Comparison of teat dips with differing iodine concentrations in prevention of mastitis infection

Six commercial dairy herds were used to test the relative efficacy of three concentrations of iodine as a teat dip over 12 mo. Concentrations were .1, .25, and 1% iodine with free iodine contents of 3.5, 4.0, and 1.0 ppm. Two concentrations were compared in each herd. The greatest number of new infections (71) occurred in approximately 120 cows whose teats were dipped with the 1% iodine dip, and the fewest (52) occurred in a similar number of cow quarters dipped in .1% iodine; however, differences were not significant. Clinical mastitis was highest in the 1% group. If all clinical mastitis were the result of infection, even if bacteria were not isolated from the pretreatment sample or from samples collected at the start of the study and those quarters were added to the totals, then reduction of new infection with the .1% product would be significant.