Merle Colour Patterning In The Staffordshire Bull Terrier

MERLE COLOUR PATTERNING IN THE STAFFORDSHIRE BULL TERRIER

At the request of the Staffordshire Bull Terrier Breed Council, the English Kennel Club agreed that it would no longer accept the registration of Merle coloured Staffordshire Bull Terrier Puppies with effect from 5th January 2010.

Coat colour in the Staffordshire Bull Terrier is complex because a range of colours is acceptable. Merle patterning, patches of lighter colour appearing in the coat, is the result of the M gene in the dog. There are two alleles of this gene: MM (merle) and M+ (Non-Merle). With merle (MM) being dominant to non-merle (M+). In some breeds the effect of the merle allele (MM) is termed ‘dapple’.

Unfortunately, the effects of the merle allele are not confined to coat patterning and we know that there can be an increased risk of impaired hearing and sight associated with it, particularly in dogs that are homozygous (dogs that carry two copies of the MM allele).

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MERLE PATTERNING IN GENERAL

Firstly, let me say that the merle pattern is a complex subject which leads us into the sometimes confusing area of canine genetics, and there is no really easy way to describe its effects. It is also a colour pattern that is alien to the Staffordshire Bull Terrier - ie the merles that do exist in the breed have come about through cross breeding with another breed known to possess the merle allele.

Because of the relative rarity of merles in Staffordshire Bull Terriers, most of the research into the MM allele has been carried out on other breeds where the incidence is far greater & the results easier to study.

Merle is actually a heterozygote of an incompletely dominant gene. If two such dogs are mated, on the average one quarter of the puppies will be "double merles", which is the common term for dogs homozygous for merle, and a high percentage of these double merle puppies could have eye defects and/or be deaf. Knowledgeable breeders who want to produce merle puppies mate a merle with a non-merle dog; roughly half the puppies will be merles without the risk of vision or hearing defects associated with double merle dogs.

The merle gene is often associated with congenital deafness, with merle dogs being more likely than other dogs to be born deaf. Dogs with two copies of the merle gene (homozygous merle) have an even higher chance of being born deaf. The suppression of pigment cells (melanocytes) in the iris and in the stria vascularis of the cochlea (inner ear) leads to blue eyes and deafness. An auditory-pigmentation disorder in humans, Waardenberg syndrome, reflects some of the problems associated with heterozygous and homozygous merle dogs and genetic research in dogs has been undertaken with the goal of better understanding the genetic basis of this human condition.

Ocular Defects
Dogs who are homozygous for the merle pattern gene often have visual and auditory deficits. These dogs are sometimes referred to as 'double merle' and sometimes incorrectly referred to as 'lethal white'. Ocular defects include micropthalmia, conditions causing increased ocular pressure, and colobomas, among others. Double merle dogs may be deaf or blind or both, and can carry ocular defects in blue or colored eyes. Currently no studies have been done to prove whether or not the merle gene affects the eyes, causing blindness.

Auditory Defects
One study done by a German researcher showed that out of 38 dachshunds, they found partial hearing loss in 54.6% of double merles, and 36.8% of single merles. 1 out of the 11 (9.1%) double merles was fully deaf while none of the single merles were. Another study done by Texas A&M University found that out of 22 double merles, 8 were completely deaf and two were deaf in one ear. Out of 48 single merles, only one was deaf in one ear, none were completely deaf. Another study done with 70 dogs, 15 of them were Catahoula Curs and 4 of them were deaf, whereas the other 86% of double merles in other breeds were deaf.

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Some ‘double merles’ (ie dogs who possess two copies of the MM allele) are born deaf and blind, sometimes without recognisable eyes. Others can appear normal or so severely disabled as to not survive gestation.

Here are some sites which illustrate the problems of merle patterning…
http://www.astraean.com/borderwars/2011/06/whos-your-double-merle-daddy.html
http://www.astraean.com/borderwars/2011/03/lethal-semi-dominant-merle.html

Examples of merle colour patterning & some disastrous eye problems (warning, quite graphic)

oh, those poor dogs:(

Exactly.

Awful and really, really sad. Poor dogs!
I can only wonder what people are thinking, when they breed dogs like that... or maybe they don't think?

Walpuri wrote:... or maybe they don't think?

There you have it.

It sickens and saddens me too see what people will do too get different looks and varieties in a breed no matter what it does too the dog, some of our old British breeds look nothing like they use too instead have deformities and ill health poor poor dogs i just hope the fad for merle staffords does not catch on please put their health first.
Thank you for a very informative post caryll x

When they breed merle to merle it's all about money. They think they can make more money on an interesting color. It's always the dogs that suffer!

same with blues

Yes, but the health implications with merle far outwegh the health implications with blues. I'd rather breed two blues together & risk alopecia than breed two merles together & get a dog with no eyes.

i wouldn't breed two merles or two blues together..

Neither would I, but just saying that breeding two merles is much, much worse than two blues.

i undertsand what you mean Caryll... the lesser of two evils, so to speak

But the difference is blues are a recgonised KC colour and were part of the breed of staffords merles aren,t too get a merle staffy you at some point have too cross them with a breed that has the merle gene i know that the blue strain can have some health risks but so did whites in the begining in staffs boxers and EBT, i hate that a breed has too be messed about with just for fianical gain its all wrong

breeding to blue together can increase health risk also....

https://staffy-bull-terrier.niceboard.com/t17716-colour-dilution-alopecia

a good breeder will never breed 2 together always go back to black or blackbrindle

I,m not saying i ever would i know about breeding risks but i don,t think blues and merles can be put in the same catergory merles are not pure staffords and hopefully never will be for me that have owned and my family have breed staffords for over 60yrs i am quite saddened about whats happening too our breed, but we all thank you for this site Steve it has been so lovely for me too come on here and so so many gorgeous and real staffords and people that love and know the breed.

i would put merle, blue, fawn and white in the same catecory... any breeder who mate 2 merle, 2 blue and so are bad breeders and people should stay well clear of them.

Um i am sorry Steve but i totaly do not agree with you there and i am surprised you say that, blues fawn and white are all KC registered colours so they are pure staffords merles aren,t, no where in the background was the merle gene found, i agree not too breed two of those colours together but merles are cross breed somewhere.

have you seen dog with CDA? or dog who blind and deaf? how can you not put them in the same category?

Romeo wrote:i undertsand what you mean Caryll... the lesser of two evils, so to speak

Yes, that's what I mean.

crystel wrote:But the difference is blues are a recgonised KC colour and were part of the breed of staffords merles aren,t too get a merle staffy you at some point have too cross them with a breed that has the merle gene i know that the blue strain can have some health risks but so did whites in the begining in staffs boxers and EBT, i hate that a breed has too be messed about with just for fianical gain its all wrong

That's the point, really. Nobody should be mating any merles at all, because the colour pattern shouldn't be found in the staff. Also, the health problems are far, far worse than with breeding two blues.

Steve: I know what you mean, both would be very bad breeding. All I'm saying is that one is far worse than the other. At least if you breed two blues you are just as likely to get a healthy dog as an unhealthy dog. You breed two merles and you could end up with eyes that rot away because they can't be used, or blind & deaf dogs.

i think they all bad.. breeding 2 white you could end up with blind & deaf dogs breeding 2 blue/fawn together you can get a dog that scratch it self till he/she bleed and lose most of its hair.

Steve wrote: have you seen dog with CDA? or dog who blind and deaf? how can you not put them in the same category?

yes i have dealt with colour diluation alopecia and many health problems through ill breedng steve and as i clearly said i agree with not breeding two blues together but blues are not merles is what i am saying blues are registered staffords merles aren,t.

i'm not talking about who kc or not i'm talking about bad breeding.

Just because a dog is KC reg doesnt mean it is in good health and a good dog to be bred from to other KC dog.

I wasn,t say that at all the original post was about merles and how it is bad breeding as its had too be crossed an messed about with too get that colour gene, steve said he puts blues whites and fawns in the same category as merles when it comes too bad breeding and although i agree you shouldn,t breed two of the same colours as anyone who knows the best blues comes from a cross with anothe colour, but i do not agree that blues fawns etc are in the same category as merles. I DO NOT come on here for confrontation but i have as much knowledge as anyone else on here so if i disagree i will say we are all entitled too our own views i guess.

OK, it really doesn't matter where we draw the lines of importance here. The fact is that we all know that certain things are wrong & shouldn't be done - that's all that matters, really!

Caryll wrote:OK, it really doesn't matter where we draw the lines of importance here. The fact is that we all know that certain things are wrong & shouldn't be done - that's all that matters, really!

too true caryll

Yes i understand what you mean but the point i think he was making is that two whites and two fawns bred together will be as disastrous as two blues together. None of these are as bad as merles, but are still not condoned.

Sorry, but im not totally up on Breed colour Standards, but there was no blue in the very 1st staffords, so where did it come from. Has the Kc added blue to the standard at some point. Im not trying to stir things up, but it's an intresting question. Where did the blue colour staffy come from?

Sorry, but im not totally up on Breed colour Standards, but there was no blue in the very 1st staffords, so where did it come from. Has the Kc added blue to the standard at some point. Im not trying to stir things up, but it's an intresting question. Where did the blue colour staffy come from?

blue come from black staffy blue brindle come from black brindle, fawns come from red staffy any animal that come in black or red can make blue or fawn colouring

Yes too what steve said they say Blues were a colour diluation too blacks and fawns too red like anything you have standard colours and then suddenly a litter will produce an unusal colour blues were not part of the original colour listing but back then they didn,t believe you could have a black staff either blues are so popular now, but they were really rare 10yrs ago blue was added too the kc list at least 15yrs ago could have been longer

kenny d wrote:Sorry, but im not totally up on Breed colour Standards, but there was no blue in the very 1st staffords, so where did it come from. Has the Kc added blue to the standard at some point. Im not trying to stir things up, but it's an intresting question. Where did the blue colour staffy come from?

Blue is a dilute of black & would have occured naturally on occasion. It was added to the standard, I believe, to clarify the fact that it is a naturally occuring colour in the breed.

ok, thanks.

That is just too horrid for word!!! Those poor poor dogs.