Je remets ici une réponse du kennel club anglais qui peut apporter un éclairage sur sa position concernant cette question aussi:
http://www.pastorescozzese.com/allevare/note_e.htmextrait:
En outre, la nécessité d'élargir le pool génétique a également été réaffirmé par la FCI dans la Circulaire no. 4/2012 de (DIRECTIVES SPÉCIFIQUES FCI GÉNÉRALES ET propos race CROIX des races et variétés de la race) 01.09.2012 qui définit les lignes directrices sur les croisements entre les races et les variétés de races et que le premier point affirme:
La FCI encourage croisements entre variétés de la race afin d'augmenter le pool de gènes et d'améliorer la santé de chien: ce n'est pas bénéfique pour la santé dans l'élevage de chiens d'avoir trop de petites populations.
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De même que cette récente étude italienne qui montre le degré larmant de consanguinité de tous les colleys:
August 8, 2013
Results of a study on genetic variability of the Rough Collie
by Conny Di Costanzo
I discussed a thesis on genetic variability of the Rough Collie, so I know the consequences of the excessive use of a few subjects, that within our breed took place both in ancient times and in more modern times, and indeed continues to occur today. These consequences are the result of what in genetics is called the "founder effect" which leads, within a breed, more disadvantages than benefits, so I wondered how the use of a limited number of stallions has had influence on the collie today in terms of relationship and consanguinity.
Relationship and consanguinity, but what it is meant with these two terms?
Considering that a chromosome is a sequence of genes and that the gene is an hereditary unit that controls a character, we can say that each individual has two copies of each gene; each of them is placed on a chromosome. In all the cells, except the reproductive ones, the chromosomes come in pairs, two chromosome 1, two chromosome 2, etc. (in the reproductive cells instead we have only one copy) so that when the egg and sperm fuse to create a new individual, its chromosomes will form new pairs, in which one chromosome is given by the father and the other from the mother.
The relationship can be defined as the probability that a gene placed at a specific point of a particular chromosome of an individual is identical (coming from a common ancestor) to the gene placed at the same point of the same chromosome of another individual.
You can imagine how this probability is obviously high between parents and children and how it can be still considerable among direct relatives (grandparents, great-grandparents) or collateral relatives (uncles, cousins). But if this happens between two individuals who apparently have nothing in common? In this case it means that maybe a lot back in the pedigrees of those individuals there is an ancestor common to both subjects.
The situation becomes more dangerous when the two individuals have a lot of identical genes, since this can only occur following an extreme use of one or few common ancestors, with a consequent increase of relationship.
The inbreeding coefficient is instead a typical parameter of a particular subject (it does not depends on the comparison between individuals) and it is equivalent to the probability that two genes placed on homologous chromosomes (in pairs) are identical because they derived from a common ancestor. This can only occur if the parents of this individual are relatives.
The consanguinity therefore depends directly on the family relationship: from the mathematical point of view the consanguinity of an individual is equal to half of the relationship between the parents.
The relation of a subject with itself is equal to 100%, while that between father and son is equal to 50%, ie its value is halved in each generation. These information was calculated considering that all subjects appear in the pedigree only one time, in other words these are true only if the puppy's mother and father are not relatives, otherwise the parent-child relationship will be more than 50%. Higher the degree of relationship between the two parents, the higher the consanguinity presented by their offspring. For example, if a subject A is both father and grandfather of the subject C, the relationship between A and C is equal to 75% (50 +25)!
In any breeding it is very important to monitor the inbreeding coefficient of individuals to reproduce, in order to avoid the deleterious effects that occur as a result of excessive use of consanguinity. These effects can be summarized in three main points:
Wider probability of expression of recessive rare and undesirable genes, which in normal conditions remain in the heterozygous state (present, ie, in one of the two paired chromosomes) and therefore do not exhibit their effects, while at the homozygous state (ie, when they are present in both homologues chromosomes) allow the occurrence of hereditary diseases, especially skeletal, ocular and cardiovascular disease;
Reduction of genetic variability of the population, which is less susceptible to the genetic improvement, because if all individuals are genetically identical to each other it is not possible to make any selective choice, in practice any breed animal (stallion or mare) can make improvements to the breed;
Appearance of the phenomenon known as "inbreeding depression", ie a general reduction in the average performance of the consanguineous subjects; the population loses the ability to adapt themselves to the environment and as it is increasingly unsuited to the job should be allocated (for both morphological that character features). There will also be a negative impact on reproductive characters: fertility reduction, the conception rate and the number of puppies born alive, with clear negative consequences on breeding.
To avoid the appearance of these deleterious effects, the serious breeders, those who do their work conscientiously, thinking first of all to breed, trying to avoid mating between relatives of first or second degree (close relatives) but nonetheless many of them do not take in consideration the so-called "back-ground inbreeding", ie the inbreeding that is accumulated from generation to generation. It should be right to monitor all the previous generations possible, just to avoid reaching, over time, a critical level of inbreeding.
Pour éviter l'apparition de ces effets délétères, les éleverus sérieux, ceux qui font leur travail avec conscience, pensent d'abord à éviter, dans leur élevage, à marier des parents proches (1° et 2° degrés), mais beaucoup d'entre eux ne prennent pas en considération ce qu'on pourrait appelé 'l'arrière-plan consanguin", càd la consanguinité qui s'est accumulée de génération en géénération. Il faudrait examiner toutes les générations précédentes possibles, juste pour éviter d'atteindre, au fil du temps, le seuil critique de consanguiné .It is through this mechanism that the great stallions of the past could seriously affect the health of present collie.
C'est par ce mécanisme que les grands reproducteurs du passé pourraient affecte sérieusement la santé des colleys actuels.To find out how large is this influence, it is necessary to study the pedigree of a subject today (better if born in the last year) going back as much as possible in the past generations and entering the data obtained in specific statistical programs.
Pour comprendre combien est grande cette influence, il faut étudiet le pédigrée d'un sujet d'aujourd'hui (né si possible dans l'année) et remonter ausi loin que possible dans les générations passées, et entrer toutes les données obtenues dans un programme spécifique de statistiques.
This was the object of the training I have done in the Laboratory of Genetic Biotechnology Department of Veterinary Sciences, in the University of Pisa. This work become easier thanks to the precision with which the collie breeders and the fans of the collie have always taken note of the mating, making myself available an exceptional database, which allowed me to go up in the pedigree of 80 generations, reaching up to the collie of mid-nineteenth century; database that is impossible to achieve for other breeds (ie , for the Italian Bracco, who was the first breed recognized ENCI could be traced only 16 generations).
C'est ce que j'ai fait au Laboratoire de biotechnologie génétique des facultés de Sciences vétérinaires à l'université de Pise. Ce travail fut facilité par la précision avec laquelle les éleveurs et les fans de colleys ont toujours pris note des accouplements, ce qui m'a permis de disposer d'une base de données exceptionnelle, me permettant de remonter dans le pédigrée de 80 générations, atteignant jusqu'au colley du milieu du 19°s., base de données qu'il est impossible de réaliser pour d'autres races (par ex, pour le Braque italien, qui faut le 1° race à être reconnue ENCI, on peut tracer seulement 16 générations)Despite the fact that the collie analyzed by me came from all over Europe (Italy, France, Germany, England ...) and even from America, the values of relationship and consanguinity were elevated. The most alarming data is that the subjects of the last 15 generations monitored (the most recent) are all related, this means that two subjects taken at random from these generations, will be surely relatives, despite the geographical distance.
En dépit du fait que les colleys que j'ai étudiés venaient de toute l'Europe (italie, France, Allemagne, Angleterre...) et même de l'Amérique, les valeurs de parentée et de consanguinité étaient élevés. Le fait le plus alarmant, c'est que les sujets des 15 dernières générations étudiées (les plus récentes) sont tous reliés, cela signifie que 2 sujets pris au hasard dans ces générations sont sûrement parents, malgré la distane géographique.The Clemson University researchers are conducting a study on the genes of the immune system (MHC haplotypes) to evaluate the diversity of collie in different countries. The fact is extraordinary and worrying because they have not found any differences between all the collies present in American. No difference! As if all the American collies was all brothers.
Les chercheurs de l'Université Clemson ont conduit une étude sur les gènes du système immunitaire (les haplotytes CMH) pour évaluer la diversité des colleys dans différentes régions. Le fait est extraordinaire et inquiétant parce qu'ils n'ont pas trouvé de différences entre tous les colleys présents dans l'Amérique. Aucune différence! Comme si tous les colleys américains était tous frères.The explanation for this situation should be sought in two main phenomena.
L'explication de cette situation doit être recherchée dans deux phénomènes principaux:
The first is the so-called "trendy of Lassie", from which there was a considerable increase in the demand for puppies, which has forced the breedings to adapt to the increased demand by producing a greater number of litters per year, using however , for this purpose, the breed animals already present in the breedings. To aggravate the situation is the fact that this trend has been repeated every time a new film with Lassie went out in the cinemas or a new show appeared in television, making a great raise of the number of persons registered in the Stud Books from about 400 to more than 1000 within a couple of years;
Le 1° est ce qu'on pourrait appeler le phénomène Lassie qui a considérablement multiplié la demande de chiots, ce qui a forcé les éleveurs à produire beaucoup, élever beaucoup de nichées par année, en utilisant les chiens déjà présents dans l'élevage.... Et pour aggraver la situation, les films sur Lassie se sont succédés au cinéma puis à la TV... The second is the reduction in the number of subjects that the breed has experienced during the two world wars. The economic hardships have caused a sharp drop in demand for puppies that has determined the closure of many farms. In the subsequent economic recovery occurred in every war, the breed was reconstructed from a limited number of subjects.
La seconde est la réduction du nombre de colleys au cours des deux guerres mondiales. Les difficultés économiques ont entraîné la fermeture de plusieurs fermes. Dans la reprise économique qui a suivi, larace a été reconstruite à partir d'un nombre limité de sujets.For all these reasons, if we rebuild the pedigree of stallions and mares that over the years have had more children, we realize that they are all closely related to each other.During my research I have found, in a single pedigree, at least 34 subjects with the same father, this means that the children of this stallion have been repeatedly re-coupled with their relatives causing a significant increase in relationship and consanguinity of their descendants.
Pour toutes ces raisons, si nous reconstruisons les pedigrées des étalons et des lices qui au fil des ans ont eu plusieurs chiots, on se rend compte qu'ils sont tous étroitement liés les uns aux autres. Au cours de mes recherches, j'ai trouvé, en un seul pedigree, au moins 34 sujets avec le même père, cela signifie que les enfants de cet étalon ont été maintes fois re-couplés avec leurs proches provoquant une augmentation significative de la relation et la consanguinité de leurs descendants.
The results make me assume that all the collie of today descended from a collie named Trefoil, born in Ireland in 1873 and the recent stallions, very used, such as Eden Examine (1944) Mywicks Meadow Lancer (1955) and Dazzler of Dunsinane (1962) are present in the pedigree of more than 90% of current Europeans Rough Collies.
Les résultats me font supposer que tous les colleys d'aujourd'hui descendent d'un même colley nommé Trefoil, né en Irlande en 1873 et les étalons récents, très utilisés, tels que Eden Examiner (1944), Mywicks Meadow Lancer (1955), et Dazzler de Othello (1962) sont présents dans le pedigree de plus de 90% des colleys roughs européens actuels .The levels of inbreeding found in my research were , for the reasons given, at very high levels, with the collie of the last 15 generations that are all relatives (100% of inbreeding) and those from the 55th generation of inbreeding with a percentage of over 94 %.
Les niveaux de consanguinité trouvé dans mes recherches étaient, pour les raisons indiquées, à des niveaux très élevés, avec les colleys des 15 dernières générations qui sont tous les parents (100% de consanguinité) et ceux à partir de la 55° génération avec un pourcentage de consanguinité de plus de 94%.If the farmers do not take note of this situation we will have subjects with higher values of relationship and consanguinity, and then with more and more individuals genetically similar and therefore unable to adapt themselves to the environment and to evolve. So, in respect of rising of health checks concerning the major diseases that affect the breed, we could have a collie getting sick more easily and showing character and reproductive problems. This happens because of increasing of the relationship that reflects the increase of the probability of rare recessive hereditary disease, which at some point will be massively present in the population.
To stop this possibility it would be appropriate to make a study on molecular and genealogical data of all the current Rough collie and enter the results in a database searchable by all those who have the intention to reproduce their own subjects to be able to predict the future values of the puppies, and then select the mating that will give the best results in terms of health, not only of beauty.
At the same time, to improve the situation, it could be interesting to introduce into breeding programs the collies from America, of course not forgetting that this solution has its weak point that coincides exactly with its strong point, ie that the American collie belong to a population that has been isolated from the European too many time of its history, so they may have the same problems of Europe rough collie, also if focused on different stallions. But it is important to not forget that these subjects, however, descended from Trefoil, through the great stallions of '900 which were sold in the United States.
Another help could come from the mating with the Smooth Collie. However, given the small number of smooth, their genetic pool could still be reduced so as to not bring great benefits to the Rough Collie, although it would also benefit from that the same short-haired collie.
The genetic diversity is certainly the most useful feature for the survival of a population. The presence of many different "versions" of the same being is also an evolutionary advantage, as it allows the species a greater ability to adapt and therefore of survival in case of special events.
Today, the situation of the rough collie is hard to solve, but if in the near future the breed clubs will promote a serious study and seek together with the farmers the best way for the solution of the problems underlined here, in a few years we could already see the first clear improvements in the breed.
The genetic diversity is certainly the most useful feature for the survival of a population. The presence of many different "versions" of the same being is also an evolutionary advantage, as it allows the species a greater ability to adapt and therefore of survival in case of special events.
Today, the situation of the rough collie is hard to solve, but if in the near future the breed clubs will promote a serious study and seek together with the farmers the best way for the solution of the problems underlined here, in a few years we could already see the first clear improvements in the breed. Last Update: 09/12/2013 03.35
Sujet: une polémique actuelle (nov 13 ) concernant les colleys américains/ anglais. 
Jeu 28 Nov 2013 - 16:45
