INHERITANCE OF TETANIC TORTICOLLAR SPASMS IN TURKEYS

Tetanic torticollar spasms (TT) refers to a neurologic disorder observ ed in a line of Medium White turkeys. The condition is characterized b y the dorsomesial extension of the neck and head such that the head re sts on the back with the beak directed upwards. The spasms vary in dur ation from 1 to 5 s to longer than 1 min followed by the resumption of normal posture. The spasms appear to be spontaneous but can be induce d by sudden loud noises and eating and drinking. When expressed in pou lts at hatching the condition is usually lethal due to starvation and dehydration. Typically, TT is expressed during the first 7 days postha tching but can be as late as 18 wk of age. Breeding tests indicate tha t TT is the expression of a sex-linked recessive gene with incomplete penetrance, 86%. Microscopic examination of the otoconia in the inner ears and histologic examination of the cerebellum and brainstem of TT turkeys have not revealed any abnormality. The gene symbol tt is propo sed.