Cattle Feeding: What Is Polioencephalomalacia?
Cause: Polioencephalomalacia is caused by a disturbance in thiamine metabolism. Thiamine is required for a number of important nervous system functions. This disease most commonly affects young, fast growing cattle on a high concentrate ration and may result from a thiamine-deficient diet, an increase in thiaminase (an enzyme that breaks down thiamine) in the rumen or an increase in dietary sulfates.
A thiamine-deficient diet is usually associated with an increase in the dietary concentrate:roughage ratio. When concentrates (feed grains such as corn) are increased and roughage (forage, cottonseed hulls, etc.) is decreased in the diet, rumen pH drops. This increases the numbers of thiaminase-producing bacteria in the rumen and decreases the amount of total useable thiamine. Thiaminase breaks down the form of thiamine that the animal could normally use. Some species of plants produce thiaminase and can cause a decrease in the useable amount of thiamine when consumed. Examples of these types of plants include kochia, bracken fern and equisetum.