Increase Hay Intake for Winter

Cold temperatures combined with wet, snowy, and windy conditions increase the feed requirements necessary to maintain the body condition in horses. Extra calories are required to meet the energy requirements needed for keeping warm. The best way to meet the increased energy requirements if feeding more good quality hay. A horse’s adaptation to cold weather is either acute (immediate) or chronic (long-term). The immediate response of a horse to a sudden change in temperature is to change its behavior. Horses seek shelter from the cold and wind or huddle together to decrease heat loss. Horses will stand with their heads away from the wind, their tails set low and into the wind. Horses stop foraging and stop moving to conserve energy.
On the other hand, it is not unusual to see horses running in cold weather, which increases muscle contraction, causing heat production. Shivering and other voluntary muscular activity can also generate substantial body heat. For chronic exposure, horses require 10-21 days to acclimatize to the cold. Horses develop a heavy winter hair coat. The coat acts as a tremendous insulator. Cold weather will cause the hair to stand up, trapping and retaining body heat.

Eric eating hay
Photo Credit: Peggy Auwerda

The thermo-neutral zone is when metabolic heat production does not need to be increased to maintain thermo stability.  The lower critical temperature (LCT) is the temperature below which metabolic heat production is increased to maintain core body temperature. Once the LCT is reached, physiological changes and human intervention, such as shelter and extra feed, are needed to help the horse cope with the cold. The LCT for young horses can range from 12.2oF to 32oF, and in adults, the LCT is as low as 5oF.

When cold weather persists at temperatures below the LCT, an increase in dietary energy is required. Dietary energy is the only nutrient that must be increased for horses kept at temperatures below their LCT. The main source of dietary energy (calories which convert to heat) is obtained from feed. Other heat sources include the sun, muscular activity, and mechanical heat in barns.

The average horse requires approximately 20 lbs. of forage per day, and winter weather can increase the hay needed by 30 to 50%. For each decrease in coldness of one degree F below the critical temperature, there is an increase in one percent digestible energy requirements for body temperature maintenance. Forage (hay) is the most desirable method to meet a horse's elevated energy requirements. Forages contain higher fiber than grains. Fiber is utilized through bacterial fermentation within the cecum and large intestine. Much more heat is produced in bacterial fiber fermentation than in digestion and absorption of nutrients within the small intestine (grains). RESULT – A more significant amount of heat is being produced by using forages.

Feeding good quality grass hay is the simplest way to ensure the horse will meet its energy requirement in the cold. A horse eating a round bale or large square should be fine in terms of eating enough to maintain energy balance. If you limit feed, feed 2X per day, the horse will need 1 to 3 flakes of extra hay per day. Energy intake is the most critical factor in determining how readily a horse develops a tolerance for cold. If a horse does not eat enough energy to offset the heat loss due to the cold, the horse loses weight. The extra cost of feed to rehabilitate a thin horse back to normal will equal or exceed the cost of the feed that should have been fed to maintain the horse’s body weight during the cold.

Horses should have access to some shelter – a timberline, natural bluff, or a shelter. The shelter is typically a 3-sided shed. Recommendations for the shed size are 100 sq. ft./foal, 120 sq. ft./yearling, and 150 sq. ft./horse. Horses conserve up to 20% more body heat in a shed compared to an open, exposed area.

By Peggy M. Auwerda
Equine Extension Specialist