CHEESE-BLOWING ANAEROBIC SPORES IN BULK MILK FROM LOOSE-HOUSED AND TIED DAIRY-COWS

Two management systems for dairy cows, tied and loose-housing with cub icles, were compared in a longterm (2 years) experiment. During experi mental periods in each year the numbers of cheese-destroying anaerobic spores were determined by most probable number technique (MPN) and by a filtration method followed by ELISA confirmation of Clostridium tyr obutyricum, C. butyricum and C. sporogenes. Total counts and psychrotr ophic bacteria were also analysed. Samples from bulk milk were taken e very second day for 7 weeks in the first year and for 5 weeks in the s econd year. Feeds, including grass and alfalfa silage, and pre-milking routines were kept identical in the management systems. Total counts in both systems were at a low level and differences were, on average, less than a few thousand CFU per ml. In both years, more than twice th e number of spores were found in the bulk milk from loose-housed cows than from tied cows. The differences were significant when detected by the ELISA method in both years, whereas in the first year the MPN met hod did not give reliable results. There was a large difference betwee n the two years in anaerobic spore level (tenfold more spores in the f irst year than in the second), caused by differences in silage quality . Although feeds, milking routines and animals were the same or unifor m for the two management systems, differences between the systems were distinctly reflected in the spore levels of the milk. The ELISA metho d offers a more accurate tool of determining cheese-destroying anaerob ic spores than MPN techniques. The unexpected lower values for tied co ws could be explained by the more intensive care and working time used on scraping, litter management and thorough cleaning of dirty teats t han for the loose-housed cow. It may be concluded, from this and other studies, that feed quality is of the greatest importance for the spor e content in milk. The scraping, litter management and cleaning of the teats are important factors that may eliminate a less optimal hygieni c function of the environment of the cow.