by Marcia Hathaway
University of Minnesota
Horses, given the opportunity to acclimate to cold temperatures, often prefer and are better off outdoors during the winter months. However, there are certain water and feeding guidelines that should be followed when caring for horses during cold weather.
Most adult horses weighing 1,000 pounds require a minimum of 10 to 12 gallons of water each day for their basic physiological needs. During winter months, water should be kept between 45 to 65°F to maximize consumption. Previous research indicated that ponies increased their water consumption by approximately 40% each day when the water was warmed above freezing during cold weather. Increasing salt intake will also stimulate a horse to drink more; adult horses should consume one to two ounces of salt per day. Waterers should be cleaned regularly, and clean, fresh water should always be available, regardless of temperature. If using a tank heater to warm water, inspect it carefully for worn wires or other damage, and check the water for electrical sensations or shocks.
When horses consume winter feeds, water requirements may increase. Hay and grain typically contain less than 15% moisture, while in contrast, pastures contains around 85% moisture. There are two common complications resulting from inadequate water consumption during cold weather: decreased feed intake and impaction colic. Even if quality feed is offered, horses will consume less if not drinking enough water. If less feed is consumed, horses might not have enough energy to tolerate cold weather. Fecal contents must maintain adequate moisture levels. If fecal material becomes too dry, intestinal blockage or impaction may occur. A horse will not develop an impaction in one day, but can over several days to several weeks of inadequate water consumption.
Snow or ice is not an adequate water source for horses. There have been a few scientific studies that show some horses who are acclimated to winter weather conditions can meet their water requirements from snow. However, there are serious health risks associated with snow consumption, including the length of adjustment period as horses learn to ingest snow, the actual water content of the snow, and total water intake. Therefore, some wild horses can receive their water needs from snow, but the risk of gastrointestinal tract problems, colic, and reduced feed intake is significant for domestic horses. The Minnesota Pet and Companion Animal Welfare Act states that snow or ice is not an adequate water source for horses.
Cold temperatures will increase a horse’s energy requirement as the need to maintain core body temperature increases. The temperature below which a horse needs additional energy to maintain body warmth is called the lower critical temperature. The lower critical temperature for a horse is estimated to be 41°F with a summer coat and 18°F with a winter coat (upper critical temperature is estimated at 86°F).
However, the lower critical temperature can be affected by individual horse characteristics. A horse with short hair that is exposed to cold, wet weather will have less tolerance to cold weather compared to a horse with a thick hair coat and fat stores who is acclimated to cold weather. Another factor that can influence lower critical temperature is the size of the animal. Smaller animals have a greater surface area relative to bodyweight and can lose heat more rapidly than a larger animal. More importantly, cold weather can slow growth because calories are diverted from weight gain to temperature maintenance. To minimize a growth slump during cold weather, young horses should be fed additional calories.
Energy needs for a horse at maintenance increase about 1% for each degree below 18°F. For example, if the temperature is 0°F, a 1,000 pound adult horse at maintenance would need approximately 2 additional pounds of forage daily. It is best to provide the extra energy as forage. Some believe that feeding more grain will help keep a horse warmer. However, not as much heat is produced as a by-product of digestion, absorption, and utilization of grain as is produced from the microbial fermentation of forage.
Most data suggest that the need for other nutrients do not change during cold weather. However, consider feeding loose salt instead of block salt, as horses may not want to lick cold salt blocks during winter months.
During winter months, heavy hair coats can often hide weight loss. Regular body condition scoring is recommended to gauge bodyweight and assess horse health. If a horse starts to lose body condition, increases in feed are recommended. Conversely, if a horse starts gaining excessive body condition, reducing the feed is necessary. Sorting horses by age, body condition, and nutrient requirements makes it easier to feed groups of horses appropriately.