Occurrence: Worldwide. Species affected: All. Age affected: Young chicks, usually between 15th and 30th day of life.

Causes: Deficiency of Vitamin E in the diet. Vitamin E is heat labile. It can also be caused by deficiency of selenium. As selenium levels in the soil are very variable, cereal grains are often suboptimal in selenium.

Effects: Incoordination, tremors, rapid contractions and relaxation of the legs results in the name "crazy ch...