My female killed my male!!

I've also found size to be a big factor. If the male is smaller than the females he's in trouble.

What I've done to avoid that sort of trouble, Larry, when I'm using a new younger male is to put him for his first breeding with a couple of mature females that have breeding experience and have shown themselves to be very good natured. Guess the girls just show him the way LOL but it always works for me with the smaller males/bigger females rat breedings.