At What Age....

Figured this would do better as a poll. I wait until a mouse is at least 12 weeks old before breeding them for the first time, though I've seen other mouse breeders begin breeding at different ages. So when do you begin introducing a male to your female mice? You can also include when you begin breeding a male. (I'm sure this is considerably younger)

8 to 10 weeks and I retire them after 5 litters.

It was always recommended to me to wait until they were 12 weeks old. Is there a reason for this? I retire after 6 litters. Of course that is my rule but I have never had a breeder colony long enough for that.

Like Deborah, I usually wait until they are about 8 to 10 weeks of age to introduce them to the male. I think if you go any earlier than that, you might cause the female more grief than she can take...which in turn could cause her to eat her young. Then again, most new mothers end up eating at least some of their first offspring, or so has been my experience. It took me a few months to get a good, solid colony going, but now they're doing great. I always retire mine after their fifth or sixth litter, which is easy to do as their offspring work great in taking their place. ;)

Forgot to mention that I breed the male as early as 6 weeks, so long as he's capable of doing the job. If it's a smaller male, I might wait another couple of weeks, but usually by that age, they are ready to go.

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Originally Posted by Jay_Bunny

It was always recommended to me to wait until they were 12 weeks old. Is there a reason for this? I retire after 6 litters. Of course that is my rule but I have never had a breeder colony long enough for that.

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Well those are guidelines but I pretty much go my my own guidelines based on what work with my colony.

I have been breeding rats and mice for a few years and have try various thing and 8 to 10 weeks with my colony seems to work perfectly, I have tried younger but they tend to have smaller litters and more prone to cannibalism.

At 8/10 week they average 12 to 16 babies even as first timer :O and they never eat their first litter.

I guess I could wait a little more but let's face it the breeding lifespan of mice is already very short so 8 to 10 is what I go by.

I always do 12 weeks with mice and 16 weeks with rats.

Its only a pain in the butt in the beginning when you are growing up your first breeders. After you have a good rotation in place it doesn't hold you back to wait until they are 12 weeks old.

So, I personally would wait until they are 12 weeks old.

Thanks everyone for your replies. :D

I start breeding females at 28 days. At this point they are sexually mature and will begin to cycle. If you think you are gaining anything by waiting you're not.

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.

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Originally Posted by Jay_Bunny

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.

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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.

I have left females in with their father's colony, so they probably became pregnant the very first time they came in heat. I have seen no negative effects from this. It is possible that their first litters are pretty small, although in a colony situation it is often hard to know how many pinks came from which mom. Also, in this situation, I don't necessarily know how they would do in terms of a long productive life, because the other mice in that colony are already at least 2 litters ahead of them, so when I retire the colony, these females have had a shorter breeding career.

It is much more typical for me to wean the babies at roughly 3 weeks, raise them up for another week or 2, or possibly longer depending on my needs at the moment, and then put them into colonies. The females that are put in colonies at 4 or 5 weeks of age do tend to have slightly small litters for their first litter, but they care for the babies just fine and don't appear to suffer any ill effects. They go on to have long and productive breeding careers without a break until I retire them.

I don't retire my breeders at a certain age, either. I keep records of how many babies I wean from each colony (so any that don't make it that far don't get counted), and when those numbers drop off for 2 cycles in a row, I retire the colony. I have noticed on occasion that a colony will have one cycle with really low numbers, then bounce back and have high numbers again. Based on this observation, I believe that nature provides a way for the females to have a "break" if their bodies need it, by having them produce an exceptionally small litter.

Mice wouldn't be able to breed so young, and cycle so frequently, and be able to get pregnant again so soon after giving birth, if they weren't designed to produce lots of babies over their lifetime. If YOUR mice can't handle it, than I would think it is more likely a problem with either the genetics of your colony, or the diet you are providing, rather than that mice as a species can't handle it.

What does everybody mean by "retire them"

I don't even pay attention to age. I just leave 1 male and 3 females in the same tub. Eventually they will get pregnant and have their litters. I just had a female that was only 5 weeks old get pregnant and give birth to a litter of 9babies. I know she was only 5 weeks old because I purchased her when she was 3 weeks old (right after weaning) as food, but I ended up keeping her because she started to get huge out of nowhere.... lol

You can follow strict guidelines all you want but your basically just making more work for yourself. Male+Female+same cage=babies. It's simple.