Ambient temperature and relative humidity influenced packed cell volume, total plasma protein and other variables in horses during an incremental submaximal field exercise test.

The research article explores how varying levels of ambient temperature and humidity can affect physiological responses, such as heart rate, respiratory rate, body temperature and blood components, in horses while performing exercises of incrementing intensity.

Objective of the Study

The primary aim of the study is to examine how changes in environmental conditions, specifically temperature and humidity, impact the physiological responses in horses undergoing a submaximal incremental field exercise test.

Study Design and Methodology

• The study involved ten horses being exercised under differing conditions and observing their bodily responses.
• The exercises were carried out thrice in summer and autumn, i.e., in both high and low ambient temperature and relative humidity.
• The factors tested were heart rate (HR), respiratory rate (RR), rectal temperature (Tr), packed cell volume (PCV), and total plasma protein concentration (TPP).
• The exercise was performed for 4 minutes at speeds of 3.5, 4.5, and 7.0 m/s, with resting intervals of 3 minutes. Measurements were taken at rest, after exercise, and following a recovery period of 5 and 10 minutes.

Key Findings

• Results demonstrated that all measured parameters were notably higher when exercises were performed in hotter environments as compared to cooler ones.
• The increased values for HR, RR, Tr, PCV and TPP reflect the additional thermal stress experienced by the horses during exercise in the heat.
• The study highlighted that a greater relative increase in PCV (the volume percentage of red blood cells in blood) in hot conditions may offer a thermoregulatory advantage. This is likely due to a rise in circulating red blood cell volume rather than a drop in plasma volume.

Significance and Implications of the Study

• The research findings suggest that the outcomes of exercise assessments can be significantly influenced by differences in environmental conditions. Therefore, these factors should be considered when monitoring progress in horses during fitness and acclimatization regimens.
• The study may contribute to a better understanding of not just equine physiology but also that of other endothermic animals in relation to exercise and thermal stress.