Supplementary dim light differentially influences sexual maturity, oviposition time, and melatonin rhythms in pullets.
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.
Lewis
P D
PD
Department of Clinical Veterinary Science, University of Bristol, Langford, United Kingdom. peter@clatford.demon.co.uk
Perry
G C
GC
Morris
T R
TR
English
J
J
D000375:Aging / Q000502:physiology*; D000818:Animals; D000975:Antioxidants / Q000032:analysis; D002645:Chickens / Q000254:growth & development / Q000502:physiology*; D002940:Circadian Rhythm; D005260:Female; D008550:Melatonin / Q000097:blood*; D010058:Oviposition / Q000502:physiology*; D017440:Photoperiod; D011897:Random Allocation; D012741:Sexual Maturation / Q000502:physiology*; D013997:Time Factors
D000975:Antioxidants; D008550:Melatonin