Effect of day length on flock behavioural patterns and melatonin rhythms in broilers.

Area of Science:

• Animal Science
• Avian Physiology
• Animal Behavior

Background:

• Photoperiod management is crucial for poultry production.
• Understanding the impact of light exposure on broiler behavior and physiology is essential for welfare.
• Melatonin rhythm synchrony is a key indicator of healthy circadian function in birds.

Purpose of the Study:

• To investigate the effects of varying durations of light (14, 17, 20, and 23 hours) on broiler chicken behavioral patterns.
• To assess the synchrony of 24-hour melatonin rhythms in broilers under different photoperiods.
• To determine the relationship between photoperiod, behavior, and melatonin production in broiler chickens.

Main Methods:

• Ross × Ross 308 male broilers were subjected to four lighting treatments (14, 17, 20, 23 hours of light).
• Behavioral patterns (resting, standing, walking, feeding) were digitally recorded and quantified using scan sampling.
• Melatonin levels were measured using radioimmunoassay at multiple time points over a 24-hour period.

Main Results:

• Broilers exposed to 14 and 17 hours of light showed frequent linear and quadratic relationships between time and behavior during the photophase.
• A quadratic relationship between time and melatonin was observed in flocks exposed to 14, 17, and 20 hours of light.
• Broiler flocks exposed to 23 hours of light did not develop synchronized melatonin rhythms.

Conclusions:

• Continuous light exposure (23L) in broiler chickens prevents the synchronization of melatonin rhythms.
• Disrupted circadian rhythms due to excessive light exposure may lead to sleep fragmentation and compromised welfare in broilers.
• Photoperiod management significantly influences broiler behavior and physiological rhythms, highlighting the need for optimized lighting strategies.