GENETICS

The Genetic Impoverishment of the Azawakh Breed

Written by Elisabeth Naumann
Translated by Nicole Holland

Picture text: (Shortened text taken from a presentation held at the Azawakh meeting in DWZRV on 25th of January 2003.)

There was an outcry within the Azawakh community during the summer of 2002. Some of the committee members of the French SLAG had suggested improving the breed by selectively cross breeding the Azawakh with the Sloughi. The genetic pool of Azawakh was said to be too small in Europe. Are those worries founded? What are the reasons? And what is there to be done (if at all necessary)? Before I deal with the questions above, let me first explain, as simply as possible, some of the very basics of biogenetics

The cell - the foundation material

The cell consists of cell body and cell nucleus. The latter is a carrier of genetic information material. It contains kernel threads or chromosomes, which always exist in pairs. The dog has 78 chromosomes, therefore 39 chromosome pairs

The hereditary material is divided into units. They are called microsatellites and are genetic mark stones. The dog possesses 50.000 of those microsatellites. Each microsatellite has its own special place on the chromosome and this varies from dog to dog. The closer two dogs are related to one another the more similar will their microsatellites be.

Picture 1: Homozygous allele pair - Heterozygous allele pair

Genes - the carrier of genetic information

The smallest units of genetic information are genes. Chromosomes do not exist individually, they are always made up of pairs - homozygous- each gene belonging to another partner-gene or homozygous gene (allele).

We assume that dogs have more than 100.000 allele pairs, and therefore 200.000 genes. The section where two alleles are located on one chromosome is called gene location (gene locus). A specific gene can always be found in the same location on a chromosome. And this specific gene will always influence one specific characteristic/trait and only ever this one. One chromosome from a chromosome pair stems from the father and the other from the mother. The male and the female dog contribute each half of the genes.

One allele can suppress another one, which affects the hereditary result. If such an allele occupies a mixed hereditary gene location, the weaker allele will be suppressed and the stronger, more dominant gene determines the phenotype. Those genes, which cannot push through are called recessive genes.

Recessive traits/characteristics can only be seen in the descendants of mixed hereditary dogs, if their carrier in one animal is pure hereditary. This means that those genes are located in pairs at the same gene location. This fact plays a vital role when we look at hereditary defects, as quite a number of those are inherited recessively. If an allele pair contains the same genetic information the dog is considered for this specific trait homozygous. Should the alleles for this characteristic be different, the dog is then considered for this trait heterozygous. The genetic make-up of a dog is in parts pure hereditary (homozygous) and in other parts mixed hereditary (heterozygous). Dogs where all traits and characteristics are homozygous do not exist.

In accordance with genetics

When we look at the effects of hereditary factors, we can differentiate between the following possibilities:

1.) One gene influences one trait.
2.) One gene influences more than one trait.
3.) A number of genes influence the shaping of a trait, in this case we speak of a polygenetic hereditary make-up, polygenetic or multifactor genetics.

Usually not only one specific gene is responsible for certain traits or characteristics, but it is the combination of a number of different genes. Such a polygenetic hereditary make-up is the basis of nearly all quantitative traits and characteristics. The later could be the height, weight and the degree of back legs, performance - and natural characteristics.

Qualitative characteristics are fur and fur color.

Additive genes can only be determined in appearance if they fulfill a certain minimum number (threshold). Such threshold effects can also be seen when dealing with hereditary defects. Some defects are changes (mutations) of healthy genes, which were passed on recessively. Often they stay hidden for generations. Matching two mutations will bring this phenomenon to light.

Table:
Heredity degree of different characteristics in percentages
(taken from Hansen, Vererbung am Hund, 2001)

The heredity is the influence of the phenotype through the genetic type. This can vary between 0 - 100%. Hardly any characteristic is hereditary 100% (please also compare Claude Gaillard, Der Zuchtwart, in: Rassehund, December 2002).

Selective breeding is the way to enhance or suppress traits and characteristics. The seemingly easy rule in breeding tells us that only those individuals should be bred with, which combine the favorable traits and characteristics in a breed and which come as close as possible to fulfilling the breeds standards. Of course there will always be questions on how sensible a breed standard really is and who should determine a breed development.



this Azawakh male displays in his native country the typical characteristics of a desired build such as a broad front, strong front legs, lower line in ship… form, prominent head, strong lower jaws. These characteristics are because of their high grade of heredity very easily lost in their phenotype due to tight breeding methods.


Azawakh skull (Beliregion, Westafrica), strong teeth and well-developed lower jaw are part of the "survival equipment" in the native country of the Azawakh.

Usually breeders have a vast pool of non-related breeding individuals to choose from. This is especially important when genetic mistakes show within a homozygous selection and therefore need to be corrected. These possibilities can only be applied to the Azawakh breed, due to its fewer and more limited numbers, to a certain extent. Selection always means genetic changes and losses. Selective and repeated selection changes the frequency of occurrence of specific genes within the whole breeding population.

When deciding upon genetic losses one has to look closely at the breeding animal and also seek help through inbreeding coefficients and ancestral loss coefficients. The inbreeding coefficient determines by which percentage the heterozygous has decreased and the homozygous has increased within a dog comparable to the breeding average. The formula of calculation by weight of the inbreeding coefficients (IK) reads as follows: IK=(1/2)n1+n2+1.

The ancestral loss coefficients (AVK) (formula designed by Prof. Schlegel, University of Vienna) are the quotient out of a number of uniquely found ancestors within the overall group of ancestors.

Example: Within a group of the third still know generation are only eight out of 14 ancestors different individuals, then the quotient for this group will be 8:14=0,55. This means an ancestral loss of 55 percent .An AVK of 60 for example means a loss of heterozygous of 40%.

Going back to the question from the beginning " The genetic impoverishment of the Azawakh breed?" I have analyzed the European stock (about 900 individuals between 1999 to 2001) with taking the IK and AVK into account. In order to gain an annual average figure, all documented individuals were given their IK and AVK. These figures were then added and divided by the figure of entries.

The result shows a steady decline of the AVK figure for the Azawakh population in France. Towards the end of the 1990's the AVK has sunk under the genetic threshold of 70 percent. In accordance to this development the inbreeding coefficient increased over its critical figure of 20 percent. There is the serious development of the so called "bottle neck effect" to be witnessed where we went from the initial wide genetic range of the Azawakh imports out of colonial Africa to a situation which is not correctable by the dramatic narrowing of the genetic material of the current French breeding.


Graphic 2: IK - and AVK distribution on the example of the French breeding


Graphic3: IK - and AVK distribution on the example of German breeding

The German breeding started in the 1970's in quite a similar situation in which the French population is currently. Due to the incorporation of Azawakh's from France and imports from Africa, the German breeding seems to be much safer and increasing since the 1990's. Obviously there can be a discrepancy of this statistical average between different breeders and bloodlines (please see graphic 4 - 6).

Homozygous is considered within normal breeding activity of pets as the key to optimizing a breed. Inbreeding means to make dogs and their genetic material homozygous. The bigger the IK, the bigger the possibility that descendants will be homozygous in certain genes. There is obviously an open question on which genes will be homozygous by such breeding - the favorable ones or also the unfavorable genes. To act like this within a breed which is already few in numbers and genetically limited could have serious consequences, namely the collapse of the breed as a whole. Recessive genes in mostly polygenetic heredity often determine genetic errors. The most undesired characteristics or traits, which occur within a homozygous bloodline, are hereditary mistakes. Only descendants of breeding individuals, who carry the recessive hereditary genetically faulty homozygous material, show this in their phenotype. That is the reason why a characteristic, which, through inbreeding, should have been strengthened, is coupled with a faulty characteristic, which is undesirable. Or it is the other way around- the genes which are non - desirable and which one wishes to eliminate through inbreeding are coupled with a gene which is most desirable. In a small kennel the advantages and disadvantages come very quickly to light.

By rebuilding a new breeding population, inbreeding can very quickly manifest itself (often arbitrarily) in breed characteristics defined by breeders and the kennel clubs. If further inbreeding takes place more disadvantages will show, this can be described with the term of inbreeding depression.

Negative results with inbreeding do not occur overnight, nor do they show in a multitude or all at the same time. Some bloodlines seem to have a higher level of inbreeding tolerance than others, before negative effects do show. Even in very tight bloodline breeding with relatively high IK and AVK, genetic mistakes can stay hidden over a long period of time. They can, through genetic luck, stay within certain limitations or only show certain physical or psychological characteristics, which are not that obvious to breeder or owner alike, or are simply tolerated. This could have quite dramatic effects as those negative results on the phenotype und behavior could influence both judges and the public luring them into a sense of belief that those characteristics are natural and on the whole desirable. Partly through that, the broadness of the "breeding philosophy" is astonishing high. As an example we could look at the IK - and AVK statistics of litters of three Azawakh breeders.


Graphic 4: IK- and AVK distribution at the example of an inbreeding kennel


Graphic 5: IK- and AVK distribution at the example of outcrossing


Graphic 6: IK- and AVK distribution at the example of a bloodline kennel

Tight or inbreeding does not necessarily lead to the end of the pole, especially if IK and AVK get back in balance through timely outcrossing. The threshold for IK stands at the mark of ten and the AVK threshold is believed to be at a figure of 75. Tight - and inbreeding means, in any case, unrecoverable genetic losses and the risk of undesirable and illness causing changes.

I presume that the French kennel club had those dangers in mind (graphic 5). Then their diagnosis would have been objectively correct, but their proposal to change these developments by breeding Sloughi into the Azawakh bloodline in order to achieve a genetical extension cannot be the right way. The real alternative, as already practiced by the German kennel club, is to bring in the original hereditary information of the Azawakh breed.