Genetic Correlations of Hip Dysplasia Scores for Golden Retrievers And
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The Veterinary Journal 226 (2017) 51–56 Contents lists available at ScienceDirect The Veterinary Journal journal homepage: www.elsevier.com/locate/tvjl Original Article Genetic correlations of hip dysplasia scores for Golden retrievers and Labrador retrievers in France, Sweden and the UK a,b,c, b,c d e,f a a a S. Wang *, G. Leroy , S. Malm , T. Lewis , Å. Viklund , E. Strandberg , W.F. Fikse a Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Ulls väg 26, 756 51 Uppsala, Sweden b Génétique Animale et Biologie Intégrative, AgroParisTech, 16 Rue Claude Bernard, 75231 Paris, France c Génétique Animale et Biologie Intégrative, INRA, Domain de Vilvert, 78350 Jouy-en-Josas, France d Svenska Kennelklubben, Rinkebysvängen 70, 163 74 Spånga, Sweden e The Kennel Club, Clarges Street, London W1J 8AB, United Kingdom f School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire LE12 5RD, United Kingdom A R T I C L E I N F O A B S T R A C T Article history: Accepted 27 July 2017 In order to reduce the prevalence of inherited diseases in pedigree dogs, the feasibility of implementation of an international breeding program was investigated. One prerequisite is a strong genetic correlation Keywords: between countries and our objective was to estimate this correlation for canine hip dysplasia (HD) across Best linear unbiased prediction three countries to evaluate the feasibility of an international genetic evaluation. Data were provided by Dog the Société Centrale Canine (SCC, France), Svenska Kennelklubben (SKK, Sweden) and The Kennel Club Genetic correlation (KC, UK) on Golden retriever and Labrador retriever dogs. Trivariate analysis on the three different modes Hip dysplasia of scoring HD in France, Sweden and the UK was performed using a mixed linear animal model. International breeding program Heritability, genetic correlation, number of common sires, genetic similarity, selection differentials and accuracy of selection were calculated. The estimated heritabilities of Golden retrievers (Labrador retrievers) for HD scores were 0.28 (0.15), 0.28 (0.29) and 0.41 (0.34) in France, Sweden and the UK, respectively. The feasibility of performing a genetic evaluation of HD across countries was indicated by the favourable genetic correlations estimated between score modes (ranged from 0.48 to 0.99). The accuracy of selection for the most recent birth year cohorts of male dogs was not improved by international evaluation compared to national evaluation. Improvement in genetic progress can however be achieved by selection across populations in different countries, particularly for small populations, which were indicated by the large difference between selection differentials based on the national and international evaluations. © 2017 Elsevier Ltd. All rights reserved. Introduction selection based on breeding values is the best option to create a long-lasting and widespread improvement in health and welfare. Canine hip dysplasia (HD) has been reported in more than 183 Many studies have reported heritabilities of HD (0.01–0.75; Mäki 1 dog breeds, with a prevalence varying from 0.0 to 71.8%. There is a et al., 2000; Dietschi et al., 2003; Malm et al., 2008; Lewis et al., strong association between the clinical diagnosis of hip status and 2010; Stock et al., 2011; Wilson et al., 2012; Oberbauer et al., 2017; veterinary care and mortality related to HD (Malm et al., 2010). Wijnrocx, 2017) and some have observed favourable genetic Therefore, improving the hip status as measured during routine progress in reducing expression (Malm et al., 2008; Lewis et al., screening can benefit the health and welfare of pedigree dogs. 2013; Oberbauer et al., 2017). However, genetic progress can be Because multiple genes and environmental factors influence HD, difficult to achieve for small populations where sufficient data to enable effective selection is lacking. Meanwhile, within a country, high selection intensity can increase the inbreeding level, which is a general risk factor for the expression of inherited diseases (Leroy * Corresponding author at: Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Ulls väg 26, 756 51 Uppsala, Sweden. and Baumung, 2011). Hence, enlarging the size of the population E-mail address: [email protected] (S. Wang). available for selection by combining data from several countries 1 See: Orthopedic Foundation for Animals, 2016. http://www.ofa.org/stats_hip. could be beneficial. htmlt (Accessed 23 July 2017). http://dx.doi.org/10.1016/j.tvjl.2017.07.006 1090-0233/© 2017 Elsevier Ltd. All rights reserved. 52 S. Wang et al. / The Veterinary Journal 226 (2017) 51–56 litter effects and clinic-year effects, respectively. The vector of fixed effects To achieve high accuracy for genetic evaluations across consisted of different factors for each trait: for France, it included sex, birth year and countries, the traits measured in each country must show strong birth month; for Sweden, it included sex, birth month, year of examination, method genetic correlations. Investigators previous demonstrated feasibil- of sedation, and a third-degree polynomial of age at screening; for UK, it included ity of international genetic selection for HD by observing strong sex, birth year, birth month, age at screening and year of examination. The vector of and favourable genetic correlations for HD between Sweden and additive genetic effects followed the multivariate normal distribution: 0 2 31 2 3 the UK (Fikse et al., 2013). However, the genetic correlations in that s2 s s a A A aFRaSE A aFRaUK FR B 6 aFR 7C study were estimated using correlations between nationally 4 5 2 a N@0; 4 As As As 5A; SE aFRaSE aSE aSE aUK 2 estimated breeding values. Therefore, we sought to estimate aUK As As As aFRaUK aSE aUK aUK genetic correlations for HD between countries by combining where A is the numerator relationship matrix using pedigree information trimmed pedigrees and phenotypic records from three countries (France, 2 s for available HD records and a is the additive genetic variance; the vector of litter Sweden and the UK) for two breeds – Golden retrievers and effects was assumed to follow a multivariate normal distribution without any Labrador retrievers – to investigate if genetic progress and covariances: accuracy of selection can be improved by selection across 0 2 31 2 3 2 Is 0 0 lFR lFR countries. 4 5 B 6 2 7C s I N@0; 4 0 I 0 5A; SE lSE 2 lUK 0 0 Is lUK Materials and methods the vector of clinic-year effects (SE only) followed a normal distribution: The Société Centrale Canine (SCC, France), Svenska Kennelklubben (SKK, 2 ; s ; cySE N 0 I cy Sweden), and The Kennel Club (KC, UK) provided information on both pedigrees and SE phenotypic records of HD for two dog breeds: Golden retrievers and Labrador and the residual vector was assumed to be multivariate normally distributed: retrievers. For each breed, the pedigree databases from the three countries were 2 3 0 2 31 merged into one combined pedigree database by identifying and replacing IDs for 2 Is 0 0 eFR eFR the individual dogs listed with more than one ID (Wang et al., 2017). After merging, 4 5 B 6 2 7C e N@0; 4 0 Is 0 5A: SE eSE the combined pedigree database contained 667,277 records for Golden Retrievers 2 eUK 0 0 Is eUK and 1,426,542 records for Labrador retrievers. Three grading systems are widely used throughout the world: the FCI Genetic similarity (GS) between populations was calculated as the proportion of (Fédération Cynologique Internationale), the OFA (Orthopedic Foundation for screened offspring of common sires (with screened offspring in two populations) in Animals), and the BVA/KC (British Veterinary Association/The Kennel Club) modes. relation to the total number of screened offspring in the two populations (Rekaya The scoring modes for HD are not the same in the three countries (Table 1). France et al., 1999): fi – follows the FCI system, which grades HD into ve categories (A E). For the diagnosis X À Á Nij of HD in the FCI system, A and B are normal, C is mild, D is moderate and E is severe þ nik njk GS ¼ X k¼1 X hip dysplasia. Sweden had a (different) five-level grading system for HD before ij Ni þ Nj nik njk 2000, and thereafter, Sweden started to follow the FCI system. The UK uses the BVA/ k¼1 k¼1 KC system, which has nine features for each hip scored from 0 to 6, except one where Nij is the number of sires with offspring in countries i and j, Ni and Nj are the feature which is scored from 0 to 5. Summing up the scores from the nine features number of sires in countries i and j, respectively, and nik and njk are the number of for two legs, the total HD score (H) ranges from 0 to 106 in the UK (the lower the progenies of sire k in countries i and j, respectively. total score, the better the HD). Selection differentials (S) for male dogs born 2010–2014 were calculated for two We regarded the score mode in each country as a separate trait to measure HD scenarios: selection within country and selection across countries. In the first and transformed the scores to better follow a normal distribution. For French HD scenario, EBVs from national genetic evaluations were used to identify the 100 male scores, the levels of HD (A, B, C, D, and E) were replaced with 1, 2, 3, 4, and 5, dogs of highest genetic merit. EBVs from international genetic evaluation were used respectively. For Swedish HD scores, each grade of HD was first transformed to a in the second scenario to identify the top 100 male dogs among all male dogs, normal score, and this was done separately for the two scoring systems.