An unusual epizootic of actinobacillosis in dairy heifers

Actinobacillosis developed in a group of 52 Holstein-Friesian replacement heifers. They were confined to 4 pens in a barn. Cervical abscesses were first observed by the owner in 1 heifer a month after the heifers were fed chopped haylage that was particularly dry, tough, and stemmy. During the weeks that followed, morbidity reached 73% in heifers given the feed. Calves up to 4 months old were not given the haylage and did not develop the disease. Standard bacteriologic methods were used to identify Actinobacillus lignieresii from exudate of abscesses. A biopsy of superficial granulomatous tissue of the lips revealed fibers thought to be of plant origin. Affected cattle recovered in 3 to 6 months. The lesions of 3 cattle given sodium iodide intravenously and of 4 given streptomycin regressed sooner than those given penicillin or no treatment.