In the absence of wind and moisture, horses tolerate temperatures at or slightly below 0° F. If horses have access to a shelter, they can tolerate temperatures as low as -40° F. But horses are most comfortable at temperatures between 18° and 59° F, depending on their hair coat.
Although, horses that are well adjusted to colder climate temperatures may still feel comfortable between -8 to 15°C. Whereas horses adjusted to warmer climates may start to become uncomfortable when the temperature drops below 10°C. Typically, horses require 10 – 21 days to adapt to the cold.
Horses living outside should have access to adequate shelter from weather. Trees and three-sided sheds or stables are great options. With no wind or moisture, horses tolerate temperatures near zero degrees Fahrenheit, and even colder if a good shelter is available.
Like people, healthy horses' average temperature will vary slightly between individuals but will generally fall within a recognised range. In the past, most of us learnt that the temperature range of a healthy horse should be between 37.5oC and 38.5oC.
Also keep in mind that horses have thick winter haircoats that provide plenty of protection against the cold. This thick haircoat also tends to be very fluffy and trap air. This layer of air serves as an extra layer of protection in the cold. This layer of air is lost when a horse's coat is laid down flat.
Horses cope very well in cold temperatures – it is wind and rain that they can struggle with. If you can, provide a windbreak, like a field shelter or even a line of trees, to block some of the wind or rain.
The LCT for horses will differ a little for each horse, but for a healthy adult horse at a good weight the LCT is anywhere between -15 and 5 degrees celsius. For horses in Australia I would estimate the average LCT to be around zero degrees.
When the temperature drops to – 5°C, the horse will need another 10 – 21 days to adapt to this increasing cold. This process continues up to –15°C, which is the lower critical temperature (LCT).
The normal range for temperature is between 37.5 and 38.5 degrees Celsius and if your horse's temperature is above this range it is very important to get veterinary advice quickly.
When considering rugging your horse, it is important not make this decision based on how you feel. Horses don't feel the cold like we do and naturally grow a thick coat in winter to keep them warm.
Cold weather alone will not give your horse a respiratory infection. However, cold air and winter management choices might influence the health and function of your horse's respiratory tract, increasing his risk of exposure to infectious agents or exacerbating chronic problems such as equine asthma.
Horses need salt year-round, and they will seek out the salt that they need. Making certain your horse has access to salt in the wintertime is especially important to protect against dehydration, and subsequently, impaction and colic.
The cold horse will be seen shivering much more frequently or when all the other horses are not. Wet cold weather is harder on horses than dry cold, and a rainy 35-degree day will cause a lot more shivering than any other weather condition.
“Normal temperature varies in horses, just like in people,” Dreyfuss explained. “An adult's normal temperature will range from 99 degrees to 101 degrees. Once you get over 101, for most horses, that would be a low-grade fever. For clinical studies, we often define fever as greater than 102 degrees.
However, horses are most comfortable at temperatures between 18° if the horse has a winter coat and 59° if the horse has a summer or wet coat, Hathaway said.
Myth #1: Horses need blankets to stay warm in the winter.
Reality: Most horses DO NOT need blankets to stay warm, even in the most frigid of temperatures. However, some horses absolutely DO require a blanket to stay warm.
The normal body (core) temperature in the mature horse is 37.5-38.0° C (99.5-100.4° F). Any temperature below 37.5° C (99.5° F) is considered hypothermia in the mature horse. In humans hypothermia is defined as a drop in core temperature below 35° C (95° F).
The temperature you are used to feeling under the blanket is too hot for a healthy horse. Why? Because a horse's body temperature is supposed to be maintained at 38 deg which they can do effectively un-covered but can't with rugs on.
Cold Stress
Critical temperature is the temperature below which a horse starts to expend additional energy to provide warmth. This temperature for individual horses will vary because of fat cover, hair thickness, acclimatization of the horse to cold, hair/coat wetness, and wind chill.
If you think their winter coat seems thin, stabling at night can help them stay warm. Consider the state of your field too, as it will impact on your horses' health too. If your horse doesn't have access to a shelter in your field, stabling them overnight may be something to consider.
Horses that are exposed to the elements all night long will often fare better when kept in a stable. If you would prefer to keep your horse out in the pasture, you might want to consider the option of a field shelter.
Here are some general guidelines: Body Clipped Horses: Start blanketing when the temperature gets below 60° F, or anytime it is rainy or windy. Moderate Hair Coat Horses: Start blanketing when the temperature goes below 40° F. Heavy Hair Coat Horses: Start blanketing when the temperatures go below 30° F.
Coleman said horses' hair coats can effectively protecting them from cold temperatures, but they stand up less to wind and wet conditions. “If a horse's coat gets wet in rain or snow, it can dramatically chill them,” he said. “You may need to bring them inside a barn to dry and warm up.