Evaluation of 1.6% phenol as a premilking and postmilking teat dip in preventing new bovine intramammary infections

We evaluated the effectiveness of a 1.6% phenol-based teat dip using both a teat skin assay and natural exposure field trial. A teat skin assay was co nducted to ascertain the concentration of phenol + phenate to be used in th e field study. One percent and 0.5% iodine, and 0.5, 1.1, and 1.6% phenol phenate were compared using Escherichia coli and Staphylococcus aureus. Lo garithmic reductions for S. aureus were 2.2 and 2.8 for 0.5 and 1% iodine, and 1.3, 2.1, and 2.8 for 0.5, 1.1, and 1.6% phenol + phenate, respectively . Logarithmic reductions for E. coli were 3.3 and 3.8 for 0.5 and 1% iodine , and 1.2, 1.9, and 2.6 for 0.5, 1.1, and 1.6% phenol + phenate, respective ly. A concentration of 1.6% phenol + phenate was chosen as experimental tea t dip, and 0.5% iodine served as control. The field study was conducted at Beltsville (n = 185) and Clarksville (n = 100) dairy herds using a split he rd design. Teat dips were used premilking and postmilking for 12 mo. The nu mber of new intramammary infections (IMI) for the Beltsville herd in iodine and phenol + phenate teat dipped cows were: 29 and 35 for major pathogens, and 81 and 72, for minor pathogens. For the Clarksville herd, number of ne w intramammary infections in iodine and phenol + phenate teat dipped cows w as 9 and 10 for major pathogens, and 50 and 60 for minor pathogens. Rates o f IMI per quarter day per lactation were not different for either herd or w hen herd data were combined. The number of clinical mastitis cases per 100 cows per month were similar in both treatments. The incidences of new IMI a nd clinical mastitis were similar using both dips.