The nice thing with the rat colony is your son will get excellent experience understanding genetics and management of breeding adults that he can carry over to other creatures. It's not the same exactly but the concepts are and it's a much quicker way to learn basic genetics and health (especially of the producing females).

We generally start our females breeding around 4-5 months of age when they've hit 250 grams or thereabouts. Really depends on the particular rat so I just basically eyeball it and know when a female is looking big enough. We retire the females anywhere from 12 to 16 months of age. 12 months is recommended, however, with the good resting and not back to back breeding, we are finding the females are in great condition and breed very nice litters months past the year cut off. I just watch them closely after the 12 month mark and as soon as I see any indication the female is not up to it or a sharp reduction in her litter size...she's retired.

HoneyChild is a good example. She consistently produced 15 per litter, from her first litter. When she was about 15 to 16 months old she produced her last litter of only 6. Very nice rats, in fact we kept a few out of that litter, but a clear indication momma rat was done. I'll have to get a pic of her today, she's in fantastic shape for an older female breeder and going strong having a great life. I don't know if it's because she was such a good momma but she clearly seems to get more out of life being in with the recently weaned rats than in with other mature females. She's highly maternal so I think HC just likes something smaller to cuddle and groom.

Alita, another female, produced 12, 16, 16, and 18 then dropped to 10. We got her as an adult with her age unknown but I suspect she's done now as her last rotation through with a breeder male produced no litter. She's retired and her lovely all black daughter, Jet, has quite nicely filled momma's place in the breeding rotation. I like to keep the best daughter from a good producer as they say good breeding and litter raising skills are somewhat genetic in rats.

Our retired breeder male, Casanova, who is a bit older than HC, hangs out in the male only cage with the younger actively breeding males. We call him "King of the Food Bowl" as every rat in there knows that when we put in the new food, Nova is always first to feed. Any young stud rat who thinks he can get to the treats first gets quickly tossed on it's back, rolled around and scolded by old Nova LOL.

I once tried to count how many feeders Casanova has fathered for us. I stopped after the first few hundred...my brain ached!