Will jumping my dressage horse ruin his dressage?

No. If anything, it should improve it, because jumping, like all other equestrian disciplines, uses dressage. That's where hunters and jumpers get their steering, brakes, manners, and control from. Plus, dressage teaches horses to use and move their bodies in a gymnastic, flexible way which helps them avoid injuries when they do work involving speed and balance ( and jumping requires both). So I don't think that you will ruin his training by jumping him. Lots of horses are trained for more than one discipline, you know.

No. Jumping your dressage trained horse will not ruin his dressage training, but jumping him too high too fast might cause him to get an injury.

I am sure that your horse would enjoy doing a different type of riding every now and then!

Not at all. Many upper level dressage horses are trained using ground poles and cavaletti on a regular basis to encourage more hind end engagement. It is sometimes nice to change the pace and pop him over a few small fences (less than 2' if you are not jumping regularly) occasionally just to keep his brain and body smart! Just remember that you should not be hacking him over giant galloping cross country fences or huge stadium oxers. Keep it light, small, simple and positive!

If you find that your horse is excelling and enjoying jumping and dressage and want to consider eventing - find a good trainer that can help you both transition to regular jumping lessons!

Only if the horse gets crippled up from jumping or mishaps from same. . .people who love to jump horses often forget how hard it can be on them. The pounding takes its toll. . .especially on bad footing.

Only you can ruin the horse.

When the student is ready the master appears

if that were the case there would not be three day eventing