Abstract

BREEDING SCHEMES FOR CANINE ORTHOPAEDIC CONDITIONS - ARE THEY WORKING AS EXPECTED? Å. Hedhammar Departments of Clinical Sciences, Swedish University of Agricultural Sciences, Box 7054, Uppsala Sweden The veterinary profession since more than half a century have recognised a clinical entity affecting the hip joints and due to its similarities with a congenital condition in man named it Hip Dysplasia (HD). Since about 30 years the profession also have experienced clinical entities affecting the elbow joint and accordingly named it Elbow Dysplasia (ED). When it became evident that the prevalence of HD as well as ED varied by breed, indicating a significant heritability, screening procedures to indicate affected individuals at an early stage was instituted. Based on standardised screening procedures various forms of measures and a few formal breeding programmes have been instituted. In the perspective of efforts by the profession as well as cynological organisations and breeders world wide it is pertinent to evaluate the outcome. However, lack of population based studies hampers possibilities to evaluate effects on breeding and selection. Included in this presentation is therefore also an evaluation of the material and methods used. That is screening procedures, evaluation of films and registrations of results. Screening procedures Screening programmes organised by various bodies have most commonly been based on radiographs produced at the practice level but centrally evaluated / scrutinized by national and/or breed panels. Within Europe, the protocol approved by Federation Cynologic International (FCI) for HD is most widely used. A meeting in Copenhagen March 2006 with panellists from 25 countries aimed to harmonise its usage. It was noted that a total of more than 90 000 dogs were screened yearly for hip status in Europe. Out of these 27 000 were screened in Germany and 20 000 in Sweden. In UK a hip scoring system developed by BVA/ KC is used and outside Europe the FCI protocol and a slightly different version developed by the Orthopaedic Foundation of Animals (OFA) in US, is most commonly used. With ED, less divergent screening procedures have evolved. Worldwide screening programmes for ED are all based on procedures agreed on within the International Elbow Working Group (IEWG). However number of additional projections and notions on primary lesions besides score of arthroses varies. For HD as well as for ED effects by age, positioning and sedation have called for more standardised procedures. The entity ED is made up of several primary lesions and resulting EA, each of these with a presumed complex inheritance. The clinical course of ED also more commonly results in clinical signs at an early age and an operation before age of screening. These Dogs are likely not to be screened and included in any registries. Arrangements to include data on these Dogs are highly desirable. Evaluation of films by appointed panellists Scooring of HD and ED should ideally be performed by experienced radiologists trained and certified for the task. Seminars to validate and calibrate the evaluations have been organised nationally and by international bodies as FCI and IEWG. Recently an expert panel composed of Marc Flueckiger, Jean- Pierre Genevois, Håkan Kasström, Bernd Tellhelm, Aldo Vezzoni, and Richard Nap (chairman) was appointed to review and suggest additions and changes to the FCI protocol for HD screening, based on proposals at the meeting in Copenhagen. Registries Registries to record the results have been organised by various bodies. Ideally they should contain positive as well as negative result and be open to the public. To be able to serve as resources for breeding programmes they must be linked to ancestral background. An increasing number of registries now fulfil these criteria and computerised content have made it possible to estimate breeding indexes in breeds with sufficient number of individuals screened. The value of screening procedures for traits with a multifactorial background as HD and ED is not only based on the heritability and how accurate the trait is measured. The value is also directly related to accessibility and how the information is used in the selection of breeding stock. Breeding programmes Breeding programmes are based on formalised screening procedures and evaluation criteria, registries of ancestral background and results of all individuals screened in a defined population. They contain various forms of advice, rules and regulation to achieve a change in phenotype as well as genotype in a defined population. Formal breeding programmes to reduce prevalence of HD and ED on a population basis are scarce and published outcome even fewer. Most breeding programmes for HD as well as ED have been based solely on the phenotypic appearance of breeding stock at the time of screening. To various extent a shift from usage of affected and / or unscreened to phenotypic ally unaffected breeding stock have been noticed in breeds/ countries in which such information is available. Based on computerised information not only on individuals but also on relatives including parents and progeny already produced, breeding indexes for HD and ED have been made available in several breeds/countries over the last couple of years. Such information has made it possible to select breeding stock not only by phenotype but also by an indication of genotype for HD and ED. To what extent such information have been used in various population is not well documented. Outcome Although the ultimate goal of screening as well as breeding programmes have been to reduce prevalence of clinical problems ( at any age ), mainly the decrease in prevalence of dogs exhibiting features of HD or ED at the time of screening most commonly without clinical signs, have been monitored. Already from the beginning, effects on individual matings by selection of screened and unaffected breeding stock have been repeatedly proven. Conflicting and even disappointing figures on time trends for prevalence of HD in various screening programmes can be explained by lack of selection pressure despite the numbers of individuals screened. In breed populations where only a smaller fraction is screened and even fewer of these are used for breeding, no decrease in prevalence is to be expected. In national populations where an increasing fraction of breeding stock is screened and unaffected, a decrease has been achieved. When almost all breeding stock is unaffected further decrease has been shown to call for more refined methods for further improvement. For ED and initial shift from unscreened to screened and unaffected breeding stock is still seen in most national breed populations. Recently, reports on documented and validated decrease in phenotype as well as genotype for both HD (1) and ED (2) have been published for extensively screened population of German Shepherd for HD (1) and for HD and ED in Burmese Mountain dog and Rottweilers (2). Further perspectives Further improvement calls for more refined tools as breeding indexes and possibly also genetic markers. To achieve an enhanced outcome of all efforts to reduce prevalence of HD and ED, collaborative efforts have to be made. Promotion not only of the screening programmes but also of its use in formal breeding programmes is an issue for the profession as well as the cynological organisations. The veterinary profession also have the responsibility for accuracy of screening at practice level by submission of all results and at the level of national /breed panels by training and validation the competence of those who serve as scrutinisers / panellists. References V.Janutta , H. Hamann, O. Distl (2008) Genetic and phenotypic trends in canine hip dysplasia in the German population of German shepherd dogs. Berl Munch Tierarztl Wochenschr. Mar-Apr;121(3-4):102-9. S. Malm, E. Strandberg, W.F. Fikse, B. Danell (2008) Genetic Variation and Genetic Trends in Hip and Elbow Dysplasia in Swedish Rottweiler and Bernese Mountain Dog Journal of Animal Breeding and Genetics. (Publ. on-line may 21st)

Published in

Conference

15th European Society of Veterinary Orthopaedics and Traumatology

SLU Authors

• Hedhammar, Åke

  • Department of Clinical Sciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Veterinary Science
Animal and Dairy Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/20282