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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 (SB1), 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.
