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Plasma corticosterone in chicks reared under several lighting schedules
Insights
Chicks reared in darkness showed lower plasma corticosterone levels than diurnal or continuous light groups. A diurnal rhythm of corticosterone was observed, persisting even in constant light conditions.
Area of Science:
- Animal Physiology
- Endocrinology
- Chronobiology
Background:
- The regulation of plasma corticosterone levels is crucial for broiler chick health and development.
- Lighting regimes are known to influence physiological processes in poultry.
- Understanding the interplay between light, circadian rhythms, and stress hormones is essential for optimizing poultry welfare.
Purpose of the Study:
- To investigate the impact of different lighting regimes on plasma corticosterone levels in broiler chicks.
- To determine the presence and characteristics of a diurnal corticosterone rhythm under various light conditions.
- To assess the influence of light intensity and sampling time on corticosterone levels.
Main Methods:
- Plasma corticosterone was measured using radioimmunoassay in male broiler chicks (6-7 weeks old).
- Chicks were reared under controlled lighting regimes, including darkness, diurnal light, and continuous light.
- Around-the-clock blood sampling was performed to analyze diurnal rhythms.
Main Results:
- Chicks reared in darkness exhibited significantly lower plasma corticosterone than diurnal or continuous light groups.
- A clear diurnal rhythm of corticosterone was observed, with higher levels during the day and lower levels at night.
- This diurnal rhythm persisted in constant light, though it appeared phase-shifted or free-running.
Conclusions:
- Photoperiod significantly influences plasma corticosterone levels in broiler chicks, with darkness leading to suppression.
- Broiler chicks possess an endogenous diurnal corticosterone rhythm that is robust and can persist under constant light.
- Light intensity and the specific light status (on/off) at the time of sampling did not significantly affect corticosterone levels in this study.
Abstract:
Plasma corticosterone was determined by radioimmunoassay in 6-7-week-old male broiler type chicks, reared under several carefully controlled lighting regimes. When subjects were grouped by photoperiod of rearing, chicks reared in darkness had significantly lower hormone levels than diurnal controls, or than subjects reared in continuous light. Around-the-clock sampling revealed a diurnal corticosterone rhythm, with high daytime levels and lower night-time levels. This rhythm appeared to be retained in constant light, although phase shifted or free running. Neither analysis by light intensity level nor by lights on/lights off status at the time of blood sampling revealed differences in plasma corticosterone between the experimental groups which could be attributed to these factors.
