Researchers Assess Horses’ Susceptibility to Cold, Heat Loss

Is your horse hot-natured or cold-natured? Or somewhere in between?

Norwegian researchers have found that horses’ susceptibility to cold is individualized. Breed, genetics, body condition, coat type, exercise level, diet, age, and health all contribute to how horses lose heat—and how humans should manage that heat loss through blanketing, shelter, and feeding.

“The common management of clipping, blanketing, and stabling in warm buildings is perhaps not the best we can do to help our horse maintaining thermal comfort,” said Grete H.M. Jørgensen, PhD, of the Norwegian Institute of Bioeconomy Research, in Tjøtta. “But it’s what everybody else does. It is what the professional riders do. And it is what we humans would do when we feel cold.

“Everyone loves their horses and wants to do the very best for them, but to be honest, I think the general knowledge about thermoregulation in horses is somewhat lacking,” she added. “Every individual should be evaluated separately, and management routines might change as the horse gets older, exercise routines are altered, or if the horse becomes pregnant or sick.”

Thermographic Readings of Coats

Jørgensen and her fellow researchers recently used infrared thermography to evaluate how 21 horses of mixed breeds, ages, body conditions, and workout programs maintained body heat. She said they found that, generally, warmblood horses (saddle-type horses) had shorter coat hairs and lighter-weight coats than coldblood (draft-type) horses. However, they noted significant individual differences.

On thermography, warmblood horses’ coats showed higher temperatures than those of coldblood horses. However, that doesn’t mean the warmblood horses were warmer. On the contrary, Jørgensen explained, these higher coat temperatures actually meant those horses were losing more of their body heat—the readings indicated the heat loss from the body onto the coat.

The Clipping Conundrum

In particular, the chest and shoulder/neck areas, as well as the rump, showed the highest thermographic readings. That means these are the areas where horses lose the most body heat—which is complicated by the fact that many horses lose hair in the neck and chest area from blanket rubbing, Jørgensen said.

It’s also complicated by clipping trends, she said. “The body parts most prone to losing heat in the cold are the ones that get sweaty first during exercise, the neck and shoulders,” she said. “Heat loss is a mechanism of upmost importance to horses, as they are prone to heat stress, (so) many owners clip their horses’ necks and shoulders to avoid heat stress during exercise. This is a very difficult situation for the horse.”

If a horse is clipped, he’ll need to be covered with a blanket, Jørgensen said. “But the horse cannot regulate temperature on one body part separately; if it becomes too warm on the back it will feel warm, even if the neck is clipped.”

Jørgensen doesn’t recommend just covering the clipped parts alone. More research, however, is needed to find practical solutions for dealing with exercise-induced sweat in the cold, she said.

Heat-Sapping Iron Makes Cold Feet

Iron shoes can also drain horses of body heat through their feet, said Jørgensen. In this first-ever study of heat loss associated with metal shoes, she and her colleagues found that horses tend to have colder feet, especially hind feet, when they’re wearing shoes compared to when they’re barefoot.

Her research confirms what she’s long suspected as a horse observer. “I have always thought that shod hooves felt colder when handling them,” she told The Horse. “And I have seen barefoot hooves leave a melting mark in the snow.”

Heat loss from the feet isn’t dramatic, but it’s worth considering in certain situations, she added. “This might be negative in really cold conditions or in horses spending longer periods of time in the lower parts of the thermoneutral zone (temperatures that don’t require extra energy use to regulate body temperature, but close to or sometimes crossing over lower critical temperature),” she said.

The full study was published the Journal of Thermal Biology.