Causes for dogs to poop green:

1. Eating too many green vegetables

Dogs poop green but it is formed. It could be that your dog is eating too many green vegetables. Dogs generally poop the same color as the food they eat.

2. Bloating

If your dog has green but formed poop, it may be because the dog has not eaten a certain amount recently. If you eat too much food and it cannot be digested, it will accumulate and cause bloating. Too much oxygen in the dog's stomach will cause it to be reduced to bilirubin and then oxidized to biliverdin, which will cause the feces excreted to be green.

3. Biliary dysfunction

If your dog poops green but becomes constipated, it may be that there is a problem with the dog’s bile function. The gallbladder is an important organ as it determines the color of your poop. When bile is secreted to digest food in the intestines, bilirubin and biliverdin are formed. Bilirubin is yellow when visible to the naked eye. The color of normal stool is mostly caused by bilirubin, and biliverdin is green. If the pigment is abnormal, the stool will be green.

4. Colitis

If your dog poops green but is formed, it may be that the dog has colitis. Colitis will cause biliverdin to be unable to be restored normally, so the dog's poop will be green.