This article by Dr. Willis explains why you should not breed the merle color in the Chihuahua breed. For our part, we have decided as a conscientious, ethical breeder respecting the Chihuahua breed not to reproduce the merle color. This color is not recognized by the Canadian Kennel Club (CKC) and therefore automatically not purebred. No ethical breeder respectful of the breed and its dogs would breed this color knowing all the health problems associated with it.
Free translation by Mountain Chihuahua:
“Following the information we know about this color, all chihuahuas of this color have a 36.8% to 54.6% chance of having a problem with hearing loss which in some cases goes as far as deafness. Merle is now a disqualification in the breed standard in Canada and the United States as well as several other countries.
The History of Merle Color: Merle-colored Chihuahuas have appeared in the breed over the past 15 years. No mention of this color is present in books covering the Chihuahua breed, or in books that list the genetics or patterns of Chihuahuas. This coat also appeared simultaneously in several other breeds as well (notably, poodles, cocker spaniels, miniature pinschers, etc.). The merle can come in a variety of color patterns, including red merle and blue merle. There may also be what is called a hidden or cryptic merle, where the merle pattern does not present itself, such as on a light-colored dog, or where the merle pattern does not cover a large area of the dog
The Merle gene itself is a dominant trait, meaning one of the parents must be a Merle or carrier of that gene for the gene to be expressed in a puppy. This is not the type of gene that remains hidden for many generations like a recessive gene. This color pattern is likely due to crossbreeding with other dog breeds that have the merles gene such as a dachshund. The merle Chihuahua was therefore created by falsification of the registration of a purebred dog. Although Merle color can resurface through genetic mutations, this is probably not the case, as this gene is the same one that is also present in Aussies, Dachshunds, Shelties, etc.
Ultimately, if you buy a Merle Chihuahua, you are probably not getting a purebred Chihuahua dog, but a genetically mixed breed dog (although one may actually have registration papers). Additionally, a large majority of Merle Chihuahuas are still very large/fat, in the 6-10 lb range, which is not respectful of Chihuahua breed standards.
Another much more serious and important problem is the higher frequency of health problems in Merle Chihuahuas. You may ask why, since Merle is only a color pattern? Well, unfortunately, unlike other colors, the merle gene acts on a color and brightens and whitens certain parts of it (creating patches)...bleaching is the cause of defects. Often, when a dog's coat is bleached, the pigment inside the ear and on their eyes is also bleached, resulting in many cases in deaf and blind dogs.
“Health Problems Associated with the Merle Allele”: Heterozygous (one merle parent, the other is a non-merle) and homozygous (both parents are merle) merle puppies may exhibit hearing and ophthalmic abnormalities, including mild to severe deafness, increased intraocular pressure, ametropia, microphthalmia and coloboma. The double merle genotype, homozygous, may also be associated with abnormalities of the skeletal, cardiac and reproductive systems. Based on information about the merle gene in dachshunds, all merle dogs have a 36.8% chance of developing some sort of hearing loss, resulting from either mild hardness of hearing to total deafness. This percentage results from research for puppies that result from one merle parent and the other that is a non-merle.
So, please keep in mind, if you are interested in getting a Merle Chihuahua, in addition to encouraging a breeder who does not have the health of these puppies at heart, you could get a puppy in poor condition. health. A puppy may appear to be healthy, but could actually have hearing or vision impairment.”
For more information on this study by Dr. Willis, and for his perspective on merle structure in Chihuahuas, please go to: http://chihuahuaclubofcanada.ca/images/stories/articles/willis -merle.pdf
For more information on the journey that led to the banning of the color at the Canadian Kennel Club please go to: http://chihuahuaclubofcanada.ca/images/stories/articles/banmerle.pdf
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