# breeding age



## sys15 (Nov 26, 2011)

i thought this was interesting, from a jax husbandry manual.



> Mate mice early. Mate mice when they are six-to-eight weeks old. Younger mice generally breed better than do older
> ones.


http://jaxmice.jax.org/manual/breeding_ ... manual.pdf


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## Seafolly (Mar 13, 2012)

I get the impression that "better" just means more babies are produced in a short amount of time (aka doesn't take long to mate) that actually survive. It doesn't seem as though they're concerned about longevity given what various strains produce. I didn't read it all the way through though. I guess it's not too different from people though, right? As we age it seems to take longer to conceive, generally speaking. And teenage hormones, you know. : P


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## moustress (Sep 25, 2009)

Twelve weeks old at the youngest; 16 weeks is good. I'd breed varieties that tend to obesity at 16 weeks. Four to six months is a very good range for first breeding; a doe should not be bred for the first time past eight months old.

Mousies can produce young as early as six weeks, though it rarely occurs until seven or eight weeks. I separate my young meeces at about four or five weeks, depending on how the boys are looking, and more to the point, how the boys are looking and sniffing after sisters and mom. When the testicles are hanging long and low, visible at the tail set, it's time for the boys to go to bachelor's quarters for sure.


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## Jack Garcia (Oct 9, 2009)

I'm not surprised they'd advocate that for lab mice. Lab mice are small and lightly built, just like wild mice (who also breed very young). Show mice are larger, have wider heads and longer bodies, and are more solidly built so they necessarily have to mature slower. Their ovaries might be ready to have babies at 6 weeks old, but the rest of them isn't done growing yet.

Lab mice are tiny and mature so quickly.


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## sys15 (Nov 26, 2011)

jack, i suspect you are entirely correct regarding the different ages of maturity among differently sized strains of mice. that is a very consistent pattern across domestic mammals. nonetheless, i remain suspicious of traditional husbandry practices not supported by data.


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## Loganberry (Oct 24, 2008)

12 weeks is fine for first breeding a doe but you can go earlier if she's big and you're in a hurry.c12 weeks is early adulthood for a mouse and they tend to be almost full grown or full grown depending on the variety. If a variety is prone to obesity, breed much earlier. I've had does aged 4.5 weeks get pregnant, too often actually, so I'd rewrite that 6 week idea.


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## sys15 (Nov 26, 2011)

very interesting, loganberry. thank you for contributing that.


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## MojoMouse (Apr 20, 2012)

What do you think is the best breeding age range for a doe, sys15?

I'll happily breed a female from 12 weeks onward, and in some cases a week earlier. Our mice are smaller than what the US and the UK have - (we're so far behind in type) - so I think they mature a bit faster than the show type. When I started breeding I was told not to breed a female before 6 months, but I never agreed with that after I started reading about mouse husbandry. I don't generally let a female have more than 2 litters. I've got no evidence to back that up, it's just a practice I follow. The oldest age of a mouse I'll breed is 6 months for a first litter.

Some parts of that manual were quite interesting. There was a lot of Jax advertorial stuff in it though. :lol:


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## sys15 (Nov 26, 2011)

MojoMouse said:


> What do you think is the best breeding age range for a doe, sys15?


i think a wide range of ages are acceptable, depending on one's goals and your colony limitations.


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## Jack Garcia (Oct 9, 2009)

sys15 said:


> jack, i suspect you are entirely correct regarding the different ages of maturity among differently sized strains of mice. that is a very consistent pattern across domestic mammals. nonetheless, i remain suspicious of traditional husbandry practices not supported by data.


I think the data remain un-researched because it is so obvious. Researching how mice mature at different rates would be like researching how many toes they have. All you need to do is look at them.


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## sys15 (Nov 26, 2011)

Jack Garcia said:


> I think the data remain un-researched because it is so obvious. Researching how mice mature at different rates would be like researching how many toes they have. All you need to do is look at them.


the detrimental effects of breeding a 8 week old female vs a 10 week old female vs a 12 week old female are as obvious to you as the number of digits they possess? you'd be doing me a service if you could summarize the data you have on the topic in that case. i myself have not been able to detect those effects, however obvious they might be to you.


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## Jack Garcia (Oct 9, 2009)

Ooops, I should have said that seems like the attitude of the labs who'd be doing the research, not make it seem like my own viewpoint. Sorry.


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