Chicken muscular dystrophy: an inherited disorder of flight.

Dystrophic (University of California, Davis, line 413) and normal control (Davis, 1. 412) chicks (Gallus domesticus) between 7 and 49 days old were tested for flight-related pathology and righting ability. Drop-evoked lateral flight developed in control chicks between 7 and 13 days. Dystrophic chicks never developed lateral flight. Both dystrophic and control chicks showed drop-evoked wing-flapping on the day of hatching. Also, dystrophic chicks had a normal but slightly higher drop-evoked flapping rate than controls at 13 days. Thus, the neural circuits that initiated and generated the rate of drop-evoked wing-flapping, present in dystrophic chicks at birth, were intact at 13 days, when deficiencies in lateral flight and righting ability were already present. The righting behavior of control chicks was superior to that of dystrophic chicks at all ages from 7 to 49 days.