I used to breed mice, but were just a big hassle compared to rats. I've been breeding rats for a couple years now as pets and as food. There's really not much to it. I can say mice smell(the males have a musk) and seem more sensitive than the rats. I can honestly say as far as pets go you'll enjoy a rat 100X more than a mouse. They're very intelligent and almost dog-like. Breeding rats or mice, it'd be a good idea to give your females a break from babies every once in awhile. Too many nonstop litters can really take a toll on the female, death could even result. Generally speaking the better they're fed the better they'll breed. Lastly I just want to say breeding rodents especially on a small scale is not as cost effective as they seem, learned this from experience. lol