Abstract: Analysis of heart rate variability (HRV) is a noninvasive approach for investigating the sympathovagal balance of the autonomic nervous system. In recent years, HRV has been increasingly evaluated in animal research. In horses, it has been suggested that basal resting conditions can be achieved by restraining them. The aim of this study was to verify how restriction of movement influences HRV i2n horses. Ten healthy standardbred mares were used to measure the electrocardiographic signal under 2 conditions: free to move in the stall and restrained in the stock. Results indicate that the restriction of movement is associated with increased nervous system sympathetic activity not consistent with resting conditions.

Abstract: A good horse-rider ‘match’ is important in the context of equine welfare. To quantify the influence of repetition and horse-rider matching on the stress of horses encountering challenging objects, 16 Warmblood horses were ridden in a test-setting on three occasions. On each occasion the horse was ridden by a different rider and was challenged by three objects (A–C). Heart rate (HR), heart rate variability (HRV) of horse and rider, and behaviour score (BS) of the horse were obtained for each object and as a total for each test. The horse-rider interaction was evaluated with each combination and assessed as ‘matching’ or ‘mismatching’, and the horses were categorised as ‘compliant’, ‘partly-compliant’ or ‘non-compliant’. Horses exhibited a decreased HR (P = 0.015) and a decreased BS (P = 0.004) within and across different tests. ‘Matching’ horse-rider combinations exhibited less stress as indicated by reduced HR (‘match’ 69 ± 10 vs. ‘mismatch’ 72 ± 9, P = 0.001) and BS (‘match’ 1.9 ± 1.1 vs. ‘mismatch’ 3.8 ± 1.4, P = 0.017) of the horse. ‘Compliant’ (68 ± 8, P < 0.001) and ‘partly-compliant’ (71 ± 9, P = 0.002) horses had significantly lower HR than ‘non-compliant’ (75 ± 9) animals. The findings of the study indicate that HR and BS measurements support a subjective ‘match’ diagnosis and HR measurement may be a valuable tool in assessing horse compliance.

Abstract: Abstract Stress is a generic concept describing the body's reaction to external stimuli, including both physiological and psychological factors. Therefore, by definition, the assessment of psychological stress in the exercising horse encompasses the problem of teasing apart the psychological and physiological factors both of which result in stress responses. The present study reviews the existing literature on various measures of stress taken specifically in the context of equitation science. Particular attention has been paid to short-term effects, and commonly used measurements of short-term stress include heart rate, a number of heart rate variability parameters, blood or saliva cortisol levels, eye temperature, and various behaviour parameters including in particular behaviour patterns presumably indicative of conflict with the rider's/trainer's aids. Inspection of the individual studies' results revealed that disagreement between these different measures of stress is commonplace. For physiological parameters, the largest proportion of agreement (i.e. both parameters simultaneously indicated either higher, insignificant or lower stress compared to a control treatment) was found for heart rate and heart rate variability parameters, while generally limited agreement was found for cortisol. It appears that cortisol levels may not be particularly useful for assessing/assessment of the valence of a situation in the exercising horse as cortisol levels are predominantly linked to activation and exercise levels. Although heart rate variability parameters reflect in theory more closely sympathovagal balance compared to cortisol levels, great care has to be taken regarding the use of appropriate time-frames, appropriate raw data correction methods as well as the use of appropriate equipment. In spite of its wide-spread and apparently successful use, popular equipment may in fact not be accurate enough under field conditions. Eye temperature is another promising parameter for assessment of psychological stress, but the technique is likewise susceptible to application errors. Given the high susceptibility of physiological parameters to errors at various experimental stages, behavioural rather than physiological parameters may in fact provide more accurate measures of valence when conducting experiments in the exercising horse. Behavioural parameters that appear to be particularly practical in assessing stress in ridden horses' behaviour are associated with frequencies of behaviour indicative of conflict. However, while increased frequencies of are a good indicator of stress, the absence of conflict behaviour does not provide proof of the absence of stress due to the possible occurrence of conditions such as Learned Helplessness. In future studies, the above issues should be taken into consideration when designing experiments to assess psychological stress in ridden horses.

Abstract: Abstract In the study of animal emotions, emotional valence has been found to be difficult to measure. Many studies of farm animals' emotions have therefore focussed on the identification of indicators of strong, mainly negative, emotions. However, subtle variations in emotional valence, such as those caused by rather moderate differences in husbandry conditions, may also affect animals' mood and welfare when such variations occur consistently. In this study, we investigated whether repeated moderate aversive or rewarding events could lead to measurable differences in emotional valence in young, weaned pigs. We conditioned 105 female pigs in a test arena to either a repeated startling procedure (sudden noises or appearances of objects) or a repeated rewarding procedure (applesauce, toy and straw) over 11 sessions. Control pigs were also regularly exposed to the same test arena but without conditioning. Before and after conditioning, we measured heart rate and its variability as well as the behavioural reactions of the subjects in the test arena, with a special focus on detailed acoustic analyses of their vocalisations. The behavioural and heart rate measures were analysed as changes compared to the baseline values before conditioning. A limited number of the putative indicators of emotional valence were affected by the conditioning. We found that the negatively conditioned pigs showed changes that were significantly different from those in control pigs, namely a decrease in locomotion and an increase in standing. The positively conditioned pigs, however, showed a stronger increase in heart rate and a smaller decrease in SDNN (a heart rate variability parameter indicating changes in autonomic regulation) compared to the controls. Compared to the negatively conditioned pigs, the positively conditioned pigs produced fewer vocalisations overall as well as fewer low-frequency grunts but more high-frequency grunts. The low-frequency grunts of the negatively conditioned pigs also showed lower frequency parameters (bandwidth, maximum frequency, 25% and 50% quartiles) compared to those of the positively conditioned pigs. In any of the statistically significant results, the conditioning accounted for 1.5–11.9% of variability in the outcome variable. Hence, we conclude that repeated moderate aversive and rewarding events have weak but measurable effects on some aspects of behaviour and physiology in young pigs, possibly indicating changes in emotional valence, which could ultimately affect their welfare. The combination of ethophysiological indicators, i.e., the concurrent examination of heart rate measures, behavioural responses and especially vocalisation patterns, as used in the current study, might be a useful way of examining subtle effects on emotional valence in further studies.

Abstract: Horse trainers often report that lowering the height of a horse's head so the poll is below the height of the withers can induce a calming effect during training. Four groups of horses were used in a 2-part study to investigate the behavioral and physiological effects of head lowering in horses. In Part 1, Group A had no experimental stimuli applied and horses in Group B were trained to lower their heads when presented with a specific stimulus by the handler. The stimulus for head lowering was the application of downward pressure on the headcollar via the lead rope until the horse lowered its head such that its lips were approximately at mid-cannon (third metacarpal) height, whereupon the pressure was released. The stimulus was applied again if the horse raised its head during the 300-second test period. In Part 2, Groups C and D were aroused until their heart rates exceeded 100 beats per minute (bpm). Group C had no further experimental stimuli applied whereas Group D lowered their heads as a response to the above stimulus for a period of 300 seconds. Repeated measures analysis showed that there was no difference between the heart rate of Groups A and B or Groups C and D but that the heart rate of Groups A and B were lower than Groups C and D during the 300-second post-arousal (P < 0.001). The horses in Groups A and B were more likely to contact the handler (P < 0.001), exhibit licking and chewing (P < 0.001), rest a hindleg (P < 0.001), and sniff the ground (P < 0.001) than those in Groups C and D. The number of stimuli required to maintain the head in a lowered position was greatest during the first 30 seconds (P = 0.012 and P < 0.001, Parts 1 and 2, respectively). The current study has shown that head lowering in horses does not influence cardiac responses, even after the horses had been aroused to have their heart rates above 100 bpm. Therefore, it is not a method that will aid in calming an aroused horse in training. Contrary to popular belief, there was no association with licking-and-chewing and head lowering, nor with these behaviors and response acquisition.