Physiological Development of Cockerels as Influenced by Selected Wavelengths of Environmental Light

The effects of narrow-band light at equal energy levels on the development of cockerels were investigated. A total of 216 chicks were raised in conventional electrically heated starting batteries until 6 weeks of age. They were then allotted to environmental chambers and exposed to one of the following light treatments for 35 days: blue (450 nm.), green (545 nm.), red (650 nm.), far-red (750 nm.), dark or white. Feed and water were supplied ad libitum. Chick growth was significantly (P < .05) stimulated by a green light environment (peak 545 nm.) when compared to any other light environment. This was not accompanied by an increase in feed consumption. Chicks grew about as well in complete darkness as under white lights. The wavelength of light environment affected the reproductive development of the chick. Larger pituitary glands, containing significantly (P < .01) more gonadotropin hormone, were obtained from birds receiving the red (peak 650 nm.) or white light treatments, compared to the other light treatments. Testes weight and comb weights followed a similar pattern, indicating release as well as production of pituitary gonadotropin hormones. The pituitary glands from chicks grown under far-red (peak 750 nm.) environment contained the least gonadotropin. This difference was significant (P < .05) for all values except that obtained for the dark environment.