The calculation is simple, for every negative dd
there are approximately 4-5 positive Dd
, of which 2 are homozygous DD
for the mutation . You have done a great job with your Pedigree software and anyone can anticipate about what might happen and what lines have more problems. With or without DCM test: 2+2=4.
The discovery of a nuclear DNA mutation (deletion of 16 bp, no marker) responsible for DCM in Doberman is a first step, but as already indicated in his presentation Dr. Meurs, the problem is probably more complex (polygenic). I think that early will begin to appear more papers on various aspects of the disease, and blood samples of tested dogs will be very useful.
Genetic background of Dobermann genome shows two disturbing characteristics: significant loss of alleles and intense linkage disequilibrium. As I already indicated in two previous notes, the immune system of the Dobermann is like a sieve full of holes, and breed shows worrying signs of immune deficiency. Last evaluation of impact of inherited disorders on the 50 most popular breeds, placed the Dobermann in the seventh worst place with predisposition to 53 genetic disorders (Asher et al. 2009. Inherited defects in pedigree dogs. Part 1: Disorders related to breed standards. The Veterinary Journal 182, 402–411
Major gene responsible for the disease is discovered, and we can no longer say: "when it is discovered, we'll see”. There will be a group of breeders who will try to continue as if nothing had happened, and now they will say that “there are other genes, that all is not clear..”. There will always be reasons for unreason, but the selection will be made against the mutation, and other selection criteria will be deferred to a secondary level. Reduction of the breeding population can be drastic, because the “market” will quickly select: Who will buy a dog without a test? Who will buy a dog heterozygous defective Dd
, when we do not know what will be affected? What will happen with the homozygote’s DD
? Euthanized? Who will want matting a free female dd
with a heterozygous defective Dd
sire? Not too much. More of the confusion regarding the DCM has been cleared and now dogs without DCM test no longer be suspects, but guilty. Will the judges continue to choose winners as if nothing had happened? Probably, but winner males DD
for the mutation will not very likely to be requested for stud service. By contrast, winner males dd
free for the mutation will be very requested.
The problem is that reduction is not on a “genetically healthy” population, but on a population with a reduced “effective population” (Ne) and a bad genetic background. What will happen to an isolated population with a high inbreed rate is not a secret, and the scientific literature is full of examples that indicate what will happen. The situation of purebred dogs is similar to that of a widely studied model of population genetics in conservation biology: “the island model
” proposed by Wright (1931)
and then uses estimates of Wright's Fst (inbreeding rate) to calculate effective population Ne. I have numeric data about the effective population size Ne for the population of European Dobermann because I have calculated, but I will not give because it is useless. In any case it is very small (far less than 100 dogs). It is certain that the selection against the DCM mutation will cause problems, but the question remains whether many or few problems. Everything depends on how we do things.
Let us now make an estimate of what the baseline situation. Breeding population are distributed as follows:
Most of the current population (average population between 2009 and 2001) are no breeding population, and only 20% is breeding population: 76% are females and only 24% are males. Among males 61% were “top sires” with more than 100 pups produced. It is clearly a biased sire population with a high top sire contribution.
If we project linearly these rates to the current European population, excluding population homozygous DD
for the mutation, we are approximately 2012 breeding females (Dd
), only 354 are free dd
homozygous for the mutation, but only 212 dd
females are in reproductive age (2-8 years). About sires I have spoke before. Otherwise we can not forget that these available reproductive females and males are related by ascendancy: average inbreeding coefficient for the current European Population COI = 10.27 +- 4.55 %. We can not confuse wishes with reality. If this is not the numbers of a future bottleneck, it seems a lot. Selection for conformation, plus character and against DCM mutation? How many dogs? We will have to set priorities, forget the old triumphalism speeches, and adapt to reality. The market is a very severe judge, implacable.
The managing of selection program against DCM need a rational approach, and old ticks about overuse of popular sires can be dramatic in our case. Graphic bellow shows the evolution of effective population versus number of breeding females, for different number of males at breeding.
Obviously biased sex mating determines a several reduction in the effective population Ne. You can also observe that for a little number of reproductive males, effective population Ne is quickly independent of number of breeding females. It's like there are 10, 100 or 5000 females, effective population is the same. If we continue to focus the selection on popular dogs, with this drastic reduction of the population expected, quickly we find more problems. I know you're not kindly of regulations, but do you understand why we should limit the number of litters per male?
You know how I think, but please read the 2008 RSPCA report
(specially Chapter 4 & 5) of a prestigious group of 28 independent scientists: geneticists, animal welfare experts and veterinarians, commissioned by the Royal Society for the Prevention of Cruelty to Animals, and coordinated by the speakers: Professor David Sargan (School of Veterinary Medicine, University of Cambridge) and Professor Nicola Rooney (University of Bristol): “Pedigree dog breeding in the UK: A major welfare concern?
Are all these experts lunatics? Although it may seem a paradox, perhaps now the breed is more in danger than a month ago, when it was revealed the discovery of the mutation for Dobermann DCM. The result will depend a lot on how we handle the situation. Will we learn any day of past mistakes, or our dogs will continue to pay the price?