Sorry, but an obese horse will not get in shape ASAP. Just like people, the farther out of shape they are the slower they need to go.
Just start slowly cutting back her feed and working her up to a decent workout. Watch her breathing, and her sweating as you work her whether in a round pen or on a line. If you are seeing nostrils flare because she is breathing hard, slow down, walk her out, cool her down and then keep track of how long it takes her to work up to it, The next time up it a bit.
You dont want her to lose weight to fast as that can cause problems as well.
[SIZE=14pt]I am 100% with Annette, You can kill her by throwing her into hyperlipemia if she starts using her fat stores faster than her liver can clean the blood. Show horses are KEPT in condition not suddenly made that way. Go slow and then keep her where you want her once she is there by keeping the diet and exercise program.[/SIZE]
A large belly doesn't always mean the horse is fat. You need to look at the overall picture. I have seen horses with very large bellies who are actually underweight. Take a close look, does her backbone show, can you see any ribs, what does she look like overall??? If she just has a big belly she may need to be wormed and need to be eating more in the way of grain and less in the way of hay. Horses that are getting large amounts of hay and no grain can get huge bellies while not being in good condition elsewhere. Do you have any pictures of her Kayla???
My mare was the same why when I first got her. She had been a broodmare on grass for 10 years. I really didn't cut her feed down that much. All I did was walk her and that did the trick. Most people walk their dogs...I walk the dogs and my minis! My neighbors must think I am crazy!
Hey Kayla, Congrats on your new horse! What's her colour, size, name? Got any pictures yet that you could post? How's Stormy? You've got to come by sometime...I've got his only offspring back now! Littlefoot's Sweetgrass is his 4 yr old silver dapple daughter. She looks alot like your beloved Dandy! Kinda chunky too. Good luck with your mare.
I would start her slow with a walk and slow trot on a lunge line for a week. If she is really out of shape easy on the trot. Hook her up and drive her at a walk. Once she can do the walk without lathering add in a trot of a few hundred yards then walk again. As her condition improves increase the length of the trots. Monitor her health while training. All that extra weight puts added strain on her feet. As conditioning improves you can give her hour long drives four or five times a week. I think August is not being very realistic as a time frame. More like October or November. It could take until August before you will get her to trot a mile without working into a heavy lather. This time of year is tough to give horses heavy exercise because so many parts of the country are just to hot.