How you decide when to blanket—or not blanket—your horse can depend on many factors, including climate, coat length, access to shelter, his individual internal thermostat, health, age, and weight.

Understanding A Horse’s Coat

You’ve probably noticed that blanketing can be a controversial topic.

“Everybody has an opinion, but nobody seemed to have the science to back it up,” says Michelle DeBoer, Ph.D., an associate professor at the University of Wisconsin River Falls with a research interest in horse blanketing. She began her research with the goal of improving horse welfare and reducing stress for owners making blanketing decisions.

To understand how to blanket horses, we must understand how their natural coats work. According to DeBoer, a horse’s coat provides warmth using piloerection. Piloerection, which occurs in many kinds of animals, works when the hair stands up on end. When you see your horse’s coat “puff up,” it is actually creating air pockets underneath the hair follicles, which traps warmth.

Weather conditions may impact your horse’s ability to fluff up. For example, a wet coat cannot use piloerection, which creates a risk that your horse can become cold. According to the website for Mid-Rivers Equine Centre in Wentzville, Mo., snow can often be kept at bay by a thick coat. Heat can stay trapped within, resulting in snow simply sitting on top of the coat.

If the snow begins to melt, it may indicate that your horse’s coat is not insulating properly. On the other hand, heavy rain that breaks through the top layer of a horse’s coat and soaks down to the skin poses a risk in cold weather.

“Flattening the Coat”

Many owners are concerned about blanketing because they fear it may damage a horse’s natural coat and insulating ability.

A blanket should not have a significant negative impact on the natural coat’s insulation. According to Fernando Camargo, DVM, Ph.D., an associate professor at the University of Kentucky and Sarah Coleman, executive director of the Kentucky Horse Council, there is no research that indicates that putting a blanket on a horse will make them colder by flattening their coat.

If you’re concerned that blanketing today means your horse will need to be blanketed more in the future, there is little need for concern, according to DeBoer. It takes approximately five to 12 weeks to see a change in a horse’s coat due to blanketing, and the changes don’t seem to have long-term effects.

In other words, if you decide to blanket one winter, it does not doom you to blanket the same way next year and beyond.

Thermoneutral Zone

At what temperature should you start blanketing? This depends on the individual equine and weather conditions. However, DeBoer states that horses have a “thermoneutral” zone where they don’t use any extra energy to stay warm (or cool).

This temperature varies greatly depending on the horse’s climate. DeBoer says that horses adjusted to colder areas don’t start burning additional calories until it is 5 to 18 degrees Fahrenheit, while horses that are accustomed to warmer regions need to produce extra heat at around 41 degrees Fahrenheit. If wet, horses begin producing extra heat at around 59 degrees.

Similarly, Rutgers University’s Netti R. Liburt, Ph.D., and equine extension specialist Carey Williams, Ph.D., state that 59 degrees Fahrenheit is also the approximate bottom of the thermoneutral zone for a body-clipped horse or one with a summer coat.

Weight and Health

A heavier horse has a bigger insulating layer of fat, which will keep him warmer when the temperatures drop. An underweight horse, on the other hand, may feel colder sooner than other horses in the same weather conditions.

An overweight or healthy weight horse could perhaps stand to burn some of the extra calories it takes to stay warm in cold conditions, while a horse that is underweight, a hard keeper, or in poor health may not be able to spare the same calories.    

Hay Use

A horse’s digestive system creates significant amounts of heat while breaking down fiber in the hindgut, kind of like an internal wood stove, so forage is an important part of keeping a horse warm.

According to DeBoer, this also means that blanketing can help reduce hay use during the winter. In her study on horse’s dry matter intake and condition, she found that “blanketed horses had a reduced hay intake compared to non-blanketed horses.”

If barns and owners are experiencing a winter hay shortage, or don’t have good access to places to put lots of forage in their fields, this may be an option to consider. It also can be important for horses who are stalled overnight, and therefore may go longer periods without forage.

Shivering and Ear Check

Sometimes an owner may worry that they can’t tell if their horse is too cold. DeBoer says that shivering is her No. 1 way to check.

“If a horse is shivering, he is too cold,” she says. “While they can shiver for short periods of time and be OK, if they are required to shiver for a long period of time as a way to stay warm, it can lead to weight loss and health problems for the horse. I most often see shivering when it is wet and windy.”

DeBoer also suggests that a more subjective way of gauging your horse’s temperature is checking the base of his ears.

“This can be an indicator of your horse’s condition, as a cold horse will reduce blood flow to extremities in an attempt to conserve heat by keeping the majority of blood within the core of the animal,” she says.

DeBoer notes, however, that this is not an “end-all, be-all” method.

All of these factors can feel like a lot to consider, so it’s important to observe your horse for yourself. Is his weight dropping, is he shivering, or is he sweating and hot in his blanket? When it rains, does his undercoat remain dry, or is he immediately soaked through?

When you take the time to observe your horse, you will eventually develop an idea of how he reacts to different weather conditions.

“If you choose to blanket, you need to be more vigilant in managing your horse, but if you don’t, you want to make sure he has the resources to stay warm on his own, primarily adequate or extra hay and a shelter,” says DeBoer.

Blanket Away! (Mindfully)

Blankets are useful tools, and you may use them for a variety of reasons. In real-world situations, it may not be possible to constantly micromanage your horse’s warmth. Most unclipped horses that are a healthy weight can manage winter on their own, especially with good shelter access.

Throwing a heavy blanket on a horse and then leaving it on when the temperature rises again could potentially be just as harmful as a horse being cold.

“When we over-blanket, it can trap too much heat underneath the blanket,” says DeBoer. “Besides the obvious concern of making the horse uncomfortable, if he gets so warm he begins to sweat, this can create an environment that fosters skin infections or rain rot.”

When blanketing, always consider when you will next be able to check on your horse and switch his blankets. Consider your resources and time when deciding how to blanket.

Further Reading
◆ Best Horse Blanketing Practices
◆ Feeding Your Horse in the Winter
◆ Winter Horse Care FAQs
◆ Keeping a Horse Blanket Clean

This article about the science behind blanketing horses appeared in the November/December 2024 issue of Horse Illustrated magazine. Click here to subscribe!

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