During the last few years considerable interest has been shown in the production of broiler chicks to the age of 10 to 12 weeks. During the late winter and early spring months, difficulties, such as leg weakness have been frequently encountered and remedies, such as cod liver oil, egg yolks, quartz mercury vapor lamp, glass substitutes or direct sunlight have been advocated to provide the antirachitic vitamin, which is necessary to insure success and obtain maximum growth.
Variability in potency, supply and cost of cod liver oil and egg yolks have been limiting factors in their use by the practical poultrymen in rearing chicks during late winter and early spring.
Cochran, R. L. and Bittenbender, H. A.
"Value of some of the glass substitutes in growing chicks,"
Bulletin (Iowa Agricultural Experiment Station): Vol. 21
, Article 1.
Available at: http://lib.dr.iastate.edu/bulletin/vol21/iss246/1