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RE: [SPAM] Re: [RC] Won't hurt? - heidi
Gayle has certainly done some good work on electrolyte loss, and often
it is Gayle's numbers that are used when people tout use of lots of e-lytes. But the amounts of e-lytes lost are only part of the story. You also have to look at how much the horse takes in in its feed, how much there is available in the hindgut, and how the body processes those e-lytes that it does take in.
Using Gayle's numbers and then going to the NRC charts on feeds, one can
quickly discover that the daily intake of e-lytes in forages in the amounts that our endurance horses eat exceeds the amounts lost in Gayle's studies on a 100-mile ride. Additionally, the horse carries about 2 days' worth of forage in its hindgut--a TREMENDOUS e-lyte reserve.
Looking at how the body processes e-lytes, first they have to be
transported across cell membranes in the GI tract. This is an active process requiring fuel (glucose, VFAs, whatever--substrates that can be turned into ATP in the cells)--and often the "hitting the wall" that is ascribed to low e-lytes is REALLY a low fuel situation. Then, there has to be sufficient fluid in the various body compartments (intracellular, extracellular, bloodstream, etc.) to properly process e-lytes--in other words, if the concentration of e-lytes is too high, there are complications. In a dehydrated horse, administering more and more e-lytes can lead to devastating results. In some cases, excess e-lytes can cause brain swelling, seizures, etc., when the body can't properly transport and/or dilute the e-lytes.
Bottom line--e-lytes are NOT harmless, innocuous substances. While
certain levels are certainly necessary for life, more is not necessarily better, and yes, you CAN overdose them! At the very most, one should only be replacing a portion of the calculated loss for an event--not the entire amount, since the horse also has to process those present in his feed. In many (if not most) cases, the e-lytes that are already present in the hindgut and that the horse ingests in his feed are adequate to cover the losses in the sweat.
Heidi
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