Selective dry cow therapy on US dairy farms

Impact on udder health and productivity

Abstract

There is an opportunity to reduce antibiotic (ABX) use at dry-off in US dairy farms, as approximately 80% of herds practice blanket dry cow therapy (BDCT), despite most quarters (~80%) being uninfected at that time. Selective dry cow therapy (SDCT) strategies use screening tests to determine which quarters or cows require ABX treatment at dry-off. 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. However, more research is needed to validate 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 multiherd randomized, positively controlled, clinical trial for the following outcomes; reduction in ABX use at dry-off, clinical mastitis (CM) risk, culling risk, milk yield, and somatic cell count (SCC) in the first 120 days in milk (DIM).