Abstract Selective dry cow therapy (SDCT) is one measure suggested to reduce the use of antibiotics on dairy farms. This procedure may have a negative impact on dairy herds, affecting both milk yield and quality. The aim of this observational study was to evaluate the implementation of a SDCT protocol based on the treatment only of cows with SCC at last individual milk test before drying-off >100,000 cells/mL (primiparous cows) or >200,000 cells/mL (pluriparous cows) on udder infection status. We also assessed the association between cow and management factors with the likelihood of cure or of new IMI across the dry period. The study considered 516 dairy cows (2064 quarters), and only 53% of the cows were treated with antibiotics. Before drying-off, 999 quarters (49.1%) were bacteriological negative at two consecutive samples. After calving the negative quarters were 1004 (49.3%). The likelihood of a cure across the dry period was significantly associated with parity, drying-off length and teat sealant application, while the likelihood of new IMI across the dry period was associated to all the risk factors considered (parity, dry period length, teat sealant application, infections status at drying-off and type of long-acting antibiotic applied). The application under field conditions of the proposed SDCT protocol showed to feasible, and to largely reduce the use of antimicrobials at drying-off, with a relatively small impact on cow health. Highlights First observational study in of Italian dairy herds on the application of a selective dry-cow therapy protocol based on SCC. The study showed as a reduction of about 50% in antimicrobial usage at drying off can be achieved. Management and cow factors affect the likelihood of a cure of a new intramammary infection across the dry period.

中文翻译：

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基于个体体细胞计数阈值的选择性干牛治疗方案应用的观察性研究

摘要 选择性干奶牛疗法（SDCT）是建议减少奶牛场抗生素使用的一项措施。该程序可能对奶牛群产生负面影响，影响牛奶产量和质量。这项观察性研究的目的是评估 SDCT 方案的实施情况，该方案基于在干燥 >100,000 个细胞/mL（初产奶牛）或 >200,000 个细胞/mL（多产奶牛）之前的最后一次单独牛奶测试中仅治疗患有 SCC 的奶牛。奶牛）乳房感染状态。我们还评估了奶牛和管理因素与干奶期治愈或新 IMI 的可能性之间的关联。该研究考虑了 516 头奶牛（2064 个季度），只有 53% 的奶牛接受了抗生素治疗。在烘干之前，999 个季度 (49.1%) 在两个连续样本中呈细菌学阴性。产犊后的负季度为 1004 (49.3%)。整个干奶期治愈的可能性与胎次、干奶期长度和乳头密封剂的应用显着相关，而跨干奶期新 IMI 的可能性与所有考虑的风险因素（胎次、干奶期长度、乳头密封剂的应用、干燥时的感染状态和应用的长效抗生素类型）。提议的 SDCT 协议在田间条件下的应用表明是可行的，并且在很大程度上减少了干奶时抗菌剂的使用，对奶牛健康的影响相对较小。亮点 在意大利奶牛群中应用基于 SCC 的选择性干奶牛治疗方案的第一项观察性研究。研究表明，在干燥时抗菌剂的使用量可以减少约 50%。