Field trial evaluation of two teat dips containing nisin or polyvinylpyrrolidone iodophor designed for use before and after milking.

In a first trial involving six commercial dairy herds and 291 cows for a period of eight months, pre-milking udder sanitation by dipping teats in a 0.25% polyvinylpyrrolidone (PVP) iodophor product followed by wiping with paper towels was compared in each herd with traditional teat washing and wiping with individual udder cloths. The incidence of new intramammary infections by Staphylococcus aureus, Streptococcus uberis and Corynebacterium bovis were significantly (P < 0.05) reduced, respectively by 48%, 60% and 47%. There were no significant differences in the two groups of cows for other intramammary infections, total bacterial counts, clostridia spore counts, iodine residues in milk or teat condition scores. In a second trial involving nine commercial dairy herds and 367 cows for a period of seven months, a teat dip containing nisin used before and after milking was compared in each herd with a classical 0.5% iodophor product used in the same way. There was no significant difference in the incidence of new intramammary infections, in spite of a higher rate of new Staphylococcus aureus infections in the group of cows teat-dipped with the nisin product (P = 0.06). It was concluded that pre-dipping with teat dips specifically designed to be safely used before milking can be more efficient than traditional pre-milking udder preparation. These teat dips, when used before and after milking, seem to be as efficient as products which should normally be restricted to post-milking use.