Bacillus cereus in the housing environment of dairy cows

The spore-forming bacterium Bacillus cereus can survive pasteurisation and thus a limiting factor for the shelf life of pasteurized milk. The occurrence of B. cereus spores in the housing environment of dairy cows was investigated and the routes of contamination elucidated also measures to improve hygiene in cubicles and alleys were tested. High numbers of spores were found in deep sawdust bedded cubicles hence a source of contamination of milk via soiled teats. In laboratory tests, type of different bedding material, pH, and the availability of nutrient in form of faeces in the beds were shown to be important factors for the growth of B. cereus. In deep sawdust bedded cubicles more frequent adding of fresh bedding and entire bed replacement had a limited effect on reducing spore content in the beds. It was shown by experimentally feeding spores to cows that highly contaminated feed could be a potential source of contamination via faeces and soiled teats. The effects of different premilking teat-cleaning methods were evaluated on experimentally spore contaminated teats. The most effective method in reducing the milk spore content (96 % reduction) was the use of a moist washable towel with or without soap followed by drying with a dry paper towel. Mechanical scrapers on top of the slatted floor reduced the amount of manure on alley floor, hence reducing the faecal contamination in the cubicles, and improving the hygiene score of udder and teats. The drainage capacity of slatted floors was tested in a laboratory arrangement. For loose faeces from high-yielding dairy cows, the greater void ratio the better drainage capacity, irrespective of slat and slot widths was obtained.