Several environmental conditions affect horses in the winter:

• Horses decrease feed intake in cold and windy weather—seek shelter.
• Snow accumulation greater than 7 inches covers grass and decreases intake of pasture. This decreases grazing time (24%) and decreases intake (22%).
• Pawing through deep snow to get grass greatly increases the energy requirement of the horse.
• In cold, windy conditions, horses lose more body heat and burn more energy to stay warm.

The “Lower Critical Temperature (LCT)” is the temperature below which metabolic heat production must be increased to maintain body temperature.

• Mature Horses (LCT) = 5 to 41º F
• Thin coat 41º F
• Thick coat 5º F

• Young Horses (LCT) = 12 to 32º F

For each decrease in coldness of 1 degree Fahrenheit below the critical temperature, there is an increase in digestible energy requirements for body temperature maintenance.

An average 1,000-pound horse requires 15 Mcal per day for maintenance under normal conditions. The following tables outline the additional digestible energy and hay intakes under inclement winter weather conditions.

Fiber should, in most cases, be the first ingredient to increase in your horse’s diet when trying to keep them warm. This is because the microbes in the hind gut produce heat as a by-product of breaking down fiber.

Estimated Feed Energy Increase at Different Magnitudes of Cold below the Lower Critical Temperature of Mature Horses

When wind and rain are added to the environmental conditions, the digestible energy requirement increases even further.

Effect of Wind and Rain on Digestible Energy Requirement for a 1,000-pound Horse at Maintenance

The tables above assume a 1,000-pound horse eating at least 1.5% of its body weight in hay to maintain body condition and health (at least 15 pounds of hay). The additional feed/hay intake is on top of the original 15 pounds plus of hay. A horse in freezing temperatures, also enduring rain and wind, would require 25 to 30 pounds of hay intake per day. This might be an unfeasible amount to supply to your horse or they might not be able to consume this much (older horses or pregnant mares). It should also be noted that most local grass hays are lower in digestible energy with values closer to 0.7-0.8 Mcal/lb, which further increases the quantity needed to maintain body condition in wintery conditions.

Standlee Premium Western Forage provides a variety of high quality forage products to help maintain body condition in winter conditions. Check out some great forage options to keep your horse supplied with a balanced diet at standleeforage.com.

This article was authored by Drs. Tania Cubitt and Stephen Duren.