Equine related excerises

Ok - I have a question....I do not know if the people who operates or owns this database reads posts or what.....Anyway...

I am in training for eventing and I know I KNOW about 99% of you have NO idea was eventing is....

Here's the link to eventing....just so you know what it is....

http://en.wikipedia.org/wiki/Eventing

This is a very demanding and dangerous sport and many times horses are very high strung to deal with especially when it comes to cross country.

Anyway, in the database here - there are horseback riding - general, horseback riding - trotting, grooming and these seems more like generalized horse back riding - TOO LOW calories....

How do I figure out the right exercise calories output when I am dealing with my crazy mare and when it comes to eventing time? And where did these people come up with these numbers?

When I train my mare and she puts up a battle, I am sweating like bullets and could barely walk after being done with her....on good days, I would say about 400 calories an hour but bad days - I feel like 800 calories!

Thanks!!!

Holly