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The Relationship of the Vitamin D Intake of the Hen to the Antirachitic Potency of the Eggs Produced^1,2

One Figure

Departments of Agricultural and Biological Chemistry and Poultry Husbandry, Pennsylvania State College

A study has been made of the effect of the vitamin D intake of the hen on the antirachitic potency of the eggs produced. As a result of this investigation, the following conclusions are drawn:

1. The antirachitic potency of egg yolk depends on the antirachitic intake of the hen producing it.

2. The ability of the hen to transfer the antirachitic factor or factors from her diet to the egg appears to be limited.

3. When the hen's diet is supplemented with one-fourth per cent of fortified (8D) cod liver oil (which Murphy, Hunter, and Knandel ('34) found to be the optimum level when the birds were confined and denied access to direct sunlight), 1 gm. of the yolk from the eggs produced contained approximately 0.5 Steenbock unit. On this basis, an egg yolk weighing 15 gm. would contain 7.5 Steenbock units of vitamin D.

4. Yearling hens, nearing the end of a period of egg production, produced egg yolks that were more potent (antirachitically) than did pullets at the beginning of their initial period of egg production. It is suggested that this difference in potency might be due to the rate of egg production and not to the period of production.

5. At the particular level studied, the antirachitic potency of cod liver oil appeared to be more efficiently transferred from the diet to the egg yolk than was an equal unitage of viosterol.

² Publication authorized by the director of the Pennsylvania Agricultural Experiment Station April 16, 1935, as technical paper no. 686.

Manuscript received 22 April 1935.