Your horse’s winter coat: what’s it all about?
A horse’s coat is made of two types of hair: a fluffy, dense undercoat and a stiffer protective coat called guard hairs. The undercoat insulates your horse by trapping warm body heat between the skin and cold air. Guard hairs keep the undercoat clean, shed rain and hold moisture to prevent it from getting to the undercoat.
Long winter hairs are attached to a layer of muscle that moves the hair as needed for additional insulation. Each hair can stand up or lay down and be turned in a particular direction. When the hair is standing, your horse looks fat and puffy, which allows more space to trap and warm the air. When the hairs lay down, they act more like a cooling device and the warm air is moved away from the horse’s body. The hairs can also be “pointed” in a certain direction to help deflect wind and weather.
What if it rains when it’s cold? Most water hitting a winter coat runs off, and the coat will withstand quite a bit of water before soaking through to the skin. If rain does get through the coat, the horse will get chilled and loose body heat up to 20 times faster than a dry horse. The moisture flattens out the hair and eliminates the air spaces between the hairs, which reduces the insulating effect.
Horses rarely get frostbite. A horse’s muzzle has plenty of blood vessels that allow it to withstand extreme cold without freezing. Their long nasal passages with bone spirals and an air pouch warm the cold air before it reaches the lungs.
A horse’s feet and legs can also withstand intense cold without discomfort or damage even when standing in deep snow. The area below the knees and hocks are made of bone and tendons which need less blood circulation than muscles, which make them less susceptible to frostbite. If the horse’s feet start to get cold, shunts open up so the blood flows from the smallest arteries directly into the veins, so the feet warm up.