Height question

[carrie17491]

Just a discussion I'm having at the minute.

If a mare standing at 14hh with history of the similar height was put to a stallion of 16.2 with big heights in his breeding, how big would the foal be expected to make?

[sarahp]

Anywhere in between but most likely not outside those heights! You normally hope for the average of the two, ie in this case 15.1hh but a small mare may have a smaller than expected foal on the grounds of being able to carry it OK - nature's a wonderful thing and does compensate.

I bred two welsh PB foals from a 14.1hh D mare by a 16hh neat AES stallion with lots of TB in his pedigree - one was a whisker under 16hh - and her first foal too - and the other a 14.2hh jumping pony.

[Guestless]

Dec 21, 2012 9:35:09 GMT sarahp said:

a small mare may have a smaller than expected foal on the grounds of being able to carry it OK - nature's a wonderful thing and does compensate.

Sometimes. I have witnessed a mare losing a foal during its birth because it was too big for her - she was a friend's mare and had been unknowingly pregnant when bought from a dealer.

I would never take the risk of covering with anything too big - IMO breeding is risky enough without increasing the odds of something going wrong. My own vet (reproduction specialists who do everything from AI to embryo transfer) recommends nothing more than a hand bigger than the mare.

[sarahp]

Of course not every time, but much more often than not - experiments have been done on sizes of foals at birth and mature heights of heavy horse x Shetlands, both ways round (conceived by AI!).

The build of the respective parents matters a lot too, it's about more than height. My wide D mare was fine with her two by the neat TB type 16hh but I'd never dream of putting say a 16hh trad on a 14.1hh Riding Pony, that would be asking for trouble.

We don't know of course if the OP is thinking of doing this mating, or expecting a foal already from those two parents, or what types they both are either.

[pattendown]

isnt that considered abuse to ai a shetland mare with a heavy horse knowing that the mare can be torn apart with the growing foal of the foal cannot go past the pelvis and has to be cut into pieces to remove it from a very destressed mare ,i for one would never take the risk ,in this day and age with the over breeding and eveything why is it needed anyway

[sarahp]

This wasn't private breeding but a properly conducted scientific experiment, and may be some time ago now, I can't remember the date of the paper. I quoted it to back up my statement on sizes of foals two posts above being affected by the size of the mare. I can't believe anyone would do it as a serious breeding project.

[lils]

I do recall when doing AI Training with Jos Motterhead him saying something similar along the lines of what SarahP is saying.

[sarahp]

Thanks!

[dazycutter]

Even if it was a scientific experiment, that is outrageous. So does it make it ok if it falls under the banner of research? Thank goodness for human research there is ICH GCP and the deceleration of Helsinki.

[sarahp]

Don't shoot the messenger, it wasn't me that did it! I was just reporting. And the point was to increase knowledge and so save suffering in the future don't forget.

[dazycutter]

Not shooting the messenger at all, just amazed that in the name of research they would do that. I am sure before they carried out this research they knew what the outcome would be. Out of interest what happened to the little mare and foal?

[sarahp]

Well after Christmas when time I'll try to find the original research paper and put a link up.

[swilliam]

Gojng back to the original question, I've got a 14,3 mare out of a 14.1 mare by a 15.2 stallion, and a 14.1 mare out of a 14.2 mare by a 16.2 stallion - so who knows! The first mentioned 14.1 mare than had a 16+ colt by a 17 hh stallion

[busymare]

Sorry OP not answering your question but I got intrigued and thought others might be interested (thank you sarahp I found it fascinating and had not heard of this research before).

I found a Shire-Shetland paper from 1938- when ethical considerations were not given the scrutiny or importance that they are today.

rspb.royalsocietypublishing.org/content/125/840/311.full.pdf

I was fairly horrified by the research and their relaxed attitude with the mares foaling unmonitored (and consequently they lost 2 foals to suffocation); not to mention the suffering that could have resulted if a mare had foaling difficulties. And fundamentally their scientific method was weak their conclusions were based on a very limited number of mares & foals and did not include proper controls (accurate observations of pure bred foals).

However that said their observations have been validated by modern work such as:

www.reproduction-online.org/content/127/1/67.long

Here they use pony x TB as I do not believe that nowadays they would get ethical approval for the more extreme cross.

[sarahp]

Thanks for finding it - saved me the trouble! Nowadays many vets think that foals "suffocated in the bag" were actually dead at/during birth as a normal healthy foal would get itself out, so maybe the ones they lost were as a result of a protracted labour, no way of knowing as unsupervised. As you say, nowadays ethical considerations are tighter than they were.

I hadn't seen the later paper, published after my time in College so wouldn't have been brought to my attention as the previous one was but I do have a few observations. First they used ET so the foals were pure breds of each size, not genetic crosses as in the earlier study - would that obviate the need for data on pure bred foals in the earlier study? Second it was more about the growth after birth than the birth size, which is the part relevant to the OP, and third that "pony" mares covers a huge range of possibilities, I would like to see more details on those. Admittedly I've only skimmed through quickly and they do give an average weight of mares but would a chunkier but not as tall mare have more foal room and hence give a TB foal a birth advantage over a taller but narrower and less deep one of the same weight? My feeling is that it would, as I said above, but this study gives no information on this.

[busymare]

Sorry yes posted the wrong link that was part 3 should have been part 1 in utero:
www.reproduction-online.org/content/123/3/445.short

I just found these when I was looking for the old paper and it seemed like a much better experiment (but I too have only skimmed!)

My comments were directed at the old paper? With ET they had Tb into Tb and P into P data to provide an accurate baseline taking into account any impact of ET itself. I agree I found 'pony' a very broad definition. This is not my area, but I assume that a chunky little mare would have a larger surface area of allantochorion than a taller pony of lw build so they have taken uterine capacity into account by measuring this, but I could be wrong!

[sarahp]

Maybe ET wasn't yet developed when the old research was done, so genetic crosses had to be used?

I took the new paper to show that the size of the mare would have a great influence on the birth size of any foals, as I said above, and I'd agree with you re the surface area of allantochorion. Nice to have proper scientific corroboration, many thanks.