Botulism in an Oregon dairy cow herd

Of 18 sick cows in a 100-cow dairy herd in Oregon, 14 died despite treatment. The cows were being fed high-moisture whole corn and alfalfa and rye haylage from pit silos. Signs of illness were anorexia, severe depression, and reduced milk production. Necropsy revealed only hyperemia of the abomasal mucosa and dilated, gas filled large intestine. On the basis of response to treatment, laboratory findings, necropsy findings, and herd history, a tentative diagnosis of botulism was made. This diagnosis was confirmed by results of mouse inoculation tests. Injections of extract from the corn killed mice that were not protected by botulinum antitoxin.