Optimised Stable Lighting Strengthens Circadian Clock Gene Rhythmicity in Equine Hair Follicles.
Authors: Collery Aileen, Browne John A, O'Brien Christiane, Sheridan John T, Murphy Barbara A
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Hair follicles offer a non-invasive window into equine circadian function, making them valuable for assessing how stable management affects the molecular clock—a concern given that irregular light exposure disrupts circadian rhythmicity and compromises welfare in stabled horses. Researchers compared standard incandescent lighting against a customized LED system (blue-enriched white light during the day, dim red at night) in five Thoroughbreds per group, sampling mane hair every 4 hours over 24-hour periods at baseline and 20 weeks, then quantifying expression of six core circadian genes using qPCR. The LED-treated group demonstrated significant 24-hour rhythmicity in two critical clock genes—*NR1D2* and *PER2*—by week 20, with *CRY1* approaching significance, whereas control horses showed no detectable gene rhythmicity at either timepoint. These findings suggest that current stable lighting practices fail to support robust circadian entrainment, and that timed, spectrum-optimised LED systems can meaningfully strengthen circadian clock function over a season. For equine professionals managing stabled horses, this work indicates that deliberate investment in lighting design—particularly blue-spectrum exposure during daylight and suppression of light at night—represents a practical, evidence-based welfare intervention with measurable molecular consequences.
Read the full abstract on PubMed
Practical Takeaways
- •Consider upgrading stable lighting systems to blue-enriched LED during day and red/dim light at night to support horses' natural circadian rhythms and improve welfare
- •Irregular or continuous incandescent lighting fails to entrain circadian clock genes in stabled horses; this may contribute to stress and health issues in racing operations
- •Hair samples provide a non-invasive method to assess whether your stable's lighting regime is effectively supporting circadian function
Key Findings
- •LED lighting with blue-enriched white light by day and dim red light at night induced 24-hour rhythmicity in NR1D2 and PER2 clock genes in horse hair follicles by week 20
- •Standard incandescent lighting produced no detectable circadian gene rhythmicity in control horses at either week 0 or week 20
- •CRY1 gene expression approached significant 24-hour rhythmicity in the treatment group (p = 0.051)
- •Hair follicles successfully demonstrated circadian clock gene expression patterns in response to optimized lighting conditions