Is your horse cold in the winter? The following excerpt from Keeping Horses Outdoors by Iveta Jebáčková-Lažanská helps answer that question by addressing the science behind your horse’s temperature management.
Horses are naturally equipped to handle the colder months; summer heat tends to cause them more trouble than winter temperatures. As soon as the days begin to shorten in the fall, hormones responsible for coat growth kick into action by beginning to produce longer and thicker hair as well as a thicker undercoat. In addition to daylight, temperature plays a role: thermoreceptors will perceive a cold autumn and trigger the growth of a thicker coat. If a horse is kept indoors or blanketed, horses adapt by producing less winter fur.
As soon as the days begin to lengthen in December, horses will stop producing warmer coats, even if January brings extreme cold. This isn’t something to worry about, as horses who have spent the seasons in the same place will have a well-established coat—even a sudden hard frost won’t be an issue. (This is why it’s best to transition a horse from an indoor situation to your outdoor stabling in spring or summer.) However, it’s important to have well-fitting blankets on hand in case a horse develops a problem regulating his temperature due to illness. I’m not a fan of preventative blanketing for outdoor horses, but this doesn’t excuse irresponsibility. Each horse should have at least one insulated blanket and a waterproof sheet, even if they both gather dust for years. At the end of the day, it’s better to have an unnecessary blanket in your closet than to have a shivering, wet horse out in a blizzard. Calling a vet at night is a much greater inconvenience and expense than finding good blankets for your horses.
One of the most frequently asked questions in the early days of outdoor horse keeping was whether horses were cold living out in the winter, and the answer, more often than not, was: they’re horses, not people… they’re fine! But many caretakers, especially with purebred horses, saw the exact opposite: simply put, their horses were cold. It doesn’t always require the coldest temperatures, but sometimes just a quick drop from warm to cool. Cold, wet weather can really have an impact on a horse’s well-being. Wild animals have far more options when it comes to finding shelter from the wind and cold. They can find shrubs, tree cover, or uneven terrain to protect them from wind gusts.
Maintaining an optimal body temperature is an absolute necessity for any warm-blooded organism. A constant body temperature ensures the normal functioning of bodily processes. The heat that a horse receives from his environment, together with the heat he produces, must be in equilibrium with output. If this equilibrium is disturbed, overheating or excessive cooling can make a horse very uncomfortable and even quite sick.
A horse’s muscle mass is excellent at retaining the heat produced by processes like digestion (fermentation of fiber in the intestines) and producing heat through exercise. A horse’s core isn’t subject to temperature changes based on his surroundings (because horses are warm-blooded), but the peripheral parts of the body (ears, hooves, skin) behave much like a cold-blooded animal’s would: they partially adjust to the ambient temperature, helping to maintain a stable core temperature. This is why you can’t tell whether a horse is cold by feeling his ears!
Temperature Management
Horses are excellent at regulating blood flow in the subcutaneous vascular network, which significantly influences temperature management of the entire body. Heat loss can be managed by vasoconstriction: blood flow is reduced in areas where blood would be cooled by being close to the surface of the skin. Horses are also able to cool off through vasodilation: by expanding these same blood vessels, surface contact is maximized and excess heat is transferred through the skin.
Skin, subcutaneous tissue, and fat act as powerful insulators. For this reason, it’s a good idea to have horses go into the winter season with a few fat reserves—they will be far less bothered by the cold than a skinny or underweight horse.
Also, a well-made shelter can help protect a horse from the worst weather—an animal protected by a shelter can save up to 25 percent more energy reserves than an unprotected one. This is no small thing on difficult days! Horses that aren’t as cold on a windy, heat-robbing day will consume hay at a more relaxed pace as well, saving some strain on your wallet. A well-thought-out shelter, whether you build new or rebuild by converting an existing building, is an investment which will pay you back over time.
Shivering
Some take a shivering horse as the definitive signal that it’s time to blanket. Others believe that because shivering produces heat, the horses are warming themselves and are actually fine. So what’s the real story?
Peripheral thermoreceptors are activated by the skin becoming cold. As soon as a horse’s usual defenses fail to maintain a comfortable temperature—hair bristling (increasing the coats’ ability to insulate against the cold) and vasoconstriction (narrowing of the subcutaneous blood vessels)—the horse will begin to shiver. Using muscle tremors, the body will be able to increase heat production by about 30 percent. But there’s a catch—this only works for a short time, and it uses a great deal of energy.
Unfortunately, the first horses to begin shivering are usually somehow compromised: skinny, sick, old, or recovering from illness or injury. These horses are the ones with the smallest energy reserves, but even a fat, healthy horse can’t produce heat for long by shivering—the energy necessary for such demanding work is exhausted early. Although the body has other defenses against the cold as well (accelerated metabolism, for example), their effectiveness is limited. Shivering should be considered a sign that your horse is headed toward hypothermia—don’t take it lightly.
Tip: If you aren’t sure whether your horse is cold, place a hand by the elbow of a front leg. If this area is cold, your horse is cold enough that he’s uncomfortable.
This excerpt from Keeping Horses Outdoors by Iveta Jebáčková-Lažanská is reprinted with permission from Trafalgar Square Books.
