Hämtat från https://northwestsbtclub.co.uk/health-bullitins/
Health Bulletin No 24, March 2015.
Discussion about blues and the numbers being registered is seldom off the various social internet sites. Like everyone else, I deprecate the actions of those who breed blue Staffords (or French Bulldogs etc.) purely for money without due regard for the quality of their dogs, whether in relation to the Standard or to their health. The topic has become so emotive that clear thinking has become very cloudy in many instances. As one who simply wants the scientific truth in this matter (and all other such topics) I have sought the comments of the academic experts, as well as trying to get reliable information on any associated problems.
I will assume that readers will understand the workings of the ‘D’ (dilution) gene and its recessive ‘d’, of which there are at least two alleles or variants, one of which is more common in dogs in general and is the only one to be found in some breeds; it is not known if both are present in Staffords or not. It is ‘d’ when homozygous, i.e. a dog carries two copies, one from each of its parents, that produces ‘blue’ by causing the eumelanin (black) pigment in hairs to clump rather than be evenly distributed throughout.
Firstly a question – ‘Is there any difference, in respect to ‘d’(assuming it is the more common allele involved), between a blue dog produced by two brindles that carry it or one which is the result of blue to blue matings over several generations?’ The answer is simply ‘No’! If you tested each dog, either by DNA sequencing or by the DNA tests for ‘d’ offered by some companies, you would get exactly the same result, which in turn means that the expression of ‘d’ in both would also be the same. In the course of correspondence regarding blue to blue matings, Prof Schmutz of Saskatchewan University, who is regarded as the queen of colour genetics, simply stated that you can’t get “more homozygous” by the process and did not see why it would matter, thus supporting what has been pointed out above. Prof Tosso Leeb of Bern University, whom I also consulted, responded in a similar vein seeing ‘no rational reason for a ban on blue x blue matings’
Some confusion may have arisen by using the term ‘dilution’ for the gene which in scientific literature is now referred to as the MLPH gene in accordance with its function at the molecular level. It was the American geneticist, Clarence Little, the father of coat colour genetics, who coined ‘D for dilution’ in the 1940s on account of its recessive ‘d’ ‘diluting’ black to blue (actually a slate grey) as he put it and nothing more. Some however may have the impression that when you mate two blues or dilutes together you are then ‘diluting’ further and further with each generation, which is simply untrue. Once the initial ‘dilution’ has occurred to produce the blue dog which is homozygous ‘d/d’, then that is the dilution process complete!
There are of course anecdotal reports of blue to blue matings producing coat and other problems, plus comments that many blues are different from other colours in build and appearance. Should this be considered so, it is almost certainly a question of ‘bad’ breeding rather than ‘blue’ breeding. If you breed for one particular aspect, in this case a colour, without regard for the whole dog (or other animal) then you are asking for trouble. This is something that has been seen in other species, for example in cattle where breeding for milk production solely has had serious adverse effects on cows’ health.
The big problem is a virtual total lack of data, i.e. peer-reviewed papers in scientific journals, and there would need to be several to ensure that any finding was corroborated. I am aware of some papers of a histological or molecular nature but none on the incidence of coat colour-related conditions in dogs in general or in specific breeds. (If anyone comes across any, please let me know.) Hearsay and anecdote have been the basis for so many opinions when firm data is essential. In fact a vet I was talking to very recently at a seminar highlighted this lack of facts and figures.
In Staffords we must be very aware that perceived coat problems may not be confined to blues. I know we are again forced to rely on anecdotal opinion, but if one goes back thirty years or so you may have heard of certain stud dogs being associated with progeny with poor coats and I do recall seeing brindle dogs, supposedly from a certain popular line, with ‘spectacles’ of hair loss round their eyes. Some may recall I asked vets from a large canine charity (Health Bulletin 14), plus others along the way, for their thoughts and clearly the body of opinion was that blues were no more affected with skin and coat conditions than other colours, in fact some vets consider that whites may be at greater risk.
Currently the greatest hope of getting meaningful data is the VetCompass project which receives information, including coat colour as well as the usual parameters, from many veterinary practices on all ‘patients’ being seen. I have spoken to Dr Dan O’Neill the veterinary epidemiologist in charge about our concerns. At the moment no data has been extracted in relation to coat colour but, having asked the right questions, it is on the ‘to do’ list. However, even if health conditions were found to be more prevalent in blues (or any other colour), thus showing a correlation, that would not be the end of the matter. Correlation does not equal causation! Further studies would be necessary see if the colour genes were actually involved and to rule out co-incidental findings such as inadvertently selecting genes for other conditions.
To appreciate why great care is needed with ‘correlation’ we only have to look at the hereditary cataract cases that emerged in the late ‘nineties’. There was a correlation with the red breeding, with a few saying to keep away from the ‘reds’, but no one with the least understanding ever claimed it had anything to do with their coat colour or the genes that produced it. It was just chance that it came to the fore in reds.
The one condition that is associated with blue dogs is colour dilution alopecia (CDA) where the blue hairs become fragile and break off. It can vary in severity and may lead to extensive bald areas where the skin may be affected by dryness and infection requiring long term topical treatment. White areas, if present, are not affected and in blue fawns CDA is likely to be much milder simply because of there being much more phaeomelanin (red) than eumelanin (black) in their hairs. However many blues (of many breeds where the genes are the same, as well as Staffords) have good, even excellent, coats with no problems so one cannot say that, although only blue hair is affected, the d/d genotype is specifically the cause. Expert opinion now considers that some other, as yet undescribed, genetic factors are involved; these will also be carried by non-blues but have no effect because of the different coat colours. There have been attempts to understand CDA but sadly very little progress has been made and there would seem to be no current research. Prof Leeb does have a call online for case reports plus specimens; I have no idea what the response has been but one suspects it has not been overwhelming. This may simply reflect a low incidence of CDA but perhaps VetCompass will shed light in due course. In addition, only one of the vets surveyed from the large canine charity referred to above reported seeing a case of CDA. Furthermore if a blue dog does have hair loss, all other possible diagnoses, such as demodex, allergy, etc., must be eliminated before considering CDA and if there is reasonable recovery, CDA can almost certainly be excluded. In the course of discussions, it was suggested that if breeders of blues were concerned about the possibility of CDA or similar coat and skin problems, then they ought to ensure they used only dogs with visibly good coats. This of course is common sense and constitutes ‘good’ breeding.
Of course the absolute way to eliminate all risk of CDA would be to discourage or prohibit breeding for blues as the colour is essential for the expression of those genes that may be the real cause. As far as we in UK are concerned, this would mean changing the Standard by deeming blue to be ‘highly undesirable’ along with liver and black and tan.. In fact some years ago I wrote an article to this effect pointing out the anomaly of permitting blue but not liver or black and tan, bearing in mind that black and tan is a perfectly normal coat colour and liver is produced by black eumelanin being replaced with the brown variety, without any hair abnormality, which the eumelanin clumping in blues undoubtedly is.
As many know, there was no mention of ‘blue’ in the original 1935 Standard, being only added in the 1948 review. There is no documented evidence of why this was done to my knowledge. It may be that blues pre-1948, were included with brindles and fawns but added after the genetics had been described by Little as mentioned above. Thus if a change in the Standard to discouraging blues, because of perceived health issues, were to be proposed, the inevitable question is why has it taken well over sixty years to be raised? And more importantly, where is the evidence, in the form of peer reviewed papers, which will withstand scientific scrutiny?
Even if the KC were persuaded to implement such a change, the greater threat of legal action is a possibility. A commercial breeder, all above board and licensed with the local council, might sue the KC (or other KC’s or similar bodies that have implanted colour breeding restrictions for registration) as their business might be adversely affected. Unless I am greatly mistaken (the legal experts will correct me I’m sure) the KC would back down rapidly as they would know that it was a lost cause.