Reconstituting a Breed
Reconstituting a Breed
by Dr. Hellmuth Wachtel From time to time the question
has been asked: Have any studies been done to show that genetic problems
are increasing? I do not believe that any one
has even tried to answer this question. I think nobody can, as there are
no statistical observations from bygone times, nor appreciable new ones
( we know more or less *what* defects there are, but rarely the
*incidence*). But simple scientific reasoning
says it can't be otherwise: breeds were created from relative few
individuals of a population, so they passed on *few* defects but these
to the whole offspring generation. Elite breeding and standard selection
made few males eligible for breeding in each new generation thus
steadily thinning out what genetic heritage was still left, but
accumulating defect genes. Long time, hard natural selection (absence of
vaccinations and advanced vet care, often scrap feeding, etc.) helped
keep up sound genetic combinations in spite of inbreeding effects by
incest matings, line breeding and favorite sires. Today, sophisticated feeding,
general care and veterinary advancement allows to continue breeding dogs
with high inbreeding coefficients and defect incidence, if at
considerable costs and emotions. Theoretically, the persistent
inbreeding regime should have purged a lot of defects, but obviously not
or by far not enough so. In addition, new defect mutations seem to pop
up in higher proportions than geneticists would think. These in turn are
readily multiplied by more favorite sire use etc. in the successive
generations. So, how can a highly beset
breed be reconstituted? In my opinion, only by a lot of idealism,
co-operation, trustfulness and discipline. People must find agreement
that they can't go on in this way, their beloved breed must be helped by
common effort. They must unite, world-wide if possible, make a genetic
breed analysis (pedigree and DNA), find out which "families" are most
riddled with defects, which dogs show highest heterozygosity, which
combinations are genetically most distant. Then a plan must be made,
using a combination of least-kinship matings and avoidance of dogs from
"infected" families *1(e.g. by means of BLUP), thus gradually decreasing
the mean inbreeding coefficient in every generation, and severely limit
the use of individual sires, in other words increasing the number of
sires per generation, taking care to achieve a minimum *2effective
genetic population size of 200. In that way, both defect
incidence and inbreeding depression could be efficiently tackled,
provided the breed is sufficient numerous and general background
inbreeding level not too high. Otherwise only a crossbreeding scheme
could help but not by crossing breeds as distinct like setters and sight
hounds but e.g. Irish with Gordon Setters or even with LGPs or French
épagneuls. In this way, much of the
original vitality could be recuperated. Utopian ? Maybe, but realistic.
Only by using both tools, defect screening and population genetics the
goal can be achieved. A breed's future requires vet care, genetic
hygiene, health selection, and defect control, all of them, not patch
work. I think the target could be achieved in ten years. There could be
setbacks, of course, for bad surprises may come up but should not
discourage. The German Landseer action I mentioned AFAIK is the (so far
only) tangible proof. BTW, the best thing would be to abstain from
showing with kennel clubs during the "genetic quarantine" (or for good).
A well revitalised breed may be demanded just by the health bonus (if
conformation is maintained). Dr. Hellmuth Wachtel Free collaborator of the
Austrian Kennel Club - Member of the Scientific Council of the Vienna
Schoenbrunn Zoo *1 BLUP -Hmm.., sorry, a
thorough explanation would take a lot of time. BLUP is a mathematical
method to find out which dogs are more or less liable to develop
defects, eg. HD, based on kin data, and the dogs with lower than average
index are to be bred as concerns HD (or other defect/traits if so
adapted.) It was successful eg. dealing with HD in Hovawarths in
Germany. *2 Effective genetic population
size means a computed value indicating the genetic loss of a breed by
genetic drift per generation that is always smaller than the actual
breeding population. It depends mainly on the relatedness within the
breed (eg. one sire for (theoretical) thousand bitches would produce an
offspring generation with an effective population of 4!! Real
population: effective population size = 1001 :4) This illustrates how
favourite sire use is a kind of genetic genocide :-(. (If the effective
size is too small, inbreeding problems arise even without actual
inbreeding, because the breed gets more related in every generation.) As far as I know, pedigree
programs mostly do not compute effective size, I know of one called
Optimate of the Hanover Vet College in Germany that does it. It is
destined for endangered domestic animal breeds, they tell me it is used
for some dog breeds in Germany. A size of 200 is the level that allows a
breed to survive (provided it is not further inbred and sufficient sires
are used to maintain the 200 level.) Dr. Hellmuth Wachtel
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