Positive-control teat dips should previously been shown efficacious compared with not dipping in either experimental challenge or natural exposure trials. Selecting Experimental Herds, Cows, and Quarters Trials should be conducted in at least two herds. Conduct trials in herds where whole-hearted cooperation of managers to comply with experimental procedures can be attained. Monitor milking equipment and milking management practices carefully and regularly to minimize machine-mediated infections. This is especially necessary in commercial herds where constant supervision by the investigator will not be practical.
All quarters are eligible except quarters with teats that are deformed due to previous injury.
Teat Dipping Dip teats of half the cows in the experimental product in a split-herd design. Cows in the remainder of the herd serve as positive-controls. Ensure that the two groups are milked in the same facility. When a split-udder design is used, either dip two diagonal teats or teats on either the right or left side of each udder with the experimental barrier product. The other two teats on each cow are dipped with the positive-control germicidal product.