I was having trouble breeding my rats. I was doing back scratches; I read some where that was to stimulate the rats. I introduced males in rotations. I have 3 males, and six females. Nothing for a long time. Now I have 41 rats in total, and two more girls that have not popped yet. Just be patience. It will happen as long as your guys are fertile. One of my male was a true albino; even though he liked the bow chicky wow wow. He was shooting nothing but blanks.