About chocolate Havanese
by Robin Mosher of Havanasilk 

 When I first became interested in breeding for chocolate Havanese, I began to hear an undercurrent of murmurings, little snippets of remarks that seemed to suggest that breeding chocolate Havanese to chocolate Havanese was taboo, ethically wrong, and an invitation to a myriad of crippling health problems.

 

As a student of canine genetics I could not fathom what they were talking about, as breeding chocolate to chocolate in other breeds has routinely produced so many well known working hunting dog breeds (gundogs, flushing dogs) in which beautiful chocolate pigmented dogs are far more common than black-pigmented ones. Several, centuries old, well established breeds carry ONLY chocolate genes including
Spinone, Kleiner Münsterländer, all four German Pointer breeds, Weimaraner, Brittany Spaniel, Field Spaniel, even the English Springer Spaniel. These breeds have no more (or less) incidence of health issues than their black pigmented cousins, and a quick search of OFA databases will easily confirm that.

 

My next step was to ask for ANY documentation of chocolate to chocolate Havanese breedings producing any more or any unusual health issues. When such documentation was not forthcoming, I was told it was because the crosses were never done so there wasn't any documentation to provide.

 

Odd, because a search of the Havanese database, "Havanese Gallery" lists colors and parentage colors so it was a fairly simple exercise to hand pick several names of dogs with two chocolate parents and enter them at OFA. While many of the dogs were not showing any health testing, those that did have the CHIC tests performed had no particular issues to report.

 

So why do some Havanese breeders (and surprisingly breeders who brag about breeding chocolate puppies) spread these malicious myths?

 

Well, to be fair, in Europe, the chocolate Havanese was not recognized in the FCI Standard until recently, and furthermore, there are true anecdotes in other breeds of culling chocolate puppies at birth to try and eliminate the gene and "purify" the "race". Most notably, in the 1800's, chocolate Labradors were routinely killed and those that lived were not registered. It did not, however, eliminate the chocolate gene from the breed. Brittany Spaniels took a bit different stance and eliminated what they THOUGHT was black pigmentation from their breed, which was later shown to be a very dark chocolate pigment and subsequently DID end up damaging their gene pool.  

 

Further still, there are certain Havanese who carry a recessive gene for dilution, and dilution of color in ANY pigment carries health risks and primarily potential autoimmune weaknesses like pemphigus and skin conditions. A true dilution pigment in a chocolate pigmented dog looks almost pink...pale pinkish nose, skin, pale chocolate tinted hair. In a black pigmented dilution, you will see a pale blue or grey nose, pale grey skin, etc. (For researchers of Blue Havanese, pale blue (black dilute) is NOT a derivative of a true blue pigmented dog who looks almost black pigmented but with a silvery to blue cast).

Trying to explain color transmission is difficult unless you know basic information on color inheritance that apply to all breeds of dogs including mixed breeds. All dogs carry the complete sequence of color genes, including those that create colors that do not “appear” visible in the Havanese. The visible characteristics that we see in a dog (phenotype) are under the influence of genes, present within the 78 chromosomes of dogs. Each parent contributes 1/2 of the 76 somatic and 2 sex chromosomes.

Genes are always present in pairs, one from the father, and the other from the mother, so for simplicity, an example: FF= Father, MM= Mother. When the cells divide for reproduction they are halved and then recombined when sperm meets an egg, to form the new offspring which will carry the “FM” (Father + Mother) gene combination. These genes reside at the same location (locus) on a homologus chromosome pair. These two copies of the gene are called alleles. A dog with two identical alleles at a locus is called a homozygote. A dog with two alleles that are slightly different in their nucleotide sequences is called a heterozygote, or is said to be heterozygous at that locus.

Genes may have modifiers of strength which influence what is seen. An example: dark chocolate color vs. lighter red chocolate color, which is the same color gene with genetic intensity modifiers affecting how it appears to our eyes.

Genes may be either DOMINANT or RECESSIVE. By standard genetic convention dominant genes are expressed by a capital letter, while the recessive gene is reported by a small letter.

The dominant gene is ALWAYS visible, so we usually say it is expressed. The exception is when two recessives are combined together then we see them expressed. We call this double dose of the same genes either dominant or recessive as “homozygous”.

An example following our genetic rules:

Dominant + Dominant = visibility of Dominant

Dominant + recessive = visibility of Dominant

recessive + recessive = visibility of recessive

The B gene gives a dog black pigment, but is also responsible for Chocolate pigment. Both colors are due to the same pigment (eumelanin) and the chemical shape of its particles determines whether it is seen as black or Chocolate. The gene for black is designated with a capital “B” (= dominant), while the one for liver is designated with a lower case “b” (=recessive). If parents with the father=BB (Black) and mother= bb(chocolate) are mated together, all of the offspring will be uniformly “Bb”. As explained above, the dominant gene masks the expression of the recessive, so this first generation offspring will be uniformly black, all of the pups carrying the “Bb” combination. If first generation of “Bb” pups are bred back to each other, the offspring in the second generation would statistically show the following possible combinations:

Possible color combinations when parents carrying Bb are mated

            

      B        

     b        

B

   BB (25%)

  Bb (25%)

b

    bB (25%)

  bb  (25%)

BB and Bb are the “phenotypes” (what we see as black, but cannot be sure of which gene format the offspring are carrying; BB or Bb since both are black), while “bb” is what we see (Phenotype) and in this case also know the “genotype” ( chocolate is always and only of the “bb” form) so it is a ‘gene expressed’ appearance. "Statistically” such a breeding of Bb to Bb will produce 75% black pigmented offspring, and 25% chocolate. But, for a small number of matings this result could be varied as the size of the litter will determine the number of possibilities seen, so it may take many repeated matings to approach the “statistical” results as given. In the case of chocolate colored dogs you may have plus or minus modifiers that also affect intensity of the chocolate (bb) shade, from almost black (it will NEVER be black), to a washed out, faded or “sunburned” like color appearance. Sable chocolates are an excellent example of this phenomenon as they carry the Havanese sabling gene which changes many darker colors to lighter shades with age. 

This is a VERY simple genetic explanation of how chocolates are created outside of bb to bb , which will ALWAYS result in chocolate puppies.

So I ask again, why do some Havanese breeders spread malicious myths about chocolate to chocolate breedings with health problems that just do not exist? Until actual, verifiable documentation can be provided outlining these mythical "health problems" I have begun to think breeders who take this nonsense and try to make others believe it without providing proof are the types of people who are not comfortable unless they control those around them.  

References:

·  Genetics, Dog Coat ColorsSue Bowling's explanation of Little's predicted alleles and additional hypotheses of her own

·  Dog Coat Colour GeneticsJ. Chapell's well illustrated page about dog coat colors

·  Miniature Pinscher Colours A very well illustrated and up to date site

·  Coat Color in Chihuahuas A very well illustrated page of the wide range of color in Chihuahuas

·  Coat Color in Belgian Sheepdogs A pdf download document on Tervuren, Groenendael, Malinois, Laekenois coat color genetics

·  Coat Color in English Mastiffs Includes excellent explanation of pigmentation

·  French Bulldog Coat Colour Genetics A well illustrated and up to date site about Frenchies by Dr. Karen Hedberg

·  Coat Color Genetics in Whippets Includes fantastic set of photos for many phenotypes

·  Color Genes in the Poodle A 1997 article by the late John Armstrong who was a geneticist and poodle breeder in Canada, now slightly out of date but with interesting comments regarding greying, etc. in poodles

·  Inheritance of Coat Color in Brittany Spaniels Discussion of both the American and French coat colors

·  Labrador Retriever Coat Colors Diagrams of breeding results of various matings

·  Great Dane Coat Color Genetics JP Yousha's page of loci and alleles in dogs

·  Australian Shepherd Colors Photographs and postulated genotypes of Australian Shepherds, especially Merle patterns

·  German Shepherd DogColors Alleles in the German Shepherd Dog accompanied by excellent photographs

·  English Cocker Spaniel Coat Colors A gallery of photographs of the range of coat colors and patterns in English Cockers

·  Understanding Cocker Colours, Patterns & Markings An informative article about the range of coat colors and patterns in American Cocker Spaniels which includes photographs

·  Coat Color in Pomeranians A very well illustrated page of the wide range of color in Pomeranians. Note you must click on the colored Poms to see the actual photos.

·  Genetics of Coat Color in Chow Chows An up to date site of Chow Chow colors, matings and genetics

·  The Border Collie Museum Permanent Collection A collection of photographs of Border Collies of many different colors and patterns

·  Finnish Lapphund Coat Colors Page with good accompanying photos of a wide variety of colors

·  Information about White DobermansAn explanation about the inheritance and health of White Doberman Pinschers

·  DogMap International Project International Collaboration to map genes in the dog

·  Dog Radiation Hybrid Project International Collaboration to map genes in the dog using chromosome mapping, somatic cell hybrid mapping and linkage mapping

·  Dog Genome Project American Collaboration to map genes in the dog

·  Inherited Diseases in Dogs University of Cambridge site about genetic diseases in the dog

·  Dog Genetics References An excellent listing of linked articles related to dog genetics

Links to DNA Testing Services

·  Healthgene Laboratory (Canada) DNA Testing for Coat Color & Diseases in Dogs

 


 
 
 
 

 

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