by Kim Hallin
A horse’s skin and hair work together in amazing ways to provide natural protection from the outside world and to control body temperature. The more you understand about the important roles of skin and hair in overall equine health the better equipped you will be to make smart decisions that can keep your horse healthy in a variety of situations including inclement or extreme weather, stabling, showing and trailering.
Let’s Start with the Skin
Equine skin serves as the primary barrier between the outside world and the internal structures of the body. Considered an organ, the horse’s skin provides a barrier against the environment, protects from external injury, helps to regulate body temperature, prevents excess loss of water/electrolytes and gives the horse a sense of touch. Equine skin also contains a critical population of bacteria that live in healthy balance and act as competition to potentially harmful invading bacteria.
Averaging almost one inch in thickness overall, a horse’s skin depth varies considerably by area of the body. The thinnest skin (less than ½ cm. deep) is found on the head and underbelly. The thickest skin (1.5 centimeters deep) is on the lower back and rump. The skin contains hair follicles as well as millions of sensory nerve cells and sweat glands. With a huge surface area (approximately 7,750 square inches for a 1,000-pound horse and comprising 12-24% of the animal’s total weight), the skin also provides valuable protection from dehydration and infection. Finally, equine skin plays a role in regulating seasonal body temperature because skin temperature can help to trigger hair growth and/or shedding.
What Does the Hair Do?
Although equine hair is not considered an organ, it is still a critical body feature assisting with thermal regulation, protection against the elements (wind, sun, rain), sensory perception and the transport of pheromones, not to mention providing protection against insects and ultraviolet light damage. Equine hair also serves as a barrier to chemical, physical and microbial invasion to the skin.
Horses have three different kinds of hair: the permanent hair of the forelock, mane, tail, eyelashes, and “feathers”; the temporary hair that covers most of the body (it is shed seasonally); and the tactile hair on the muzzle and in the ears.
The long, wiry hairs that protrude from around a horse’s eyelids and muzzle (often referred to as “whiskers”) are actually sensors. Each one has its own nerve and blood supply as well as a corresponding region in the brain devoted exclusively to interpreting the information that the feeler picks up. Horses investigate objects by touching them with their whiskers to gather more information before proceeding. Whiskers act as important pre-warning devices when the horse’s face or muzzle gets dangerously close to an object. They also help the horse with depth perception in the blind spot under the muzzle. So, even though a horse (literally) can’t see what’s under his nose, he can still feel it and make decisions based on the information he receives when his whiskers touch it. Newborns also use these sensors to help find the dam’s teats shortly after birth. Horses that have their whiskers trimmed are more likely to suffer eye, ear and facial injuries or lacerations due to the lack of pre-warning they otherwise would receive when their head gets too near an object.
Mane hairs that are long enough to fall over the neck and/or face provide significant protection against insects, as do the hairs inside a horse’s ears. You will often see horses shake their heads when bugs are swarming in order to swat insects away with their mane or forelock. Manes can also help drain water away from the neck when it rains heavily, keeping the horse’s neck dry and warm underneath.
A horse’s tail serves several purposes:
1. Warmth – A cold horse will clench its tail to help prevent heat loss from the area under the tail and may even bring its tail all the way between its legs to cover the sheath or udder.
2. Insect protection – Horses use their tails as fly swatters/swishers.
3. Body language – For example, a flattened tail may mean fear. A tail lifted over the back might indicate enthusiasm. A swishing tail can be a sign of irritation.
Hair Growth and Composition
Horses that live outdoors year-round will have five distinct body hair coats during their lifetime: birth coat, foal coat, yearling coat, adult summer coat and adult winter coat. Equine body hair does not grow continuously, but rather in cycles. The growing cycle is when the follicle is actively growing a new or “living” hair. The resting cycle is when the mature or “dead” hair is simply retained within the follicle. After the resting cycle is the shedding phase.
The direction of hair growth is determined by the follicle structure within the skin. If the follicle is straight, the hair grows straight. If the follicle is slanted, the hair grows slanted. For the most part, the hair coat of all horses has a typical orientation pattern over the body, except for unique whorls, cow-licks, etc. It’s also important to note that the hair coat patterns of adult horses are quite different from the hair coat patterns of foals. These differences are believed to be related to different requirements for heat regulation, camouflage and possibly even sexual/social communication.
What Triggers the Growing/Shedding Cycles?
The most important factor in determining when coat cycles will transition is the changing length of daylight. This change in daylight hours triggers the brain, followed by the hormones, to respond. As mentioned previously, skin temperature does also play a role, but temperature alone is not the primary trigger. This is why blanketing or heated stabling can diminish a winter coat, but will not prevent it entirely. It’s also why a cold, wet season can delay a shedding cycle. Each horse is an individual biological system. So, the starting date of the shedding cycle will vary from horse to horse within the same year and will also vary from year to year on the same horse. Only the horse’s body itself can determine the healthiest timeline for any given shedding season.
How Does Thermoregulation Work?
The ability of the hair coat to regulate body temperature is directly related to its length, thickness and density per square inch of surface area of skin. Each hair follicle has a small muscle that is controlled by the nervous system. These muscles can pull the hairs to a standing or “puffed up” position in order to increase the insulating factor of the hair coat. When raised, the hairs will effectively trap a layer of air, which is then heated by the body, creating a toasty warm insulation. When the horse’s body begins to get too warm, the coat is easily flattened, thus decreasing the amount of insulation, increasing new airflow to the skin and providing a cooling effect.
Unfortunately, when humans blanket a horse, the weight of the blanket forces the hairs to lie flat. This means the horse no longer has control over regulating his own temperature. It also means the hair muscles don’t get exercised, which leaves them in poor condition. When we clip or blanket horses, we hinder their natural ability for thermoregulation leaving them vulnerable to becoming too hot or too cold. No matter how attentive and careful we are, we will never be as good as the horse’s own natural body and hair coat at self-regulating for ideal body temperature in any given moment.
Despite what many humans believe, horses are naturally very well adapted to deal with cold conditions. In fact, it is easier for them to warm themselves up than to cool themselves down. Unlike dogs, horses cannot pant to lower their body temperature. They must rely on sweating to cool the skin’s surface as the moisture evaporates. Many horse owners believe clipping is good because it helps a horse to cool itself. Unfortunately, it also takes away their ability to warm themselves. In nature, a sweaty or wet horse will later raise the hairs of its coat and turn them in different directions to allow the air to dry the moisture so they can warm back up. Ventilation and airflow are key in this process. Regardless of whether a horse is clipped or not, when drying takes longer than usual due to limited airflow in a stable, this can lead to chilling.
What Role Does Nutrition Play?
Hair is composed mainly of protein and it requires energy in order to be grown by the horse’s body. Poor nutrition will result in a poor coat quality.
Nutrients and minerals including zinc, iodine, biotin and methionine are necessary in adequate amounts in order for the horse to produce a shiny coat and healthy mane/tail hair. If your horse seems to be lagging behind in shedding and/or his coat is turning a burnt orange color, you might want to increase the amount of fat (such as supplementing with Power Stance powdered coconut oil) for optimal skin and coat health.
Skin health is also affected by nutrition. Issues such as dry, flaking skin are often improved with increased fat intake. Proper hydration and access to a quality water source is the cornerstone of skin health but a quality balanced diet is also important. Diets balanced in essential amino acids, Omega-3 and Omega-6, and vitamins and minerals are what promote healthy skin.
What about Grooming?
Grooming can help with shedding as well as distributing oils from the skin into the coat. Tools like Hands-on Gloves that feel rewarding to the horse have the added benefit of promoting bonding and relaxation as well. Some types of grooming, especially frequent bathing with soaps in the winter, can strip the horse’s coat of natural oils which are there to help keep the coat waterproofed.
When it comes to skin and hair, nature provides exactly what most horses need to stay healthy and safe. So you might want to think twice before reaching for those clippers or unpacking that winter blanket or bringing your horse in for his third bath of the week.
References and Additional Resources