The dry period is a critical time in the lactation cycle,
being the optimum time to cure existing intramammary
infection (IMI) as well as encompassing the periods of
highest susceptibility to new infection. Currently, IMI
in the dry period is controlled with antibiotic dry cow
therapy. The aim of this randomized control trial was
to investigate different dry cow therapy regimens by
stratifying cows by likely infection status at drying off in
herds with low somatic cell count (SCC; bulk milk SCC
90% in
quarters receiving antibiotic. Combination treatment of
high-SCC infected cows resulted in an increased likelihood
of being pathogen free post-calving (odds ratio =
1.40; 95% credibility interval = 1.03–1.90). The benefits
of combination treatment of low-SCC uninfected cows