actually it's very bad to feed a cat of any age with milk (especially the milk that we people usually drink) or tuna fish.
I don't know how people made the stereotypical image of cats loving to consume tuna and/or milk, but PLEASE DON'T FEED THE CAT WITH THESE TWO FOODS BECAUSE THEY WILL CAUSE STOMACH PROBLEMS.
If you don't have catfood, i suggest you feed your cat mainly with meat, mainly chicken, beef, whatever fits your expenses, as long as it is NOT ham, liver, etc. A bit of vegetables such as potatoes, carrots, brocolli etc. are, surprisingly, OK to feed your cat, as long as you control how much you give to it and you actually boil/steam it. Raw meat is good, but just in case of bacterias, i suggest you cook them a little.