# How close together is too close?



## JuniperBerry55 (Feb 19, 2018)

Wasn't sure where to post this so hope this is ok.

I'm new to breeding and currently have 4 female sisters, 1 male and am keeping another 1 female from a litter as well as my sister taking a male from this litter that I will have access to for breeding.

My question is: How closely related should you breed before it causes health issues? I'm trying to plan who I should breed to who but I don't want to end up having to buy heaps of unrelated females and males. What do you guys do? I have space for more females and probably another unrelated male but don't really want to keep more than two males.


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## Cheshire Gleam (Aug 15, 2016)

Breeding very closely related mice is fine as long as you aren't breeding in bad traits or recessives. Such as when I began breeding, I had some mice with bad respiratory systems, they weren't contagious but were sickly, and since then I've bred away from having those issues. Just don't use unhealthy mice to breed with and if you find your line is riddled with problems, then it might be best to scrap it. Introducing outcrosses usually doesn't hurt but depending on if they have bad genetic traits, it could still cause harm unless they're from a reliable source. I've bred over thirty litters (not as much as some :lol with very closely related mice resulting in minimal issues. Breeding in good traits is fine, breeding in bad traits aren't. Also, I've read that you should find an outcross after fifty or so generations, but I'm not sure how much truth that holds.


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## Amtma Mousery (Jan 29, 2015)

Most consistent show breeders utilize multiple studs and does.

There is not a specific answer to your question because it is often dependent upon the mice, how many and what deleterious recessive genes they carry. Each generation gains approximately 9-20 germ-line mutations, with .001-.01 being deleterious or lethal.

When limited to a minimal stock population (such as your situation), breeding a specific coat color is a more realistic pursuit than improving type and size. I suggest you breed whatever mice you think are acceptable. If they have unhealthy pups, then you need to use a different buck and/or doe.

Avoid breeding unhealthy mice and inbreeding sibling to sibling. It is better to inbreed at a slower rate to decrease the genetic bottle-necking. A minimum of 2 or 3 generation difference is best, such as grandparent to grandchild or distant cousins.

Sources:
https://genome.cshlp.org/content/early/ ... 4.full.pdf
https://onlinelibrary.wiley.com/doi/pdf ... .tb02178.x
http://content.csbs.utah.edu/~rogers/an ... ut_sel.pdf


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## JuniperBerry55 (Feb 19, 2018)

Thanks! This was very helpful


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