United States Eventing Association

This educational article is brought to you by Standlee Hay Company, the Official Forage of the USEA.

Several environmental conditions affect horses in the winter:

• Horses decrease feed intake in cold AND windy weather – seek shelter.
• Snow accumulation greater than seven inches covers grass and decreases intake of pasture - 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 one degree Fahrenheit below the critical temperature, there is an increase in digestible energy requirements for body temperature maintenance.

An average 1000-pound horse requires 15Mcal 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 horses’ diet when trying to keep them warm. This is because the microbes in the hindgut 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

Difference in F Below Critical Temperature	Digestible Energy Increase (Mcals/day)	Average Feed Intake Increase (lb/day)*
0	0	0
10	2	2
20	4	4
30	6	6
40	8	8

*Assuming an energy density of 1.0 Mcal/pounds, which is typical of good, quality hay.

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 1000-pound Horse at Maintenance

Average temperature		Additional Mcal/day	Additional Hay
32 Degrees F	10-15 mph wind	4-8 Mcal/day	4-8 pounds of hay
32 Degrees F	rain	6 Mcal/day	6 pounds of hay
32 Degrees F	rain and wind	10-14 Mcal/day*	10-14 pounds/day

*May not be able to consume enough hay to meet requirements.

The tables above assume a 1000-pound horse eating at least one and a half percent 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 may be an unfeasible amount to supply to your horse or they may 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.