Horses' Maintenance Energy Requirements Reviewed

Hard keepers, or horses that fail to maintain body weight despite large amounts of feed, need to be fed according to the high-maintenance energy requirements.

Photo: Alexandra Beckstett, The Horse Managing Editor

To achieve optimal weight management of horses, it is important to determine how much energy (calories) they need per day. All animals need energy to keep their hearts beating, to maintain body temperature, etc. The amount of energy required to maintain normal body functions is considered the basal metabolic rate. This amount of energy is largely related to body size; thus, a pony requires substantially less energy than a Percheron.

The science behind energy requirements in horses is beyond the scope of this article, but Nutrient Requirements of Horses, published by the National Research Council and the National Academy Press, discusses it in detail. The most recent edition (2007) gives energy requirements for three levels; high-maintenance, medium-maintenance, and low-maintenance.

As most horse owners realize, some horses are considerably easier keepers than those that fail to maintain body weight despite large amounts of feed (the “hard keepers”). These hard keepers would therefore need the high-maintenance energy requirements and the easy keepers would need the low requirements.

The requirements discussed herein refer to “maintenance” energy requirements. An animal at maintenance is one that is not gaining or losing weight, is not growing, performing, lactating, or reproducing (pregnant mares, active stallions), and is in a thermo-neutral zone (the range in environmental temperatures where an animal doesn’t have to change its metabolic rate just to maintain body temperature). For example, a horse in a cold environment would need more energy to maintain body temperature than a horse in a more temperate climate. Also, it should be noted that these "maintenance" values are purely estimates and that every horse is different.

Nonetheless, these values provide a guideline for how much energy your horse needs for a given body weight. Feeding to have your horse gain or lose weight will require different energy intakes.

The digestible energy requirements of a horse largely depend on its body weight. The following equation is used to estimate daily digestible energy requirements of a horse:

DE (Mcal per day) = Body weight (in kilograms) x 0.0333

For instance, a 500 kg horse would require 16.65 Mcal/day to maintain body weight, while a 400 kg horse would require 13.32 Mcal/day.

To estimate requirements for easy keepers (low requirements) and hard keepers (high requirements), multiply body weight by 0.0303 or 0.0363, respectively. Therefore, a 500 kg easy keeper would require 15.2 Mcal/day and a hard keeper would require 18.2 Mcal/day.

Energy requirements for horses that are growing, pregnant, lactating, or working will be affected greatly due to the energetic demands of these processes. Such horses, including reproducing stallions, should be managed and fed differently and are beyond the scope of this article. If you need help formulating a diet for these types of horses, please consult an equine nutritionist or your veterinarian for guidance.

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