Regarding the possible future DNA testing for Chondrodysplasia-like Dwarfism

[Debby - LB]

To not take away from Arion Mgmt - Mr. John Eberths wonderful announcement I want to start a new post about what this possible test will mean to the Miniature Horses industry in the future and how some of you will deal with it. Please excuse this being long and excuse my grammar.

in that thread found here targetsmom posted: (hope you don't mind me quoting you Mary)

Thank you so much for pinning this! I hope more people get to see it and realize the implications to the miniature horse industry. Now, my wish is that with the Lupton's instigating the change to the AMHA rules so that color test results can (but are NOT REQUIRED TO) be added to the registration certificate that it will be an easy change to just VOLUNTARILY add dwarfism test results. If this is done along with DNA testing there should be no question of identity. The horses who test test negative can be advertised as such and we will likely see their value increase. Then all you need to do to assure no more dwarfs in your herd is to test and not breed two carriers (of the same gene) together. Just the same way we avoid Lethal White foals - which isn't by getting rid of all the carriers.

________________________________________

I agree!! It is my hope that eventually this will be mandatory testing for breeding stock but I know that would be way in the future.

This is something that has been on my mind for months now since I got caught up in the middle of the blow up in the miniature longhorn cattle industry. At the time all I could think of was OMG this would be a major impact on the Miniature Horse industry and I hope and pray the breeders there don't act this way!!

The miniature Texas longhorns were supposed to be pure and bred down but upon DNA testing for Chondrodysplasia (Dexter bulldog gene) it was found that many people who claimed pure breeding actually used Dexters or known Dexters to bring the size down... thus introducing the dexter bulldog gene . Some used Zebu but that's another story and as far as I know didn't cause any genetic dwarfism issues.

The only way you could get the Bulldog Chondrodysplasia dwarfism gene in a Texas Longhorn was if it was not pure. (for the cattle the test for Chondrodysplasia has been available since 2009 -2010) So needless to say their Mini Texas Longhorn registries were worthless unless you came clean with your tested cattle and only registered them as their policy stated. Well... I'm sure you can see where this is going, most knew the bloodlines, they had to know some of theirs were not pure. The registries were built on this and the gene was in most if not all the breeding stock.

I felt really bad for the people who invested their time and money but I couldn't believe the things I was told by some who tried to justify this happening! I guess when people are in this position they want to believe what they are told. I was informed, among other things, that the cattle were pure, not crossed with Dexter and anyone could have this type of dwarf born..... because of a parasite.

To quote Mary again: The horses who test negative can be advertised as such and we will likely see their value increase. Then all you need to do to assure no more dwarfs in your herd is to test and not breed two carriers (of the same gene) together. Just the same way we avoid Lethal White foals - which isn't by getting rid of all the carriers.

This is similar to what I told the few breeders who asked me back then what I thought would be the outcome of a test like this for our horses. This is what I told them:

If a test came out for mini horses it would be wonderful in the long run but the chaos it would bring would take a while to recover from. On the other hand there is no doubt what-so-ever in my mind that there would be a HUGE market for N/N results and people who have them could name their prices.
Some farms would test and never tell the results or lie about them just like your breeders are doing now. Money is a big motivator so admitting their stallions should be gelded and mares retired will be a hard pill to swallow. Being able to advertise dwarfism free stock would be a HUGE HUGE boon to the mini horse industry....IF testing is embraced and the registries promote it.

I know that unlike the cow info. in this post most mini people already know that dwarfism is in the Miniature Horse so this is some what different but do you foresee some of the same problems with misinformation and misrepresenting happening? Do you see the implications to the miniature horse industry?... pros ? cons ? how would this relate to the future close of hardshipping? Do you think we as owners/breeders will embrace the testing and use it, or maybe use it and continue to hide the results? Will you personally test and post results?

 

[targetsmom]

I don't mind at all that you quote my thread - quite the opposite, as I am glad to see this topic raised.

I think one of the issues is that the farms (estimates on here of >40% of farms when I did a poll in 2007) that have had a dwarf foal or fetus KNOW they have minis that will test positive. Those breeders may be concerned about how the test might be used (they see the glass as half empty). I see it the other way around - my glass is half full as I see the potential for promoting those minis that test negative (N/N).

I do not agree that stallions that test positive should be gelded or that mares should be removed from the gene pool. I think that is the reason breeders are concerned about the test. I think if test results are used properly so that positives are not bred to positives, just like we do to prevent Lethal White Foals - you will at least prevent more dwarf foals from being produced. Of course you will still have the dwarf gene in the population but until we have a better idea of how many horses carry dwarfism, I think it is premature to decide their fate. Think about some of the horses in the past that might have been removed from the gene pool if the test had been available 20 or even 10 years ago.

As for those stallions (especially) that test positive, breeders can and will likely keep quiet about them, but silence will speak volumes!

 

[user 488]

I think if test results are used properly so that positives are not bred to positives, just like we do to prevent Lethal White Foals - you will at least prevent more dwarf foals from being produced. Of course you will still have the dwarf gene in the population but until we have a better idea of how many horses carry dwarfism, I think it is premature to decide their fate. Think about some of the horses in the past that might have been removed from the gene pool if the test had been available 20 or even 10 years ago.

As for those stallions (especially) that test positive, breeders can and will likely keep quiet about them, but silence will speak volumes!

Exactly! You just have to educate yourselves. KNOW what you are breeding!

 

[Tremor]

From the way I understood the paper, it will be a lot more complicated than just breeding carriers of different types. There are multiple types of dwarfism on one location AND they can carry multiple types.

Its going to be a lot more difficult, and lets also realize that they haven't even located where Achondroplasia is. We still have to worry about that.

EDIT: I will admit that the test will make a huge impact on the industry and I'll be testing all of my horses for the genes when the tests are released.

 

[Debby - LB]

I agree but to my way of thinking what you describe is how responsible breeders were and are already handling it. All these years it has been the only way we could.

For me personally once I knew I could buy a horse that was tested as clean I'd never breed known carriers or buy non tested again at all. To know positively which ones carry is a whole new ball game and time to cull.

I do agree that until we have a idea how many horses carry dwarfism, it is premature to decide their fate. It will be interesting for sure to see how many people test and see it as a boon to the industry.

*note I no longer breed anything so just my little opinion here hoping I don't step on anyone's toes.

 

[wingnut]

Good breeders will do right by their horses. People who breed to make a quick buck? They will do whatever it takes to continue their efforts in this regard. It's human nature. I wish it weren't so. Should I be in the market for another horse after a test were to become available, I will definitely be working with those farms who have had the testing done and can show me the results. That's what an educated buyer should do. The education has to be on both sides of the coin.

 

[Minimor]

I breed a Mini foal here & there, or have done up until now--not really planning to have any more after 2014--but once the test is available, I wouldn't breed again without first testing the horses I intend to breed. If either stallion or mares prove to have a dwarf gene, the positive horse(s) would not be bred. I do not see the need to breed a carrier, even to a non-carrier; at least it is not what I want to do--not when I can know one way or the other by testing. If I were to buy another Mini mare or stallion I would want to see a negative test before I paid any money. Obviously in a gelding it wouldn't matter, as long as I like the horse's conformation it wouldn't matter what might be hiding in his genetic makeup. If he is carrying a dwarf gene it's not going to pop up and bite me somewhere down the line.

 

[BSharpRanch]

I cannot view the article so am not educated on what this test will test for. Is it for ALL types of dwarfism or just one or two types? If it is just for one or two types, that would mean that even though your horse tested negative, it still MAY carry the other types of dwarfism so by saying "dwarf free" it could be very misleading that there is not ANY dwarf genes at all in your horses which may or may not be totally true without being able to test for ALL types of dwarfism. But like I said, I am unable to access the article so I may be way off base.

 

[ohmt]

BSharp-the tests are for all but the achondroplasia, which is located in a different area in the genome so hasn't yet been isolated. There are still the 4, not including the mixing of them so it would eliminate most worry for breeders.

 

[BSharpRanch]

Okay. I cannot access the article, so by the title figured it was just one kind. Cool.

 

[rabbitsfizz]

Skipped to the end, sorry.

For me this is a no brainer. The AMHA should add a box, as they should have done years and years ago for the colour pheno/geno type. The box should merely say "DNA tested N/N N/C (carrier) for dwarfism C1 (or whatever they decide to call it) Thus, as with HYPPD, you can choose to advertise if your horse is tested or not. I actually think, with something as important as this, it should be compulsory from the moment the test is proven, but I KNOW that is never going to happen so there is no point in even suggesting it. I doubt very much if even the innocuous box for proudly declaring your horses proven status will appear as I am a cynic and have watched just how long it is taking the QH people to remove their heads from- OK you can say the sand if you wish!!

They still accept N/H horses for breeding and people can still breed N/H to N/H- now how long has that test been out?

The dwarf test and all John's work is invaluable and we all thank him- all us sensible ones, that is, all the people who will take advantage of the test (even if it came years too late for D.C's testicles!!!) as soon as it is available. As for the rest? I do not think it will even stir the surface of the pot, quite frankly. When you have something that is not visible, as with a single dwarf gene, or, as I found in Dobes VwB (Haemophilia) people can just ignore it and go on happily throwing out their trash. Until the relevant societies take a stand (as our Dobe society in the UK did almost immediately) and start publishing the status of the animal and demanding testing (VwD will not show until relative maturity, although two unaffected parents cannot throw and affected pup) then the "top" people, on whose livelihood this depends, will do nothing at all and go on spreading the hype that, as thier horse is perfect it cannot be affected.

Cynical, moi??

Yes, after fifty years I am afraid I am, just a little!

 

[Debby - LB]

gotta agree Jane. Like was said before though about those who may not test or those who do test but try to hide it..silence will tell. So far every one of the people I've spoken with about this in the last 6 months say they would want a N/N test if and when it's available.

I don't breed anymore but I will test my 2 girls that I couldn't part with and their status will be available. It will be interesting to see their results and to hear the results of others as we watch the gene or genes gather in certain or all bloodlines.

To answer the anonymous person who emailed me wanting to know why I thought it my business to know the DNA status of anyone's herd since I don't breed minis.... for years now I do help people find horses to purchase so DNA for parent qualifying, color, or possible dwarfism... which at this time my only available option was to research through pedigree and searching online with photos and message boards... will still be my business. The new testing - If and when available - will make it way easier.

 

[Minimor]

I do think it is going to be a big selling point to advertise negative test results. Depending on how many negative horses are available there may still be a market for the carriers, but I don't see people having a great deal of success in selling horses that don't have test results available. Informed buyers are going to want to know what they are buying.

I don't know if I will test my non-breeding horses--that will depend on cost and if I have the $$ to spare--they are driving horses or pets, their status doesn't really matter except for the sake of interest. As I said earlier, if I'm going to breed anyone then those horses will be tested, and any mares being advertised for sale will be tested with their results available. (I won't be selling any stallions.) Geldings--again, I don't see it mattering except for the sake of interest, but if anyone wanted a test on a gelding I was selling then I would certainly do one.

 

[Tremor]

When the test is released, I'll be testing all my minis from my ex broodmares to my dwarf gelding. They may not be breeding, but I want to know out of curiosity.

 

[Margo_C-T]

I no longer breed miniatures, and no longer have breeding age mares, nor any stallions...but when I did, and had one dwarf born, I completely removed sire and dam from my breeding program,giving both to a boys/girls' ranch who didn't 'do' breeding,along w/ a normal filly by the stallion....all with full disclosure...admittedly, I later wished I had had the stallion gelded before gifting him; spaying the mare, while a good idea, would have been more than I could have afforded. I kept nothing by or out of either of the pair who produced the dwarf.

I kept a son of my personal favorite 'outside' stallion; later, 'someone' emailed to say they'd owned that stallion's dam and she had produced a dwarf for them. to this day, I'm not sure whether I believe it, as I had stated my personal beliefs about never again breeding anything that produced a dwarf, and suspect the person in question has and continues to breed, for sale of the offspring, dwarf producers-and may just have resented my strong stance??? In any case, my horse was gelded after siring only a few foals---all normal and of excellent conformation quality...and he is STILL my favorite mini I bred/raised.

All this said, I have looked forward to the day there was a reliable test, and am thrilled beyond description by John's work and emerging results! Were I still breeding, I would absolutely be testing ALL breeding stock, with the results open to examination.

I agree w/ Rabbitsfizz on most points...including about the AQHA (cannot begin to express how I've lost respect for them as a result of their lack of proper action on genetic issues--(just TODAY, I saw a online ad for an APHA mare, with BRAGS about her N/H sire!!)And, I also believe that the sad truth is that too many miniature horse buyers are uneducated/naive, and will continue to be preyed upon by unscrupulous breeders because they do not/will not 'do their homework FIRST, so it will take a LONG time, if ever, before the issue is truly addressed in a comprehensive way.It will be a BIG step in the right direction, though, to have the test available, and I hope it will be widely and completely utilized!

 

[susanne]

.

To the person who sent that email to Deb:

We may not all breed, but we are your potential customers, so YES, IT IS OUR BUSINESS.

Once the test is available, many will choose to buy only those horses that test negative, whether they plan to breed or not.

Unfortunately, too few breeders have the integrity to rid the miniature horse world of the dwarf gene. Breeding those that are positive, even to horses that are negative, will only serve to perpetuate the dwarf gene and allow it to rear its ugly head in the future.

Between the closed minded reactions of some breeders to the ramification of this test and the idiocy of both registries closing and thereby limiting the gene pool...do I see another miniature horse registry forming in the future? Ah...I can only hope!

 

[Charlotte]

I have a question. I assume the feeling that AMHA should have testing for dwarfism be mandatory includes AMHR? So having said that, Everyone says miniatures come from Shetlands, so why not start at the root of the problem and have ASPC require testing? Wouldn't that be the place to start? As soon as the shetland lines that were carriers were known then miniature owners would have some idea of where to start testing instead of feeling so overwhelmed with horses to test. Maybe if this were done then people would be more willing to test.

Oh, just on the same subject, I have been meaning to mention this for a long time and I keep forgetting. At the last Annual Meeting where John came and did a presentation on his research Frank asked him a question regarding the prevalence of dwarfs in the miniature breed now as compared to 20 years ago, 15, 10 etc. I don't remember the exact wording of the conversation, but John agreed that the number of dwarfs being produced had dropped substantially from early years. So I think we can all be comforted to know that for the most part breeders are policing themselves and that characteristic is being bred out for all practical purposes.

 

[Becky]

In my observation since I purchased my first miniature horses in 1989, serious, committed breeders are breeding out undesired characteristics. I see way fewer miniature horses with dwarf like features now than I did back in the 1990's. So, there is self-limiting going on which is a great thing. Testing for dwarfism should be all inclusive of every breed that miniatures horses are derived from.

 

[Minimor]

Charlotte--it is very doubtful that there is dwarfism in today's ASPC ponies. Just because the Miniatures originated with Shetlands does not mean than Miniatures are 100% Shetland, and it doesn't mean that the dwarfism mutation originated in the Shetland. John's article says that it is a fairly new mutation... In any case--if there were some dwarfs showing up in ASPC ponies in the 60's and 70's, those dwarfs would not have been desirable in any Shetland breeding program. For one thing, Shetlands have always been judged on movement, and a dwarf is not going to be able to move. Any self respecting Shetland breeder would have ditched any dwarf and quite likely the parents of any dwarf. If there were any ASPC dwarfs (and I don't know that there were, but cannot say there were not) it is almost certain that owners did not revalidate the papers on those dwarfs. If the papers were not revalidated when revalidation was necessary, those ponies were no longer included in the Shetland registry. Any dwarf Shetlands were almost certainly dropped from ASPC and then went on to become part of the foundation of the Miniatures.

I for one would be extremely surprised if any of todays ASPC ponies were to test positive for dwarfism. From everything I've read--I think John Eberth would be too.

There is little point in demanding that Shetlands be tested for dwarfism when it is the Minis that have been producing the dwarfs.

 

[targetsmom]

This is a quote from page 32 of John's thesis: "AMHR horses have a much less incidence of carriers of dwarf alleles
compared to the AMHA population". And if I read the thesis right, John feels that there are even fewer dwarfs in Shetlands - that the mutation is new and not from the Shetland blood.

So I agree with Minimor - not much point in requiring Shetlands to be tested.

But one thing I have not seen discussed is the number of dwarfs that are not viable and result in early abortions. It looks like about half of the possible combinations that produce dwarfism are not viable so could be the reason a miniature mare "slips a foal" or comes back in heat. And of course even breeding two carriers together will not always produce a dwarf. So while some breeders might be aware they have carriers because of actual dwarfs being produced, the chances of breeders being fully aware of all carriers without a test seems pretty unlikely.

I would also like to comment on Susanne's statement "too few breeders have the integrity to rid the miniature horse world of the dwarf gene. Breeding those that are positive, even to horses that are negative, will only serve to perpetuate the dwarf gene and allow it to rear its ugly head in the future." Let's present a hypothetical of the breeder with a stallion (and a mare too of course, because it takes two) that produce a dwarf so he knows they are carriers. The consensus seems to be that you geld the stallion and never breed the mare in order to help remove the dwarf gene from the gene pool. Does that mean that you stop breeding? Because at the present time, without a test, how will you find another stallion (or mare) that you can be sure is not a carrier? Remember that poll I did a few years ago on here where over 40% of breeding farms anonymously reported a dwarf foal or fetus? And what if this same stallion is himself or is producing World Champion horses? Don't say it doesn't happen because I am pretty sure it does (or did)....