How to place the rats when breeding...

Hello,

I was looking up information on how to breed rats and it said to place the rats male and female in a tank over night and then put them back. Is okay if the rats are living together? Because i have two rats and they are both living together and I am trying to get them to have babies. Once they have babies and they grow up I will start to raise many rats to breed, and I wanted to know also if I should be placing one male with a bunch of females. And is there a good chance that most of the females will get pregnant? Or should I do one by one in separate cages? Why do people separate the rats after a few hours? Is it just to keep track of how long the female was pregnant for? :confused:

I have the male's with the female's all the time , I only take the male's out when the females are about to give birth. I then wait til about a week before weaning the little ones to reintroduce a male.