Effect of pre-milking teat disinfection on clinical mastitis incidence in a dairy herd in Northern Queensland, Australia.

Abstract

To determine if a pre-milking teat disinfection protocol would reduce the incidence of clinical mastitis by greater than 50%. Two pre-milking routines were compared in a natural exposure trial. Cows from a single dairy herd were randomly assigned to control (n = 246) and experimental (pre-milking teat disinfection [PMTD]; n = 244) groups. For cows in the control group, the pre-milking routine involved minimal teat-washing, except for cows with wet teat contamination. For cows in the PMTD group, the pre-milking routine involved washing of all teats, dipping with a commercial 0.1% available iodine solution, allowing a minimum of 30 s contact time and then drying of the teats using disposable paper towel. Clinical cases encountered during the trial were recorded and pathogens were isolated from milk samples using standard laboratory methods. The effect of PMTD was determined using multivariable binary logistic regression. Multiparous animals in the PMTD group had higher odds of experiencing clinical mastitis overall and of experiencing clinical mastitis caused by environmental pathogens (odds ratio (OR) 1.97 and 4.11, 95% confidence interval (CI) 1.15-3.38 and 1.49-11.3, respectively). In primiparous animals, pre-milking teat disinfection did not reduce the odds of clinical mastitis by greater than 50% (OR 1.31, 95%CI 0.52-3.29). In this herd, PMTD increased the odds of clinical mastitis. The effectiveness of PMTD to prevent clinical mastitis in pasture-based systems is likely to vary greatly between herds. We therefore recommend against the wholesale use of this practice on Australian farms.