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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.
Keywords: horse; cortisol; diurnal rhythm; reproduction; housing
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Becker-Birck, M., Biau, S., Aurich, C., Möstl, E., Ille, N., & Aurich, J. (2012). Heart rate and heart rate variability in the horse and its rider: different responses to training and a public equestrian performance. In K. Krueger (Ed.), Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing.
Abstract: While detailed information exists on the cardiovascular response of horses to racing or endurance, much less is known about cardiovascular function of the rider in equestrian sports. Combined analysis of the horse-rider-team has not been investigated so far. In this study, we have analyzed changes in heart rate and heart variability (HRV) variables SDRR (standard deviation of beat-to-beat interval) and RMSSD (root mean square of successive beat-to-beat intervals) both in well-trained horses (n=9) and their highly experienced riders (n=7) during the airs above the ground (sauteurs en liberté of the Cadre noir de Saumur) at a public performance and at an identical, but non-public training session, both lasting for exactly 7 min. Heart rate in the horses and riders increased during the airs above the ground, both in training and in the public performance (p<0.001 over time). In the horses, this increase did not differ between training and public performance (training: from 35±6 in the stable to 97±17 beats/min during riding, performance: from 43±13 to 103±13 beats/min, respectively). In contrast, in the riders, the increase in heart rate was significantly more pronounced (p<0.01) during the public performance (basal value 91±10, maximum 150±15 beats/min) than during training (basal value 94±10, maximum 118±12 beats/min). With regard to HRV in horses, overall SDRR did not change significantly over time and did not differ significantly between training and performance. RMSSD decreased during both training and performance to the same extent, indicating a decrease in parasympathetic (vagal) tone. In the riders, both HRV variables decreased significantly during riding (p<0.001) and for SDRR the decrease was more pronounced (p<0.05) during an equestrian performance compared to a training session. During the performance SDRR decreased from a basal value of 5.0±1.5 to a minimum of 3.2±0.6 msec while respective values for the training session were 5.3±1.1 and 2.3±1.1 msec. Both a public performance and an identical training session of the airs above the ground in the ridden horse caused an increase in heart rate and a decrease in HRV variables. While increases in heart rate are mainly caused by physical activity, decreases in HRV also indicate a stress response. The cardiovascular response in the horses did not differ between a training session and a public performance but clear differences could be demonstrated in the riders. During a public performance, the increase in heart rate and decrease in SDRR were more pronounced than during a similar training session. In conclusion, the presence of an audience thus causes more pronounced sympathoadrenal activity in experienced riders than the same equestrian tasks ridden without spectators present. In contrast, the presence of an audience was without effect on sympathoadrenal activity in experienced horses. KW -
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Becker-Birck, M., Schmidt, A., Wulf, M., Aurich, J., von der Wense, A., Möstl, E., et al. (2013). Cortisol release, heart rate and heart rate variability, and superficial body temperature, in horses lunged either with hyperflexion of the neck or with an extended head and neck position. Journal of Animal Physiology and Animal Nutrition, 97(2), 322–330.
Abstract: Bringing the head and neck of ridden horses into a position of hyperflexion is widely used in equestrian sports. In our study, the hypothesis was tested that hyperflexion is an acute stressor for horses. Salivary cortisol concentrations, heart rate, heart rate variability (HRV) and superficial body temperature were determined in horses (n = 16) lunged on two subsequent days. The head and neck of the horse was fixed with side reins in a position allowing forward extension on day A and fixed in hyperflexion on day B. The order of treatments alternated between horses. In response to lunging, cortisol concentration increased (day A from 0.73 ± 0.06 to 1.41 ± 0.13 ng/ml, p < 0.001; day B from 0.68 ± 0.07 to 1.38 ± 0.13 ng/ml, p < 0.001) but did not differ between days A and B. Beat-to-beat (RR) interval decreased in response to lunging on both days. HRV variables standard deviation of RR interval (SDRR) and RMSSD (root mean square of successive RR differences) decreased (p < 0.001) but did not differ between days. In the cranial region of the neck, the difference between maximum and minimum temperature was increased in hyperflexion (p < 0.01). In conclusion, physiological parameters do not indicate an acute stress response to hyperflexion of the head alone in horses lunged at moderate speed and not touched with the whip. However, if hyperflexion is combined with active intervention of a rider, a stressful experience for the horse cannot be excluded.
Keywords: animal welfare; equitation; stress; training
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Burger, D., Baumgartner, M., Schauer, S. N., Wägeli, S., Aurich, C., & Gerber, V. (2008). Influence of the recipient mare on character traits of adult offspring in a Warmblood embryo transfer program – preliminary results. In IESM 2008.
Abstract: The influence of recipient mares in commercial embryo transfer (ET) programs
on behavior of the ET foals is a matter of great interest and controversial discussion. Presently, no interdisciplinary ethological and reproductive studies on this topic exist. However, empirical experience suggests that behavioral traits of the recipient mare do not influence those of the foal, thus implying a predominantly genetic origin of a horse"s basic character. Aim: The aim of the present study was to investigate the influence of recipient mares on behavioural traits of their ET products. Materials and Methods: Based on records of the embryo transfer program in Warmblood horses since 1990 at the Swiss National Stud, questionnaires concerning behavior, stereotypies and mother-foal-relationship were designed and completed by telephone interview: 18 scientifically assessed questions provided the basis for a linear description (Equine Personality Assessment Questionnaire, Lloyd et al., 2007). They were grouped in a) emotivity, b) social motivation, c) general level of activity, d) stress behavior, e) learning capacity and f) reactions towards humans. Questionnaires were designed for the owners of the ET offspring (minimum of three years of age), the sires, donor mares and the recipient mares. Out of 200 questionnaires, 25 complete ET families have emerged so far and were analysed. All genetic parents were Warmblood horses, as were 23 of the recipient mares, the other two were Franches-Montagnes horses. Results: Comparing the mean values of the four groups (genetic dam and sire, recipient mare and ET product), significant differences were found for the parameters emotivity (sires lower, p<0.001), learning behaviour (recipient mares lower, p<0.05) and activity (recipient mares lower, p<0.05). With only one exception, the multiple variable regression analysis found no significant influence of the recipient mare on the ET product. The only significant effect observed, was that of the social motivation of the recipient mare on the learning capacity of the ET offspring (r2= -0.421, p<0.05). In contrast, numerous significant effects of behavioural traits of the genetic dams and sires on their ET offspring (10 and 8, respectively) were observed. Conclusions: These preliminary results confirm field observations that the influence of the recipient mare does not play an important role in character development of the ET offspring. However, the investigated parameters indicate that the behavioural traits of the genetic parents appear to have a strong influence on the offspring"s behaviour.. This study model promises new achievements in the evaluation of genetic and environmental effects on the behavior of a horse. References Lloyd, AS, Martin, JE, Bornett-Gauci, HLI, Wilkinson, RG (2007). Evaluation of a novel method of horse personality asses |
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Erber, R., Wulf, M., Aurich, J., Becker-Birck, M., Rose-Meierhöfer, S., Möstl, E., et al. (2012). Physiological stress parameters in sport horse mares transferred from group housing to individual stabling. In K. Krueger (Ed.), Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing.
Abstract: Initial equestrian training and especially first mounting of a rider are stressful challenges for young horses (1). Most young horses are raised in groups but, in association with equestrian training, they are commonly transferred to individual stabling in loose boxes. Although, in most stables, visual contact with horses in adjacent boxes is possible, separation from the herd might be an additional stressor. We have studied physiological stress parameters, in 3-year-old sport horse mares (n=8), transferred from a group stable with access to a paddock to individual boxes without paddock. Once stabled in the individual boxes, mares underwent a standard training for young horses. Horses had been accustomed to lunging and tolerating a rider on their back several weeks before the study. Mares were studied from 5 days before to 5 days after changing the stable. Cortisol concentration in saliva, locomotion activity (ALT pedometers), heart rate (HR) and HR variability (RMSSD: root mean square of successive beat-to-beat intervals) were determined. We hypothesized that the change of the stable increases cortisol release and is associated with changes in HR and RMSSD and reduced locomotion. Before mares were moved to individual boxes, cortisol concentration showed a pronounced diurnal rhythm with values around 0.6 ng/ ml in the morning and a continuous decrease throughout the day. When the mares were moved to individual boxes, cortisol concentration increased to 1.8±0.2 ng/ml and did not return to baseline values within 6 h (p<0.05 over time). On subsequent days, a diurnal rhythm was re-established but shifted to a higher level than before. Locomotion activity determined by ALT pedometers was increased for some minutes only after mares has been placed in individual boxes but was only slightly higher than during the time mares spent with the group in a paddock. On days 2-5 in individual boxes, locomotion activity was reduced compared to the group stable. HR increased and the HRV variable RMSSD decreased when mares were separated. In conclusion, separating horses during initial training from their group is an additional stressor, although the stress is less pronounced than induced by other social challenges, e.g. weaning of foals (2). When stabled in individual boxes, mares move less than when kept as a group. Horses kept in a group thus appear to exercise themselves freely, such an effect is absent when the animals are kept individually.
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Schmidt, A., Aurich, J., Möstl, E., Müller, J., & Aurich, C. (2010). Changes in cortisol release and heart rate and heart rate variability during the initial training of 3-year-old sport horses. Horm Behav, 58(4), 628–636.
Abstract: Based on cortisol release, a variety of situations to which domestic horses are exposed have been classified as stressors but studies on the stress during equestrian training are limited. In the present study, Warmblood stallions (n = 9) and mares (n = 7) were followed through a 9 respective 12-week initial training program in order to determine potentially stressful training steps. Salivary cortisol concentrations, beat-to-beat (RR) interval and heart rate variability (HRV) were determined. The HRV variables standard deviation of the RR interval (SDRR), RMSSD (root mean square of successive RR differences) and the geometric means standard deviation 1 (SD1) and 2 (SD2) were calculated. Nearly each training unit was associated with an increase in salivary cortisol concentrations (p < 0.01). Cortisol release varied between training units and occasionally was more pronounced in mares than in stallions (p < 0.05). The RR interval decreased slightly in response to lunging before mounting of the rider. A pronounced decrease occurred when the rider was mounting, but before the horse showed physical activity (p < 0.001). The HRV variables SDRR, RMSSD and SD1 decreased in response to training and lowest values were reached during mounting of a rider (p < 0.001). Thereafter RR interval and HRV variables increased again. In contrast, SD2 increased with the beginning of lunging (p < 0.05) and no changes in response to mounting were detectable. In conclusion, initial training is a stressor for horses. The most pronounced reaction occurred in response to mounting by a rider, a situation resembling a potentially lethal threat under natural conditions.
Keywords: Horse; Initial training; Cortisol; Heart rate variability
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Schmidt, A., Biau, S., Möstl, E., Becker-Birck, M., Morillon, B., Aurich, J., et al. (2010). Changes in cortisol release and heart rate variability in sport horses during long-distance road transport. Domest Anim Endocrinol, 38(3), 179–189.
Abstract: It is widely accepted that transport is stressful for horses, but only a few studies are available involving horses that are transported regularly and are accustomed to transport. We determined salivary cortisol immunoreactivity (IR), fecal cortisol metabolites, beat-to-beat (RR) interval, and heart rate variability (HRV) in transport-experienced horses (N = 7) in response to a 2-d outbound road transport over 1370 km and 2-d return transport 8 d later. Salivary cortisol IR was low until 60 min before transport but had increased (P < 0.05) 30 min before loading. Transport caused a further marked increase (P < 0.001), but the response tended to decrease with each day of transport. Concentrations of fecal cortisol metabolites increased on the second day of both outbound and return transports and reached a maximum the following day (P < 0.001). During the first 90 min on Day 1 of outbound transport, mean RR interval decreased (P < 0.001). Standard deviations of RR interval (SDRR) decreased transiently (P < 0.01). The root mean square of successive RR differences (RMSSD) decreased at the beginning of the outbound and return transports (P < 0.01), reflecting reduced parasympathetic tone. On the first day of both outbound and return transports, a transient rise in geometric HRV variable standard deviation 2 (SD2) occurred (P < 0.01), indicating increased sympathetic activity. In conclusion, transport of experienced horses leads to increased cortisol release and changes in heart rate and HRV, which is indicative of stress. The degree of these changes tended to be most pronounced on the first day of both outbound and return transport.
Keywords: Horse; Transport; Cortisol; Heart rate variability
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Schmidt, A., Möstl, E., Wehnert, C., Aurich, J., Müller, J., & Aurich, C. (2010). Cortisol release and heart rate variability in horses during road transport. Horm. Behav., 57(2), 209–215.
Abstract: Based on plasma cortisol concentrations it is widely accepted that transport is stressful to horses. So far, cortisol release during transport has not been evaluated in depth by non-invasive techniques such as analysis of salivary cortisol and faecal cortisol metabolites. Transport also causes changes in heart rate and heart rate variability (HRV). In this study, salivary cortisol, faecal cortisol metabolites, heart rate and HRV in horses transported by road for short (one and 3.5 h) and medium duration (8 h) were determined. With the onset of transport, salivary cortisol increased immediately but highest concentrations were measured towards the end of transport (4.1 ± 1.6, 4.5 ± 2.6, 6.5 ± 1.8 ng/ml in horses transported for one, 3.5 and 8 h, respectively). Faecal cortisol metabolite concentrations did not change during transport, but 1 day after transport for 3.5 and 8 h had increased significantly (p < 0.01), reflecting intestinal passage time. Compared to salivary cortisol, changes in faecal cortisol metabolites were less pronounced. Heart rate increased and beat-to-beat (RR) interval decreased (p < 0.05) with the onset of transport. Standard deviation of heart rate increased while root mean square of successive RR differences (RMSSD) decreased in horses transported for 3.5 (from 74 ± 5 to 45 ± 6 ms) and 8 h (from 89.7 ± 7 to 59 ± 7 ms), indicating a reduction in vagal tone. In conclusion, transport of horses over short and medium distances leads to increased cortisol release and changes in heart rate and HRV indicative of stress. The degree of these changes is related to the duration of transport. Salivary cortisol is a sensitive parameter to detect transient changes in cortisol release.
Keywords: Horse; Transport; Cortisol; Heart rate variability
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Schmidt, A., Möstl, E., Neuhauser, S., Aurich, J., Müller, J., & Aurich, C. (2008). Changes in heart rate and cortisol release during initial training of three-year-old warmblood sport horse stallions. In IESM 2008.
Abstract: The first weeks of training in young sport horses have been suggested to represent a stressful period and training practises for horses have been questioned recently. So far, only limited data on the stress response of young horses to the initial training are available. Heart rate (HR) provides information on fitness of the horse but is also an indicator of stress or pain. Determination of cortisol metabolites in faeces is a non-invasive technique to determine a prolonged stress response. In our study, three-year-old warmblood sport horse stallions (n=8) were followed through a standardised 10-week classical training programme from lunging to first mounting of a rider and progressing to moderate work. Feed, housing and management were similar for all horses. HR was recorded with a mobile recording System (f810i, Polar, Kempele, Finland) fixed to a girth around the thorax of the horse and was monitored twice weekly from 30 min before to 30 min after training, i.e. including the training period. In addition, cortisol concentrations were determined in faecal samples collected three times daily. Overall basal HR before daily training was 39±2 (SEM) beats/min and mean values did not change significantly over the 10-week study period. Average HR during initial lunging (week 1) was 119±14 beats min and decreased to 95±5 beats/min in week 2. Due to individual variations this decrease did not reach statistical significance. Neither first mounting of a rider (89±10 beats/min) nor an increasing workload (e.g. week 8: 111±4 beats/min) were associated with prolonged increases in mean HR, but transient increases were recorded and the response to mounting of the rider differed markedly between stallions. After daily training, HR decreased rapidly but was slightly, although significantly (p<0.05, Friedman-test) higher than pre-work values (46±2 beats/min). Cortisol metabolite concentrations in faeces tended to decrease during the period of lunging, were not increased when the horses were first mounted by a rider but rose slightly with an increasing work load during the last 4 weeks of the 10-week training period. In conclusion, based on HR and faecal cortisol metabolite concentrations, the initial training of sport horse stallions in the classical German training system is not associated with major stress for the horse. The increase in HR during training is due to physical exercise itself and not associated with specific situations of the training programme.
Supported by a fellowship from Stiftung Forschung für das Pferd to AS |
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Wehnert, C., Schmidt, A., Möstl, E., Aurich, J., Müller, J., & Aurich, C. (2008). Heart rate and cortisol release in horses during road transport. In IESM 2008.
Abstract: In sport horses, equestrian competitions may lead to increased cortisol release. The competition itself but also a new environment or transport to the events can be considered as stressors. In this study, warmblood sport horses (4-16 years, 4 mares, 2 stallions, 18 geldings) were transported by road for one (t1), 3.5 (t3.5) and 8 hours (t8), (n=8 per group). Heart rate (HR) is an indicator of stress and correlates with cortisol release. Heart rate was recorded with a mobile recording system (f810i, Polar, Kempele, Finland), fixed to a girth around the thorax of the horse and was monitored the day before transport, during transport and 12 hours thereafter. In addition, cortisol metabolite concentrations in faeces were determined in order to analyse adrenocortical activation during transport. Faecal samples were collected three times per day. Cortisol metabolite concentrations in faeces are increased approximately 24 hours after an elevation in plasma cortisol concentrations. Basal HR before transport did not differ between groups (45±2 (SEM) beats/min). During the first 30 min of transport, HR increased significantly (84±6, p<0.001, Kruskal-Wallis-H-test) but did not differ between groups. During the remaining part of the transport, HR was 61±6 beats/min (p<0.001 vs. first 30 min). When HR was analysed for the last 30 min of transport, values for groups t1 and t8 were significantly (p<0.05) higher than in group t3.5. HR decreased to baseline values within less than 30 min after transport and did not differ between groups (30-60 min after transport: 44±3 beats/min). Faecal cortisol metabolite concentrations on the day after transport were elevated compared to pre-transport baseline values in all three groups of horses. Significant differences existed between groups (e.g. 18 hours after transport t1: 91±5, t3.5: 110±18, t8: 136±27 ng/g; p<0.05). Based on HR analysis, horses of group t3.5 had adapted to transport, while the prolonged transport in group t8 again was a stressor. In group t1, which was transported only for one hour, the higher heart during the last 3 min of transport was still part of the initial rise in HR. After an initial increase, heart decreases indicating adaptation of the horse to transport. Cortisol metabolite concentrations in faeces indicate that transport causes adrenocortical activation with the amount of cortisol released depending on the duration of transport. Transport over medium distances appears to no major stressor and a negative impact on the performance of the horse is unlikely. Transport over 8 hours caused the most pronounced cortisol release and HR increases again during the last hours of an 8-hour transport. Transports exceeding this time may temporarily affect the subsequent performance of the horse in equestrian sports.
Supported by Stiftung Forschung für das Pferd |