The National Research Council estimates that the average adult horse in light to moderate work needs this combination of nutrients:

Grasses and grass hays come closest to providing the nutrient mix that matches the average horse’s needs:

Other feeds provide different levels of nutrients. Only a few horses, such as lactating mares and growing youngsters, require the protein concentration in alfalfa hay:

Hardworking horses benefit from the extra energy-producing carbohydrates found in grains, but a diet too rich in grain may not provide enough fiber, which keeps food moving through the horse’s gut.

Source: The 1989 National Research Council Nutrient Requirements of Horses and other sources.

This article is excerpted from “Straight Answers to Feeding Questions” which originally appeared in the October 2000 issue of EQUUS magazine.