The Influence of Vitamin D on Hatch- ability and Egg Production

POULTRYMEN have known for some years that the hatchability of eggs pro-duced during the winter months—the in-cubation season—tended to be low, espe-cially if the birds were confined indoors. A marked improvement occurred in the spring when the birds were allowed outdoors in the sunshine. Since this improvement paralleled fairly closely the increase in amount of ul-tra-violet light in sunlight, many workers soon established a relationship between hatchability and the antirachitic vitamin. In general, the sources of vitamin D have been cod liver oil. Recently investigators have used ultra-violet irradiation from ar-tificial sources either directly or indirectl