I was meaning it as if you already had cat food..as I do..I could try it to them.I've never tried feeding the chickens cat food although I know others do.
I try to avoid feeding them anything that may contain additives and preservatives so I suppose it depends on what's in the cat food.
Also, cat food and the vitamin drinks tend to be expensive.
I would try plain cooked fish and mix it in with their normal feed.
Cooked fish mixed to their feed unfortunatel didnt work for mine