[Jacob-list] Congenital defects

[Jacobflock at aol.com]

I think it is good that shepherds share problem episodes so that the breed 
may be conserved.  Congenital problems are not a new phenomenon nor a shepherd 
or breed stigma.  The committed shepherd will watch the flock and each sheep, 
note problems, search for causes and be willing to share the experience for the 
sake of the breed.  It is our "selfish" gene that says a defect should not be 
seen or reported, buried rather than necopsied.

When Miss Shnickelgruber(sp?) saw her new-born son, she probably said he was 
a beautiful baby ... perfect ... he will be a success!  We look at lambs and 
see cute, a measure of perfection and it will be registered.  But perhaps the 
"perfect" lamb is really 20 years old that reproduced consistent, viable 
offspring that, in turn, reproduce consistent, viable offspring.  Lambs are far more 
a "hope" than a "promise"; they tell us about their parents, not their unborn 
offfspring.

I am not advocating a "know-nothing" approach to the practice of husbandry 
but suggest tempering husbandry instinct with some realities such as "one robin 
does not make a spring", "stars are not only there at night", "the sun doesn't 
rise", "the major contributor to the OED was from an insane asylum" and 
"there'll be days like this".

A single instance of atresia ani may be just that, a single instance of a 
genetic mutatioin caused by anything from the status of the egg or fetus getting 
hit by a neutrino to the ewe being stressed or ingesting skunk urine left in 
the pasture.  

On the other hand, a gene is a predictable protein machine, always doing 
something (like producing copies of itself and the building instructions which get 
passed on) but we don't see gene efffects until the right conditions arise. 
Some effects are apparent at birth (black/white, horns, four cleft hooves and 
plumbing, even viability effects such as getting up, smell and sucking,and even 
congenital defects).  Some other effects such as ticking, stones, even 
parasite resistance or resilience are already there but are not typical lamb 
observations.  All breeds of sheep have positive breed outcomes as well as congenital 
and genetic problems. The Jacob is not that unique. 

Most genetic problems are autosomal recessives (most are non lethal problems, 
some lethal).  Given the penchant for breeding pedigrees that dip deep to the 
imports rather than "unknowns", some genetic problems are results that would 
be expected from the gene puddle of the first 25-30 Jacobs. 

You can create your own gene puddle ...Punnett saquare... like AAxAa where A 
is the "normal anus and run two lines, birth sex is 50/50 and assume that 4/5 
rams are wethered or butchered.  I think you hit a aa with a 90% probability 
by the 4th generation.  You can repeat the breeding and see if it is 
repeatable.

Defects can appear to come from "different" lines. On the one hand a line 
suggests a certain level of inbreeding greater than the general population; don't 
rely on flcok name prefixes for breeding distance; check the pedigree to 
great grandparents... on the other hand, did it ever previously occur in one line 
or the other ... ? 

The severity, frequency and predictability of the problem is rather critical 
and that is why sharing information about congenital and genetic defects is so 
important ... how else does one collect information on defects per 100 
births?  

When a case of otognathia was reported...two more were reported ...  When 
cases of OCD were reported ... more were reported ... and atresia ani, stones, 
adactylly, intersex, jaw misalignments, ... etc.,  So there does exist a catalog 
of some Jacob congenital defects and a very crude measure of incidence.  On 
the other hand some defects are more clearly known; e.g., we did planned 
breeding to produce lysosomal storage problems over two years of breeding known and 
suspected carriers that, since genetics probably works, produced expected 
results. Texas A&^M identified the source(s), but the likelyl enzyme defect was 
not the expected beta galactosidase or the other betas associated with lysosomal 
problems in other breeds.  Perhaps the Jacob is unque!  

Having come full circle, I must remeber that beyond the package of genes, 
management and environment also have an effect on the breed and congenital 
defects; e.g., over feeding and barn confinement are often noted. The task is to 
observe and study a problem, propose a casue, test the cause and proceed with a 
little bit of added knowledge and experience.  Sharing knowledge and experience 
helps the shepherd and the breed. 

Fred Horak

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