On-farm assessment of the antibacterial efficacy of hoof disinfectants for dairy cows

Digital dermatitis is a major cause of infectious lameness in dairy cows. Disinfectant footbaths and sprays are used for disease control. Laboratory tests of disinfectant efficacy cannot match the complexity of organic challenges on farms. This study developed an on-farm test of antibacterial efficacy for hoof disinfectants applied as a topical spray or in a footbath. Two trials were carried out, one testing disinfectants applied by topical spray and the other testing the same products after use in a footbath that had been walked through by 100 cows. Products were copper sulphate (positive control), P1 (acetic and peracetic acid based), P2 (amine) and P3 (lactic acid and chlorocresol), all used at 5% concentration. A pre- and post- treatment swab methodology was used and log reduction in aerobic colony count was determined. For spray application, the log reduction caused by copper sulphate was smaller than P1 but not different to P2 or P3. For the used footbath disinfectants, the log reduction caused by copper sulphate was larger than P2 but not different to P1 or P3. This testing method can discriminate products that have higher or lower antibacterial efficacy than copper sulphate under farm conditions when different application methods are used.