The main causes of black stools in dogs are: Firstly, feeding of food such as offal, which can usually be changed when the food is stopped. Secondly, the protein content in the food is too high caused by indigestion. Thirdly, bleeding in the upper gastrointestinal tract can also cause black stools. If owners can rule out dietary causes, it is recommended that they take their dog to the hospital for a stool test to check for gastrointestinal bleeding.
