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A study of free-running rhythms in sheep
International Journal of Chronobiology
|January 1, 1979
Summary
In rams, daily rhythms for eating and activity initially free-ran briefly under dim light but quickly became random. Entrained rhythms were lost by day four, indicating a loss of biological clock regulation.
Area of Science:
- Animal behavior
- Chronobiology
- Physiology
Background:
- Circadian rhythms govern daily biological activities.
- Light-dark cycles are primary synchronizers of these rhythms.
- Understanding rhythm entrainment and free-running is crucial for animal welfare.
Purpose of the Study:
- To investigate the free-running activity rhythms in cross-bred rams.
- To determine the effect of continuous dim light on previously entrained rhythms.
- To assess the impact of different entraining agents on activity patterns.
Main Methods:
- Two experiments were conducted on four cross-bred rams.
- Activity rhythms were initially entrained using a light-dark (LD) cycle (12:12) (300:0).
- Rhythms were then exposed to continuous dim light (<2 lux) or combined entrainment methods.
Main Results:
- A transient suggestion of free-running activity was observed for approximately three days.
- By the fourth day of continuous dim light, activity patterns became random.
- Both LD cycles and feed restriction as entraining agents showed similar results.
Conclusions:
- Entrained rhythms in rams are rapidly lost under continuous dim light.
- Biological rhythms were not sustained in free-running conditions beyond a few days.
- The study highlights the sensitivity of ram activity rhythms to light cues.