Use of a semi-quantitative sweat test in thoroughbred horses

A practical test for evaluating the sweating response to various concentrations of the specific beta 2 agonist, salbutamol sulphate, is described. The results of performing this test on horses (n = 54) considered to be "free sweaters", horses (n = 6) that showed signs of heat stress following exercise, and horses with complete anhidrosis (n = 2) are presented. The results indicate that intradermal injections of 0.1 ml of salbutamol sulphate at dilutions of 10(-7) or less are suitable stimuli to elicit a visually detectable local sweating in horses with a normal sweating response. Horses that only sweated at the sites where salbutamol solutions with dilutions of between 10(-4) and 10(-6) were injected, probably had a reduced sweating response and could be considered to be suffering from partial anhidrosis. Horses with severe anhidrosis of long duration did not sweat, even in response to salbutamol solutions with dilutions of 2 x 10(-3).