Animal Industry Report

Extension Number

ASL R1920



Summary and Implications

One objective of this field investigation was to evaluate the efficacy of extended therapy with pirlimycin hydrochloride with or without vaccination prior and during therapy for S. aureus mastitis. 80% of cows and 44% of quarters were infected with S. aureus. S. aureus infected animals were split into 3 groups with all quarters of all cows treated with extended pirlimycin therapy. One group received a vaccine which had herd autogenous strains (AV), and another group received a new trivalent S. aureus vaccine (TV) at 14 and 1.5 days prior to treatment, and 6 days after treatment started. Cure rates at 32 days post treatment were 18%, 38%, and 56% for treatment only (TO), (AV), and (TV) groups. Cure rates at 60 days post treatment were 14%, 33%, and 33%, respectively when all cows were included in the analysis, and 14, 17, and 14%, respectively, when high SCC quarters with no 60 day data were excluded from the analysis. Coupling vaccination to extended therapy was not successful in this herd ( compared to other data) possibly due to underlying herd nutrition problems. This study also points out that bacteriological cure must be assessed later (>30–45 days post treatment) and/or quarter SCC should be used when multiple therapy strategies are coupled together.

Copyright Holder

Iowa State University