Q. When reading about feeding horses, I always see nutritionists refer to a “maintenance diet.” What does this mean, and how do I know whether my horse falls into this category?
A. “Maintenance diet” or “maintenance requirements” are terms we nutritionists use fairly often and are perhaps guilty of using with the assumption that horse owners commonly understand what they mean.
In the Nutrient Guidelines for Horses published in 2007 by the National Research Council (NRC), “maintenance” is defined as a physiologic state that applies to “animals that are not pregnant, lactating, growing, or performing work.” The NRC also states that in the case of energy, “the amount of dietary energy needed to prevent a change in the total energy contained in the body of these animals can be considered the maintenance requirement.” Maintenance requirements exist for all nutrients with known daily requirements.
If your horse isn’t pregnant, lactating, growing, or performing work, then his nutrient requirements are those of a horse with his body weight in a maintenance physiologic state. This would include horses on pasture moving around freely but not undergoing forced work, as well as horses that might be laid up in stalls.
Generally speaking, the horse in pasture, while doing no real work, will be expending more energy and have greater nutrient needs than the horse confined to a box stall. So when the NRC guidelines were revised and published in 2007, its authors adopted three levels of maintenance: minimum, average, and elevated. These help account for the variations that might exist within horses that do no forced work.
It’s important to understand that the NRC doesn’t account for individual variations in requirements that might exist. For this reason, use the NRC minimum and elevated maintenance recommendations only as guidelines. You’ll need to make adjustments both up and down depending on the individual horse.
Also keep in mind that an individual horse’s nutrient requirement might change with the season. A horse that might only need the minimum maintenance requirement for calories in summer might need the recommended calories for elevated maintenance in the winter, when he requires more fuel to keep warm.
In reality, all horses have maintenance nutrient requirements. When we deem additional nutrients necessary to help support growth, lactation, or work, for example, we add these nutrients to the horse’s existing maintenance needs. For example, an 1,100-pound (500-kilogram) horse has an average maintenance calorie requirement of 0.0333 multiplied by the mature body weight of 500 kilograms, which is 16.7 Mcals or digestible energy per day. Similarly, crude protein needs are 1.26 multiplied by mature body weight in kilograms or 630 grams of crude protein.
According to the NRC, this same horse in light work has a digestible energy requirement of 0.0333 multiplied by mature body weight (i.e., the maintenance requirements), which is then multiplied by 1.2. This raises the calorie need to 20 Mcals of digestible energy a day or an increase of 3.3 Mcals over the average maintenance requirement. The maintenance requirements are the foundations we build on when feeding all horses, no matter their physiologic state.
Hopefully this gives you a better grasp of what we mean when nutritionists use the term “maintenance.” As with anything else when it comes to feeding and managing horses, always keep in mind that you should feed horses as individuals, and they might not fit neatly within a given definition.