Skeletal Dwarfism (SD2) Testing for Labrador Retrievers

Labrador retrievers can inherit a hereditary condition called skeletal dwarfism (SD2). This genetic health issue leads to disproportionate dwarfism, where affected dogs have shorter legs, especially the front legs, while their body size remains normal. Understanding SD2, its inheritance, and testing helps breeders make responsible decisions to reduce its spread.

Understanding Skeletal Dwarfism (SD2) in Labradors

SD2 is a mild form of skeletal dysplasia caused by a recessive mutation in the COL11A2 gene. Dogs affected with two copies of this mutation (homozygous mutant) show shortening and slight bowing of the front limbs. The condition is distinctive due to disproportionate limb length compared to the overall body, but it typically doesn't cause other health problems or reduce lifespan.

Affected adult males often stand under 55cm at the shoulder, females under 50cm, though these heights can vary in tall bloodlines. Puppies initially seem normal at birth, with signs becoming obvious by around six months old as the long bones fail to grow properly.

Inheritance of SD2: How the Condition is Passed Down

SD2 is inherited as an autosomal recessive trait. This means a dog must inherit two copies of the mutated gene—one from each parent—to develop the condition. Dogs are classified as:

• Clear (N/N): No mutated gene copies; they neither develop nor pass on SD2.
• Carriers (N/SD): One mutated gene copy; unaffected themselves but can pass the mutation to offspring.
• Affected (SD/SD): Two mutated gene copies; will develop dwarfism and pass it on to all offspring.

Breeding two carriers risks 25% of puppies being affected. Responsible breeders use this knowledge to avoid carrier-to-carrier pairings, thereby minimising SD2 prevalence.

Why Testing for SD2 is Important

Testing helps identify clear, carrier, and affected Labradors, making breeding decisions more informed and ethical. This prevents producing affected puppies, improving the health and welfare of future generations of dogs.

How to Get Your Labrador Tested for SD2

To determine your dog's genetic status, ask your vet to collect a DNA sample. The sample can be a cheek swab, blood, semen, or tissue. This is sent to one of The Kennel Club's approved laboratories or reputable genetic testing companies such as Laboklin or CombiBreed.

Results typically arrive within 10-12 working days and will clearly state if the dog is clear, a carrier, or affected by the SD2 gene mutation.

Responsible Breeding Practices to Manage SD2

Breeders should:

• Test all potential breeding Labradors for SD2 status.
• Avoid mating two carriers together to prevent affected puppies.
• Breed carriers only to clear dogs, which will produce carrier but not affected pups.
• Inform puppy buyers about testing and health history to promote responsible ownership.

Such strategies help maintain the breed's health while respecting breed standards and welfare.

Summary and Next Steps

Skeletal Dwarfism (SD2) in the Labrador retriever is a hereditary condition caused by a recessive COL11A2 gene mutation. It results in shortened limbs but does not usually affect a dog's quality of life. Genetic testing is widely available and essential for responsible breeding management.

If you own a Labrador or plan to breed, consider testing to clarify your dog's status, avoid carrier-to-carrier matings, and help reduce SD2 incidence in the breed. This promotes happier, healthier Labradors and supports ethical breeding practices aligned with The Kennel Club's health initiatives.