(Disclaimer: sorry for the photo sizes...I don't know how to edit them smaller! LOL)
I have ridden, trained, and/or owned many different breeds and types of horses. I have also ridden and/or competed in many different disciplines. I won't list them all, but suffice it to say that in everything, the underlying principles of riding have been the same.
I believe (and practice) the same principles of riding and training the horse, no matter what breed or type it is, for the foundation of the horse's training. No matter what the horse will specialize in, the foundation is built according to the Training Scale guidelines (or pyramid, as some call it) of the USDF and the German FN, up through about third level (single flying changes and all lateral movements).
This has served my horses well, so the (what I call) standard principles of training carry over into all types of competition, and across all saddle-type breeds (walk/trot/canter breeds, that is--the gaited breeds need special consideration in the training scale, and will specialize much earlier in the training process, and I do not have much experience with them at all).
But, do all breeds carry over into dressage
competition with the same consistency? In other words, is it a level playing field in dressage competition for all breeds? The one-word answer is "no". The qualifier is "with the same consistency". And it has nothing to do with not liking a particular breed on the judge's part. Dressage judges judge according to an ideal standard of quality and training, which are outlined in the USEF rules for dressage. And dressage judges, in my experience, have been the most educated, methodical, and fair group of judges among ALL the disciplines.
ALL 3-gaited breeds and types--they don't even need to be breed-registered, are (and should be) able to compete in dressage competitions, but when it comes to dispersing more favorable scores and awards, there is a component of judging that separates the breeds that are developed specifically with the sporting disciplines (dressage, jumping
) in mind from those breeds developed for other purposes (flat racing, endurance, sprinters, pulling, etc.).
That component is quantified in the first of the collective scores (Gaits), but it is also the underlying theme throughout all of the figures and movements of the entire test. It is more than "gaits". It is the quality of those gaits, and it goes to the genetic physical and psychological type.
These (yes, I am talking about the warmbloods) breeds are developed with an "uphill" conformation that makes it easier to shift their point of balance back for greater collection, and move freely through their backs and shoulders; they have large open joints that make elasticity and collection easier for them; great strength through their loin areas, as well as other physical attributes that have been proven to be desirable specifically in the sporting disciplines.
We hear about "rideability" a lot in descriptions of the warmbloods, which speaks also to the psychological attributes of the horse allowing himself to be guided in all sorts of contortions, and remain calm and relaxed (this is quantified in the "submission" score in the collectives), and to not resist the rider. The horse gives himself to the rider; body and spirit and accepts the rider's guidance completely. These are the ideals that are in the forefront of the breeders' philosophies.
Other light horse breeds have been developed with other factors more in focus--run fast, jump high, be brave/bold (Thoroughbreds), think on its own, crouch down and pivot (quarter horses), pull heavy loads, take small steps and push weight through the chest (drafts), etc. Which is not to say that those breeds don't possess any amount of the same qualities that the warmbloods do--it is just that the emphasis of the physical and psychological aspects are different.
And that is one reason that ALL breeds can and should "do dressage"--(refer to my previous post from 7/25/09 "Is it REALLY dressage"), the "other breeds" will have a more difficult time winning in dressage competition against the warmblood types, all other things being equal. Of course there will be exceptions that prove the rule, and when it all comes down to it, TRAINING is key. If you spend the time necessary to develop a solid foundation on any breed or type of horse, you will get your share of the ribbons, and the scores as well.
I have found that the key to riding an "other breed" in dressage competition and winning is in the quality of the correct training that can garner enough points to win more and higher scores and ribbons in competition against the warmbloods--technically correct, well-ridden, and total focus by the partnership on each other makes a formidable presentation.
Just know that you have to be patient, and get help from a trainer/instructor that has experience with the breed you are working with. The journey is much easier if you have quality help.