Tag Archives | Kladrubers

Early greys and fading whites

earlygrey

A short time after the posts about Dominant White went out, I was contacted by someone about a family of seemingly white Miniatures. The stallion was advertised as a maximum white sabino, which is often how Dominant White horses are described. The writer wanted to know if I thought the horse was a White or a Sabino. She thought they might be Whites because of this quote from the Wikipedia entry about the color.

Horses with the W3 allele often retain interspersed flecks or regions of pigmented skin and hair, which may fade with time.

That quote was in reference to the third identified family of Dominant Whites, which began with the mutation in the Arabian stallion R Khasper. A few of the other Dominant White families – but not all – have this same tendency. Photos of the Freiberger horses in the original white study (W1, the Cigale family) show this phenomenon really well.

Here is a Cigale descendant as a foal.

514px-DominantWhiteHorsesB

Here he is as a mature horse.

653px-DominantWhiteHorsesC

(Both photos are from the original journal article by Haas and Brooks.)

The writer wondered if the same thing was happening with the Miniatures. Looking at the pictures, it was clear that whatever else was going on with the stallion, he was a tobiano because he was throwing a lot of tobiano foals from unmarked mares. The fact that some of those tobiano foals turned white really quickly was why Dominant White was suspected. Because the dark areas of their tobiano patterns looked to have uniformly dark skin, my own suspicion was that the foals at least were not White, but early greys.

Andrea Caudill sent the picture at the top of this post, and it is perhaps helpful in this case. The colt is two years old, and almost entirely white grey. His legs are muddy in the photos, but Andrea says they were also white. As a thin-coated race horse in what is probably a wet environment, it’s easy to see his dark skin. In my experience, it can be much harder to tell white greys with extensive markings or facial depigmentation from truly white horses when they are dry and have denser coats.

Some horses, like this colt, do grey really early. Famous white grey breeds like the Lipizzans and Kladrubers have been bred specifically for early and thorough greying. Conversely, breeds like the Percheron have been bred for later greying, so it would appear that greying speed can be manipulated by selective breeding. Perhaps even more interesting, and relevant to the situation with the Miniatures, is that early studies on the silver gene mentioned that pairing silver (Z) with grey (G) produced really rapid greying. I do not believe this was studied in-depth, but it is true that a number of Shetland breeders in the mid-twentieth century were attempting to breed “white” ponies that were in fact early greys. That might be what was happening with the Miniatures in question.

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Depigmentation on greys

Depigmented

One of the best places to study horse color is the wash rack, and BreyerFest was no exception. This is one of the guest horses at the event, Pecos. He is a 13 year-old PRE stallion. As the pictures in the link show, he appears to be a grey that has turned uniformly white. When wet, though, small spots of depigmented skin are visible.

Many greys lose pigment as they age, and this seems particularly true of horses of Spanish descent. What makes the depigmentation on Pecos a bit unusual is that it is not concentrated on his face or his undersides. Notice in the picture above that his sheath area is still quite dark. (I did not think to take a shot of the area under his tail, unfortunately, but I suspect it too is still mostly dark.)

This shot shows that his face is also mostly dark.

Depigmented2

I did not get any shots of the front of his nose since he was rather intent upon wuffling the rack, but this picture shows how the area around the borders of his marking as started to mottle. That is common in older greys and seems especially common in the breeds that are prone to depigmentation.

Two of the breeds covered in the upcoming book – the Boulonnais and the Kladruber – get an even more dramatic form of pigment loss that appears to effect the face. Studies done in the Czech Republic suggested that the two types of depigmentation in greys – one concentrated on the undersides and one on the face – are genetically distinct from one another.

Neither look much like what is going on with Pecos. His owner said that this was a recent development and that they thought it was a reaction to medication.

The spots are also unlike Tetrarch spots, named for the famous grey racehorse who had them.

Tetrarch spots usually appear in the earlier stages of greying, and disappear as the horse greys out. Photos suggest that these kinds of spots have dark skin under the white hair, rather than white skin like the spots on Pecos.

Pictures of one of the extensively depigmented Kladrubers appear in the upcoming book. Horses like that are interesting because their presence could mask others kinds of patterning in an all-grey (or mostly grey) breed.

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More on closed registries

KladruberFoal
(Photo by Tereza Huclova, provided for the upcoming book by the Kladruber Stud)

Several people have commented about the convex profiles of the Kladrubers and how they are visible even in the foals. I thought I would share this photo since it illustrates the characteristic so well. The extent of the arch varies from horse to horse, but it does seem especially pronounced in the black horses. As someone who grew up around Walking Horses when this type of head was not uncommon, I find it very appealing.

I also received a number of responses about genetic diversity and closed registries, so I thought I would include some links and reference material for those with an interest in the subject.

As Sarah Minkiewicz-Breunig mentioned in her comment, I like to recommend the book Bred for Perfection by Margaret Derry.



In the book Derry explores how culture, economics and the (then new) science of genetics shaped the world of stud books and animal breeding. She doesn’t shy away from the less appealing aspects of that history – namely the close association with eugenics and social Darwinism – but she does so in a less sensationalistic way than many.

There are also a lot of resources from the dog world, in part because rigidly closed registries have long been the norm within that community. One of the best sites for articles is the Canine Diversity Project.  Among the particularly good ones are:

The Poodle and the Chocolate Cake by Dr. John Armstrong  (a really good overview of the problem)
The Price of Popularity: Popular Sires and Population Genetics by C. A. Sharp

The dog world has also had some interesting experiments with out-crossing. Closed registries are the norm for dogs, so these have all been very controversial. Among horses relatively few breeds maintain completely closed stud books, and fewer still are willing to pay for that choice in the way that dog breeders are.

The Backcross Project  (restoring proper uric acid levels to Dalmations)
Bobtailed Boxers – Part 1
Bobtailed Boxers – Part 2
Bobtailed Boxers – Part 3
Bobtailed Boxers – Part 4
Bobtailed Boxers – Part 5
Bobtailed Boxers – Part 6
(This series is worth reading just to see how quickly a breed reverts back to type when crossed on something really different, all extensively documented in pictures.)

There was also a great post on the Terrierman blog about the importance of provenance in selling breeds.
You Can Blame Garrison Keillor’s Grandfather
The Terrierman blog has a lot of great posts about genetic diversity, though that recommendation comes with two caveats: 1) the blog is routinely sprinkled with unrelated politics that readers might or might not appreciate and 2) temperance and diplomacy are not really the style there. (He also takes exception to the color merle, which of course is not going to fly around here at the House of Blue Dogs!) Still it is consistently an interesting read, and it is worth exploring the (vast) archives there.

There is also the BBC program “Pedigree Dogs Exposed” which one of the comments referenced. To say that the program ignited a firestorm would be an understatement, and in parts it is certainly sensationalized. Still, what it portrays is happening, and perhaps something like this was the only thing that would push people to look at the issues involved. Since it aired, studies have been conducted and some preliminary actions taken by the British Kennel Club.

So what does that have to do with horses? To some extent horses and horse breeds are in better shape because they have not had a uniform culture of closed registries. Still where there are small populations and closed breeding programs, the same kinds of issues arise. Here is a discussion of the Friesian stud book policy on genetic disorders. This statement shows the very real parallel with the problems facing the dog world:

For this reason, the KFPS believes that carrier stallions should remain in the breeding pool. In addition, it should also be possible to approve young carrier stallions on the condition that they possess extra qualities. If we do not implement this policy, 1 in 3 young stallions will automatically be rejected on the basis of DNA testing.

One in three. And what are they carrying? Dwarfism. Twelve of the current stud book stallions are carries of dwarfism. Hydrocephalic Foals. Sixteen of the current stud book stallions are carriers of hydrocephalism. The effective breeding population is too small, and the defective genes so widespread that culling the carriers would probably narrow the gene pool enough that new defects would appear. That is what has happened in many dog breeds. It is exactly what should concern horse breeders, particularly those working with rare breeds with limited populations.

That is why many rare horse breeds have actually relaxed their color restrictions. They may still have strongly worded preferences for colors or markings, but off-colored or mismarked horses are not automatically removed in many breeds. Ironically, one of the breeds that does do this is the Friesian, which does not allow chestnut carriers as breeding stallions. This puts the registry in the awful position of permitting damaging defects if the horse is otherwise “of good quality”, but banning something as inconsequential as color no matter how nice the horse. As with dog breeders, this kind of disconnect with simple animal welfare undermines the assertion that purebred breeders are guided by a higher standard of ethics than “backyard” breeders.

Were it possible to expand the gene pool, culling could be accomplished without raising the inbreeding level to still more dangerous levels. Even without outright culling of carriers, introducing an outcross line can dilute the overall incidence of the defective gene. The fact that there are animals breeders out there who will choose “purity of blood” over solving serious health issues is something that deserves more attention. It isn’t a particularly comfortable discussion for a lot of breeders, and it points to the need for a very different mindset when it comes to breed stewardship, but it is one I personally feel must happen.

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