females and babies

Question
right. me and my partner have two rats. both  females ( sisters in fact) and there about 4-5 months old. There black hooded rats and still very small and dainty. They get on great and rarely scabble, and when they do its only really because one doesnt want to be groomed right at that moment lol. Now, my brother has a year and a hlaf old males brown hooded rat, he's considerably bigger than them but has a nice placid temprement. I wish to breed my female, but my partner doesnt want his bred. What are the right and worngs of going about this as i dont want my little girl to be in danger and i wonder if her sister would help with the pups or would a seperate cage for teh birth be in order as i've heard different things. I'll continue to research but any help would be lovely thank you. x

Answer
Breeding is a bit more complicated than putting two rats together and letting them mate.

I do not recommend breeding a rat that you do not know anything about their history such as mother/father= Grandparents etc...in order to know what type of genetic defects they may carry. There are already too many rats that are cancer ridden, carry genes for heart disease and kidney disease etc...and also there are simply too many rats that die in shelters daily needing to be put to sleep because nobody wants to adopt them. You can have the most wonderful temperament rats in the world, but if they have any genetic defects or there are genetic defects in the line, you will not know about it and create unhealthy rats. If you want more rats you should consider just adopting some homeless young rats.
Your rat may have a genetic defect that may not allow her to lactate which means she wont make milk and her babies will starve. She may be unable to have babies naturally and may require a cesarean section but a qualified vet which can be costly.  The father may also carry genes that could make for unhealthy babies as well. Its just impossible to know. Rats can have up to 21 babies; thats alot of babies. They are fertile at 5 weeks old and the mother is fertile right after giving birth. They go into heat every 5 days for up to 12 hours at a time. That makes for plenty of babies to be made.
Even if you plan on keeping them, they will end up all needing attention from a vet during their lifetime. Are you prepared to care for over 20 rats possibly? Also, if you cannot find homes for them and you cant keep them all, have you even thought of what you would do with them all?

I, however, cannot tell you what to do and it is your personal decision to breed her but I will outline the things that can happen.

Please refer to this website (it is not mine) for more info:

http://www.afrma.org/breeding-ethics.htm