Your horse’s coat quality and color reflect his or her inner health. Coat color is primarily determined by genetics, although diet and care can also significantly impact coloration.

Melanin is a natural pigment protein that gives color to your horse’s hair and skin. A diet lacking in key nutrients can cause the coat to appear dull and lighter than the shade it would be with optimal nutrition.

Some of the nutrients responsible for producing melanin in the hairs of the coat include zinc, copper, and amino acids. Vitamins A and E, omega-3 fatty acids, and biotin also contribute to coat quality and health.

You can support your horse’s hair coat health and protect it from fading in the sun by providing a balanced feeding program and regular veterinary care. Proper grooming, exercise, and management also support general well-being and help your horse’s coat look its best.

What Determines Coat Color in Horses?

Many different colors of equine coats exist, but horses have three basic coat colors including red (chestnut), bay, and black. [1] All other colors and patterns of equine coats are derived from these base coat colors. [1][2]

The color of your horse’s coat is pre-determined by genetics, but is greatly affected by environmental factors including diet and sun exposure.

Genetics

Several genes interact to influence equine coat color. [3] Key genes responsible for coat color include:

Extension (or E): This gene is responsible for the expression of black pigment in the coat.

Agouti (or A): This gene controls the location of black in the coat.

Dilution: Multiple types of dilution genes exist. These genes reduce the amount of pigment produced in the coat and/or the amount of pigment expressed in the cells of hair follicles.

These genes influence whether one or more pigments are present in the coat and or on the extremities of the body including the mane, tail, lower legs, and ear rims.

Dilution genes are responsible for creating a diverse array of coat colors including cream, champagne, dun, pearl, silver, and mushroom.

Grey (or G): All grey horses have a mutation of the Grey gene (STX17) that is responsible for the slow removal of color from the coat over a period of several years, without altering skin or eye color. A mutation affects the way their bodies produce pigments. [4]

Most white horses carry a dominant mutation of this gene that results in rapid greying with age. This gene does not produce a base color such as red or black. It is also not a dilution gene.

KIT: Mutations in the KIT gene (sabino (Sa1), tobiano (To), roan (Rn), and dominant white (W#)) are responsible for producing predominantly white coats and white spotting patterns in horses. [5]

Melanin Production

Variants of genes (alleles) affect the amount of melanin present in the coat. Melanin is produced in cells called melanocytes.

Two chemically different types of melanin exist including: [6]

  • Pheomelanin: This pigment is red to yellow in color.
  • Eumelanin: This pigment is brown to black in color.

Genes associated with color determination in mammals influence the production and/or distribution of pheomelanin and eumelanin. Coat pigmentation depends on the presence, absence, or proportions of eumelanin and phaeomelanin produced by the melanocytes.

The production of melanin in melanocytes is carried out by proteins that act as biological catalysts (enzymes). A lack of pigment in the skin and hair is caused by the absence of melanocytes.

The color present in each hair of a horse’s coat is produced by melanocytes in the hair follicles. Melanocytes transfer pigment into the hair cells when the hair is actively growing.

If melanocytes are injured due to damage from severe or chronic pressure, a loss of hair color in the affected area may occur and white hair may regrow.

Nutrition and Coat Health

Multiple nutrients influence the growth and health of the coat as well as the pigmentation of the hair. Hair pigment serves as a protective shield for the skin against sunlight.

When UV light oxidizes the pigments in the coat hairs, fading occurs. If there are less than optimal levels of nutrients in the diet to support the production of sufficient pigment, hair will be more prone to bleaching.

Natural coat color cannot be changed without bleaching or dyeing. However, diet can influence the shade and intensity of coat color in horses. [7]

Key nutrients that affect the appearance of the coat include the minerals copper and zinc, as well vitamins B7, A and E.

Copper:

This trace mineral is a component of tyrosinase, one of the key enzymes required for melanin synthesis. Without copper, tyrosinase activity is impaired.

Sufficient dietary copper is needed to produce the melanin responsible for pigmented hairs present in buckskin, chestnuts, black, brown, and grey coats.

When copper level is low in the body, chestnut coats may appear to have a yellow tone and black coats will have a rusted appearance. [14]

Depigmentation and impaired keratinization of the coat hairs can indicate low copper status. Low zinc can also cause these effects.

Zinc:

Horses deficient in the trace mineral zinc may have dull, faded, and frizzy coats. Deficiency is most noticeable in chestnuts, bays, and blacks who require more melanin for their dark coat color.

Zinc is another component of the enzyme tyrosinase, which is is involved in melanin production. Horses with insufficient zinc may not be producing enough melanin to maintain optimal coat health and color.

Zinc is also involved in the production of keratin, the most abundant protein in hair. Keratin is responsible for giving hair its structure.

If your horse’s diet is low in zinc or copper, it is recommended to supplement with organic forms of these trace minerals. Research shows that horses supplemented with organic zinc and copper had stronger and more elastic hair fibres compared to those given inorganic forms of these minerals. [8]

Zinc and Copper Ratio

The balance between zinc and copper must be considered when formulating a diet for your horse. Too much zinc in the diet has been shown to interfere with copper uptake.

Zinc and copper should be present in the diet in a 3:1 ratio to support a shiny, healthy coat.

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Even when adequate levels of copper and zinc are present in the diet, antagonist minerals such as iron can cause secondary deficiencies. A secondary copper deficiency can also be caused by high levels of sulfur in the diet.

Biotin:

An important B-vitamin for hair growth and structural integrity, biotin helps to support the production of keratin in the hair and skin.

Although severe biotin deficiency is not found to occur in horses, insufficient intake of this vitamin can contribute to poor coat quality and cause depigmentation and alopecia. [9][10]

Microbes within the horse’s hindgut synthesize biotin. Horses with hindgut dysfunction may benefit from biotin supplementation to support a healthy, shiny coat.

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Vitamins E and A:

Vitamins E and A support skin and coat health in horses. A dry or brittle coat may occur due to a deficiency in either of these vitamins.

Omega-3 Fatty Acids

Horses deficient in omega-3 fatty acids often have poor hair quality and skin health. Horses cannot synthesize these essential fatty acids so they must come from the diet.

Studies in humans and canines show that diets deficient in omega-3 fatty acids increase the risk of hair loss, structural abnormalities and pigmentation changes in the hair. [11][12] It is possible that a similar effect occurs in horses.

In research on horses, increasing the ratio of dietary omega-3 to omega-6 fatty acids resulted in improved coat scores. [13]

Horses that have higher levels of omega-3 fatty acids in their blood have smoother, shinier, and healthier-looking hair coats. Omega-3s enhance the function of the skin barrier by promoting moisture retention and protecting against irritants that could compromise coat and skin condition.

Amino Acids

The hair in a horse’s coat is predominantly comprised of keratin, a protein made up of amino acids. Suboptimal protein or amino acid levels in the diet can compromise coat color and quality.

The following amino acids contribute to a healthy coat.

  • Phenylalanine and tyrosine aid in the synthesis of eumelanin which is responsible for dark hair pigment.
  • Methionine and cysteine sulfur-containing amino acids are needed to produce keratin which gives hair a strong structure.

A well-balanced vitamin and mineral supplement should supply all nutrients required to support healthy coat growth and color. Mad Barn’s Omneity is a comprehensive vitamin and mineral that contains these ingredients and more in an optimal formulation for coat quality and overall health.

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Tips to Improve Coat Quality

There are lots of ways that you can help your horse grow and maintain a healthy coat. Consider the following strategies to support coat quality and prevent fading:

1) Provide Essential Nutrients: Ensure your horse is receiving all the nutrients required to stay healthy. Feed aforage-based diet and provide a balanced vitamin and mineral supplement such as Mad Barn’s Omneity or AminoTrace+.

Provide a source of essential fatty acids in the diet such as Mad Barn’s w-3 Oil. Your horse cannot produce these fatty acids in his body and must receive them through the diet.

2) Work with an Equine Nutritionist: Ensure your horse’s diet is nutritionally balanced by seeking advice from a qualified equine nutritionist.

3) Groom Your Horse Regularly: Grooming your horse daily is essential to encourage healthy skin and coat growth. Check your horse’s skin and hair daily for signs of irritation. Remove any dirt, mud, or grit from your horse’s coat to minimize skin irritation.

4) Exercise Your Horse: Exercise is beneficial for coat health because it promotes blood flow which facilitates the delivery of oxygen and nutrients to the skin.

Exercise stimulates the flow of sebum (natural secretions of the sebaceous glands) from the hair follicles. Sebum forms a protective layer over the skin that guards against moisture loss and drying and helps to give hair its shine. [15]

5) Control Parasites: A dull, dry coat can be caused by a high parasite load in your horse’s body. Consult with your veterinarian regarding a regular worming program.

6) Treat Skin Infections: Shedding that results in matting or clumping of parts of the hair coat can indicate an infection. The bacterium known as Dermatophilus congolensis is a common cause of skin conditions in horses that causes hair loss and requires treatment to restore coat health. [16]

7) Use UV Protectants on Your Horse’s Coat: Protect your horse’s coat, mane, and tail against sun bleaching by using an external UV protectant on it. Spraying a UV protectant on your horse’s hair every few days may help to reduce sun-bleaching.

8) Blanket Your Horse with a UV Sheet: Covering your horse with a sheet/neck cover made of fabric that offers UV protection may help to reduce coat fading.

9) Limit Sun Exposure: To prevent sun-bleaching of your horse’s coat, consider stabling your horse during the hours of the day when the sunlight is most intense and provide turn out in the evening or overnight.

10) Keep Your Horse’s Coat Free of Sweat: Rinse your horse’s coat with water after exercise to prevent it from bleaching due to sweat.

Horses that are stalled during the day will likely sweat during warm weather which can cause coat bleaching if they are turned out afterward and exposed to the sun’s rays. Using a fan can help to keep your horse cool.

11) Avoid Overbathing: Don’t use harsh detergents on your horse’s coat. These products strip the natural oils from the coat causing it to become dull and dry.

Rinse shampoo and leftover soap from the coat to prevent the skin and coat from over-drying. Rinsing your horse’s coat with water is preferable to using shampoo to preserve coat health.

12) Provide Regular Veterinary Care: Regular veterinary care is important to ensure your horse is in good overall health. The appearance of your horse’s coat reflects his overall health status.

Growing a Healthy Coat: When to Expect Results

If you alter your horse’s feeding program to support coat quality, it can take several months before those changes are reflected in your horse’s hair coat.

Equine coats go through two growth cycles each year, in the summer and winter seasons. The months preceding a seasonal coat change are ideal to influence the incoming hair.

Annual differences in coat appearance will also occur depending on your horse’s diet, ability to absorb nutrients, age, activity level, and environmental influences such as weather.

Reasons for Poor Coat Quality

Any time your horse’s coat significantly changes, consult with your veterinarian. Coat health can be influenced by many health issues including:

Dental Problems: Your horse’s teeth should be checked and floated every six to 12 months by a veterinarian or qualified equine dentist to ensure they are able to chew and digest their food properly.

Metabolic Disease: Horses that have excessively long, and slow-to-shed coats may have a metabolic disease called Pituitary Pars Intermedia Dysfunction (PPID). If you suspect your horse has PPID, contact your veterinarian regarding blood testing to assess your horse for the disease.

Ulcers: If your horse is underweight and has a poor coat appearance, consult your veterinarian. Your veterinarian may recommend a gastroscopy to determine if your horse is suffering from ulcers which can reduce the uptake of nutrients from the diet.

Parasites: Consider performing fecal testing to determine your horse’s parasite load. Follow de-worming recommendations provided by your veterinarian.

For help with formulating the optimal diet to support your horse’s coat color and quality, submit your horse’s information online. Our nutritionists will look over your current feeding program and suggest ways to balance it for free.

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References

  1. Equine Coat Color Genetics. UC Davis Veterinary Medicine. Retrieved June 2022.
  2. Reissmann, M. et al. Distribution of coat-color-associated alleles in the domestic horse population and Przewalski’s horse. J Appl Genet. 2016.
  3. Ludwig A. et al. Coat color variation at the beginning of horse domestication. 2009.
  4. MacKay, RJ. Treatment Options for Melanoma of Gray Horses. Vet Clin North Am Equine Pract. 2019.
  5. Bai, DY. Et al. Effects of Kit gene on coat depigmentation in white horses. Yi Chuan. 2011.
  6. Rzepka, Z et al. From tyrosine to melanin: Signaling pathways and factors regulating melanogenesis. Postepy Hig Med Dosw. 2016.
  7. Asano, K. et al. Influence of the coat color on the trace elemental status measured by particle-induced X-ray emission in horse hair. Biol Trace Elem Res. 2005.
  8. Malgorzata, Kania et al. Effect of diet on mechanical properties of horse’s hair. Acta Bioeng Biomech. 2009.
  9. Whitehead, CC. Assessment of biotin deficiency in animals. Ann N Y Acad Sci. 1985.
  10. Fritsche, A. et al. Pharmakologische Wirkungen von Biotin auf Epidermiszellen [Pharmacologic effects of biotin on epidermal cells]. Schweiz Arch Tierheilkd. 1991.
  11. Finner, A. M. Nutrition and Hair: Deficiencies and Supplements. Dermatologic Clinic. 2013.
  12. Combarros, D. et al. A Prospective, Randomized, Double blind, Placebo-Controlled Evaluation of the Effects of an N-3 Essential Fatty Acids Supplement (Agepi® ?3) on Clinical Signs, and Fatty Acid Concentrations in the Erythrocyte Membrane, Hair Shafts and Skin Surface of Dogs with Poor Quality Coats. Prostaglandins, Leukotrienes & Essential Fatty Acids. 2020.
  13. Goh, YM. et al. Plasma n-3 and n-6 fatty acid profiles and their correlations to hair coat scores in horses kept under Malaysian conditions. J Vet Malaysia. 2004.
  14. McLean, L.M. and Jones, W.E. Depigmentation — copper supplement therapy a case report. J Equine Vet Sci. 1983.
  15. Khmaladze, I. et al. The Skin Interactome: A Holistic “Genome-Microbiome-Exposome” Approach to Understand and Modulate Skin Health and Aging. Clin Cosmet Investig Dermatol. 2020.
  16. Aufox, E.E. et al. The prevalence of Dermatophilus congolensis in horses with pastern dermatitis using PCR to diagnose infection in a population of horses in southern USA. Vet Dermatol. 2018.