Examination of pre-milking teat disinfectant contact times using the excised teat model
Use of pre-milking teat disinfectants is a common practice used to aid in the control of mastitis which is the most common and expensive disease in the US dairy industry. Effectiveness of pre-milking teat disinfectants in reducing pathogen load on teat skin is influenced by the duration these disinfectants remain on the teat skin, although this has not been adequately investigated. The objective of this study was to determine the percentage reduction in mastitis pathogen load, four environmental and four opportunistic (n = 8), on teat skin with disinfectant contact times of 15, 30, and 45 sec. Three commercially available disinfectants were tested: 0.25% (A) and 0.5% (B) iodophor, and 1% H2O2 (C). Excised teats, collected from an abattoir, were washed, dried, hung from a dowel rod, dipped in 70% isopropyl alcohol and allowed to dry. Once dry, teats were dipped in challenge solution of approximately 107 colony forming units/ml of a pathogen. After 5 minutes, teats were dipped with desired disinfectant and rinsed with quench solution upon achieving test contact time. Rinse was serially diluted, plated, incubated for 18-48 hr, and enumerated. Main effect differences were observed within dips, contact times, and species (P < 0.0001). Dip A percentage log reduction across all species was 28% at 15 sec, 35.7% at 30 sec, and 39.2% at 45 sec, SE ± 1.7%. Dip B, percentage log reduction was 36% at 15 sec, 41.2% at 30 sec, and 43.8% at 45 sec, SE ± 1.7%. Dip C, the least efficacious disinfectant, had log reductions of 26% at 15 sec, 25.5% at 30 sec, and 28% at 45 sec, SE ± 1.7%. In summary percentage log reductions across all pathogens and dips at 15, 30, and 45 sec were 30% ± 0.97%, 34% ± 0.97%, and 37% ± 0.96% respectively, all significantly different from one another (P < 0.05). The relationship between duration of contact time and percentage log reduction demonstrates the importance of allowing adequate contact time to maximize pathogen reduction and reduce the risk of mastitis.
Keywords: mastitis, teat disinfectant, contact time