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.     

Growth dynamics of the canine proximal tibial physis

Objective: To determine growth of the proximal tibial physis in the Labrador Retriever, a breed of dog at risk for rupture of the cranial cruciate ligament (CCL). Animals: Male Labrador Retriever dogs (n=6). Methods: Tantalum markers (0.5 mm diameter) were implanted in the right proximal tibial epiphysis and metaphysis of each dog at 16 weeks of age. Lateral and craniocaudal radiographic projections of the tibia were made monthly and longitudinal growth was assessed from radiographs; a growth curve was generated from the data. Data from dogs that had undergone proximal tibial epiphysiodesis (PTE) was compared with the growth curve to demonstrate if the growth curve accurately predicted changes in the growth associated with this procedure. Results: Growth rate of individual dogs decreased slowly and non‐linearly over the 1st year of age. Growth from the proximal tibial physis is described. Conclusions: Growth of individual dogs described here follows the model of saltation and stasis. The growth curve generated predicted the change in tibial plateau angle (TPA) for two Labrador Retrievers that had PTE (±1°).     

Evaluation of results for Schirmer tear tests conducted with and without application of a topical anesthetic in clinically normal dogs of 5 breeds

OBJECTIVE: To evaluate, for clinically normal dogs, results of Schirmer tear tests in eyes without topical anesthetic (STT) and to detect differences associated with breed, sex, age, day, and time of day in eyes in which STT was performed after use of topical anesthetic (STTa). ANIMALS: 41 Beagles, 43 Labrador Retrievers, 25 Golden Retrievers, 26 English Springer Spaniels, and 22 Shetland Sheepdogs. PROCEDURE: Beagles had STT and STTa values measured twice daily for 5 days. Client-owned dogs of 4 other breeds had STT and STTa values measured once. RESULTS: Mean +/- SD values of Beagles for STT and STTa were 20.2 +/- 2.5 and 3.8 +/- 2.7 mm/min. Mean values for STT and STTa were as follows: Labrador Retriever, 22.9 +/- 4.1 and 9.6 +/- 3.8 mm/min; English Springer Spaniel; 20.7 +/- 3.2 and 5.4 +/- 3.4 mm/min; Golden Retriever, 21.8 + 3.7 and 8.8 +/- 3.1 mm/min; and Shetland Sheepdog, 15.8 +/- 1.8 and 3.6 +/- 2.8 mm/min. Overall mean values for STT and STTa were 20.2 +/- 3.0 and 6.2 +/- 3.1 mm/min. Differences for STT and STTa were detected among breeds, but significant differences were not associated with sex or age within each breed or in overall values for all dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results for the STT reported here compare favorably with reported values, except for results of Shetland Sheepdogs; however, results for the STTa differ dramatically from reported values. Clinicians should consider effects attributable to breed when evaluating results of STT and STTa in dogs.     

The geographic form of retinal dysplasia in dogs is not always a congenital abnormality

To examine the congenital nature of the geographic form of focal/multifocal retinal dysplasia, we carried out a retrospective analysis of the medical records of dogs produced in a closed colony of service dogs who receive very thorough ophthalmologic examinations early in their life, and later, when they return for training. Medical records were reviewed from all dogs produced by The Seeing Eye, Inc. between October 1991 and September 1998, and which had a diagnosis of geographic retinal dysplasia coded. We identified 23 dogs of five different breeds or interbreed crosses that comprise the breeding and production program (Golden Retrievers, German Shepherds, Labrador Retrievers, Labrador Retriever/Golden Retriever cross and German Shepherd/Labrador Retriever cross) in which the results of at least two complete ophthalmic examinations were documented, the first before 10 weeks of age, and the second when the dog was a young adult. Of the 23 dogs, only one was identified as affected with the geographic form of retinal dysplasia when examined at 5–6 weeks of age. The remaining dogs were normal. Our findings indicate that, in most cases, the geographic form of retinal dysplasia is not present in dogs prior to 10 weeks of age. These findings indicate the need to revise recommendations for early screening of dogs for retinal dysplasia.     

Clinical and pathologic findings in dogs with atherosclerosis: 21 cases (1970-1983)

Atherosclerosis was diagnosed on necropsy in 21 dogs in a 14-year period. Nine dogs died and 12 were euthanatized because of complications associated with the disease. The mean age was 8.5 +/- 0.5 years; 18 dogs were male. Three breeds (Miniature Schnauzer, Doberman Pinscher, and Labrador Retriever) had a higher prevalence of the disease than other breeds in the canine necropsy population of The Animal Medical Center. Most common clinical signs were lethargy, anorexia, weakness, dyspnea, collapse, and vomiting. Hypercholesterolemia, lipidemia, and hypothyroidism were common in affected dogs tested, and protein electrophoresis revealed high values for alpha 2 and beta fractions in all dogs tested. Electrocardiography indicated conduction abnormalities and myocardial infarction in 3 of 7 dogs. Necropsy revealed that affected arteries (including coronary, myocardial, renal, carotid, thyroidal, intestinal, pancreatic, splenic, gastric, prostatic, cerebral, and mesenteric) were yellow-white, thick and nodular, and had narrow lumens. Myocardial fibrosis and infarction also were observed in the myocardium. Histologically, affected arterial walls contained foamy cells or vacuoles, cystic spaces, mineralized material, debris with or without eroded intima, and degenerated muscle cells.     

Cutaneous neosporosis in two adult dogs on chronic immunosuppressive therapy.

Antemortem diagnosis of generalized ulcerative and pyogranulomatous dermatitis with numerous intralesional tachyzoites was made from skin biopsy specimens from 2 adult dogs on chronic immunosuppressive therapy. A 9-year-old Italian Greyhound was on long-term corticosteroid therapy for the treatment of a lupus-like systemic autoimmune disorder, and a 7-year-old Labrador Retriever had received several months of chemotherapy for lymphosarcoma. The tachyzoites were identified as Neospora caninum by immunoperoxidase immunohistochemistry. Both dogs were treated with clindamycin. Lesions in the Greyhound resolved; however, the Labrador Retriever was euthanized because of evidence of neuromuscular disease, despite improvement of the skin lesions. These 2 cases indicate that cutaneous neosporosis can occur in adult dogs on chronic immunosuppressive therapy. The disease may result from reactivation of a congenital infection and/or a recently acquired primary infection.     

Muscular dystrophy in dogs: does the crossing of breeds influence disease phenotype?

Golden Retriever (GR) muscular dystrophy is an inherited degenerative muscle disease that provides an excellent model for Duchenne muscular dystrophy in humans. This study defined the histopathologic lesions, including the distribution of type I and II muscle fibers (FTI and FTII), in 12 dystrophic and 3 nondystrophic dogs between 7 and 15 months of age. The authors were interested in studying the influence on disease phenotype from crossing the base GR breed with Yellow Labrador Retrievers. The dystrophic dogs were divided according to breed: GRs and Golden Labrador Retrievers (GLRs). On hematoxylin and eosin staining, histopathologic lesions were more severe in GRs than GLRs. Six of eight GR muscles (75%) had a severe lesion grade (grade 3). In contrast, seven GLR muscles (87.5%) had mild lesions (grade 2), and only one had severe lesions (grade 3). Changes in fiber-type distribution were more pronounced in GRs versus GLRs. FTI:FTII ratio inversion was observed in three dystrophic GRs but only one GLR. The mean diameter of FTI and FTII was smaller in GRs and GLRs than in nondystrophic dogs (P < .01). The FTI of five GR muscles (62.5%) were larger than those of GLRs, whereas only one GLR muscle was larger (P < .05). The differential was less pronounced for FTII, with four GR muscles being larger and three GLR being larger. Observations indicate that crossing the base GR breed with Labrador Retrievers lessened the severity of the GR muscular dystrophy phenotype.     

Right Atrioventricular Valve Malformation in Dogs and Cats: An Electrocardiographic Survey With Emphasis on Splintered QRS Complexes

The purposes of this study were 2-fold: (1) to determine the prevalence of splintered QRS complexes (Rr', RR', rR', rr') and other electrocardiographic abnormalities in dogs and cats with congenital right atrioventricular valve malformation (RAVM) and (2) to determine if the Labrador Retriever was at greater risk for RAVM and splintered QRS complexes. EKGs from 39 dogs and 6 cats with echocardiographically diagnosed RAVM were studied retrospectively. Splintered QRS complexes were commonly found in affected Labrador Retrievers (9 of 19, 47%), non-Labrador Retrievers (12 of 20, 60%), and cats (4 of 6, 67%). Right ventricular enlargement was most commonly detected by precordial leads (CV₆LL[V₂], CV₆LU[V₄]) in the dogs and by the standard limb leads in the cats. Arrhythmias were uncommon. The Labrador Retriever was significantly overrepresented (P < .001) in the RAVM group when compared to the general hospital population (50% versus 8%). Males were also significantly overrepresented ( P < .01). It was concluded that splintered QRS complexes are a distinctive and common electrocardiographic finding in dogs and cats with RAVM. Moreover, this congenital cardiac defect is most common in the Labrador Retriever, although this breed does not have proportionately more or less splintering of the QRS complexes than other breeds.     

The effects of growth and disease in serum keratan sulfate concentration in dogs

The purpose of this study is to investigate keratan sulfate (KS) concentration in the serum of puppies and the effects of age, body weight, breed and diseases. Serum samples from six neonatal dogs (4 Beagles, 2 Labrador Retrievers), and from 127 adult dogs with various diseases were collected at a Teaching Animal Hospital. Canine serum KS concentration was measured by inhibition enzyme-linked immunosorbent assay (ELISA). Samples from puppies were evaluated for growth-related changes, and samples from patients were evaluated for age, body weight, breed and disease-related changes. Serum KS concentration was high in puppies from birth to 4 months of age. KS values started to decrease from 4 months to 9 months of age, and then gradually reached to the plateau. Though in the small sample, mean KS concentration in a Labrador Retriever was higher than in Beagles during the first 10 months. The values of serum KS showed body weight-related increase within retrievers among teaching hospital population and there was significant increase in body weight-related change. Cartilage metabolism is high in canine immature joint and that activity continues for 5 months, and that higher in Labrador Retrievers rather than in Beagles. There was no effect from other factors, including age, body weight, breed and disease in all patients. Serum KS concentration of Retrievers is higher than Beagles, and that value increased with gain of body weight. We suggest that Retriever have higher cartilage metabolism with growth or ageing.     

Leucoencephalomalacia and Cerebral White Matter Vacuolar Degeneration in Two Related Labrador Retriever Puppies

Two Labrador Retriever dogs from a common dam had similar neurological deficits consisting of cortical blindness, dullness, and loss of previously learned habits. Both were examined at 5 months of age, and histopathological examination revealed leucoencephalomalacia and vacuolar degeneration of the cerebral white matter. Histopathologic findings in these 2 dogs differed from those reported previously in Labrador Retrievers with spongy degeneration of central nervous system white matter. A nonlittermate full sibling to 1 of these dogs was examined at 1.5 years of age for similar clinical signs that did not progress for the next 25 months.     

Breed and sex differences in growth curves for two breeds of dog guides

A desirable dog guide weighs 18 to 32 kg as an adult. Male and female German shepherd dogs and male and female Labrador retrievers were weighed between birth and 18 mo of age, with at least one weight recorded after 290 d of age. Growth curves were constructed from 10,484 observations on 880 dogs using the Gompertz function in the form Wt = W(max)exp(-e[-(t-c)/b]), where Wt is weight at time t, Wmax is mature body weight, b is proportional to duration of growth, c is age at point of inflection, and t is age in days. Estimates for mature body weight were 2.4 +/- .3 kg higher for Labrador retrievers than for German shepherd dogs and 4.7 +/- .2 kg higher for males than for females. Male Labrador retrievers were closest to the upper limit for desirable weight, with an average estimated mature weight of 31.4 +/- .3 kg. Duration of growth, 4b + c, was not different between the breeds; however, the estimate for males was 8 +/- 5d longer than for females. Female Labrador retrievers had the shortest estimate for growth of 319 +/- 6 d. The estimate for age at the point of inflection was 3.6 +/- 1.2 d greater for males than for females, but not different between breeds. A better understanding of growth curves for dog guides may aid in estimating mature weight at a young age, thus allowing earlier breeding and training decisions to be made and increasing genetic change per year.     

Familial canine dermatomyositis: clinical, electrodiagnostic, and genetic studies

Three Collies with a skin disorder, 6 progeny from a breeding of 2 of the Collies (incross litter), and the 4 progeny from the breeding of an affected Collie male and a normal Labrador Retriever female (outcross litter) were examined. By 7 to 11 weeks of age, all 6 dogs in the incross litter developed a qualitatively similar, but variably severe, dermatitis of the ears, face, lips, tip of the tail, and over bony prominences of limbs. Later, myopathic signs characterized by bilaterally symmetrical skeletal muscle atrophy of the head, neck, trunk, and extremities; facial palsy; decreased jaw tone; stiff gait; and hyperreflexia were observed in the dogs more severely affected by the dermatitis. Of the 4 dogs in the outcross litter, 3 had similar, but milder, clinical manifestations of the dermatitis and myopathy. Cutaneous lesions consisted of intraepidermal and subepidermal vesicles or pustules with intradermal infiltration by leukocytes. Muscle lesions included myositis; myofiber degeneration, regeneration, and atrophy; and fibrosis. A generalized myopathy in the severely affected dogs was indicated by abnormal readings on needle electromyograms and normal motor nerve conduction velocities. Spontaneous needle electromyogram abnormalities were fibrillation potentials, positive sharp waves, and bizarre high-frequency discharges. Retrospective and prospective genetic analyses disclosed a definite familial tendency and indicated the condition has an autosomal dominant component.     

Comparison of tibial plateau angles in dogs with and without cranial cruciate ligament injuries

OBJECTIVE: To measure and compare tibial plateau angles (TPA) of dogs with cranial cruciate ligament (CrCL) injuries and dogs without CrCL injuries. DESIGN: Prospective study. ANIMALS: 87 dogs. PROCEDURE: Stifle joints were measured from lateral radiographic views to determine TPA in 3 groups: group-1 dogs had CrCL injuries, group-1a dogs, a subgroup of group 1, had 1 unaffected stifle joint, and group-2 dogs had no CrCL injuries. Age, sex, breed, body weight, limb injured, and TPA were recorded for each dog. RESULTS: 56 stifle joints were measured in group-1 dogs; mean TPA was 23.76 degrees , and mean age and weight were 5.7 years and 37.91 kg (83.4 lb), respectively. Fourteen stifle joints were measured in group-1a dogs; mean TPA was 24.71 degrees , and mean age and weight were 5.6 years and 38.06 kg (83.8 lb), respectively. Sixty stifle joints were measured in group-2 dogs; mean TPA was 18.10 degrees , and mean age and weight of these dogs were 4.83 years and 35.85 kg (79 lb), respectively. The most common breeds included Labrador Retriever, Golden Retriever, and Rottweiler. The TPA of dogs in group 1 and group 1a were significantly greater than the TPA of dogs in group 2. CONCLUSIONS AND CLINICAL RELEVANCE: Dogs with CrCL injuries have a significantly greater TPA than dogs without CrCL injury. With further investigation, a normal TPA can be determined. In the future, TPA measurements may be used to screen dogs suspected of being susceptible to CrCL injury.     

Reference values of the red blood profile in beagle, German shepherd and golden retriever puppies

In the present study, blood samples were taken from clinically healthy puppies of the breeds Beagle, German Shepherd, and Golden Retriever between days 1 and 3 (n = 146), 8 and 10 (n = 137), 28 and 33 (n = 151), and 50 and 58 (n = 129) post natum. Measurements for red blood cell count, haemoglobin concentration, haematocrit, mean erythrocyte volume (MCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC) were performed by a semi-automatic blood cell counter; the normoblast number was counted visually. Between the 1st and 3rd day of life, the erythrocyte number of the puppies was 4.57 +/- 0.68 10(6)/microliter and, as such, was clearly below the reference range for adult animals. It further decreased by the 2nd measurement (8th to 10th day of life) to 3.59 +/- 0.41 10(6)/microliter, and then increased again to 4.75 +/- 0.68 10(6)/microliter (reference range: 3.73-6.25 10(6)/microliter, 2.5% to 97.5% percentile) by the final measurement (50th to 58th day of life). The measurement values of the haemoglobin concentration (13.5 +/- 2.0 g/dl) and haematocrit (41.0 +/- 6.5%) after birth were only insignificantly below or around the lower limit of the reference range for adult animals. Both parameters decreased to a more pronounced extent than did the erythrocyte count. They reached a minimum of 8.4 +/- 1.0 g/dl and 26.8 +/- 3.2%, respectively, between the 28th and 33rd day of life. Even at the end of the examination period (50th to 58th day of life), the values of these parameters (10.1 +/- 1.1 g/dl, reference range: 7.5-11.8 g/dl; 32.1 +/- 4.2%, reference range: 24.8 to 40.8%) were remarkably lower than the minimum of reference range for adult dogs. At the 1st sampling (between 1st and 3rd day of life), MCV (89.8 +/- 6.7 fl) and MCH (29.6 +/- 1.9 pg) were distinctly higher than the reference values for adult dogs. Both parameters decreased with increasing age. Thus, from the 50th-58th day of life, the results were comparable to those of adults. No considerable age dependence was found for MCHC. During the first days of life a relatively high number of normoblasts (8 +/- 7/100 Leukozyten) was found; it decreased rapidly. The study revealed significant differences between the breeds, e.g. German Shepherd dogs had lower initial values of erythrocyte count, haemoglobin concentration, and haematocrit when compared to the other breeds. Puppies of this breed also had higher normoblast numbers than the Beagle and Golden Retriever puppies at the 2nd and 3rd samplings. No clear sex differences in the studied parameters were observed. The results of this study reflect the replacement of fetal erythrocytes by postnatal erythrocytes. Moreover, they illustrate the need to use age as well as breed-specific reference ranges.     

Breed, sex, and body weight as risk factors for rupture of the cranial cruciate ligament in young dogs.

OBJECTIVE: To describe clinical features of dogs < 2 years old with rupture of the cranial cruciate ligament (CCL) and to evaluate breed, sex, and body weight as risk factors. DESIGN: Case-control study. ANIMALS: 201 dogs < 2 years old with rupture of the CCL and 804 age-matched control dogs. PROCEDURE: Medical records were reviewed for breed, sex, and body weight, and results were compared with results of age-matched control dogs. RESULTS: Breed predisposition was detected for Neapolitan Mastiff, Akita, Saint Bernard, Rottweiler, Mastiff, Newfoundland, Chesapeake Bay Retriever, Labrador Retriever, and American Staffordshire Terrier. Increased risk was detected for neutered males and neutered females, compared with sexually intact males and sexually intact females, respectively. Differences in prevalence of rupture of the CCL were not detected between all males and females, sexually intact males and sexually intact females, or neutered males and neutered females. Body weights of dogs with ruptured CCL were significantly greater than those of control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Several large breeds of dogs are predisposed to rupture of the CCL at a young age.     

Copper-associated chronic hepatitis in Labrador Retrievers

This study summarizes the clinical and pathologic findings in 15 Labrador Retrievers with copper-associated chronic hepatitis (CACH). Our hypothesis was that this form of hepatitis is caused by a defect in hepatic copper metabolism, which most likely originates from a genetic defect. Affected Labradors consisted of 11 female and 4 male Labrador Retrievers. Eight family members of 2 of these patients were examined prospectively, as were 6 unrelated healthy Labrador Retrievers. All dogs were registered at the breed club. The average age at clinical presentation was 7 years (range, 2.5-10.5 years). All dogs were presented for anorexia, which was associated with vomiting in 8 patients. The diagnosis of CACH was based on histologic examination of liver biopsy specimens in all dogs, including semiquantitation of copper. A disproportionate increase in alanine aminotransferase (ALT) activity relative to alkaline phosphatase (ALP) activity, as well as the centrolobular localization of copper and the association of copper accumulation with hepatic lesions, suggested a primary copper storage disease rather than primary cholestatic liver disease causing copper accumulation. Mean hepatic copper concentration measured in related Labradors was 1,317 microg/g dry weight liver (range, 402-2,576 microg/g). Mean hepatic copper concentration of unrelated normal Labradors was 233 microg/g dry weight liver (range, 120-304 microg/g). Our findings support the hypothesis that a hereditary form of hepatitis occurs in Labrador retrievers and is caused by a defect in hepatic copper metabolism.     

Risk factors for hip-related clinical signs in a prospective cohort study of four large dog breeds in Norway

We conducted a prospective cohort study including privately owned dogs from the breeds Newfondland (NF), Labrador Retriever (LR), Leonberger (LEO), and Irish Wolfhound (IW) followed from birth until age 9 yrs. We wanted to investigate whether radiological hip dysplasia status given at approximately age 12-18 mos and other factors during growth influenced development of clinical signs due to hip-joint disease necessitating veterinary consultation. Whether or not such signs occurred due to hip dysplasia or due to secondary or primary DJD could not be distinguished, and we therefore used the term "owner-reported veterinary-diagnosed hip-related clinical signs" ("the event"). The included dogs were followed from birth to the event or until a maximum of 9 yrs of age. Our objectives were to describe breed differences in time to incidence and to evaluate potential risk factors for the time to event. We used Kaplan-Meier curves to describe time to incidence, and potential risk factors were assessed by use of a Cox proportional-hazards model. We enrolled 494 dogs from 103 litters, and 46 dogs were reported as having had the event during the observation period. We observed a significant time-varying effect (TVE): LR and LEO developed clinical signs later in life than NF. If the radiological hip status was either mild, moderate, or severe the hazard of experiencing the event was significantly increased. Access to off-leash exercise at age 12 mos decreased the hazard of the event, and the hazard varied by litter. The findings supported the hypothesis that radiological hip status at screening and exercise conditions during growth influenced the time to incidence of the event and that there were breed differences in time to the event.     

Genetic aspects of Labrador Retriever myopathy

Labrador Retriever myopathy (LRM) has become a relatively common muscular disease. The objective of our prospective study was to determine by segregation analyses a plausible mode of inheritance within a Labrador Retriever population. Therefore we performed neurological examinations, as well as electromyographic and histopathological evaluations of 58 closely related dogs. Seven dogs with an average age of 27.8 months had clinical signs consistent with LRM including exercise intolerance or fatigue. The diagnosis was based on neurological deficits and confirmed by histopathological results of muscle biopsy. We found in all cases obvious differences in fiber calibre size associated with texture disturbances. In addition, we found 41 clinically normal dogs with histological findings consistent with LRM. Three genetic models, the major gene, the mixed inheritance as well as the environmental model, were evaluated by segregation analyses. They were applied to an extended pedigree including 164 non-randomly ascertained related Labradors. According to phenotype the clinically examined dogs were divided into two different data sets. One data set distinguished between clinically normal and abnormal dogs, the second data set between histopathologically normal and abnormal dogs. We concluded that the clinical form of LRM is transmitted by a major gene and controlled by an autosomal recessive mode of inheritance. Furthermore, for expression of the subclinical form an additional gene or an environmental factor is responsible. Our findings suggest that LRM is similar to limb-girdle muscular dystrophy in man and therefore, may be used in the future as an animal model.     

COMPARISON OF TWO PALPATION, FOUR RADIOGRAPHIC AND THREE ULTRASOUND METHODS FOR EARLY DETECTION OF MILD TO MODERATE CANINE HIP DYSPLASIA

Hip joint laxity was evaluated in Golden Retriever (n = 60), Labrador Retriever (n = 23), and Labrador/Golden Retriever mix (n = 24) puppies. Ortolani and Bardens maneuvers, four radiographic measurement indices and three dynamic ultrasonographic measurements were used. Each puppy was evaluated twice; at 6.5 to 9 and 43 to 79 weeks of age. These nine methods were compared for accuracy in predicting the development of canine hip dysplasia with or without degenerative joint disease by a median age of 16 months. The Bardens maneuver was a significant predictor of canine hip dysplasia/+/-degenerative joint disease for Golden Retriever puppies, however, it was not a reliable predictor for the other two breeds. Norberg angle measurements taken with femurs in a neutral position with hips distracted (PennHip position) was a significant predictor of degenerative joint disease in two breeds, but not in Golden Retriever puppies. Ultrasound measurement was a reliable predictor of hip canine hip dysplasia/+/-degenerative joint disease for Labrador/Golden Retriever mix puppies, but was not reliable for the other two breeds. Palpation, radiographic, and ultrasonographic methods of evaluating hip joint laxity in puppies at 6.5 to 9 weeks of age were not consistently reliable for all three breeds in predicting hip dysplasia with or without degenerative joint disease at one year of age. A strong association was found between Norberg angle and degenerative joint disease occurrence, as well as between distraction index (PennHip) and degenerative joint disease occurrence when measured at 52 to 79 weeks of age, but not when measured at 6.5 to 9 weeks of age in these breeds. These results emphasize the difficulty of early detection of mild hip dysplasia in the dog.