Effect of Different Sources of Vitamin D on the Laying Bird

Abstract

THE presence of vitamin D in egg yolk was first demonstrated by Mellanby (1921), who cured rickets in a dog by the addition of egg yolk. Hess (1923) pointed out that egg yolk was one of the few natural foods which possessed definite prophylactic and curative properties against rickets. Casparis, Shipley, and Kramer (1923) also found egg yolk effective in curing rickets in infants. Several investigators have shown that the antirachitic potency of egg yolk is influenced by the vitamin D intake of the laying hen and the exposure of the birds to ultra-violet light. Hart and co-workers (1925) reported that the antirachitic potency of egg yolk from hens exposed for 10 minutes daily to the radiations of a quartz lamp was approximately 10 times that of egg yolk from non-irradiated birds on the same ration. Hughes et al (1925) fed egg yolk of known sources to young chicks and . . .