The merle gene is the reason for the colorful coat worn by the Catahoula. This coloration is due to a mutation in the merle gene that causes dilution of the solid colors and creates a combination of hues within a color. It is this same gene acting in the Australian Shepherd, Collie, Great Dane, Beauceron, Shetland Sheepdog, Dachshund, and other breeds that display the mottled coat.
For many years the Catahoula has been grouped with these breeds, and it was believed that the gene acted the same in all breeds. A recent DNA study performed at Texas A&M by Leigh Anne Clark, Ph.D., suggests that there may be a modifier gene having an effect on the merle gene within the Catahoula. This study has shown that there are more merle and double merle Catahoulas being used in breeding programs than originally believed. There are many colored dogs with normal hearing that have been tested and shown to be double merles. All of the dogs in the Texas A&M study were BAER tested, and many of those tested were double merles.
The tests which were performed at Texas A&M have given way to the hypothesis that there is a tremendous amount of the phantom merle allele running around in the Catahoula. The study has shown that there are more merle and double merle Catahoulas being bred than non-merles. A large majority of dogs that are phenotypically identified as solid-colored Catahoulas may actually be merles. This is known as Ghost merle or Phantom merle, and cannot be detected without DNA testing. The breeding of a solid-colored dog to a merle dog may appear to be a safe method of breeding; however, not knowing for certain that the solid colored dog is actually a non-merle, can result in the breeding of merle to merle. Knowing if a dog is non-merle, merle, or double merle can only be proven via DNA tests.
The double merle, which has in the past been phenotypically identified by many as a white dog, may actually have a full colored coat in the Catahoula. This proves that phenotype cannot be used to identify a double merle. The only means of identification is via DNA testing which is currently being offered by GenMark, of Vita-Tech Laboratories.
It has long been thought that the double merle was the cause of the deafness in the Catahoula; however, a Double Merle Male was bred to a Double Merle Female, and produced a complete litter of Double Merle puppies. The result was a litter of pups that were fully colored and without deafness. This gives way to the thought that there is something having a positive effect on a double merle breeding in Catahoulas that is not present in other merle breeds. Could it be that the feared double merle is not as dangerous in the Catahoula as it is for other breeds?
I have been breeding dogs for over 25 years, and since 1994 have been breeding merle to merle as a part of my breeding program. The manner in which I began this program was to study the Sire and Dam, and the litters in which they belonged. I would also study the Grand Sire and Grand Dam and the litters in which they belonged. I found that identifying coat and eye coloration, as well as the problems any of the pups may have had, gave me a better idea of what may be produced when a pair was bred.
Anyone from whom I've purchased a dog can attest to the questions about lineage and litters. I've asked some questions that some breeders would be very reluctant to answer. I've been sworn to secrecy on some of those answers and they will remain with me forever, but, if those questions were not asked and answered, I would not have been able to achieve the results that I have.
Keeping records of the breeding and the litters aided in what was working well, and what was not working. By studying those results, it presented a picture of which dogs could or should be bred together. Knowing which dogs to breed resulted in reducing the deafness problem which plagues many kennels. When I first started the merle to merle program, my deafness ratio was about 25 percent, and still well below the average. Today, it is about 9 percent. It has been reduced by more than half, simply by studying the litters instead of just choosing a male or female to breed based solely on color.
There are many breeders that will tell you to keep away from breeding white dogs, but will purposefully breed for white collars, blazed faces, and white feet. In most breeds, this combination is commonly known as Irish Spotting. Irish Spotting is a division of the Piebald gene, and many dogs that have been identified as double merles have a pattern similar to Irish Spotting, either appearing in the feet, neck, or face. The Piebald gene regulates the merle gene - so while they are related, this does not mean that Catahoulas actually have the piebald mutation. In fact, it probably shows why the merle gene can cause a pattern that looks like piebald. There is no way to prove this until a test for piebald is available. Could it be that breeding for "Irish Spotting" in merle dogs is adding to the deafness problem in the Catahoula?
When I wrote my book, I stated that when breeding Catahoulas (merle) light to light should be avoided. Dark to light, medium to light, medium to medium and dark to dark in merle dogs should produce the better results. Well, after all the testing that has been performed, and a breeding program culminating 12 years, that statement still holds true. If any breeding of light colored, or white, Catahoulas is to be performed, it should be done with a dark merle or non-merle dog coming from a litter of pups that were medium to dark in color.
Now that DNA testing can identify merle and non-merle, it is beneficial to the breeder to have their dogs DNA tested. Knowing that you are about to breed a light colored double merle to a non-merle, which will produce a complete litter of single merle pups means less chance of defective pups being born. Today's breeder has more tools at their disposal than ever before, and those that refuse to use the tools will only be hurting the breed as a whole.