Identical Twin Horses?

[JOJOBA]

I meant to post this ages ago...

Recently I was out and about (in the non-horsey world), and I passed a group of horses hacking (it was miles from anywhere so I cant think where they came from, but that's a different story :p).
I noticed that the last two horses of the four were identical.
Now I mean actually identical, Ive known hundreds of horses and although I often see horses that are very similar, Ive never seen identical ones before.
They were exactly the same height, and chestnut. They were the exact same build (they looked like welshies) and each had an identical white hind sock. They both had large blazes which sloped over their eyes in the exact same pattern. It really was just one horse in duplicate. Also they were both rather small and weak looking, even though the horses they were with were healthy and well cared for, which made me think they could be twins.

Now Ive heard of equine twins and know they are rather rare, especially if they both survive - but what about identical ones?

xxx

[Yann]

Don't know about the reproductive process in horses but as mammals that normally carry a single offspring like us I daresay identical twins are a possibility.

Rio's old owner told us that she had twins as a broodmare and they lived, who knows, the ones you saw could have been hers?:D

[Esther.D]

I believe they are physically possible but it is rare both survive. I do know quite a lot of pretty identical ponies - much in demand in the driving world for pairs. Some of the pairs are so similar you would think they are twins but are in fact often full brothers/sisters from a sire who throws very consistent offspring

[Humbole]

At my yard 3 of us have *almost* identical dark bay TBs (totally unrelated). They are so alike all of us at some point have gone to catch the wrong horse :o . We can tell them apart up close, but to save confusion we've now got them in seperate fields!

[JOJOBA]

Ive seen very similar horses before, but seriously these were completely identical!

Yann - have you ever thought about finding any of Rio's foals? Just thought it could be interesting! :)

xxx

[Yann]

I'd love to but wouldn't have a clue where to begin looking, she's not papered and I doubt any babies would have been either. I'm afraid if I met one and it was anything like her then I'd want to buy it too:D

Quite surprising that anyone would want to use her as a broodmare when she's made such a fantastic riding horse, she wasn't backed till the age of 7.

[Pink's lady]

I know of identical twins (though I never met them myself). My friend went on a riding holiday, and they had a set of twins there.

And they were coloured and had EXACTLY the same markings. My friend (who is knowledgeable of horses) said there was no way you could tell them apart, except in personality (one was a bit no out-going).

One of them had his mane hogged, except apparently it was allowed to grow back, and the next time , the other one got done, which confused people even more! :D

[shandy84]

There are ponies by Bramble's sire that are identical to her in every way, it's meant to be a gene thing apprently :rolleyes: so althought I have heard of twins unless you know the bloodlines it is possible they are unrelated or related a different way

[chev]

I knew a pair of what the vet believed were identical twins. They actually had different markings - similar to the cloned foals (which are genetically the same horse, if that makes sense) that had very different markings when born. It's believed that white markings are not just the result of genetics but also environmental factors while the foal is still in the womb - pressure on the unborn foal and that kind of thing. So identical twins are no more likely to have identical markings than any other siblings, although that kind of identical type of marking does crop up (and sometimes in horses that are unrelated too).

As far as I'm aware though twins in horses are usually non-identical - the result of two ova being released and fertilised at the same time, rather than one later splitting and becoming two foals. The case I knew was scanned as one embryo but turned out to be two foals, which led the vet to believe that the this had split and was therefore identical twins. Twins in horses are relatively rare (maybe less so now as we use drugs to encourage fertility and conception) and apart from that one I've only ever heard of non-identical twins. Most non-identical twins are resorbed by the mare, so I imagine that identical twins are even less likely to develop in the first place, or to survive if they did.

Either way - identical markings in horses are actually far more likely to be coincidence than genetics, as proven by the breeding experiments (especially those using cloning technology).

Edit cos I found my statistics again!

Twin pregnancies occur in about 1 - 2% of all TB pregnancies. The majority of these result in either natural embryo reduction (resorption) or later abortion. 93% of these twin pregnancies are non-identical twins - they correlate to the number of ovulations detected by scanning. In other words, 93 in every 100 of these twins were shown to be producing more than one egg before covering.

So.... at most, 2% of mares conceive twins. Fewer actually produce twins. Of that 2%, only 3% are identical twins. Even fewer of these are catually born.

Figures for TB breeding are much higher than natives breeds, so the incidence of identical twins in non-TB mares is going to be even less. They are very rare!