May 29, 2012

Belton patterned horses

Posted by The Equine Tapestry under Appaloosa, Mystery colors and patterns, Oddities, Pintaloosa
1 Comment 

This is “Gump.” He’s a Paint Horse that shows here in the Carolinas, and is the horse that first had me wondering about the possibility of a dark ticking pattern that was separate from any of the white patterning genes. As you can see, he has quite pronounced spotting on his face much like one might expect to see on a leopard. The problem is that were he actually a leopard as well as an overo, those spots would replace his bay areas, not his white areas. (For those just joining the conversation, the two previous posts explain this in much more detail.) I suspect those familiar with leopard patterns would also recognize that there area around his mouth doesn’t look right for the appaloosa pattern, either. It is too “clean”, with the spots and the white very clearly defined. If you cover his face so that just his muzzle shows, he looks like a pinto with “kissy spots” and not a leopard appaloosa.

So he is just a pinto. Here is a side shot to show the rest of his pattern.

As this picture shows, he’s a frame overo. That white on the side of the neck and again on the side of the body are classic placements for that particular pattern. He probably also has one of the sabino patterns, since he has high stockings in the back. Frame does not typically add white to the legs, so frame horses with white legs are usually carrying something else in addition to frame. Since the various sabino patterns are widespread in riding horses, and especially in stock horses, it’s the most likely cause.

What struck me about Gump is that his pattern has a torn, angular look, which is quite different from his extremely round ticks.

There is spotting on his leg white, too, though I did manage to position myself for the best lighting in this photo. Like the spots on his face, these are round even though the rest of his stocking goes up in ragged angles.

The character of the ticking and his pattern do not match.

That is particularly interesting to me, because most of the pinto patterns interact with one another. They don’t just overlap one pattern on top of the other. The presence of one tends to effect the appearance of the others. That overall influence gives most patterned horses a harmonious look. It also complicates matters for those of us interested in teasing apart and defining the different patterns, when the action of one mutation changes the actions of a second, unrelated mutation. Sheila Archer, of The Appaloosa Project, refers to this as patterns “talking” to one another. I have always liked that way of phrasing it, and would say that much of what I find most interesting about patterns these days revolves around those “conversations” between the patterns. The discordant patterns on Gump say that whatever is causing his ticking, it doesn’t seem to be “talking” to the rest of his patterning. That would at least suggest that it is something separate from whatever is causing his pinto pattern.

Gump sat in my “weird stuff” file for years, until last month, when a Facebook friend linked to this horse. When I first saw the image as a thumbnail, I assumed someone had found Gump. The ticking and even her base color is that similar! But that’s not Gump. That’s an Australian sport pony named Haley’s Comet.

Around the same time, another horse came to my attention. Her image was used on the header of the Paint Horse Connection, a quarterly newsletter that goes out to American Paint Horse Association members, and in an article in the Paint Horse Journal.

Like Gump, she is a frame overo, but without the sabino-type leg white. And like Gump, she has the spots that are very concentrated on her face, compared to the spots on her body. Because her body has broad areas of white patterning, it’s even more striking on her.

That was what made me think of the Belton pattern in English Setters. They sometimes have that same kind of larger, more concentrated spotting on the face compared to the body.

They aren’t all like that. One of the most interesting thing about the ticking (Belton) pattern in dogs is that it does have a lot of variation even within a single breed. But on a horse this kind of concentration on the face is quite unusual. Heavily concentrated dark ticking is odd in horses. Having it more pronounced on the face is stranger still.

You might notice that these horses all have a similar spotting arrangement, but that arrangement is rather different from Vision Morinda, the horse posted previously. Her ticking is more uniform, smaller and denser. It is hard to know, with so few horses like this, if these are variations on the same trait, or different things entirely. But having seen a handful of horses like this now, I know I’ll be looking at ticking more closely in the future. And certainly if any readers find horses with interesting spots inside markings or patterns that don’t fit what might be expected for a tobiano or one of the overos, please pass them along!

 

May 26, 2012

Leopards, Cat Tracks and Beltons (Part 2)

Posted by The Equine Tapestry under Appaloosa, For Artists, Non-equines and other tangents, Pintaloosa, Tobiano
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In the previous post, I talked about the two things that cause horses to have small dark spots on a white background. The first was the leopard pattern (Leopard Complex + Pattern1) and the second was the homozygous tobiano pattern. In this post, I want to talk about how dark spots on a white background are different in dogs.

Dalmatian dogs look like leopard appaloosas. It’s the same white background and the same small, round spots of color.  But Dalmatians are genetically very different from leopards. In fact, they have a lot more in common with the homozygous tobianos. That’s because they are “pinto” dogs. They just happen to be missing (or at least mostly missing) their dark patches. In fact, if you can imagine someone starting out with a classic tobiano horse – dark head, large round areas of color on the body – you have a good idea of what the basic piebald pattern is in dogs. In fact, in some countries the name for tobiano and the name for this pattern in dogs is the same: plating. Plattenscheck, platenbont – plate pinto. It makes sense, since tobianos have large “plates” of color on a white background. These dogs do, too. Or at least they started out that way. Here is a popular sire of English Setters from a little over a century ago.

His pattern is very reminiscent of tobiano. But breeders did not care for the patches, so they began breeding away from them.

In dogs, this kind of pattern is often called “extreme piebald”. It is still a “pinto” dog, but it doesn’t have a lot of color left, even on the face. English Setter breeders were not alone in this preference. The Dalmatian breeders were selecting for the same thing. They did not want patches, or even dark ears. They wanted all-over round spots.

Those round spots, which are visible in all three of these English Setters, look a lot like cat tracks to someone familiar with tobiano. What makes them different is that they aren’t actually part of the plating pattern. They are a separate thing entirely. For English Setters and some of the other sporting breeds, that’s the “Belton” pattern. The more technical names for it – ticking and roaning – are unfortunately for us horse people, already taken by very different patterns. So for now we’ll just use Belton to avoid making this any more confusing.

Belton adds dark spots of color to the areas the piebald pattern leaves white. What dog breeders have done is manipulate the scale and spacing of those spots of color. All three dogs at the top of this post have what are believed to be variations on this kind of patterning. The English Setter to the left is of course the original Belton pattern. The Dalmatian in the middle is likewise has a Belton-type pattern, but he also has some kind of modifier that has made the spots larger, rounder and more distinct. (Some of the distinctive nature of his spots are, of course, because he is a sleek-coated dog compared to the setter.)  The Australian Cattle Dog at the end has a Belton-type pattern that was modified to the other end of the spectrum, with spots that have gotten smaller, less round and less distinct. In some breeds, this is what is called Roan. There is some debate about whether Roan and Ticking in dogs are truly separate, or just variations on the same gene. I am not aware of any papers yet published with molecular studies, but it does seem that roan dogs, when outcrossed to non-roan breeds, end up with offspring that look a lot like the Belton setters. Certainly whether these are separate, similar genes or the same gene with layers of modifiers, the end result is that dogs have independent factors that will “recolor” the area that a piebald gene left white.

It didn’t seem that horses had that, at least not until recently.

In 2009 a French sport horse, Vision Morinda was foaled.

Clicking on the image above will take you to the website for her breeder, and her page which has many high-quality photos of her at all ages.

At first glance, it is tempting to assume that Vision Morinda is a tobiano with very loud cat tracking. The problem is that she cannot be homozygous. Her dam is brown. (Note that the mare she is pictured with is a surrogate. Her dam, Scarlett Fontanel, is pictured here.) But perhaps even more intriguing is the fact that her spotting seems to have intensified as she matured. That’s something that is typical of the Belton patterns. As most people are aware thanks to the Disney movie, Dalmatian puppies are born white and develop their spots later. That’s true of the English Setters and the Australian Cattle Dogs. Here is my friend Mary’s (extremely cute) Cattle Dog mix, Volt, as a puppy. (Thank you, Mary, for letting me share your photos!)

As you can see, he looks like a white dog with black patches. He is an extreme piebald. That’s why he has white ears. Well, mostly white ears. He was already starting to show some spotting there. His back and sides, however, looked white. But here is Volt today, as a grown dog.

As you can see, he developed his ticking – the Belton-type pattern – over time.

In a less dramatic fashion, Vision Morinda seems to have spotting that intensified as she matured. (Her breeders even comment on her page about the surprise of getting an English Setter color on their horse.) The spotting on her is also different, visually, from a typical tobiano with cat tracks. The pattern is evenly distributed. The spacing does change somewhat (notably across her shoulder) but it still is pretty consistent across the white areas, rather than clustering into spots or patches. It looks like the ticking you would see on a dog, not a horse.

This raises the question of whether there is some factor in horses that can add ticking – a Belton pattern, so to speak. I have a few more horses to share, all with odd spotting patterns. None are quite like Vision, but all have unexplained dark spots inside white patterns or markings. They all come from my “weird stuff” files. That’s where I put things that don’t make sense, or just seem “off” in some fashion. Sometimes enough of them accumulate – like the odd late greys from a few months ago – that it seems like there might be some thread connecting them all. I am not sure these horses really have a common thread, because they do have some visual differences, but I’m going to start posting them just to see if more turn up. That’s what happened with those greys (I have more that I need to post in the future, by the way!) so maybe sharing them will bring others out of the woodwork!

(Images at the top of the post are courtesy of Wikipedia. Images of historical English Setters come from The Pointer and Setter in America, published in 1911, and Country Life, Volume 22, 1907.)

 

May 26, 2012

Leopards, Cat Tracks and Beltons (Part 1)

Posted by The Equine Tapestry under Appaloosa, For Artists, Non-equines and other tangents, Pintaloosa, Tobiano
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Images of leopard appaloosas with Dalmatian dogs are always eye-catching. Certainly they can look quite closely matched, like this Polish Malopolski and his buddy. Even so, the patterns in the two species are very different in terms of what is really happening to the pigment on the animal. That’s probably off in the weeds for most owners and breeders, but for artists the distinction is actually pretty important.

This touches on one of the reasons why artists who develop an interest in horse color often have such a different perspective. Usually the kind of information a breeder needs is predictive. That is, they need to know what might likely result from crossing this to that, or what they might need to cross if this particular end result is what was wanted. What artists need to know isn’t about prediction nearly so much as it is about possibilities. Not so much what might happen, but what could happen – even far-out-there, not-very-likely, could happen. That’s because artists often want to add something for interest or for composition. For those producing realistic art, that has to be done within the constraints of what is possible. It doesn’t necessarily have to be likely, but it does have to be possible. This unique perspective became apparent to me a number of years ago when I gave my first presentation on horse color. In the question and answer period afterwards, someone in the audience asked if a horse could be both dappled and fleabitten at the same time. It was clear that was not the sort of question my fellow presenter, Dr. Sponenberg, often heard. But it is precisely the kind of question that equine artists ask all the time. Scientists might not notice this kind of detail on an individual horse, but for someone who paints horses, this kind of information – does this happen with this? – has a lot of practical value.

So why do artists need to understand the process behind appaloosa patterns? Spotting is a useful tool, because it breaks up positive and negative space. It makes the horse more visually interesting. If you are particularly clever, it can be used to draw the eye in a way that works with the composition, or to hide flaws. But spotting doesn’t just happen anywhere. It follows rules, and those rules depend with what is happening with the pigment. Understanding the underlying mechanism makes it far less likely that you’ll add some interesting detail that isn’t realistic. When dealing with rare combinations of colors and patterns, it might be difficult to find a reference image to consult. Knowing the process can tell you if there is a reason to bother looking in the first place, because it tells you what is possible. (And when you wing it without a reference, the knowledge will make for more reliable guesses.)

“Trouble”, sculpted by Sarah Minkiewicz-Breunig and glazed by Lesli Kathman.
In the collection of Melissa Gaulding.

This is a ceramic collectible with the kind of spotting (often called cat tracking) seen in homozygous tobianos. It’s a really popular effect. In my normal job (the one I have when I am not trying to get a horse color book to press), I have produced quite a number of these. The problem comes when this gets confused with leopard spotting, and most especially what happens when leopard patterns are combined with the tobiano pattern. That brings us back to the image at the beginning of the post. These three images – the leopard, the Dalmatian, and my ceramic foal –  represent three very different scenarios in terms of the underlying process. I want to take each, one at a time, and explain how they are different despite looking so similar.

This is the typical nose-to-toes kind of leopard. Most people would think of this as a white horse with black spots that have been superimposed on top. That’s not really accurate. From a genetic standpoint, this kind of horse is a two-step process. First she has inherited a gene that progressively adds white hairs to the coat. Those hairs, over time, are going to produce the fairly distinctive pattern known as varnish roan. If the pony in my illustration just had that first gene, she would look like a black version of this pony.

That first gene, known as Leopard Complex, sets things up for leopard but it doesn’t make leopard patterns itself.

That happens when the horse inherits a separate patterning gene in addition to Leopard Complex. In this case, that patterning gene is called Pattern1. What Pattern1 does is take the white from Leopard Complex and amplifies and organizes it. So while our horse looks like she is white with spots, it is perhaps more helpful to think of her as a horse that was roan, but Pattern1 has now taken that mixture of white and dark hair  and reorganized it. Underneath the white hair, what that horse may look like is closer to this.

This is what the underlying skin looks like. She probably does have some truly white skin in the area where a blanket pattern would go. Pattern1 does amplify the white, after all. But under it all she isn’t really a white horse, at least not in the sense that most people would think of as true white. She is more like a roan horse that has been modified a bit. That’s why even nose-to-toes leopards have faces that are shaded much more like a grey than a cremello, because for the most part the face has dark skin, not pink skin. And that is why a pintaloosa looks like this:

The true white areas of the tobiano pattern cover over the appaloosa pattern. The spots from the leopard pattern don’t spread over onto the tobiano pattern because the process with Pattern1 isn’t “add dark spots to the white”, it is “organize the roan into spots.” So the spots don’t happen where the tobiano pattern already took all the roan away. Without the color there in the first place, Pattern1 has nothing to work with.

Of course, if we moved our tobiano pattern out a bit, encompassing more of the dark skin and butting it up close to the “blanket” skin, we could probably get something that looked a bit like the leopard spots migrated over some of the tobiano.

Even so, the spotting is still concentrated in such a way that shows it is an appaloosa pattern with a tobiano pattern layered over the top of it. The spots on the flanks might look like they are in the tobiano white, but really they are just in an area that was already white from the action of the Pattern1 gene. The action is still the same. The tobiano is there adding true, pink-skinned white on the horse, and underneath it Leopard Complex and Pattern1 are just doing their thing.

Even with the tobiano bumping up to the pink-skinned areas of the leopard pattern, it still looks different from the kind of spotting that comes from a horse having two copies of the tobiano gene.

This is a (presumably) homozygous tobiano with cat tracks. Whereas Leopard Complex is a roaning process that Pattern1 takes and organizes into the leopard pattern, this type of spotting is more like a not-entirely-successful attempt to add some more color to a horse that already has large patches of color. Unlike the existing spots, which are large and opaque, these new spots are small and vary in opacity. Some just come through in specks.

Cat tracking tends to cluster around the existing spots to some extent, almost as if these new spots want to occupy the same general area as the existing spots. This is quite different from the spotting on a leopard, which tends to be dispersed across the body.

The exception is the hooves. Tobianos with cat tracks often have a concentration of spots around the coronary band, often turning the hoof completely dark or nearly so.

There are spots on the legs, but typically they are not as numerous as the ones around the feet. The same is true for the face. This is the face that goes with these feet. He does have a few spots in his blaze, but they are not extensive.

So how is this different from the Dalmatian? Well he really is a white animal with colored spots added on top. In dogs, the gene for this is usually called Ticking, but since ticking means something different in horses, I am going to use the older English term for the pattern, which is belton. This post has run really long, so I’ll split that over into a second part. And why delve into the belton pattern in dogs? Because lately there has been a handful of horses that have turned up that just might have that kind of spotting. At the very least there are horses with dark spots inside their white markings that are not tobiano cat tracking and not leopard patterning. More on those will appear in the next post!

 

May 25, 2012

All kinds of updates

Posted by The Equine Tapestry under Dilutions, From The Book
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I apologize for neglecting this blog this past month. My time has been almost completely absorbed in the final production work for the book. The good news is that the book is just a few weeks away from publication, though I am almost afraid to jinx it by saying so! What time hasn’t been spent on the book has gone towards a handful of print articles. This has all meant that the blog has languished simply because I couldn’t face writing anything more.

Which is a shame because I sure haven’t lacked for things to share. While I have been quiet, all manner of interesting things have been piling up on my desk and in my inbox. One of them is the picture at the top of this blog. I truly wanted to include it in the book, but I never heard back from the Tyne & Wear Archives and Museums regarding commercial usage of the image. They do allow non-commercial use, though, so I thought I would share it here on the blog. The reason I wanted it for the book is that I have a chapter on the now-extinct Hanoverian Creams. Those were the ceremonial carriage horses that were once used by British royalty, but are now extinct. They have long held a certain fascination for horse color researchers because their exact color is not known. The other mystery is what ever became of them. It is known that some of their Continental relatives ended up in the Wulff Circus, and that a handful of the British horses ended up with Garrard Tyrwhitt-Drake. This image caught my eye because the horse has the same diluted coat with the very dark mane and tail that is seen in some of the later images of the Creams. But even more interesting, the photo is part of a group associated with Lord John Sanger’s circus. There is a connection between Sanger and Tyrwhitt-Drake, so it is quite plausible that this horse was one of the Creams, or was related to them. The photos are not dated, but the range from the other photos in the set are correct for the horses that were dispersed to have still be alive. If anyone recognizes the image and can place it or date it, I’d love to hear from them!

There have also been a couple of interesting horses that have come to light in just the last few weeks. The first is another white-born Standardbred recently foaled in New Jersey. Pictures of him can be seen here. Since both is sire Art Major and dam Coochie Mama are unmarked horses, he is quite likely a new dominant white mutation. Another suspected dominant white Standardbred, Macahan Loss, was born in 2008.

The other cool new horse is a confirmed silver dilute Pura Raza Espanola (PRE). That is the mare Trajana YR. She is actually chestnut, so the color is not visible on her, but she carries the gene. If she is bred to a bay or black horse she could produce a black or red silver (bay silver). Some readers might remember a few years ago there was a PRE stallion that was rumored to have been tested as a silver, but many questions were raised about his purity and his testing status. His owner stopped replying to questions (not that I can say I blame them, given the truly unpleasant tone that many took), and it became a dead end. Hopefully this mare puts an end to the debate over whether the gene is there or not.

Speaking of the silver dilution, I was able to get some really wonderful contrast shots a few weeks ago. The opportunity to have two visually similar, but genetically different, colors side-by-side only come up on rare occasions, so I was tickled to have gotten these shots. I haven’t had time to crop and size the photos, but eventually I will have those up on the blog. And I still have to post the “English translation” for the splash research, and some much-needed updates to the Splash Project page. And there are other cool things that just need to be sorted and composed. So like I said, there is a lot to share – just not enough hours in my days at the moment!

 

April 13, 2012

Macchiato

Posted by The Equine Tapestry under Macchiato, Splash overo
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As I posted briefly yesterday, the new paper on splashed white had a lot of surprising information, not the least of which was the horse pictured in yesterday’s post. A number of people wondered about his identity, and most particularly about his breed. His name is Apache du Peupe, and he is a four year-old Freiberger. The Freiberger is also called the Franches-Montagne, which sometimes leads to confusion. The horses in the picture above (courtesy of Wikimedia Commons) are quite typical examples. Freibergers are among the last of the European light draft breeds, though in more recent years many breeders have focused on a slightly lighter riding type, which is why I choose to shift them – and a few others, like the Frederiksborg – to a later volume rather than include it in the draft and coaching breeds.

Because they were originally included in the upcoming volume, I had looked into the range of colors in the breed. Apache came to my attention during that time. Freibergers were already interesting because they had a well-documented family of dominant whites. Those trace back to a white mare, Cigale, born in 1957. She was the source of what eventually became the first formally identified dominant white mutation. Hers is the mutation that got the designation W1. That is what I thought Apache was, until I realized that he was not related to Cigale. In fact, his parents did not look all that different in color from the two horses pictured above.

Here he is again, from yesterday’s post:

This is his sire, Noble Coeur. This is his dam, Muscade. Both are clear bays with socks and minimal face markings. Apache and his parents are the kind of horses that sat in my “don’t fit the theory” file when I first wrote about maximum sabinos (sabino whites) in the 1990s. The horses that did fit that theory turned out to be Sabino1, the spotting pattern that results in a white horse when homozygous. All the horses that fit the theory had parents with a high number on my ranking scale for white markings, while most of the horses in the “don’t fit” file had parents that fell short. Typically they did have some white, but it was a stretch to say they were marked like the others. Had Apache and his parents come along at that time, they would have ended up in that same file. Many of the horses there (R Khasper, White Beauty, Puchilingui) were later identified as dominant whites.

So I wondered if Apache was another new dominant white mutation. But there was another aspect to him that made me wonder, and that is why – up until yesterday when he appeared in the splashed white paper – he was in my “mystery” files. If you look closely at his picture, he looks diluted. If he were a Paint horse, or almost any other American stock or gaited breed, I would assume he was buckskin. Here are more pictures that give that impression.

Cantering (with is spin visible to show no dorsal stripe)
Conformation (quite current, shot in 2011)

That was what was so unusual about him. His parents are, as the links show, quite ordinary bays. And even allowing for the fact that he probably has a good portion of white hairs mixed in his coat, the tones give the impression that the actual hair is diluted. His owners called his unusual color “macchiato”, for the coffee drink, which suggested that he was cream-colored in person. Since his parents were not diluted, and since I had no evidence that cream (or any other dilution) was present in the Freiberger, I wondered about the accuracy of his pedigree. Pattern mutations do appear, but a pattern and a dilution all in one horse?

And now with the publication of the splashed white paper, we know that is exactly what he has: a mutation that is both a dilution and a white pattern. Researchers parent tested him using 13 markers, confirming that he really was the offspring of the parents of record. What’s more, they tested blood, hair roots and sperm to rule out mosaicism. Mosaics are animals that have two separate sets of cells with different genetic coding. Horses that are patched with black and chestnut, for example, are mosaics. Apache is, genetically speaking, all one horse with the same genetic makeup throughout his body. They also looked at the genes currently known to produce dilutions, and found nothing out of the ordinary. So he’s not a cream, a silver, champagne, pearl or dun. He is what is called a de novo mutation – something new.

The new thing that he has is a mutation at the same location as splashed white, which is the MITF gene. The color Apache’s breeders named Macchiato is a form of splashed white. Technically that makes four identified splashed white patterns, although researchers declined to name his SW4, perhaps in deference to what his breeders were already calling the color. So far the other MITF mutation for which we have numerous examples to study, SW1, does not seem to have the diluting component. The third, SW3, is said to be rare and none beyond the two horses pictured in the paper have come to light so far. Neither of those two horses appear diluted, but two is not a lot of data, especially when one is too white to really evaluate base color on anyway.

But what is interesting is that Apache’s mutation has a human equivalent. The human Tietz Syndrome is caused by a similar mutation. The Office of Rare Diseases Research describes Tietz Syndrome this way:

Tietz syndrome is a genetic condition characterized by profound hearing loss from birth, fair skin, and light-colored hair. This condition is caused by mutations in the MITF gene.

A second human MITF mutation causes Waardenburg Syndrome. Again from the Office of Rare Diseases Research:

Waardenburg syndrome is a group of genetic conditions that can cause hearing loss and changes in coloring (pigmentation) of the hair, skin, and eyes.

So a similar mutation in human beings causes pale hair, piebald patches (in the Waardenburg Syndrome) and pale eyes. It also causes deafness, which was also true for Apache, who tested to be deaf.

That raises the question of whether or not other as-yet-unidentified splashed white patterns might not have a dilution component like that seen in Apache. Certainly several of the horses from the Bald Eagle line have a very similar base color to Apache du Peupe. I had assumed that, being stock horses, the were getting their diluted color from the other parent. It would certainly be worth looking at the members of that family to confirm that those with diluted base colors actually had a diluted parent. That isn’t something that ever would have occurred to me to look for, because “dilution” and “white pattern” were completely separate categories of colors up until yesterday. As I said, it is an exciting time to study horse color, because there really is something new to learn all the time!

So that’s three of the four mutations. Someone probably noticed that one got skipped. That is SW2, and if Macchiato complicates how we categorize mutations, that one complicates how we are naming them. I’ll open that can of worms in the next post!

 

April 12, 2012

Splashed white paper is published

Posted by The Equine Tapestry under Macchiato, Splash overo
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The long-awaited splashed white paper has now been published in PLoS Genetics. The full article can be read here.

As a number of people predicted, the MITF gene is involved, but there are also some surprises. One of them is that the authors looked into the odd case of the Freiberger stallion, Apache. Above is his picture from the paper, and the link from his name will take you to a site with more pictures. His owners called his odd color and pattern “macchiato.” He’s been in my “mystery” files since I first stumbled across him a year or so ago, so I was tickled to see that he was included in the paper.

It will take me a day or so, but I will try to put up a plain English summary of the paper. It is an exciting time for those of us interested in animal coloration!

 

April 4, 2012

Catching up…

Posted by The Equine Tapestry under Uncategorized
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Just a quick note that the previous post on dogs was composed during our family’s annual trip to Pawleys Island. I am still shaking the sand off my feet and realizing just how much was left undone while I enjoyed the live oaks and the azaleas. If you are waiting for a reply from me, or if your message was caught in my (over-vigilant) spam filter, don’t give up yet! I should be caught up in the next day or so. (Or at least as caught up as I ever actually manage to be!)

 

April 4, 2012

Why talk about dogs?

Posted by The Equine Tapestry under Genetic diversity
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These two Dogue de Bordeaux have the extremely narrow, upright nostrils that are common in the breed. This and other anatomical exaggerations are why the Dogue is included in the Kennel Club list of high profile breeds subject to separate vet checks at shows. (Photos from Wikipedia.)

As I mentioned in the previous post, I want to do a series of posts on the subject of genetic diversity. Obviously the primary focus of this blog is horses, but for this particular topic I will be jumping back and forth a bit between the world of dogs and the world of horses. The situation in many purebred dog breeds is quite dire. With few exceptions, horse breeds do not face nearly such difficult circumstances, and because of that, most breeders of horses do not face the same difficult choices. Still, the factors that allowed purebred dogs to reach this point are not entirely absent in horses. It is also true that because dogs are so pervasive in our culture, many people have had their views, particularly those about what constitutes a ‘proper breed’, influenced by the world of pedigree dogs. For that reason, I will present the situation with dog breeding as a cautionary tale for those interested in horses.

So what has happened to dogs? Three independent inquiries were made in the aftermath of the British documentary Pedigree Dogs Exposed. These produced three separate reports: the Bateson Report, the APGAW Report and the RSPCA Report. All three groups found that the health and welfare of purebred dogs were compromised, and highlighted two contributing factors. The first of these was selection for exaggerated anatomical features. The second was the dramatic increase of inherited disorders brought about by inbreeding.

These observations were not new. In 1988 the British Council for Science and Society produced a report on companion animals. It noted the problems in the following statement:

An in­creasing number of hereditary problems are being recognised in companion animals, especially dogs. Many of these are the consequences of inbreeding or breeding for genetically defective animals. Some are the result of deliberate selection for abnormal or unnaturally accentuated physical characteristics for fad or fancy.

As that quote shows, both exaggeration and inbreeding were concerns twenty-four years ago. The observations made in the three reports were not new, but this time there has been public pressure to address the problems.

It is the efforts undertaken by the Kennel Club (KC) to address the first issue – the harmful anatomical distortions – that are currently the focus of much controversy in the British dog world. That controversy has created ripples over in the American dog fancy as well, with representatives from the American Kennel Club (AKC) insisting that such measures will never be taken in the United States. Meanwhile the second largest American registry, the United Kennel Club (UKC) has stepped forward to claim the high ground in addressing the issue.

This first issue will not be the focus of the posts made here. As important as the issue is to the dog world, it is not a widespread problem facing horse breeds. With a few exceptions – extreme heads in some halter Arabians, for example – breeders are not seeking to exaggerate the equine form. Horses are not anatomically malleable the way dogs have proven to be.

(These graphics come from a Belgian blog devoted to ethics in the breeding of German Shepherds.)

It is the second category of issues – those related to inbreeding – that are the bigger concern for horses. There is no question that within the horse world, there are endangered breeds with very small populations. Many of the draft and coaching breeds have experienced dramatic bottlenecks when the engine made them obsolete. It is also true that closed stud books and inbreeding are found in some horse breeds, and that some breeds have seen a rise in genetic diseases.

So why is inbreeding – in dogs or horses – a concern? Here is what the Bateson Report had to say:

Unquestionably inbreeding can lead to a loss of biological fitness. …. Inbreeding can result in reduced fertility both in litter size and sperm viability, devel­opmental disruption, lower birth rate, higher infant mortality, shorter life span, increased expression of inherited disorders and reduction of immune sys­tem function. The immune system is closely linked to the removal of cancer cells from a healthy body, so reduction of immune system function increases the risk of full-blown tumours.

These same observations are echoed in the other two reports. All three drew upon the expertise of geneticists for those conclusions. However much inbreeding is considered a valid tool by some animal breeders, the above statement is not particularly controversial within the field of genetics. Concerns about the downsides of inbreeding are pretty consistent across a large body of studies. It is the growing awareness outside that field that is new.

A few months ago, National Geographic did a feature story on the genetic variation found in dogs. One section jumped out at me when I was reading it, in part because the implications were terrible, and even worse I suspected many readers did not realize it. Perhaps pairing it with the above quote about inbreeding will make it more obvious. (Bold emphasis is my own.)

In short, while the Victorian breeders were crafting dogs to suit their tastes, they were also creating genetically isolated populations, little knowing how useful they might be to scientists in the future. The possibilities are especially abundant for cancer, certain types of which can show up as often as 60 percent of the time in some dog breeds but only once in every 10,000 humans.

Here is a similar observation from a peer-reviewed journal article:

Selection for phenotypic traits has resulted in the latent selection of genetic diseases and some breeds now have a high incidence of particular diseases, for example, the Samoyed, which has a risk ratio if 17.3 for diabetes and the boxer which has an unusually high incidence of various cancers.

The breed specificity of particular diseases lends dogs to be ideal candidates for comparative genetic association studies.

That is the precarious position of purebred dogs in 2012. Their genetically isolated populations have several hundred known genetic diseases. Because the dogs have been maintained in small subpopulations with decreasing genetic diversity, the incidence of those diseases has risen to the point that researchers have found them to be an invaluable resource. That may be good news for those seeking answers to human disease, but it is far from good news for the dogs themselves. It certainly should give pause to breeders of other animals that are considering taking (or continuing down) the same path.

It also merits thoughtful discussion by all involved with the animals affected – those that breed them, those that exhibit them and those that welcome them into their lives as companions.

 

March 29, 2012

Of math, fashion and wiffle hounds

Posted by The Equine Tapestry under Equine-related tangents, Non-equines and other tangents
[9] Comments 

My oldest son has been struggling with freshman Biology, so the concept of evolution has been on my mind a lot lately. I have also been reminded that evolution applies, not just to organisms, but of points of view. Sometimes it can be easy to forget that you once held a different view – unless of course you are foolish enough to write it down for others to find later. I have been writing about horse color long enough now that I have had that happen!

The reminder of this came from my husband. Longtime readers of the blog have probably picked up on the fact that I have a strong interest in the issues surrounding genetic diversity. It is, as I have mentioned, one of the themes that runs through the upcoming books. My close friends could probably warn readers that it is a tempting soapbox for me, particularly when it comes to the topic of dogs. That was exactly what I was doing – standing on that soapbox – when my husband reminded me that I once held a very different point of view on the subject.

He has every reason to remember this, since there was a time when the topic came up often between us. My husband is a physicist working in the field of optics. When we first met, he was intrigued by the possibilities of using genetic algorithms to solve complex design problems. A genetic algorithm is a mathmatical tool that narrows down variables by “breeding” the possibilities until an optimal solution is found. He was experimenting with genetic algorthims, and I had recently bought my first Arabian mare after spending most of my teen years planning my future breeding program. I was more than happy to explain all the different inbreeding, linebreeding and outcrossing schemes breeders had developed over the years.

I was familiar with them because I had my heart set on breeding animals, most specifically Arabian horses and Rough Collies. Since I could not convince my parents of the pressing need to start populating our home with dogs, or to acquire land for horses, I used the time to learn all I could for the day when I could do those things. When the time came, I was determined to be the most informed breeder possible. I devoured issues of Arabian Horse World. It was the 1980s and  the market for Arabians was at its peak, so each issue brought countless images for a horse crazy girl trying to determine just what qualities she would emphasize in her hypothetical breeding program. While other girls were pouring over fashion magazines and beginning to notice boys, I was filling ring binders with notes on bloodlines and affixing sticking notes to the important pages. As you can see, many of them are still there today.

I was smitten by pictures of the stallion *El Shaklan. The more something looked like an imaginary elven horse, the better. I was not an especially practical kid.

Arabians appealed to my artistic sensibilities. My interest in Collies came about in a more personal way. My grandfather was a Collie man, and encouraged me to read Albert Peyson Terhune’s books. Mr. Terhune had lived in the same town, and traveled in many of the same dog circles, as my grandfather’s family had when he was a boy. Like so many, I fell in love with the breed as it was portrayed in Mr. Terhune’s books. When my parents offered to give me my very own dog for my twelfth birthday, getting a Collie seemed a natural choice.

My grandfather’s favorite Collie, Glengay Sandy Boy. The inscription on the back of his photo is the Terhune quote, “a thoroughbred in body and in soul.”

I knew the “proper” way to obtain a quality dog. My parents, however, had different ideas. I wanted the perfect bitch with which to start my grand breeding program. My parents wanted something within their price range and a reasonable driving distance. The result was the dog at the top of this post. She came from a local farmer who raised a few Collies on the side. She wasn’t the potential foundation female I would have liked to have gotten, but she was a dog of my very own. When you are twelve, that counts for a lot.

My grandfather, when he received her photos, was quite critical. She had a pronounced stop, which was not proper. The angles of her face were all wrong, and she carried her tail in something awful close to a curl. But the real deal-breaker were her prick ears. As soon as she left the puppy stage and those ears went up, he ceased to consider her a Collie. Purebred Collies had tipped ears. She was, he insisted, nothing more than a “Whiffle Hound.” She was no relative of his beloved childhood Collie, Sandy.

Looking back, perhaps that reaction planted the seeds of doubt about what was valued in the animal fancies. It was obvious to anyone familiar with the standard that Brandy was a Collie of inferior type. I would have readily admitted as much. She was, however, a wonderful companion for a young girl. I thought she hung the moon, and her over-large, erect ears seemed like such a little thing in comparison to all that was great about her. We competed in obedience for much of her youth and mine, and it was pretty clear which of us did the better job. (Her ears were less of a limiter than my tendency to confuse left and right.)

Pictures of my grandfather with his ‘thoroughbred’ Collie, Sandy, and me with my ‘wiffle hound’, Brandy. Interestingly enough, we are the same age in these photos and adopting quite similar poses as we encouraged our dogs to do tricks for the camera.

But when Brandy passed away at fifteen years of age, I was explaining close linebreeding (the word I used at the time) to my husband. I had absorbed those ideas from the cultures that surrounded Arabians and Collies, and if anything was going to marinate a young animal lover in the twin concepts of “blood purity” and the usefulness of inbreeding, it would be the world of those two breeds.

But something happened along the way. Soon after we married, my husband’s work took us away from our small farm in Alabama, and to city life here in Charlotte.  I had already begun to question the consuming nature of raising dogs and horses, having seen that more closely through the experience of a number of friends. My interest in breeding animals became more academic, and less about laying the foundation for future activities. My mindset shifted from future breeder to a person who would own a series of beloved family companions, and who just happened to be very interested in the topic of genetics and breeding.

It was the academic interest in animal breeding that exposed me to a new way of thinking about breeding programs. My interest in color motivated me to read journal articles. Many of the authors of those articles also wrote about breed conservation and genetic diversity. Over time, the ideas presented in those papers brought about an evolution in my thinking. Like classical evolution, the change was gradual – a shifted position here, and new insight there, until something quite different took the place of what had been before.

Thankfully for me, this process occurred in the peace and isolation of my own research. I could think about the issues involved in a fairly objective, unemotional manner because no one was clamoring for me to reach a specific conclusion. Now many of those issues have become a source of controversy and bitter battles within the animal fancies. This has played out most visibly in the British dog show world, which was rocked three years ago by the documentary Pedigree Dogs Exposed. That program brought genetic diversity out of the realm of academic papers and into the public square. It is pretty safe to say that unemotional is not a feature of the situation!

In this reaction, many have called the focus on genetic diversity a passing fashion. That is not surprising, since fashion has long driven animal fancies. That is a natural frame for viewing motivations behind breeding decisions. I do believe, however, that calling the subject a fashion does a disservice to kind of thought that goes into breeding decisions. The acceptable angles of a Collie head, and the proper carriage of their ears, is a fashion. The acceptable amount of white on the legs and face on a horse are a fashion. The benefits and hazards of an increasingly homozygous population is a much larger issue. The truth is that breeders are dealing with competing concerns, with uniformity and predictibility being the very essence of selective breeding, and with its opposite, heterogenity, being so closely tied to health. That is not fashion: that is about the limits of the system as it really is. It is essential to understand those trade-offs if breeders are to make good decisions.

As I have said, the Equine Tapestry books touch on the subject of genetic diversity. Because the way a registry defines “breed” and “purity” has a huge impact on colors – both what is ruled in and what is ruled out – it is quite relevant. It is also true that misconceptions about purity and breed integrity have big implications for animal coloring. Because color is so easy to see, and is often the result of far more straight-forward inheritance than things like conformation or breed type, it tends to be on the front line of selective pressures. But beyond those issues, it is my hope that the books will raise questions about how we integrate our growing understanding of genetics into real world breeding decisions.

I have a few more posts to make that expand on some of these ideas, since I want to bring some of these ideas back to issues that touch more directly on color. I also plan to add another page (much like the Splashed White Project page) to the blog with a collection of links for further reading on genetic diversity. Perhaps they can plant the seeds for a more rational dialogue on the topic.

Twenty years ago, when I talked to my husband about linebreeding, I never mentioned genetic diversity. It was not a concept that had come up in my reading at that point. Today when I pulled the copy of my husband’s book, thinking I might find some of the images that came from his work in genetic algorithms, I found the following passage:

We intuitively know that larger populations will bring greater diversity and better sample the solution space. If the ranking function is nearly flat, poor attributes will stay in the population longer. If the ranking function is steep, the population swiftly becomes inbred. A lot of mutation can slow the convergence, while no mutation will lead to premature stagnation through inbreeding.

That passage pretty much sums up the situation facing breeders. If the selection process (what he calls a ‘ranking function’) is minimal, we will get a mix of good and bad attributes and not a lot of control over which we get from any particular breeding. That is the part I knew. At the other end, if we use extremely strict selection, we run the risk of a dead end where the variables present are too limited to provide the answer to a problem. For many, my younger self included, that is the missing piece. I may not have understood then, but the math certainly gave my husband a more complete picture. It almost makes me wish I hadn’t spent so much of my high school algebra classes doodling horses in the margins of my notebook.

 

March 22, 2012

Body clipping

Posted by The Equine Tapestry under Oddities
[2] Comments 

Body-clipping a horse can give some really strange results, but I thought this warmblood was particularly interesting. I’ve noticed that clipping a horse sometimes reveals dappling that is not evident on the regular coat. That seems especially true for silver dilutes. I’ve also noticed that some clipped horses are rather unevenly colored, and that even more of them grow back with uneven color, but this is the first one that I have seen where those uneven areas look so much like a dappling pattern in reverse.

Here are some more angles on the same horse. (And thank you again to Kim Smith for sharing her pictures. Getting such numerous clear shots of unusual colors is such a treat!)

Notice on this last one how the dark area on the hind leg follows the pattern of the veins, just like ordinary dappling does in reverse.

I must admit that my own experience with clipping is very limited, so I don’t know how common reverse dappling might be, and whether it is something seen when the horse is clipped or something that appears as the coat grows back. Perhaps owners of Miniature Horses, which are often clipped for showing purposes, can share their experience with color changes.

I do know that horses like this are often mistaken for roans or even for duns, especially in photos where the difference in hair length cannot always be seen, because of the contrast between the head and the body color.

 

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