Anhidrosis (Non-Sweaters)

Tiz The Season! Chances are if you have a thoroughbred in training in Florida during the
summer you have a 20% chance of it becoming a non-sweater. (Based on an epidemiological
study performed by Mayhew and Ferguson and published in 1987) Overall populations were
affected at 5-6%.The hallmarks of a non-sweater are a very high (panting) respiratory rate and
a mildly increased temperature on rectal exam. However acute anhidrosis may yield significant
elevated rectal temperatures. Horses tend to lose their hair particularly around their face and
eyes. These signs may be a precursor in a horse that has yet to stop sweating.
What causes it? The scientific answer is still not out there. But…. The above mentioned study
found that horses tend to be conserving their electrolytes, particularly chloride. Yet one will find
that just giving horses electrolytes does not start them sweating again. Years ago I witnessed
Clayton O’Quinn tube his horses with electrolytes and though it helped somewhat it did not start
the sweating again. My guess is that its not just electrolytes, but water. Our bodies exist in a
particular balance of water to electrolytes, and if one gets thrown out of balance, the other does
too. So various treatments usually fail or don’t really fix the problem.
So how do we prevent it? Not too long ago I owned a bunch of (unfortunately) cheap horses and
they trained in Ocala through the summer. I provided every horse its own individual loose salt
ration (a double handful) everyday by the stall door. Some devoured it; some ignored it. But
there is no way some training horse can get enough electrolytes out of a salt block or in its feed
on a daily basis. I did not have one non-sweater. Ive passed this information on to several
clients over the years (Casey Seaman comes to mind) that reproduced my findings. So the key
I hope this helps.
Just as a postscript. Many of you take pride in treating your own horses. And its a lot less
expensive in this day of skyrocketing costs than calling the vet out for every nuisance. Just be
careful if you take it on to remove stitches. If you just cut the knot off you are leaving a
significant portion of stitch under the skin; and it can cause problems later on. Usually just
cosmetic, but still a problem, particularly in a horse going to a sale. So just be careful to cut just
one strand below the knot and pull the entire stitch from under the skin. And just so you know I
don’t bill for taking stitches out; even if they aren’t mine!

July 3, 2017

H.O. Ferguson, DVM