Effect of teat washing on the bacteriological contamination of milk from cows kept under various housing conditions.

The effect of different methods of teat washing on bacterial contamination and sediment levels of the milk of cows kept under 3 housing conditions was studied. By use of an in line milk sampler and steam sterilized clusters the bacterial contamination from the teats after udder preparation was determined directly. The results show that, even under the same housing conditions and teat washing treatments, considerable variation in bacterial counts and sediment level occurred. Overall, washing with hypochlorite (600 mg/l available Cl) and drying with a paper towel gave total counts that were significantly lower than were obtained with the other 4 treatments. The aerobic spore count, in which thermoduric flora predominated, was greatly reduced by drying the teats, but the inclusion of hypochlorite in the wash water had little effect. Coliform contamination was very low (approximately 1/ml) even where the cows' teats were heavily soiled and were not washed. The sediment levels in the milk again showed wide variation and occasional high values (3 mg/l) were recorded for washed cows. In marked contrast to its effect on the bacteriological results, drying had little effect on reducing the sediment.