Abstract
In early November, 1927, a small colony of hens and cockerels from a flock of white leghorns of uniformly good grade of stock which had summered out of doors were divided into 3 groups of 6 hens and one cockerel each. They were placed in an experimental house, each compartment of which was provided with transparent windows of about 10 square feet, with southern exposure to light. One compartment was provided with cathedral or hammered vitaglass, while the other 2 were fitted with cathedral ordinary window glass. The diet fed throughout the experiment was the standard Wisconsin all-mash ration, consisting of 80 pounds yellow corn meal, 20 pounds shorts, 5 pounds bone meal, 5 pounds limestone grit and 1 pound salt. Group 1 was enclosed behind ordinary window glass with 2% by weight of cod liver oil (Squibb's) added to the diet, group 2 behind quartz-containing glass (vitaglass) and group 3 behind ordinary window glass only. The hours of feeding were regular and the quantities of food given were ample but constant. Temperature, amount of sunshine and other elements of the weather changed from day to day but were the same in all compartments. No attempt was made to keep the temperature in the experimental chicken house within a certain range; during 6 months of experimentation the temperature varied from 60° F. to −20° F. In brief, the experimental conditions were similar to those existing on a Minnesota farm; the only variables controlled were the presence or absence of the shorter ultraviolet rays of winter sunlight or cod liver oil in the ration.
Starting in January, 1928, all eggs from each of the 3 groups were gathered, and incubation of the weekly product was made.
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