Why breeding two merle dogs together is harmful

The word “merle” describes a distinctive coat colour and pattern seen in some dog breeds. This pattern, admired for its unique mottled patches across solid or piebald coats, often comes with blue or odd-coloured eyes, making merle dogs eye-catching and popular amongst buyers. However, this striking appearance brings important genetic considerations when breeding merle dogs.

Merle coloration is controlled by a specific gene, often called the merle gene, which is incompletely dominant. When a merle dog is bred with a non-merle dog, roughly half the puppies inherit the merle pattern. Yet, breeding two merle dogs together significantly increases genetic risks, especially the possibility of producing double merle puppies.

What is double merle and why does it matter?

A double merle occurs when a puppy inherits two copies of the merle gene—one from each merle parent. While all puppies from two merle parents will display merle colouring, about 25% of these will be double merles. This genotype is linked to serious health challenges.

Double merle dogs have a high risk of sensory impairments, including congenital deafness and vision problems such as malformed eyes or total blindness. These defects result from disrupted pigment cell development that affects eye and ear structures. Beyond sensory issues, double merles are more prone to allergies, autoimmune diseases, and skin sensitivities, including increased vulnerability to sunburn due to lack of normal pigmentation.

These health problems can severely impact a dog’s quality of life, requiring special care and adaptation. Sadly, many double merle puppies may struggle to find suitable homes and sometimes end up in rescue centres. Responsible breeders actively avoid matings that risk producing double merle puppies to prioritise animal welfare.

UK Kennel Club regulations and responsible breeding

Due to the welfare concerns associated with double merle dogs, the UK Kennel Club has taken a firm stance. Since 2013, it prohibits registering puppies from merle-to-merle breedings. In some breeds where merle colouring is accepted, such as the Cardigan Welsh corgi, Border collie, and Dachshund (referred to as “dapple” in that breed), breeding two merle parents is forbidden and results in registration denial for the whole litter.

These strict regulations discourage breeders from producing double merles, promoting genetic health and animal welfare. Prospective puppy buyers interested in merle-coloured dogs are urged to ask breeders about the puppy’s parentage and ensure their pup is not a double merle with increased health risks.

How to responsibly acquire a merle puppy

If you desire a merle puppy, it is vital to choose a reputable breeder committed to ethical practices. This means no merle-to-merle breedings, proper health screening, and transparency regarding the parents’ genetics and pedigrees. This careful approach helps prevent health complications and supports the wellbeing of the puppies you welcome into your home.

Understanding the serious consequences of breeding two merle-coloured dogs together strengthens the case for responsible breeding. It protects dogs from avoidable health problems and ensures quality of life, while respecting breed standards and Kennel Club policies.

For further information on dog breeds and finding reputable breeders, visit dog breeds.