Pilot study: Refining a culture-guided selective dry cow therapy program to enhance antimicrobial stewardship on dairy farms

Abstract

Selective dry cow therapy (SDCT) programs typically use either milk culture or algorithm methods to identify cows with a high risk of infection, and thereby warranting antimicrobial therapy (AMX) at dry off (DO). Multiple studies have demonstrated that SDCT programs can maintain future cow health while signifi­cantly reducing antimicrobial use (AMU), as compared to blan­ket DCT (BDCT). However, we may be able to further reduce AMU at DO by targeting only specific types of intramammary infection (IMI) that will benefit from AMX. A recent meta-analysis concluded that IMI caused by Streptococcus spp. or Streptococcus-like organisms (SSLO) do benefit from DC therapy, while IMI caused by coliform or non-aureus Staph spp. (NAS) do not. Similarly, IMI caused by other Gram-positive bacteria, in­cluding S. aureus, occur with a relatively low frequency in most herds, and often do not respond to AMX. The Minnesota Easy® Focus® media is selective for SSLO growth in milk samples. This pilot study aimed to evaluate the effect of a SDCT program that identifies and treats only IMI caused by SSLO (vs. BDCT) on quarter health and AMU.