A good balanced raw diet is very good for an old dog.

Feeding raw and some cooked fish and sweet potato helped my 14 yr old bulldog live longer, until cancer got her in the end. Feeding raw to one old dog is not that expensive and it is really much better for them. I fed raw ground venison & bone, and raw ground quail since she could not eat chicken.

I also supplemented with lots of salmon oil and some coconut oil. I did give her some canned jack mackerel and cooked sweet potato which were easy for her to digest. But the raw meat was the bulk of her diet.

You can buy the frozen Nature's Variety raw in most areas and it is a good food. I used the Blue Ridge Beef frozen raw because I can buy it for less than $2 a pound locally.

If you don't want to feed raw, a high quality kibble like Fromm with some canned fish and/or cooked meats is better than just kibble. Older dogs don't need the high protein that is in many foods so you'd want to feed one with is 24% protein or less. Add the oils no matter what diet you feed.

What's he eating now? And how is his health?