Regarding the possible future DNA testing for Chondrodysplasia-like Dwarfism

[Minimor]

Well, I have never had a dwarf but....have to say that of I did I would never have bothered with getting papers for it--why bother???? I would have stopped breeding both sire and dam, and I sure wouldn't have paid for dwarf papers on the foal.

I suspect that many/most people would not bother either--and many would just dispose of the dwarf and not admit that it ever existed. So, I don't see that dwarf registrations would have done much to expose the dwarf producers.

 

[Lewella]

I think that IF the miniature registries would have acknowledged dwarves born to registered stock the whole breed would have been able to make better informed decicions a long time ago. All that they would have to have done is to give the dwarves some type of registration that would NOT allow breeding OR showing. The lines which throw dwarfism would have been known a long time ago, thus breeders would have been able to make better informed breeding choices a long time ago and the cropping up of dwarves, in theory, would have dwindled. Horses that were known to throw dwarves could have had their papers stamped as dwarf carrier, thus making choices easier for all involved.

While this might sound good in theory, it would have failed dismally in practice. It wasn't all that long ago that both registries were completely open with no hardship clause. When the registries were completely open people would buy a registered horse and then proceed to reregister it with a different name and unknown parentage. There are probably thousands of horses that wore multiple sets of papers during their lifetime with multiple names. Dwarf producers could have simply been sold and repapered with no one the wiser that the horse had produced a dwarf (and probably were). I don't know when AMHA instituted its hardship clause but I do know AMHR didn't until the mid-1990s. So we're talking less than 20 years since that registry was completely open and you could paper a horse however you wanted to. It would have been impossible to track dwarfism in a completely open registry.

 

[rabbitsfizz]

AMHA "closed" in 1987/8, but hardship was easy and relatively cheap.

 

[horsehug]

Hardship with AMHA, ever since it was started in the late 80's or very early 90's, has been $600 for a mare and $1200 for a stallion.

I have done it several times but have always felt it was expensive. I just wanted the ones I have done to be in the AMHA bad enough to spend the money.

However, to others it might not seem expensive like it has to me. I cant speak for anyone else's finances.

The first mare I ever hardshipped in was back in 1990 or 1991 and it was $600.

Susan O.

 

[rabbitsfizz]

HH I think the exchange rate was different back then!!!

Also, it was actually still possible to hardship in Europe before the AMHA shut the door, without consultation or warning.......

 

[amysue]

The possibility of testing for dwarfism poses both benefits and issues depending upon how you look at it. I personally question if whether or not the registries will make it mandatory for several reasons. The more horses registered, the more money the registries make, period. While I am in no way criticizing any registry or association and I have the utmost respect for the breeders who preserve the breed heritage and perpetuate the breed forward, I feel that as "fads" change over time and in an effort to keep up with the times some things change, and not always for the better. There was a time when (and still are breeders today) breeding primarily for size. I cannot tell you how many times I hear or read "to size the foals down" in an ad or during a sales pitch. Not everyone breeds for quality, many just for money. I assume that this is how the dwarfism gene has spread, breeding non ideal horses for size, inbreeding and irresponsible breeding. I like what someone else said about horses today being conformed so differently, and I think it is inextricably intertwined with the dwarfism trait. Today, Arab like horses win at halter, no one shows the "chunkier" minis of yesterday in halter. A while back, they were breeding for shorter horses like they are breeding for Arabian type ones today. How many have "Tiny Tim" in their pedigrees? That is a lot of horses possibly carrying dwarf genes. What sort of implications will the test have on the mini horse market now? Is the ability to test a positive thing for the registry to improve quality? Personally I think so, as I do not buy crooked or poorly conformed horses even if they have papers, and I would not buy a known dwarf producer/carrier for breeding either. What if a huge number of already registered horses test positive? What if the test is only mandatory for new registrations and through the results, registered stock gets exposed, will horse values plummet? I see SO MANY poor quality horses with A and R papers that in my opinion are not worth the paper the certificate is printed on, but the registries took the breeders money with no qualms. I feel that a certificate should imply quality and unfortunately, I fear that papers now a days do not guarantee that. Don't get me wrong, I know that there are many super high quality horses out there with papers, that have earned their places in the show ring, but I'll bet some of those horses would test positive for carrying the gene, even if they do not possess the characteristic phenotype for it. I fear that if a test is available and an extensive volume of horses test positive, then will the horse market flood and collapse further? Will a huge influx of minis get shipped off to slaughter? What will become of carrier horses? if not bred, they will make great performance or pet horses, but will their value decrease? Will they be "disposed of"? I feel that the mini breed is plagued with over breeding because so many people believe that you can't do much else with them (so not true) and in the breeding world the best horses show, win and breed to pass on their traits (ideally, doesn't mean this happens) but Will the exposure of dwarfism in the breed hurt the mini industry more than help it?

Will the registries make it mandatory, and risk losing revenue from registrations? I assume that the test is being developed for the main purpose of improving the quality of the breeding stock right? That is why scientists are trying to isolate gene markers for human genetic defects, to identity them, detect them, be warned about them and ideally eradicate them. After all no one wants to breed for dwarfs no more than parents want to have a child born with a genetic disorder that would make life difficult. (I am in no way starting an ethics debate or in any way claiming that the gene pool needs drained, I am not ranting about some whacked out sort or "cleansing mission" either) I am just saying that we know today that many human diseases that were unheard of 100 years ago have remained in existence because of advances in medical science that allow individuals with the trait to live longer, thus reproduce and carry the trait on. It is evolution of the species on an elementary level. Same holds true for minis. If the dwarf horses were not continuously bred, the trait would be much rarer, if not gone, but it was bred for, on purpose by some and unknowingly by others (in horses who carry but do not express the trait) never the less it is present in the breed and now what do you do? In the livestock world the aim should be to breed the BEST quality animal possible, but what is considered "best" as time goes on, the ideal horse changes. I personally feel that the ability to test would benefit breeders and improve the breed, which I strive to do in my breeding program, but what about the people who collect dwarf horses and put them on display and profit off of their "attraction" ? Will the ability to isolate and test for dwarfism create a clandestine following of dwarf breeders? There already are people who do this. Will people actually market known dwarf foals to make a quick buck?

People usually hear about, are interested in and remember negatives before positives. Will this exposure, obviously meant to improve the breed and educate people actually tarnish the miniature image in not only the equine world but to society? People are already misinformed. I get asked a lot at events "do you breed those little dwarf horses?" even though none of my minis have dwarf characteristics nor have I ever had a dwarf foal. People just associate all mini horses with "dwarf" because the word has been used in popular culture for so long, so will the exposure tarnish the breed as a whole before it improves it? If the test is available and affordable, I will certainly utilize it. I will use it to make better informed decisions about breeding and purchasing, I just hope others do as well, but I fear that some may not.

 

[rabbitsfizz]

Amysue you raise some good points in a very sensible manner but, in all honesty, I do not think you need to worry about any of it. There is NO way that any of this will become mandatory any time soon. Even if I were less cynical and thought everyone will want to test, it just would not be feasible. Just too many horses will have one half of the gene. We were told, when VwB (haemophilia) was first isolated in Dobes that so many were affected we would have to either close down the breed and start again or set a "clotting threshold" below which we did not breed and start from there. We chose the latter. Even now, thirty years or so later, we still have not eradicated it. We are two thirds the way there, I think, so long as we go on as we started and other countries are as scrupulous (the US was) VwB is a two sided gene like dwarfism, and the status on the pedigree forms is voluntary but it is one of the questions most asked now, just as "what is your horses HYPPD status" should be in QH!! I think anyone from the BH world would just be impressed that we cared enough to try, and there are always going to be dwarfs around, sadly, as there are thousands of unregistered horses just as there are thousands of unregistered Dobes!!

 

[horsehug]

Just some more thoughts of mine on this.

First let me say I am not against breeding non carriers to carriers once we are able to test and know what we are doing. The breeders I have talked to who have bred for years and in large numbers have told me they believe a recessive dwarf gene to be in 50% or more (possibly as much as 80%) of miniatures. And so I do believe carriers should still be allowed to be bred for their qualities that are good for the betterment of breed, when bred to non carriers.

However, for those who do not think carriers should be bred, I wonder if they are "For" the closing of the hardship registry for AMHA.

I personally have hardshipped in several horses over the years, and see it as a mistake.

And now in relation to dwarfism, I foresee people testing their minis, and finding that some that are unregistered or AMHR but not AMHA, are free of a dwarf mutation (non carriers) and yet now will be ineligible for hardship into AMHA.

If it were still open after this year we could be gradually adding more non carriers to the gene pool by hardshipping in non carriers.

In any event..... it will be interesting to see how this all plays out.

I still hope at some future meeting there will be a rule change to re-open the hardship registry.

Susan O.

 

[targetsmom]

Of course without a test no one can know how many carriers there are in the population but I think John estimated somewhere between 25 and 40% of all minis. At any rate, I agree with Horsehug that it sounds reasonable to breed carriers to non-carriers once they can be identified by testing. When pondering how many carriers there might be among minis, one of the things that struck me from John's thesis was the number of combinations that produced not live dwarfs but non-viable fetuses. How many times have we seen threads here on LB where someone says they thought the mare was bred but she must have slipped the foal, or certain mares that are hard to get in foal? Hello people!!! Some of those are very likely mares that are aborting non-viable dwarf fetuses!!! The way I read the thesis, if one of the pair contributed D1, and the other one contributed any of the 4 dwarf genes John studied, the mare will abort because the fetus will be non-viable. Did I read that right? And I am pretty sure these are early abortions, not late term.

One of my proposals - either here or on Facebook where another discussion was going about closing the AMHA registry - was that the registry should consider staying open to miniatures 34" and under with ASPC or AMHR papers who can prove they are NOT DWARF CARRIERS.

I think it will be quite interesting to see what happens once the test becomes available and perhaps we get a better estimate of how many dwarf carriers there really are.

 

[Arion Mgmt]

I want to clear up a few things some are confused about and to explain a few things I did not put in the thesis because it did not pertain to chondrodysplasia. Remeber it was my thesis on specifically the dwarfisms I worked on within the gene ACAN.

I dont remember who wrote specifically these misunderstandings but i will try to be short and simple to explain.

First there are other dwarfisms within the minis already known besides the ones within ACAN. Specifically the ones I breifly referred to as skeletal atavism currently being worked on in Sweden in collaboration with me. I supplied most of the dwarf samples for them. That allowed them to do a SNP test study on those. They are finalizing their results and I believe they found the cause. You can look in my bibliography and see. Also this type, the skeletal atavism type is the one some old US shetland breeders saw from some shetlands long ago (some old shetland breeders called them "midget ponies" they also called normal small shetlands midgets too), most likely those that came from Europe, since an unknown type of dwarfism was anecdotally known to exist in Europe. This is all speculation on my part, however look at the Fresian type and the skeletal atavism type, very similar. I talked directly to old shetland and mini breeders years ago when some were still here with us and got A LOT of information people would be shocked about. I cannot and will not discuss it due to my research confidentiality, but it helped IMMENSELY understand the trail of genetics, since pedigrees were worthless back then even some are today. Remember I started this seriously in 1993 in undergrad but had already talked with them to learn history of the breed in 1990.

THere are dwarf samples I have that do not have the four mutations I found, they have one of the mutations but not two of the same or combos... I am still working on a part of the gene that cannot be sequenced with todays technology due to its sequence characteristics, (read my chapter four). So I strongly feel there are more mutations within this gene that may cause another type.

As for the references on this mysterious Miniature dwarf type called Achondroplasia... It is a reference of INCORRECT ANECDOTAL NOMENCLATURE....used for years by some mini breeders that looked at the human Achondroplasia and just started using that term. Achondroplasia is caused by a mutation in the FGFR3 gene. The Miniatures were looked at back in 1995-96 here at UK by Dr. Cothran when I first got here and they did not have the mutation that caused Achondroplasia. I also looked at microsatellites surrounding the FGFR3 gene in the Minis and found no correlation with the dwarfs I have worked on. So Achondroplasia DOES NOT exist in the Minis.

As for the questions about prevelance within the breed....These four mutations ALONE....may VERY likely involve upwards of 40++% of the AMHA population. This does NOT include the dwarfs I have that have mutations I havent found NOR the dwarfs I have of skeletal atavism (different gene) and independent of ACAN. I have skeletal atavism dwarfs that ARE CARRYING in heterozygous form one of the four in ACAN. The only mutation found in the AMHR population I tested was D2 AND only 2 were carriers, and I have no idea where those samples came from, were they minis or mini/ponies or ponies....I honestly do not know, it was a true random test. but more need to be tested. But those 40 samples were MUCH lower than the 100 random samples I tested in AMHA. Hopefully, I will be more indepth at the AMHA Convention. I was not given any time by the AMHR ASPC registry for their convention here in Lex next month, so they might have to wait until next year to hear me.

 

[Tremor]

Personally, I think its going to be another 15-30 years before any of the registries add any admittance to dwarfism testing on papers. Its going to take time for the testing to get out, perfected, to get everybody to accept the testing, for laws, bi-laws to be approved, and the process for the testing to be put on papers. I bet A LOT of people won't be keen on testing, won't want it on papers, etc. I think there is going to be a lot of wasted time arguing about the laws around it.

I have said this before, I'll be testing. No worries on that! I'd love to and would be testing IMMEDIATELY!

On the topic of horses with Bonds Tiny Tim and carriers (since he was...ever so popular), I have a 2013 colt with Bonds Tiny Tim in his pedigree TWICE (8 generations back; half brother bred to half sister) and Komokos Little Husseler (TWICE. 7 and 8 generations back). It's obvious that physically, these stallions are much too far back to have any physically

affect on my colt, but genetically? We'll see once the testing comes out. SURE, he may NOT actually have any of these horses in his pedigree since there was a lot of name switching back then, but its the only information I have.

I have to say, look back at the OLD dwarfism discussions on this forum. Its quite fun and interesting. Here's one from 2007 that I've been reading.

http://www.miniaturehorsetalk.com/index.php?showtopic=85021&st=0

 

[Tremor]

Of course, I spend over an hour typing a response while I'm off doing other things and John Eberth posts.

If he posted more often I'd be yelling at him to quit posting and to get the tests out for commercial use.

 

[ohmt]

Thank you for the post, John!

Tremor-do you believe Komokos Little Husseler was a dwarf, or dwarf carrier? Just wondering, as I think I have read that the Eberths were fairly certain Komokos Little King Supreme was not a dwarf carrier based on number of offspring and mares crossed with, which would rule out Husseler as being a dwarf. The picture that is used for him is not very flattering, I definitely agree there.

 

[Tremor]

Thank you for the post, John!

Tremor-do you believe Komokos Little Husseler was a dwarf, or dwarf carrier? Just wondering, as I think I have read that the Eberths were fairly certain Komokos Little King Supreme was not a dwarf carrier based on number of offspring and mares crossed with, which would rule out Husseler as being a dwarf. The picture that is used for him is not very flattering, I definitely agree there.

I have no clue. Everything I knew about dwarfism and even my own horses is gone. Literally.
KLKS, was a heck of a nice horse and KLH produced some good and bad horses but the good had his eyes and dishy head (or so I've read). I have a 2013 colt with both in his pedigree and I'm just now doing research on them. I can certainly say I don't like the picture of KLH that I've seen, and I don't think KLKS was a carrier, which is great for me and my colt.

Ask me again on my view on dwarfism once the research and tests are out, because after the past couple weeks I am just...lost.

A friend asked me if I thought one of my mares was a carrier, and if her "dwarf" foal was in fact a dwarf or just exhibiting conformtional faults from both sire and dam. After extensively thinking about THAT foal, it just completely ruins my confidence in my knowledge. Do I think THAT foal in particular was a dwarf? (I don't own him anymore and he was gelded) Maybe not. Was his dam a carrier? Possibly not. Was his sire? I know that for a fact. So does this mean his full siblings are possible carriers? Not. A. Stinking. Clue.

(Foal in question was stocky at birth, cow hocked, had dam's domed head, constructed nostrils, roach back, pot belly...that the dam had as well. The dam was not a beauty queen in any way shape or form, and the sire had a long back and short neck. I had a full brother to this colt that had a slightly bad back, long back, short neck, and bad stifles. Was a good looking boy, and so were his other non-dwarf siblings. The "dwarf" colt now makes me question whether he just exbhited his dam and sires faults instead of resembling his sire like his siblings. It's not like I had decently conformed parents to begin with, I had horses with the same faults, and one with more severe ones. If they were World champions and perfect and this colt was born, I'd be running for the hills and gelding immediately. But this situation makes me doubt everything. This then extends to my 2010 filly in my avatar. It's a lot harder for me to distinguish between dwarf and a horse exhibiting a lengthy amount of bad conformation that has spanned multiple generations.

I wish I had all the answers. I could speculate and speculate, but when it comes down to it, I don't know a single thing about my own horses anymore.

I will say this, I have my suspicions about KLH, but I must ask this, How old was he in the pictures I've seen? Are their actual conformation pictures instead of front pictures? Is he the actual sire of KLKS?

Would KLKSs status as a non-dwarf carrier take KLHs running as a dwarf out of the system? Before Johns thesis came out I would have said it came down to percentages, but now I just don't know.

I wouldn't knock any horse with him in it.

The only thing I can say, is that I am a *wee* bit confident that my colt isn't a carrier after researching his pedigree and knowing the horses up close. But. I could be mindblown at any minutes.

 

[MiniNHF]

Tremor I send you a photo I had of KLH that I have for my boys pedigree and it is a side shot of him with his owner, not sure if you have seen those or not from the front/angled front shots of him that are out there.

 

[rabbitsfizz]

Thank you for taking the time to post that John, I find it very interesting that Achondroplasia- which is the term used here at the moment for the most common form of dwarfism in UKShets is a nomenclature. It is going to take me FOREVER to change my way of thinking on this subject- it is way, way more complicated than, I feel, anyone thought. Did you ever think, in 1990 that here, 23 years later, you would only just be starting to unravel the genetics?

 

[Tremor]

Has anybody donated samples to the research? I've dabbled with the idea before, but I'm not sure if it would be helpful at all?

I have three possible dwarves, a mare and her two offspring. I don't own the stallion anymore and can't get samples from him other than pictures and pedigrees.

I also have another mare who *may* have produced a dwarf, and her 2011 filly. The offspring are all sired by the same sire.

I can get pictures and pedigrees of all the horses and dwarves, but not blood samples since most are deceased or sold to new homes.

I would LOVE to send in blood samples/pictures/pedigrees, and I could have my vet pull blood next spring and send in the vials.

 

[Debby - LB]

Thank you John!

 

[Debby - LB]

Very good post Susan O

wow many good points and things to think about! To answer your question about the closing of the hardship registry, In light of this near future ability to test for this type of dwarfism, sorry I am NOT "For" the closing of the hardship registry for AMHA.

 

[ohmt]

Good post, Tremor-it's tough "knowing", isn't it? I will be so glad when we have tests for them all. Just the first 4 will be fantastic

Yes, I do think Husseler was King Supreme's sire. LK really liked their Komokos lines, the color and size fits, the pretty heads fit. Of course Husseler may have been a carrier, I don't know, but not a dwarf himself. He was thicker than what we're used to seeing nowadays (but not for back then), in pasture condition without being clipped and set up, and the picture was taken from above, so keep that in mind. I do wish I could go back in time and see these foundation horses in person!