Well, first of all 1000 lbs. horses pull carts
all the time. So there's not an arguement that there build isn't for that. Light horse have been pulling carts since before the Romans. You can see Amish using them regularly today, you see them all over the show world, you see people pulling sleighs with them, you see people out on the roads riding for pleasure.
Second, yes, a 2000 lbs. horse IS going to jump differently. That doesn't equal to not be able to jump and breaking down. Different style, different way, does not equal can't or shouldn't.
Third, it's about
common sense. If you are using a full draft, don't be riding hard before they are 4-5 years old. A lot of people out there tell you that you can do light jumping from 5-6 then after that they can move into regular jumping (that being the low level jumps which are more suited for their build).
If you put a
solid foundation on them - good training, breaking down is not going to be an issue. A horse
will tell you if it is. I've seen this as well. Drafts that start in the jumping field and just don't have it then move onto another discipline. And then there are the drafts that live for jumping.
It's time to get away from the old thinking of draft horse equals plow. Full draft can do anything now.
I talked to every draft horse person I could when I got my boy. There are several draft horse forums with full draft jumpers even back in 1999 when I got my boy. Those people were fighting the draft = plow back then.
This link is from the Percheron Horse Association web page. At the bottom it tells that some make fine jumpers.
Percheron Horse Association of America
On the main page a picture of one jumping:
Percheron Horse Association of America
This is a pretty famous Belgian Jumper:
Pics of Horses
If you take the time to look around there is a lot out there on them. Irish Drafts often jump well into their teens.
And
again it's all about good training.