How much protein do horses need, and what happens if they get too much? Also, what exactly is "crude" protein?

Horses at maintenance need about 8 to 10% of their diet to be protein; this will only increase very slightly if exercising but will increase more significantly if breeding, lactating, or growing (up to 16% at times). Feeding excess protein will not create a problem unless the horse has existing kidney problems. High-protein diets will cause a high level of ammonia to be excreted in the urine. If horses have kidney problems and are consuming high levels of protein, it …