Nothing "just" about it Audrey . I think most of us that breed for feeders are doing it not only because managed correctly, it can be quite cost effective but also because we like knowing the feeders are of higher quality that we can likely find in most pet shop feeder tanks. Rats are also a lot of fun to raise and quite easy to manage. Some of us have a certain color or coat pattern that appeals to us and even though as a feeder it doesn't really matter, it's just nice to raise rats that appeal to you visually I think.

To that end (and I speak only for myself) I usually keep an eye on a variety of pet stores when I'm looking for "new blood" for our rat colony. I also specifically watch our own litters for rat pups that carry certain looks I like or come from a pairing that I want to keep that genetic line going - those pups when weaned don't go to the grow out tubs.

Buying a healthy young rat for a future breeder is pretty much like buying a puppy or kitten - clear eyes, clean ears, dry butt, shiney coat, etc. You look for a young animal in good health from a store that cares for their rodent stock appropriately. Try to buy females only from pet stores that seperate the genders over 5 weeks of age. Recently I picked up a young female rat who it turns out was preggie from the store. Even though she did successfully birth 8 young, since she was far too young to have been bred, her young are on the smallish side for feeders and it was hard to keep weight on her while she was nursing them.

Just basic animal husbandry....healthy parent stock, cared for well, gets you offspring that grow to feeding size more quickly and in top condition. Considering your snake gets all it's nutrition from this one source, the better the quality of your feeder rats, the better for your snake.