Sonya, thanks for the reply.

Tubs are the freedom breeder rat tubs. I think they are approximately 16L x 12W x 7H. I keep a 1.5 breeding colony in 1 tub and separate the expected moms prior to parturition. Then I add more females to the breeding colony to replace the ones I removed. I believe this was the first litter for each of the two mothers previously mentioned. They didn't look as pregnant as the other (larger) females I have who haven't dropped yet. The 2 females who I thought would drop today are twice the size of the first females, and they still haven't dropped.

I wean rats at 3.5 weeks and then add the mom back to the breeding box. Any idea of how I could improve on this system? Any idea how many new moms I could put in one of these tubs? I'd like to maximize the use of the space as I am limited to 5 birthing boxes.

Thanks,
Anthony-