I'd take her off the triple crown, and put her on something like semionle wellness perform safe. It is a low starch, high fat pellet feed. I used it on my boy when he was on training because he was losing weight and I was having a hard time toning him - alot like your situation. The good thing about this feed is that it is low starch to keep them 'level headed' and they don't go crazy. Starches are no good for them. I was very pleased with this feed. As far as feeding recommendations for the pellet, the information is on the bag. But I would give pellet twice a day. I would add flax to her diet as well, it will give her a nice shine and other fatty acids she will need.
For more calories, I would add beet pulp WITHOUT molasses, to her diet. Just make sure you soak it really well about two hours before you feed. Beet pulp is very good for them. Two - two and a half quarts of beet pulp 2 times a day. You can mix it in with the grain or put it in a separate bucket. I like mixing it with their grain and I love feeding it because then you can sneak supplements, medicine, almost anything to picky eaters.
So I'm guessing she gets two flakes of alfalfa a day? She is going to need more than that. Horses really should get constant roughage to keep healthy. Invest in a hay net so she will have to work at it for awhile instead of eating it within an hour or so. But what I would do (if you have the option to do this) is put the flake of alfalfa in the hay net in the morning and give a flake of Timothy or T/O - some kind of nice grass hay on the ground as well. That way when she finishes the grass hay off she will have to work to get the good stuff (the alfalfa). If she finishes the alfalfa off before the next hay feeding, I'd put another grass hay flake in the net and let her continue to work on that. Then at night feeding - I'd put the 1 flake of alfalfa in the net and the grass hay on the ground. This will insure that she is getting enough small meals all day. Some people like to double up on the hay nets so it takes them longer to eat it. This is also a good idea because if they are in a small pasture or stall then it will keep them from getting bored and will keep them out of trouble :p But a working horse should be getting at least 4 flakes of hay a day regardless, at least two or more being a grass hay.
Good Luck with your horse!
EDIT: I forgot to add! generic metamucil works great for the sand. My horses are keep on a lot of sand and I do metamucil once a month. They get 2 scoops twice a day for 7 days.
Last edited by justhorsinaround1; 09-24-2012 at 04:24 PM.