| Subject: Re: INBREEDING AND PEDIGREE DOGS |
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Date Posted: 18:24:42 08/27/09 Thu
In reply to:
from longwoods by dr
's message, "INBREEDING AND PEDIGREE DOGS" on 16:33:01 08/27/09 Thu
Re(1): INBREEDING AND PEDIGREE DOG BREEDS - article
Posted on August 24, 2009 at 19:04:41 by Tracey
Breed development
A breed is a collection of animals that are related, stem from a specific origin and have various features in common. In the development of breeds there was a distinct tendency to inbreed so as to try to fix various attributes, mainly of phenotypic importance. When Longhorn cattle were the norm the development of the Shorthorn was enhanced by making it not only shorter in horn length but of different colour and shape with different attributes. In the development of the Orlov Trotter in Russia in the late eighteenth century inbreeding was rife and Kelley (1946) gives a pedigree of Lubensoi 111 which has an inbreeding coefficient of over 64% inside 7 generations, higher than any dog pedigree I have seen outside of colonies bred for research and thus not "real dogs".
Breeds of dog have been selected in many instances for specific roles. These may vary from being a lap dog through to all manner of work and companion animal status. Without a herding dog (Border Collie, Kelpie etc) a sheep farmer would be highly handicaped in European/American situations. In USA the role of livestock protection dogs (Maremma, Anatolian etc) is such that without them sheep farming would be impossible in some locations because of predator attack. But the traits that are found in a herder are not those found in a livestock protection dog. One dog cannot thus replace the other and both types are needed. This must not be lost sight of. Dogs have a specific purpose and are needed for that purpose even if it is merely as a companion to an old-age pensioner living alone.
The GSD is the police dog par excellence. British police forces have tried Rottweilers, Dobermanns, Bouvier des Flandres and Mallinois among others but for general police work the GSD is the dog that still wins over the others, even though few police forces breed their own dogs and they are thus dependent upon breeders who did not set out to breed police dogs.
Breeds not only aid man in working situations but they also undertake such tasks as being the eyes for those who cannot see. Dogs like Labradors and Golden retrievers, developed originally as gundogs, now have little or no opportunity to do this sort of work but they have developed other attributes such as guide dogs for the blind. This shows a tremendous versatility and ability to adapt yet some advisors to governments seem to want to be rid of the purebred dog. If crossbreeds and mongrels were the ideal then why have they not been used? Twenty years ago I visited South Africa where the police were crossing Bloodhounds and Rottweilers/Dobermanns for working purposes. I went back to SA a few years ago and the crossbred animals were a tiny minority with GSD of excellent police ability dominating the force's dogs.
Crossbreeding has a useful purpose in Beef, Sheep and Pig production and no agricultural scientist would argue with the wisdom of such an action. Indeed in such species the concept of pure breeds is almost redundant. But world wide modern dairy cattle are almost all black-and-white descendents of Dutch Holstein-Friesians and breeds like Jerseys, Guernseys and Ayrshires are almost gone. When I was a university student in the early 1950s the Dairy Shorthorn was the breed of choice in Britain but it is now a rarity. This did not come about by pressure from scientist but the fact that for the circumstances of the day the Holstein-Friesian outclasses all others. Crossbreeding is not undertaken in most dairy herds because the Holstein is so far ahead of the other breeds that crossing it would be a retrograde step. However inbreeding is hardly a problem even though many small bottlenecks have occured over history.
Various organisations around the world are intent on retaining rare pure breeds of farm livestock species in the knowledge (hope?) that one day they or their attributes may be needed. Such bodies are aware of inbreeding risks but they are intent on retaining the purity of race. In contrast canine breeds in Holland are threatened with political interference under the guise of preserving them but by imposing so many restrictions that they are taking away the role of the breeder and bringing in draconian rules even in breeds that are numerically large. I do not have Dutch registrations figures but in the UK we register about 20,000 GSD annually and the average lifespan is 10 years. That means that we have about 200,000 GSD in Britain at any one time. That is not a population at risk. In contrast we register 800 BMD with a lifespan of 7 years. Our population at any one time is thus 5,600 which is hardly risk making. Breeds that can amass a mere 100 individuals may have problems but we should deal with these according to their needs and not apply the same rules to major breeds with numerical strength.
Few canine breed studies on inbreeding have been undertaken but McCarthy and Blennerhasset (1972) made a study of a small sample of racing greyhounds in Eire and found an inbreeding coefficient of less than 1% per generation or less than 0.22% per year. Since man is permitted to marry a first cousin, leading to an inbreeding in any progeny of 6.25% the racing greyhound is hardly at risk from inbreeding. Indeed studies on most numerically large breeds would show that inbreeding over five generations would generally be around the 3-4% mark. My own analysis (Willis, 1989) of 276 Boxer champions in Britain showed a mean value of 4.2% with over half the animals being <1%. Extending pedigrees would increase these values slightly but breeders have no means of doing this. In his study of Seeing Eye dogs in America Pfaffenberger (1963) showed that inbreeding to the dog Frank of Ledge Acres increased the chance of successful guide dogs. It is true that Rehfeld (1970) in a beagle colony showed an increase in noenatal death with increasing inbreeding but he was operating at levels up to 78% , far higher than those seen in pedigree dogs.
Ubbink et al (1992) showed a highish level of inbreeding (median 6.4% to 12.5%) in Bouvier des Flandres in Holland and levels were slightly higher in some dogs with specific defects but not for all defects and the population was not large.
Nobody would dispute the fact that high levels of inbreeding can be damaging but in some cases the effect of inbreeding is not apparent at less than 20% (brother/sister and parent/offspring is 25%). Having said this the Chillingham Wild White Cattle herd, some 50 miles from where I live, has survived in genetic isolation under a king bull system for around 300 years and is still going strong but is numerically small (about 40 cows). In other words the high inbreeding coefficient on paper is not reflected in the realities on the ground.
In White Park Cattle in 1991 the effective population size was 79 and Alderson( 1992) argued that more than 15% of the variability could be lost in the next 50 generations. This is over a period of at least 250 years during which time Dr Alderson and the rest of us will no longer be involved! I do not think we can seriously hope to plan a breeding programme for 250 years ahead, nor should we try, however hungry we are for power and influence.
The idea that increased inbreeding will increase the incidence of defects is unlikely (Alderson & Bodo, 1992) if the defect has a high frequency. For example the long coat (an aesthetic defect in GSD) has an incidence to the extent that about 10% of GSD are born long-coated which means that about half the normal coated dogs are carriers and half are free of the allele. Nothing much is done or needs to be done because some owners like long coats and they have minimal biological disadvantage. Alderson & Bodo(1992) argue that inbreeding has not detracted from conservation programmes even when some animals have reached 20% inbreeding.
Let me close this section by referring to the eminent geneticist, the late Prof J.L.Lush of Iowa State, a world authority in the field of genetics. In his classic book Animal Breeding Plans (1945) he states " It seems reasonably certain that more opportunities for breed progress are lost by not inbreeding when inbreeding would be advisable than are lost by too much inbreeding." Some of the advisors to the Dutch KC, by no means in the class of Lush, would do well to re-read this classic book, dated though it is.
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