Chestnuts evolved from a third toe
Chestnuts are flat, crusty, and devoid of hair. They are located on horses' legs just above their knees on its front legs and below the hocks on rear legs.
Ergots are located at the bottom of a horses fetlock
Soften the chestnuts with water or baby oil and then use your fingernails to peel off the outer layers.
Zebras and donkeys don't have chestnuts on their legs.