Effects of selected wavelengths of light on reproductive development in cockerels

This study examined the effects of light from different portions of the spectrum on reproductive development in Leghorn cockerels. Chicks were distributed among six identical chambers. One was illuminated with broad spectrum white light; the other five were equipped with filter systems designed to provide approximately 100-nm bandwidths of light of similar intensity. All treatment groups were synchronized to a 14L:10D photoperiod. Plasma concentrations of LH and testosterone were measured by radioimmunoassay in 15- and 18-week-old cockerels. Body weights and testes weights were obtained from 18-week-old birds. Statistically significant (P less than 0.05) differences in plasma LH concentrations due to lighting could not be detected at either age. However, at 15 weeks, circulating testosterone levels were significantly higher in the groups exposed to red or white light. Three weeks later, testosterone was also elevated in cockerels grown under green light, while testes weights were heavier only in birds kept under white or red.