Pro-Combo #3 is an important combination of nutrients that the body needs for the kidneys to function properly. One of the kidneys function is to keep the electrolyte level in balance. PC #3 gives the horse rhythmic, well coordinated movements by transmitting the right impulses from nerves to muscles. One of the first visible symptom of urinary tract disturbance is when the horse lagg its left hind leg, get inflammations in the flexor tendons and back stiffness.