Département de pathologie et microbiologie, Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada J2S 2M2; Canadian Bovine Mastitis and Milk Quality Research Network, Saint-Hyacinthe, Québec, Canada J2S 2M2.
Canadian Bovine Mastitis and Milk Quality Research Network, Saint-Hyacinthe, Québec, Canada J2S 2M2; Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3.
J Dairy Sci. 2018 Jul;101(7):6399-6412. doi: 10.3168/jds.2017-13986. Epub 2018 Apr 5.
Our objectives were to evaluate the prevalence of quarters with an observable internal teat sealant (ITS) plug at first milking following calving and investigate persistency of ITS residues in milk after calving. An observational cohort study was carried out on 557 quarters of 156 cows treated with ITS in 6 farms in Quebec, Canada. The presence of an ITS plug at first milking and ITS residues in milk at each milking were observed by producers. The effects of various factors on the odds of observing an ITS plug and persistency of ITS residues in milk were studied using generalized logistic mixed and generalized negative binomial mixed models, respectively. Milk samples were taken on the day before dry-off and on 2 occasions after calving for bacterial identification to detect intramammary infection (IMI) using bacteriological culture followed by MALDI-TOF identification. The association between the absence of an ITS plug and the presence of new IMI was assessed using a mixed logistic regression model. Internal teat sealant plugs after calving were more often observed in rear quarters and in quarters receiving ITS alone at drying-off versus antimicrobial and ITS. We observed an average (standard deviation) persistency of 4.0 d (2.3 d). When an ITS plug was still present at first milking (83% of quarters), the elimination of ITS residues in milk after calving was significantly longer (4.5 d, on average) compared with 1.2 d when an ITS plug was absent. In cows with an ITS plug at calving, we observed a higher number of days of excretion in older cows. When a plug could not be observed, rear quarters, older cows, and cows with a long dry period duration excreted ITS residues for a significantly longer period. The lack of a significant association between the absence of a plug and the odds of new IMI at calving suggests that despite the loss of the plug, cows were still protected against new IMI. Although we were able to highlight some statistically significant risk factors explaining persistency of ITS residues following calving, observed differences were often relatively small and, perhaps, not clinically relevant. In conclusion, an ITS plug was present until first milking after calving for 83% quarters, quarters without an ITS plug at first milking appeared to have been protected from new IMI, and ITS residues could be observed in milk up to 12 d in milk.
我们的目标是评估产后首次挤奶时可见内部乳头密封剂 (ITS) 塞的 quarters 比例，并研究产后牛奶中 ITS 残留的持久性。在加拿大魁北克的 6 个农场对 156 头奶牛的 557 个 quarters 进行了一项观察性队列研究。生产者观察了首次挤奶时是否存在 ITS 塞以及每次挤奶时是否存在 ITS 残留。使用广义逻辑混合和广义负二项式混合模型分别研究了各种因素对观察 ITS 塞和牛奶中 ITS 残留持久性的影响。在干奶前一天和产后 2 次挤奶时采集牛奶样本，用于细菌鉴定，使用细菌培养和 MALDI-TOF 鉴定检测乳腺炎（IMI）。使用混合逻辑回归模型评估没有 ITS 塞与新 IMI 存在之间的关联。与抗菌剂和 ITS 相比，产后后部 quarters 和仅接受 ITS 治疗的 quarters 更常观察到 ITS 塞。我们观察到平均（标准差）持续时间为 4.0 天（2.3 天）。当首次挤奶时仍存在 ITS 塞（83%的 quarters）时，产后 ITS 残留从牛奶中消除的时间明显更长（平均 4.5 天），而当没有 ITS 塞时，仅为 1.2 天。在分娩时有 ITS 塞的奶牛中，我们观察到年龄较大的奶牛的排泄天数更多。当无法观察到塞子时，后部 quarters、年龄较大的奶牛和干奶期较长的奶牛会排泄 ITS 残留更长的时间。在没有塞子时，观察到的新 IMI 缺失与新 IMI 缺失之间缺乏显著关联表明，尽管塞子丢失，奶牛仍能免受新 IMI 的侵害。尽管我们能够突出显示一些解释产后 ITS 残留持久性的统计学上显著的风险因素，但观察到的差异通常相对较小，也许在临床上并不重要。总之，83%的 quarters 在产后首次挤奶时仍存在 ITS 塞，首次挤奶时没有 ITS 塞的 quarters 似乎可以防止新的 IMI，并且可以在牛奶中观察到多达 12 天的 ITS 残留。
