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Löckener, S., Reese, S., Erhard, M., & Wöhr, A. - C. (2016). Pasturing in herds after housing in horseboxes induces a positive cognitive bias in horses. Journal of Veterinary Behavior: Clinical Applications and Research, 11, 50–55.
Abstract: Abstract Horses are kept in various housing systems, for example, with conspecifics in horse pens or singly in horseboxes, with or without pasturing. To provide appropriate living conditions for horses, it is necessary to know in which conditions they feel well or unwell. Here, a cognitive bias assessment provides information about an individual's affective state and its well-being. When a positive affective state prevails, animals tend to judge optimistically in ambiguous situations. When a negative affective state prevails, animals judge pessimistically in unclear situations. In the present study, we trained horses on a spatial discrimination task and evaluated their judgment of ambiguous locations when they had access to pastures and contact to conspecifics versus when they were kept singly in horseboxes. Ten days of pasturing and contact with conspecifics after being kept singly in horseboxes for 6 months induced a positive cognitive bias in the horses. We suggest that horses need to act out certain behaviors like exploration, social interaction, play, or grooming to fulfill their needs. After a time in which they were individually in horseboxes without pasturing and access to the herd, they seem to have a positive cognitive bias once they have access to pastures and conspecifics. This positive cognitive bias effect seems to disappear over time, as horses appear to adapt to the circumstances.
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Vitale, V., Balocchi, R., Varanini, M., Sgorbini, M., Macerata, A., Sighieri, C., et al. (2013). The effects of restriction of movement on the reliability of heart rate variability measurements in the horse (Equus caballus). J. Vet. Behav., 8(5), 400–403.
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.
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Yeon, S. C. (2012). Acoustic communication in the domestic horse (Equus caballus). Journal of Veterinary Behavior: Clinical Applications and Research, 7(3), 179–185.
Abstract: Equine vocalization and acoustic sounds can communicate a horse’s emotional state, physiological state, and situation to other individuals, including other horses and humans. These vocalizations and acoustic sounds can be divided into several types. The whinny, nicker, squeal, blow, snore, snort, roar, and groan are typical types of horse vocalizations and acoustic sounds. The sound localization thresholds of horses are markedly poorer than those of other large mammals, such as humans and elephants. The audiogram of horse has shown their best sensitivity and hearing range in which it perceives sound. Laryngeal diseases, such as laryngeal hemiplegia, dorsal displacement of the soft palate, and alar fold paralysis, can cause laryngeal sounds in the upper airway. The analyses of horses’ vocalizations and laryngeal sounds that are reviewed in this article were conducted with computer-aided analysis programs using spectrograms and spectra that evaluate several parameters, including amplitude, fundamental frequency, duration, and formants. Laryngeal sound analysis could be a useful method for diagnosing upper airway diseases. This article presents a review of the literature describing scientific analyses of horse vocalizations and acoustic sounds to elucidate equine acoustic communications and aid in the development of horse-human bonds.
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Waldern, N. M., Wiestner, T., Ramseier, L. C., Amport, C., & Weishaupt, M. A. (2013). Effects of shoeing on limb movement and ground reaction forces in Icelandic horses at walk, tölt and trot. Vet. J., 198, Supplement 1, e103–e108.
Abstract: Abstract Tölt is a symmetric four-beat gait with a speed range extending into that of trot and canter. Specific shoeing methods, such as unnaturally high and long hooves, are used to enforce individual gait predisposition. The aim of this study was to assess the consequences of this shoeing style on loading and movement of the limbs at walk, tölt and trot, and at different velocities. Simultaneous kinetic and kinematic gait analysis was carried out at walk (1.4 m/s) and at two tölting and trotting speeds (3.3 m/s and 3.9 m/s) on an instrumented treadmill. Thirteen sound Icelandic horses were first measured with high, long front hooves (SH) and, 1 week later, after trimming the hooves according to standard shoeing principles (SN). Comparing SH with SN, front hooves had 21 ± 5 mm longer dorsal hoof walls, and the shoeing material per hoof was 273 ± 50 g heavier. In all three gaits, gait quality, as it is currently judged, was improved with SH due to a lower stride rate, a longer stride length and a higher, but not wider, forelimb protraction arc, which were also positively associated with speed. Forelimb–hind limb balance remained unchanged, but limb impulses were higher. Apart from an increase of ⩽2.2% in the forelimbs at the faster speed of both tölt and trot, SH had little influence on vertical peak forces.
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Munsters, C. C. B. M., Visser, K. E. K., van den Broek, J., & Sloet van Oldruitenborgh-Oosterbaan, M. M. (2012). The influence of challenging objects and horse-rider matching on heart rate, heart rate variability and behavioural score in riding horses. The Veterinary Journal, 192(1), 75–80.
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.
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Aurich, J., Wulf, M., Ille, N., Erber, R., von Lewinski, M., Palme, R., et al. (2015). Effects of season, age, sex and housing on salivary cortisol concentrations in horses. Domest. Anim. Endocrinol., .
Abstract: Abstract Analysis of salivary cortisol is increasingly used to assess stress responses in horses. Since spontaneous or experimentally induced increases in cortisol concentrations are often relatively small for stress studies proper controls are needed. This requires an understanding of factors affecting salivary cortisol over longer times. In this study, we have analysed salivary cortisol concentration over 6 mo in horses (n = 94) differing in age, sex, reproductive state and housing. Salivary cortisol followed a diurnal rhythm with highest concentrations in the morning and a decrease throughout the day (P < 0.001). This rhythm was disrupted in individual groups on individual days; however, alterations remained within the range of diurnal changes. Comparison between months showed highest cortisol concentrations in December (P < 0.001). Cortisol concentrations increased in breeding stallions during the breeding season (P < 0.001). No differences in salivary cortisol concentrations between non-pregnant mares with and without a corpus luteum existed. In stallions, mean daily salivary cortisol and plasma testosterone concentration were weakly correlated (r = 0.251, P < 0.01). No differences in salivary cortisol between female and male young horses and no consistent differences between horses of different age existed. Group housing and individual stabling did not affect salivary cortisol. In conclusion, salivary cortisol concentrations in horses follow a diurnal rhythm and are increased in active breeding sires. Time of the day and reproductive state of the horses are thus important for experiments that include analysis of cortisol in saliva.
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de Oliveira, K., Soutello, R. V. G., da Fonseca, R., Costa, C., de L. Meirelles, P. R., Fachiolli, D. F., et al. (2015). Gymnastic Training and Dynamic Mobilization Exercises Improve Stride Quality and Increase Epaxial Muscle Size in Therapy Horses. Journal of Equine Veterinary Science, 35(11), 888–893.
Abstract: The objective was to evaluate the efficacy of gymnastic training (GYM) and dynamic mobilization exercises (DMEs) on stride length (SL) and epaxial muscle size in therapy horses. Nine cross-bred hippotherapy horses that performed three, 25-minute therapeutic riding sessions per week throughout the study period were randomly assigned to three experimental groups: a control group in which the horses were sedentary with no additional physical activity; a group that performed DMEs; and a group that performed both DMEs and additional GYM including pelvic tilting, backing, turning in small circles, and walking over a raised rail to strengthen the abdominal and pelvic stabilizer muscles. The exercises were performed 3Â days per week for 3Â months, with evaluations at the start and end of the study. Stride quality was assessed by measuring SL and tracking distance (TD). Epaxial muscle size was monitored by ultrasonographic measurement of m. longissimus dorsi (LD) thickness and m. multifidi (MM) cross-sectional area. Paired t tests were used to compare within groups across time, and between groups were detected using analysis of variance with Tukey post hoc test. When walking at 1.3Â m/s, SL and TD at walk increased significantly (P < .05) in horses subjected to GYM. Thickness of LD did not change in any group, but cross-sectional area of MM increased significantly by 3.55Â cm2 (DME) and 3.78Â cm2 (GYM). It was concluded that GYM training improved stride quality and DME-stimulated MM hypertrophy which has been shown to improve intervertebral joint stability in other species.
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Covalesky, M. E., Russoniello, C. R., & Malinowski, K. (1992). Effects of show-jumping performance stress on plasma cortisol and lactate concentrations and heart rate and behavior in horses. Journal of Equine Veterinary Science, 12(4), 244–251.
Abstract: Summary Effects of show jumping competition on stress levels in horses was examined. Twenty-six homes were sampled in both show and farm environments from three levels of show experience schooling, (least experience, n=11); intermediate, (moderate experience, n=6); open, (most experience, n=9). Blood samples were taken at 6 time points; 3 at the horse show and 3 at the home farm (baseline at rest, pre-schooling and post-performance over a jump course). Stress responses were assessed through comparison of the behavioral response of the horses (determined by a subjective scoring system) to plasma cortisol (F) concentrations. Physical exertion was evaluated by heart rate (HR) and plasma lactate (L) concentrations. Schooling jumpers displayed higher baseline F concentrations than open jumpers (83g±9.2 vs 46.4±10.2 ng/ml, respectively; p<.05); but not when compared to intermediate jumpers (66.2 ± 13.7 ng/ml; p>.05) at the horse show. At the farm, there were no differences in F concentrations between experience levels at a time point (p<.05). Least experienced horses displayed higher F values at rest at the show compared to the home farm. At the show, open jumpers had higher L concentrations post-exercise compared to intermediate horses (40.3±3.4 vs 25.5±4.0 mg/dL, respectively; p<.05); but were not different compared to schooling jumpers (34.8±2.0 mg/dL; p>.05). There were no differences in heart rates or behavior score between experience levels at specific time points at either the show or farm (p>.05). Low positive correlations were found between HR and F (r=.24, p<.05); HR and L (r-.48, p<.05); and HR and behavior (r=.22, p<.05). Results suggest that conditioned jumpers that have previously been exposed to horse show environments do not appear stressed during acute show-jumping competition.
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Rochais, C., Henry, S., Fureix, C., & Hausberger, M. (2016). Investigating attentional processes in depressive-like domestic horses (Equus caballus). Behavioural Processes, 124, 93–96.
Abstract: Abstract Some captive/domestic animals respond to confinement by becoming inactive and unresponsive to external stimuli. Human inactivity is one of the behavioural markers of clinical depression, a mental disorder diagnosed by the co-occurrence of symptoms including deficit in selective attention. Some riding horses display ‘withdrawn’ states of inactivity and low responsiveness to stimuli that resemble the reduced engagement with their environment of some depressed patients. We hypothesized that ‘withdrawn’ horses experience a depressive-like state and evaluated their level of attention by confronting them with auditory stimuli. Five novel auditory stimuli were broadcasted to 27 horses, including 12 ‘withdrawn’ horses, for 5 days. The horses’ reactions and durations of attention were recorded. Non-withdrawn horses reacted more and their attention lasted longer than that of withdrawn horses on the first day, but their durations of attention decreased over days, but those of withdrawn horses remained stable. These results suggest that the withdrawn horses’ selective attention is altered, adding to already evidenced common features between this horses’ state and human depression.
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Watanabe, N. M., Stahlman, W. D., Blaisdell, A. P., Garlick, D., Fast, C. D., & Blumstein, D. T. (2012). Quantifying personality in the terrestrial hermit crab: Different measures, different inferences. Behav. Process., 91(2), 133–140.
Abstract: There is much interest in studying animal personalities but considerable debate as to how to define and evaluate them. We assessed the utility of one proposed framework while studying personality in terrestrial hermit crabs (Coenobita clypeatus). We recorded the latency of individuals to emerge from their shells over multiple trials in four unique manipulations. We used the specific testing situations within these manipulations to define two temperament categories (shyness-boldness and exploration-avoidance). Our results identified individual behavioral consistency (i.e., personality) across repeated trials of the same situations, within both categories. Additionally, we found correlations between behaviors across contexts (traits) that suggested that the crabs had behavioral syndromes. While we found some correlations between behaviors that are supposed to measure the same temperament trait, these correlations were not inevitable. Furthermore, a principal component analysis (PCA) of our data revealed new relationships between behaviors and provided the foundation for an alternate interpretation: measured behaviors may be situation-specific, and may not reflect general personality traits at all. These results suggest that more attention must be placed on how we infer personalities from standardized methods, and that we must be careful to not force our data to fit our frameworks.
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