Re: electrolyte supplementation

[Michael I Lindinger <mlinding@uoguelph.ca>]

> Please note that the discussion from me and the reference to Jeannie Waldron
> did not suggest WITHHOLDING electrolytes, but rather not forcefully
> supplementing electrolytes.  I don't think any of us would withhold free-
> choice electrolytes from the working horse.
> 
> Although I am not good at collecting literature, I know I have read excerpts
> from research indicating that both the kidneys and the sweat glands become
> more conservative of electrolytes when the body is slightly depleted, and also
> become very unthrifty with them when there is always plenty there.  One study
> showed that sweat from conditioned horses can become as much as 90% less
> concentrated, but that this efficiency is not reached in horses that are
> constantly supplemented.  I don't recall actual numbers for kidney
> conservation of electrolytes.  I do simple taste tests of the sweat on my
> horses to ascertain their degree of sweat efficiency--on unconditioned horses,
> the sweat tastes very noticeably salty, and on the very fit ones, I almost
> cannot detect a salty taste.  The body cannot store excess electrolytes, hence
> any added at non-stress times must be excreted in some manner, generally
> through sweat or urine.  It simply does not make sense to enter a competition
> with these systems primed to dump the very electrolytes the horse needs to
> conserve.
> 
> Heidi
> 
Dear Heidi,

One needs to differentiate between the concept of 'conservation' versus
what what is available to be lost (in either urine or sweat. If the
electrolyte is not available, it cannot be lost at adequate rates to
produce an optimum sweating rate for effective thermoregulatory cooling of
the exercising horse.

You noted, correctly (as I pointed out yesterday) that sweat electrolyte
concentrations may decrease in horses as they become conditioned. This is
primarily ascribed to the production of a MORE DILUTE sweat, i.e. more
water with the same amount of electrolytes. Therefore electrolytes still
are not conserved.

When you think about it, it does not make good sense to try to conserve
electrolytes at the skin, because this will impair the ability of the
horse to sweat and produce related heat stress problems. What may appear
as 'conservation' may be an inabilty to provide the sweat because the
water and electrolyte reserve is not adequate.

Sincerely, Mike Lindinger