People combat cold weather by putting on additional clothing, but horses fight the elements by using more energy to maintain body temperature. While most people can address their own needs, horses are dependent upon their owners to provide proper nutrition and protection from the weather, said Dave Freeman, PhD, PAS, Dipl. ACAN, Oklahoma State University Cooperative Extension equine specialist.
Energy for Body Warmth
"The temperature below which a particular horse starts to expend additional energy for maintaining body warmth (called the critical temperature) will vary," he said. He attributes this to several factors including the amount of fat each horse has, the thickness of their winter coats, how well the horse acclimatizes to the cold weather.
For example, a horse with short hair, exposed to wet, cold weather, might need significantly more energy when the temperature gets below 50° F (10° C). A horse acclimatized to cold weather, with a thick hair coat and fat cover, may not expend appreciably more energy until the temperature drops below 30° F (-1° C).
As a general rule, a 1% increase in the energy required to stay sufficiently warm is needed to replace the energy lost for each degree the temperature falls below the horse's critical temperature. Simply put, a horse owner would have to supply roughly two pounds more feed for each 10 degrees Fahrenheit below the critical temperature per day when horses are consuming typical hay and grain rations, a situation that is not practical.
Condition the Horse
"...Horses need to be preconditioned for cold weather by increasing fat thickness and body condition before the onset of winter," Freeman said. Freeman cautions that a horse manager cannot just provide additional feed to offset loss of body condition.
"Sudden changes in grain composition and amounts will increase the incidence of colic and founder," he said. "It's best to make adjustments in grain gradually over a period of several days, especially if horses already are consuming large quantities of grain."
Owners also should consider feeding large amounts of grass hay to horses restricted from forage. Free-choice hay helps horses exposed to cold weather, partly because of the heat generated by digestion and also as an aid to a continual supply of nutrients.
Shelter for Horses
Another way to lessen horses' stress resulting from exposure to wintery weather is to provide some form of shelter from wind, rain, and cold. Some pastures provide enough natural protection that manmade shelters are not required.
"Owners housing horses in areas unprotected from wet, windy weather should consider constructing windbreaks or sheds," Freeman said.
Freeman reminds owners to consider horse instincts and herd pecking orders when deciding on windbreak or shed design. Areas housing a single horse or two horses that are compatible with one another will allow for an enclosed shed with three or four sides. These structures should be similar in size to recommendations for stalls: 10 feet by 10 feet minimum for each horse.
The same type of structure will not work in pens with large numbers of horses, or groups of horses with large ranges in horse dominance orders.
"An enclosed, sided structure may increase horse injury to horses on the low end of the herd dominance order by the more dominant horses," Freeman said. "This type of structure may be inefficient because dominant horses will keep others from having access."
Freeman recommends single-sided windbreaks with a top cover be used in herds with both dominant and passive horses.
"Also, owners should consider two or three of these structures spread about the area because one long, continuous structure is easily guarded by dominant horses," he said.
In some situations aggressive behavior becomes such a problem that horses need to be separated. The more submissive horses generally will need more shelter because they are the ones that are usually in the least favorable body condition, Freeman concluded.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.