Breed-Specific Merle Guidelines: Standards, Registrations, and Considerations
The merle pattern has a legitimate historical presence in certain breeds while representing a recent introduction - often through crossbreeding - in others. Understanding which breeds traditionally carry merle and the registration policies of major kennel clubs is essential knowledge for any breeder working with or considering this pattern.
The distinction between historically merle breeds and those where the pattern has been artificially introduced matters for several reasons. In traditional merle breeds, the pattern has been selected alongside other breed characteristics for generations, and experienced breeders have developed collective knowledge about managing it safely. In breeds where merle has been recently introduced, this accumulated wisdom does not exist, and the circumstances of introduction often raise additional genetic and ethical concerns.
Traditional Merle Breeds
The following breeds have documented histories of the merle pattern extending back many generations. While the same testing protocols apply regardless of breed, breeders of these dogs can draw on established knowledge bases and breed-specific guidance.
Australian Shepherd
Blue merle and red merle are both standard colours in the Australian Shepherd. The breed club maintains extensive resources on merle genetics, and experienced breeders typically understand the risks of merle-to-merle breeding. Both the AKC and The Kennel Club accept merle Australian Shepherds.
Rough and Smooth Collie
Blue merle has been present in Collies since the breed's establishment. The pattern appears as blue-grey with black patches, ideally with rich tan markings. Collie breed clubs have long advocated against merle-to-merle breeding, though cryptic merles have caused occasional double merle litters in carefully managed programmes.
Shetland Sheepdog
Blue merle Shelties follow the same pattern inheritance as Collies, and experienced breeders follow similar precautions. The breed's smaller size means that health problems in double merles are often particularly severe, as the already small ears and eyes are further compromised by the homozygous merle genotype.
Border Collie
Merle Border Collies have existed throughout the breed's history, though the pattern is less common than in some other herding breeds. Working Border Collie registries generally accept merle, as do The Kennel Club and AKC. The breed's intelligence can help affected individuals adapt to sensory impairments, but this does not justify producing them.
Cardigan Welsh Corgi
Unlike the Pembroke, the Cardigan Welsh Corgi has merle as a traditional colour. Blue merle with tan points is specifically mentioned in the breed standard. The Cardigan fancy has good awareness of merle genetics, and reputable breeders test breeding stock.
Dachshund
In Dachshunds, the merle pattern is called "dapple." It has a long history in the breed, particularly in certain European lines. The American Kennel Club accepts dapple as a standard pattern. However, "double dapple" - the Dachshund equivalent of double merle - produces the same tragic consequences seen in other breeds.
Great Dane
Merle in Great Danes interacts with the harlequin gene, creating additional complexity. The merle and harlequin patterns are both traditional in the breed, but breeding decisions must account for both genes and potential allele instability. The breed clubs have specific guidelines for colour breeding.
Old English Sheepdog
Blue merle Old English Sheepdogs exist but are relatively uncommon. The breed's long coat can make visual identification of merle pattern difficult, reinforcing the importance of genetic testing.
Key point for traditional breeds:
Even in breeds with long merle histories, complacency is dangerous. Every breeding animal should be genetically tested regardless of pedigree or visual appearance. "We've been breeding merles for fifty years without problems" is not a substitute for scientific verification.
Breeds Where Merle Raises Concerns
In recent decades, merle has appeared in breeds where it has no historical basis. This introduction typically occurs through crossbreeding, either intentionally to create "rare" colours or through undocumented mixed breeding. The appearance of merle in these breeds raises significant concerns.
French Bulldog
There is no historical evidence of merle in the French Bulldog gene pool. Its appearance in the breed indicates crossbreeding at some point in the pedigree. The Kennel Club does not register merle French Bulldogs, and the AKC breed standard does not include merle. Merle French Bulldogs cannot be shown in conformation and may face registration difficulties.
English Bulldog
Similar to French Bulldogs, merle English Bulldogs are not recognised by reputable registries. The combination of brachycephalic health issues with potential merle-related problems creates a concerning welfare picture.
Pomeranian
The status of merle in Pomeranians is debated. Some claim historical presence, while others consider it a recent introduction. The Kennel Club and AKC both accept merle Pomeranians, but breeders should research their specific lines carefully and test all breeding stock.
Chihuahua
Merle Chihuahuas exist in significant numbers but remain controversial. The AKC accepts them; The Kennel Club does not. The small size of the breed means that double merle health problems can be particularly devastating.
Cocker Spaniel
Merle in Cocker Spaniels is a recent introduction with no historical foundation. Neither The Kennel Club nor AKC breed standards include merle. Dogs sold as merle Cockers should be viewed with suspicion regarding their pedigree integrity.
When merle appears in a breed with no historical record of the pattern, it almost certainly entered through crossbreeding. This means the dog's pedigree documentation may be inaccurate, and other genes besides merle may have been introduced. Buyers should consider what else might have entered the gene pool along with the merle pattern.
Registration Policies
Major kennel clubs have developed policies to address merle in various breeds:
The Kennel Club (UK)
The KC maintains a list of breeds where merle is acceptable and will not register merle dogs in breeds not on this list. They also use a "Mate Select" system that flags potential merle-to-merle matings. Since 2020, they require DNA test results for merle status before registering puppies from certain colour combinations.
American Kennel Club
The AKC takes a more permissive approach, generally registering dogs based on parentage rather than colour. However, individual breed standards determine whether merle dogs can be shown in conformation. Breed clubs may have their own policies regarding merle breeding.
FCI (Federation Cynologique Internationale)
FCI policies vary by member country, but the organisation generally defers to breed standards regarding acceptable colours. Many European countries have stricter animal welfare legislation that may affect merle breeding practices.
Making Informed Decisions
Whether you are breeding a traditional merle breed or considering acquiring a merle dog from a more controversial background, the following principles apply:
- Verify registration status - Understand whether your dog can be registered and shown in your jurisdiction
- Research pedigree integrity - In non-traditional breeds, investigate how merle entered the line
- Test regardless of breed - Genetic testing is essential in all merle-affected populations
- Follow safe breeding protocols - The genetics work the same regardless of breed
- Connect with breed communities - Experienced breeders in traditional merle breeds have valuable knowledge to share
Regardless of breed, the fundamental rule remains constant: never breed any merle dog to another merle without absolute certainty of genetic status from DNA testing. The pattern is beautiful in many breeds where it legitimately belongs. The health consequences of careless breeding are tragic in all of them.
Dr. Patricia Wells
Canine Coat Genetics Specialist
Veterinary geneticist with over 25 years researching coat colour inheritance in domestic canids. Former research fellow at the Animal Health Trust and consultant to multiple breed health programmes across Europe and North America.
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