Here is a guide on the proper care for feeder rats including breeding information. Feel free to sticky.
Introduction: Rats are intelligent and social animals. They are easy to breed and care for, and make an excellent diet for carnivorous reptiles such as snakes and monitors.
Housing: A single rat needs 2 cubic feet of space. The smallest size for 2 adult rats would be 24X12X24. Because they are good escape artists, the bar spacing for the cage should be no more than 5/8 of an inch, though 1/2 inch is more common. Expecting mothers and baby rats should be kept in glass aquariums so that they can not escape.
Substrate: The cheapest and easiest substrate to use is Yesterday’s News cat litter, or another unscented paper litter. This should be changed weekly.
Diet: Rats are omnivores and can do well on a high-quality lab block or low-fat/low-protein dog food. A good lab block is Harlan Teklad or Native Earth. A good dog food would be Innova Senior. They should not be feed hamster/gerbil seed mixes, or rat/mouse seed mixes, as these are incomplete diets.
Socializing: Rats do best in same-sex groups of 2 or more. For a breeding colony, it is recommended that you have at least 2 unrelated males and 2 unrelated females. You should keep males and females separated until it is time to breed.
Sexing: Rats are easy to sex once they have reached 3-4 weeks of age. Males begin to develop testicles, and females are born with nipples. If you examine the babies when they are born, you can often tell the females because they already have nipples. Babies should be separated by sex by 5 weeks of age in order to prevent inbreeding.
Gestation/Litter Size: Rats gestate for about 21-25 days, and litter size can range from 1 to 20.
Temperature and Humidity: Rats do well at room temperature, and an external heat source is not necessary, however they do tend to overheat, so a hot room is not recommended.
Breeding: Breeding rats is very simple. Put a male in a glass tank or wire cage with an unrelated female for 24-48 hours. The courting and mating ritual will ensue.
Newborn Care: Rats are born blind and hairless and totally helpless. They will nurse from the mother for 5 weeks and slowly develop hair. Their eyes will begin to open around 5-10 days, sometimes earlier. Make sure to keep the fathers separate, as they tend to eat the babies.