Keeping Horses Warm in Cold Weather
With winter upon us, it’s important to protect your horse from the cold. Here are determining factors and other critical information to guide you:
The thermoneutral zone (TNZ) is the ambient temperature at which the horse is able to maintain its appropriate body temperature with little to no energy expenditure. The TNZ is influenced by the temperature the horse is used to, its age, and its health. It takes about 21 days for a horse to adapt to a new ambient temperature if it moves to a different climate.
Lower critical temperature (LCT) is the lowest temperature within the TNZ. Below the LCT, the horse must increase its metabolic heat to maintain normal body temperature. Upper critical temperature (UCT) is the highest temperature within the TNZ. Above the UCT, horses will sweat, dilate their blood vessels in their skin, and increase their respiratory rate and effort. The LCT in horses can range from 5°F in horses with a full winter coat who are used to colder weather to 41°F in horses that are used to milder temperatures. The UCT is still being determined, but current estimates place it between 60°F and 86°F.
Increased Energy Demands
Several studies have shown that allowing horses free-choice access to high-quality forage helps keep them warm. Horses should receive 1.5-2% of their body weight in hay a day. This amount should be increased another 2-3 lbs. for every 5-degree increment below zero the temperature falls. The fermentation of the fiber from the hay in the large colon and cecum creates internal heat more effectively than concentrated grains, acting as an internal furnace for the horse. Forage also takes longer to chew, which produces more heat and helps the horse produce more saliva to buffer against gastric ulcers.
Horses do just as well outside during the winter as they do in the warmer months of the year; they just need adequate shelter. Adequate shelter can be both natural and manmade. A run-in shed that provides a break from the wind and coverage from wet precipitation (e.g., rain; sleet; heavy, wet snow) is sufficient. Be sure it is adequately sized for the herd using it so a dominant horse cannot corner a horse lower on the pecking order. Natural cover in the form of evergreen trees or a wind break will also help keep horses warm.
Age and Weight
Age and weight have an impact on your horse’s ability to stay warm. Foals and senior horses have a more difficult time regulating their body temperature than a healthy, mature adult horse. It’s important to monitor horses in these age groups in case they need help staying warm throughout the winter.
Monitor your horse’s weight and body condition carefully going into and throughout winter. As your veterinarian, we can show you how to do this using a weight tape and a body condition score scale. Horses are better off going into winter a little more on the fleshy side than on the thin side as subcutaneous fat helps maintain body heat. It is also more difficult for a horse to gain weight in winter if they are already on the thin side. Monitoring your horse carefully will help you determine if he needs to be fed more, or if he is getting an adequate amount of food to stay warm without becoming overweight. Trending too far in either direction can lead to significant health consequences.
Monitoring horses’ water supply is very important in winter. Most horses drink warm water more eagerly in the winter than cold water. Keep in mind horses will be on a dry forage rather than a moist pasture during the winter months, so water intake is very important to help prevent impaction colic, choke, and other ailments caused by dehydration. Water should be checked throughout the day to be sure it is not freezing and water heaters are working properly. Plugging a water heater into an automatic surge protector is an important safety measure for any water heater. You should never rely on your horse eating snow to keep itself hydrated.