Hair Coat Conundrums

Beautiful hair is a widely sought-after commodity. Just look at the millions of dollars people spend on various hair treatments. Britney Spears alone reportedly spends more than $60,000 on personal grooming expenses every year! Horses are similarly pampered and preened, as evidenced by the fact that nutritional supplements marketed for skin and coat are the fifth most popular type of equine supplement sold in the United States, accounting for approximately $58 million dollars in sales each year. 

This article focuses on some common aberrations in your horse’s hair coat. Examples include failure to shed, balding, graying, and the itching and crusting that might lie beneath the hairs. We’ll also briefly review beauty basics, what your horse’s hair actually is made of, and what purposes those teeny tresses serve. 

Mary, Mary Quite Contrary—How Does Your Hair Grow?

Considering how difficult hair can be to manage, whether your own tough-to-tame tresses or your horses’ braid-resistant locks, its structure is actually quite simple. Hair grows from follicles in the skin, and each strand has a center (the medulla), a middle layer (the cortex), and an outer layer (the cuticle). Horses have three different kinds of hair: permanent hair of the forelock, mane, tail, eyelashes, and “feathers” (what’s seen in Clydes and some of our other draft horse friends); temporary hair covering most of the body that the horse sheds intermittently/seasonally; and tactile hair on the muzzle and in the ears.

Other than to occupy owners’ time brushing, trimming, shaving, and pulling, horses’ hair actually serves a number of important functions, including:

  • Body temperature regulation and protection against the elements (wind, rain, sun);
  • Insulation of the vessels in the neck that supply blood to the brain;
  • Protection against insects; and
  • Production and transport of pheromones, which are potent chemicals animals produce that can change or impact the behavior of others.

Horses’ bodies produce hair in distinct stages. Hair actively growing—when new hairs formed in the follicles displace “old” or “club” hairs—is in its anagen phase. Hair’s resting phase is termed telogen, and hair in transition from anagen to telogen is in the catagen phase. 

Too Much Hair

Horses with long, shaggy hair coats tend to stick out like sore thumbs from their shiny herdmates in milder months. Cathy McGowan, BVSc, MACVSc, PhD, DEIM, Dip. ECEIM, FHEA, MRCVS, head of Equine Internal Medicine in the University of Liverpool’s Department of Veterinary Clinical Sciences, in the United Kingdom, has studied hair coats in depth and says one of the most common causes for failure to shed or inappropriate shedding is equine Cushing’s disease, also known as pituitary pars intermedia dysfunction (PPID).

In a recent study of 325 Queensland, Australia, horses over the age of 15, she and her colleagues determined that approximately one-fifth of the animals had PPID diagnoses. “Of horses diagnosed with Cushing’s disease, hirsutism, defined as delayed shedding and/or a long hair coat, was one of the most consistent signs of the disease,” relays McGowan. 

She says one interesting study observation was that owners were more likely to pick up on signs of hirsutism than the veterinarians. “This makes sense when you think owners have a … historical perspective of their horse’s shedding patterns,” she says. This tendency “is even more important in horses than in ponies, because ponies show quite marked hypertrichosis (abnormal hair overgrowth), whereas horses can show more subtle signs of abnormal shedding or coat length, like simply longer guard hairs or hairs on the legs or just a few weeks’ delay in shedding noticed over the years.” So if you spot this type of hair growth on your horse, you might want to put a call in to your veterinarian.

In a recent article, Annette D. Petersen, DVM, Dipl. ACVD, et al. from Michigan State University’s College of Veterinary Medicine, in East Lansing, said that more than 80% of Cushing’s horses have a long and curly hair coat that fails to shed. She said changes in hair coat occur steadily over several years and are most obvious as delayed shedding and as growth of long hairs under the jaw, along the jugular grooves and underside of the neck, and the backs of the limbs. 

To better establish exactly why horses with equine Cushing’s disease have coat-related issues, Petersen and colleagues collected skin and hair follicle samples from eight horses with Cushing’s disease and four age-matched nondiseased controls. They analyzed those samples under a microscope and determined that Cushing’s horses’ follicles were almost exclusively in the anagen phase whereas normal horses’ follicles were primarily in the telogen phase. In addition, they found that after treating affected horses with pergolide for six months, shedding improved and the number of hair follicles in the anagen and telogen phases was similar to that of the control horses.

The persistence of hair follicles in the anagen phase appears to explain why Cushing’s horses almost always have long and curly hair coats; however, the study authors concluded, “Further investigation is needed to elucidate the mechanism(s) underlying development of hypertrichosis in PPID-affected horses.”

Breed-Specific Coats

For some horses, unusual hair coats are in their genes. Certain breeds are characterized by the length, color, and texture of their hair. A few examples include:

Bashkir Curly Horses As the name implies, these horses carry a gene that produces a uniquely curly coat, mane, and tail—even inner-ear fur. The trait can be expressed minimally (in some horses, called smooth coat curlies, it isn’t expressed at all) or to the extreme, as pictured on the cover.

Gypsy Horses These black and white draft-type horses have leg feathering typical of most draft breeds, falling from the knees downward. They might also sport a mustache along their lips and abundant jaw hair, commonly referred to as a beard.

Akhal-Teke This breed from Turkmenistan and Russia carries a gene for the cream dilution hair coat. They are known for their distinctive metallic sheen—particularly in palomino and buckskin-colored individuals.

Norwegian Fjord This sturdy little breed sports primitive markings, including a dorsal stripe that runs the full length of the body and faint striping on the legs. When roached, the flaxen hairs on the edges of their manes contrast with the dark center stripe to give fjords a rare and dramatic two-toned hairdo.

Alexandra Beckstett

Too Little Hair

There are almost as many reasons for hair loss as there are hairs on your horse’s head alone. Some of the most common are bacterial or fungal infections. Classic examples include rain rot caused by the bacterium Dermatophilus congolensis and ringworm from various fungi such as Trichophyton equinum, T. mentagrophytes (most commonly), as well as Microsporum gypseum, M. canis, and T. verrucosum. Malassezia yeast infections can cause hair loss, a condition called Malassezia dermatitis. And various uncommon disease conditions, such as equine alopecia areata (AA), can lead to bald spots.

“Alopecia areata is a disease that causes hair loss due to inflammatory changes within and surrounding the hair bulb and deeper portions of the hair follicle without subsequent scarring,” explains Danielle E. Hoolahan, DVM, of the William R. Pritchard Veterinary Medical Teaching Hospital at the University of California, Davis, in her April 2013 Veterinary Dermatology article.  

From 1980 to 2011, Hoolahan and colleagues identified only 15 horses with alopecia areata—a disease prevalence of only 0.017%. Important discoveries about this disease included the following:

  • There was no statistically significant breed or sex predilection, but affected horses were more likely to be Appaloosas and Quarter Horses; 
  • Mean age of affected horses was nine years;
  • Hair loss was more likely to occur in the mane and tail and on the face; and 
  • Hair loss was more pronounced in the spring and summer.

The researchers noted spontaneous improvement is possible; however, they said AA typically has a waxing and waning course and that, although unsightly, it appears to be only a cosmetic concern based on the available information.

Dull Hair, and the Crusty, Itchy Skin Beneath 

Worms such as roundworms or large and small strongyles can cause dull hair coats in young horses. Additional reasons for anything less than a glossy gleam are plentiful, but they can include the following:

Pemphigus foliaceus This is a disease in which the body’s immune system attacks the bonds that keep the skin cells together. When the cells separate, pustules (blisters) form. As such, affected horses experience oozing, crusting, and scaling, as well as hair loss and even depigmentation. 

Allergies/hives Also referred to as “urticaria,” hives appear as elevated, round, or flat-topped wheals or plaques measuring approximately 0.5-8 in. (1-20 cm) in diameter. Such hives can appear anywhere on the body, but they primarily occur on the back, flanks, neck, eyelids, and legs within minutes to hours of exposure to the inciting cause, be it a drug or other environmental contaminant.

Onchocerciasis This condition is caused by roundworms located in the skin (as opposed to the gastrointestinal tract, where other roundworms reside). Infected horses can develop fistulous withers, poll evil, uveitis (inflammation in the eye), and dermatitis of the face, neck, chest, withers, forelegs, and abdomen. Lesions might be itchy, and the skin often develops scales, crusts, and ulcers, sometimes resulting in hair loss and changes in hair color. 

As we’ve suggested, insect bites, environmental allergens, or even chemicals (including shampoos and topical medications) can all negatively impact the skin and hair coat’s appearance. Sometimes it can be challenging to visually distinguish various skin conditions from one another, despite how different the underlying causes are. 

Fading and Graying

Multiple breeds and horses of particular genetic makeups have hair coats that gray or fade at various points during their lives, though we won’t go into detail regarding the complex genetics of coloring here (learn more at Changes or loss in coat color can also occur with age, following certain infections (as with pemphigus foliaceus), or after injury and scarring. 

Pulled hair samples contain enough DNA for most experimental methods we might need to perform in research

Dr. Samantha Brooks

Additional Uses for Hair

Sure, we’ve seen horsehair paint brushes, along with pottery, bracelets, and other mementos. But did you know that scientists can use horse hair as a cell source for cloning horses? Hair can also be used to assess a horse’s nutritional status and even drug history. You or your veterinarian can collect a hair sample from your horse and send it to a commercial laboratory to yield information regarding the levels of certain elements, such as selenium or heavy metals that can affect the animal’s health, particularly if toxic levels exist in the body. Drugs such as stimulants, steroids, and sedatives can also be detected. 

Finally, owners can store and use hair for future genetic analysis, as previously reported by Samantha Brooks, PhD, an associate professor at Cornell University’s College of Agriculture and Life Sciences and Director of the Brooks Equine Genetics Lab.

“Modern genomic techniques can utilize very small samples of DNA for complex levels of analysis,” she says. “Pulled hair samples (a swatch about the thickness of a pencil), just like those used for most parentage testing, contain enough DNA for most experimental methods we might need to perform in research. Plus, hair samples are easy to ship and store.”

Having stored DNA means it would be possible for horse owners and breed organizations to collect their own “DNA banks.”

“Samples gathered now, kept neatly, and with relevant horse identification and information on health or performance could be used to conduct expansive studies in the future,” Brooks adds. “In fact, many of our current projects aren’t limited by the available technology, but by the number of samples we are able to recruit on short notice.”

Take-Home Message

There is a wide and varied range of reasons that a horse’s hair coat can puzzle even the most experienced horse owner. If in doubt about the cause of your horse’s clinical signs, especially if they are not resolving despite attention to environmental and nutritional factors, always seek the assistance of your veterinarian. And in some cases hair analysis could be helpful.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.