Garlic is supposed to increase their appetite or something like that so they are easier to get onto prepared foods. Its also good for boosting the immune system, like a natural antibiotic. And yes, its good for carnivores, omnivores and herbivores. I have Garlic Guard (basically super concentrated garlic extract, it almost knocked me out when I first opened it, and I like garlic) that I mix with shrimp and scallops to make food packets for the time being. I'm still searching for some ingredients/recipes. They get those packets once a week. I'm not sure if there's a limit to the amount of garlic you should give them though.
But ya, garlic = good for your lovelies! lol