NO! Ferrets cannot drink milk. Milk is not a part of a ferret's natural diet and can cause digestive upset. Ferrets are obligate carnivores, which means that their bodies are designed to digest and use only animal-based proteins. Fish is a good source of protein for ferrets, but it must be cooked before feeding. Raw fish can contain harmful bacteria that can make your ferret sick. Cooked, deboned fish is a safe and healthy treat for your ferret.