Equine Dwarfisim (Friesians, Mini Horses, Mini Donkeys, Welsh)

EKW said:
Personally I think all equines born with dwarfism should be put down at birth or at weaning if the mare is particularly stressy. It should not be encouraged nor should a pony with dwarfism be bred from.


A few years ago a dwarf Shetland was shown and when the judge placed it last and explained why the owner went off her rocker and said that it had the best breeding of the whole class. Be that is as it may but a dwarf is still a dwarf.
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Back in the day, a dwarf miniature was winning massive championships because of his size. Conformation made no difference to the judge. I don't think you would get away with it now haha or at least i hope not. Minis are no longer about size, but about proportion. No point having a 29" that looks like a pig win over a 34" that looks like a horse through a telescope backwards.
 
At the moment i think it is more carriers being bred because the owners don't know they are carriers, or chance they their luck (but the test was only made available in early 2014)

If they get a dwarf, it will either be pts or sold as a novelty/used as a novelty horse.
 
equi said:
At the moment i think it is more carriers being bred because the owners don't know they are carriers, or chance they their luck (but the test was only made available in early 2014)

If they get a dwarf, it will either be pts or sold as a novelty/used as a novelty horse.
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At which point you would test both parents and stop using the one that carries the gene. Even if it is only a 5% chance of getting a dwarf that's still 5% too many in my books.
 
But the problem is that is as the gene is recessive you can't see it. It's not just a case of not breeding from a horse that looks like a dwarf but also not breeding from any mare and gelding stallions that have produced a dwarf as that means both parents are carriers.

If there is now an accurate test now then there is the option of not breeding from a horse that carries the gene.

However I suspect some breeders might still breed from a horse carrying the gene if it had been successful in the show ring but make sure that the other parent does not. So while they would not produce a dwarf they would have a 50% chance of producing carriers.

ETA I read an article ages ago that some successful miniature sires are known to be carriers but are still bred from as they are successful and if not a dwarf their progeny is what is wanted.
 
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EKW said:
At which point you would test both parents and stop using the one that carries the gene. Even if it is only a 5% chance of getting a dwarf that's still 5% too many in my books.
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With the gene how it is, if either carrier has the gene it is a 50% chance of passing it to the offspring. The only way is to breed any with the gene to a NON carrier, test the foal and continue and eventually have non carriers. If the thread is correct, over 50% minis have the gene and if we cull 50% of miniatures there will not be any left and they will start inbreeding again and be back to square one.
 
equi said:
With the gene how it is, if either carrier has the gene it is a 50% chance of passing it to the offspring. The only way is to breed any with the gene to a NON carrier, test the foal and continue and eventually have non carriers. If the thread is correct, over 50% minis have the gene and if we cull 50% of miniatures there will not be any left and they will start inbreeding again and be back to square one.
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I think that is a sacrifice that any ethical breeder would make. (I mean cull as in remove from breeding programmes)

If it was my decision, I would look at the long term. I would introduce something hardy and with diverse bloodlines (Welsh section A would be the obvious choice) with the thought of producing a healthy horse in 100 years, rather than a small horse in 10.

This is why syringomyelia etc is so prevalent. It all down to an attempt to change a breed's morphology in a short space of time. (also the focus on appearance over utility is a huge contributor, but that is a whole other argument)
 
There are some perfectly fine non-carrying miniatures, so they don't need to all be culled and introduce others (welshes also have dwarfism so might not be the best choice). Just need to make sure two carriers are never bred from together, and eventually it will breed out. People know more about it now, and thus can make more informed decisions. There will always be dwarves, cause there will always be people who don't care what they breed.
 
equi said:
At the moment i think it is more carriers being bred because the owners don't know they are carriers, or chance they their luck (but the test was only made available in early 2014)

If they get a dwarf, it will either be pts or sold as a novelty/used as a novelty horse.
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At which point you would test both parents and stop using the one that carries the gene. Even if it is only a 5% chance of getting a dwarf that's still 5% too many in my books.
 
equi said:
http://www2.ca.uky.edu/gluck/AGTRL.asp#Dwarfism
This is the one for minis, but i'm sure they would do other breeds too. There is a mini breeder in the netherlands who has all his stock done, so i wonder if they do it there rather than USA (its much cheaper! in netherlands!)

Tests only started in 2014...so its still very new. I suspect that soon, some of the UK labs will start it.
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Different loci for some of the different breeds so unless other labs are able to do the same test under licence it is likely too soon for others to be able to reverse engineer it if that makes sense - molecular genetics can be tricky!

I am not sure about breeding from carriers, yes in theory if you breed a carrier to a non carrier but the USA should have bred out HYPP years ago by doing the same but many breed two n/h horses together hoping they will get the % that isn't h/h and affected and essentially allowing the gene to perpetuate because n/h horses can still be registered. Hopefully mini breeders are more responsible but :p.
 
equi said:
There are some perfectly fine non-carrying miniatures, so they don't need to all be culled and introduce others (welshes also have dwarfism so might not be the best choice). Just need to make sure two carriers are never bred from together, and eventually it will breed out. People know more about it now, and thus can make more informed decisions. There will always be dwarves, cause there will always be people who don't care what they breed.
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Most breeds have occurrences of dwarfism but there are not so many that would knowingly breed a carrier.
 
ester said:
Different loci for some of the different breeds so unless other labs are able to do the same test under licence it is likely too soon for others to be able to reverse engineer it if that makes sense - molecular genetics can be tricky!

I am not sure about breeding from carriers, yes in theory if you breed a carrier to a non carrier but the USA should have bred out HYPP years ago by doing the same but many breed two n/h horses together hoping they will get the % that isn't h/h and affected and essentially allowing the gene to perpetuate because n/h horses can still be registered. Hopefully mini breeders are more responsible but :p.
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I'm trying to find out myself :p i have to admit i didn't look into it that much before this. I knew bits and pieces, but not the full story.
 
Pigeon said:
Most breeds have occurrences of dwarfism but there are not so many that would knowingly breed a carrier.
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Very true, but i don't think it is ever going to happen that over 50% of breeding stock are going to be culled. I have heard that it is creeping up in friesians again due to a demand in them, and thus breeding of unreg stock.

AMHA are a closed book now as are BMHS so hopefully they maybe take this under their wings and request dna for the breeding stock? I don't know if that can happen or not.
 
They should do that, IMO for a time they should allow carriers to be registered as it also wouldn't be good to shrink the gene pool too quickly unnecessarily but it should then change that either only negatives can be registered or that carriers can be shown but their progeny not registered, that sort of thing anyway!
 
Just musing but I wonder if a single copy of the gene makes any difference to the appearance of a carrier.

From the linked article

"miniature horses who are Skeletal Atavism carriers tend to have more 'horse-like' heads. Others have noticed smaller ears are also present in their carrier stock.".

Now they say this may not be linked but it just got me thinking that with miniature horses at least what if there are certain physical attributes (even size) associated with being a carrier and these are ones that are desirable then there is a danger that carriers will be bred from.
 
As its a recessive gene there should not be any but it is a fact that some dwarf horses were bred because of their size. So attributes of that horse may come through, despite the horse not being genetically a dwarf itself.
 
criso I do think it is possible and it might not be an absolute recessive depending on the circumstances/expression of it and other genes. It might become clearer once there is a stock of known carriers to analyse traits on.
 
Thing is some traits (domed head, small ears, dished face) are being bred for and may not necessarily be a trait of dwarfism but just what's being bred. However how many of these "Arab" types are carriers or not would be very interesting to know.
 
equi said:
With the gene how it is, if either carrier has the gene it is a 50% chance of passing it to the offspring. The only way is to breed any with the gene to a NON carrier, test the foal and continue and eventually have non carriers. If the thread is correct, over 50% minis have the gene and if we cull 50% of miniatures there will not be any left and they will start inbreeding again and be back to square one.
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I agree with Equi.

Personally, I think that it would be a bad idea to ban all dwarf gene carriers from breeding, because there is no current test (as far as I know) which shows that all the other genes the tested horse is carrying, is 100% healthy.

Hypothetically, let us say that 50% of horses in a specific breed is dwarf gene carriers, and they become banned from breeding tomorrow. But then some years from now, it turns out that some of the supposedly healthy horses, are in fact carriers of some other (currently unknown) unwanted gene, which earlier had gone undetected because of the larger amount of possible breeding animals. What are they going to do then, narrow down the potential gene pool even further, by eliminating them as well?

I think that there will probably always be some idiot somewhere, who does what they want to, but the most sensible option to me, is the one where either the stallion or the brood mare, must be a non-carrier of dwarf genes. That way, the gene pool isn't narrowed down too much.
 
The carrier stallion on the stud I used to work for was a lovely pony. He was one of the nicest, most correct stallions she had and passed his Shetland test with flying colours (and they are *strict*). Moved beautifully, lovely conformation, very trainable, was in full work. You really wouldn't have known that he was carrying anything untoward. It was only when some of his offspring turned out to have short bent legs and other defects that it became clear that something was amiss. However, his non-dwarf offspring were just as correct as he was.
 
What worries me most is the fact that so many people viewing this advert will say 'awww, how cute' whereas I guess most horsey people cringed. I certainly did. I can see a wave of folk wanting cute lil ponios..........and that is not good.
 
One of our shetlands (std, registered, show quality) had a dwarf foal in the 70's.
Was mares 1st foal from our stallion. Stallion already had 100% live normal foals and almost all took their colour from dam.
We never put the mare in foal again, foal lived till 3yrs old - happily and healthily - but a hefty dollop of flu that was sweeping the SE at the time saw her off very quickly. Heart beat was irregular when under stress & vet opined that this gave out before he could PTS.
We traced mares breeding (already had her mother who my mother had had 4 foals from) and not a single issue raised over 5 generations or more back.

The odd one can just 'happen'. This one stood right out as the smallest we had at that time was 36'' with most around 39/40 ins.
 
It's not that the odd one just happens but being a recessive gene you need both parents to carry it. If it is relatively rare in the population then the chances of the two meeting ans being bred is unlikely.

In some populations like in friesans where the population went down to few individuals or miniatures where dwarves were bred from way back so it is more likely to be an issue.

We have examples above both stallions mentioned would have been carriers as well as the mares they were put to to when a dwarf appeared so statistically 50% of their offspring would be carriers. If they are lovely correct individuals, then there will be demand and the gene gets passed through the population.

It can be difficult if there is a very small genepool to choose from but breeders do have to think of the consequences further down the line of using either mare or stallion if a dwarf has been produced.
 
The other thing with minis is that the dwarf gene gives "false" smallness. Any non-dwarf foals from the pairing will be a few inches larger (ie their actual genetic size), so regardless of any ethical considerations, it doesn't make good breeding sense if your aim is to breed consistently small ponies.

The smallest lines that my old boss used to breed had not a hint of dwarfism. The stallion I referred to earlier was about 32", if I remember correctly, so not really tiny.
 
My friend breeds as small as 29" and has never had a dwarf from the mare/stallion and offspring are all very correct and no hints of anything untoward. I think there is a fair bit of inbreeding in American lines more so than British lines because America is just too vast to cover mares whereas uk/ireland is more obtainable. AI is very rare in miniatures.
 
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