I'm going to weigh in with my hap'penny worth here.
In the UK, Bearded Collie breeders are fighting tooth and nail to prevent the KC from permitting merle beardies to be registered, as this colour doesn't exist in show lines. You might be interested in reading the statements around the edge of this. The late Dr Malcom Willis was a hugely respected breeder and geneticist. His and the other statements do indicate issues with heterozygous as well as homozygous merles:
http://www.beardedcollieclub.co.uk/Merle_Press_Advert.pdf
I have never heard of any heterozygous sheltie merles which have issues proven to be attributed to their colour. Nor have any of the merles I have known been any less healthy or shorter lived than other colours. Their eyesight and hearing seems to be perfectly normal and I've not heard of any higher incidences of CEA in blue merles (although the visual eye exam isn't always accurate in the blue eyed ones due to the pigmentation). It could be that illnesses/diseases that have occured in merle dogs have been put down to colour when in reality, this may be purely incidental.
I may have misinterpreted it, but I read the statement in the opening post as a breeder trying to dissuade people from doing this mating. Not "it's fine if you can cope with disabled dogs" but "are you
really prepared for the consequences of what might happen if you do this?"
I do think there is a difference, although a subtle one, between those who carry out this mating to produce an outstanding coloured blue and who are aware and dreading what the result might be - and those who apparently are deliberatly trying to breed all white dogs for some sort of 'distinction' and who are BYB or puppy farmers only interested in producing a rarity.
In the past it was acceptable in livestock breeding of any kind to 'cull' any surplus. Certainly when I started out in rabbits 20 years ago, it was perfectly normal in the patterned breeds and those with a limited pet appeal, to select the better animals at birth and reduce the litter down to 2-3. The surviving offspring would do better with less competition and money, time and effort wasn't wasted rearing unwanted animals. 'Stockmen' were not sentimental towards their stock and one of my books states "you must be ruthless and cull anything which doesn't reach the required standard".
I know several breeders who openly reveal they have done merle to merle matings in the past. They say that they have either never, or only once produced any 'defective' puppies from this. It's worth mentioning that while stastistically a merle to merle mating will produce 25% 'lethal/defective' puppies (and even this has been disputed as the genetic mode of inheritance is not straightforward and not completely understood) in real terms, it would be quite possible to breed several litters of merle to merle and apparently not have a problem. I also think I recall reading in 'Sheltie Talk' (mine is a 1970's edition) a frank discussion about doing this mating and even breeding on from a white. The fact that the outcome isn't guaranteed to be bad and could well result in hitting the jackpot, is probably why breeders have and continue to do it. It's a gamble but if you strike lucky once....
However, and this is the stumbling block, in the past it was quite appropriate and acceptable to drown litters of unwanted kittens and puppies and to 'cull' defective, mismarked and surplus animals. That was the 'responsible' course of action to take when this practice first started, but times have changed.
There are two slightly seperate issues associated with the breeding of double merles. The first is bringing puppies into the world which have a potential risk of being either blind or deaf, the second is what to do should this occur. For myself, I could not as a breeder, deliberatly bring life into the world with the intention of destroying it. It goes against everything I believe unless something has gone badly wrong or the animals are being bred for food anyway. However, I
can understand those who have made the choice to breed a certain colour or breed (thinking about rabbits) where the right ethical choice is not to permit those lives to continue if they would have a very poor quality of living. When Mia's advert was first posted, I was rather horrified and I thought it wasn't ethical to keep such a disabled animal alive, as what possible quality of life could she hope to have in a dark and silent world? When Michelle and Brian brought her into their clan, I did soon change my mind as I watched the videos and I'm so delighted to see how she has blossomed.
BUT, homes and owners like this, who are prepared to take on the challenges of owning and devoting themselves to a blind and deaf dog are few and far between. I'm in awe of people who can do this as honestly, I couldn't. It is a risk in rearing severely disabled/special needs animals that a good home can eventually be found. If not - what then? Ultimately the responsibility has to lie with the breeder - and they should either be prepared to euthanise the defective puppies at birth, ensure either very good appropriate homes can be found or commit to keeping them for the whole of their life and devoting all the necesssary level of attention to their care. Definitly not something to be taken lightly and I suspect not many breeders are realistically in a position to devote themselves to caring for a special needs dog. To take the risk of bringing blind and deaf puppies into the world and then pass on the result to a rescue to deal with, is frankly beyond contempt.
The UK KC will not register progeny from a merle x merle sheltie mating now, which think is a very positive development. IMO, colour is unimportant in the scheme of things and the possibility of producing a visually outstanding blue CANNOT EVER justify deliberatly breeding merle to merle. I think the vast majority of breeders in the UK now would find it abhorrent anyway, the trouble is when 'everyone's' doing it, or someone does it and has high profile sucess it somehow becomes more acceptable. To answer the question posed earlier, I see no issue with merle shelties continuing to be bred responsibly and personally I wouldn't have an issue buying or using a dog from someone who did merle x merle matings, although I would be cautious about owning even a 'normal' homozygous merle - especially as I prefer the darker rather than washed out blues which are currently in vogue!
Sorry, this is more like fifty pounds than a ha'penny!!
