Estimation of heritability for hip dysplasia in German Shepherd Dogs in Finland

The heritability of hip dysplasia in the German Shepherd Dog was estimated by applying the animal model and the Restricted Maximum Likelihood (REML) method to a data-set which consisted of the hip scores of 10 335 dogs. Fixed effects of the model were the month and the year of birth, screening age, the panelist responsible for screening and the origin of the animal's sire. The litter and the breeder had only minor effects on hip joints. Heritability estimates were moderate (0.31–0.35). The moderate heritability, which was found in this study, enables a much better genetic gain in the breeding programme, if proper evaluation methods, such as BLUP animal model, and effective selection is used instead of phenotypic selection.     

Estimation of heritability for hip dysplasia in German Shepherd Dogs in Finland

The heritability of hip dysplasia in the German Shepherd Dog was estimated by applying the animal model and the Restricted Maximum Likelihood (REML) method to a data‐set which consisted of the hip scores of 10335 dogs. Fixed effects of the model were the month and the year of birth, screening age, the panelist responsible for screening and the origin of the animal's sire. The litter and the breeder had only minor effects on hip joints. Heritability estimates were moderate (0.31–0.35). The moderate heritability, which was found in this study, enables a much better genetic gain in the breeding programme, if proper evaluation methods, such as BLUP animal model, and effective selection is used instead of phenotypic selection.     

A radiographic stress technique for evaluation of coxofemoral joint laxity in dogs

OBJECTIVE: To develop a radiographic stress technique to quantify hip joint laxity in dogs. STUDY DESIGN: Prospective study on client-owned dogs presented for hip dysplasia screening. ANIMAL POPULATION: 302 nonselected dogs (63 breeds). METHODS: Dogs were sedated and placed in dorsal recumbency. During pelvic radiography, the femoral heads were displaced manually in a craniodorsal direction. On these stress radiographs, the degree of lateral displacement of the femoral heads was assessed in terms of a subluxation index (SI) and compared with the degree of femoral head subluxation and the severity of hip dysplasia found on conventional extended hindlimb radiographs. RESULTS: The degree of subluxation on stress radiographs was significantly greater than on conventional radiographs. Correlation between the severity of canine hip dysplasia (CHD), graded according to conventional techniques, and the degree of subluxation, induced by radiographic stress technique, was positive (r = .57; P<.0001). Two critical SI values were noted. Of the dogs with an SI value of 0.3 or less, 99% were classified as CHD grade normal, borderline, or mildly dysplastic. In dogs with an SI value between 0.3 and 0.5, CHD grading ranged from normal to severely dysplastic. Of the dogs with an SI value greater than 0.5, 95% had dysplastic hip joints. CONCLUSIONS: Hip joint laxity cannot be quantified precisely on standard position radiographs. The proposed stress technique yields significantly higher degrees of femoral head subluxation than the standard position.     

Multivariate genetic analysis of canine hip and elbow dysplasia as well as humeral osteochondrosis in the Bernese mountain dog

In the present study genetic parameters for canine hip dysplasia (CHD), canine elbow dysplasia (CED) and osteochondrosis dissecans of the humeral head (OCD) were analysed in Bernese mountain dogs. The data set included the official scores for CHD and CED from 5534 Bernese mountain dogs born in the years 1995-2008. A multivariate linear animal model was employed to estimate heritabilities, additive genetic and residual correlations using residual maximum likelihood (REML). Heritability estimates were h2 = 0.26 for CHD, h2 = 0.22 for CED and h2 = 0.40 for OCD. The additive genetic correlation between CHD and CED was 0.31, between CHD and OCD 0.25, and between CED und OCD -0.49. A further multivariate analysis of the prevalence of the FCP (fragmented coronoid processus), CHD and OCD revealed a heritability of h2 = 0.59 for FCP. The additive genetic correlations among FCP and CHD as well CED except FCP were positive, but negative with OCD. Multivariately estimated breeding values will lead to higher genetic progress because the correlation structure of the traits can be taken into account and possible genetic antagonisms among traits are better reflected in the breeding values.     

Canine hip dysplasia: study of heritability in 401 litters of German Shepherd dogs

Heritability of hip dysplasia was estimated to be about 0.4 to 0.5 when based on the radiographic evaluations of the hip joints of 2,404 German Shepherd Dogs born at The Armed Forces Dog Training Center in Sweden. The material included all dogs in 401 litters born at the Center from 1965 through 1973 that reached the age of 15 months. To be expected with such high heritability, frequency of hip dysplasia in the offspring was shown to be affected by the hip joint status of sire and dam as well as by the hip joint status of their parents and littermates. Even matings between sires with normal hip joints and dams with only slight dysplasia resulted in significantly higher frequency of hip dysplasia in the offspring, when compared with the frequency if both sires and dams had normal hip joints. Frequency of hip dysplasia in the progeny of sires with normal hip joints varied greatly. Since 1973, selection of the breeding stock has been based on hip joint status (phenotype) of the breeding animals and of their relatives as well as on what had become known about frequency of hip dysplasia in the litters already born (progeny testing). In this way, frequency of hip dysplasia in 347 dogs born at the Center during 1975 was lowered to 28%. This figure should be compared with the figure of 50%, which represents the frequency of hip dysplasia in the kennel up to 1970, when selection was not as strict as could be expected in a well-controlled kennel.     

Comparison of arthroscopic and radiographic abnormalities in the hip joints of juvenile dogs with hip dysplasia

OBJECTIVE: To compare radiographic and arthroscopic abnormalities in juvenile dogs with clinically apparent hip dysplasia. DESIGN: Case series. ANIMALS: 52 dogs (70 hip joints) with clinical signs of hip dysplasia scheduled to undergo triple pelvic osteotomy. PROCEDURE: A ventrodorsal radiographic projection of the pelvis was evaluated by a radiologist unaware of clinical and arthroscopic findings, and radiographic osteoarthritic abnormalities were judged and scored as absent (0), mild (1), moderate (2), or severe (3). Arthroscopy was performed by a surgeon unaware of clinical and radiographic findings, and arthroscopic abnormalities were graded from 0 (normal) to 5 (exposed, eburnated subchondral bone). RESULTS: In 30 of the 70 (43%) hip joints, no radiographic osteoarthritic abnormalities were seen. Severe, full-thickness articular cartilage lesions (grade 4) of the femoral head or acetabulum were seen arthroscopically in 14 (20%) joints. Lesions > or = grade 2 were seen in 60 (86%) joints. Partial tearing of the ligament of the femoral head was present in 57 (81%) joints, and complete rupture was seen in 5 (7%). Radiographic abnormalities were seen in 13 of the 14 (93%; 95% confidence interval, 66% to 99.8%) joints with grade 4 arthroscopic abnormalities but in only 23 of the 46 (50%; 95% confidence interval, 35% to 65%) joints with grade 2 or 3 arthroscopic abnormalities. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that radiography is not a sensitive method for identifying moderate cartilage lesions in juvenile dogs with hip dysplasia. If moderate cartilage lesions are an important prognostic indicator for the success of triple pelvic osteotomy, then methods other than radiography should be used to detect these lesions.     

Estimates of genetic parameters for hip and elbow dysplasia in Finnish Rottweilers

Data from 2,764 Rottweiler dogs born from 1987 to 1996 were analyzed with a Restricted Maximum Likelihood procedure using a mixed linear animal model to obtain variance component estimates for hip and elbow dysplasia. The data included 2,764 hip dysplasia and 2,278 elbow dysplasia records. Hip joints were scored as normal (0), borderline (1), slight (2), moderate (3), and severe (4, 4.5, and 5) hip dysplasia. Elbow joints were graded normal or borderline (0), slight (1), moderate (2), and severe (3) elbow dysplasia. The mean for the hip scores was 1.07 and for the elbow scores .60. Environmental effects influencing hip dysplasia were age, birth year, birth year x season interaction, and experience of the veterinarian responsible for x-raying the dog. For elbow dysplasia, statistically significant effects were age, birth year, sex of the dog, and panelist responsible for each screening. Estimates of heritability for hip and elbow dysplasia were .58 +/- .04 and .31 +/- .04, respectively, with a genetic correlation of .37 +/- .08 between the traits. Genetic improvement of almost one genetic standard deviation was observed in both traits during the 10 yr covered by the data.     

Genetic analyses of elbow and hip dysplasia in the German shepherd dog

Results from radiographic screening for canine hip dysplasia (CHD) and elbow dysplasia (CED) of 48 367 German shepherd dogs born in 2001–07 were used for the population genetic analyses. Available information included CHD scores for 47 730 dogs, CED scores for 28 011 dogs and detailed veterinary diagnoses of primary ED lesions for a subsample of 18 899 dogs. Quasi‐continuous traits were CHD, CED and cases of CED without radiographically visible primary lesion (CED‐ARTH). Binary coding was used for fragmented medial coronoid process of the ulna (FCP), borderline findings and mild to severe signs of dysplasia in hip and elbow joints. Genetic parameters were estimated in univariate threshold and multivariate linear and mixed linear‐threshold models using Gibbs sampling. Correlations between univariately predicted breeding values (BV) indicated genetic differences between borderline and affected disease status for both CHD (r_BV = 0.5) and CED (r_BV = 0.3). Multivariate genetic analyses with separate consideration of borderline findings revealed moderate heritabilities of 0.2–0.3 for the quasi‐continuous traits with positive additive genetic correlation of 0.3 between CHD and both CED and CED‐ARTH. For FCP, heritability of 0.6 and additive genetic correlations of +0.1 to CHD and ?0.1 to CED‐ARTH were estimated. Results supported the relevant genetic determination of CHD and CED, argued for both diseases against interpretation of borderline findings as healthy and implied genetic heterogeneity of CED. Accordingly, future breeding strategies to reduce the prevalences of CHD and CED in the German shepherd dog should be most efficient when based on BV from multivariate genetic evaluation for CHD, CED‐ARTH and FCP with use of the whole scale of categories for classification of CHD and CED.     

Relationships among measurements obtained by use of computed tomography and radiography and scores of cartilage microdamage in hip joints with moderate to severe joint laxity of adult dogs

OBJECTIVE: To evaluate correlations among measurements on radiographic and computed tomography (CT) images with articular cartilage microdamage in lax hip joints of dogs. ANIMALS: 12 adult mixed-breed hounds. PROCEDURES: Pelvic CT and radiography were performed. Hip joints were harvested following euthanasia. Orthopedic Foundation for Animals (OFA) and PennHIP radiograph reports were obtained. Norberg angle (NA) and radiographic percentage femoral head coverage (RPC) were determined. Center-edge angle (CEA), horizontal toit externe angle (HTEA), ventral acetabular sector angle (VASA), dorsal acetabular sector angle (DASA), horizontal acetabular sector angle (HASA), acetabular index (AI), and CT percentage femoral head coverage (CPC) were measured on 2-dimensional CT images. Femoral head-acetabular shelf percentage was measured on sagittal 3-dimensional CT (SCT) and transverse 3-dimensional CT (TCT) images. Light microscopy was used to score joint cartilage. Relationships of OFA confirmation and PennHIP osteoarthritis scores with radiography, CT, and cartilage variables and relationships of cartilage scores with radiography and CT measurements were evaluated with Spearman rank correlations. Pearson correlation was used for relationships of distraction index (DI) with radiography, CT, and cartilage variables. RESULTS: Significant relationships included PennHIP osteoarthritis score with cartilage score, CEA, HTEA, DASA, AI, CPC, and TCT; OFA confirmation score with cartilage score, NA, RPC, CEA, HTEA, DASA, AI, CPC, and TCT; cartilage score with NA, RPC, CEA, HTEA, DASA, HASA, AI, and TCT; and DI with cartilage score, CEA, HTEA, DASA, HASA, AI, and CPC. CONCLUSIONS AND CLINICAL RELEVANCE: CT appeared to be a valuable imaging modality for predicting cartilage microdamage in canine hip joints.     

Estimation of genetic parameters for radiographic signs of hip dysplasia in Labrador Retrievers

The aim of this study was the analysis of environmental factors and estimation of genetic parameters for hip dysplasia in Labrador Retrievers. We analysed hip dysplasia scores of 2970 dogs from the official screening programme of the Labrador Club Deutschland (LCD) according to the FCI protocols. Traits evaluated were HD-Mit (average value of HD scores), HD-Max (higher score of both hip joints), HD-LI and HD-RE (HD score of the left or right hip joint). A linear animal model was employed to estimate heritabilities, additive genetic and residual correlations using Residual Maximum Likelihood (REML). Only inbreeding was significant after testing all non-genetic effects. Higher inbreeding coefficients were associated with higher HD scores. Heritability estimates and their standard errors were 0.38 +/- 0.04 for HD-Mit, 0.40 +/- 0.04 for HD-Max, 0.33 +/- 0.03 for HD-LI and 0.38 +/- 0.04 for HD-RE. The additive genetic correlation between HD-LI and HD-RE was 1. Heritability for female dogs was 0.31 and 0.30 for male dogs. The analysis of HD scores of Labrador Retrievers showed that the highest HD score of the hips should be used in breeding programmes, that heritabilities are not different among females and males, and that genetic components are much more important than environmental factors.     

Effect of dam and sire qualitative hip conformation scores on progeny hip conformation

OBJECTIVE: To determine in dogs what effect using hip conformation scores assigned by the Orthopedic Foundation for Animals (OFA) as a criterion for breeding selections would have on hip conformation scores of the progeny. DESIGN: Longitudinal study. ANIMALS: English Setters, Portuguese Water Dogs, Chinese Shar-peis, and Bernese Mountain Dogs for which OFA hip conformation scores were known. PROCEDURE: Pedigree data were obtained from the national breed clubs and the American Kennel Club and merged with data from the OFA hip conformation score database. An ANOVA was used to evaluate the effects of sex, age at the time of radiographic evaluation, and year of birth on the variation in hip conformation scores among the progeny. Heritability was estimated by use of within-year midparent offspring regression analyses. RESULTS: Significant differences in progeny hip conformation scores between sexes were not detected, but age at the time of radiographic evaluation and year of birth had a significant effect on hip joint conformation of the progeny. Estimated heritability (mean +/- SE) was 0.26 +/- 0.03, and dam and sire hip conformation scores had a significant effect on progeny hip conformation scores. Annual decreases in percentage of dysplastic progeny and increases in percentages of progeny and breeding dogs with phenotypically normal hip joint conformation were detected. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that hip conformation scores have moderate heritability in dogs and selection of breeding stock with better hip conformation scores will increase the percentage of progeny with phenotypically normal hip joint conformation.     

Genetic analysis of three different classification protocols for the evaluation of elbow dysplasia in German shepherd dogs

OBJECTIVES: Three different scoring systems for elbow dysplasia and its radiographic signs were genetically evaluated in 2645 German shepherd dogs. METHODS: An animal model was used to estimate heritabilities and additive genetic and residual correlations for the three scoring systems: ED-SV, which is recommended by the International Elbow Working Group; ED-LA, developed by Lang and others; and ED-TH, proposed by Tellhelm. RESULTS: The effects of sex, age at examination and the correlation between the two factors were significant for all three scoring systems. Heritability estimates (se) were 0.18 (0.04) for ED-SV, 0.11 (0.03) for ED-LA and 0.16 (0.04) for ED-TH. The additive genetic correlations among the different single criteria for elbow dysplasia and the different elbow dysplasia scores were between 0.68 and 0.98, except for the criteria ununited anconeal process and osteochondrosis dissecans of the trochlea humeri, which were mostly genetically negatively correlated to the other radiological criteria. CLINICAL SIGNIFICANCE: The elbow dysplasia scores were determined by two genetically different traits. The possibilities for selecting German shepherd dogs with respect to elbow dysplasia might be improved by taking into account these two traits in the prediction of breeding values.     

Static and dynamic ultrasonography for the early diagnosis of canine hip dysplasia

Objective : To determine the feasibility of sonographical examination of hip joints in non-sedated puppies and to assess the value of static and dynamic ultrasonography for the early diagnosis of canine hip dysplasia (CHD). Methods : Prospective study was carried out. Five hundred and sixty-six puppies between the ages of 16 and 49 days underwent sonographical determination of the α-angle, joint laxity and distraction value (DV). Sonographical parameters were correlated to conventional radiographic CHD classification in the adult dogs. Results : α-Angles between 74° and 89° (X ±sd=82·8°±2·31°) were measured. Despite the feasibility of sonographical hip assessment in puppies, no statistically significant correlation was found between sonographical determinations of the α-angle, joint laxity, DV and conventional radiographic hip joint classification at the age of 12 to 24 months. Clinical Significance : Results of our study suggest that static and dynamic ultrasonography of hip joints in puppies between 16 and 49 days of age is technically feasible but cannot be recommended for detecting puppies that will develop CHD between the ages of 12 and 24 months.     

Symmetry of hip dysplasia traits in the German Shepherd Dog in Australia

Canine hip dysplasia (CHD) is a common and debilitating developmental condition of the canine coxofemoral (hip) joint, exhibiting a multifactorial pattern of inheritance. British Veterinary Association hip traits (BVAHTs) are nine radiographic features of hips used in several countries to ordinally score both the right and left hip of potential breeding candidates to assess their suitability for breeding. The objective of this study was to examine some aspects of the relationship between contralateral scores for each BVAHT in a cohort of 13 124 Australian‐registered German Shepherd Dogs. Goodman and Kruskal gamma coefficients of 0.48–0.95 and correlation coefficients of 0.50–0.74 demonstrate that the association between right and left hip scores varies between moderate and strong for BVAHTs. Principal component analysis of scores detected a sizeable left‐versus‐right effect, a finding supported by symmetry and quasi‐symmetry analyses which found that seven of the nine BVAHTs display significant marginal asymmetry. Dogs showing asymmetry for one BVAHT are significantly more likely to display asymmetry at other BVAHTs. When asymmetry is expressed as a binary trait (either symmetrical or asymmetrical), it displays low to moderate heritability. Estimates of genetic correlations between right and left scores are very high for all BVAHTs (>0.945), suggesting right and left scores for each BVAHT are largely determined by the same set of genes. The marginal asymmetries are therefore more likely to be of environmental and non‐additive genetic origin. In breeding programmes for CHD, we recommend that scores from both hips be used to estimate breeding values, with a term for side‐of‐hip included in the model to account for score variation owing to asymmetry.     

Dorsolateral Subluxation of Hip Joints in Dogs Measured in a Weight-Bearing Position With Radiography and Computed Tomography

Objective —To develop a radiographic procedure to measure dorsolateral subluxation (DLS) of the femoral head in canine coxofemoral (hip) joints in a weight-bearing position. Study Design —DLS measured on a radiographic projection was compared with DLS measured on computed tomography (CT) images of hip joints in a weight-bearing position. Animals —A total of 24 dogs of varying ages were examined including Labrador retrievers, greyhounds, and Labrador-greyhound crossbreeds. Methods —Anesthetized dogs were placed in sternal recumbency in a kneeling position in a foam rubber mold. The stifles were flexed and adducted with the femora perpendicular to, and in contact with, the table. To test for DLS, dogs were imaged in this weight-bearing position (DLS test) with routine radiography and CT. For each hip, the DLS score was determined by measuring the percentage of the femoral head medial to the lateralmost point of the cranial acetabular rim on the dorsoventral radiographic projection and the lateralmost point of the central, dorsal acetabular rim on the CT image. Higher DLS scores indicated better coverage of the femoral head by the acetabulum. DLS scores were compared with the distraction index (DI) by grouping joints according to their probability of developing osteoarthritis (OA) as predicted by the DI. Results —The DLS score in the new position ranged from 29% to 71% for radiography and 15% to 59% for CT. Joints classified as OA unsusceptible had a mean score of 64%± 1.5% for radiography and 55%± 0.8% for CT (n = 10); hip joints having a high probability of developing OA had a score of 39%± 2.6% for radiography and 26%± 1.9% for CT (n = 8). When the DLS test was repeated on the same dogs at a different time, the intraclass correlation coefficient for the DLS score on the radiographs was 0.85 (left hip) and 0.89 (right hip). There was a strong correlation (r = .89 for both hips) between the DLS score measured on the weight-bearing radiograph and the CT image. A strong correlation also was observed between the DLS score and the DI (r = -.87). The DLS scores for OA unsusceptible joints and joints with a high probability of developing OA were significantly different (P < .05). Conclusions and Clinical Relevance —The DLS test can be performed with CT or routine radiography to measure variable amounts of DLS in weight-bearing hip joints oriented similarly to those of a standing dog. After additional long-term follow-up studies evaluating the development of OA and breed effects are performed, the DLS method may prove useful in studies of normal and abnormal hip joint development related to canine hip dysplasia.     

Clinical and Radiographic Evaluation of Intertrochanteric Osteotomy in Dogs: A Retrospective Study of 18 Dogs

Objective- To determine whether intertrochanteric osteotomy (ITO) can prevent the progression of degenerative joint disease (DJD) in dysplastic hip joints.
Study Design- The results of ITO were assessed retrospectively by using owner questionnaires, physical examination, and radiographic evaluation.
Animals- Eighteen client-owned dogs (29 coxofemoral joints were evaluated).
Methods- Lameness was scored according to a grading system. A scoring system was also developed to assess radiographically evident osteoarthritis on a ventrodorsal projection of the coxofemoral joints in extension.
Results- Twenty-nine ITO were performed in 18 dogs with varying degrees of hip dysplasia. The dogs were lame on 19 of 29 rear limbs on physical examination before surgery. In 22 of the 29 hip joints, palpation caused signs of pain. The median age at the first and second surgical procedure was 14.5 months and 18 months, respectively. Follow-up evaluation was performed on average at 9.77 (FU I), 22.52 (FU II), and 47.50 months (FU in) after surgery. Based on the owners' evaluation, there was a tendency toward improvement after surgery. The results of the physical examination at the preoperative examination and at the three follow-up examinations did not differ significantly. The follow-up radiographic scores showed significantly worse DJD than the preoperative scores.
Conclusions- ITO does not prevent progression of DJD in the dysplastic hip.
Clinical Relevance- Knowledge of the long-term effects of ITO is essential for surgeons trying to achieve improvement in dogs with hip dysplasia.     

Long-term outcome of juvenile pubic symphysiodesis and triple pelvic osteotomy in dogs with hip dysplasia

OBJECTIVE: To compare long-term outcomes of juvenile pubic symphysiodesis (JPS) and triple pelvic osteotomy (TPO) in dogs with hip dysplasia. DESIGN: Prospective clinical trial. ANIMALS: 18 dogs with hip dysplasia (ie, distraction index > or = 0.5 in at least 1 hip joint and no, mild, or moderate radiographic evidence of degenerative joint disease [DJD]). PROCEDURES: Dogs between 4 and 5.5 months old at enrollment were assigned to undergo JPS, and dogs between 5 and 12 months old were assigned to undergo TPO. All dogs were reexamined at 2 years of age. RESULTS: At 2 years of age, there were no significant differences between groups in regard to lameness scores, angle of extension of the hip joints, distraction index, peak vertical force, acetabular angle, radiographic DJD score, or owner-assigned scores of clinical function. Dorsal acetabular rim angle was significantly higher in dogs that underwent JPS than in dogs that underwent TPO. For dogs that underwent TPO, dorsal acetabular rim angle was significantly decreased and acetabular angle was significantly increased at 2 years of age, compared with values obtained prior to surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that JPS and TPO have similar effects on hip joint conformation in dogs with moderate to severe hip dysplasia but that neither procedure eliminates the hip joint laxity characteristic of hip dysplasia or the progression of degenerative changes.     

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.     

Heritabilities and genetic correlations between fetlock,hock and stifle osteochondrosis and fetlock osteochondral fragments in Hanoverian Warmblood horses

The main objective of this study is to estimate genetic parameters for osteochondrosis (OC) and osteochondrosis dissecans (OCD) in fetlock, hock and stifle joints as well as for palmar or plantar osteochondral fragments (POFs) and dorsodistal osteochondral fragments (DOFs) in fetlock joints. For this purpose, the results of a standardized radiographic examination of 7396 Hanoverian Warmblood horses were used. Heritabilities and genetic correlations were estimated using residual maximum likelihood (REML) under a linear animal model. Heritability estimates for OC at the different joints were at 0.17–0.34, for OCD at 0.16–0.46, for POFs at 0.19 and for DOFs at 0.22 after transformation onto the liability scale. For osteochondral fragments (OFs), lower heritabilities were estimated, especially in fetlock joints. POFs were genetically negatively correlated with OC in each joint. The size of the heritability estimates indicates that the prevalence of these radiographic findings can be reduced by breeding measures. However, differentiation among the different clinical entities is crucial to avoid underestimation of heritabilities. The analysis of genetic parameters performed in this study indicates that OC and OCD in fetlock, OC and OCD in hock, OC and OCD in stifle joints, POFs of the hindlimbs and DOFs may be treated as different traits.     

Spondylosis deformans in the boxer: Estimates of heritability

This study presents the estimates of heritability for spondylosis deformans in the boxer based on 353 offspring from 24 randomly selected sires, each with at least three radiographically investigated offspring. The estimated heritability (h²) for maximum degree of osteophyte development was high, both when estimated by paternal half-sib correlation (0·42) and by the regression of offspring based on the parents (0·62). The heritability for the number of affected discs estimated by paternal half-sib correlation was also high (0·47). The estimate of heritability for the number of affected discs based on regression of offspring on the parents was lower at 0·13. All heritabilities had large standard errors. A positive phenotypic correlation between spondylosis deformans and hip dysplasia was observed. Assuming a significant portion of the correlation is genetic, this fact may permit selection against spondylosis deformans without negatively influencing the incidence of hip dysplasia. Since the incidence of spondylosis deformans is high even in young dogs, it should be possible to detect a large proportion of genetically predisposed animals by radiographic examination of the spine at one year of age; at the same time that dogs are presented for a routine test for hip dysplasia.