Inbreeding

There's been a lot of criticism in the British media lately regarding inbreeding. When I first began looking into breeding I was undecided, but having read the books and listened to more knowledgeable breeders my mind is made up. My view is that it is actually more ethical in the long term to inbreed when coupled with ethical selection. The marvel of inbreeding is in the fact that it uncovers any problem genes, rather than covering them and allowing them to spread through the rat population until they reach the point where they are widespread and come out unexpectedly later.

Doesn’t outcrossing give ‘hybrid vigour’?

Inbreeding is a long term investment. Hybrid vigour is a short term benefit of unrelated matings, possibly accompanied by unexpected problems. Outcrosses, even between two established lines, give a complete lottery. Genes interact in very complicated ways, and you just can’t tell if they will work well together; if temperament issues will arise. I have begun my breeding from unrelated rats but appreciate that if I wish to follow my aim of extending lifespan then I need to inbreed in order to select for the attributes which indicate the capacity for longer life. I have also benefitted from the fact that my foundation rats came from established lines in which many problems had already been weeded out.

There are many illnesses which crop up in our pet rats which have a genetic basis in terms of predisposition, such as mammary lumps, pituitary tumours, kidney failure, hind leg degeneration. Pet shop rats from large suppliers (presumably randomly or semi-randomly paired) are generally more likely to show these problems than carefully selected and inbred rats from a responsible breeder. It’s impossible to breed against the tendency to such diseases without a firm knowledge of the genetic history, which is just not possible with outcrosses, especially from random bred lines.

I don’t expect to never have a litter with problems. But inbreeding gives me to tool to remove these problems from the line, rather than hiding them.

Note: much of this was written from a personal viewpoint. Please feel free to alter it and make it more general if you feel it will improve the article.

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