Merle Rat Terriers
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In the early part of the 20th Century in America, the Rat Terrier (also called ‘Feist’ at that time) were abundant especially on farms and homesteads, filling the role of hunter/watchdog/companion.
Beagle was added for a better nose for hunting, while supposedly Whippet and Italian Greyhound were added for speed. It’s been rumored that Bull Terrier was added for strength and, in other areas, the rumor includes Welsh Corgi and/or Dachshund for additional hunt and toughness. It was President Teddy Roosevelt who used these Feists to rid the White House of a rat infestation. The President’s dogs were so effective at dispatching vermin, that the President called them his Rat Terriers and the name stuck. As the breed continued to evolve, it’s been noted that Toy Fox Terriers (which were developed using Fox Terriers and Chihuahuas) that did not fit the standard of the TFT were bred back to Rat Terriers. In the 70s, Chihuahuas and Dachshunds were also (openly) added into the fold.
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With the many different breeds that helped create our modern day Rat Terrier, the main one being the ‘Feist’, there should be no wonder why they vary in size, color and pattern. Until recently, two varieties shared the name Rat Terrier. The taller, almost square-bodied type is known as Type A or simply Rat Terrier, and the shorter, longer bodied known as Type B. The Type B Ratties are now known as Teddy Roosevelt Terriers.
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It’s difficult to dislike all varieties of the Rat Terrier as this breed has so much to offer and fits many different lifestyles. There are different Registries that cater to the differences of the Ratties. Some include both body styles calling them Type A (Rat Terrier) and Type B (Teddy Roosevelt Terrier) and one recognizes three sizes (Toy, Mini and Standard). Aside from body type and size, the main controversy in this breed is the inclusion, or rather the exclusion, of two color patterns – Brindle and Merle.
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The Foundation Breeds that makes up the gene pool for Rat Terriers, like the Feist, Corgi, Chihuahua and Dachshund, clearly have brindle and merle as a part of their color pattern. Brindle is that stripe pattern which is a co-dominant gene. As a co-dominant gene, it is easily hidden or masked by other dominant or co-dominant genes such as the colors chocolate, red and tan. The brindle pattern is more of a personal preference where breeders may or may not breed for it. There are no known health problems associated with the brindle. You only need one parent to carry the brindle gene in order for it to crop up in a litter. So why was brindle removed from current Rat Terrier standards? That was decided by a handful of breeders who wrote the standard, who believe the brindle gene muddies the striking look of a bi-colored or Tri-colored Rat Terrier. So simply due to their taste and preference, no legitimate reason, the color was declared a disqualification.
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Merle is another controversial coat pattern, yet it is found in Feist, Dachshund, Chihuahua, and Cardigan Welsh Corgi, all of which are ancestors of the Rat Terrier. The proper breeding of merle dogs does require some education on the part of the breeder, but it is a dominant gene that cannot be carried, and therefore is not difficult to manage. The simple rule is to never cross 2 merle dogs, as there is a possibility of health issues in some of the puppies. It is also not wise to cross merle with color patterns such as sable and recessive red that can mask the merle pattern and create hidden (cryptic) merles that can be mistaken for non merle. When bred properly, there are no health concerns with merle. Many dog breeds have merle, and many educated breeders manage it safely and successfully. Merle IS a disqualification in the AKC conformation ring, but they can compete in any other AKC event. There are a number of outspoken rat terrier breeders, mostly members of the nearly defunct RTCA, (the assoc. that originally removed Merle & brindle from the list of accepted colors) that are very outspoken against the Merle coloring, spewing lies as facts, that rat terriers can’t be Merle, they must be crossbred to be Merle, that akc won’t register Merle, etc…..all incorrect.
AKC absolutely does register Merle, even though it’s a DQ in the conformation ring (only because the rtca members deemed it so). Here it is straight from an email from AKC, and the AKC website….
“Right off AKC web site:
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“Can dogs be registered with a color or marking that is considered a disqualification in Conformation according to the breed standard?
Decisions about acceptable colors and markings for registration and Conformation competition are made by the national breed clubs for each of the respective breeds. In addition to color information in the breed standards related to Conformation, the national breed clubs also determine what colors may be used in the registration of their breed. While some colors may be disqualifications within the breed standard, dogs of a disqualifiable color may still be registered.”
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By northwoodratterriers.com
AKC & Merle Rat Terriers
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“Can Dogs be registered with a color or marking that is considered a disqualification in conformation according to the breed standard? Decisions about acceptable colors and markings for registration and conformation competition are made by the national breed clubs for each of the respective breeds. In addition to color information in the breed standards related to conformation, the national breed clubs also determine what colors may be used in the registration of their breed. While some colors may be disqualifications within the breed standard, dogs of a disqualifiable color may still be registered.” – AKC
The news about Merle – It’s All Good! Some Rat Terrier breeders feel the need to make negative comments about the merle coat pattern in the Rat Terrier…making claims that these dogs cannot possibly be purebred, and insisting that all merle dogs have health problems.
These claims are simply not true…and the breeders distributing this misinformation are doing so in the interest of their own financial gain. If they can scare you away from buying a merle puppy, then they can sell you one of THEIR puppies.
It’s all about marketing. Pure Breeding As for the origin of the merle pattern in the Rat Terrier, it traces back to the Feist, which is the primary ancestor of the purebred Rat Terrier as we know it today.
Feists come in all colors and coat patterns, including merle and brindle. Registration Due to dog show and breed club politics, the AKC breed standard was written to exclude merle (and brindle) from the conformation show ring. However, non standard colors and patterns may still be registered with AKC, and the dog can compete and title in any other AKC event except conformation. Our puppies are AKC registered and AKC limited (non breeding) registration is included as part of your puppy purchase.
Health Issues – There IS the risk of possible health problems (most often eye and ear defects) associated with the merle gene, but this risk ONLY occurs when two merles are mated together. As merle is a simple dominant gene (it cannot be carried), it is NOT complicated to work with…the simple way to avoid any health issues is to always breed a merle to a non-merle. As long as a merle Rat Terrier has one non-merle parent, it has no risk of being any less normal & healthy than a non-merle Rat Terrier!
NO RESPONSIBLE BREEDER WILL EVER CONSIDER CROSSING 2 MERLES!
Merle is common and accepted in a number of other dog breeds. If those breeders can educate themselves about how to properly manage merle genetics, and breed healthy dogs, Rat Terrier breeders can do the same. Merle is here to stay, and increasing in popularity as more and more Rat Terrier fanciers discover these beautifully colored dogs, no two of which are marked exactly alike.
by northwoodratterriers.com
Deafness and the Merle Gene
George M. Strain, PhD
Professor of Neuroscience
Louisiana State University, Baton Rouge, LA
Of all the domestic species, the canine has the greatest variation in size, shape,
and skin pigmentation pattern.1 Results from classical genetic studies in the last
century identified at least ten genetic loci that determine coat color and pattern,
represented by the letters A, B, C, D, E, G, M, P, S, and T.2 Two of these genes,
S (piebald) and M (merle), have been linked to the appearance of congenital
hereditary deafness. The S series has one dominant and three recessive alleles:
the dominant S allele produces a solid coat color, while the recessive alleles si
(Irish spotting), sp (piebald), and sw (extreme piebald) produce increasing
amounts of white in the coat and skin. The Dalmatian breed is homozygous for sw
and is the breed with the highest prevalence of deafness: 30% are deaf in one or
both ears. Other breeds carrying recessive piebald alleles with deafness
problems include the bull terrier, English setter, English cocker spaniel,
Australian cattle dog, and Jack Russell terrier.
The second pigmentation gene associated with deafness is merle. The dominant
allele M acts on uniform pigmentation to produces an alternating pattern of dark
versus light that is also known as dapple. The recessive allele produces uniform
pigmentation when the dog is homozygous (mm). Heterozygous merle (mM) in
an otherwise black dog produces a blue merle, and in an otherwise brown dog
produces a red merle. Dogs homozygous for the dominant allele (MM) can be
mildly affected to the naked eye or severely affected, depending on breed and
even varying within a breed. Severely affected MM individuals are often nearly all
white, deaf, sterile, and blind or affected by various visual abnormalities. Merles
are commonly seen in the collie, border collie, Australian shepherd, Shetland
sheepdog, Cardigan Welsh corgi, dachshund, and Great Dane breeds; other
breeds less commonly known to carry merle are the chihuahua, American pit bull
terrier, American Staffordshire terrier, Beauceron, Catahoula leopard dog, Koolie,
poodle, Pyrenean shepherd, Old English sheepdog, American cocker spaniel,
pomeranian, Hungarian Mudi, Norwegian dunkerhound, and others.
Many of the breeds that carry merle also carry piebald. Whether it linked to S, M,
or other causes, congenital deafness has been identified in nearly 90 breeds,3
nearly all of which carry piebald, merle, or both. While we know that the piebald
gene is inherited as a simple recessive and the merle gene as a simple
dominant, the inheritance of deafness resulting from either gene does not appear
to be inherited in a simple Mendelian manner – I’ve bred deaf Dalmatian to deaf
Dalmatian and gotten bilaterally hearing puppies. Our data analyses suggest that
the inheritance involves more than one gene: M or s and another gene that
modifies how strongly the first gene acts.
Relatively few studies of the merle gene have been published, most coming from
studies of a breeding colony of merle dachshunds kept at a university in
Hanover, Germany. One study4 examined auditory function in the animals, and
several (e.g. reference 5) examined visual function. From these limited studies of
an inbred population in one breed, subsequent authors have, unfortunately,
extrapolated the reported findings to apply to all merle-carrying breeds. Current
work in our and other laboratories and the experiences of many breeders have
shown that the actions of merle have usually been over-stated. Reetz et al.4
reported hearing results for 38 dachshunds (Tekels in German): 11 double
merles, 19 single merles, and 8 non-merles. They found hearing loss – slight to
total, unilateral or bilateral – in 54.6% of double merles, in 36.8% of single
merles, and in none of the non-merles. Hearing was tested using the brainstem
auditory evoked response (BAER), determining the threshold to click stimuli
under sedation. Any threshold above 20 dB was considered to be abnormal, not
because that is an accepted standard, but because one of their non-merle dogs
had a 20 dB hearing threshold. Only one dog – a double merle male – was totally
deaf in both ears (threshold > 90 dB) and none of the dogs were totally deaf in
only one ear (unilaterally deaf). Looked at this way, true bilateral deafness
occurred in 9.1% (1/11) of the double merles and 0% of the single merles.
How can the reported hearing loss in the remaining single and double merles be
explained? The pigment-associated deafness seen with the piebald and merle
patterns typically presents as total deafness in one or both ears, based on all of
the histological studies that have been reported, so the partial hearing loss
reported by Reetz is not likely to be genetic and associated with the merle gene.
Instead, it most likely reflects a combination of poor aural hygiene (dirty ear
canals), middle ear infections, and noise-induced hearing trauma. The noise level
in institutional kennels is notoriously high, and exposure to high noise levels
produces cumulative hearing loss. Dogs in large kennels also usually do not
receive regular ear cleaning, leading to build up of excess cerumen and
infections, both of which muffle the sound reaching the inner ear. Interestingly, of
the 15 “hearing impaired” ears with thresholds between 25 and 50 dB, only 3
were in males. Perhaps differences in kennel housing for females exposed them
to greater noise levels in the whelping kennels. Regardless, the hearing loss
reported in these dachshunds that can be attributed to a genetic cause is much
lower than stated in the published English abstract of this German publication.
In 2006 the gene responsible for the merle pattern in dogs was identified and
sequenced6 and a commercial DNA test is now available to determine whether a
dog is a single or double merle. In an unpublished study performed by myself
and these investigators at Texas A&M University,7 70 merle dogs from five
breeds (Shetland sheepdog, Australian shepherd, collie, Great Dane, and
Catahoula leopard dog) had BAER hearing tests performed and merle genotype
determined by DNA tests. Of 22 double merles, 8 were bilaterally deaf (36%) and
2 were unilaterally deaf (9%). Of 48 single merles only one was unilaterally deaf
(2%), a Great Dane that also carried the piebald gene, raising a questions as to
the cause for the deafness, and none was bilaterally deaf. Based on Reetz’s
study about one third of the single merles would have been expected to have
significant hearing loss.
An interesting finding came from our group of 70 dogs: 15 of the double merles
were Catahoulas, but only 4 of them were deaf in one or both ears (27%), while
86% of the double merles in the other breeds (Shetland sheepdog, Australian
shepherd, collie) were deaf. This suggests a breed difference for the impact of
the merle gene on hearing status, which may not be surprising since most double
merle Catahoulas are heavily pigmented compared to double merles in the other
breeds. We are continuing to test additional dogs to further document and
understand these differences.
What do experienced breeders in merle-carrying breeds have to say? I cannot
present any numbers because I have not done formal surveys, but I’ve
repeatedly heard from long-time breeders who say that they seldom if ever get
deaf or blind dogs from breeding merle ı merle, especially in the dachshund and
Catahoula breeds. There is no denying that such outcomes do occur, especially,
it would seem, in the collie-type breeds, but we do not at this time know the
determinants or conditions that produce deaf or blind dogs.
What is to be done, then, about the merle gene? It seems clear that merles in
some breeds, especially double merles, present a problem. In other breeds the
problem is significantly less problematic. It might be said that recent efforts in
several national breed clubs to ban merle completely from the breed standard is
throwing out the baby with the bath water. Others would argue that the
production of even small numbers of puppies with auditory or visual defects is an
adequate reason to eliminate the pattern. If we completely understood how merle
works and what determines deaf or blind merle puppies, it might be easier to
assert with confidence the right way to proceed. Leaving aside the ascetics of the
merle pattern appearance, a matter of personal preference, we can say with
confidence based on current data that single merles have a very low likelihood of
deafness. Double merles in some breeds – Catahoula, dachshund – have a finite
but still low probability of being deaf, while double merles in some other breeds –
the collie-type breeds – have a high likelihood of producing deaf. Knowing how
strongly double merle dogs are impacted within a breed should provide guidance
to breeders on whether they should avoid breeding double merles. Researchers
will provide some guidance, but unfortunately the studies will take some time. In
the mean time it seems prudent to delay making difficult-to-reverse changes in
breed standards based on limited information. In most cases the breed standards
have been in place for many decades; a few more years of waiting won’t bring
about the end of the world while we develop a better understanding of merle.
References
1. Ostrander EA, Wayne RK. 2005. The canine genome. Genetic Research
15: 706-1716.
2. Little CC. 1957. The Inheritance of Coat Color in Dogs. New York: Howell
Book House, 194 pp.
3. Strain GM. 2007. Deafness in Dogs and Cats.
http://www.lsu.edu/deafness.deaf.htm.
4. Reetz, I, Stecker, M, & Wegner, W. 1977. Audiometrische Befunde in
einer Merlezucht [Audiometric findings in dachshonds (merle gene
carriers)]. Deutsche Tierärztliche Wochenschrift 84, 273-277.
5. Klinckmann G, Koniszewski G, & Wegner W. 1986. Light-microscopic
investigations on the retinae of dogs carrying the merle factor. Journal of
Veterinary Medicine A 33:674-688.
6. Clark LA, Wahl JM, Rees CA, & Murphy KE. 2006. Retrotransposon
insertion in SILV is responsible for merle patterning of the domestic dog.
Proceedings of the National Academy of Sciences103:1376-81.
7. Clark, LA, Wahl JM, Rees CA, Strain GM, Cargill EJ, Vanderlip SL, &
Murphy KE. 2007. Canine SINEs and their effects on phenotypes of the
domestic dog. In: P. Gustafson, ed. Genetics of Disease (in press).
The Author
George M. Strain is a professor of neuroscience at the LSU School of Veterinary
Medicine, where he has studied deafness in dogs and cats for over twenty years.
His training is in electrical engineering, biomedical engineering, physiology, and
neurology. More information on deafness can be found on his Deafness in Dogs
and Cats web site: www.lsu.edu/deafness/deaf.htm.