Bedding can affect mammary health of dairy cows. The objectives of this study were to evaluate clinical mastitis incidence in cows housed on recycled manure solids bedding and, more specifically, to determine which pathogens were involved. We followed 26 recycled manure solids farms and 60 straw-bedded farms as a comparative group during 1 year (2018–2019). For each episode of clinical mastitis, defined as a visual alteration of the milk, with or without local or systemic signs of infection, producers sampled aseptically the affected quarter, provided some details about the animal, and sent the sample to the research team at the Université de Montréal. We received and analyzed 1,144 milk samples. The samples were cultured according to the National Mastitis Council guidelines and the different colony phenotypes were subsequently identified with mass spectrometry. In 54.6% of CM cases, a single phenotype of bacteria was cultured (pure culture), while two different phenotypes were found in 16.8% of the samples (mixed culture), and no growth was observed in 14.4% of the samples. Samples with three or more phenotypes were considered contaminated and were not included in the pathogen-specific analyses (14.3% of the submitted samples). The most frequently identified bacterial species in pure and mixed culture in farms using recycled manure solids were Streptococcus uberis (16.0%), Escherichia coli (13.8%), Klebsiella pneumoniae (13.2%), Streptococcus dysgalactiae (6.2%), and Staphylococcus aureus (3.4%). In straw farms, the most frequent species were S. aureus (16.6%), S. uberis (11.0%), E. coli (9.1%), S. dysgalactiae (8.0%), and K. pneumoniae (1.1%). The incidence of clinical mastitis (all cases together) was not higher in recycled manure solids farms (14.0 cases/100 cow-year; 95% CI: 8.3–23.7) compared with straw-bedded farms (16.3 cases/100 cow-year; 95% CI: 9.0–29.6). However, K. pneumoniae clinical mastitis episodes were 7.0 (95% CI: 2.0–24.6) times more frequent in recycled manure solids farms than in straw farms. Adjusted least square means estimates were 1.6 K. pneumoniae clinical mastitis cases/100 cow-year (95% CI: 0.8–3.4) in recycled manure solids farms vs. 0.2 cases/100 cow-year (95% CI: 0.1–0.6) in straw-bedded farms. Klebsiella pneumoniae clinical mastitis is in general severe. Producers interested in this bedding alternative need to be aware of this risk.

垫料会影响奶牛的乳房健康。本研究的目的是评估饲养在回收粪便固体垫料上的奶牛的临床乳腺炎发病率，更具体地说，确定涉及哪些病原体。我们在 1 年（2018-2019 年）期间跟踪了 26 个回收粪便固体农场和 60 个稻草农场作为比较组。对于每一次临床乳腺炎（定义为牛奶的视觉变化，有或没有局部或全身感染迹象），生产者对受影响的季度进行无菌采样，提供有关动物的一些详细信息，并将样本发送给研究小组蒙特利尔大学。我们收到并分析了 1,144 个牛奶样品。根据国家乳腺炎委员会指南培养样品，随后用质谱法鉴定不同的菌落表型。在 54.6% 的 CM 病例中，培养了单一表型的细菌（纯培养），而在 16.8% 的样本（混合培养）中发现了两种不同的表型，在 14.4% 的样本中未观察到生长。具有三种或更多表型的样品被认为是受污染的，不包括在病原体特异性分析中（占提交样品的 14.3%）。在使用回收粪便固体的农场中，在纯培养和混合培养中最常见的细菌种类是 在 14.4% 的样品中没有观察到生长。具有三种或更多表型的样品被认为是受污染的，不包括在病原体特异性分析中（占提交样品的 14.3%）。在使用回收粪便固体的农场中，在纯培养和混合培养中最常见的细菌种类是 在 14.4% 的样品中没有观察到生长。具有三种或更多表型的样品被认为是受污染的，不包括在病原体特异性分析中（占提交样品的 14.3%）。在使用回收粪便固体的农场中，在纯培养和混合培养中最常见的细菌种类是乳房链球菌 (16.0%), 大肠杆菌 (13.8%), 肺炎克雷伯菌 (13.2%), 停乳链球菌 (6.2%) 和 金黄色葡萄球菌(3.4%)。在稻草农场，最常见的物种是金黄色葡萄球菌 (16.6%), 乳房链球菌 (11.0%), 大肠杆菌 (9.1%), 停乳链球菌 (8.0%) 和 肺炎克雷伯菌(1.1%)。与稻草农场（16.3 例/100 头牛年）相比，循环粪便固体农场（14.0 例/100 头牛年；95% CI：8.3-23.7）的临床乳腺炎发病率（所有病例加在一起）并不高； 95% 置信区间：9.0–29.6）。然而，肺炎克雷伯菌在回收粪便固体农场中，临床乳腺炎发作的频率是秸秆农场的 7.0（95% CI：2.0-24.6）倍。调整后的最小二乘均值估计值为 1.6肺炎克雷伯菌 临床乳腺炎病例/100 头牛年（95% CI：0.8-3.4）在回收粪便固体农场与 0.2 例/100 头牛年（95% CI：0.1-0.6）在稻草农场。 肺炎克雷伯菌临床乳腺炎一般很严重。对这种床上用品替代品感兴趣的生产商需要意识到这种风险。