Milk from 34 dairy herds was tested over a 12-month period using a mastitis evaluation program in which Streptococcus agalactiae, Staphylococcus aureus and leucocytes were counted. There was a significant decrease in the total mastitic bacterial count (S. agalactiae plus S. aureus) over the testing period; however, the curve was bimodal, showing high points in the winter and summer months. The leucocyte count alone was not a good indicator of the mastitic condition of the herd. In approximately 12% of the test results, there was a high bacterial count with a low leucocyte count or a high leucocyte count with a low bacterial count.
2Present address:Office of Health Affairs, Food and Drug Administration, Rockville, MD 20857.