。血液和乳汁中PMNL凋亡均呈现季节性变化，1月至3月凋亡细胞比例最高（分别为32.0±6.1%和34.6±2.7%），4月至6月也较高（分别为31.3±5.7%和37.8±2.3%）。与体况损失小于0.25分的小母牛相比，围产期体况损失0.25分或更多的小母牛在泌乳早期血液中凋亡PMNL比例更高（24.0±2.8%对16.6±1.7%）。在产前乳头开口处被非金黄色葡萄球菌定植的乳腺中，乳汁中PMNL凋亡不太明显（18.9±1.0%对29.4±1.0%）。产犊前后血液中PMNL凋亡的变化主要存在于小母牛水平（分别占总变化的71.4%和98.4%），而乳汁中PMNL凋亡的变化主要存在于小母牛水平（占总变化的45.7%）和乳腺水平（占总变化的45.5%）。这些数据表明，通过优化某些小母牛管理措施，如补充矿物质/维生素以及牧场和饲养策略，可以降低围产期小母牛血液和乳汁中PMNL活力受损的情况。
