The kidney is a pair of bean-shaped organs that form and excrete urine, regulate fluid and electrolyte balance, and act as endocrine glands. If the organ is listed on the label without origin of animal (e.g.: kidney instead of beef kidney), be cautious as there is no way to know which kind of animal it came from. It could be from a horse, goat, duck, pig or even skunk or other animals of questionable origin. We recommend that kidney, as with any organs, be used in the proper quantities (up to 5-10% of the diet) and come from a source where the animal has not been given any antibiotics/hormones.