Bovine salmonellosis attributed to Salmonella anatum-contaminated haylage and dietary stress

An epizootic of salmonellosis in a dairy herd started 2 days after the feeding of a new shipment of medicinal-smelling soybean meal. Clinical findings consisted of diarrhea or fever (greater than 39 C), or both, and markedly decreased milk production. The attack rate was 73% in lactating cows, 3% in calves, and 0% in nonlactating cows. There were no deaths, but 1 cow aborted a late-term fetus. Salmonella anatum was isolated from feces, milk, pharynx, uterine fluid, haylage, and bird droppings from a hayfield. The epidemiologic findings suggested that haylage contaminated by wild birds and improperly stored in a silo was the source of infection and that the precipitating event was ingestion of spoiled soybean meal.