While she was colicking (sp?). She wacked after the race because she was dehydrated from the trailer ride the day before, I brought her up much to close to the race. I was surprised they elyted her, and she continued to colic that afternoon, so I ended up taking her to Davis (of course by the time I got there, she was fine). I got a lecture from that same vet about how I was supposed to elyte her on the race, and when I took her to Davis, the head of equine medicine contradicted the vet at the race had said. So, I'm not sure who was right. I will tell you one thing, we had sucessfully competed and finished several races in previous years, and I hadn't elyted my horse all that much and she was fine in those races. We basically concluded later that she was dehydrated from the trailer ride (despite being trailered frequently, she still hates it), and so I learned a valuable lesson that day, bring my slightly neurotic horse earlier in the day before the endurance race so she has time to settle (and drink lots of water!).
Giving an endurance horse (or not giving) elytes is one of the most hotly debated things I've ever seen in the endurance field. The opinions run the "gamut" of whether to give elytes or not, whether they cause ulcers or not.
As an aside, if you feed your horse electrolytes in their feed before a race like I do, and have a horse like mine who won't *touch* her food if there is a drop of salt or powdered elytes in her feed (and that is saying a lot because I call her the Hoover Vaccuum) there is a great isotonic elyte pellet supplement I discovered a while back called Ultra-Elite Lytes (Formerly Electro-Balance™ EQ). My horse happily eats this stuff. Their product plug: Ultra-Elite Lytes is an isotonic electrolyte pellet supplement containing 4 strains of microbial cultures to support the horse's digestive tract. Isotonic supplements provides the proper concentration of minerals in the same balance as those found within cell membranes. This is important for maintaining osmotic pressure, fluid balance, and proper pH during exercise or physical stress. Ultra-Elite Lytes features alfalfa, wheat bran, molasses, and dextrose in a highly palatable pellet form.
My horse was diagnosed with very mild ulcers a few years ago, and was treated with gastrogart and is now fine. I'm very careful about giving her elytes on rides because the last evidence I had seen attributed elyting to ulcers. You can incite a whole firestorm about whether or not elytes cause ulcers, but to be conservative, I give my horse 1/4 or 1/2 doses while out on rides.
JMHO, I think that the high rate of ulcers in endurance horses is more attributable to the stress of transport and competition than elytes, but I'm sure that heavy elyting doesn't help.
Horse Journal had a good point about the administration of elytes:
1) Administer elytes in drinking water (tried this with my horse, she wouldn't drink the water )
2) Administer after they have had the oportunity to drink water, preferably a few gallons
3) Administer after they've eaten
4) If need to syringe feed them powdered elytes use antacid or corn oil as the carrier
Also, as an aside, I don't believe they evaluated paste elytes, I think the article only covered powdered elytes.