Department of Agricultural and Environmental Sciences, University of Milan, via Celoria 2, 20133 Milan, Italy.
Department of Agricultural and Environmental Sciences, University of Milan, via Celoria 2, 20133 Milan, Italy.
Animal. 2023 Oct;17(10):100982. doi: 10.1016/j.animal.2023.100982. Epub 2023 Sep 7.
The routine use of intramammary antimicrobial products in all dairy cows at the beginning of the dry period is no longer allowed in European Union (EU) countries due to the new Regulation (EU) 2019/6 to reduce antimicrobial resistance. This study investigated the application of a selective dry cow therapy scheme and the risk factors of high individual milk somatic cell count (SCC) and individual neutrophil count in early lactation, as a response to the application of a selective dry cow therapy (SDCT) protocol. The study was carried out on three commercial farms, and a total of 243 lactating cows were monitored at the end of lactation and at the beginning of the next one, 91 of which were dried off without the use of antimicrobials (NoT) based on milk SCC, differential somatic cell count (DSCC), and the response of Vetscan DC-Q milk analyser, using a secret algorithm. The remaining 152 cows received antimicrobials (T). After calving, similar means were observed between the two treatment groups for SCC (4.8 vs 4.9 log cells/ml for T and NoT, respectively, P = 0.5) and total milk leucocyte count (TLC) (5 vs 5.1 log cells/ml for T and NoT, respectively, P = 0.7) in milk. However, the use of antimicrobials led to a lower DSCC (58 vs 64% for T and NoT, respectively, P = 0.01) and lower percentage of neutrophils (59 vs 64% for T and NoT, respectively, P = 0.05), although the levels of DSCC and percentage of neutrophils in cows dried off without antimicrobials remained lower than the risk threshold suggested by the international literature. A logistic regression was computed after the application of selective dry cow therapy to identify risk factors of high milk SCC (≥100 000 cells/mL) at the beginning of lactation. Increased milk SCC after calving was related to high SCC at the end of lactation and abandonment of antimicrobial therapy at dry-off. Moreover, the length of the dry period, milk protein content, and flank cleanliness in the last test day before dry-off were other factors in the logistic regression. Neutrophil counts at the beginning of the next lactation were affected by the same factors that influenced SCC, together with milk production, TLC, and macrophages on the last test day. The results obtained in these studied farms showed that selective dry cow therapy may be applied without adversely affecting the next lactation.
由于新的欧盟法规（EU）2019/6 规定减少抗生素耐药性，欧盟国家已不再允许在干奶期开始时对所有奶牛常规使用乳房内抗菌产品。本研究调查了应用选择性干奶牛治疗方案的情况，并分析了个体牛奶体细胞计数（SCC）和个体中性粒细胞计数高的风险因素以及早期泌乳，以应对选择性干奶牛治疗（SDCT）方案的应用。该研究在三个商业农场进行，共有 243 头泌乳奶牛在泌乳期末和下一个泌乳期开始时进行监测，其中 91 头根据牛奶 SCC、差异体细胞计数（DSCC）和 Vetscan DC-Q 牛奶分析仪的反应，不使用抗菌药物（NoT）进行干燥。剩余的 152 头奶牛接受了抗菌药物（T）治疗。产犊后，两组的 SCC（T 和 NoT 分别为 4.8 和 4.9 log 细胞/ml，P=0.5）和总乳白细胞计数（TLC）（T 和 NoT 分别为 5 和 5.1 log 细胞/ml，P=0.7）在牛奶中相似。然而，使用抗菌药物会导致 DSCC 较低（T 和 NoT 分别为 58%和 64%，P=0.01）和中性粒细胞百分比较低（T 和 NoT 分别为 59%和 64%，P=0.05），尽管没有使用抗菌药物干燥的奶牛的 DSCC 和中性粒细胞百分比仍低于国际文献建议的风险阈值。在应用选择性干奶牛治疗后，进行了逻辑回归分析，以确定泌乳初期牛奶 SCC（≥100000 个细胞/ml）高的风险因素。产犊后 SCC 增加与泌乳期末 SCC 高和干奶期放弃抗菌治疗有关。此外，干奶期长度、牛奶蛋白含量和干奶前最后一天的侧腹清洁度是逻辑回归中的其他因素。下一个泌乳期的中性粒细胞计数受影响 SCC 的相同因素以及产奶量、TLC 和最后一次检测日的巨噬细胞的影响。在这些研究农场获得的结果表明，选择性干奶牛治疗可以在不影响下一个泌乳期的情况下应用。
