THE FAT-SOLUBLE VITAMIN CONTENT OF HEN'S EGG YOLK AS AFFECTED BY THE RATION AND MANAGEMENT OF THE LAYERS

Abstract

The value of a food product as a source of vitamins in the human dietary is largely determined by other inherent factors.Of two or more substances having a similar vitamin content the one which is the most available at a reasonable price to the greatest number of people, and at the same time is a product which is palatable, easily digestible, and possesses other food values, is the one which will finally prove the more important.In respect to these considerations hen's eggs probably take first place when compared with other natural food products as a source of vitamins A and D.That egg yolk is a rich source of vitamin A was pointed out by McCollum and Davis (1) and by Osborne and Mendel (2) in their early work on this vitamin.More recently Murphy and Jones (3) working on the vitamin A content of fresh eggs found that about 0.25 gm. of whole egg was required daily to cure rats of xerophthalmia, and 0.5 to 0.75 gm.daily to restore normal weight.Working with the yolk of fresh eggs, Hess (4) found that 0.25 gm.daily proved sufficient to protect rats from rickets.Similar results were obtained by Casparis, Shipley, and Kramer (5).Work at the Ohio station (6) also demonstrated that egg yolk possessed distinct antirachitic properties in preventing leg weakness in young growing chicks.Hart, Steenbock, and coworkers (7) in studying the effect of ultra-violet light on production, hatchability, and fertility of the egg, found that egg yolk from irradiated