Many veterinarians recommend supplementing dogs with liver disease with compounds such as s-adenosylmethionine (SAMe), vitamin E, or milk thistle. While there are no data to support their use specifically in copper-associated liver disease, benefits have been shown in some studies of other types of liver damage, such as from chemotherapy drugs and liver toxins. High quality products containing SAMe or milk thistle (silymarin) or both appear to be safe and are unlikely to cause harm; but quality control of dietary supplements can be questionnable, so finding a good quality brand is critical. Your veterinarian can help you find a reliable source for SAMe, vitamin E and milk thistle.
Zinc is another supplement that is frequently used in dogs with copper-associated liver disease. Zinc may reduce absorption of copper from food in the gastrointestinal tract, although how effective it really is remains unclear. It appears to be safe at commonly recommended doses, but can cause gastrointestinal upset in some dogs. Do not give zinc supplementation without talking to your veterinarian first to determine the right dose and if it’s the right option for your pet. https://vetnutrition.tufts.edu/2017/10/copper-associated-liver-disease-in-dogs/