Here's my advice, and I've been breeding at least 2000 rats for at least 3 years now.

You should ALWAYS separate each female if possible (tubs permitting) and their litter so other females don't fight over the babies. Your yield will be much higher than putting mulitple females together at once. Cat litter pans are the best for maternity racks. If you are going to house multiple females together make sure that they don't fight over the babies and if you catch them fighting over them separate the moms that were fighting and leave the rest.

You should NEVER feed dog food or swine food to a rat. It's not designed for them. Yes it can save you money, but the money you save you will most definitely spend in rats replacing the ones you kill feeding it.

You should retire females after about 6-8 months of breeding. Eventually their litter size will drop below 8 and they are worhtless at that point.

A good ratio is 1.8 per week.

You should clean your rats AT LEAST once a week. Healthy rats = Healthy snakes.

Contrary to popular belief you can house 2 males together in a tub of females, they just have to have been raised their entire lives together otherwise they'll fight. But we do it all the time with semi-lazy breeders.

If you ever find a chewer. Euthenise it immediately. It will not only chew tubs, but teach the other rats how to chew. So it's in your best interest to get rid of any chewers as soon as they are found.

You can also use flax seed to get rid of tumors in rats (just have a strong stomach). After a couple weeks of tossing flax up there when you feed you'll notice that the tumors begin to fester and puss. But eventually they will just fall off and the wound will close. It's best to separate rats that have festering tumors and best to keep them on something like equine pine that stays dryer longer.

This is my advice. You can take it for what it's worth. I produce somwhere between 100-400 rats per week give or take depending on the time of year (dead of winter and heat of summer are the slowest times).