In Digest 38 what makes feces black is topic: My turn to talk about black poop. Yes, the black color of poop which is seen following gastric bleeding is due to oxidation of the ferrous iron to ferric iron. You can also see black feces when taking to many iron tablets as well. A similar process is seen when bismuth is oxidized - it also causes black feces (we see this in animals -or-people- taking bismuth subsalicylate - also known as Pepto-Bismol) I you are giving iron supplements to your ferrets and it turns the feces black, you probably should back off. Iron overload may cause iron depostion in a number of tissues, including the liver, resulting in a disease called hemochromatosis. Feeding liver generally will not cause iron overload - it is usually either iron tablets, or in some human cultures, beer fermented in iron pots with high levels of ferrous iron. With kindest regards, Bruce H. Williams, DVM Join the Ferret Health List at http://groups.yahoo.com/group/Ferret-Health-list [Further note: dark green feces can look black. Two FHL members had these excellent suggestions: eiher check it by dilution with water, or put it into a plastic bag, swish it, and look at a light through it.] [Posted in FML issue 3349]