Evidence on Lights and Coats
- Aug 16
- 4 min read
If you’ve wandered through show barns or breeding facilities in the cooler months, you've likely seen horses glowing under artificial lights. The promise? Sleek summer coats year-round — no clipping, no shaggy fuzz, just gleaming hair ready for the ring.
But does it actually work?
What Science Says
Seasonal coat growth in horses is largely influenced by changes in day length, not temperature. Shorter days trigger a rise in melatonin, which suppresses prolactin, a hormone involved in hair shedding. Artificially extending daylight — typically to 15–16 hours per day — is claimed to suppress melatonin, allowing prolactin to maintain a sleek coat.
And the source of this claim?
One single peer-reviewed study.
In 2020, a study by O'Brien, Darcy-Dunne & Murphy was published in PLOS ONE, which is a journal that covers primary research in science and medicine. It explored whether extended photoperiod via blue light masks could affect coat growth. Their findings were promising: if started early enough (one month post–summer solstice), light exposure helped maintain summer coats in horses and accelerate shedding before winter.
But here’s the kicker — both O’Brien and Murphy are employed by or affiliated with Equilume Ltd., the company that manufactures the very light masks used in the research. Murphy is the founder and shareholder; O’Brien is a research manager.
So while the methodology appears to be sound, the commercial connection means we need to interpret the results with caution.
When looking at research, it's always important to consider who is paying for the study.
Why it Matters
No independent replication: There are no peer-reviewed studies from third-party researchers validating these results.
Breed differences: Ponies showed minimal responsiveness to light manipulation — suggesting breed-specific variability.
Timing and environment: The effectiveness hinges heavily on when light treatment is started and whether horses are rugged or stabled. Miss the window, and results diminish.
Practical vs. Proven: While anecdotal use of lights in barns abounds, the scientific foundation is thin and commercially entangled.
It's also not a free pass to leave the lights on all night.
If you’re considering lighting systems to manage your horse’s coat:
Understand it's a hormonal manipulation, not a magic bullet.
Weigh the cost against the limited independent evidence.
Watch the timing — starting late in the season is unlikely to help, and you are theoretically looking at 16 hours of light, not 24 hours of light.
Consider grooming, nutrition (including amino acid support), and appropriate rugging as equally impactful strategies.
Until research independent of the product manufacturer emerges, treat lighting systems as a tool with potential, not a guaranteed solution.
What actually builds healthy coats?
Grooming is Free
Stimulates Natural Oil Production
Brushing and currying stimulate sebaceous glands, which secrete sebum. Sebum helps the coat lay flat, adds shine, and protects against moisture loss and microbial invasion.
2. Improves Circulation
Vigorous grooming boosts blood flow to the skin and muscles.
Enhanced circulation supports nutrient delivery and waste removal, which helps maintain healthy skin and coat.
3. Prevents Skin Infections
Regular grooming removes sweat, dirt, and debris that can harbor bacteria and fungi. It’s especially effective in preventing conditions like rain rot and scratches.
4. Early Detection of Health Issues
Grooming allows for hands-on inspection, helping spot lumps, heat, or wounds early. This proactive care can prevent minor issues from escalating.
5. Parasite Control
Grooming disrupts the lifecycle of external parasites like ticks and lice. It also helps identify infestations before they become severe.
Bear in mind, mutual grooming is how horses develop bonds with each other, and manage stress. Grooming is a language of affection from you that they instinctively understand, as opposed to giving treats. Horses don't give treats to each other.
Supply your horse with the building blocks to make hair.
Keratin, the structural protein in hair, relies on adequate dietary protein.
Essential amino acids like lysine, methionine, and threonine are critical for hair strength and growth.
Lysine supports collagen and elastin synthesis in skin.
Methionine contributes sulfur for keratin formation.
Threonine aids in protein turnover and skin integrity.
Protein sources: Alfalfa (lucerne) and soybean meal.
Omega-3s (ALA, EPA, DHA) reduce inflammation and improve skin moisture retention.
Flaxseed or chia are excellent sources.
Vitamin A: Supports skin cell turnover and sebum production.
Vitamin E: Antioxidant that protects skin cells and enhances immune response.
Vitamins are generally abundant in fresh pick. Supplementation is only needed for horses on stored hay.
Biotin (B7): Essential for keratin production — strengthens hair and hooves.
Zinc: Vital for skin integrity and immune defense.
Copper: Crucial for melanin production — affects coat colour depth.
Selenium: Works with vitamin E to protect against oxidative stress.
Iodine: Supports thyroid function, which influences coat quality and metabolic health.
Forage Quality
Poor forage = protein and vitamin deficiencies = dull, brittle coats.
Bonus Tips
Hydration: Dehydration leads to dry, flaky skin. You can encourage drinking with salt.
Parasite control: Internal parasites can rob nutrients and dull the coat.
Gut health: A balanced microbiome supports nutrient absorption — VFAs from hindgut fermentation contribute to skin and coat vitality.
Our best combination of supplements for building healthy coats are Biotin Trace Mix, Flaxseed Meal and our Pre/Probiotic Bundle. Not only do these supplements provide the building blocks for healthy skin, hair and hooves, but also support a range of other functions in the body.
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