A while back there was discussion on whether or not it was okay to cool a horse with ice water. I remembered Dr.Nancy Loving saying something about that, but it took me this long to dig it up. Some folks thought that since studies are showing no adverse effects in using ice water to cool event horses, that it is probably okay to use ice water to cool distance horses. I thought this might shed some light on the subject.
This is from Trail Blazer, July/Aug 95. BEATING THE HEAT, by Nancy Loving, DVM:
One of the big problems presented by a hot and humid climate is that often the water temperature is very close to the air temperature. In an insufferable hot climate, keep in mind that if the water has been sitting around a long time in a bucket, you may have to add ice to cool it to a potentially useful temperature before sponging the horse. The addition of ice cubes or frozen plastic water bottles ("Bullets") to buckets of water will achieve some temperature differentiation to improve conduction and evaporative cooling. This does not mean you should pour ice water on your horse. Please note that using ice water on a long-distance horse is a poor idea in any situation, even in heat and humidity. If water applied to a horses skin is TOO cold, then the superficial blood vessels will reflexively constrict and pull away from the skins surface. Instead of continuing to release heat, the blood vessels suck back into the deeper confines of the muscles. The result is a rise in muscle and body temperature quite the opposite of the effect you were trying to accomplish. And worse, muscles may stiffen or cramp in response. Heart rate will remain elevated due to high body temperature and/or muscle cramping. This will certainly not help you get through a vet check in good speed.
(Presently studies are underway on the use of ice water to cool event horses. The work effort of event horses involves both aerobic and anerobic exercise. Ideally, an endurance horse works primarily in the aerobic range, and at relatively slower speeds than a galloping and jumping event horse. The differences in exercise intensity between the two sports may make it difficult to draw correlations from up-coming research. Be cautious in extrapolating from the ice water data that is directed towards the 1996 Atlanta Olympics.)