How do horses get enough protein?

We tend to think of protein as coming from animal products - or, say, soy or legumes. Horses eat grass and vegetables - so how do they get enough protein?

The answer is: From the grass. Because horses are designed to digest grass, they get all the nutrients out of it, and grass contains a surprising amount of protein. Domestic horses get the extra protein they need to be athletes from alfalfa hay (which is a legume) and grain. Grass hay can be as much as 17% protein and alfalfa hay, fed to high performers, can go up to 22%.