Relation of the Antirachitic Factor to Reproduction in Birds.

Abstract

Some years ago it was shown that hen's eggs are especially rich in the antirachitic factor, an observation which has been confirmed repeatedly. We have since found that the eggs of other animals, for example those of various fish and of serpents, likewise contain a large amount of this specific factor, the concentration varying considerably. In the hen the concentration is greater in the egg than in the liver. Several investigators 1 have shown that the content of the antirachitic factor in hen's eggs varies according to their diet and the degree of exposure to ultra-violet rays, and furthermore than when this factor is notably deficient a marked lack of hatchability results. This failure to hatch has been attributed to defective absorption of calcium from the shell into the yolk.

From last summer until this spring one group of hens has been placed on a diet devoid of the antirachitic factor (a grain mixture, including yellow corn, also meat scrap and 1 part of sodium chloride) but otherwise complete, whereas another group has been given daily supplements of cod liver oil. Our experience may be summarized by the statement that the group on the deficient diet laid comparatively few eggs even during the productive period of March and April, that these eggs contained very little of the antirachitic factor, that fertile eggs failed to hatch, and that the livers of these hens were also lacking in this substance. It should be added, however, that the blood serum of both groups of hens was found to contain a high percentage of calcium in the spring, that is during the productive season, in spite of the fact that one of the groups was laying and hatching normally, whereas the other was almost inactive in this respect.