Horse Winter Coats: How & Why They Grow Them

Horse Winter Coats: Ultimate Guide

If you have a horse, you’ve noticed the seasonal differences in his or her coat. A horse will naturally become fluffy in the fall and will naturally shed out in the spring. Have you ever wondered what’s behind these changes, and what can affect your horse’s seasonal hair growth? 

Why do horses grow winter coats? Horses have several mechanisms that allow them to retain their body heat in the coldest of temperatures. One of those mechanisms is the natural growth of a winter coat. Winter coats keep horses insulated and protected in the most extreme temperatures, but there are measures we can take that may inadvertently and negatively affect their growth. 

Keep reading to learn everything you need to know about your horse’s winter coat, including the external factor that directly causes it to grow, how you can unknowingly affect that, and whether or not a winter coat is sufficient to protect a horse in the coldest of winters. 

When Does A Horse’s Winter Coat Growth Begin?

Most owners will see their horse’s winter coat begin to come in around late August to mid-September, depending on the climate. Horses in northern climates may begin to show winter coat growth a few weeks earlier than horses closer to the equator. 

While many equestrians believe that the growth of a winter coat is triggered by the temperature, this isn’t true – if it were, the coat wouldn’t come in until after the horse has already begun to need it.

A horse’s winter coat is not like the coats we put on in the cold weather – they don’t come in all at once, and instead it can take months to achieve full fluff. 

What Triggers the Growth of a Horse’s Winter Coat?

So, if it isn’t the temperature that causes the winter coat to begin coming in, what is it? The answer to that is daylight, or rather, the diminishing of it. As the days begin to shorten, melatonin production increases.

The hormone melatonin is responsible for many body functions, one of which is the growth of an animal’s winter coat. This is why horses in northern climates grow their coats earlier, as the days are shorter than those in southern climates. Horses closer to the equator grow their coats later than their northern friends because they experience more daylight during the colder months.

The opposite is true as well – after December, the days begin to lengthen. As the daylight increases, melatonin production decreases, and the horse will begin to naturally shed her winter coat.

Coat growth will generally stop around the winter solstice, and your horse will start noticeably shedding around February, depending on the region. Though I don’t like to interfere with my horse’s winter coat growth, shedding can be especially itchy, and most horses appreciate extra grooming around this time.

Variations In Horse Winter Coat Length and Fullness

This may lead you to believe that horses in northern climates also grow fuller, longer winter coats. That would make sense, as they are the horses that need more cold protection, but while changes in the daylight affect when a horse’s winter coat comes in, it doesn’t impact the fullness of the coat.

That is mainly determined by breed. Whether discussing natural selection or intentional breeding, the outcome is the same – horses with heavy, long coats do not do as well in hot climates, and horses with naturally sparse winter coats are less likely to be found in very cold climates. 

How Do Winter Coats Protect Horses?

What exactly is it that allows a winter coat to protect a horse from the cold? The answer may seem obvious until you dig in a little more deeply.

The reason a winter coat protects the horse’s core body temperature is not only due to the extra layer of hair but rather the pockets of air this extra layer creates. Much of this is due to what we call “piloerection.”

Piloerection is the raising and lowering of hairs and the ability to aim them in different directions. We humans have this ability as well – but without the natural winter coat, all we have to show for it is goosebumps.

It has been shown that piloerection can increase coat depth by 10-30%. This depth is important because it results in a warm layer of air between the coat and the horse’s skin, keeping the horse’s body heat from escaping.

This is the same reason we wear jackets in the cold – the jacket does not generate any heat of its own but keeps our own body heat from escaping by acting as a buffer. 

Are Natural Winter Horse Coats Sufficient In The Coldest Weather?

The answer to whether a horse’s natural coat is sufficient to protect him or her in the coldest of winters is a general “yes.”

Horses are found thriving in the coldest corners of the world and have even been used in trekking expeditions in Antarctica (quite happily). That said, while you will find horses happily frolicking with a layer of snow covering their coats and icicles hanging from their nostrils, this doesn’t negate their need for shelter

A horse requires some form of shelter not from the cold itself but from the wind and rain. Both wind and rain will flatten the top layer of a horse’s coat, eliminating the gap of warm air that sits between the horse’s skin and the external temperature.

This impacts the ability of a horse to maintain body temperature and stay warm. A shelter – even a crude one – can protect the horse from the elements that will render his or her winter coat ineffective. 

Should Horses Wear Blankets In The Winter?

This topic is hotly contested, but it has been shown that, in most cases, horses do not need blankets in the winter. Those situations that do call for blankets are dependent on the horses and not on the climate.

For example, my thoroughbred cross, Pepper, needs a blanket when it’s 50 degrees and rainy. However, my draft cross, Ruach, has been fine without a blanket while soaking wet at 17 degrees.

Horses have many protections against the cold weather, and the winter coat is only one of them. While there are exceptions, most healthy, mature, acclimated horses prefer not to be blanketed.

One factor to consider is that blankets can impact the horse’s natural piloerection which makes the muscles required for that mechanism weaker. This means that a horse who is blanketed will end up requiring blankets as his natural protections have weakened. 

Another note is about the horse’s winter coat itself. Many equestrians recommend not blanketing before the winter solstice. Blanketing can impact the growth of a winter coat, and that growth is meant to continue until mid-December when the days go from shortening to lengthening.

If your horse is blanketed prior to that time, he may not be able to grow as full a coat as he would otherwise, further reducing his body’s natural protection.

Let’s ask the horses

Believe it or not, we can ask the horses themselves whether they’d like to be blanketed. A Norwegian study trained 23 horses to use abstract symbols to 1) request a blanket be put on, 2) request a blanket be taken off, or 3) request no change.

Most often, the horses requested their blankets be removed. Those horses were usually found to be sweating under their blankets, even on cold days.

What Other Cold Protection Measures Do Horses Have?

Again, the growth of a winter coat is just one protection that a horse has against the cold weather (though a very important one). Other natural protections a horse has include:

  • Thick skin – horses have naturally thick skin, which acts as its own insulation.
  • Large size – generally, the larger the animal, the more body heat they are able to maintain. This is because there is less surface area (from which to lose body heat) relative to body mass.
  • Artery constriction – during cold weather, the arteries to the skin constrict, reducing the amount of blood brought to the skin. This helps maintain body temperature as the blood isn’t traveling to the surface area in great quantities, cooling down, and then returning to the core.
  • Body fat – most horses naturally put on weight in the fall. In fact, the month of October is known as the time of “high skies and fat horses” in Korea. 
  • Digestion – believe it or not, a horse produces significant heat while digesting, especially during the process of fermenting forage like hay. This is one reason that hay is recommended over the winter as opposed to grain supplementation (though that is not the only reason).

Helping Our Horses Tolerate the Coldest Weather

We all want what’s best for our horses. When it comes to cold weather, the best we can do may just be nothing at all. So long as your horse has access to shelter that protects him from both the wind and the rain, is well-acclimated to your climate, and is in good health, he should be able to grow an adequate winter coat to protect him sufficiently as the temperatures dip.

A horse’s body can (generally) provide him everything he needs in the cold – sometimes, the hardest part is letting go and trusting in that. 

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Carmella Abel, Pro Horse Trainer

Hi! I’m Carmella

My husband and I started Equine Helper to share what we’ve learned about owning and caring for horses. I’ve spent my whole life around horses, and I currently own a POA named Tucker. You can learn more here.

Thank you for reading, and happy trails!

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