Whether to blanket your horse or not depends on many factors including body condition, winter riding schedule, turnout facilities, and environment. Horses can naturally withstand dry, cold weather very well. Their hair coat stands on end, trapping heat and creating a layer of insulating body heat. This layer can be disrupted by wind, rain, and dirt. Sleet and a cold rain are more debilitating than the snow. Clipped hair is unable to create that insulation layer.
A bad blanket with no insulation can actually be worse for your horse than not blanketing him/her at all. Here’s why: The blanket flattens down your horse’s hair, which keeps the natural warm air layer from forming. If the blanket has no insulating layer, the horse’s natural body heat rapidly escapes—and your horse will be colder as a result. You can tell if a blanket is providing proper insulation by running your hand underneath it when it’s on your horse. You should feel warmth from your horse’s body heat, but it should be dry warmth—not moist or damp.
There are different types of blankets. A stable blanket is not waterproof and should not be used outside for primary protection from the elements unless a waterproof turnout sheet is placed over it. A blanket designed for turnout will be waterproof and more rugged. Blankets range from sheets that have no insulation, to mid-weight blankets with about 220-280g of insulation, to heavyweight blankets that have about 380-500g of insulation.
Typically, older horses and foals have more difficulty regulating their body heat. Age shouldn’t be the only consideration for whether to blanket a horse, though. Some older horses have difficulty maintaining their weight; they may also experience an arthritic flare up from the cold and damp, which reduces movement and reduces the creation of body heat. Most horses in our area get less turnout time and exercise in winter because of unsafe ground conditions like deep snow drifts, icy walkways, and uneven/lumpy frozen footing in paddocks. Remember: Decreased movement results in decreased production of body heat.
Most horses with a natural hair coat can tolerate temperatures as cold as 5 degrees Fahrenheit before their body temperature begins to decrease. Given the proper nutrition and shelter, many horses do fine without ever being blanketed. Heavy breeds (such as drafts and Fjords) seem to be more naturally equipped for the cold weather than the lighter breeds (Thoroughbreds and Paso Finos).
It’s a good idea to provide more forage during the winter because the fermentation of the fiber in the horse’s gut produces body heat. A horse typically needs to consume 1.5 to 2% of its body weight in feed daily. That requirement increases 0.7% per degree below 18 degrees Fahrenheit. That translates roughly to: One extra pound of hay per 10 degrees below 40 degrees F—just to maintain your horse’s body temperature! Water consumption should be closely monitored to minimize the risk of dehydration and impaction colic.
A shelter that blocks the wind and precipitation can reduce a horse’s heat loss by up to 20%. Also, a horse kept outdoors continuously (with shelter provided), is better able to maintain his/her body heat than a horse that’s kept in a warm barn, blanketed at night, and then gets turned out during the daytime. It takes a few weeks for a horse’s “internal thermostat” to adjust to weather conditions, which is challenging for horses that travel south for a brief stay and return home to our frosty cold winter weather.
Keep in mind, if the weather changes and it becomes unusually warm, your horse can get overheated if his/her blanket is too insulated. Switching between a lighter blanket and a heavier blanket is necessary when weather conditions change abruptly.
The veterinarians at Fox Valley Equine Practice are routinely asked for blanketing recommendations based on outdoor temperatures alone. As you now know, many factors should be considered before deciding if/when to blanket your horse!
However, for those horse owners who want a less ambiguous answer, here are some general guidelines for blanketing horses:
Blanket a horse with a clipped coat < 55 degrees F.
Blanket a horse with a medium coat at < 35 degrees F
Blanket a horse with a heavy coat at < 20 degrees F.
REMINDER: Remove your horse’s blanket regularly to check for sores from blanket rubs or skin infections, and to be sure your horse is maintaining a healthy body weight.