Selenium-responsive Myopathies of Myocardium and of Smooth Muscle in the Young Poult

Poor growth, mortality and myopathies of the heart and gizzard have been produced experimentally in young poults fed a practical-type diet containing all nutrients previously shown to be required by the poult except for supplemental vitamin E and methionine. The corn and soybean meal used in this diet were obtained from geographical areas where the soil is known to be low in selenium. Addition of vitamin E and methionine to the diet improved growth but gizzard myopathy was not prevented and maximal growth was not achieved until the diet also was supplemented with at least 0.1 ppm of selenium as sodium selenite. Under the conditions of these experiments, therefore, the selenium requirement in a practical-type diet depended to some extent upon the amount of vitamin E or methionine supplementation; it ranged from approximately 0.18 ppm in the presence of vitamin E to approximately 0.28 ppm of selenium in the absence of added vitamin E. Although myopathy of the skeletal (pectoral) muscle was not observed grossly, necropsy studies revealed histological changes in skeletal muscle typical of Zenker's degeneration. The order of prominence of the “selenium-responsive” diseases of the young poult appear to be: myopathy, first of the smooth muscle (gizzard); second, of the myocardium; and third, of the skeletal muscle. Selenium appears to be the primary nutritional factor required. Vitamin E is of less importance and sulfur amino acids are completely ineffective in prevention of these myopathies in poults.