Even though a horse may be "turned out" for the winter because he is not in active work, he needs protection from wind, moisture and cold. Whether you blanket your horse or not depends on many factors including his condition, his activity level, his hair coat, his level of nutrition, and the protection offered by your facilities.
Actually, preparation for winter begins well before the first snow. In August and September, horses living in temperate climates should be allowed an increase in body weight of about 5%, but not more than 10%. A 1200-pound adult can gain 60-120 pounds in the late summer or early fall. This extra flesh and fat will provide added insulation and an energy and heat reserve for when weather is particularly bad.
During cold weather, rations should be increased to counteract environmental stresses caused by wind, freezing rain, snow, sleet, and below-freezing temperatures. Feed by weight, not volume to know exactly how much is being fed. The hay ration should also be adjusted to compensate for low temperatures. For every ten degrees Fahrenheit below freezing, the ration should be increased 10%. When it is twelve degrees above zero Fahrenheit (twenty degrees below freezing), the a 1200 pound horse’s normal hay ration of 16 pounds per day should be increased to about 19 pounds per day (a 20% increase). Horses fed less than is necessary to combat cold and wind will burn fat and muscle tissue by shivering to keep warm and they will lose weight.
A horse's shelter requirements are fairly basic - a place to get out of the wind and wet during cold weather. It is not necessary or desirable to have an air-tight, heated barn for horses. In fact, that is one of the unhealthiest environments in which a horse can live. A cold, but not drafty, barn is healthier.
A pastured horse must at least have access to an adequate windbreak. Shelter can consist of a cluster of trees, a ravine, hill, canyon, or creek bottom as well as of man-made structures. A simple three-sided shed can be situated with the back wall to the prevailing winds (often north) and the opening facing the sun (usually south in the winter).
THE HORSE’S NATURAL BLANKET THE HAIR COAT
Most horses begin shedding their summer hair in August and start growing thicker winter coats. In order to produce a dense, healthy coat, a horse's diet should provide an adequate quantity and quality of protein. A normal winter coat has as much insulating capacity as most top-of-the-line blankets. The downward growth of the long hair coupled with the stepped-up production of body oils allows the winter coat to shed water and keeps moisture away from the skin. A dry horse has a much better chance of remaining a healthy horse.
A healthy horse can withstand temperatures well below freezing as long as it is sunny and the air is still. The winter coat absorbs heat from the sun and the horse's body and traps it next to the skin. During cold temperatures, pilo erector muscles make the hair stand up which increases the coat's insulating potential. Wind separates the hairs, thereby breaking the heat seal which results in a great loss of body warmth.
Snow showers, sleet, and the freeze-and-thaw typical of many northern areas are particularly hard on horses. A wet hair coat conducts heat away from the horse many times faster than a dry hair coat. In addition, wet hair tends to become plastered close to the horse's body, nullifying the air insulation potential of a fuzzy, erect winter coat.
A horse with a long winter coat should receive minimal grooming - a rudimentary "dusting off" or vacuuming of the hair ends. Vigorously currying a winter coat can disrupt the natural protective layer of oils which is essential for protection from moisture. After riding, rub the coat dry with a cloth or gunny sack or allow the horse to roll in sand or dry snow.
A fuzzy winter coat can make it difficult to determine condition by visual inspection alone. The round teddy-bear look can be deceiving - it makes even an underweight horse look like it is in proper flesh. Feel the rib area for a moderate fleshy cover once a week throughout the winter.
USING WINTER BLANKETS
Some horses may require the use of a blanket during the winter: the show horse, the clipped horse, the southern horse that moves north during the winter, the old horse, and the horse in severe weather with inadequate shelter. Blanketing adds expense and labor to the winter care routine.
Blanketed horses must be meticulously groomed on a regular basis to minimize rubbing and rolling. Proper blanket fit is paramount. Blankets that are too small can rip or cause rub marks and sore spots on the withers, shoulder, chest, and hips. Too-large blankets can easily slip and twist, possibly upside down which can cause the horse to become dangerously tangled and the blanket mangled. Blanket linings should be of a smooth material to prevent damage to hair, such as the mane near the withers.
Overheating can be a problem with blanketed horses, so each horse may need two or three types and weights of blankets. What is appropriate for low night time temperatures in a barn is not necessarily desirable for day-time temperatures in a sunny paddock.
Waterproof blankets keep precipitation off a horse but often do not allow heat and moisture from normal body respiration to escape. A better choice is a waterproof-breathable blanket which prevents rain and snow from entering the blanket but allows moisture to escape. A too-heavy blanket can cause a horse to sweat, become wet, then chilled. This can sap a horse's energy, lower his resistance, and create an open invitation for respiratory infections. Check for over-heating or dampness by slipping a hand under the blanket at the girth and flank areas.