Salivary cortisol and eye temperature changes during endurance competitions

Abstract

Background The purpose of this study was to investigate the usefulness of salivary cortisol (SC) and eye temperature measured by infrared thermography (IRTET) as biomarkers to manage competitions more effectively and monitor horse welfare in endurance competitions. Based on previous studies, it was hypothesised that pre-exercise baseline SC and IRTET would be higher in younger or less experienced horses, and that post-exercise variation from baseline would be higher in the top finishers. Results Salivary cortisol measured in 61 competing at qualifier 40 km and 80 km rides showed an abrupt variation (93–256% rise) of the baseline SC levels [median ± interquartile range (IQR) = 0.27 ng/dl ± 0.36] obtained at the Pre-Inspection (PI) into Vet Gate (VG)1 independently of the covered distance, but modest or even lower in the subsequent Vet Gates, e.g. VG2 or VG3. The IRTET measured concomitantly in 16 horses showed significant (p < 0.05) higher levels at the PI in less experienced horses participating in the 40 km ride (median ± IQR = 35.7 °C ± 1.4) than their counterparts in the 80 km ride (median ± IQR = 35.0 °C ± 1.5), but not SC. Baseline SC levels at the PI of horses classifying in the Top5 in the 40 km ride category were significantly (p < 0.05) higher median ± IQR = 0.90 ng/ml ±0.61) when compared to horses positioned from 10th position on (median ± IQR = 0.16 ng/ml ±0.40). A lower IRTET in the PI was correlated with better placement (p < 0.05) and those in the Top5 (median ± IQR = 33.9 °C ± 0.0) had a significantly (p < 0.5) higher variation (+ 10.65%) into the last VG. Conclusion Pre-exercise baseline IRTET levels, but not SC, were higher in less experienced horses in the 40 compared to their counterparts in the 80 km ride competitions. SC and IRTET showed different indications according to the competition. In the40 km ride competition, higher baseline pre-exercise SC levels seemed to be linked to a better classification outcome. In contrast, in the 80 km ride horses, the higher IRTET variation from pre-exercise into final Vet Gate was the parameter associated with a better performance. A more controlled environment and a larger sample are needed to confirm these results and monitor horse welfare in competitions.

Correlation between Ocular and Rectal Temperature with Intra Ocular Pressure in Horse during Exercise

“…The use of a thermo-camera allows for the rapid recording of the ocular temperature, compared to the digital thermometer used for measurements of rectal temperature. The results of this study support the use of IRT as an additional, rapid and non-invasive method for measuring body temperature [ 11 ].…”

“…Ocular temperature (OT), which is easily measurable, is used as a physiological parameter as it may reflect body temperature changes in response to events and stimuli, and this is accomplished by means of infrared technology (IRT). As it reflects body temperature, the measurement of OT can be used to monitor acute and chronic stress levels in horses during physical exercise and competitions [ 7 , 8 , 9 , 10 , 11 ].…”

Selection of Image Texture Analysis and Color Model in the Advanced Image Processing of Thermal Images of Horses following Exercise

“…Such an approach can be used to monitor the exertion level of a horse to achieve the required training response without tipping over into fatigue levels associated with injury. However, the introduction of advanced digital IRT image processing into the monitoring of equine welfare during conditioning and competition requires further research, including the assessment of equine emotional state [ 70 , 71 , 72 , 73 , 74 , 75 , 76 ] and cortisol release [ 72 , 75 , 76 ].…”

The Effect of Rider:Horse Bodyweight Ratio on the Superficial Body Temperature of Horse’s Thoracolumbar Region Evaluated by Advanced Thermal Image Processing

“…Within physiological indicators, heart rate [ 11 , 12 , 13 ], heart rate variability [ 14 , 15 ], and cortisol concentration [ 12 , 16 ] are the most commonly measured [ 10 ]. However, these measures are at risk of confounding by physical exertion [ 10 , 16 , 17 ]. Therefore, in the case of horses used for riding, other more specific indicators of equine well-being are required to assess rider:horse interaction.…”

“…Therefore, in the case of horses used for riding, other more specific indicators of equine well-being are required to assess rider:horse interaction. Recently, the infrared thermography (IRT) measurement of the selected regions of the body surface temperature was proposed to assess both the horse’s emotional state [ 18 , 19 , 20 ] and the horse’s physiological response to an effort [ 17 , 21 , 22 , 23 ], also including the evaluation of the impact of the rider:horse bodyweight ratio on the equine organism [ 24 , 25 ].…”