Controlling canine hip dysplasia in Finland

Influence of Femoral Position and Pelvic Projection on Norberg Angle Measurements

OBJECTIVE

 Canine hip dysplasia is a common orthopaedic disease in dogs. The Norberg angle value is a measure of hip joint laxity. The aim of this study was to quantify the degree of rotation necessary to consider the radiograph as inadequately positioned and to determine the influence of rotation on the Norberg angle.

STUDY DESIGN

 Three sets of radiographs with different positioning and projections were acquired using 10 canine cadavers. Rotation of the pelvis was simulated by rotating the X-ray tube without changing the position of the patient.

RESULTS

 In dorsoventral projections, the Norberg angle value is increased by 3.2 to 5.8%. Due to rotation along the long axis, the Norberg angle increases on one side and decreases on the contralateral side by approximately the same value. Rotation of greater than 2 degrees in a lateral direction is visually perceived by the observer as tilted. Rotation of the projection in the caudoventral to craniodorsal direction causes mild increase of the Norberg angle (≤1%), while rotation of the projection in a cranioventral to caudodorsal direction causes moderate (≤2%) decrease of the Norberg angle. Rotation of less than -10 degrees (caudoventral to craniodorsal) or greater than 10 degrees (cranioventral to caudodorsal) is visually perceived as tilted.

CONCLUSION

 Tilted images that are subjectively perceived evaluable have only little effect on the Norberg angle and are therefore probably acceptable. Dorsoventral projections can be recognized based on the proximal position of the patella and should be excluded from evaluation, as the Norberg angle value can be falsely increased.

Distraction index and Norberg angle to distinguish dysplastic and non-dysplastic hips based on FCI score

OBJECTIVE

Radiographic hip scoring according to the Fédération Cynologique Internationale (FCI) and PennHIP (Pennsylvania Hip Improvement Program) method was performed with the purpose to compare the PennHIP and FCI results as well as coxofemoral joint laxity by correlation of Norberg angle and distraction index measurements.

MATERIALS AND METHODS

A total of 167 dogs of various breeds presented for official screening examination in a veterinary teaching hospital in Germany were included. Using receiver operating characteristic analysis, the best Norberg angle and distraction index cut-off values to distinguish between dysplastic and non-dysplastic groups based on FCI grades and to distinguish between lax and tight hip joints according to the PennHIP proposal were calculated.

RESULTS

More than one third (38.2 %) of dogs that passed the breeding criterions according to FCI (grades A and B) were in the half of the population with lax hip joints and should not be used for breeding according to the PennHIP proposal. A cut-off value for the distraction index of 0.44 with sensitivity of 82.7 % and specificity of 84.2 % was superior to the best cut-off value for the Norberg angle at 101.8° with sensitivity of 82.7 % and specificity of 71.9 % to discriminate between non-dysplastic joints (A, B) and dysplastic joints (C, D, E).

CONCLUSIONS AND CLINICAL RELEVANCE

Our results show a limited impact of laxity on the FCI grading. Breeding selection processes that are based on the FCI method could profit by an additional and complementary use of the distraction index.

Prevalence of canine hip dysplasia in 10 breeds in France, a retrospective study of the 1997-2017 radiographic screening period

Canine hip dysplasia (HD) is a complex developmental disease of the coxo-femoral joint and is one of the most common orthopedic conditions in dogs. Due to the genetic contribution, most of the programs fighting against HD recommend selective breeding that excludes affected dogs. Using the best-scoring dogs for breeding may reduce the prevalence of HD. In France, the phenotypic screening of coxo-femoral joint conformation remains a strategy for breeders to establish selection decisions. The HD prevalence was evaluated in 10 breeds, based on the assessment of 27,710 dogs, during the 1997-2017 screening period, which was divided into 3 homogeneous cohorts for analysis. The global HD prevalence varied widely among breeds from 5% (Siberian Husky) to 51.9% (Cane Corso). It decreased over time in 6 breeds, among which 4 (Cane Corso, Gordon Setter, Rottweiler and White Swiss Shepherd) showed a significant decrease. A statistically significant increase in HD prevalence was noted for the Siberian Husky. Although the efficacy of phenotype-based breeding programs remains controversial, our results are in accordance with several recent studies showing that long-term selection policies are valuable, as they may help decreasing the HD prevalence in some breeds. The complementary use of more recent tools such as estimated breeding values and genomics would probably help breeders achieve more substantive results.

Comparison of Reliability of Norberg Angle and Distraction Index as Measurements for Hip Laxity in Dogs

OBJECTIVE

 The main purpose of the study was to compare reliability of measurements for the evaluation of hip joint laxity in 59 dogs.

MATERIALS AND METHODS

 Measurement of the distraction index (DI) of the PennHIP method and the Norberg angle (NA) of the Fédération Cynologique Internationale (FCI) scoring scheme as well as scoring according to the FCI scheme and the Swiss scoring scheme were performed by three observers at different level of experience. For each dog, two radiographs were acquired with each method by the same operator to evaluate intraoperator-reliability.

RESULTS

 Intraoperator-reliability was slightly better for the NA compared with the DI with an intraclass correlation coefficient (ICC) of 0.962 and 0.892 respectively. The ICC showed excellent results in intraobserver-reliability and interobserver-reliability for both the NA (ICC 0.975; 0.969) and the DI (ICC 0.986; 0.972). Thus, the NA as well as the DI can be considered as reliable measurements. The FCI scheme and the Swiss scoring scheme provide similar reliability. While the FCI scheme seems to be slightly more reliable in experienced observers (Kappa FCI 0.687; Kappa Swiss 0.681), the Swiss scoring scheme had a noticeable better reliability for the unexperienced observer (Kappa FCI 0.465; Kappa Swiss 0.514).

CLINICAL SIGNIFICANCE

 The Swiss scoring scheme provides a structured guideline for the interpretation of hip radiographs and can thus be recommended to unexperienced observers.

Heritability of hip dysplasia: Preliminary results for German Shepherd dogs in Brazil

The heritability of canine hip dysplasia in German Shepherd dogs was estimated using Bayesian methods. Data on hip score and status of 1632 dogs born from 1990 to 2013 were provided by the Brazilian Society of German Shepherd Breeders. Heritability estimates (mean ± standard deviation) were 0.1979 ± 0.058 for hip scores and 0.187 ± 0.055 for hip status. We observed no phenotypic trends and a small rate of genetic trend (0.52%) according to the year of birth, probably because of ineffective phenotypic selection and absence of genetic selection. The heritability estimates in this study can be used to achieve effective selective breeding and genetic gains, which in turn can result in improvements in dog health and welfare.

Evaluating oxidative stress, serological- and haematological status of dogs suffering from osteoarthritis, after supplementing their diet with fish or corn oil

Background

Oxidative stress plays an important role in the pathogenesis of disease, and the antioxidant physiological effect of omega-3 from fish oil may lead to improvement of canine spontaneous osteoarthritis (OA).

Methods

In this prospective randomized, controlled, double-blinded study, we assessed haematological and biochemical parameters in dogs with OA following supplementation with either a concentrated omega-3 deep sea fish oil product or corn oil. Blood samples from 77 client-owned dogs diagnosed as having OA were taken before (baseline) and 16 weeks after having orally ingested 0.2 ml/Kg bodyweight/day of deep sea fish oil or corn oil. Circulating malondialdehyde (MDA), glutathione (GSH), non-transferrin bound iron (NTBI), free carnitine (Free-Car), 8-hydroxy-2-deoxyguanosine (8-OH-dG), and serum fatty acids, haemograms and serum biochemistry were evaluated. Differences within and between groups from baseline to end, were analysed using repeated samples T-test or Wilcoxon rank test and independent samples T-test or a Mann-Whitney test.

Results

Supplementation with fish oil resulted in a significant reduction from day 0 to day 112 in MDA (from 3.41 ± 1.34 to 2.43 ± 0.92 μmol/L; P < 0.001) and an elevation in Free-Car (from 18.18 ± 9.78 to 21.19 ± 9.58 μmol/L; P = 0.004) concentrations, whereas dogs receiving corn oil presented a reduction in MDA (from 3.41 ± 1.34 to 2.41 ± 1.01 μmol/L; P = 0.001) and NTBI (from −1.25 ± 2.17 to −2.31 ± 1.64 μmol/L; P = 0.002). Both groups showed increased (albeit not significantly) GSH and 8-OH-dG blood values. Dogs supplemented with fish oil had a significant reduction in the proportions of monocytes (from 3.84 ± 2.50 to 1.77 ± 1.92 %; P = 0.030) and basophils (from 1.47 ± 1.22 to 0.62 ± 0.62 %; P = 0.012), whereas a significant reduction in platelets counts (from 316.13 ± 93.83 to 288.41 ± 101.68 × 10⁹/L; P = 0.029), and an elevation in glucose (from 5.18 ± 0.37 to 5.32 ± 0.47 mmol/L; P = 0.041) and cholesterol (from 7.13 ± 1.62 to 7.73 ± 2.03 mmol/L; P = 0.011) measurements were observed in dogs receiving corn oil.

Conclusions

In canine OA, supplementation with deep sea fish oil improved diverse markers of oxidative status in the dogs studied. As corn oil also contributed to the reduction in certain oxidative markers, albeit to a lesser degree, there was no clear difference between the two oil groups. No clinical, haematological or biochemical evidence of side effects emerged related to supplementation of either oil. Although a shift in blood fatty acid values was apparent due to the type of nutraceutical product given to the dogs, corn oil seems not to be a good placebo.

Genetic variances, trends and mode of inheritance for hip and elbow dysplasia in Finnish dog populations

The aims of this study were to assess genetic variances, trends and mode of inheritance for hip and elbow dysplasia in Finnish dog populations. The influence of time-dependent fixed effects in the model when estimating the genetic trends was also studied. Official hip and elbow dysplasia screening records of 42 421 dogs from seven breeds were analysed with REML. To investigate the mode of inheritance of hip and elbow dysplasia, trait distributions, genetic variances and regressions of offspring phenotypes on parental predicted breeding values were studied separately in males and in females. Genetic trends for hip dysplasia between the years 1983 and 1998 were favourable only in the Rottweiler. In elbow dysplasia, the trends were favourable after the year 1992 in all the four breeds studied but the overall changes were small. The reason for this seemed to be negligible selection pressure against these traits. Time-dependent fixed effects in the model had an influence on the estimated genetic trends, resulting either in a more negative or more positive genetic trend compared with the model from which the time-dependent effects were removed. Mitochondrial or sex-linked inheritance did not seem likely in the expression of hip and elbow dysplasia in the populations studied. Regression coefficients of offspring phenotypes on estimated parental breeding values were approximately equal to their expected value in a situation with equal parental contribution. Furthermore, the phenotypic frequency distributions of hip and elbow dysplasia grades were similar among males and females in each breed studied. No indication of major genes was found in the offspring frequency distributions within individual sires. According to these Finnish data, mode of inheritance for both hip and elbow dysplasia is polygenic (quantitative) with equal expression of the genes from both parents, although the estimates of heritability for hip dysplasia in the Rough Collie and for elbow dysplasia in the German Shepherd and the Golden Retriever were somewhat different in males compared with females.

A genetic predictive model for canine hip dysplasia: integration of Genome Wide Association Study (GWAS) and candidate gene approaches

Canine hip dysplasia is one of the most prevalent developmental orthopedic diseases in dogs worldwide. Unfortunately, the success of eradication programs against this disease based on radiographic diagnosis is low. Adding the use of diagnostic genetic tools to the current phenotype-based approach might be beneficial. The aim of this study was to develop a genetic prognostic test for early diagnosis of hip dysplasia in Labrador Retrievers. To develop our DNA test, 775 Labrador Retrievers were recruited. For each dog, a blood sample and a ventrodorsal hip radiograph were taken. Dogs were divided into two groups according to their FCI hip score: control (A/B) and case (D/E). C dogs were not included in the sample. Genetic characterization combining a GWAS and a candidate gene strategy using SNPs allowed a case-control population association study. A mathematical model which included 7 SNPs was developed using logistic regression. The model showed a good accuracy (Area under the ROC curve = 0.85) and was validated in an independent population of 114 dogs. This prognostic genetic test represents a useful tool for choosing the most appropriate therapeutic approach once genetic predisposition to hip dysplasia is known. Therefore, it allows a more individualized management of the disease. It is also applicable during genetic selection processes, since breeders can benefit from the information given by this test as soon as a blood sample can be collected, and act accordingly. In the authors' opinion, a shift towards genomic screening might importantly contribute to reducing canine hip dysplasia in the future. In conclusion, based on genetic and radiographic information from Labrador Retrievers with hip dysplasia, we developed an accurate predictive genetic test for early diagnosis of hip dysplasia in Labrador Retrievers. However, further research is warranted in order to evaluate the validity of this genetic test in other dog breeds.

Genomic prediction of traits related to canine hip dysplasia

Increased concern for the welfare of pedigree dogs has led to development of selection programs against inherited diseases. An example is canine hip dysplasia (CHD), which has a moderate heritability and a high prevalence in some large-sized breeds. To date, selection using phenotypes has led to only modest improvement, and alternative strategies such as genomic selection (GS) may prove more effective. The primary aims of this study were to compare the performance of pedigree- and genomic-based breeding against CHD in the UK Labrador retriever population and to evaluate the performance of different GS methods. A sample of 1179 Labrador Retrievers evaluated for CHD according to the UK scoring method (hip score, HS) was genotyped with the Illumina CanineHD BeadChip. Twelve functions of HS and its component traits were analyzed using different statistical methods (GBLUP, Bayes C and Single-Step methods), and results were compared with a pedigree-based approach (BLUP) using cross-validation. Genomic methods resulted in similar or higher accuracies than pedigree-based methods with training sets of 944 individuals for all but the untransformed HS, suggesting that GS is an effective strategy. GBLUP and Bayes C gave similar prediction accuracies for HS and related traits, indicating a polygenic architecture. This conclusion was also supported by the low accuracies obtained in additional GBLUP analyses performed using only the SNPs with highest test statistics, also indicating that marker-assisted selection (MAS) would not be as effective as GS. A Single-Step method that combines genomic and pedigree information also showed higher accuracy than GBLUP and Bayes C for the log-transformed HS, which is currently used for pedigree based evaluations in UK. In conclusion, GS is a promising alternative to pedigree-based selection against CHD, requiring more phenotypes with genomic data to improve further the accuracy of prediction.

Quantitative trait loci mapping for canine hip dysplasia and its related traits in UK Labrador Retrievers

Background

Canine hip dysplasia (CHD) is characterised by a malformation of the hip joint, leading to osteoarthritis and lameness. Current breeding schemes against CHD have resulted in measurable but moderate responses. The application of marker-assisted selection, incorporating specific markers associated with the disease, or genomic selection, incorporating genome-wide markers, has the potential to dramatically improve results of breeding schemes. Our aims were to identify regions associated with hip dysplasia or its related traits using genome and chromosome-wide analysis, study the linkage disequilibrium (LD) in these regions and provide plausible gene candidates. This study is focused on the UK Labrador Retriever population, which has a high prevalence of the disease and participates in a recording program led by the British Veterinary Association (BVA) and The Kennel Club (KC).

Results

Two genome-wide and several chromosome-wide QTLs affecting CHD and its related traits were identified, indicating regions related to hip dysplasia.

Conclusion

Consistent with previous studies, the genetic architecture of CHD appears to be based on many genes with small or moderate effect, suggesting that genomic selection rather than marker-assisted selection may be an appropriate strategy for reducing this disease.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-833) contains supplementary material, which is available to authorized users.

Assessing the impact of genomic selection against hip dysplasia in the Labrador Retriever dog

Many purebred dogs exhibit a higher prevalence of inherited diseases compared with non-purebred dogs. One of the most popular breeds in the UK is the Labrador Retriever, which has a high prevalence of hip dysplasia resulting in high costs for surgical operations and impaired animal welfare. Considering the many complications of highly managed populations, mainly due to breeder's conventions and the resulting population structure, is of great importance for the proper development of a strategy against the disease. In this study, we have compared the utilities and performances of both genomic and phenotypic selection against hip dysplasia in a simulated population with the characteristics of the British Veterinary Association and Kennel Club (BV /KC) hip dysplasia scheme. The results confirm the potential benefits of genomic selection by showing a moderate increase of 1.15-fold (assuming a realistic accuracy of r(2) = 0.5) in response to selection due to the higher accuracy (between 0.96- and 1.32-fold, considering 0.35 ≤ r(2) ≤ 0.7) and more than a threefold increase when all the offspring in each litter are tested (between 3.25- and 4.55-fold, again considering 0.35 ≤ r(2) ≤ 0.7).

Housing- and exercise-related risk factors associated with the development of hip dysplasia as determined by radiographic evaluation in a prospective cohort of Newfoundlands, Labrador Retrievers, Leonbergers, and Irish Wolfhounds in Norway

OBJECTIVE

To identify housing- and exercise-related risk factors associated with the development of hip dysplasia (HD) as determined by radiographic evaluation in Newfoundlands, Labrador Retrievers, Leonbergers, and Irish Wolfhounds in Norway.

ANIMALS

501 client-owned dogs from 103 litters.

PROCEDURES

Dogs were assessed from birth until official radiographic screening for HD at 12 (Labrador Retriever [n = 133] and Irish Wolfhound [63]) or 18 (Newfoundland [125] and Leonberger [180]) months of age. Information regarding housing and exercise conditions during the preweaning and postweaning periods was obtained with questionnaires. Multivariable random effects logistic regression models were used to identify housing- and exercise-related risk factors associated with the development of radiographically detectable HD.

RESULTS

Puppies walking on stairs from birth to 3 months of age had an increased risk of developing HD. Factors associated with a decreased risk of developing HD included off-leash exercise from birth to 3 months of age, birth during the spring and summer, and birth on a farm. Significant clustering of dogs with HD was detected within litters.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that puppies ≤ 3 months old should not be allowed access to stairs, but should be allowed outdoor exercise on soft ground in moderately rough terrain to decrease the risk for developing radiographically detectable HD. These findings could be used as practical recommendations for the prevention of HD in Newfoundlands, Labrador Retrievers, Leonbergers, and Irish Wolfhounds.

Getting priorities straight: risk assessment and decision-making in the improvement of inherited disorders in pedigree dogs

The issue of inherited disorders in pedigree dogs is not a recent phenomenon and reports of suspected genetic defects associated with breeding practices date back to Charles Darwin's time. In recent years, much information on the array of inherited defects has been assimilated and the true extent of the problem has come to light. Historically, the direction of research funding in the field of canine genetic disease has been largely influenced by the potential transferability of findings to human medicine, economic benefit and importance of dogs for working purposes. More recently, the argument for a more canine welfare-orientated approach has been made, targeting research efforts at the alleviation of the most suffering in the greatest number of animals. A method of welfare risk assessment was initially developed as a means of objectively comparing, and thus setting priorities for, different welfare problems. The method has been applied to inherited disorders in pedigree dogs to investigate which disorders have the greatest welfare impact and which breeds are most affected. Work in this field has identified 396 inherited disorders in the top 50 most popular breeds in the UK. This article discusses how the results of welfare risk assessment for inherited disorders can be used to develop strategies for improving the health and welfare of dogs in the long term. A new risk assessment criterion, the Breed-Disorder Welfare Impact Score (BDWIS), which takes into account the proportion of life affected by a disorder, is introduced. A set of health and welfare goals is proposed and strategies for achieving these goals are highlighted, along with potential rate-determining factors at each step.

Selection against canine hip dysplasia: success or failure?

Canine hip dysplasia (CHD) is a multifactorial skeletal disorder which is very common in pedigree dogs and represents a huge concern for canine welfare. Control schemes based on selective breeding have been in operation for decades. The aim of these schemes is to reduce the impact of CHD on canine welfare by selecting for reduced radiographic evidence of CHD pathology as assessed by a variety of phenotypes. There is less information regarding the genotypic correlation between these phenotypes and the impact of CHD on canine welfare. Although the phenotypes chosen as the basis for these control schemes have displayed heritable phenotypic variation in many studies, success in achieving improvement in the phenotypes has been mixed. There is significant room for improvement in the current schemes through the use of estimated breeding values (EBVs), which can combine a dog's CHD phenotype with CHD phenotypes of relatives, other phenotypes as they are proven to be genetically correlated with CHD (especially elbow dysplasia phenotypes), and information from genetic tests for population-relevant DNA markers, as such tests become available. Additionally, breed clubs should be encouraged and assisted to formulate rational, evidenced-based breeding recommendations for CHD which suit their individual circumstances and dynamically to adjust the breeding recommendations based on continuous tracking of CHD genetic trends. These improvements can assist in safely and effectively reducing the impact of CHD on pedigree dog welfare.

Genetic evaluation of hip score in UK Labrador Retrievers

Hip dysplasia is an important and complex genetic disease in dogs with both genetic and environmental influences. Since the osteoarthritis that develops is irreversible the only way to improve welfare, through reducing the prevalence, is through genetic selection. This study aimed to evaluate the progress of selection against hip dysplasia, to quantify potential improvements in the response to selection via use of genetic information and increases in selection intensity, and to prepare for public provision of estimated breeding values (EBV) for hip dysplasia in the UK. Data consisted of 25,243 single records of hip scores of Labrador Retrievers between one and four years old, from radiographs evaluated between 2000 and 2007 as part of the British Veterinary Association (BVA) hip score scheme. A natural logarithm transformation was applied to improve normality and linear mixed models were evaluated using ASREML. Genetic correlations between left and right scores, and total hip scores at one, two and three years of age were found to be close to one, endorsing analysis of total hip score in dogs aged one to three as an appropriate approach. A heritability of 0.35±0.016 and small but significant litter effect (0.07±0.009) were estimated. The observed trends in both mean hip score and mean EBV over year of birth indicate that a small genetic improvement has been taking place, approximately equivalent to avoiding those dogs with the worst 15% of scores. Deterministic analysis supported by simulations showed that a 19% greater response could be achieved using EBV compared to phenotype through increases in accuracy alone. This study establishes that consistent but slow genetic improvement in the hip score of UK Labrador Retrievers has been achieved over the previous decade, and demonstrates that progress may be easily enhanced through the use of EBVs and more intense selection.

Genetic evaluation of the nine component features of hip score in UK Labrador Retrievers

The aim of this study was to explore the genetic relationship between the nine component traits comprising the British Veterinary Association (BVA) total hip score in UK registered Labrador Retrievers. Data consisted of 11,928 single records of trait scores of dogs aged between one and four years (365–1459 days) old, from radiographs evaluated between 2000 and 2007. Pedigree information was provided by the UK Kennel Club. The distribution of trait scores showed only small numbers of dogs with visible malformation in the six traits that were scored according to the severity of osteoarthritis. Linear mixed models were fitted using ASREML. Estimates of heritability ranged from 0.15 to 0.38, and litter effects from 0.04 to 0.10. Genetic correlations between all nine traits were extremely high ranging from 0.71 to 1.0, implying considerable genetic similarity. The decomposition demonstrated that aggregate scores of only the 3 traits indicative of laxity in one year old dogs was predictive of the phenotype of the remaining six scored on osteoarthritic severity in dogs at 4+ years old. The application of selection index methodology in selecting against hip dysplasia using the trait scores was explored and potential improvements in accuracy (directly related to response to selection) of over 10% are reported compared to the current total hip score. This study demonstrates that traits descriptive of joint laxity are valuable early-age predictors of osteoarthritis and shows that there is scope for improvement in the way data from the UK hip score scheme are used for selection against hip dysplasia in Labradors. This was verified via use of selection indices, which identified substantial increases in accuracy, not only via optimum coefficients, but also through an easily applicable aggregate of scores of just two or three traits only compared with the current total hip score.

A prospective study on canine hip dysplasia and growth in a cohort of four large breeds in Norway (1998-2001)

The study-objective was to measure the effect of weight and growth related parameters on the risk of development of Canine Hip Dysplasia (CHD). The hypothesis was that heavy and fast growing dogs of large sized breeds were at increased risk of development of CHD compared to lighter and slower growing dogs. A prospective cohort study was conducted among dogs of four large breeds: Newfoundland (NF), Leonberger (LEO), Labrador retriever (LR), and Irish wolfhound (IW). The dogs were privately owned with individualized nutrition and environment, and they were followed from birth and throughout the growth period until the official screening for CHD was performed. The study sample consisted of 501 dogs from 103 litters, with the breed distribution 125 NF, 180 LEO, 133 LR, and 63 IW. Because the dogs were clustered in litters a multivariable random effects logistic regression model was used to assess statistically significant growth-related risk factors for CHD. The estimated incidence risk of CHD was 36% in NF, 25% in LEO, 20% in LR, and 10% in IW. Based upon the final multilevel model it appears that the odds of CHD among both LR and IW (odds ratio (OR) 0.22) are about one-fifth of the odds for NF. The odds for LEO (OR 0.60) are not significantly different from NF. There appeared to be an inverse relationship between body weight at 3 months of age and odds of CHD, with an OR of 0.89 (P=0.044). The degree of clustering at the litter-level was high (22.6%) and highly significant (P<0.001). Findings failed to support the hypothesis that heavy and fast growing dogs from four large sized breeds were at increased risk for development of CHD. There might be other unmeasured environmental risk factors for CHD in this cohort of dogs, although the contribution of the genetic variance to the litter-level clustering also needs further investigation.

Simulation study on the effects of excluding offspring information for genetic evaluation versus using genomic markers for selection in dog breeding

Different modes of selection in dogs were studied with a special focus on the availability of disease information. Canine hip dysplasia (CHD) in the German shepherd dog was used as an example. The study was performed using a simulation model, comparing cases when selection was based on phenotype, true or predicted breeding value, or genomic breeding value. The parameters in the simulation model were drawn from the real population data. The data on all parents and 40% of their progeny were assumed to be available for the genetic evaluation carried out by Gibbs sampling. With respect to the use of disease records on progeny, three scenarios were considered: random exclusion of disease data (no restrictions, N), general exclusion of disease data (G) and exclusion of disease data for popular sires (P). One round of selection was considered, and the response was expressed as change of mean CHD score, proportion of dogs scored as normal, proportion of dogs scored as clearly affected and true mean breeding value in progeny of popular sires in comparison with all sires. When no restrictions on data were applied, selection on breeding value was three times more efficient than when some systematic exclusion was practised. Higher selection response than in the exclusion cases was achieved by selecting on the basis of genomic breeding value and CHD score. Genomic selection would therefore be the method of choice in the future.

Association between radiographic assessment of hip status and subsequent incidence of veterinary care and mortality related to hip dysplasia in insured Swedish dogs

Our objective was to evaluate the association between grading of hip status as assessed by radiographic examination (hip screening) and subsequent incidence of veterinary care and mortality related to hip dysplasia (HD) in five breeds of insured dogs in Sweden. Screening results for hip status from the Swedish Kennel Club and data on veterinary care and mortality from the insurance company Agria were merged based on the registration number of the dog. Dogs of five breeds (Bernese Mountain Dogs, German Shepherds, Golden Retrievers, Labrador Retrievers, and Rottweilers) screened during 1995-2004 and covered by an insurance plan for veterinary care or life at the time of screening were included. The study populations included between 1667 and 10,663 dogs per breed. Breed-specific multivariable Cox proportional-hazards analyses were performed to evaluate the impact of radiographic hip status on time from hip screening to first HD-related veterinary and life claim, respectively. The effects of gender, birth season, and a time-varying covariate of year were also studied. Additional analyses, on the five breeds combined, were performed to investigate the effects of hip status, breed, and the interaction between hip status and breed. The effect of hip status was highly significant (P<0.001) for both life and veterinary claims related to HD in all five breeds with increased hazard ratio (HR) for deteriorating hip status. Dogs with moderate or severe hip status at screening had a markedly increased hazard of HD-related veterinary care and mortality compared with dogs assessed as free or mild. The time-varying covariate of year showed a significantly higher HR in the last time period for German Shepherds and Labrador Retrievers in the analyses of veterinary claims. In the analyses on all five breeds, German Shepherds had the highest HR for both veterinary care and mortality related to HD, followed by Bernese Mountain Dogs. Golden and Labrador Retrievers had the lowest HR. The effect of hip status on the hazard was the same irrespective of breed. However, as a consequence of differences between breeds in overall risk, the predictive ability of screening results for subsequent incidence of HD-related problems for individual dogs was breed-dependent. Based on the strong association between radiographic hip status and incidence of HD-related veterinary care and mortality, and the previously reported moderate heritability of hip status, we conclude that selection based on screening results for hip status can be expected to reduce the risk of HD-related clinical problems.

Update of a retrospective cohort study of changes in hip joint phenotype of dogs evaluated by the OFA in the United States, 1989-2003

OBJECTIVE

To determine whether there has been improvement in canine hip joint phenotype classifications of dogs whelped from 1989 to 2003 by the Orthopedic Foundation for Animals (OFA), by examining results of radiographic evaluations and identifying any trends in percentages of dogs classified as having desirable hip joint phenotypes.

STUDY DESIGN

Retrospective cohort study.

SAMPLE POPULATION

OFA radiographic classifications (n=431,483) on dogs whelped between 1989 and 2003.

METHODS

Numbers and percentages of dogs classified by hip joint phenotypes were determined for 2-year cohorts. Differences between breeds and sexes were assessed using the Fisher's exact test, and odds ratios with 95% confidence intervals were calculated to express associations. The Cochran-Armitage test for trend was calculated to identify significant trends over time.

RESULTS

There were statistically significant (P<.05) increases in the proportion of all breeds of dogs evaluated as excellent and good from 1993 to 2003, controlling for gender and age at evaluation. Labrador Retrievers, Bernese Mountain Dogs, and Rottweilers had the highest proportions of excellent and good scores, and the highest rates of improvement in excellent and good scores were seen in Bernese Mountain Dogs and Rottweilers.

CONCLUSIONS

Results support the contention that there have been improvements in hip joint phenotype classifications in dogs in the United States since the previous study (1989-1992), through increases in the proportion of dogs receiving excellent and good classifications.

CLINICAL RELEVANCE

Hip joint phenotype classifications can be used by dog breeders to develop breeding programs to improve the hip joints of future generations of dogs.

Prevalence of hip dysplasia, elbow dysplasia and humeral head osteochondrosis in dog breeds in Belgium

The official screening results of the Belgian National Committee for Inherited Skeletal Disorders, an affiliate of the Belgian Kennel Club, have been used to estimate the prevalence of hip dysplasia, elbow dysplasia and humeral head osteochondrosis in the dog breeds in Belgium, and these have been compared with reported prevalence data from other countries. In some breeds, the prevalence of hip and elbow dysplasia is very high, both in Belgium and in other countries. Comparisons of the prevalence of hip dysplasia are not always feasible because different systems are used to evaluate the quality of the hips and because there is no strict consensus on what should be considered a diseased hip joint.

Impact of sedation method on the diagnosis of hip and elbow dysplasia in Swedish dogs

Our objective was to investigate the effect of sedation method on the screening result for hip and elbow dysplasia. The study was based on a questionnaire survey of routines for hip and elbow screening at Swedish veterinary clinics and results of hip and elbow status, for eight breeds (Bernese Mountain Dog, Boxer, German Shepherd Dog, Golden Retriever, Labrador Retriever, Newfoundland, Rottweiler, and Saint Bernard) recorded by the Swedish Kennel Club. In total 5877 and 5406 dogs examined for hip and elbow dysplasia, respectively, from January 2002 through March 2003 were included. We used logistic regression to examine whether the type of chemical restraint used for sedation affected the screening result for hip and elbow dysplasia. In addition to sedation method, the effects of veterinary clinic, sex, breed, and age at screening were studied. The type of chemical restraint used for sedation affected the screening result for hip but not for elbow dysplasia. Acepromazine gave less than half the odds of hip dysplasia compared with medetomidine and butorphanol (the most common method), medetomidine alone or xylazine. Females had about 25% higher odds for developing hip dysplasia whereas males had almost 40% higher odds for developing elbow dysplasia. Saint Bernard, Newfoundland and German Shepherd Dog had the highest odds of developing hip dysplasia, whereas Rottweiler and Labrador Retriever had the lowest odds. Boxer had the lowest risk for elbow dysplasia, followed by Labrador Retriever. Saint Bernard and Rottweiler had the highest odds of elbow dysplasia. Increasing age increased the odds of both hip and elbow dysplasia, by about 2.5% per month. Following the results in this study, recording of the type of chemical restraint used for sedation during hip screening has now become mandatory in Sweden. This makes it possible to account for the effect of sedation method in a model for prediction of breeding values for hip dysplasia.

The use of a genetic-counselling program by Dutch breeders for four hereditary health problems in boxer dogs

Our group developed a genetic-counselling program for boxer-dog breeders in The Netherlands, using data for cryptorchidism (uni- and/or bilateral), epilepsy, knee-problems (including ligament rupture, fractured or ruptured meniscus, severe osteo-arthrosis of the knee, or a combination of these disorders), and schisis (including cheiloschisis, palatoschisis, or cheilopalatoschisis). We transformed the estimated breeding values (EBVs) into odds ratios (ORs), to enable the breeder to compare the risk for each of the traits for a certain dam-sire combination with the average population risk (set at 1). The goal of the study was to evaluate the use of our genetic-counselling program by Dutch breeders of boxer dogs. We asked breeders of the Dutch Boxer Club to send in an application form for genetic-counselling from June 1 to December 1, 2000. Breeders indicated on this application form three desirable sires for their dam (sire 1, sire 2, sire 3) in random order. On the basis of this information, a counselling report was produced which included ORs for the four diseases in litters of the dam-sire combinations indicated on the application form. Together with the counselling report, the breeders received an evaluation form. We received 129 application forms from 70 breeders, and collected 125 evaluations. Of these evaluations, 96 were informative about the influence of the counselling report on sire choice. The most-important criteria used by breeders to select sires were: the exterior characteristics (60%) and known progeny (52%). Although it was the first time breeders could make use of genetic-counselling, 32% of the breeders indicated that the genetic-counselling played a major role in their sire selection. Breeders expressed little difference in importance for the four genetic traits, but there was a tendency to consider epilepsy more than the others. Breeders hesitated to put long-term population interest above short-term personal interest. Nevertheless, the general conclusion of this study is that breeders acknowledge the value of counselling, especially to reduce the frequency of a threatening disease such as epilepsy.

Heritability and epidemiology of canine hip-dysplasia score and its components in Labrador retrievers in the United Kingdom

Hip-dysplasia (malformation of the coxofemoral joint) in dogs is a major health problem. Under the British Veterinary Association/Kennel Club's voluntary hip-dysplasia scheme, dog-owners/breeders submit radiographs from animals >1-year-old, to ensure adequate skeletal maturity. An overall hip score quantifies the degree of malformation in the hip joints of these animals, by summing the scores for nine components of the radiographs of both the left and right joints. The hip score data for 29,610 Labrador retrievers (registered with The Kennel Club, UK) were merged with the Kennel Club pedigree database for 472,435 Labrador retrievers. The merged data included the animal's identity, date of birth, sex and hip score and similar records for the dog's relatives, including the hip score if the relative had been tested. In recent years, breeding had been increasingly from tested parents. The mean hip score for male Labradors was significantly higher than that for females. Regression modelling showed a significant, positive dependence of the hip score of the offspring upon the hip scores of its sire, dam and grandparents. Genetic heritability (using data from 13,382 Labrador retrievers comprising 718 litters) was highly significant: 0.34 from the two parents, 0.41 from sire alone and 0.30 from dam alone. Using components data from 2038 offspring Labrador retrievers comprising 1248 litters, three similar estimates of heritability were significant for three major components (Norberg angle, cranial acetabular edge and subluxation); for other components, heritability was significant from the sire but not from the dam. Offspring hip score could be reduced substantially by using only parents with zero hip score.

Quantitative genetics of traits associated with hip dysplasia in a canine pedigree constructed by mating dysplastic Labrador Retrievers with unaffected Greyhounds

OBJECTIVE

To determine the genetic influence on expression of traits associated with canine hip dysplasia.

ANIMALS

193 dogs from an experimental canine pedigree.

PROCEDURE

An experimental canine pedigree was developed for linkage analysis of hip dysplasia by mating dysplastic Labrador Retrievers with nondysplastic Greyhounds. A statistical model was designed to test the effects of Labrador Retriever and Greyhound alleles on age at detection of femoral capital epiphyseal ossification, 8-month distraction index, and 8-month dorsolateral subluxation score.

RESULTS

The additive effect was significant for age at detection of femoral capital epiphyseal ossification. Restricted maximum likelihood estimates (+/-SD) for this trait were 6.4+/-1.95, 10.2+/-2.0, 10.8+/-3.1, 11.4+/-2.1, and 13.6+/-4.6 days of age for Greyhounds, Greyhound backcross dogs, F1 dogs, Labrador Retriever backcross dogs, and Labrador Retrievers, respectively. The additive effect was also significant for the distraction index. Estimates for this trait were 0.21+/-0.07, 0.29+/-0.15, 0.44+/-0.12, 0.52+/-0.18, and 0.6+/-0.17 for the same groups, respectively. For the dorsolateral subluxation score, additive and dominance effects were significant. Estimates for this trait were 73.5+/-4.1, 71.3+/-6.5, 69.1+/-6.0, 50.6+/-12.9, and 48.4+/-7.7%, respectively, for the same groups.

CONCLUSIONS

In this canine pedigree, traits associated with canine hip dysplasia are heritable. Phenotypic differences exist among founder dogs of each breed and their crosses. This pedigree should be useful for identification of quantitative trait loci underlying the dysplastic phenotype.

Comparison of three radiographic methods for diagnosis of hip dysplasia in eight-month-old dogs

OBJECTIVE

To compare the accuracy of the extended-hip radiographic (EHR) score, the distraction index (DI), and the dorsolateral subluxation (DLS) score for identifying hip dysplasia in dogs at 8 months of age.

DESIGN

Cohort study

ANIMALS

129 Labrador Retrievers, Greyhounds, and Labrador Retriever-Greyhound crossbreds.

PROCEDURE

Radiography was performed when dogs were 8 months of age. Dogs were euthanatized at 8 to 36 months of age; hip dysplasia was diagnosed at the time of necropsy on the basis of results of a gross examination of the articular cartilage of the hip joints for signs of osteoarthritis.

RESULTS

The EHR score, DI, and DLS score at 8 months of age were all significantly correlated with degree of cartilage degeneration at necropsy. Sensitivity and specificity of using EHR score at 8 months of age to diagnose hip dysplasia (scores > 3 were considered abnormal) were 38 and 96%, respectively; sensitivity and specificity of using DI (values > 0.7 were considered abnormal) were 50 and 89%; and sensitivity and specificity of using DLS score (scores < 55% were considered abnormal) were 83 and 84%.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that specificities of the 3 methods for diagnosing hip dysplasia in dogs at 8 months of age were similar. However, the DLS score had higher sensitivity, indicating that there were fewer false-negative results.

Heritability estimations for diseases, coat color, body weight, and height in a birth cohort of Boxers

OBJECTIVE

To obtain heritability estimates for diseases and characteristics in Boxers.

ANIMALS

Birth cohort of 2,929 purebred Boxers from 414 litters.

PROCEDURE

Heritability estimates were determined for cheiloschisis-palatoschisis, cryptorchidism, epilepsy, stifle disorders, cardiac disorders, coat color, birth weight, and adult weight, and height. Binary traits were analyzed by use of a mixed-effects probit model. Some traits also were analyzed by use of a model that postulated monogenic inheritance. Full pedigree analyses were performed. Variation in incidences of disease among clusters of related dogs was evaluated.

RESULTS

Heritability estimates were virtually zero for cardiac disorders, medium (0.17 to 0.36) for most other traits, and high (> 0.55) for coat color, birth weight, and adult height. Litter effects and risk factors affected cheiloschisis-palatoschisis, heart murmur, coat color, broadly defined epilepsy, and adult weight. Litter effects may be attributable to common environmental effects for littermates but also may be attributable to dominance variation caused by a recessive gene. Heritability estimates increased when stricter definitions for epilepsy and stifle disorders were used. The monogenic model did not reveal higher heritability estimates for 6 traits analyzed. Incidences for white coat differed significantly for 10 familial clusters, confirming high heritability and effects of familial lineage.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that genetic improvement of most traits should be feasible, except for cardiac disorders. However, because most traits are influenced by environmental effects as well as genetic effects, genetic counseling based on polygenic inheritance and use of familial information rather than strict exclusion of parents is preferred.

Heritability of canine hip-dysplasia score and its components in Gordon setters

Hip dysplasia (malformation of the hip joint) is an important health problem in dogs. The condition and the control scheme for Gordon Setters was organised by the British Veterinary Association (BVA) and the Kennel Club before 1976 and use hip scores. Our analyses of hip dysplasia in Gordon Setters used both hip scores and the scores for the nine components (which collectively defined the hip score). The scores for all nine components were available for 732 females and 420 males. These clinical data were merged with the Kennel Club pedigree database (animal's identity, date of birth, and also similar data for its parents, including hip scores if the parent had been tested). Regression models showed strong positive relationships between offspring and parental hip scores as well as for some component scores. The heritability of hip dysplasia (assessed using both hip scores and the major components) was significant, particularly from dams. Our research emphasizes the need for both sires and dams--particularly dams, to have zero or small hip scores. Tested parents have been used increasingly in recent years, but greater reduction in offspring hip score will require stricter selection of potential breeding stock. The models reported here provide quantitative predictions of likely health benefits from selective breeding.

Heritability and epidemiology of canine hip-dysplasia score in flat-coated retrievers and Newfoundlands in the United Kingdom

Hip dysplasia (malformation of the coxofemoral joint) in dogs is a major health problem for which the British Veterinary Association (BVA) had set up a control scheme in 1965. Based on scoring nine components of the radiographs of both the left and right joints, the degree of hip joint malformation is now quantified by an overall hip score (a measure of the condition of the hip joint). The hip scores of 1258 flat-coated retrievers and 1566 Newfoundlands (registered with The Kennel Club in the United Kingdom) were analysed after merging with Kennel Club pedigree data for 19036 flat-coated retrievers registered by 1995 and 14336 Newfoundlands registered by 1997. The merged data included the animal's identity, date of birth, sex and hip scores and also similar records for the dog's relatives including the hip score if the relative had been tested. In recent years, breeding has been increasingly from tested parents. There has been some reduction in offspring hip scores - presumably because breeders avoided breeding from males with very high scores. However, a much greater reduction in offspring hip score would be achieved by stricter science-based selection of potential sires and dams. Regression modelling quantified the positive relationship between offspring and parental hip scores. The genetic heritability of hip scores was large and significant in both breeds (particularly from dams). The breeders in UK tended to use healthy sires for breeding but they have taken less care in selecting dams. Our regression models emphasise the need for both sires and dams, particularly dams, to be healthy with very small hip scores.

Attitudes of Finnish dog-owners about programs to control canine genetic diseases

A mailed questionnaire survey was done to study dog-owners' knowledge of canine inherited diseases and the present screening and control programs in Finland, as well as to study the importance of health-related matters and well-being to dog-owners. The purpose was also to study the owners' role in programs and the influence of health and well-being in their decision-making process and choices when purchasing a puppy. This study showed that dog-owners highly valued health-related matters and well-being. The present programs were considered to have a positive effect on the prevention of canine inherited diseases. Dog-owners estimated that their own knowledge could be better but they believed in veterinarians' and dog-breeders' ability to inform them. Inherited skeletal and ocular diseases were thought to be important to canine well-being; the importance of other diseases or behaviour problems was assessed to be lower. In choosing a suitable breed, behaviour and temperament were the most-important factors but health-related matters were essential in actually choosing a puppy's breeder and the litter. Well-being and health were also considered very important to the image of the dog hobby.

Attitudes of Finnish dog-breeders about programs to control canine genetic diseases

A questionnaire was mailed to 320 Finnish dog-breeders to study breeders' knowledge of canine inherited diseases and of the present screening and control programs in Finland. The purpose was also to study the breeders' attitudes about and compliance with such programs. Breeders estimated that their knowledge was quite good, and they also believed in their ability to influence other groups and to promote the programs. The present programs were considered to have a positive effect on the prevention of canine inherited diseases, but information given to breeders and other key groups could produce even better results. Inherited skeletal and ocular diseases were thought to be important to canine well-being; the importance of other diseases was assessed to be lower.

Factors affecting hip dysplasia in German shepherd dogs in Finland: efficacy of the current improvement programme

Hip dysplasia records from 10,335 German shepherd dogs were used to estimate environmental effects and predict breeding values and genetic change achieved with the Finnish Kennel Club's breeding programme. The best linear unbiased prediction (BLUP) procedure was used for the analysis. No clear genetic improvement could be found during the study period (1985 to 1997). This might be due to ineffective selection for good hips. Significant environmental effects included year and month of birth, panellist, screening age and the effect of the genetic group of offspring from imported versus non-imported sires. In order to make the breeding programme more effective, BLUP breeding values should be used instead of phenotypic selection.