Katarzyna Strzelec
Cortisol concentration in saliva as an indicator of the stress reaction in horses studied during different types of utility
zeszyt 374, ss. 87
Measuring the level of the unbound fraction cortisol, which is directly proportional to the cortisol level in blood, allows the analysis of the stress phenomenon that can be observed in horses taking part in competitions as well as during equine value test performed with non-invasive methods. The aim of this study was to: 1) determine the cortisol level in saliva of horses used for various purposes and study the influence of other factors, 2) identify the groups of horses with high levels of cortisol in saliva at rest and after exercise, 3) classify the purposes for which the horses were used based on the different types of stress they induce, 5) identify the advantageous and disadvantageous ranges of the cortisol level values as indicators of the equine value, 6) search the best time to measure the cortisol level in saliva in order to precisely identify the horse’s readiness for achieving top results of equine value. The material for the study consisted of the samples collected from randomly chosen 620 horses divided by six factors: type of uses, research season, breed, age, sex and coat colour. The saliva samples were collected five times in each case (evening, morning and after each exercise stage).
The data were analyzed with the use of multifactoral analysis of variance, T-Tukey test and Pearson’s correlation. The research showing the correlation between the cortisol level in saliva and the type of use was conducted for the first time. Advantageous competition results should appear when the horses show increased levels of cortisol at rest and low levels during and after competition.  The results made it possible to identify the ranges of the cortisol level from which an advantageous or disadvantageous influence of the hormone on the equine value can be observed. Horses promising with regard to the future career should have the cortisol level above 2.48 nmol/l during the evening measurement a day before the competition and between 1.85 and 6.39 nmol/l before the competition. The cortisol level in saliva after effort should not be higher than 27.01 nmol/l. The cortisol level measurement after the first competition stage was identified as the representative time for sample collection in this type of study. The method of evaluating the cortisol level in saliva used for predicting the competition results can be especially useful in the case of horses taking part in show jumping and eventing as well as the races performance test.