Record keeping for breeder rats

I have a small dry erase board for each rack that I track when the male was introduced, when he was removed, when the litter was born, and how many in the litter.

I keep a whiteboard with the general info and an individual record for each of my 'breeding staff'

I keep mine in 1.2 or 1.3 colonies and just write the month I set up a colony on a piece of tape and stick it to the rack or tub. I don't retire at a certain age, but it makes it a lot easier to know which and how many colonies are older so I can watch for production to start dropping off and retire them as I feel its time.