Animalia Life

The Breed History
This breed, the most popular breed in North America, took its name from the province of Labrador-Newfoundland in Canada, where this hardy breed was first reported in the early 1800s. They were exported to England not long after, and recognized by the English Kennel Club in 1903. AKC registrations began in 1917.

Breeding for Function
As their name implies, these solid, muscular dogs were bred to be gun dogs for retrieving waterfowl. They are much more versatile than that, and so have also become popular as assistance and therapy dogs, for companionship, obedience, agility, and as search and rescue and narcotics dogs. The field lines are leaner and taller than average.

Physical Characteristics
Height at Withers: female 21.5-23.5" ( 54.5-59.5cm), male 22.5-24.5" (57-62 cm)
Weight: females 55-70lb (25-32 kg) , males 65-80 lb (29.5-36.5 kg).
Coat: Their glossy water-resistant coat is flat, dense and short, and comes in three colors: black, chocolate and yellow. They have a soft wooly undercoat that provides insulation and water resistance. Longevity: 11-13 years.
Points of Conformation: These are compact muscular dogs, a bit longer than tall that have a distinctive thick tail, referred to as "otter" type. These tails extend to the tarsus and taper from a thick origin, and are not feathered. The skull is broad and mesocephalic in type, with moderate stop and well-developed jaws and soft mouth for game handling. Eyes are medium-sized, dark, and express a gentle look, and the nose is wide and pigmented brown on chocolates, and black in black labs. The eyes are usually brown, but can be hazel in the chocolates. The ears are medium sized, leathered and pendulous in a triangular shape. The neck of medium length has moderate arch, and the topline is level. The chest is moderate in volume and depth and the abdomen is not tucked up. Limbs are straight and solid boned. Feet are compact and the toes are webbed and arched. The dewclaws may be removed. Their way of going is easy and straight, giving the impression of stamina and sturdy grace.

Recognized Behavior Issues and Traits
These dogs are famous for their placid, loving temperament. They enjoy play and need lots of human contact. Their loyalty and intelligence make them a treasured companion dog. Good with children and other pets, they are also easy to train but they need to be trained from an early age. They require both mental challenge and physical exercise for good health. If bored, they may resort to chewing. They are average shedders that need only routine grooming care. They gain weight easily.

Normal Physiologic Variations
None Reported

Drug Sensitivities
None Reported

Inherited Diseases
Hip Dysplasia: Polygenically inherited trait causing degenerative joint disease and hip arthritis. Reported at a frequency of 12.6% in one study. OFA reports 12.0% affected. Quantitative trait loci (QTL) have been identified in the breed that are linked to the development of hip dysplasia. Heritability estimated at 0.21 in the breed. Selection based on relatives (estimated breeding values) provide a greater response than selection based on phenotype alone.
Elbow Dysplasia: Polygenically inherited trait causing elbow arthritis. Reported at a frequency of 17.8% with a male predilection in Labrador Retrievers in one study. OFA reports 11.0% affected. Reported 20.5x odds ratio for fragmented coronoid process, 8.5x odds ratio for ununited anconeal process forms of elbow dysplasia, and 109.4x odds ratio for elbow osteochondrosis versus other breeds.Heritability estimated at 0.12 in the breed. Dietary restriction slows the progression of elbow arthritis in affected dogs.
Patella Luxation: Polygenically inherited laxity of patellar ligaments, causing luxation, lameness, and later degenerative joint disease. Treat surgically if causing clinical signs. Lateral patella luxation occurs in the Labrador Retriever, with a 3.3x relative risk versus other breeds. OFA reports 9.4% affected.
Progressive Retinal Atrophy (prcd-PRA): Autosomal recessive progressive rod cone degeneration (prcd) form. Age of onset between 3-8 years of age, eventually causing blindness. Optigen reports 3% testing affected, and 20% testing carrier. A genetic test is available.
Exercise Induced Collapse (EIC, Dynamin 1 Mutation): Average age of recognition is 12 months, especially in dogs being trained. An autosomal recessive disorder of muscle weakness, incoordination and life threatening collapse accompanied by hyperthermia after just five to fifteen minutes of intense exercise or excitement. After 10 to 30 minutes of rest, most dogs return to normal. Genetic testing shows 3% of Labrador Retrievers are affected, and over 30% carriers. A genetic test is available.
Oculo-Skeletal Dysplasia/Retinal Dysplasia (RD/OSD): Autosomal recessive developmental disease causing ocular vitreous dysplasia, cataracts, retinal detachment, and dwarfism with valgus deformity of the carpi. Heterozygous carriers of the defective gene present with various forms of retinal dysplasia (folds, geographic, or detachment). Retinal dysplasia is identified in 2.31% of Labrador Retrievers CERF examined by veterinary ophthalmologists between 2000-2005. CERF does not recommend breeding any affected Labrador Retrievers. A genetic test is available.
Centro-Nuclear Myopathy (CNM): Autosomal recessive disorder of muscle weakness. Onset of progressive weight loss and loss of tendon reflexes by 2 months of age, and an awkward gait, decreased exercise tolerance, and generalized muscle weakness between 2-5 months of age. Clinical signs stabilize in adult affected dogs. A genetic test is available.
Tricuspid Valve (Right Atrioventricular) Dysplasia: Autosomal dominant disorder with incomplete penetrance. Congenital malformation of the tricuspid valve leaflets, chordae tendineae, and/or right ventricular papillary muscles. Mild cases have no clinical signs except tricuspid regurgitation on auscultation and echocardiography. Severely affected dogs show signs of ascites, pleural effusion, exercise intolerance, syncope, weight loss, arrythmia, and right sided heart failure. Labrador Retrievers have a 35x relative risk versus other breeds, with a heritability of 0.71. No genetic test is available.
Cystinuria: Rare, autosomal recessive disease causing dysuria, stranguria, or obstruction due to cystine calculi, primarily in affected males. Caused by a defect in cystine metabolism. Affected females can have cystine crystals and calculi without clinical signs. A genetic test is available.
Narcolepsy: Rare, autosomal recessive disorder causing sudden collapse and a sleep-like state elicited by excitement. Clinical episodes begin at four weeks of age, with maximal symptoms by 10-32 weeks of age. A genetic test is available.

Disease Predispositions
Allergic Dermatitis: Inhalant or food allergies. Presents with pruritis and pyotraumatic dermatitis (hot spots). The breed has a significant frequency of allergies, with a computed heritability of 0.47.
Hypothyroidism: Inherited autoimmune thyroiditis. 5.7% positive for thyroid autoantibodies based on testing at Michigan State University. (Ave. for all breeds is 7.5).
Persistent Pupillary Membranes: Strands of fetal remnant connecting; iris to iris, cornea, lens, or involving sheets of tissue. The later three forms can impair vision, and dogs affected with these forms should not be bred. Identified in 3.41% of Labrador Retrievers CERF examined by veterinary ophthalmologists between 2000-2005.
Epilepsy (Inherited Seizures): Can be generalized or partial seizures. Control with anticonvulsant medication. Occurs at a frequency of 3.1% in Danish Labrador Retrievers with 24% generalized, and 70% partial seizures. Proposed polygenic inheritance with a major recessive gene of influence.
Cataracts: Polar subcapsular triangular cataracts predominate, usually developing between 6 and 18 months of age, with 75% of affected dogs developing cataracts by 5 years of age. Proposed autosomal recessive mode of inheritance. Identified in 2.64% of Labrador Retrievers CERF examined by veterinary ophthalmologists between 2000-2005. Identified in 8% of Labrador Retrievers in Holland, with offspring of affected dogs occuring at a much higher frequency. CERF does not recommend breeding any Labrador Retriever with a cataract.
Cranial Cruciate Ligament (ACL) Rupture: Traumatic tearing of the ACL in the stifle, causing lameness and secondary arthritis. Treat with surgery. Reported at an increased incidence versus other breeds. In one study, 23% of large breed dogs with the diagnosis were Labrador Retrievers. Dorn reports a 2.17x odds ratio versus other breeds. There is no difference in tibial plateau angle between affected and unaffected Labrador Retrievers with ACL rupture.
Osteochondritis Desicans (OCD): Inherited joint cartilage defect. Causes joint pain and lameness in young growing dogs. Mild cases can resolve with rest, while more severe cases require surgery. Reported 45.9x odds ratio for hock OCD, 27.6x odds ratio for stifle OCD and 13.1x odds ratio for shoulder OCD versus other breeds.
Hypertrophic Osteodystrophy (HOD): Immune-mediated disorder causing fever, and painful, swollen joints and bones in young Labrador Retrievers. Occurs mostly within 3-14 days post-vaccination. Age of onset is 8-16 weeks. Reported 5.9x odds ratio versus other breeds.
Chronic Hepatitis/Copper Associated Hepatitis: A breed-related hepatopathy occurs in Labrador Retrievers, characterized by vomiting, polyuria/polydipsia, icterus, and abdominal pain and distention. Liver enzymes are elevated, and histopathology shows chronic inflammation, fibrosis, and copper accumulation. Feeding low copper diets is helpful in controlling the disease. Incidence is 1.2% in the breed, with a median age at diagnosis of 9.3 years. Unknown mode of inheritance.
Distichiasis: Abnormally placed eyelashes that irritate the cornea and conjunctiva. Can cause secondary corneal ulceration. Identified in 0.90% of Labrador Retrievers CERF examined by veterinary ophthalmologists between 2000-2005.
Corneal Dystrophy: Non-inflammatory epithelial/stromal corneal opacity. Identified in 0.76% of Labrador Retrievers CERF examined by veterinary ophthalmologists between 2000-2005.
Lymphoma/Lymphosarcoma: Malignant cancer of lymphoid tissue. Both B-cell and T-cell (mycosis fungoides) occur in the breed.
Entropion: A rolling in of the eyelids, can cause corneal irritation and ulceration. Correct with surgery. Reported at an increased incidence versus other breeds. Identified in 0.44% of Labrador Retrievers CERF examined by veterinary ophthalmologists between 2000-2005.v Acquired Laryngeal Paralysis: Late-onset disorder of laryngeal dysfunction secondary to axonal degeneration of the recurrent laryngeal nerve. Affected dogs show exercise intolerance, inspiratory stridor, inspiratory dyspnoea, gagging, coughing and dysphonia. There is a male:female ratio of 1.56:1 and the average age of presentation is 9.9 years. Labrador Retrievers are identified as the most frequently affected breed.
Diabetes Mellitus (Sugar Diabetes): Treat with insulin injections. Age of onset between 5-12 years. Labrador Retrievers represent 17.4% of all diagnosed cases.
Immune-Mediated Hemolytic Anemia (IMHA): Autoimmune destruction of red blood cells. Females are more frequently affected than males. Labrador Retrievers account for 8% of diagnosed cases. Unknown mode of inheritance.
Nasal Parakeratosis: Inherited disorder of nasal hyperkeratotic lesions appearing between 6 and 12 months of age. Affected dogs have mild to severe lesions of dry and rough keratin affecting the dorsal aspect of the nasal planum. Fissures and erosions can develop in severe cases. Proposed autosomal recessive inheritance.
Uveal Cysts: Labrador Retrievers have a higher frequency of uveal cysts than other breeds, with a mean age of cyst development of 9.1 years.
Secondary Glaucoma: Glaucoma causes increased pressure within the eyeball and blindness due to damage to the retina. The breed is listed as predisposed to secondary glaucoma due to uveitis or lens luxation. Screen with tonometry.
Limbal Melanoma: Benign eye mass, usually originating from the dorsal limbus. Labrador Retrievers have a 3.0x odds ratio of limbal melanomas versus other breeds.
Lingual Squamous Cell Carcinoma (SCC): Labrador Retrievers have a 2.41x odds ratio versus other breeds of developing this tongue cancer. Females are overrepresented in one study.
Atrioventricular (Heart) Block: Labrador Retrievers are found to be at increased risk of high-grade second- or third-degree atrioventricular block versus other breeds. Treatment is with a pacemaker.
Histiocytic Sarcoma/Histiocytosis: Malignant cancer of CD11d+ macrophages, producing masses in the spleen, liver, lung, bone marrow, +/or eye. Mean age of diagnosis of 8.61 +/- 2.43 years, with a less than 6 month life expectancy. Labrador Retrievers are overrepresented in diagnoses versus other breeds.
Ectopic Ureter: Congenital malformation where one or both ureters do not enter the body of the urinary bladder, often entering the bladder neck or urethra causing incontinence. Labrador Retrievers are at increased risk versus other breeds. Unknown inheritance.
Digital Squamous Cell Carcinoma (SCC): Subungual (toe) squamous cell carcinoma occurs at increased frequency in black dogs. Treat with digital amputation. Labrador Retrievers account for 23.8% of all cases.
Iridociliary Epithelial Tumors: These intraocular adenomas and adenocarcinomas occur more frequently in the Labrador Retriever. They rarely metastasize.
Calcinosis Circumscripta: Calcinosis circumscripta is an uncommon syndrome of dystrophic, metastatic or iatrogenic mineralization of calcium salts in soft tissues. Lesions usually occur on the hind feet or tongue in 1-4 year old dogs. Nine percent of canine cases occur in Labrador Retrievers.
Ossification of the Infraspinatus Tendon-Bursa: Disorder identified in 13 Labrador Retrievers with unilateral or bilateral forelimb lameness between 2 to 10 years of age. Diagnose via radiograph. Treat with rest, steroid injection, or surgery.
Acral Lick Dermatitis, Central Axonopathy, Central PRA, Cervical Vertebral Instability, Cleft Lip/Palate, Degenerative Myelopathy, Ectropion, Factor VIII Deficiency, Fanconi Syndrome, Fibrinoid Leukodystrophy, Follicular Dysplasia, Gastric Dilatation w/Volvulus, Hypotrichosis, Juvenile Cellulitis, Lymphedema, Malignant Hyperthermia, Megaesophagus, Microphthalmia, Micropapilla, Mucinosis, Myelodysplasia, Myoclonus, Neuroaxonal Dystrophy, Optic Nerve Coloboma, Optic Nerve Hypoplasia, Panosteitis, Seasonal Flank Alopecia, Sebaceous Adenitis, Silica Urolithiasis, Spongiform Leukodystrophy, Supernumerary Teeth, Tetralogy of Fallot, Vitamin A Responsive Dermatosis, Vitiligo, and von Willebrand’s Disease are reported.

Isolated Case Studies
Hemophilia B (Factor IX deficiency): An affected male Labrador Retriever had clinically severe bleeding due to complete deletion of the Factor IX gene. A genetic test was developed for this X-linked recessive gene.
Cerebellar Abiotrophy: Several cases of juvenile cerebellar degeneration have been diagnosed in Labrador Retrievers. Puppies between 9 and 17 weeks of age developed rapidly progressive hypermetria, ataxia, and intension tremors resulting in euthanasia.
X-linked Muscular Dystrophy: A dystrophin deficient muscular dystrophy similar to human Duchenne’s muscular dystrophy was identified in a 3.5 month-old, male Labrador retriever. The dog presented with difficulty swallowing, poor body condition and a protruding tongue.
Mytubular Myopathy: Three to four-month-old, male, Labrador retrievers present with progressive weakness and muscle atrophy. Histology demonstrated central mitochondrial accumulations. A mutation in the MTM 1 gene causes this x-linked disease in the breed. Worldwide screening did not identify carriers outside of this affected kindred in Canada.
Chondrodysplasia/Dwarfism: An apparently autosomal recessively inherited dwarfism without retinal lesions is identified in a kindred of Labrador Retrievers in the Netherlands. Candidate gene analysis was not successful in identifying a causative gene.
Neuronal Ceroid-Lipofuscinosis (NCL): An 8-year-old, neutered male Labrador Retriever presented with an 11 month history of progressive partial seizure activity (facial and ear twitching), and a 2 week history of ataxia and dysphagia. Necropsy diagnosis confirmed NCL.
Mucopolysaccharidosis Type II (MPSII): A 5-year-old male Labrador Retriever had progressive incoordination, visual impairment, exercise intolerance, coarse facial features, macrodactylia, unilateral corneal dystrophy, and generalized osteopenia. X-linked recessive MPSII was diagnosed.
Sub-Follicular Panniculitis And Sebaceous Adenitis: A 6-year-old male black Labrador retriever presented with a 12 week course of nonpruritic multicentric, well-demarcated alopecia. Pathology revealed an inflammatory sebaceous adenitis and sub-follicular panniculitis. Alopecia was permanent in these areas.

Genetic Tests
Tests of Genotype: Direct tests for prcd-PRA, and RD/OSD are available from Optigen.
Direct test for exercise induced collapse (EIC) is available from the University of Minnesota Veterinary Diagnostic Lab.
Direct test for centronuclear myopathy (CNM) is available from the Alfort Lab labradorcnm.com, and the Animal Health Trust.
Direct test for cystinuria is available from PennGen.
Direct test for Hemophilia B is available from HealthGene.
Direct test for Narcolepsy is available from Optigen and HealthGene.
Direct tests for black, chocolate (brown), yellow, and diluted coat colors and black and brown nose are available from HealthGene and VetGen.
Tests of Phenotype: CHIC Certification: Required testing includes hip and elbow radiographs, and CERF eye examination. Optional gene test for CNM (See CHIC website; caninehealthinfo.org). Recommend thyroid profile including autoantibodies, patella evaluation, genetic test for EIC, and cardiac examination.

Miscellaneous
• Breed name synonyms: Lab, Labrador, Yellow Lab, Black Lab, Chocolate Lab, St. John’s Retriever (historical)
• Registries: AKC, CKC, UKC, KCGB (Kennel Club of Great Britain), ANKC (Australian National Kennel Club), NKC (National Kennel Club)
• AKC rank (year 2008): 1 (100,736 dogs registered)
• Internet resources: The Labrador Retriever Club, Inc.: thelabradorclub.com
Labrador Retriever Club of Canada: labradorretrieverclub.ca
The Labrador Retriever Club of Great Britain: thelabradorretrieverclub.com