In breeding! Good or bad?

[kc261]

most laboratories will inbreed a max of 7 generations to get their results. it has been proven that any more after that can cause visual defects to come out. that's how most laboratories create their strains of mice/rats.

Pitoon

Hmm. I don't know about that max of 7 generations. Without knowing where that info came from, my first guess is that if it has any basis in reality, they inbreed for a MINIMUM of 7 generations to get the genetic conformity that they desire.

Here is a link I found recently when looking for info on Swiss Webster mice:

1) H
"a mouse strain selected over 101 generations for high litter size, The H-strain, has a mean (± SD) litter size at birth of 21.5 ± 3.5 pups. University of Norway, Department of Animal Science"

http://forums.kingsnake.com/view.php?id=354683,354683

And here is another link I just found:

The International Committee on Standardized Nomenclature for Mice has ruled that a strain of mice can be considered "inbred" at generation F20 (Committee on Standardized Genetic Nomenclature for Mice, 1989).....(5 paragraphs later)....All of the classical inbred strains (including those in Table 3.2 and many others) have been inbred for at least 60 generations.

http://www.informatics.jax.org/silve...ters/3-2.shtml

OK, so apparently it has been defined since 1989 that mice must be inbred for at least 20 generations before they can even be officially an inbred strain. Also, I didn't quote this part, but they are defining inbreeding as brother-sister crosses. Some of us with rodent colonies are doing that, but also often we might be mating cousins, or half-brother to half-sister, etc. So our inbreeding isn't as intense as what they are doing in labs.

Inbreeding is not inherently dangerous. It does not "cause" defects, visual or otherwise, to spontaneously appear. It will sometimes cause hidden defective genes to show themselves. That's ok. Cull those animals with problems, and by inbreeding you can eliminate those defective genes from your bloodlines. It is important that if you are going to be inbreeding, that you are selective about which animals you hold back as breeders.