Inheritance of Tetanic Torticollar Spasms in Turkeys

Abstract

Tetanic torticollar spasms (TT) refers to a neurologic disorder observed in a line of Medium White turkeys. The condition is characterized by the dorsomesial extension of the neck and head such that the head rests on the back with the beak directed upwards. The spasms vary in duration 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 induced by sudden loud noises and eating and drinking. When expressed in poults at hatching the condition is usually lethal due to starvation and dehydration. Typically, TT is expressed during the first 7 days posthatching but can be as late as 18 wk of age. Breeding tests indicate that 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 proposed.