At What Age....

[Brandon Osborne]

28 days is waaaaay to soon for a female mouse to begin breeding. Sure they are ABLE physically to conceive but that does not mean her body is READY for that kind of task. I mean, technically a 13 year old can conceive, but I bet you her body would not be able to handle it and she'd have all sorts of problems. I say ABSOLUTE minimum is 6 weeks. I have four does that are 6 weeks old tomorrow. They are not as big as their mothers, maybe only 25g at most. To me, they are not ready. I will wait another two weeks and then weigh them again.

You need to get a better strain of mouse then. The mice I used to breed were 25 grams at 4 weeks old. If they are ovulating and breeding, they are ready. I bred mice for 15 years and have friends that have been for 25+ years. Our females were always introduced at 28 days. You will see litters in 21-25 days. Mice and humans are apples and oranges. Keep waiting and limit your production.

If you know EXACTLY what age to breed them, why even ask people their opinion? I know it worked for me for many years, but you absolutely refuse to take my advice. It's not waaaay too early if it's been proven successful for many many years. You say the ABSOLUTE minimun is 6 weeks, I say it's 28 days.