By Kimberly Peterson, DVM
Cold and inclement weather conditions present special challenges for the horse. Whether a horse is turned out or exercised regularly, you need to be focused on the nutritional requirements of your fuzzy, four-legged friend. Horses are naturally well-adapted to thrive in frigid weather if they have the basics of adequate calorie intake, palatable water, and protection from wind and severe precipitation.
It is important to take into consideration any additional stress factors when assessing the caloric needs of your horse. Other calorie-burning conditions, such as late gestation, chronic pain, metabolic diseases, contagious illness, or parasite infestation, significantly increase the body’s demand for calories. Frequent assessment of physical and environmental conditions is necessary to maintain optimum body condition.
Before severe weather sets in, your horse needs a physical examination, including a dental exam and current immunizations and deworming. Consider asking your veterinarian to check a complete blood count and blood chemistry panel to rule out any underlying conditions that add stress to the horse.
You will encounter several calorie units throughout equine literature. A calorie (c) is the amount of energy it takes to raise one gram of water one degree Celsius. A Calorie (C) represents the amount of energy it takes to raise one kilogram (1,000 grams) of water one degree Celsius. The Calorie, also called a kilocalorie (Kcal), is the unit of measure used in human nutrition. A megacalorie (Mcal) is 1,000 kilocalories. Megacalorie (Mcal) is the unit used to measure energy in equine and other large animal diets.
Generally, horses at rest in ambient temperatures of 70°F consume 2% of their body weight in roughage (hay) per day. A 1,100-pound horse will eat approximately 22 pounds of hay per day. Assuming an energy density of 1.0 Mcal/lb, which is typical of many hays, this equates to approximately 22 Mcal or 22,000 Kcal.
Roughage in the diet is the main source of heat for the horse. The bacterial fermentation of fiber in roughage, occurring in the large intestine, results in the majority of heat produced during digestion. Horses unable to consume enough hay to maintain body condition might be supplemented with grains and oils. Many horses do very well on a diet of 100% hay and should always have at least 50% of the diet as hay. Sick horses or those at increasing levels of exercise or illness might consume more calories with the addition of cereal grains (oats, barley, rye, wheat, rice, and corn).
Oats have the advantage of carbohydrate energy in addition to high fiber content for heat production, compared with other cereal grains. Oats provide one-third more digestible energy than hay (1.30 Mcal/pound of oats). Corn has less fiber for heat production, but it contains 50% more energy than hay. Be sure to weigh grain. Do not rely on volume (i.e., a scoop or coffee can) to accurately measure a ration.
Added fat in the form of vegetable oil is an efficient calorie source at 4 Mcal/pound (four times the energy of hay). Up to 12% of the day’s total calories in the form of fats and oils is well tolerated. While fat digestion releases almost no heat, it provides calories for energy and the maintenance of body condition (1 cup vegetable oil=2 Mcal).
A horse with a moderate hair coat starts requiring additional calories for body temperature regulation at approximately 50°F. Add about 2 pounds more hay for every 10-degree temperature drop. With wind and rain at near-freezing temperatures, the feed required increases by approximately 10-15 pounds to 32-47 pounds of hay per day!
Water is critical for digestion. Optimum water temperature for maximum palatability is 45-65°F. Horses tend to consume less if it falls outside this range, making them more prone to poor digestion efficiency, dehydration, and intestinal impactions.
Evaluating your horse’s feed regimen regularly can help reduce stress on his body from inadequate nutrition. When you can’t see your horse’s body condition through the hair or blankets, get your hands on him regularly (at least a couple of times a week). For a horse in good body condition, the back should be level (no crease or ridge), the ribs felt, but not easily seen, fat around tailhead should feel spongy, the withers should be rounded, and the shoulders and neck should blend smoothly into the body.
About the author: Kimberly Peterson, DVM, is an AAEP member and lives in Lexington, Ky.
AAEP Forum article courtesy of The Horse magazine, an AAEP Media Partner.
Reviewed by original author in 2016.