THE INFLUENCE OF VITAMIN D DEFICIENCY ON GASEOUS EXCHANGE IN CHICKS

Abstract

The respiratory quotient (Haldane method) of the normally growing small chick between 75 and 500 gm is between 0.94 and 1.00. This furnishes evidence that the chick consistently utilizes carbohydrates while upon an adequate diet. Deprived of an adequate supply of vitamin D, the chick continues the utilization of carbohydrates for a time, as evidenced by the persistence of the respiratory quotient near unity. After 15-18 days upon a diet lacking in vitamin D, the characteristic symptoms of rachitis appear. Prior to their appearance a pronounced fall in the level of the respiratory quotient is noted. This would seem to indicate a rapid loss in ability to utilize carbohydrates as a chief source of fuel. During exhibition of leg weakness the respiratory quotient is indicative of the utilization of fats alone although carbohydrates compose as high as 47% of the diet. The temperature of the chick falls slightly and remains low throughout manifestation of rachitis with only slight loss of appetite. Restoration of the antirachitic substance, either by the inclusion of cod liver oil in the diet or by irradiation, brings the respiratory quotient to unity. It is evident that the presence of the antirachitie factor is requisite to normal carbohydrate metabolism in the chick.