Why Breeding Merle to Merle is Highly Discouraged: Understanding the Risks
Breeding merle to merle dramatically increases the risk of producing puppies with severe health issues, particularly hearing and vision impairments. Therefore, why can’t i breed merle to merle? Because doing so significantly elevates the chances of double merle offspring inheriting two copies of the merle gene, resulting in serious developmental problems.
Understanding the Merle Gene
The merle gene (M), responsible for the mottled coat pattern seen in various dog breeds like Australian Shepherds, Collies, and Great Danes, is a dominant gene. This means a dog only needs one copy of the gene (Mm) to exhibit the merle phenotype. The non-merle allele is represented by ‘m’. Dogs with two copies of the non-merle allele (mm) are considered solid-colored or non-merle.
The Perilous Double Merle
When two merle dogs (Mm) are bred together, there is a 25% chance that each puppy will inherit the merle gene from both parents, resulting in a double merle (MM). This is where the trouble begins. Double merle dogs often exhibit a predominantly white coat and are at a significantly higher risk of developing serious health problems.
Associated Health Risks
Double merle dogs are prone to a range of health issues, most notably:
- Deafness: Often complete and irreversible, due to lack of pigment in the inner ear.
- Vision Impairments: Including microphthalmia (abnormally small eyes), colobomas (defects in the eye structure), and blindness.
- Skin Cancer: Increased susceptibility, particularly in areas with less pigment.
- Other Potential Issues: Sterility and neurological problems, though less common.
These health problems result from the merle gene’s impact on pigment cells during embryonic development. When a dog inherits two copies of the merle gene, this impact is significantly amplified, leading to severe developmental defects.
Ethical Considerations
Beyond the increased risk of debilitating health conditions, breeding merle to merle raises serious ethical concerns. Intentionally producing puppies with a high probability of deafness, blindness, or other health problems is considered irresponsible and unethical by most reputable breeders and animal welfare organizations. A responsible breeder prioritizes the health and well-being of their dogs and avoids breeding practices that could lead to suffering.
Prevention is Key
The best way to prevent double merle puppies is to avoid breeding merle to merle. This means ensuring that at least one parent is a non-merle (mm) dog. Reputable breeders often use genetic testing to determine the merle status of their dogs and make informed breeding decisions.
Alternatives to Merle-to-Merle Breeding
For breeders interested in preserving the merle pattern, there are responsible alternatives to breeding merle to merle:
- Breeding Merle to Non-Merle: This guarantees that no puppies will inherit two copies of the merle gene, and reduces the risk of health problems.
- Careful Selection of Breeding Pairs: Choosing non-merle dogs with desirable traits can help maintain breed standards while avoiding the risks associated with double merle inheritance.
- Genetic Testing: Genetic testing can help breeders understand the merle genetics of their dogs and make informed breeding decisions.
| Breeding Pair | Probability of Merle Puppy | Probability of Double Merle Puppy | Probability of Non-Merle Puppy |
|---|---|---|---|
| ——————- | ————————— | ——————————– | —————————– |
| Merle (Mm) x Merle (Mm) | 75% | 25% | N/A |
| Merle (Mm) x Non-Merle (mm) | 50% | 0% | 50% |
| Non-Merle (mm) x Non-Merle (mm) | 0% | 0% | 100% |
Frequently Asked Questions (FAQs)
What does “cryptic merle” mean, and how does it affect breeding decisions?
A cryptic merle or phantom merle is a dog that carries the merle gene but exhibits very little or no visible merle patterning. Genetic testing is the only reliable way to identify cryptic merles. Breeding a cryptic merle to another merle dog carries the same risks as breeding two visibly merle dogs.
How do I get my dog genetically tested for the merle gene?
Various genetic testing companies offer tests for the merle gene. Your veterinarian can advise you on which test is appropriate for your breed and provide guidance on sample collection and submission.
Can I breed a merle dog to a dog of a different breed to avoid double merle?
While breeding to a non-merle dog from a different breed eliminates the risk of double merle, it introduces other potential complications related to breed standards, genetic health, and temperament. Consider these carefully.
What are the signs of a double merle puppy?
Double merle puppies often have a predominantly white coat, particularly around the head and ears. Other signs include blue eyes, pink noses, and physical deformities of the eyes or ears. However, not all double merle dogs are completely white, and some may have more subtle markings.
Is it possible for a double merle dog to be healthy?
While some double merle dogs may appear healthy initially, they are still at increased risk for developing hearing and vision problems later in life. Early intervention and specialized care can improve their quality of life.
What should I do if I accidentally breed two merle dogs?
If you accidentally breed two merle dogs, consult with your veterinarian immediately. They can advise on prenatal care for the dam and prepare you for the possibility of double merle puppies. Be prepared to provide specialized care or consider humane euthanasia if puppies are born with severe health problems.
Are there any breeds where merle-to-merle breeding is acceptable?
There are no reputable breeders or breed clubs that advocate for merle-to-merle breeding. It is universally recognized as an irresponsible breeding practice that puts puppies at risk.
Can diet or supplements prevent health problems in double merle dogs?
While a healthy diet and appropriate supplements can support overall health, they cannot prevent or cure the genetic defects associated with double merle.
Are all white dogs double merles?
Not all white dogs are double merles. White coats can be caused by other genetic factors unrelated to the merle gene, such as albinism, extreme piebaldism, or genes that control coat color intensity. Genetic testing is the only way to definitively determine if a dog is a double merle.
What are the long-term care needs of a deaf or blind dog?
Deaf and blind dogs require specialized care and training. This includes learning hand signals, creating a safe and predictable environment, and using scent to aid navigation. With patience and dedication, deaf and blind dogs can live happy and fulfilling lives.
Why does the merle gene affect hearing and vision?
The merle gene disrupts the development of melanocytes, pigment-producing cells, which are crucial for the proper function of the inner ear and eyes. When melanocytes are absent or abnormal in these areas, it can lead to deafness, vision impairments, or both.
If I breed merle to merle, what are the chances of getting no double merle puppies?
The odds of not getting any double merle puppies from a merle-to-merle breeding are low. Because each puppy has a 25% chance of being a double merle, the odds diminish significantly with each additional puppy born. For example, in a litter of 4, the odds of having zero double merle puppies would be about 31%. Therefore, the risks associated with breeding merle to merle are very high and should be avoided.