Tell the truth, or someone will tell it for you.
----Stephanie Klein
A rebuttal of the article written by Jack Vanderwyk, The Dilute Gene in Labrador Retrievers – Health
Problems and Behavioral Problems.
Written by Kristi Jenkins
A few months ago, an article (penned by none other than the self-proclaimed oracle of Labrador
genetics, Jack Vanderwyk) appeared on the Internet. Although Jack Vanderwyk is a talented and
creative writer, his articles are strikingly one-sided, with an inclination to slant more toward fiction
than fact. In an effort to dispel many of these untruths, I have provided a “rebuttal” of sorts to each of
his paragraphs from his article The Dilute Gene in Labrador Retrievers – Health Problems and
Behavioral Problems.
Vanderwyk: The American Kennel Club (AKC) (and all other reputable kennel clubs around the
world) recognizes three coat colors in the Labrador: black, yellow and chocolate. These colors are
inherited based on genes at two loci: B and E. In recent years, other colors have become more
prominent in the breed. Breeders refer to these colors as ‘silver’, ‘charcoal’ and ‘champagne’. In order
to obtain these new colors, a recessive D locus dilution factor (d) must be introduced into the
population. According to literature, the dilution factor was not originally a part of the Labrador
retriever breed, and therefore, controversy surrounds the topic.
Information known about the dilution factor’s lack of presence in the Labrador suggests that it was
introduced into the breed in the United States, at some point in time, probably in the late 1940s, early
1950s, by crossbreeding. Research has shown that some dogs with coat color dilution are prone to hair
loss and reoccurring skin problems. These conditions should be selected against by eliminating
dilution factors within the Labrador population.
Me: While the American Kennel Club (AKC) does indeed recognize three coat colors in the Labrador
retriever breed, Vanderwyk fails to mention that the AKC recognized dilute Labrador retrievers as a
“shade” of their base coat color. Thus, owners are directed by the AKC to register “silvers” as
chocolate, “charcoals” as black and “champagnes” as yellow. To verify this, I sent an email to the
AKC, stating I had obtained a “silver” Labrador puppy and was confused regarding the color
selections on the AKC form. AKC’s response was: “Silver Labs are registered as chocolate”. AKC has
stated again and again that registration of dogs is based on parentage, not color.
While Vanderwyk states that the dilution gene’s lack of presence suggests it was introduced in the
United States, there is documented and published evidence to dispute this.
The Labrador Retriever breed should be consistent with its breed standard, and dilute colored dogs
incorrectly represent the purebred breed. Dorothy Howe (who, by the way, is included in
Vanderwyk’s list of “Who is who in the world of Labrador retrievers”) included a very interesting
tidbit of information in her book, “This is the Labrador retriever”, published in Great Britain in 1972.
In her writings, Ms. Howe devotes a chapter to Labrador coloration. She divides the colors into the
following: 1) Black and Chocolate, 2) Yellow, 3) And Other Kinds. She proceeds to reveal that, “in
both the past and present, there have been grey puppies of a lovely silver color at whelping, but they
very soon start to darken”. Those of us who have bred dilute black (charcoal) puppies in our litters
can relate quite well to this quite accurate description of dilute black puppies. Furthermore, in the
book “The Labrador Retriever” (published in Great Britain in 1957), additional evidence abounds to
suggest the dilution gene did indeed exist. The author, Lorna, Countess Howe (who is also named in
Vanderwyk’s list of “Who is who”) describes the English Kennel Club Standard (of 1950) as follows:
“The colour is generally black or yellow but other whole colours are permitted”. Whole colours? The
pluralization of the word “colour” leads me to believe Lady Howe is referencing more than one other
color besides black and yellow. She goes on to add, “The coat should be free from white markings
but a small white spot on the chest is allowable. The coat should be of whole colour and not of a
flecked appearance”.
Vanderwyk also states that research has shown that some dogs with coat color dilution are prone to
hair loss and reoccurring skin problems. While this is true, I feel that it is prudent to add that some
breeds are much more prone to dilution-related skin issues than others. In conversations with my
veterinarian (who has been practicing veterinary medicine for over 30 years), it is revealed that
Doberman pinschers and Pit bulls are the most commonly affected. He stated he has never seen
(nor heard of) a Weimaraner with skin issues, as they seem to be unaffected by the dilution gene in
that sense. So, let’s revisit that. Vanderwyk (and other dilute Labrador haters) adamantly claim
that Weimaraner was introduced into the Labrador retriever gene pool. They also claim that dilute
Labrador retrievers are prone to skin issues. Yet, Weimaraners seem to be unaffected by colordilution related skin issues. Hmmm…..
In regards to Vanderwyk’s seemingly indisputable claim that there is no other explanation for the
presence of the dilution gene other than crossbreeding, I partially agree (bear with me here….). As
most of us know, many breeds were used to refine and develop the Labrador retriever breed as we
know it today. A simple Internet search will provide information about the infusion(s) of other
breeds, including Newfoundland, Chesapeake Bay retriever, and Flat coated retriever. In fact,
Vanderwyk states in an article, “Obviously one didn't want the public to know that one's high
ranking field champions' bloodlines were mixed with those of Flat coated Retrievers, Chesapeake
Bay Retrievers and Golden Retrievers”. The late Mary Roslin Williams is heralded as one of the
foremost authorities on the Labrador retriever breed. In her 1986 speech to the Labrador Retriever
Club, she mentions having first-hand knowledge of breeders who used Foxhounds, Greyhounds and
even Border Collies in their Labrador retriever breeding programs. Each breeder was seeking to
refine a unique set of skills. For example, Greyhounds were introduced to attempt to add speed to
the English Field Trial dogs. Of the breeds we have mentioned, which are documented to have been
used in the formation of the Labrador retriever breed, we can see the following with regard to the
status of the dilution gene in that breed:
Newfoundland – Dilute gene exists.
Chesapeake Bay retriever – Dilute gene exists.
Flat coated retriever – Dilute gene does not exist.
Foxhound – Dilute gene exists
Greyhound – Dilute gene exists
Border collie – Dilute gene exists
I find it quite interesting that, of the 6 breeds documented to have been used in the creation of
today’s Labrador retriever, the dilution gene naturally exists in 5 of them.
Vanderwyk: The Labrador retriever breed, as it was developed and registered in the United
Kingdom, never (until 2006) carried the dilution factor. A survey in the United Kingdom, Europe,
Canada and the United States shows that no reputable Labrador breeder has ever had a puppy
carrying the dilution factor, so it is hard to explain the direct cause of a mutation in the breed. There is
no other explanation than that crossbreeding occurred with a breed carrying dilution, probably the
Weimaraner, and they passed the d allele down to offspring.
Me: How can it possibly be determined that the dilution factor was never present in the United
Kingdom? Recessive genes can lie undetected for many generations. Until two recessive genes
came together, the presence of a recessive gene such as dilution would have gone undetected.
Vanderwyk states, “There is no other explanation than that crossbreeding occurred with a breed
carrying dilution, probably the Weimaraner, and they passed the d allele down to offspring”. The
Weimaraner is one of over 40 canine breeds carrying the dilution gene. I firmly believe we have
adequately displayed that there are numerous potential and acceptable inlets for the dilution gene
in the Labrador retriever.
Vanderwyk: There are many breeders in the United States who specialize in breeding diluted
“Labradors”. Diluted dogs typically have a metallic-looking sheen to the hair. A typical Labrador with
a black phenotype can have the genotype: BBEE, BBEe, BbEE or BbEe. A Labrador with a chocolate
phenotype will have either the bbEE or the bbEe genotype. A dog displaying a yellow coat must have
the homozygous recessive genotype at the E locus, and therefore can be BBee, Bbee or bbee. It is
possible for these genotypes to be diluted if the dog carries two copies of the recessive dilute gene, dd.
Dogs that carry at least one D will not have a diluted coat. If a dog carries the Dd genotype at the D
locus, one copy of the dilute gene is present. If bred to a bitch carrying a dilute gene (Dd or dd),
diluted offspring could be produced.
Me: I actually agree with most of the above paragraph. My only dispute is that diluted dogs
typically have a metallic-looking sheen to the hair. While we might describe dilute chocolates or
dilute blacks as having a “metallic sheen” to their coats, dilute yellows can often not be identified
from standard yellows. In fact, there is now a dilute yellow (champagne) conformation champion.
The dog appears standard yellow in all ways, yet carries two copies of the dilution gene.
Vanderwyk: Various expressions of the dilution gene have been noted. Some dogs with dilute color
display minimal or no health problems; other dogs experience hair loss and skin problems. Color
dilution alopecia (CDA) and black hair follicular dysplasia (BHFD) can accompany coat color dilution.
These diseases cause recurrent skin inflammation and drying, bacterial infections of hair follicles and
severe hair loss. Late 2013 a 12-week-old female silver Labrador retriever was submitted to the
Comparative Ocular Pathology Laboratory of Wisconsin, and was diagnosed with Malignant Uveal
Schwannoma. Scientists believe that the dilute color mutation may contribute to the cause.
Other disorders that could travel with the dilution gene are heritable Weimeraner genetic issues such
as trembling disorders, autoimmune related vaccination sensitivity and intolerance, Von Willebrands
Disease, hyperuricosuria causing painful bladder and kidney disease, and behavioral problems that
are more common in the Weimaraner, such as separation anxiety, and dominant, protective,
territorial temperament. Minimizing occurrence of these conditions would mean minimization of the
dilute mutation. Selection against dilution is important in breeds that display health issues associated
with the mutation. It is also important to minimize the dilution mutation in breeds that do not have a
standard written which include these colors. The Labrador Retriever is currently one of these breeds.
Dilute colored Labrador retrievers are a disqualification according to breed standards. Those dogs
carrying the dilute gene should not be registered as purebred Labrador Retrievers.
Me: As discussed in a previous paragraph, some skin conditions can exist in dilute dogs.
Weimaraners very rarely have skin issues associated with the dilution gene, while other breeds
(Doberman pinschers, Pit bulls) seems to be more adversely affected. My veterinarian recommends
a high quality diet (no corn, wheat or soy) and supplementation with Omega Fatty Acids for ANY
Labrador retriever, regardless of color. Vanderwyk’s attempt to strike fear in the general
Labrador retriever public with claims of inherited Weimaraner diseases and conditions is wholly
without merit. I believe I’d be reluctant to consider Vanderwyk an authority on the transference of
Weimaraner issues to the Labrador retriever when he is unable to correctly spell the word
“Weimaraner” in his article. Vanderwyk’s veiled claim that a particular eye tumor (Malignant
Uveal Schwannoma) is prevalent in dilute Labrador retrievers is absolutely preposterous. To date,
there has been only one documented case of Malignant Uveal Schwannoma in a dilute Labrador
retriever. Although it does affect more blue-eyed dogs, one lone case hardly provides fodder to
proclaim a genetic propensity. Perhaps Mr. Vanderwyk would be better served to pursue breeders
of known Labrador retriever disorders such as Exercise Induced Collapse (EIC). Studies have
shown the prevalence of Exercise Induced Collapse trait in standard colored American Field Labs to
up to 38%. Now, this is an outrage! Exercise Induced Collapse is a disease that can kill. A mere
color cannot.
The Labrador Retriever Club Inc. is the AKC Parent Club of the Labrador Retriever. On May 12, 2014,
the LRC published the following message on their website: “Very exciting news – the OFA has agreed
to maintain a database of Labradors who have been permanently identified (microchip or tattoo ) and
have been tested for the d gene. Dogs having the genotype dd will be listed as affected, Dd as carriers
of the dilute gene and DD as clear of the dilute gene. This is great news for us.”
Note: The Orthopedic Foundations for Animals (OFA) only registers hereditary diseases (or
the lack of those) in their databases. So it’s not a simple matter of “a different colour”.
Me: In my opinion, the Orthopedic Foundation for Animals (OFA) created this registry to allow
Black/Yellow/Chocolate (BYC) purist breeders a “gathering place” of sorts. OFA (and most dilute
breeders) recognize the desire and right of BYC breeders to keep their lines free of the dilution gene.
The database allows owners to record the dilute color test results of their dogs. To date, this
database is still in the developmental stages. It is not listed anywhere on OFA’s website, nor is it
listed under their “Pilot databases”. I think it is important to add, it is, by no means, an attempt by
OFA to collect data on (or track the existence of) dilute Labrador retrievers. In fact, I seriously
doubt if any information on dilute dogs has even been submitted to OFA. In addition, the only
“hereditary diseases” of Labrador retrievers for which OFA recommends testing are: 1) hip
dysplasia, 2) elbow dysplasia, 3) eye examination by a boarded ACVO ophthalmologist, 4) Exercise
Induced Collapse and 5) Centronuclear Myopathy (Optional). The dilution gene is not mentioned by
OFA as a health concern or a disease for which testing needs to take place.
Vanderwyk: Although findings of these various studies do not definitively explain the cause of
dilution in dog coat colors, they help us to understand the correlation between dilution and the MLPH
gene. Knowledge that the MLPH gene mutation is responsible for dilution has allowed DNA testing
companies to begin testing for the mutant dd allele. These tests can help identify carriers of the d
gene, and therefore, can help to eliminate it from populations, such as the Labrador retriever, in
which it is undesirable. Responsible breeders should take the time, and spend the money, to have
their breeding stock genetically tested at the D locus. Labradors displaying dilution, ‘silver’,
‘champagne’ or ‘charcoal’, coloration (dd) should not be used for breeding. Ideally, only Labradors
with genotype DD at the dilution locus should be used for breeding.
Throughout the years, Labrador breeders have worked diligently to eliminate undesired traits and
illnesses in the breed. A complete elimination of coat color dilution in the Labrador retriever would
take a very long time, through DNA testing and breeding stock selection. Kennel clubs and breed
clubs are expected to respect the breed standard and the closed character of the studbooks. No respect
of the breed standard and the closed character of the studbooks is shown by the common practice of
registering “silver” as chocolate, “charcoal” as black, and “champagne” as yellow. Labrador retriever
breeders are equally expected to follow the breed standard as currently written when selecting parents
for future litters.
Me: I actually agree with Jack that elimination of the dilution gene in the Labrador retriever
population would take a very long time. In fact, at this point, I truly believe it is impossible. Since
dilute dogs are registered with AKC under their base coat color, it is impossible to estimate the
number of dilute Labradors in existence. However, I approximate it to be in the thousands.
Vanderwyk: The AKC registration of “silver”, “charcoal” and “champagne” dogs as chocolate, black
or yellow Labrador Retrievers, without any restrictions, has resulted in the disturbing fact that in 2011
the first American dilutes were imported into the United Kingdom, and that these dilutes were
registered by The Kennel Club, also without any restrictions. As a result, hundreds of dilutes were
born in the United Kingdom, and most of them were registered by the K.C. as completely normal
black, chocolate or yellow Labrador Retrievers. The Kennel Club told the Labrador parent club that
“DNA-tests” proved that these dogs were purebred Labrador Retrievers, and that there was nothing
they could do about it.
The Kennel Club did not mention when these “tests” took place. However, it’s a matter of fact that
these tests are extremely unreliable. Yes, the tests could show that the parents and grandparents of a
certain dog are Labrador Retrievers, but does that make a dog a purebred Labrador? Even the most
modern and sophisticated tests are not able to say something about anything that happened more
than three generations ago, while many dilutes have a history that goes back to the 1970s, or even to
the 1950s.
So, instead of using an extremely unreliable test to “prove” that a Labrador is purebred, the K.C.’s
should use a test that is reliable: any dog carrying the d-gene can not be a purebred
Labrador Retriever and should be excluded from the registry.
Me: My summary of the two previous paragraphs is that Vanderwyk is the epitome of a sore loser.
Nothing more. Not only do dilute Labrador retrievers exist in the United Kingdom, there are
established breeding operations in Belgium, Germany, Denmark, New Zealand and South America
(to name a few). Simply put, the dilute Labrador retrievers are here to stay.
References

Howe, D. This Is The Labrador Retriever. T.F.H. Publications, Inc. Ltd., Surrey 144.

Howe, L. 1978. The Labrador Retriever. Arco Publishing Company, New York. 55.

Duke, F.D., L.B. Teixeira, L.E. Galle, N. Green, R.R. Dubielzig. Malignant Uveal Schwannoma
With Peripheral Nerve Extension in a 12-Week-Old Color-Dilute Labrador Retriever. Vet
Pathol, Feb 10, 2014.

"Newfoundland Breed Standard." Newfoundland Club of America: The Breed Standard for
the Newfoundland Dog. N.p., n.d. Web. 08 Feb. 2015.
<http://www.ncanewfs.org/standard.shtml#.VNeD-p3F_TA>.

Vanderwyk, Jack. "WHO'S WHO in the World of Labrador Retrievers." WHO'S WHO in the
World of Labrador Retrievers. N.p., n.d. Web. 08 Feb. 2015.
<http://labradornet.com/whoswho.html#W>.

"Flat-Coated Retriever Breed Standard | American Kennel Club." Flat-Coated Retriever Breed
Standard | American Kennel Club. N.p., n.d. Web. 08 Feb. 2015.
<http://www.akc.org/breeds/flat_coated_retriever/breed_standard.cfm>.

"Dog Coat Colour Genetics." Dog Coat Colour Genetics. N.p., n.d. Web. 08 Feb. 2015.
<http://www.doggenetics.co.uk/dilutes.html>.

National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web.
08 Feb. 2015. <http://www.ncbi.nlm.nih.gov/pubmed/24513800>.

National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web.
08 Feb. 2015. <http://www.ncbi.nlm.nih.gov/pubmed/24513800>.

Clark, Roger W., DVM. "The Dilution Gene in Dogs and Potential Risks." Personal interview.
05 Feb. 2015.

Williams, Mary Roslin. "Mary Roslin Williams Speech to the Labrador Retriever Club - 1986."
Audio blog post. N.p., n.d. Web. <https://www.youtube.com/watch?v=kFlng4i8_R4>.