Acute changes in oxytocin predict behavioral responses to foundation training in horses

Oxytocin in horse saliva: validation of a highly sensitive assay and a pilot report about changes in equine gastric ulcer syndrome

BACKGROUND

Equine gastric ulcer syndrome (EGUS) is a frequent disease in horses that comprises two different entities: equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD). This disease considerably reduces the quality of life of affected horses and can negatively affect performance. Saliva contains biomarkers, such as oxytocin, that have been used as a welfare indicator and can develop a function as a protective factor against stress-induced changes in gastric function due to its gastric antisecretory and antiulcer effects. The objective of this work was to evaluate changes in salivary oxytocin concentrations in healthy and EGUS horses. For this purpose, an immunoassay based on AlphaLISA technology was validated for the quantification of salivary oxytocin and applied in a total of 102 horses divided into 5 groups: 25 with both EGUS, 23 with only EGGD, 21 with only ESGD, 19 horses with other diseases, and 14 healthy horses.

RESULTS

The analytical validation of the method showed good precision and linearity under dilution. Salivary oxytocin concentrations in healthy horses were higher compared to horses with both ESGD and EGGD and only EGGD. Salivary oxytocin concentrations in horses with only ESGD were higher compared to horses with both ESGD and EGGD and horses with only EGGD. In addition, salivary oxytocin concentrations in horses with other diseases different from ESGD were significantly increased compared to horses with both ESGD and EGGD and horses with only EGGD.

CONCLUSIONS

This report validates a new assay that can measure oxytocin in saliva in horses in a precise and accurate way. The lower oxytocin values in horses with EGGD and both EGGD and ESGD than in horses with ESGD, horses with other diseases, and healthy horses could indicate a possible relation of oxytocin with this disease.

Living the good life? A systematic review of behavioural signs of affective state in the domestic horse (Equus caballus) and factors relating to quality of life. Part 2: Horse-human interactions

Quality of life is dependent upon the extent to which behavioural needs are met, and the balance between pleasant and unpleasant lifetime experiences. In Part II of this systematic review, articles (n = 109) relating to horse-human interactions were reviewed to identify behavioural evidence of their positive or negative impact on the horse. The number of articles (n = 22) relating to the recognition of pain in horses, indicated the importance of identifying health issues, which are also likely to increase the aversiveness of interactions. These and articles relating to emotional reactivity testing in horses (n = 19), the behaviour of horses during handling and management procedures (n = 17), behaviour of the horse when ridden (n = 17), non-procedural horse-human interactions (n = 13), horse behaviour during transportation (n = 12) and behaviour during training other than when ridden (n = 9) were reviewed. During most interactions, horse behaviour is controlled and/or restricted by the human, masking negative or positive signs, and may be confounded by factors including fear and individual differences. In situations involving freedom of movement, positive experiences of horses with humans were associated with approach behaviour, negative ones with avoidance, but training could affect both. Undoubtedly, change is needed to reduce the extent to which interactions with humans are unpleasant for the horse. Only when the needs of the horse are fulfilled and interactions with humans are predominantly pleasurable will their quality of life improve.

Systematic review: pain, cognition, and cardioprotection-unpacking oxytocin's contributions in a sport context

Introduction

This systematic review investigates the interplay between oxytocin and exercise; in terms of analgesic, anti-inflammatory, pro-regenerative, and cardioprotective effects. Furthermore, by analyzing measurement methods, we aim to improve measurement validity and reliability.

Methods

Utilizing PRISMA, GRADE, and MECIR protocols, we examined five databases with a modified SPIDER search. Including studies on healthy participants, published within the last 20 years, based on keywords "oxytocin," "exercise" and "measurement," 690 studies were retrieved initially (455 unique records). After excluding studies of clinically identifiable diseases, and unpublished and reproduction-focused studies, 175 studies qualified for the narrative cross-thematic and structural analysis.

Results

The analysis resulted in five categories showing the reciprocal impact of oxytocin and exercise: Exercise (50), Physiology (63), Environment (27), Social Context (65), and Stress (49). Exercise-induced oxytocin could promote tissue regeneration, with 32 studies showing its analgesic and anti-inflammatory effects, while 14 studies discussed memory and cognition. Furthermore, empathy-associated OXTR rs53576 polymorphism might influence team sports performance. Since dietary habits and substance abuse can impact oxytocin secretion too, combining self-report tests and repeated salivary measurements may help achieve precision.

Discussion

Oxytocin's effect on fear extinction and social cognition might generate strategies for mental training, and technical, and tactical development in sports. Exercise-induced oxytocin can affect the amount of stress experienced by athletes, and their response to it. However, oxytocin levels could depend on the type of sport in means of contact level, exercise intensity, and duration. The influence of oxytocin on athletes' performance and recovery could have been exploited due to its short half-life. Examining oxytocin's complex interactions with exercise paves the way for future research and application in sports science, psychology, and medical disciplines.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=512184, identifier CRD42024512184.

Changes in the blood redox status of horses subjected to combat training

Combat training of police horses, involving physical activity in the presence of environmental stressors, poses a risk of oxidative stress. This study compared the oxidative imbalance after combat training in horses in the regular police service and in horses that had just been schooled. Blood collection was performed immediately after training and after 16 h rest. The activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and total antioxidant status (TAS) were determined as the markers of enzymatic antioxidant defence. At the same time, lipid peroxidation (TBARS) and protein carbonylation (Carb) were assessed as oxidation biomarkers. Additionally, oxidative imbalance indexes such as SOD/CAT, SOD/GPx, TBARS/TAS and TBARS/GPx were calculated. Animals during schooling had significantly lower SOD activity in erythrocytes than those experienced. CAT activity in erythrocytes was insignificantly higher immediately after training than during recovery. The SOD/GPx ratio was higher in experienced animals, which may reflect the intra-erythrocyte imbalance between enzymes producing and degrading hydrogen peroxide towards the first one. The concentration of carbonyl groups was significantly higher after the combat training compared to the recovery period in all horses. In inexperienced animals slight increase in TBARS/TAS and TBARS/GPx indexes were observed during the recovery time after exercises, contrary to experienced horses, in which these markers decreased slightly. These results suggest that the oxidative imbalance in inexperienced horses, although less pronounced just after combat training, was more prolonged as compared to horses in regular service.

Changes in salivary oxytocin in response to biologically-relevant events in farm animals: method optimization and usefulness as a biomarker

Although best known for its established role in mediating parturition and lactation, the highly-conserved neuropeptide hormone oxytocin also mediates a range of social and stress-buffering processes across mammalian species. Measurements of peripheral oxytocin in plasma have long been considered the gold standard, but there is increasing interest in developing methods to detect oxytocin non-invasively in saliva. Here we present an analytical and biological validation of a novel method to measure salivary oxytocin (sOXT) in an under-studied research group: farm animals. Given their similarities with humans in physiology and brain, methods that can identify valued social contexts and social relationships for farm animals and investigate their function have implications for clinical research as well as for animal welfare science. However, current methods to measure sOXT vary greatly in terms of sample collection, pre-measurement processing and measurement and more rigorous standardization and validation of methods is critical to determine the utility of sOXT as a biomarker of salient social events and related emotions. We optimized a method for extracting sOXT in pigs and horses and measured sOXT in extracted samples using a commercially available enzyme-immunoassay. Extracted samples were within acceptable ranges for precision (CVs < 15.2%), parallelism and recovery (94%-99%) in both species. Salivary oxytocin increased in samples collected during birth in pigs (Friedmans, p = 0.02) and horses (Wilcoxon, p = 0.02). Salivary oxytocin tended to decrease in sows after a 90-min separation from their piglets (Wilcoxon, p = 0.08). We conclude that sOXT can be reliably linked to physiological events that are mediated by the oxytocinergic system in farm animals, but that more research is needed to determine whether sOXT is a reliable trait marker for more general oxytocin system activation in response to salient social events. Future research should characterize how individual attributes and salivary parameters influence sOXT measurement and should emphasize reporting of analytical and biological validations to increase acceptance of non-invasive methods.

Measuring heart rate variability using a heart rate monitor in horses (Equus caballus) during groundwork

Measuring physiological parameters of stress in horses during groundwork, for example when involved in equine-assisted interventions, is important to gain insight into the stress levels of the horses. Heart rate and heart rate variability can be used as physiological indicators of stress in horses. Heart rate monitors could be easily incorporated into practice, as they are not expensive and easy to use. However, it is questionable whether heart rate monitors present accurate heart rate variability results in exercising horses, similar to electrocardiograms. The aim of this study was to determine the accuracy of heart rate monitors for the assessment of heart rate variability in horses during groundwork exercise. Simultaneous telemetric electrocardiograms (Televet) and heart rate monitor (Polar H10 transmitter and M430 receiver, Hylofit electrodes) recordings were performed on 28 horses (15 mares and 13 geldings). Results indicate that the heart rate monitor accurately determined heart rate and time-domain heart rate variability parameters when compared to electrocardiograms during both baseline and groundwork conditions. As expected, heart rate significantly increased and the heart rate variability significantly decreased during groundwork compared to baseline conditions. This indicates that the heart rate monitor can be used to accurately determine heart rate variability during groundwork.