Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691.
Department of Animal Sciences, The Ohio State University, Columbus 43210.
J Dairy Sci. 2022 Sep;105(9):7615-7622. doi: 10.3168/jds.2022-21794. Epub 2022 Jul 22.
Intramammary infections (IMI) in primigravid dairy heifers can affect mammary growth and development, which can reduce first-lactation milk yield. Detection of IMI in heifers most often involves the use of culture-based methods that are not often used in production dairy settings given their labor- and time-consuming nature. The objective of this study was to determine whether mammary secretion somatic cell count (SCC) and viscosity were associated with the infection status of primigravid heifer mammary glands. A total of 270 heifers from a single farm were used, selected based on the farmer's willingness to participate. The study was conducted from June to October 2020. Mammary secretion samples were aseptically collected from a randomly selected quarter of each heifer at 75 d prepartum (75PP), and another quarter of each heifer was sampled at 35 d prepartum (35PP). The remaining 2 quarters of each heifer were not examined. Mammary secretion samples underwent bacteriological examination to determine IMI status and quantitative SCC measurement and were also assessed for secretion viscosity based on visual observation. Prevalence of IMI was 26% (69/270) and 28% (71/255) at 75 and 35 d prepartum, respectively. Uninfected secretion samples had 133.2 [95% confidence interval (CI): 16.8 to >999.9] times greater odds to be thick compared with samples infected with a major pathogen, and 14.4 (95% CI: 8.5 to 24.1) times greater odds to be thick compared with samples infected with non-aureus staphylococci (NAS). The mean secretion SCC of uninfected quarters (6.04 ± 0.03 log cells/mL) was significantly lower than that of secretions collected from quarters infected with Staphylococcus chromogenes (6.34 ± 0.04 log cells/mL), other NAS species (6.28 ± 0.10 log cells/mL), or a major pathogen (6.73 ± 0.08 log cells/mL). These results indicate that mammary secretion viscosity and SCC measurement may be useful tools in identifying primigravid heifer quarters with IMI. The ability to evaluate viscosity at time of sampling may be a useful strategy that could be incorporated into interventions designed to diminish the negative effects of prepartum IMI on lactational performance.
初产奶牛的乳腺炎（IMI）会影响乳腺的生长和发育，从而降低初乳产量。在牧场环境中，通常使用基于培养的方法来检测 IMI，但这些方法由于耗时耗力而不常用。本研究的目的是确定初产奶牛乳腺的乳汁体细胞计数（SCC）和黏度是否与感染状态有关。总共使用了来自一个农场的 270 头奶牛，这些奶牛是根据农场主的意愿选择的。该研究于 2020 年 6 月至 10 月进行。在产前 75 天（75PP）时，从每头奶牛随机选择的一个乳区无菌采集乳汁样本，在产前 35 天（35PP）时从每头奶牛的另一个乳区采集乳汁样本。每头奶牛的其余两个乳区不进行检查。对乳汁样本进行细菌学检查以确定 IMI 状态和定量 SCC 测量，并根据视觉观察评估分泌黏度。75PP 和 35PP 时 IMI 的患病率分别为 26%（69/270）和 28%（71/255）。未感染的乳汁样本比主要病原体感染的样本更有可能呈现浓稠状态，优势比为 133.2[95%置信区间（CI）：16.8 至>999.9]；比非金黄色葡萄球菌（NAS）感染的样本更有可能呈现浓稠状态，优势比为 14.4（95%CI：8.5 至 24.1）。未感染乳区的乳汁 SCC 平均值（6.04 ± 0.03 log 细胞/mL）明显低于感染金黄色酿脓葡萄球菌（6.34 ± 0.04 log 细胞/mL）、其他 NAS 物种（6.28 ± 0.10 log 细胞/mL）或主要病原体（6.73 ± 0.08 log 细胞/mL）的乳汁 SCC。这些结果表明，乳汁黏度和 SCC 测量可能是识别初产奶牛 IMI 乳区的有用工具。在采样时评估黏度的能力可能是一种有用的策略，可以纳入旨在减轻产前 IMI 对泌乳性能负面影响的干预措施中。
