I have only ever had one cat and she has been on prescription food for years. I recently adopted two brothers that are 14 months old and healthy. I am not sure what to feed them. They were in a shelter and ate a mix of the donated food. I was given a small bag to mix with what I planned to feed them. I have tried science diet regular adult food and one of the boys threw up several times on that. My vet suggested Diamond brand which he is still throwing up some. I am taking him to the vet for a checkup but thought it might just be stress of a new home and new food.