The blue merle Shetland sheepdog gene explained

The blue merle colouration within the Shetland sheepdog (or sheltie) breed is one of the most striking and visually impressive coat patterns available. This unique colouring is caused by a genetic mutation rather than being a natural breed colour, giving rise not only to beautiful markings but also potential health concerns that responsible owners need to understand.

The blue merle gene is recessive, meaning puppies are unlikely to show this trait if only one parent carries the gene. However, when both parents carry this gene, the chances increase significantly that some or all offspring will inherit the blue merle coat and associated genetic traits. It is important to understand these genetic factors and potential complications before deciding to own or breed a blue merle Shetland sheepdog.

Understanding the blue merle gene and its impact

The Shetland sheepdog comes in various recognised colours including tricolour (black, white and tan), brown and white, black and white, grey merle, among others. The colours seen in puppies depend on the genetic makeup of both parents and sometimes further back through their ancestry.

A dog carrying a single blue merle gene may not visibly display it but is still a carrier. Such a dog might have either a typical Sheltie coat or the characteristic blue merle pattern without other genetic issues. The complexity arises when two carriers are bred together, producing pups with a "double merle" gene. These puppies are more likely to exhibit the blue merle colouring with associated disorders affecting eye and ear development.

Breeding blue merle Shetland sheepdogs responsibly

When a blue merle carrier (single gene) is mated with a non-carrier, the puppies often display diluted black pigment resulting in a silvery or grey shade rather than the vivid blue merle. These pups usually feature tan markings, distinguishing true blue merles from bi-blue Shelties, which lack tan areas and show a white, black and grey merle coat.

Responsible breeders carefully track their dogs’ genetic history, avoiding breeding two merle carriers to prevent double merle offspring which can suffer from health complications.

Health concerns associated with the double merle gene

The double merle gene creates a pigment disorder that affects more than coat colour. It can alter the shape and colour of the eyes and disrupt the normal development of nerve endings in the inner ear. This can cause a range of vision problems, from reduced night vision and poor depth perception to blindness. Hearing problems, including partial or total deafness, are also common.

Signs to watch for in affected dogs include unsteady movements, bumping into objects, difficulty focusing, and not responding to sounds such as calls or loud noises. Early recognition of these symptoms helps in managing the dog's quality of life effectively.

How to identify the presence of the merle gene in your Sheltie

Colour alone cannot reliably indicate the genetic makeup of a dog. Only genetic testing or examining detailed ancestral records can confirm whether a dog carries the blue merle gene.

Reputable breeders maintain thorough lineage documentation and conduct genetic testing to ensure they avoid breeding two carriers. This responsible approach helps reduce the incidence of health issues associated with the double merle gene and supports the overall wellbeing of the breed.

Before acquiring a blue merle Shetland sheepdog, ask your breeder for genetic test results and health clearances. This is important for choosing a healthy puppy and promoting ethical breeding standards in the Sheltie community.