Beardies derive from a relatively small gene pool and, like all pedigree animals, have an inevitable degree of inbreeding. Founder breeders were often obliged to mate very close relatives such as father and daughter, brother and sister because they simply didnt have much choice. The surprise is that whilst such close matings are relatively rare today the average inbreeding rates are significantly higher than they were in those early eight ten generations.
These days there are several computer programmes that cut out the mathematical challenge and make it possible to find the inbreeding co-efficients basically the degree of inbreeding - for any dog at the touch of a button. Some breeders may baulk at the study of such figures but such Luddite-like attitudes are usually founded in ignorance and a lack of understanding of the benefits the appropriate use of science can bring to pedigree dogs, not only in producing outstanding specimens for the ring but also, and perhaps more importantly, healthy family pets.
Inbreeding is not always easy to identify and it is vital to study pedigrees spanning at least eight generations to gain an accurate analysis. An animal which appears to be outcrossed, with no individual ancestor appearing more than once in a three generation pedigree, may descend from only four animals and therefore be highly inbred. The inbreeding coefficient is an estimate of the percentage of all the variable gene pairs that are homozygous that is identical - due to inheritance from common ancestors. Co-efficients also pinpoint the key ancestors that feature in the inbreeding and give an estimate of the contribution they are likely to have made.
The mating of an otherwise unrelated half brother to half sister will produce an inbreeding co-efficient of 12.5 per cent while a brother-sister or father-daughter mating will give inbreeding co-efficients of 25 per cent. Very few Beardies are produced from such close matings but many have similar and even greater degrees of inbreeding because of the influence of background inbreeding, the intensive use of niece-nephew, uncle-niece and similar matings.
Two of the most influential stud dogs of the seventies and eighties were Ch Ororaâ€™s Frank and Ch Pepperland Lyric John at Potterdale. Both dogs were super Beardies, different in type, but both great dogs. Their lines have combined to produce many of todayâ€™s top winners. Both dogs consistently produced high quality offspring that went on to produce well themselves.
Inbreeding co-efficients for most current stud dogs are very much higher, with figures of more than 20 per cent at generation three rising to more than 27 per cent at generation eight being far from exceptional. Whilst at first glance such dogs might not appear to be particularly inbred they are only as genetically diverse as offspring from father â€“ daughter combinations.
Such breeding can and does produce top class dogs, but breeders need to be aware it is happening so that they are able to make informed choices
These two dogs, and most of their generation, shared a similarity that sets them apart from most of the current leading stud dogs. They were far less inbred.
Frank was from Ch Osmart Bonnie Blue Braid and Ch Willowmean Mignonette at Orora, top ranking dogs and bitches of their day. His co-efficient of inbreeding at generation three was 0.00 per cent, rising to 15.3 per cent at generation eight.
Lyric John was by Wishanger Buttertubs Pass by Quinbury ex Pepperland Pandamonium and more closely bred, His co-efficient of inbreeding at generation three was 0.00 per cent, rising to 23.0 per cent at generation eight.
Just as genes responsible for undesirable characteristics may be bred out by inbreeding, so can genes responsible for undesirable defects be bred in. In the Birman cat, for example, inbreeding co-efficients average at between 40 and 60 per cent and the breed is affected by hereditary conditions including kidney dysfunction and liver shunt. Persians can suffer an inherited defect to the walls of blood vessels, Siamese are susceptible to an inherited disorder causing a blockage to part of the stomach and British Shorthairs are prone to a blood clotting disorder.
In many instances careful selection by breeders can prevent dogs carrying abnormalities being used in the breeding programme and this can substantially reduce the risk of undesirable characteristics being established by inbreeding. Sadly, this is not always possible. The Beardie, for example, is a generally very healthy breed but there does seem to be an increasing incidence of dogs affected by low thyroid problems and diseases of the auto immune system. Such disorders do not usually become evident until the dog has reached middle age, years after the affected individual has been used in a breeding programme.
Laboratory mice are probably amongst the most inbred animals. Scientists have aimed to produce mice that are as genetically identical as possible as this increases their value in experiments. Many such mice are perfectly healthy animals, but they must be kept in sterile environments as their immune systems are unable to cope with the everyday germs which pet and wild mice would shrug off with no ill effect. Extreme inbreeding has severely reduced the diversity of genes needed to ensure an efficient immune response and the laboratory mice can be dangerously compromised by trivial infections that would otherwise be of little concern.
Each dog has 38 pairs of chromosomes plus the x and y chromosomes. Each chromosome carries genes made up from the DNA that is the genetic building brick of inheritance. Each parent contributes one of each pair of chromosomes. When dogs have multiple appearances in a pedigree they will have contributed a correspondingly greater number of their chromosomes and there is an increased chance that any single chromosome pair is identical due to inheritance from this common ancestors. Inbreeding increases the number of identical genes carried by the dog. An inbreeding co-efficient of 10 per cent, for example, indicates the probability that 10,000 of the 100,000 genes on the dogs chromosomes have identical alleles. A co-efficient of 25 per cent indicates that 25,000 of the 100,000 genes will have identical alleles.
There is nothing intrinsically wrong with inbreeding, but breeders must be aware of the risks and benefits of producing stock with high inbreeding co-efficients. The first step must be to become aware of the degree of inbreeding within a particular kennel, especially where that inbreeding is background and not apparent without careful study of the pedigree. The use of inbreeding co-efficients, whether calculated manually or at the touch of a button on a computer, is a vital tool in assessing inbreeding rates and one that merits far greater application in the world of pedigree dogs.
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