Whats the biggest she can carry?

So I am wanting to breed Shylo again after this pregnancy (only if this one goes well of course)
She is 12.2hh and I'm just wondering what ya'll think the biggest she could carry would be?
I'm hoping to find a smaller Thoroughbred to breed too somewhere down the road but I absolutely DO NOT want to put any strain on Shylo or make her uncomfortable.
I've been told by different local breeders and such that if I bred her to a 15.3hh stud she should be fine but wouldn't go any higher.
I would just like your opinions :)
Thanks!


Oh and right now she is bred to a 11.3hh welsh pony stud...you can see pictures of her in my virtual barn

Theres been much research done thats proven it doesn't matter how big a stud is when breeding a mare. The mares uterus allows the foal to only grow so large regardless. After birth diet and genetics take over and determine the size the foal will grow to. They breed Shetland ponies to Draft horses and vice versa. At birth the foals from the pony mares where much much smaller then those from the draft mares. By 3 years of age they were all the same size.

I don't know that it would be safe to go to the extreme like breeding her to a draft but I bet she would do fine with a large QH or an average TB.

there is actually a really good discussion about breeding pony mares to horse stallions on another forum. Personally, I would NOT breed a pony mare of that size to a stallion over 16hh. You could really run into some problems with birthing IMO. BUT, you should discuss with stallion owners the history of the foal sizes with their stallion. Some stallions produce large foals at birth, some produce smaller foals at birth. But rule of thumb is, no bigger than 2 hands difference.
And certainley if you are doing live cover, you wouldn't want a stallion that is too big so as to injure your mare either.

cheekyhorse do you mean two hands at birth? Thats 8 inches which is a HUGE amount!!!!!

Exactly!
The mares uterus will determine how big the foal can be.

no, two hands difference between sire and dam.
I don't agree with what the others have said about the mare's uterus determining the size of the foal at birth. That is not necessarily true and I personally have not read any studies to prove this so called 'fact'. I am a veterinary technician so I've seen first hand what can happen when you breed to a stallion that is much larger than the mare. I know of breeders who have lost mares and foals due to large birth size. It is the same in dogs, or in any other species in fact. You wouldn't breed a german shepherd male to a mini schnauzer would you? You are asking for trouble.
I use Dr. Juan Samper for my reproductive work, he is a world leader in reproduction and has written books on the subject that are used in universities. I'd be curious to hear what he would have to say on this, I'll ask him next time I am in collecting my stallion which will be within the next couple of weeks as breeding season is starting up again.... I'll let you know what he says.

Think about this logically for a moment. A foal only has a certain amount of room to grow. Regardless of whether or not the sire is huge or tiny, the baby can only grow to be a certain height and length within the mare. It's why maiden mares tend to have a bit more difficulty, as they haven't stretched out yet. Same thing as with women. Ever wonder why a 5" woman can deliver a really long baby? But a 5'8" woman can't without complications? It has to do with the pelvis and the way that the uterus is molded. Now, that only dictates how big the baby will be once he's born. After that , genetics and a variety of other things dictate how big he'll end up. (again, why that same looong baby is only 5ft when all is said and done?)


I wouldn't be concerned about height. Instead, I'd be concerned about bone. If you're breeding your really teeny narrow mare to a hulking draft horse, its not the height that is a concern. It's the fact that the the mare's pelvic opening might not be wide enough to accomodate the mass (not the height) of the foal.

If you do AI, you wouldn't have to worry about the size of the stallion hurting her since she wouldn't actually be covered.
You see crosses all the time that a mix between some small horse/pony and a draft. If your worried, I would contact as many vets in the area and get their opinions on it.

Skyhuntress hit it on the head. There are a lot of factors that can make mares have complications--you can't blame 'height' just by looking at them.

Most mares will only allow the baby to grow so big. But, be careful--if you breed her to a 16hh stud, it does not mean the baby will come out 'in the middle'. He'll either be sized like the mother, or sized like the sire.