Toxic ergot alkaloids are produced by Claviceps spp, which grow on cereal grains. Rye is especially affected, but also wheat and other cereal grains. The mycotoxins form in the sclerotium, a visible, hard, dark mass of mycelium that displaces the grain tissue. Within the sclerotium are the ergot alkaloids, which target: the nervous system, causing convulsive and sensory neurologic disorders; the vascular system, causing vasoconstriction and gangrene of the extremities; and the endocrine system, including neuroendocrine control of the anterior pituitary gland. In chicks, the toes become discolored due to vasoconstriction and ischemia. In older birds, vasoconstriction affects the comb, wattles, face, and eyelids, which become atrophied and disfigured. Vesicles and ulcers develop on the shanks of the legs and on the tops and sides of the toes. Reductions in feed consumption and egg production are seen.