Biology subjects

Bourguignon, H.

Publications and source records attributed to Bourguignon, H..

2 recordsLinked to original sources

bioRxiv2026

Sleep quality and quantity and their associations with age, salivary cortisol and abnormal behaviours: a preliminary field study in racing thoroughbreds.

Sleep plays a key role in both physical recovery and welfare. However, sleep patterns remain poorly documented in animals, particularly in athletic horses. This study aimed to provide a detailed description of sleep quantity and quality in training Thoroughbred racehorses and to investigate their relationships with age, abnormal behaviours, and cortisol. Thirteen Thoroughbreds (2-7 years old) were continuously monitored in their home environment over three consecutive days. An ethogram was used to quantify the two main phases of sleep: Non Rapid Eye Movement sleep (NREM) and Rapid Eye Movement sleep (REM), as well as sleep interruptions (from day 1 at 12:00 a.m. to day 3 at 12:00 a.m.). Sleep Quality Indices (SQI), defined as the quantity of sleep divided by the number of sleep interruptions (SI), were calculated. Behavioural observations of four indicators of poor welfare (alertness, stereotypies, inactivity, aggressiveness towards humans) were performed using scan sampling, and salivary cortisol was measured each morning. Linear models were used to assess the links between sleep quantity and quality, age, mean cortisol, and abnormal behaviours. Sleep quantity was significantly associated with age: positively for total NREM sleep (ANOVA: {chi}{superscript 2} = 5.26, p < 0.05) and, negatively for total REM sleep (ANOVA: {chi}{superscript 2} = 4.46, p <0.05) and total recumbency duration (ANOVA: {chi}{superscript 2} = 5.68, p < 0.05), suggesting an age-related shift favouring NREM over REM. Morning cortisol concentrations and the frequency of abnormal behaviours were significantly higher in horses with lower sleep quality (cortisol: Total SQI, ANOVA: F = 5.26, p < 0.05; Combined SQI, ANOVA: F = 5.40, p < 0.05; abnormal behaviours: Total SQI, ANOVA: F = 4.07, p = 0.074), pointing to a potential link between stress or altered welfare and poorer sleep quality. These findings suggest that, whilst the type and duration of equine sleep may be mainly affected byage, sleep quality is associated with both cortisol levels and the expression of abnormal behaviours, indicating that poor sleep quality may be linked to poor welfare in this population of horses. Thus, sleep appears to be closely linked with racehorse welfare, highlighting the need for further investigation into how it is influenced by factors such as husbandry, training load, recovery, and performance.

animal behavior and cognition↗

bioRxiv2025

Exploring the association between stress-related hormonal changes, behaviours and facial movements after a trotting exercise in French Standardbred

Physical exercise can act as a physiological and a mental stressor. Monitoring exercise-induced stress is therefore essential to understand racehorses responses to effort and ensuring their welfare. Stress perceived by the horse during physical activity can be measured using various indicators, including stress-related hormones such as cortisol and adrenaline, and other neuromodulators such as serotonin, all involved in the stress response and its regulation. Another approach to assess physiological and emotional responses to stimuli such as exercise is through behaviours and facial movements. In this study, we aimed to 1) evaluate the changes in these three hormones following a trotting exercise, 2) determine the changes in behaviour and facial movements in response to the same exercise and 3) investigate a potential relationship between hormonal variations and specific behavioural patterns that could serve as indicators of exercise-induced stress in horses. Fourteen French Standardbred horses from two stables were monitored over one day. On the morning they performed a trotting exercise. Behaviours and facial movements were recorded via video for 2min30 both before and just after exercise. Saliva and blood samples were collected at four time points: before exercise, just after exercise, 1h post-exercise and 24h post-exercise to assess the concentration of salivary cortisol, serum concentration of adrenaline and serotonin. Results showed significant post-exercise increases in all three hormones with peak concentrations observed immediately after exercise (general mixed models, p<0.05), and elevated cortisol and adrenaline levels persisting one hour later (general mixed models, p<0.05). In terms of behaviours, horses exhibited higher frequencies of facial movements and especially mouth movements after exercise than before (MANOVA, F=5.85, p<0.01). Moreover, increases in serotonin and adrenaline concentrations were positively associated with agitation-related behaviours (pawing and head turning) and mouth movements (general linear models, p<0.01). This association may reflect a rebound effect of bit pressure on the mouth, which may be greater with greater perceived stress during exercise, and the increased arousal effects of adrenaline, and to a lesser extent, serotonin. Overall, our findings suggest that a behavioural profile characterised by increased agitation and mouth movements may serve as a useful non-invasive indicator of exercise-induced stress in French Standardbreds.

animal behavior and cognition↗