Effects of experimental challenge of ewes with Mannheimia haemolytica on subsequent milk composition.

The objective was to describe the physicochemical changes during the early phase of subclinical mastitis and to associate them with pathological findings. A Mannheimia haemolytica strain was deposited into one teat duct of 25 ewes and the clinical, bacteriological, cytological, physicochemical (pH, milk composition), gross-pathological and histological findings were subsequently recorded. The organism was consistently isolated from samples of teat duct material (140/150) but not from mammary secretion (50/150).