Re: [PyrNet-L] SAS- Threat to Pyrs?

[Kshoffman@aol.com]

In a message dated 12/17/99 5:55:49 PM Eastern Standard Time, 
janices@jump.net writes:

<< I've got newfs.  I will say one thing.  If you look at a newf pedigree 
 today in general you're not going to see heavy line breeding in it 
 anymore.  I understand they used to do heavy line breeding. <snip>
 Guess what.  That's how SAS usually gets started in there, heavy 
 line breeding, and once it gets in there, well, the rest is 
 history >>

Janice,

How many years ago would you say this "switch" from mostly linebreeding to 
mostly outcrossing in Newfs occurred, and how long has it been known that SAS 
is a problem in the breed?  Is there any evidence yet to indicate that the 
overall frequency of the disease breed-wide has decreased as a result of this 
general change in trend of breeding modality?  Statistically, and from a 
population genetics standpoint, this *should* be the case, especially if the 
defect was originally high in some lines but low to non-existent in others.

Just curious if there are any numbers available in Newfs over the past 
several years that would bear this out.  Also, if most breeders are now 
avoiding close genetic relationships in mates, and as a result are lowering 
the incidence of SAS, it would lend more credence I would *think* to this 
defect being polygenic, at least in Newfs.  Could perhaps be only 2 or 3 
genes involved though.  Of course, this is pure speculation on my part based 
on some other hypothesized 2-4 gene defects that are currently being 
researched, i.e. idiopathic epilepsy in the Belgian Tervuren.

Kelley Hoffman
kshoffman@aol.com