Influence of lighting on sleep behaviour, circadian rhythm and spontaneous blink rate in stabled riding school horses (Equus caballus).

The study investigates how different types of lighting, particularly light-emitting diode (LED) and fluorescent fixtures, affect sleep behaviors, daily rhythm, and spontaneous blink rates in stabled horses. The results showed no significant change in sleep patterns or circadian rhythmicity and suggest that LED lighting could perhaps promote daytime wakefulness in horses.

Objective and Methodology of the Study

• The research aimed to examine the impact of two different types of lighting, a customised LED lighting system and a standard fluorescent lighting fixture on sleep behaviours, the internal body clock, and spontaneous blink rates in horses. This consideration is important as modern horse care practices often involve substantial time spent indoors where lighting conditions can be subpar, and horses are frequently disturbed in the night by human activity.
• Ten horses used in a riding school were exposed to two varying stable lighting conditions for four weeks each from January to March 2023. The treatment lighting was an LED system that emitted timed blue-enriched white polychromatic light by day and dim red light at night. In contrast, the control lighting was manually switched on and off each morning and evening with the standard fluorescent tube.
• The behavior of the horses, including their blink rate, was monitored continuously during the fourth week of the experimental period. Hair samples were also collected from each horse at four-hour intervals for 52 hours to allow for the analysis of circadian clock genes.

Findings of the Study

• The study found no notable differences in total sleep, different types of recumbency, wakefulness, standing, standing sleep, or spontaneous blink rate between the two different lighting conditions.
• However, the lighting period (Day versus Night) did have a significant effect on total sleep, total recumbency, wakefulness, and standing sleep in both conditions. In the LED lighting condition, more wakefulness was observed during the day.
• While time affected the activity of the clock genes PER2 and DBP, the study found no interaction between time and treatment, suggesting that the type of lighting had no significant impact on the time-dependent activity of these circadian genes.
• For both lighting conditions, a consistent 24-hour pattern was found for the circadian genes PER2 and DBP, suggesting that the lighting used did not interfere with the normal circadian rhythms of the horses.

Implications of the Results

• These results seem to suggest that using dim red light at night does not have a negative impact on normal sleep patterns or the horses’ internal body clocks.
• Interestingly, the study notes that during the day, stabled horses under LED lighting were more awake. This could potentially suggest a role for blue-enriched LED light in promoting increased wakefulness during the daytime.
• The researchers recommend further research into this area is needed to better understand the role and possible benefits of LED lighting for horse husbandry.