Department of Agronomy, Food, Natural resources, Animals and Environment, University of Padova, Legnaro, 35020, Italy.
Department of Veterinary Medical Sciences, Alma Mater Studiorum University of Bologna, Ozzano dell'Emilia, 40064, Italy.
BMC Vet Res. 2024 Jun 7;20(1):249. doi: 10.1186/s12917-024-04083-y.
Intramammary infection is the result of invasion and multiplication of microorganisms in the mammary gland and commonly leads to mastitis in dairy animals. Although much has been done to improve cows' udder health, mastitis remains a significant and costly health issue for dairy farmers, especially if subclinical. In this study, quarter milk samples from clinically healthy cows were harvested to detect pathogens via quantitative PCR (qPCR) and evaluate changes in individual milk traits according to the number of quarters infected and the type of microorganism(s). A commercial qPCR kit was used for detection of Mycoplasma bovis, Mycoplasma spp., Staphylococcus aureus, coagulase-negative staphylococci (CNS), Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Prototheca spp., Escherichia coli, Klebsiella spp., Enterococcus spp. and Lactococcus lactis ssp. lactis. Quarter and pooled milk information of 383 Holstein, 132 Simmental, 129 Rendena, and 112 Jersey cows in 9 Italian single-breed herds was available.
Among the cows with pathogen(s) present in at least 1 quarter, CNS was the most commonly detected DNA, followed by Streptococcus uberis, Mycoplasma bovis, and Streptococcus agalactiae. Cows negative to qPCR were 206 and had the lowest milk somatic cell count. Viceversa, cows with DNA isolated in ≥ 3 quarters were those with the highest somatic cell count. Moreover, when major pathogens were isolated in ≥ 3 quarters, milk had the lowest casein index and lactose content. In animals with pathogen(s) DNA isolated, the extent with whom milk yield and major solids were impaired did not significantly differ between major and minor pathogens.
The effect of the number of affected quarters on the pool milk quality traits was investigated in clinically healthy cows using a commercial kit. Results remark the important negative effect of subclinical udder inflammations on milk yield and quality, but more efforts should be made to investigate the presence of untargeted microorganisms, as they may be potentially dangerous for cows. For a smarter use of antimicrobials, analysis of milk via qPCR is advisable - especially in cows at dry off - to identify quarters at high risk of inflammation and thus apply a targeted/tailored treatment.
乳腺感染是微生物侵入和繁殖乳腺的结果，通常会导致奶牛乳腺炎。尽管为改善奶牛乳房健康做了很多工作，但乳腺炎仍然是奶牛养殖户的一个重大且代价高昂的健康问题，尤其是亚临床乳腺炎。在本研究中，从临床健康奶牛中采集四分奶样，通过定量 PCR（qPCR）检测病原体，并根据感染的奶区数量和微生物类型评估个体奶特性的变化。使用商业 qPCR 试剂盒检测牛支原体、支原体属、金黄色葡萄球菌、凝固酶阴性葡萄球菌（CNS）、无乳链球菌、停乳链球菌、乳房链球菌、产朊假丝酵母、大肠杆菌、克雷伯氏菌属、肠球菌属和乳酸乳球菌乳亚种。意大利 9 个单品种牛群中，383 头荷斯坦牛、132 头西门塔尔牛、129 头伦藤牛和 112 头泽西牛的四分奶和混合奶信息可用。
在至少一个奶区存在病原体的奶牛中，CNS 是最常检测到的 DNA，其次是乳房链球菌、牛支原体和无乳链球菌。qPCR 阴性的奶牛有 206 头，体细胞计数最低。相反，在≥3 个奶区分离出 DNA 的奶牛体细胞计数最高。此外，当≥3 个奶区分离出主要病原体时，牛奶的酪蛋白指数和乳糖含量最低。在分离出病原体 DNA 的动物中，主要和次要病原体的产奶量和主要固体物质受损程度之间没有显著差异。
本研究使用商业试剂盒，调查了在临床健康奶牛中，受感染奶区数量对混合奶质量特性的影响。结果表明，亚临床乳腺炎对产奶量和质量有重要的负面影响，但应进一步努力调查未靶向微生物的存在，因为它们可能对奶牛构成潜在危险。为了更明智地使用抗生素，通过 qPCR 分析牛奶是可取的 - 特别是在干奶期 - 以识别炎症风险高的奶区，并因此进行有针对性/量身定制的治疗。
