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Re: [RC] Genetic diseases - Ed & Wendy Hauser"...if one DOES judiciously breed a carrier individual (why
is it always the great hue and cry to geld the stallions and ignore the
mares, BTW?)..."
Now this discussion is getting down to the crux of the matter.
1. Does the individual have a unique enough genetic heritage to warrant
breeding on? When we (actually Wendy) started looking for stallions for her
SCID clear mare, we quickly found that there was a large pool of suitable
stallions, with pedigrees that suited Wendy and complemented the mare who
were SCID clear. This eliminated any need to use any untested or positive
Stallion. Wendy could achieve her breeding goals without potentially
breeding on SCID carriers.
2. If a responsible breeder were to own a potential stallion (say a
yearling), the breeder would (obviously) have the colt tested for SCID. If
the result comes back positive, then begins the tough decision.
Is this colt's heritage unique enough that the genes must be preserved?
When I look at the pedigrees of a fair number of stallions (particularly in
color breeds) I can not see any plan in the breeding program. It looks like
horses (who may have been good individuals) were just bred together.
(Everyone, please note that just because I can't see the plan, doesn't mean
the plan does not exist.) I then begin to believe that there is a good
chance that even very superior individuals will produce a variety of
offspring, many of whom will not resemble their sire (or dam). We can all
think of great Arabian stallions who were bred to any mare that came along
and thus now have decedents who vary from superior to rotten. I have
noticed an apparent increase in close breeding of performance QH during the
last 20 years. This is a good thing, but in addition to multiplying the
good points of the line it of course makes their faults much more prevalent.
Is this colt's performance potential that outstanding that he must breed on?
(i.e. does he have the potential of producing world cup winners?)
Is this colt's conformation extremely good?
I would bet that in almost all cases, given the numbers of Arabian (or QH
when genetic testing becomes available) horses in the US, if one were
objective, this colt would not be in say the top 10% in all these categories
and thus should be gelded. To be fair one would do the same evaluation of a
filly, and choose not to breed her on the same basis. There are also some
"preservation breeders" of relatively rare lines Arabian horses. Their
breeding programs need to be much closer to the breeding of rare breeds of
horses.
3. The decision would be much harder if the genetics were unique. This
reads on the rare dogs in a previous post, and in the horse world relates to
horses of the rare breeds (Kigers, Akl Tekes, etc. {by the way I DO NOT
have any information or suspicion that these breeds have specific problems
with any particular bad or lethal recessive genes whether testable or
not.}). In this case all breeders are preservation breeders, and would
have to carefully weigh the pros and cons of each mating. They will,of
course, look for clear offspring as preferred sires and dams of the next
generation. I have read a bit about the breeding practices of early Arabian
breeders in the USA. The stories of these programs, with their intensive
close breeding of the few outstanding individuals, are very instructive as
to how to properly run a breeding program. If I remember correctly, Bazy
once imported a stallion that was rumored to have produced what is now known
as an SCID foal. She advertised nationally and bred him to about 20 mares
who had produced SCID foals. She got almost half SCID foals. She
immediately gelded him because she did not want to breed this fault on in
her herd. Note that this was all done before the advent of testing. If
this were to happen today, I'll bet that she would have bred him on, and
tested his offspring, removing the positives and breeding on only his get
who were clear. In her case she could breed multiple times to the right
mares and then only select the absolute best to remain in her program. How
many of us have the money and time to do that?
Ed
Ed & Wendy Hauser
2994 Mittower Road
Victor, MT 59875
ranch@xxxxxxxxxxx
406.642.6490
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