Why Won't My Golden Retriever Eat?

Many factors can contribute loss of appetite in dogs like pain, all diseases of digestive tract including esophagus, stomach, intestine, pancreas, and liver, other diseases that can affect kidneys, mouth, eyes, nose, skin, brain, throat etc. Depression and anxiety can also cause anorexia.

Treatment depends upon diagnosis first and can be both supportive and specific.  But finally, your vet can give better suggestion.