They take a little while to be mature enough to be usable(for me at least). I usually wait about 5-6 weeks from the time they are born. They are usually about the size of small adult mice at this time, maybe a little bigger. More meat on their bones though. I always handle them from birth, as it seems to help them be less spastic when being eaten

If you're ever in Waco, and need another breeding pair, let me know. What are you breeding gerbils for, by the way? Someone bein' picky?