Some may wonder why they must manage their horses differently during the winter months. This is because in a cooler or challenging environment, a horse will use more of its energy to maintain homeostasis and an appropriate body temperature.

As a quick reminder, an adult horse’s resting body temperature ranges from 99 to 101°F (37.2 to 38.3 °C). To maintain this temperature, the horse will need to burn more calories each day during periods of cold weather. It is also a reason horses are often known to lose condition over the winter months as they burn their caloric reserves. However, with an appropriate winter-feeding plan, horses can maintain body condition through these challenging months.

In two related articles, we discuss the importance of managing your horse’s nutritional needs during the winter. In the Winterizing Tips article, we discussed some behavioral and physiological changes horses go through during the winter. We also highlighted some management and nutritional strategies to help horses maintain their body weight.

In our Winter Forages article, we discussed the types of forages available during the cooler months. We also highlight the importance of feeding more forage during the winter. This is because as the horse digests hay (fiber), the good bacteria in the hind gut, known as microbes, produce heat. Therefore, when you feed more hay, more internal heat is produced within the horse, helping to maintain its body temperature. It is recommended to feed hay at least 3x per day allowing the horse to produce internal heat over a longer period during the day.

Many studies have investigated temperatures at which a horse will begin to experience cold stress and thus, need more calories. Generally, most horses are adapted to a low outdoor temperature of 50°F (10°C). When the temperatures are above these levels, a horse’s nutritional requirements usually do not increase. This adapted temperature can be lower once a horse has adjusted to cold winter temperatures. Some studies have shown horses can adapt to temperatures as low as 5°F (-15°C). It is also worth noting that it is estimated it takes horses about 21 days to fully acclimate to this temperature.

Adaptations to cold winter temperatures will differ by the age of the horse. Younger horses do not have the ability to withstand cooler temperatures as well as a fully mature horse. The lower temperature end for young horses ranges from 50°F (10°C) to a low of 14°F (-10). Again, this will depend on whether the horse is already adapted to a cold environment or not.

Once temperatures drop below the levels a horse is adapted for, their energy (calorie) requirements increase. During the cold winter months, on average, the energy requirements for a horse may increase as much as 25%. In extreme cold and wet environments, this may increase as much as 50%. The exact energy required during the cold winter months depends on many factors, such as:

  • Age of the horse
  • Class of use
  • Location
  • Amount of rain and wind
  • Length of hair coat
  • Housing

To maintain body condition and be better able to withstand a cold environment, horses will need more calories (energy) in their diet. We have highlighted the importance of the composition of the horse’s diet in a cold environment in our previous articles. Briefly, while it may be easy to just increase a horse’s daily feed to increase calories, feed on its own is usually not enough. This is because cereal grains, such as corn or oats, do not equate to better body temperature maintenance. Rather, diets higher in hay (fiber) have been shown to increase a horse’s heat output. Thus, hay is the first portion of the diet that should see a substantial increase during the cold winter months. It has been estimated that hay requirements for a horse in more extreme cool environments may be as high as 50% more compared to their hay requirements during warmer months.

Hay, especially if it is not high quality as commonly seen in the winter months, may not be enough to meet your horse’s energy requirements. Adjustments should then be made with an increase to your horse’s daily feed ration. You could also add a fat supplement to your horse’s daily ration, such as K Finish®.  We understand calculating the exact calories required is complex to calculate and will highly depend on your individual horse’s needs. Therefore, we always suggest you reach out to us for help in determining the best feed program for your horse.

Overall, the take home message is that horses need more calories in their diet during the winter requirements to sustain body condition and maintain an appropriate body temperature. With appropriate adjustments to your horse’s diet, horses can survive and thrive in many cold climates.

Chris J. Mortensen, Ph.D.