RESUMEN
Thirty min occlusion of the subclavian artery of commercial strains of adult light-weight and broiler breeder fowls had no adverse effect on the supracoracoid muscle. When this temporary arterial occlusion was combined with electrically-induced contractions of the supracoracoid for a period of 4 min, myopathy occurred in both types of bird. A similar degree of muscle contraction without any interference with the arterial supply induced necrosis of the supracoracoid of the broilers but not of the light-weight strain. The superficial pectoral muscle of the broilers was not adversely affected by stimulation. The necrotic muscle resembled that in spontaneous deep pectoral myopathy. These findings are discussed with particular reference to the vascular supply to the muscle and although they are not considered to be due to pre-existing occlusive lesions of the arteries, the basic nature of the causative defect remains obscure. On the basis of this work carried out on commercial broiler breeder stock maintained at the Poultry Research Centre, we conclude that a relatively small number of electrically-stimulated contractions of the supracoracoid muscle will bring about necrotic myopathy.