Horses, cows, and other animals that walk on tiptoe are called ungulagrades. Plantigrades use toes at the end of the foot to help them balance on two hind limbs. Digitigrades are able to move more quietly and, in general, they can attain faster speeds than plantigrades or ungulagrades. Ungulagrades have relatively long, slender limbs, and they can sustain a high speed for longer periods. The ends of the digits or toes are also modified in each of these species.
People have toenails, cats have claws, and horses have hooves.
Each of these is a modification of basically the same material. The combination of a cat's stealth and claws make it a very good hunter. A horse's hooves are well suited for supporting its body weight while running long distances on rugged, abrasive terrain. These hooves and long, slender legs enable a horse to outdistance a cougar, given enough head start. The extremities of front and hind limbs in four-legged mammals are very similar.