[Jacob-list] Recognition of inbreeding coefficients

[Jacobflock at aol.com]

Fred Horak here.  I think that Thom and Betty have an insight into the Jacob 
gene puddle and the consequences for the breed and flock.  I would like to 
encourage the theme of their conversation.

The "founding" Jacobs which were in the hands of relatively few breeders 
(AMBC records) and a few loose Jacobs that turned up at "sales barns" are the 
gene puddle (as opposed to a gene pool).  The first conservators were widely 
separated by geography and lack a real breeding network.  Consequently, some 
of the early Jacobs have a lot of genes that are "identical by descent"...the 
opposite of genetic diversity.  That is the gene puddle; more Jacobs by count 
but fewer Jacobs by genetic variability.

Some of these early realationships are 12.5% (great grandparent to great 
grand progeny) to 25% (full uncle/aunt to niece or nephew OR half brother to 
half sister). Some of this is by accident of geography and desire to produce 
animals.

Inbreeding is not always apparent unless one looks at the pedigree.  The 
basic tool for this is the flock book or specific breeding records of a 
shepherd.  Inbreeding can sneak up as offspring move to different farms.  
Breeding a pair with different farm names is not a guarantee that the family 
trees on each side are nearly identical.  If a common Jacob name shows up on 
either side of the "family tree" for apparently unrelated Jacobs, they are 
related.  The further removed by generations from the "common ancestors (say 
3 generations), the lower the probability of "same genes" for the offspring. 

The greater the relationship between breeding pairs: the greater the common 
genes and loss of diversity, the greater the chance of moving deleterious 
genes to the offspring (inbreeding depression) or carrying deleterious 
recessive genes to successive generation's offspring.   

Suppose one has two related Jacob rams;  The "problem offspring" gets bonked 
rather than acknowledged; the "good looker" gets registered. The "good 
looker" may have 25% of the "problem offspring"'s genes...and pass them on.  
The flock books are a "genetic bank", not just a "beauty contest".

To conserve the breed these genetic issues should be acknowledged, looked at, 
and shared.  Conservation begins with conversation.

Fred Horak