In cattle the disease is most often caused by eating the preformed toxin. Classically, botulism has been commonly associated with pica or craving for phosphorus in phosphorus-deficient animals pastured on soils lacking phosphorus. In their search for phosphorus, cattle eat bones or soil which contain the botulism bacteria and toxin. Individual animals or groups of cattle can be affected. It may also occur with contaminated feeds where the bacteria found a suitable place without oxygen to grow and produce toxin.
Animal carcasses provide a suitable place for the botulism bacteria to grow.
If the carcasses are baled into hay or packed into silage, cattle may be exposed to the toxins at some later time. This was the situation in a recent case presented to the California Veterinary Diagnostic Laboratory. Botulism was diagnosed in a California dairy herd where over 400 dairy cows died following eating feed contaminated by a dead cat. Botulism is diagnosed by detecting the toxin, not the bacteria, in the blood, gut content or feed. Samples are injected into mice some of which have been protected by specific botulism antitoxin.