Women/females normally get bigger after giving birth...add to the fact the limited available activity given in this situation, and them getting bigger/fatter is inevitable.

IBuild more of the concrete tub racks....

use some space for grow out racks...

optimum production would be to cycle your breeders out at 8-12 months old as larges, some of the grow outs ate 3-4 months as mediums and the rest as needed.

I don't understand the logic of trying to be "humane" to these animals since you are doing nothing that doesn't come naturally (they naturally will breed back to back in a wild colony situation, hence the expression "breeding like rats.") and unless you are starving them or making them live captive in their own refuse...you are being humane. Ultimately they animals will be killed one way or another to feed another. I can't figure any form of dying is fun or happy.

back on topic.....

1.4 is ideal in the concrete tub...you can swing 1.5 but fighting sometimes occurs from crowding....

at 1.4 or bigger, keep a close eye on weaning....you will be producing a high rate of animals per tub, so older rats will bully out younger ones for milk. So once their eyes are open, move them to allow new pinks to be able to feed.


pinky mice....I run 1.8 in the litter pan racks. no issues if they have constant access to food and water. Mice will kill their young quickly if they feel they can not support them.

I supply pet shops, individuals and myself...when you become a supplier....you worry more about production, sizes, and quality than you do pet life qualities....

they need to be fed, watered, not bullied and not live in soiled conditions that will cause them harm.


also if you supply someone....any escapees are contaminated...

if you want to feed them to your own private stuff...fine....but they never re-enter a colony nor do they go to your customers. Great way to bring in poisons, mites/fleas etc...