Mechanics of standing in birds: functional explanation of lameness problems in giant turkeys.

1. The parameters used for the mechanics of standing in birds are defined and compared for two strains of turkeys, a giant, broad-breasted strain (up to 40 kg), the result of artificial selection, and a traditional, smaller bird (9 kg), in order to show whether the mechanics of standing are modified by selection. 2. Using a geometrical similarity hypothesis, it was found that, although the locomotor apparatus of both strains are similar, the stresses on the pelvic muscles of broad-breasted turkeys are increased. This is induced by the anterior position of the centres of gravity of their trunks, the result of selected pectoral hypertrophy. 3. The modification to the mechanics of standing may be related to the increase in locomotor disease in strains of giant turkeys.