
There is a really interesting article on the above at
http://www.vin.com/proceedings/Proceedings.plx?CID=TUFTSBG2005&PID=10632&Category=1484&O=Generic
I think that many of us recognise the dangers of eliminating valuable breeding stock from the gene pool if they are found to be carriers of a genetic disorder, particularly if that disorder has polygenic inheritance.
Takes a bit of reading, but worth it
Jo and the Casblaidd Flatcoats