Post-milking iodine teat skin disinfectants. I. Bactericidal efficacy

An iodine teat skin disinfectant tested in lactating cows over a range of concentrations, 100 to 10 000 mg available iodine/l(mgavI/l) was found bactericidally effective against Staphylococcus aureus when containing 1000 mg avI/l or greater. Against Streptococcus dysgalactiae 5000 mg avI/l or greater was bactericidally effective. The addition of glycerine to a disinfectant containing 5000 or 1000 mg avI/l at levels of 225 ml/l and 105 ml/l, respectively, resulted in a reduction in bactericidal efficacy of the disinfectant. Emulsified paraffin added at concentrations of between 50 and 500 ml/l had no effect on the efficacy of the 5000 mg avI/l disinfectant, but the addition of 200 ml/l emulsified paraffin to a 1000 mg avI/l disinfectant significantly reduced its efficiency. Iodine disinfectants containing emulsified paraffin phase separated rapidly during storage, and the bactericidal efficacy of the phases differed significantly and diminished with time.