MOTIVATION FOR THE MANTLE TO BE INCLUDED IN THE GREAT DANE STANDARD (RSA)

SHANNON McKAY – SAXONY GREAT DANES (Johannesburg, South Africa)

March 2003

Based on my personal experience, literature and research covering published findings of various specialists in the field of colour genetics, I have the following information on mantle colouration in the Great Dane. I have opted to use everyday language as opposed to the technical terminology as far as possible.

DEFINITIONS

The series of genes that affect the distribution of white on a dog is defined by Clarence C. Little in The Inheritance of Coat Color in Dogs as the S series. Little proposed that there are at least four alleles. Some 32 years later Dr. Malcolm B. Willis in his book, Genetics of the Dog (1989) lists the same four alleles, but with slightly different definitions. The original definitions were:

S – self, or completely pigmented body surface;

sⁱ – Irish spotting, with few and definitely located white areas;

s^p – piebald spotting;

s^w – extreme-white piebald.

All four have been observed in blacks from harlequin breeding.

My personal interpretations are:

S – Black with little or no white i.e. show marked black

INHERITANCE

Every single gene needs two alleles (one from each parent) so a self coloured dog bred from generations of self coloured dogs will more than likely be SS and will only produce SS if put to an SS partner. As this dog’s expression of colour is a true reflection of its genetic make-up for colour, this dog will breed true and is termed homozygous for that particular trait. A dog that has two different alleles is termed heterozygous. These dogs will not “bred true” in that the recessive gene may come to the fore depending on the mate.

Example:

Ssⁱ – A black dog with white toes

Ssⁱ – A black bitch with white toes and white on the chest

25% of offspring will be homozygous black (SS) and will produce only black

50% of offspring will be heterozygous black (Ssⁱ) with possible small white markings, and can produce mantle

25% of offspring will be homozygous mantle (sⁱsⁱ), which will produce mantle

As can be seen the heterozygous dogs have not “bred true”.

If one is using blacks from harlequin breeding, the odds are, in my opinion, high that they are heterozygous Ssⁱ as the mantle pattern of clear front and neck is an integral part of harlequin breeding. In other words, as a result of the preferred patch distribution in harlequins, most harlequins are sⁱsⁱ.

In breeding for the preferred harlequin patch distribution, the harlequin breeder will produce mantles. By excluding these dogs from their breeding programme they limit their gene pool and the complicated task of breeding harlequins with the preferred patch distribution moves even closer to an impossibility.

INCOMPLETE DOMINANCE

As stated by Dr. Malcolm B. Willis in his book, Genetics of the Dog (1989), the S series of alleles is also regarded as being an incomplete dominant. What this means is that when there is a difference between the two alleles an intermediate type may be expressed. This has been demonstrated in flowers. Progeny from one red and one white flower can be pink as opposed to the dominant red one would expect.

Example:

Ss^p – The dogs appears to be a mantle, but is in fact an heterozygous intermediate hybrid i.e. a combination of a solid black and a piebald, which produces a “fake mantle”.

When put to a mate with the same heterozygous intermediate hybrid coupling:

25% of offspring will be homozygous black (SS) and will produce only black

50% of offspring will be heterozygous mantle hybrids (Ss^p), and can produce piebald

25% of offspring will be homozygous piebald, which will produce piebald (s^ps^p)

As can be seen, if mantle breeders are aware of the incomplete dominance factor, they will be able to determine the dog’s genetic colour distribution pattern, which will assist tremendously in their breeding programme.

MODIFIERS

The S series also possesses modifiers, which restrict (minus modifiers) or increase (plus modifiers) the base colour. So a sⁱsⁱ dog with plus modifiers may appear to be a SS with minus modifiers. This is termed a pseudo Irish. When S and sⁱ exist in a breed (such as in the Great Dane) identification problem may occur. However, research into the dog’s pedigree should provide a better understanding of the dog’s genetic colour and assist breeders in correctly identifying their dog’s S series.

WILL MANTLES BREED TRUE?

Unequivocally yes, in that they will always produce a combination of a base colour (black) with specific areas of white. They cannot produce harlequin or merles unless put to a harlequin or merle. By using only mantles that fall within a pre-described standard, the incidence of under marked dogs is greatly reduced.

CONCLUSION

While there is the possibility that under marked dogs (dogs classified as s^w i.e. white with very little black marking) can be produced from mantle breeding, the risk is far less than it is in harlequin breeding. It is important to note that these under marked dogs from mantle breeding should not carry the same high risks as under marked dogs from harlequin breeding i.e. deaf, blind etc. as the merle gene is not present.

Furthermore, breeders striving to produce the correct mantle pattern will automatically steer clear of the piebald and extreme piebald, thus making the production of white and extreme piebald virtually impossible.

The mantle standard should, in my opinion, call for symmetrical markings, which are said to be most apparent in sⁱsⁱ  i.e. homozygous dogs who appear mantle and will breed true by only producing mantles (with the influence of modifiers affecting the amount of white).

Therefore accepting the mantle as a recognised colour – and therefore having a standard to work towards – will reduce the incidence of under marked dogs since breeders will be working toward breeding homozygous dogs that will only produce mantle.

Furthermore, the use of homozygous mantles in harlequin breeding programmes will greatly reduce the number of s^w harlequins (harlequin headed), who are susceptible to a variety of problems. The use of mantles (whether true or hybrid) to harlequins will also guarantee no double merle offspring.

Harlequin breeders who are willing to limit themselves by only breeding harlequins to mantles can then gradually establish homozygous sⁱ in their breeding stock and thus gradually reduce the incidences of under marked dogs, who are susceptible to a variety of problems. The use of mantles (whether true or hybrid) to harlequins will also guarantee no double merle offspring. Furthermore, the homozygous mantle will breed true and will not produce white when put to a harlequin.

Harlequin breeders should be using mantles to gain the correct patch distribution. Without the mantle these breeders have no choice but to use harlequin to harlequin, which can and does result in double merle offspring. Thus by accepting the mantle, harlequin breeders will not be pushed into this corner and harlequin breeding would no longer entail the routine culling of double merle puppies.

As can be seen, the use of homozygous mantles will greatly reduce the number of under marked and white dogs. However breeders require a standard to work to and an incentive to produce correctly marked mantles, which will in my opinion benefit the breed on the whole.

Without formal recognition of the mantle, this exceptional opportunity to improve the Great Dane as a breed and the individual welfare of under marked dogs is lost.

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