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.

我们的目标是在产犊后第一次挤奶时使用可观察到的内部奶嘴密封剂（ITS）塞来评估四分之一的患病率，并研究产犊后牛奶中ITS残留的持久性。在加拿大魁北克省的6个农场中，对156头接受ITS处理的母牛的557处中的1/4进行了观察性队列研究。生产者观察到在初次挤奶时存在ITS塞子，并且每次挤奶中都存在ITS残留物。分别使用广义逻辑对数混合模型和广义负二项式混合模型研究了各种因素对观察ITS塞的机率和牛奶中ITS残留的持久性的影响。在变干前一天和产犊后两次采样牛奶样品，以进行细菌鉴定，以使用细菌培养物进行MALDI-TOF鉴定来检测乳内感染（IMI）。使用混合逻辑回归模型评估了是否存在ITS插塞和是否存在新的IMI之间的关联。产犊后的内部奶嘴密封剂堵塞现象在后半部和干燥后单独接受ITS的地区相对于抗微生物剂和ITS更为常见。我们观察到了4.0 d（2.3 d）的平均（标准差）持久性。当初次挤奶时仍使用ITS塞子时（四分之一季度的83％），产犊后消除牛奶中ITS残留物的时间要长得多（平均4.5 d），而没有ITS塞子时则为1.2 d。在产犊时使用ITS插头的母牛，我们观察到老年母牛的排泄天数更高。当无法观察到堵塞时，后半部，成年母牛和干燥时间长的母牛会在更长的时间内排泄ITS残留物。缺少插塞和产犊时新IMI几率之间缺乏显着联系，这表明尽管失去了插塞，但奶牛仍受到新IMI的保护。尽管我们能够强调一些统计学上显着的危险因素来解释产犊后ITS残留的持久性，但是观察到的差异通常相对较小，也许与临床无关。总之，在产犊率达到83％的季度之前，一直存在ITS插塞直到第一次挤奶，第一次挤奶时没有ITS插塞的季度似乎受到了新IMI的保护，