[kanisha]

Yes I much prefer a more balanced approach and tail vertebrae is a more interesting and relative means of measurement. ouessant breeders have never placed any importance on the fluke tail and its significance to shetland owners as a sign of cross breeding is a breed specific issue., outcross a ouessant to anything else and the biggest indicator of cross breeding will be size. Hence a ouessant breeder doesn't go anywhere without his measure or his knee. ( they should all be below the knee level.) the texts are in french but the study from nantes is lengthy ( there are multiple parts just change the number in the end of the url. ) very in depth and very interesting still puts the ouessant as the oldest breed in france and untouched by modern intervention. due in  a large part to its geographic location; interesting to note that one of the main indicators used in the nantes study for breed age is size  the population of the breton noir is also listed and height  measured in many zoo technical manuels from the 17th century onwards again because of the rusticity of the sheep in this region. There are more than enough indicators to confirm the origins of the ouessant in the region and its authenticity as a Nst its just that sometimes people aren't used to seeing variation as anything other than a sign of cross breeding.  what if I was to give you another  considered by some *outrageous* explanation for dominant black in hebredians.............

[Fleecewife]

<<what if I was to give you another  considered by some *outrageous* explanation for dominant black in hebredians.............>>

Oh go on then 

[kanisha]

Hang on to your hat! I will assume you have a good understanding of basic colour genetics.

standard explanation for dominant black is that it switches ( in laymans tems) the dominance from the agouti locus to the brown locus.  It is a single switch ie its either dominant black ( whatever is at the brown locus dominates)  or its standard agouti dominance.

the only fly in the ointment to this has been those breeds that behave as whites but have black markings like the scottish blackface.  Genetically this has not been possible to explain if agouti is full on to white, expression of eumelanin isn't possible. All the studies to explain  sheep colour have been based on this assumption.  Including the very tidy agouti heirarchy as seen and ably demonstrated in the shetland. with the more recent (2008) understanding of the mechanism in white sheep thanks to the genome project it was able to show that there was a duplication in the agouti signaing protein sequence that does allow the *possibility* for expression of eumelanin in a white sheep Instead of one agouti signaling protein there are two sat next to each other.

Instead of a switch you now have possibility for a  mechanism for co-dominance between agouti and extension. This can appear in a variety of forms depending on the expression of that co-dominance, each family or breed of sheep showing these genetics has its own pattern and the patterns are progressive if you select always for the most patterned ( darkest)  individuals I call them spreading patterns)  so the scottish black face is a much reduced  black pattern on a white sheep . I made the proposal  that  agouti grey was not an agouti pattern but this type of co-dominance between agouti and extension only much futher towards the greater  expression of extension. In some case this shift towards extension can go further and become extension dominant and the odd ED sheep arrives in an otherwise "normal" flock. I made this proposal after struggling for a long period to understand the development of pattern in ouessants a breed which traditionally only comes in white and black and the experiments I have done to study this development.

This would be exactly the same mechanism as is seen in suffolks. Now instead of the shetland having exclusivity, its genetic mechanism is shared with many UK breeds of sheep  ( This proposal has caused outrage!)  However just say this was the case and that in the genetic soup before breeds were fully characterized within the scottish populations of sheep there was a mechanism for producing dominant black that may explain those hebredians that were selected as black ( we all know you can't tell by looking which are recessive and which are dominant black)Then the notion of assuming ED was as a result of crossing to a jacob or a black welsh mountain isn't necessarily the only answer. I leave it to you to work out if the breeds history allows this development but  the mechanism is there.   

[Fleecewife]

Hi Kanisha.  Very interesting !  Yes, I think the breeds history would allow for the possibility of this mechanism.  It is only 130 years or so since Hebs were part of the greater multicoloured Scottish tanface landrace type. Would you not though also expect to see th same mechanism in, say, black Soay, North Ronaldsays, etc?  In fact is someone in N America not studying that very question with Soays?
As genetics, whilst being extremely interesting, is not my main hobby, I find it difficult to keep up with the latest studies and knowledge, so thank you for bringing that one to my attention. 
Now, can you explain White Hebrideans please?  I understand that it is beleived that they can be genuine (ie there is a mechanism to explain how they can pop up every now and then) although the HSS still does not allow registration.  Whites were registerable under the RBST but not since the HSS took over.  We have a white Heb ewe we bought several years ago but have always assumed that she was a cross.........You can see her on our website www.scothebs.co.uk

[kanisha]

Hi Fleecewife. Black soay are recessive blacks this is as  result of a non functional promoter to the agouti signaling protein studies have shown this to be the case in black soays on hirta. The study came out not that long after the study into white sheep so was very relevant.  studies in NA soays depend on which ones they are studying they  may or may not be relevant some are acknowledged to have been crossed out to US breeds.
The north ronaldsay is a good question. Has anyone given you an explanation for their colouration or the mode of inheritance? everytime I ask I get blank looks. However as a breed they are very relevant.

OK firstly the explanation I have given is far from being accepted by the genetics community but its working for me and that is important because it is quite a complex inheritance;and I am looking for the theory to fail in order for me to have to rethink things.
to take first the scottish blackface a breed which in terms of pattern and colour is very stable there is very little variation within the breed until you cross them out. I would not expect a dominant black to pop up in this  breed without being a mutation they are to far towards a white sheep to get a huge shift to ED.

the north ronaldsay are more variable but quite a stable population in that they are all closely related, would anyone one know/ notice if one went as far as ED? is anyone breeding them looking for definative colour patterns or characteristcs? I was told of one breeder who claimed to have a recognisable mouflon ( black and tan or soay) pattern crop up only to be told by the breed society it was a cross. I asked to have contact details for the breeder and was blanked....  yet the breed society couldn't tell me the colour inheritance of the breed; ( the mouflon pattern is relevant but lengthy to explain)

as for whites hebredians; Blondie is for me fascinating although white she shows marked colouration and that for me is what I spend a lot of time looking at all those funny little patterns in white sheep. she could only show up as a true white hebredian if there was dominant black and somewhere along the line  a genuine white hebredian line was continued but if you say that up until recently they were accepted then its entirely possible ( as much as not)  that she is genuine.  I am only able to look closely at ouessants its hard enough getting good testimony from breeders over their oddities in this breed let alone other breeds and it takes people who are comfortable with questioning the acceptance of breed characterisitics in such black and white terms but  my theory would offer an  explanation for both genuine dominant black hebredians and the white hebredian line. whether or not you could prove it is another matter..... do you know her parentage and history?

[Fleecewife]

<< Blondie......do you know her parentage and history? >>

Unfortunately not, as she is not registered.  We know the Hebridean flock she came from and we also bought several black Heb ewes from them at the same time - one of those a few years ago produced white twins but we assumed fence hopping was to blame as at that time we had a white Shetland tup.  There were apparently four flocks which regularly produced white Hebs but in the face of opposition from the HSS they gave up trying to get them recognised.  This was before we joined the HSS ourselves so all I know is by hearsay.  I think that the flock we bought Blondie from was one of the four, so the chance of her being genuine is fairly high.  As well as the dark nose, she also has one or two tan markings which she passes on to her crossbred lambs.  If bred to a black Heb, she produces black lambs indistinguishable from pure Hebs, so we always cross her. Obviously if we had time and space we would do some experiments, but we don't.

I don't know enough about Ronnies to be able to help there.  I know a couple of people who breed them, and I know that their fleeces are wonderfully soft to spin, but beyond the general history of the breed I have no insight.

As you will have seen on our website, we breed Soays for black - the piebalds popped up from two blacks but are a new venture. As well as black we also get moorit lambs, which you would expect. 

I think Lawrence Alderson feels now that white Hebs can be explained without the presence of dominant black, but I need to make further enquiries.

[kanisha]

Hi, does she always produce black lambs when bred to the hebredians?

[Fleecewife]

When we first bought her as a three year old she was already in lamb to a pure Heb and had a single perfect black lamb.  The previous owners had previously bred her to a pure tup and had had black lambs they said.  After her first lambing we always crossed her to a white shetland and she would have a single enormous white lamb. This year we are not breeding her.

[kanisha]

Hi Fleecewife , interesting but not possible to draw any conclusions from.

 Re other way to get white from black.
the other mechanism is white spotting which is a recessive and at times it can be hard to tell a white sheep from a black sheep with white spotting except when you have tan markings and then you are dealing with a white sheep as tan cannot be expressed in the prescence of white spotting - which is a total failure of the colour cells to produce colour; Blondie is a genuine white sheep whether she is genuine hebredian is a different question.

[Fleecewife]

Ah so the tan markings are significant.  Blondie remains a mystery, but I will see if I can find out more through Lawrence Alderson, as he is the one who has said that it is explainable.  This question is significant to the Hebridean breed, because of the change of policy from registering whites under the RBST, to not registering them under the HSS.  At the same time, registrations of polled and topknotted animals was also not allowed, but now they are, as the current HSS committee recognises the need to preserve the ancient characteristics of the breed before they are lost forever.

[kanisha]

Yes and to get back to my original point there has been a kind of breed snobbery with regard to variation instead of conserving and understanding the variation some breeds view any deviation from the ideal as an indication of cross breeding. hence the issues with tails. and of course more relevant to this thread the mistaken  idea that concentrating exclusively on one single genotype as providing protection from scrapie. nature favours variation for breed strength and yet you still meet people who will only accept ARR/ARR

One point to make re blondies black lambs if she was heterozygous for white ( which one would have thought more than likely)  she should have by the law of averages produced as many white as black lambs for her former owners when put to hebs unless of course his flock had dominant black present which could also hide white...........but that doesn't mean you'd get the same results with your flock.

[Fleecewife]

Blondie's dam was a normal black Heb - but then so allegedly was her sire. But depending on the reason for her being white, she could I suppose be homozygous recessive, if this proposed mechanism allows that. I am  a bit pushed for time at the moment but I will try to find out more.

With Hebs, we have a breed desciption, not a standard, so it allows for variation within that description - it's something we defend to the hilt and it has allowed us to save the rarer traits at the last minute.

[kanisha]

I can see where Lawrence alderson could try to explain white hebs using white spotting and yes this would result in a homozygous recessive piebald lamb. ( I'm not saying I agree but as a mechanism its theoretically possible. )

however Blondie isn't as a result of white spotting her colouration excludes that.  I would have thought the easiest way would be to get blondie DNA tested. it can be done to determine parentage quite easily these days.she would then be either as a result of dominant black hiding a white or a cross fence liaison. Testing wouldn't prove or disprove Aldersons ideas but leaves two possible explanations for whites in hebs and of course will settle blondie. The complication in Aldersons theory is that there is dominant black in Hebs but as white spotting isn't hidden by dominant black you should get the two cropping up independantly of each other.