Well, I don't breed rats, but I do like Google.

http://www.ratbreeding.com/

http://vets-unleashed.falikshow.com/...atbreeders.asp

http://www.agrogea.com/search/rats.htm

http://www.ahc.umn.edu/rar/breeding.html

Some of those are links on breeding pet rats, but the general info is going to remain the same. The link second from the bottom is a list of other links, so somewhere in all that should be more information than you probably will ever need (I noticed some genetics information on one of the pages. For feeder rats, I don't think most of us would be too worried about trying to breed special color varieties or whathaveyou...).

Hope that helps!