Horse Preferences for Insolation, Shade or Mist Curtain in the Paddock under Heat Conditions: Cardiac and Behavioural Response Analysis

Cortisol levels, heart rate, and autonomic responses in horses during repeated road transport with differently conditioned trucks in a tropical environment

Horse's stress responses have been reported during road transport in temperate but not tropical environments. Therefore, this study measured cortisol levels, heart rate (HR), and heart rate variability (HRV) in horses during medium-distance road transport with different truck conditions in a tropical environment. Six horses were repeatedly transported in either air-conditioned trucks with full (ATF) or space (ATS) loads or non-air-conditioned trucks with full (N-ATF) and space (N-ATS) loads. Blood cortisol was determined beforehand and 5, 30, and 90 minutes post-transport. HR and HRV were assessed pre-transport and at 15-minute intervals until 90 minutes post-transport. Cortisol levels increased significantly in N-ATS horses (but non-significantly in ATF, ATS, and N-ATF horses) at 5 minutes post-transport and returned to baseline by 30 minutes post-transport. Predominant parasympathetic nervous system (PNS) activity was observed during the first few hours and returned to baseline until the destination was reached. A recurrent, increased PNS activity was detected post-transport. Interaction effects of air condition-by-loading condition-by-time, air condition-by-time, and separate effects of air condition and time were observed on HR and various HRV variables during transport. A transient increase in beat-to-beat intervals, coinciding with decreased HR, was observed in ATF horses. The PNS index increased, corresponding to a decreased sympathetic nervous system index, in ATS horses during transport. We suggest that medium-distance road transport causes no stress for transport-experienced horses in a tropical environment. Air and loading conditions impacted hormonal and autonomic modulation, causing different responses in horses transported in differently conditioned trucks.

Heat stress in horses: a literature review

Healthy adult horses can balance accumulation and dissipation of body heat to maintain their body temperature between 37.5 and 38.5 °C, when they are in their thermoneutral zone (5 to 25 °C). However, under some circumstances, such as following strenuous exercise under hot, or hot and humid conditions, the accumulation of body heat exceeds dissipation and horses can suffer from heat stress. Prolonged or severe heat stress can lead to anhidrosis, heat stroke, or brain damage in the horse. To ameliorate the negative effects of high heat load in the body, early detection of heat stress and immediate human intervention is required to reduce the horse's elevated body temperature in a timely manner. Body temperature measurement and deviations from the normal range are used to detect heat stress. Rectal temperature is the most commonly used method to monitor body temperature in horses, but other body temperature monitoring technologies, percutaneous thermal sensing microchips or infrared thermometry, are currently being studied for routine monitoring of the body temperature of horses as a more practical alternative. When heat stress is detected, horses can be cooled down by cool water application, air movement over the horse (e.g., fans), or a combination of these. The early detection of heat stress and the use of the most effective cooling methods is important to improve the welfare of heat stressed horses.

Effect of Cooling Blanket on the Heat Stress of Horses in Hot and Humid Environments

Simple Summary

Heat stress is serious problem for livestock. While riding horses and racehorses spend the majority of their days in stalls, there are few reports on effective methods for reducing stall heat stress. The aim of the present study was to evaluate the effectiveness of an ice horse blanket in hot and humid environments. Twenty healthy horses were measured first without the blanket (C) and then measured with the blanket (IB), or vice versa, in a cross-over trial. The blanket was designed to keep cooling the front back, the rear back, and the loin. The skin surface temperature of the front back was decreased with cooling time in IB, whereas it was not changed in C. Similarly, respiratory rate and plasma cortisol level also decreased only in IB. The blanket used in the present study had the advantage of allowing for gentle cooling of the horse’s body without the use of water or fans. Applying this methodology should enable effective reduction of heat stress not only in horses but also in other mammals kept in barns.

Abstract

Heat stress is serious problem for livestock. While riding horses and racehorses spend the majority of their days in stalls, there are few reports on effective methods for reducing stall heat stress. The aim of the present study was to evaluate the effectiveness of an ice horse blanket in hot and humid environments. Twenty healthy horses were measured first without the blanket (C) and then measured with the blanket (IB), or vice versa, in a cross-over trial. The blanket was designed to keep cooling the front back, the rear back, and the loin. Skin surface temperature, respiratory rate, rectal temperature, and plasma cortisol level in both C and IB were measured at 10:00, 12:30, and 15:00. The skin surface temperature of the front back was decreased with cooling time in IB, whereas it was not changed in C. Similarly, heart rate, respiratory rate, and plasma cortisol level also decreased only in IB. The blanket used in the present study had the advantage of allowing for gentle cooling of the horse’s body without the use of water or fans. Applying this methodology should enable effective reduction of heat stress not only in horses but also in other mammals kept in barns.

Behavioural responses of Konik Polski horses to natural, familiar sound of thunderstorm, and unfamiliar similar-sounding sounds of volcanic eruption and sea storms

Background

It is not clear, if modern Konik Polski horses have retained the ability to identify sounds in terms of danger. The aim of the study was to identify differences in their behaviour in response to the reproduction of volcanic eruption and sea storm sounds, assumed to be unfamiliar to these horses, as compared to their response to a thunderclap sound, considered by the horses as potentially dangerous. The study included 13 adult mares of the Konik Polski breed, kept under a free-range system. Their behavioural responses to the reproduction of the three natural sounds with an intensity of over 50 dB, were registered. They were analysed distance of each horse to the central point of the pasture and to the exit from the enclosure, and time and/or frequencies of elements of behaviour categorised as: increased anxiety (walking, trotting and cantering), vigilance (snoring, vocalisation, high head position, high tail position, sticking together), foraging (time of grazing), comfort (playing, examining the surroundings, sniffing), maintenance of hygiene (rubbing against objects, auto- or allogrooming, rolling) and resting. The obtained data were analysed by the Dwass, Steel and Critchlow-Fligner method using the SAS program.

Results

Most of analysed elements increased in response to reproduced sounds and decreased after sounds were stop playing (p < 0.05), however, they were no significant differences in general response to each studied sound.

Conclusions

The responses of horses to similar sounds of both known and unknown origins, i.e. the sound of a thunderstorm, sea storm and volcanic eruption, are similar. The sound stimuli applied were not too stressful for the horses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03314-4.