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 defi ned and compared for two strains of turkeys, a giant, broad-breasted s train (up to 40 kg), the result of artificial selection, and a traditi onal, smaller bird (9 kg), in order to show whether the mechanics of s tanding are modified by selection. 2. Using a geometrical similarity h ypothesis, it was found that, although the locomotor apparatus of both strains are similar, the stresses on the pelvic muscles of broad-brea sted turkeys are increased. This is induced by the anterior position o f the centres of gravity of their trunks, the result of selected pecto ral hypertrophy. 3. The modification to the mechanics of standing may be related to the increase in locomotor disease in strains of giant tu rkeys.