WHEN HORSES COME IN FROM THE COLD
How a horse responds to winter weather may have more to do with his individual makeup than his breed or body type, according to new research from Norway. For a study conducted over two winters, researchers at the Norwegian Institute for Agriculture and Environmental Research chose 22 horses of various breeds—about half were coldblooded native Nordic horses and the rest came from warm-blooded bloodlines. The horses, who ranged from 3.0 to 6.5 on the body" condition score (BCS) scale, were all acclimated to the local weather. Before the start of the study, samples | of each horse's coat were S clipped and weighed to | quantify their thickness.
During the three-month study periods, each horse was observed turned out without a blanket in a specially designed paddock that offered three options: staying outdoors, going into a small run-in shed and going into an identical run-in space that contained a small overhead, infrared heater.
The researchers are quick to point out that the use of heaters in the study does not suggest that this amenity needs to be provided for horses. "We wanted to create a third choice," explains Grete H. M. Jorgensen, PhD. "If the horse would rather go into a heated shelter compartment instead of the non-heated compartment, this might suggest that the weather conditions were challenging his thermoregulation strategies so much that the horse needed [more protection than the unheated shelter could provide]."
The study horses were exposed to a variety of weather conditions in different settings. First, they were turned out for two-hour increments in their home paddocks without blankets; then they were allowed into the experimental pen for an hour, and their shelter choices were noted every minute. Any signs that they were having trouble regulating their body temperature, including shivering or standing tensely against the cold, were also documented.
[Reference: "Preference for shelter and additional heat in horses exposed to Nordic winter conditions," Equine Veterinary Journal, October 2015]
As might be expected, the data showed that wet, windy weather drove horses to seek shelter significantly more often than cold, dry conditions. However, the researchers report that each horse's individual characteristics seemed to influence his preferences more than general factors: For example, horses with thicker coats, regardless of breed or body condition, were more likely to spend time outdoors.
In cold, dry weather, only about 50 percent of the horses sought shelter in the heated compartment, indicating that overall, the horses had no need for the extra warmth it provided. However, when the weather turned wet or windy, horses were drawn to the artificial heat source.
"Both precipitation and wind reduce the animal's cover insulation," says Jorgensen. "Water may also cause the hairs to mat together and hence reduce the total cover depth as well as replacing the still air close to the skin with water."
Jorgensen says these findings suggest that it is unwise to generalize too broadly about equine shelter needs during the winter. "Each horse is unique and one should never assume that your horse would feel cold, or not, based on its appearance, its breed and the common knowledge of the people you might share stables with. Even the smallest changes in metabolic rate, feed types and feeding regimens, training, clipping and turnout time will have consequences for the individual's ability to handle changes in temperature, precipitation and wind," she says.
"To put it into perspective: A fat Arabian horse with muscles and a nice thick hair coat might handle the arctic winter weather conditions quite well compared to an old, clipped Icelandic Horse with few muscles and a low body condition score," she explains. "Even though the Arabian breed is indeed a warm-blood breed and the Icelandic Horse are categorized as a hardy, cold-blood horse breed."
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