Supplementary dim light differentially influences sexual maturity, oviposition time, and melatonin rhythms in pullets

• Published in: Poultry science 2001-12, Vol.80 (12), p.1723-1728
• Main Authors: Lewis, P D, Perry, G C, Morris, T R, English, J
• Format: Article
• Language: English
• Subjects: Aging - physiology; Animals; Antioxidants - analysis; Chickens - growth & development; Chickens - physiology; Circadian Rhythm; Female; Melatonin - blood; Oviposition - physiology; Photoperiod; Random Allocation; Sexual Maturation - physiology; Time Factors
• ISSN: 0032-5791
• DOI: 10.1093/ps/80.12.1723

The addition of two 3-h periods of very dim light, one before and one after a normal 8-h photoperiod, advances sexual maturity in pullets by about a week. This trial tested the hypothesis that dim light given before a short day of normal intensity is linked to form a more stimulatory day length and that dim light given after it is photosexually ignored. Pullets were reared from 2 d of age on 8-h photoperiods. From 10 wk, they were continued on 8-h photoperiods, transferred to 16 h, or given an 8-h period of dim light (0.09 lx) immediately before or after the main 8-h photoperiod. The bright/dim and dim/ bright groups matured at the same age, thus disproving the hypothesis tested. Both groups matured 1 wk earlier than the 8-h controls but 5 wk later than birds transferred to 16-h photoperiod. Oviposition time was similar for 8-h controls and bright/dim hens and delayed by 3 h for 16-h birds, but phase advanced by 2.4 h for dim/bright hens. Plasma melatonin rhythm was phase-advanced by about 5 h in the dim/bright hens and retarded by about 5 h in the bright/dim hens, suggesting a 13-h subjective day. However, these treatments were not regarded as fully stimulatory, as a transfer to a normal 13-h photoperiod at this age advances maturity by 5 to 6 wk. These findings show that the addition of a period of dim light to a normal nonstimulatory photoperiod differentially affects the clocks that control sexual maturation, plasma melatonin concentration, and oviposition time.