Winter is here! The days are short, and the nights are long and cold in much of the country. As we manage our horses in the colder weather, the question arises of whether or not to blanket your horse. The short answer is “no,” but let’s look at why that is, and under what circumstances blanketing may be preferred or necessary.

How a horse stays warm:

Horses have developed very efficient means of staying warm, even in very cold temperatures. Your horse’s coat is comprised of two types of hair: longer stiffer guard hairs; and a soft, fluffy undercoat. The guard hairs “guard” or protect the soft hairs from dirt and water, shed off rain, and collect moisture from sweat that might damage the undercoat. The softer, fluffier hairs of the undercoat trap warm air between and act like insulation around your horse. Natural oils are produced that coat the hair to make them water resistant. Each hair is connected to the piloerector muscle. This muscle allows the hairs to be stood up or laid flat. When they stand up, warm air trapped between them, just above the surface of the skin. When they lie down, warm air is released from between them, cooling the area above the surface of the skin.

How much winter hair will my horse get?

Horses will start to grow their heavy winter coats sometime in late August in most parts of the United States. The hair growth is actually linked to the length of daylight, not the temperature. How thick their coat will grow does depend some on where you live. A horse in Florida will not grow nearly as heavy a coat as a horse in Minnesota does, but they all grow a thicker coat for winter.

What role does nutrition play?

Besides the hair coat, given the right nutrition, horses will start to put on a layer of fat in late summer and early fall in preparation for colder weather to come. Nutrition also plays a role during the cold weather. It is important that your horse gets enough hay to eat. The fermentation of hay in the horse’s hindgut produces an incredible amount of heat. Basically, your horse has a built in furnace that is fueled by hay. And that sudden burst of crazy running around the pasture? While it may seem that your horse or horses have just been spooked, or have gone nuts, this moving around is another way to generate heat.

How much cold can a horse tolerate?

A Canadian study found that horses can tolerate temperatures down to 5° F before they show any drop in body temperature. However, certain conditions do change your horse’s ability to keep warm. Rain and wind are the two most important. Rain will flatten the hair coat and prevent the undercoat from providing that layer of warm air. Wind will blow the warm air from the surface of the skin. Snow is less of a problem. In fact, snow will collect on your horse’s coat and act as a layer of insulation.

When don’t I need to blanket my horse?

  • When he has a natural winter coat
  • When he is healthy and in good body weight
  • When it is not too windy or raining
  • If the temperature says above 5° F

When do I need to blanket my horse?

  • When he has been clipped for winter
  • When he is sick or injured
  • When he is underweight (or any “hard keeper”)
  • When he is older, with weight issues, or difficulty moving around
  • When he has been recently moved to a colder climate (Expect it to take 10-21 days for a horse to acclimate to a new climate)
  • When it is Windy or Rainy or both
  • When there is no available shelter

Here are some general guidelines:

  • Body Clipped Horses: Start blanketing when the temperature gets below 60° F, or anytime it is rainy or windy
  • Moderate Hair Coat Horses: Start blanketing when the temperature goes below 40° F
  • Heavy Hair Coat Horses: Start blanketing when the temperatures go below 30° F

Do keep in mind, however, that most horses with a natural hair coat will do fine without blankets as long as there is no wind or rain.

It is very important to keep in mind that there are times when blanketing is worse than not blanketing. A blanket will make your horse’s hair coat lie flat, thus removing that insulating layer of warm air. If the amount of insulation in the blanket is less than what your horse’s natural coat would provide, then he will be cold. Make sure that any blankets used for turnout are waterproof! A wet blanket will make your horse cold. Too many blankets, or too heavy a blanket will make your horse sweat, make the hairs lie down, and make your horse cold. Stick your hand under your horse’s blankets to make sure he is not too hot. Additionally, you should not see sweat marks on your horse when you take the blanket off.

How to blanket properly:

Proper fit is essential to keep your horse warm and safe. Make sure that the blanket is not putting pressure on your horse’s withers, chest, or shoulders. You may have to try several styles of blanket to find the one that fits your horse correctly. Many horses, especially those that are clipped, will develop rub marks on the shoulders. Slick undergarments are available to help with this. Spraying the inside of the blanket with a silicone grooming spray can also help.

Remove your horse’s blanket often to make sure that any rubs have not turned into sores or that he hasn’t developed rain rot under his blanket.

Make sure to use turnout blankets when horses are turned out! These blankets are designed to stay in place when your horse runs and rolls; they are waterproof; and they are generally of studier materials to withstand herd turnout. Stable blankets are not waterproof, plus your horse can get tangled up in a blanket that is not intended for turnout.

A blanket that is too small can cause pressure sores and not provide enough warmth. Likewise, a blanket is too large can be dangerous from being too loose, as well as allow too much cold air to flow underneath it.

Registered 2011 by Equestrian Collections
Author: Sallie S. Hyman, VMD, DACVIM, CVA

Information in this article is for educational purposes only and is not a substitute for evaluation by an equine professional. In particular, all horse owners should seek advice and treatment from a licensed veterinarian, such as TEVA, for their horses' medical care.

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