Selecting for Large Litter Size

I have started breeding and intend to replace less than stellar producers with girls from a mom that consistently produces larger litters. Has anyone here kept records of average litter sizes over an extended period and then kept females from those with larger litters to see just how heritable the trait of having large litters is? So far I've had one girl drop 6, one drop 7 and one drop 11 (to include one stillborn). I have three more girls that should be dropping litters in a couple of weeks and am hoping to get at least 10 from them but I'll have to wait and see. Thanks in advance for any help figuring this out!

I have too many rats (with a lot looking alike ) to obviously be able to track who does what and when, however I keep track of my overall production each week.

When holding back females I always pick them from litters of 14 minimum.

First time moms produce about 12 babies.

A far as my litter sizes at their pick females produce between 14 to 17 babies.

All this did not happen overnight, when I first started the production was poor and it took several lines and selective breeding to achieve this kind of production.

Thanks Deborah. I assume that it will take a few generations but I'd like to at least get to where I get 10 rats per litter. Thanks again!

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Originally Posted by gsarchie

Thanks Deborah. I assume that it will take a few generations but I'd like to at least get to where I get 10 rats per litter. Thanks again!

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Maybe maybe not, when I first started my choices (genetically/quality wise) were limited, I did not know anyone breeding rats so I bought mine from Petco and Petsmart, not ideal but my only choices, I slowly added other animals from other sources and with time and careful selection I managed to get better and better production.

Be selective when holding back and if you can try adding new blood coming from someone with a well established colony.

I holdback only the nicest looking rats of my biggest litters. I actually keep track of my production by tubs and make sure to note any movement of rats. I like to keep a first time mother with a veteran breeder. Right now my average is 12 rats per litter. I have only been breeding for about 9 months now but was able to get quality stock right from the start and occasionally go and pick up a couple more from the same guy.

My average is 12-14. I haven't been able to get more than that yet. :(

Thanks for the further input. I will have to start looking around for someone local that has a well established colony. The one with the litter of 11 came from a local pet store and the two with 6 and 7 came from PetSmart. Looks like I may be feeding those two off and raising a couple of girls from my pet store stock.

I've had a litter with 13.
Another factor is age..breed them at the height of their career, which would be around 4-5 months. They are big enough to support large litters and old enough to know how to handle them.

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Originally Posted by gsarchie

Thanks for the further input. I will have to start looking around for someone local that has a well established colony. The one with the litter of 11 came from a local pet store and the two with 6 and 7 came from PetSmart. Looks like I may be feeding those two off and raising a couple of girls from my pet store stock.

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I suggest waiting for their second litter before you cull. Sometimes new mothers just drop less babies the first time around. And you have to take into account the size of the babies.
I once had a experienced mother, who usually had 12 pup litters , drop a 7 pup litter. These newborn pups were huge though. 3-4x larger than my average sized pink.

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Agree with Nikki. I have had new moms drop 6-8 for their first litters but 12-13 on their second litters. Just make sure they have plenty of recovery time.