Male animals can have a green or yellow discharge from the penis that is called smegma. It is a normal discharge. It should not be excessive and should not smell. Other causes of discharge from the prepuce are infection and trauma. Before his surgery mention your concerns to the veterinarian--they can determine if this discharge is normal or not. If he is sick in any other way--not eating, not drinking, or lethargic--have him examined sooner.
