I have the same kind of thing here, but for my cat. He can only eat one kind of food without having a UTI, but someone else bought the cat food (Bubba of course! ) so it's taking a bit to clear things up. Especially after I had the vet order the food that he eats and Bub kept feeding the wrong thing.
I met a very dear man here recently. One of those "accidental" things that don't seem to be such an accident later. I was waiting on Bubba to get to this man's business and went inside. The man and I started talking and somehow (?) the talk came around to animals. He was telling me that he feeds about 7 cats outside his business and that he also picks up strays on the road and finds homeless cats in other ways and takes them in. He actually built an addition to his house to make a home for a lot of the cats. He find homes for them but takes care of them in the meantime. I made a donation to him for his efforts - which he tried to refuse - and the other day I realized that I have two partial bags of food that are good food just something I can't use. I really admire him for what he is doing because so many people just don't care. I intend to take him a big bag of litter and maybe some more food soon. (After doing wildlife work where everyone expects you to take in animals and they think that you are getting paid to do that I realize even more how anyone who takes in any kind of animal can use financial help in taking care of them).
Sorry - long winded me!