Randomized Controlled Trial Investigating the Effect of Two Selective Dry Cow Therapy Protocols on Antibiotic Use and Udder Health

摘要

Approximately 80% of U.S. dairy herds practice blanket dry cow therapy (BDCT), despite most quarters (~80%) being uninfected at that time (Rowe et al., Accepted). Consequently, antibiotic (ABX) use at dry off could be reduced using selective dry cow therapy (SDCT) strategies. A small number of trials conducted in North America recently found that SDCT reduced ABX use by up to 60% without negatively impacting udder health, culling risk, or milk production when compared to BDCT (Cameron et al., 2015, Vasquez et al., 2018). However, more research is needed to investigate SDCT before it can be widely implemented. The objective of this study was to compare 2 SDCT approaches (Culture-based or Algorithm-based) against BDCT in a multi-herd randomized, positively controlled, clinical trial for health indicators during the dry period (quarter-level intramammary infection [TMI] cure risk, new IMI risk, and IMI risk at 1-13 days in milk, DIM) and during the first 120 DIM (clinical mastitis [CM] and culling ordeath risk and test-day milk somatic cell count [SCC] and milk yield).