Horses' behavior and heart rate in a preference test for shorter and longer riding bouts

Journal of Veterinary Behavior (2012) 7, 362-374

RESEARCH

Horses’ behavior and heart rate in a preference test for shorter and longer riding bouts Uta Ko¨nig von Borstela, Julia Keila,b a b

Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada; and University of Veterinary Medicine Vienna, Wien, Austria. KEYWORDS: horse; riding; preference test; workload; heart rate; behavior

Abstract A Y-maze preference test was used to investigate whether horses prefer a shorter riding treatment over a longer riding treatment. In a pilot study (n 5 4 horses), the maze was positioned with the 2 arms each pointing toward one of the short sides of the indoor arena, and in the main study (n 5 14), the maze was rotated by 90 . Horses were 11 6 4.4 years old and ridden regularly for at least 5 times/ wk. They were conditioned to associate 1 exit of the maze with 1 lap of riding (R1), covering a distance of approximately 40 m at the walk or trot according to a predetermined schedule, and the other exit with 2 such laps (R2). Immediately afterward, riders dismounted, horses were led into the maze, and horses were let loose to make their choice in the maze. After exiting the maze, the rider mounted again and rode according to the chosen treatment. This procedure was repeated on the same day until statistical significance (P , 0.05) of preference was reached or up to a maximum of 35 trials. In addition, behavioral observations and heart rates were recorded. In the pilot study, all horses, regardless of the associated treatment, chose the left arm, which, unfortunately, pointed toward the arena’s exit door. If horses were not caught immediately after exiting the maze (n 5 5 occasions), they walked or trotted straight to the door. In the main study, 4 horses significantly preferred R1, 2 horses significantly preferred R2, and 8 horses had no significant preference. Heart rates were significantly (P , 0.05) higher during R2 (87.4 6 2.6 bpm) than during R1 (79.5 6 2.4 bpm). Except for tail swishing, no significant differences were found for the frequency of occurrence of behavior patterns between R1 and R2. Over the course of repeated trials, some horses became increasingly reluctant to enter and walk through the maze, and most showed increasing resistance to being remounted (e.g., sidestepping). Overall, the experimental setup did not seem to be appropriate to answer the research question. It is likely that the repeated mounting and dismounting caused discomfort or confused many of the horses to an extent that they did not actively select a treatment but rather searched for ways to evade further mounting (and riding). In conclusion, horses did not show a clear preference for either shorter or longer riding bouts, but their behavioral reactions indicate that they perceived mounting as uncomfortable and that their motivation to rejoin their herd-mates and/or to obtain feed in the barn was greater than their motivation to being ridden at all. Nevertheless, pronounced individual differences also seem to exist, with some horses showing little aversion to, and perhaps enjoyment of, being ridden, whereas others clearly preferring not to be ridden. Ó 2012 Elsevier Inc. All rights reserved.

Address for reprints requests and correspondence: Uta Ko¨nig von Borstel, BSc, MSc, PhD, Department of Animal Science, University of Go¨ttingen, Albrecht-Thaer-Weg 3, 37075 Go¨ttingen, Germany; Tel: 149-(0)551-39-101-39; Fax: 149-(0)551-39-5587. E-mail: [email protected] 1558-7878/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.jveb.2012.02.006

Ko¨nig von Borstel and Keil

Horses’ preference for different riding workloads

Introduction Many riders believe that their horses enjoy being ridden. Also, the Fe´de´ration Equestre Internationale (FEI, 2006) calls the objective of dressage in their international rulebook ‘‘the development of the horses into a happy athlete through harmonious education.’’ However, scientifically, there are serious difficulties in complying with this request, as it is not known under which conditions, if any, horses get pleasure from riding. On the one hand, it is suggested that horses have a behavioral (i.e., psychological) need for locomotion itself. For example, the development of repetitive locomotor stereotypies is thought to be potentially linked–among other factorsdto deprivation of exercise (Bachmann et al., 2003; McGreevy et al., 1995; Mills et al., 2005), which may lead to frustration from the behavioral motivation for exercise (Mills et al., 2005). Access to exercise opportunities can also reduce the occurrence of stereotypic behavior, as shown in horses in a study by Krzak et al. (1991) or in hamsters in a study by Gebhardt-Henrich et al. (2005). Thus, there may be a motivation for locomotory activity itself that does not have an immediate function or use to the animal (Fraser, 1992), such as in the case of play behavior (McDonnell and Poulin, 2002). Besides, there is a necessity for locomotion to maintain physical well-being (e.g., by walking while grazing or by fleeing from predators). Depending on the nature of their environment and availability of forage, freeranging horses spend between 55% and 75% of their day in locomotion, which consists mainly of moving at a slow walk to graze (Duncan, 1980; Keiper, 1980; Salter and Hudson, 1982; Boyd and Bandi, 2002). Thus, a strong behavioral need for walking is likely to exist, and in horses that were observed after being exercised on a high-speed treadmill, walking (besides eating, elimination, and selfgrooming) was not significantly influenced by exercise (Caanitz et al., 1991). Also, Houpt et al. (2001) pointed out that mares housed in tie stalls showed a compensatory increase of locomotion in turnout areas after being deprived of free exercise. The same compensatory effect was observed by Kurvers et al. (2006) and by Chaya et al. (2006) in foals, despite the fact that their horses were ridden on at least 5 d/wk. Therefore, exercise seems to be important to horses, and the possibility to express locomotory behavior after deprivation of exercise might result to some degree in the experience of pleasure in horses. On the other hand, riders also frequently complain that their horses are ‘‘lazy,’’ that is, that they are disinclined to activity. Indeed, it seems likely that horses have mainly evolved to save energy. Horses are considered very costefficient movers (Minetti et al., 1999). For example, gait transitions in horses are suggested to occur at a speed that maximizes metabolic economy, presumably triggered by a system of biomechanical and metabolic factors (Wickler et al., 2003; Griffin et al., 2004). In each gait, horses move at a preferred speed that correlates with the

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minimum cost of transport (i.e., energy spent per unit body mass and distance moved) for that gait (Hoyt and Taylor, 1981; Wickler et al., 2001; Griffin et al., 2004), with walking being the overall cheapest gait in horses (Reilly et al., 2007). Also, even though Walker and Liem (1994) rightfully consider unguligrade to be an adaptation for speed, Reilly et al. (2007) suggest that it seems to have evolved in horses to make walking more costefficient rather than making running gaits cheaper, as unguligrade limbs serve as supreme pendulums. Behavioral studies on domestic horses housed in confinement showed that opportunities for exercise strongly influenced general activity. Jørgensen and Bøe (2007) found that daily forced exercise in a walker significantly reduced activity of stallhoused horses in turnout paddocks. Also, both the aforementioned studies that observed a compensatory effect (Houpt et al., 2001; Chaya et al., 2006) also found that horses that had daily access to free exercise significantly decreased their activity in the paddocks. Thus, it seems that after compensating for the deprivation of exercise, horses show relatively little motivation to spend more energy than necessary. Also, in recent studies with similar setup, compared with the present study, most horses seemed to prefer treatments involving lower workload rather than higher workload, both under a rider (Go´reckaBruzda et al., 2011) or on a treadmill (Lee et al., 2011). Therefore, from an evolutionary and ecological standpoint, it can potentially be concluded that although horses likely have a pronounced requirement for exercise, they have mainly evolved to save energy. These considerations lead to the questions of how much and what quality of locomotion fulfils the physical and psychological needs for exercise in riding horses (which are typically kept in a confined environment and provided with food), what role riding can play to satisfy locomotory requirements, and how that affects animal welfare. Therefore, the aim of the present study was to use a preference test to investigate whether horses prefer shorter over longer riding bouts. We hypothesized that horses would choose a lower workload if given the chance. We further hypothesized that horses with less energetic temperament, as assessed by their owners, will show a more pronounced preference for lower workload.

Materials and methods All procedures are in accordance with the Canadian Council on Animal Care guidelines to the care and use of experimental animals, and they were approved by the University of Guelph Animal Care Committee as well as the University of Guelph Research Ethics Board.

Horses and riders Eighteen mature riding horses of various Warmbloodtype breeds between the ages of 4 and 20 years were

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Table 1 Overview of horses’ age, gender (G, gelding; M, mare), riding discipline (W, Western; E, English), and owner type (P, privately owned; S, school horse) Horse

Age

Gender

Discipline

Owner

A B C D E F G H I J K L M N O P Q R

15 12 8 12 8 20 19 4 10 8 10 16 12 7 6 12 13 8

G G M G M G G G G G M G G G M G M G

E E E W W E E W/E W/E E E W E E W W E E

S P S P S S S S S S P S S P P P P S

involved in this study (Table 1). Of these, 4 horses participated in a pilot study and 14 horses in the main study. Horses were trained in English (n 5 11), Western (n 5 5), or both riding styles (n 5 2). They were either privately owned (n 5 7) or used as school horses in a college riding program (n 5 11). All the horses were housed in the same location in individual box stalls and were usually ridden on 5 d/wk for 1-3 hours, individually or in group lessons. They were turned out, weather permitting, every day for approximately 5 hours in sand paddocks ranging in size from 0.1 to 0.35 ha. The horses were fed hay 3-4 times a day (6 AM, 12 PM, 4:30 PM, 8 PM) and received individual rations of concentrate feed twice daily (6 AM, 4:30 PM). Sixteen volunteer riders were recruited from the University of Guelph equinerelated college or university programs. Two riders participated twice. They were all female, between 18 and 28 years of age, and rode at various amateur levels, with the majority of participants (n 5 14) riding at a prenovice or novice level. Riders either owned the horses they rode in the experiment or were otherwise familiar with them from lessons and coaching sessions.

Location and experimental setup The experiment was carried out inside a 15 ! 35-m2 indoor riding arena where a Y-maze apparatus had been set up. All horses were familiar with the location but none of them was exercised there on a regular basis. The Y-maze was the same as described in another study (von Borstel et al., 2009) with 1 black and 1 cream-colored maze arm

Arena door observer

observer (for right side treatments)

Arena door observer (for left side treatments)

Figure 1 (A) Setup of the Y-maze for the 4 horses of the pilot study (not to scale). Dotted lines indicate the path taken by horses without rider (moving freely and led), and dashed lines indicate the ridden path. (B) Setup of the Y-maze for the 14 horses of the main study (not to scale). The observer alternated the position depending on the treatment. Dotted lines indicate the path taken by horses without rider (moving freely and led), and dashed lines indicate the ridden path.

that could be exchanged between left and right side of the maze. Pilot study and main study For the pilot session, the Y-maze was set up in the middle of the arena with the trunk toward the long side, leaving room for two 15-m circles on each side (Figure 1A). In the main study, the setup was changed, as it was suspected that the position of the arena door considerably influenced the horses’ choices in the preference test. Thus, for the remaining 14 horses, the Y-maze was turned and set up with its trunk toward the short side and the door of the arena, leaving room for two 16 ! 6 m2 ovals that were separated by a line of jumping fences that were 1.30-m high (Figure 1B).

Testing procedures The preparation and conditioning procedures were the same for horses of the pilot study and of the main study, and data were thus combined for the conditioning phase, but analyzed separately for the preference test. Preparation and habituation On the day of testing, horses had not received exercise and were stall-rested for a minimum of 12 hours. After the

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Horses’ preference for different riding workloads

usual grooming and tacking, the horses were additionally fitted with a heart rate monitor (Polar RS800, Polar Electro Oy, Kempele, Finland), according to the manufacturer’s instructions. Horses were tested and habituated to the testing conditions individually. Habituation to the maze consisted of hand-walking horses through the maze at least 4 times, ensuring that they exited both arms equally often. Additionally, the horses were made familiar with the sounds of tail swishing and sand being kicked against the maze walls. This was conducted until they no longer showed obvious signs of distress or flight responses while in the Y-maze. In the next step, to prepare the horses for the preference test situation, they were trained to walk through the Y-maze on their own. For this procedure, 1 arm of the Y-maze was closed, leaving only 1 opening for the horse to exit. The rider was instructed to stand beside the open exit, with her back toward the entrance of the Y-maze. This position was chosen to have the setup resemble the later preference testing procedure, where the aim was to minimize the potential for the rider to influence the horse in its choice. The horse was positioned in front of the entrance and then encouraged by the observer first verbally and by gestures, and if necessary, subsequently also by tactile cues, to step into the Y-maze on its own. As the horse walked through the maze, the observer remained centered behind the horse just outside of the Y-maze entrance, driving the horse forward verbally if necessary. The horse was then caught by the rider on exiting the maze arm. This was conducted twice for each side. The riders were then asked to warm up the horses according to their individual needs for a maximum of 10 minutes. Following the warm-up, the horses were ridden through the Y-maze at the walk, exiting twice through each arm. Potentially, preexisting side biases were investigated by instructing the riders to ride the horses at the walk with loose reins straight toward the arena wall opposite to the door, not giving any cues except for encouraging the horse to move forward. This procedure was conducted twice per horse, and it was noted whether the horses turned right, left, or stopped when they reached the wall. Conditioning phase During the conditioning phase, the horses were trained to associate 1 exit of the Y-maze with a treatment involving a higher workload comprising riding 2 circles/ ovals (R2), and the other with a treatment involving a lower workload comprising riding only 1 circle/oval (R1). The circumference of 1 circle or oval was approximately 40 m. One riding treatment (R1 or R2) was considered 1 trial, and the conditioning procedure was repeated for a total of 32 trials, consisting of 2 sets with 16 trials each. For a given horse, all testing was concluded in 1 day. The horses were encouraged to pass through the Y-maze at a walk, and were ridden on exiting the maze arm in R1 or R2 treatments, respectively. To limit the stress on the horses’ backs caused by frequent mounting, the horses

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were ridden through the Y-maze for the first 28 trials. For the last 4 trials, the horses walked through the Y-maze without a rider as practiced during the habituation phase, and were remounted using a mounting block on exiting the maze arm. The side associated with higher workload remained the same for each horse throughout the session, and was balanced among all horses participating in the study. However, if horses haddaccording to their ownerda side preference, their preferred side was chosen to be associated with R2 treatments. Following the procedures described in the study by von Borstel et al. (2009), association of the treatments was balanced across horses for sides (left/right maze arm) as well as maze arm color, and direction of riding (clockwise/counterclockwise) and gaits (4 rounds walk and 12 rounds trot per treatment) were balanced across the 2 treatments. A semirandomized procedure was used to determine the order through which arm the horses were to exit, and to ensure randomness and equal distribution of left- and right-side treatments as well.

Preference test On the same day, immediately after the conditioning phase, a choice test was carried out to investigate whether horses showed preferences between R1 and R2 treatments by giving them the option to choose between the 2 exits of the Y-maze. The riders were instructed to dismount and to stand in the middle between the 2 exits, facing away from the Y-maze and the horse. The horses were then led by the observer to the entrance of the maze. To minimize the influence on the horses’ choices, the side from which the horses were led into the Y-maze was alternated throughout the testing phase. Furthermore, it was ensured that the horses entered the maze trunk straight and centered, and that the observer remained behind the horses, just outside of the maze entrance, as horses were walking through the Y-maze. On exiting, the horses were then remounted and ridden at the trot in the chosen treatment (R1 or R2). The direction of circle/oval was alternated for subsequent choices per each side. The horses’ choices were recorded on a chart (Figure 2AD) developed by Bross (1952) for sequential trials. Details for this method are described in the study by von Borstel et al. (2009). In brief, the method allows terminating the experiment as soon as significance (P , 0.05) of preference for one or the other side (maze arm) is reached. Therefore, the experiment could be terminated as soon as a significant result was achieved, allowing use of the horse to be kept to a minimum. In addition, for this study, a maximum of 35 trials per horse was determined to avoid overexertion of horses and/or riders. A graph based on the same principles is also available for a significance of P , 0.1 (Bross, 1952), and it was used to test significance of choices, in case the maximum of 35 choices had not resulted in a significant preference for one of the sides at P , 0.05.

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Figure 2 (A-D) Examples of results of the preference test for horses Q, O, J, and G. (A) Path of horse Q significantly preferring R1 treatments without ever choosing the R2 treatment. (B) Path of horse O significantly preferring R2 treatments. (C) Path of horse J not showing a significant preference or tendency for either R1 or R2 treatments. (D) Path of horse G, for which the test was ended after 35 trials without reaching significance. Choices are recorded on the chart developed by Bross (1952) for sequential trials. Starting in the square marked with ‘‘x’’ a pathway is created, reflecting the consecutive choices made by the horse. If the horses chooses the left arm, the adjacent square to the top is marked; if the horse chooses the right arm, the adjacent square to the right is marked. Procedures are repeated until a bold line is crossed. Crossing the bold line on the outside of either graph arm represents a significant preference for the treatment on that side at P , 0.05. Crossing the bold line on the inside represents indifference between treatments. (R1 5 treatment involving a low workload consisting of 1 round of riding; R2 5 treatment involving a doubled workload consisting of 2 rounds of riding).

Data collection Questionnaire In addition to collecting general information about the horses, such as age, breed, and riding discipline, a questionnaire obtaining information on certain characteristics of the horse was completed before the experiment, either by the horse’s owner (privately owned horses) or by the barn manager (school horses). They were asked to rate how easily the horse can be aroused to activity and its responsiveness to the rider on scales from 1 to 5 (with 1 5 very lazy [preferably stands or moves at slow speeds and seeks every possibility to slow down] to 5 5 very energetic [always active and needs to be held back by the rider] and 1 5 very high to 5 5 very low for responsiveness), as well as to indicate whether the horse had a certain side preference when ridden. Furthermore, it was noted if

and how the horse had been exercised on the testing day before the experiment, as this, unfortunately, could not be standardized for all horses due to organizational reasons. A summary of all recorded variables and their use in the analysis is given in Table 2. Heart rate During the conditioning phase, horses’ heart rates were recorded to obtain an indication of the differences in physical effort combined with the potential psychological effects of the 2 treatments. Additionally, start and end time of each individual trial (5 R1 or R2 treatment) was recorded, and mean heart rates per trial were calculated. Owing to the fact that there is no consensus in the literature on how to edit heart rate recordings using devices that do not store electrocardiogram data (see von Borell et al., 2007), heart rate values in each trial outside the

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Table 2 List of all variables recorded before the experiment (horse-related information), during the conditioning phase, or during the preference test and their mode of use, that is, their consideration and use as independent or dependent variable in the final analysis

Variables and their levels Horse-related information Horse (18 individuals) Breed (e.g., Thoroughbred) Owner type (private/school) Age (4-20 years) Gender (mare/gelding) Coat color (e.g., bay) Riding discipline (english/western) Type of bit (snaffle/curb) Normal side preference (left/right) Side preference test (left/right) Responsiveness to rider (score, 1-5) Inclination to activity (score, 1-5) Exercise on day before test (riding/stall-rested/turnout) Conditioning phase Heart rate (mean bpm) Behavior patterns (frequencies) a. Frequent occurrence b. Rare occurrence Treatment (R1/R2) Gait (walk/trot) Maze arm color (black/cream) Treatment-side (left/right) Duration of trials (seconds) Trial number (1-32) Intensity of rein contact (1-5) External disturbances (frequencies) Preference test Choice of treatment (R1/R2/none) Side of leading (left/right) Hesitation to enter or leave maze (frequency of stops) Running out of maze (frequency of trotting or cantering) Evasion of mounting (sidestepping, moving with head held high) Averseness to rein pressure Evasion toward door (frequency)

Analyzed as independent variable?

Considered (regular print) and used in the final analysis (bold print) as dependent variable in the analysis of.

No No No No No No No No No No No No No

Heart rate, behavior (a) as random factor /(too many levels) Heart rate, behavior (a) Heart rate, behavior (a) Heart rate, behavior (a) /(too many levels) Heart rate, behavior (a) Heart rate, behavior (a) Preference Preference Heart rate, behavior (a), preference Heart rate, behavior (a), preference Heart rate, behavior (a), preference

Yes

/

Yes Noa No No No No Yes No No Yes

Duration of trial, external disturbances Duration of trial, external disturbances Heart rate, behavior (a) Heart rate, behavior (a) Heart rate, behavior (a), preference Heart rate, behavior (a), preference Heart rate, behavior (a) Heart rate, behavior (a) Heart rate, behavior (a), preference Heart rate, behavior (a), preference

Yes No Noa Noa Noa Noa Noa

/ Preference Preference Preference Preference Preference Preference

Behavior patterns with frequent occurrence (a) include the patterns ‘‘pinned ears,’’ ‘‘averse reaction to bit,’’ ‘‘tail swishing,’’ ‘‘evasion toward door,’’ ‘‘rider’s use of legs,’’ and ‘‘rider’s use of voice.’’ Behavior patterns with rare occurrence (b) include ‘‘escaping,’’ ‘‘whinnying,’’ ‘‘rider’s use of whip,’’ ‘‘rider’s use of hand.’’ a Simple means were calculated due to rare or zero occurrence at some levels.

physiological range of 35-200 bpm at the walk, and 45-240 bpm at the trot were considered erroneous and were excluded from the analysis. This error-correction procedure resulted in 0.43% 6 0.89% of individual values per trial being considered erroneous; therefore these individual values were excluded from analysis. Trials that involved deletion of .20% erroneous values were excluded altogether from the analysis (n 5 2).

Behavioral observations During the conditioning phase, behavioral observations were taken by an observer positioned at the wall facing the

Y-maze entrance (for the pilot study) or at the wall on the side opposite to the ongoing treatment side (for the main study). Frequency of occurrence of several behavior patterns in the horse and rider was recorded (Table 3). Additionally, external disturbances, such as noise from a tractor passing by, were noted. The overall intensity of rein contact applied by the rider throughout the experiment was rated by the observer on a scale from 1 to 5 (with 1 5 loose to 5 5 very strong). Along with horses’ choices (R1 or R2), the side from which the horse was led into the Y-maze entrance was noted for each individual trial. Additionally, occurrences of any strong behavioral reactions were noted (Table 2).

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Table 3

Description of behavior categories recorded in horses and riders during the conditioning phase

Behavior category

Description

Tail swishing Averse reaction to bit (5 behavior associated with averseness to bit pressure)

Quick lateral or vertical movement of the tail (McGreevy et al., 2005). Nose tilting: The horse carries its head with the nose tilted to one side (McGreevy et al., 2005). Tongue out: The horse’s tongue is hanging out of the mouth for .3 seconds. Teeth grinding. Mouth open: The horse’s mouth is kept open for .3 seconds. Excessive play with bit: Chewing, licking, or tongue play that is displayed for .5 seconds. Quick forward-upward motion of the horse’s head (Minero et al., 2003), restricted by the reins. The ears are either flattened against the horse’s head or kept turned backwards for .5 seconds. Shying: Sudden reaction that involves swerving of the fore-quarters (McGreevy and McLean, 2005). Scooting: An instant flight response that involves trotting or cantering away for a short distance. The horse drifts toward the door of the arena.The horse speeds up toward the door of the arena. Characteristic vocal utterance of horses that can indicate separation anxiety

Head tossing Pinned ears Escaping behavior

Evasion behavior toward door Whinny Rider behavior (Rider uses.) Voice Leg Hand Whip

Use of voice commands to encourage the horse to move forward. Forceful application of leg and/or heel pressure initiated by an outward motion of one or both lower legs (‘‘Kick’’) Pulling on the reins by moving one or both hands backward with some force. Use of a whip on the horse’s trunk to encourage forward motion.

Each coherent unit of a behavior pattern was counted as one occurrence regardless of its lengths (e.g., in the case of rider’s use of voice, a phrase such as ‘‘come on boy!’’ would have been counted as one occurrence of that behavior pattern).

Statistical analysis

on the coefficient of determination in the regression analysis. Thus, the final model was as follows:

All analyses were conducted in SAS 9.1 (http:// www.sas.com; SAS Institute Inc., Cary, NC). Mean heart rates per conditioning round were tested for normality (PROC UNIVARIATE), and after removal of a few (n 5 20) outlying values, residuals followed a normal distribution. Heart rates were analyzed using a mixed model with repeated measures over conditioning trials 1-32 (PROC MIXED). Continuous variables (see Table 2) in the final model were determined using a model selection procedure (PROC REG RSQUARE) based on a compromise between achieving low numbers of variables and a high coefficient of determination. Treatment and other categorical variables such as maze arm color were tested for significance and only included if they were significant at P , 0.05. In the final model, age, duration of treatment, and the responsiveness to the rider were considered linear covariates, gait and treatment (R1 or R2) were considered fixed factors, and horse was considered a random factor. The linear variables age and responsiveness were not significant (P . 0.1), but nevertheless included in the model, as they had a considerable effect

yijklmn 5gi 1tj 1ak 1dl 1r2m 1hn 1eijklmn with yijklmn representing the heart rate per trial; gi, the gait (walk/trot); tj, the treatment (R1/R2); ak, the horses’ age; dl, the duration of the trial in seconds; rm, the responsiveness to the rider as assessed before testing by the questionnaire; hn, the random animal effect; and eijklmn, the random error term. Behavior variables were analyzed in a similar manner as heart rates, but by using a generalized linear mixed model (PROC GLIMMIX), assuming an underlying Poisson error structure (using a log link function) for averseness to bit, and a binomial error structure (using a logit link function) for tail swishing, pinned ears, evasion toward door, leg use, and voice. Duration of the treatment and the observation category ‘‘disturbances’’ were also analyzed with this method. The latter was analyzed to check for potential bias in the observer (i.e., whether disturbances were less likely to be noticed during instances when other horse behavior had to be recorded), which, however, was not the case. Because of the rare occurrences of escaping

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Table 4 Frequencies (LS-means for original scale data [for information purposes] and for latent-scale data [i.e., analyzed values]) of behavior patterns observed per trial during the conditioning phase by treatment (R1, low workload consisted of 1 round of riding; R2, double workload consisted of 2 rounds of riding) after correction for differences in duration and significance of difference between treatments (n.s. 5 P . 0.1)

Behavior category a

Pinned ears Averse reaction to bitb Tail swishinga Evasion toward doora Lega Voicea

LS-mean frequency per trial (original scale)

LS-mean estimate 6 standard error (underlying logita or logb link scale)

R1

R2

P value

R1

0.15 1.35 0.01 0.03 0.08 0.13

0.14 1.78 0.05 0.06 0.29 0.30

NS NS 0.0040 NS NS NS

24.14 20.83 26.67 24.72 23.24 23.32

R2 6 6 6 6 6 6

0.78 0.44 1.07 0.77 0.48 0.58

23.94 20.66 23.40 25.27 23.01 22.86

6 6 6 6 6 6

0.85 0.45 0.74 1.23 0.63 0.67

a

Analyzed using logit procedure. Analyzed using log procedure.

b

(n 5 2), whinnying (n 5 9), and hand (n 5 0) or whip use (n 5 2), a statistical analysis of these variables was not possible or appropriate. A factorial logistic regression was used to analyze whether factors such as the side from which the handler had led the horse into the Y-maze, the horse’s normal side preference, maze arm color, or results from the side preference test had significant influence on the horse’s choices.

all analyzed behavior variables (pinned ears, averse reactions to the bit, tail swishing, evasion toward door, leg and voice use) occurred significantly more often at the trot than at the walk (Table 5). Evasion toward the door was significantly more likely to occur with progressing conditioning trials (P 5 0.0336), and the treatment duration was significantly (P 5 0.0012) prolonged by 0.29 6 0.09 seconds for each occurrence of an aversive reaction to the bit.

Preference test

Results Conditioning phase During R2, average heart rates (bpm 6 standard error) were 87.4 6 2.6 bpm, which were significantly higher than during R1 (79.5 6 2.4); however, in general, heart rates decreased by 0.34 6 0.07 bpm per each additional second of treatment duration (both P , 0.0001). At the trot, the mean heart rate of all horses was 89.8 6 2.4 bpm compared with 77.2 6 2.6 bpm at the walk (P , 0.0001). After correcting for treatment duration, only tail swishing occurred significantly (P , 0.05) more often during R2 than during R1 (Table 4). However, except for pinned ears,

In the pilot study, 2 horses significantly preferred the maze arm associated with R1, and 2 horses significantly preferred the maze arm associated with R2. For all 4 horses, these choices implied a preference for the left maze arm that pointed to the arena’s exit door. In addition, in a few (n 5 5) instances, horses (n 5 3, i.e., 2 horses showing the behavior pattern twice) trotted out of the Y-maze arm such that riders were unable to catch them immediately at the exit of the maze. In these instances, horses further trotted toward the arena’s exit door, where they could be caught eventually by the rider or experimenter. In the main study, 4 horses significantly preferred the maze arm associated with R1 treatments (P , 0.05), whereas

Table 5 Frequencies (LS-means for original scale data [for information purposes] and for latent-scale data [i.e., analyzed values]) of behavior patterns observed per trial during the conditioning phase by gait (walk/trot) after correction for differences in duration and significance of difference between gaits (n.s. 5 P . 0.1)

Behavior category a

Pinned ears Averse reaction to bitb Tail swishinga Evasion toward doora Lega Voicea

LS-mean frequency per trail (original scale)

LS-mean estimate 6 standard error (underlying logita or logb link scale)

Walk

Trot

P value

Walk

0.11 0.68 0.02 0.01 0.16 0.14

0.16 2.44 0.04 0.08 0.21 0.29

N.S. ,0.0001 0.0081 0.0420 0.0700 0.0434

24.21 21.28 27.54 26.63 23.72 23.61

Trot 6 6 6 6 6 6

0.82 0.45 1.39 1.52 0.68 0.69

23.87 20.21 24.29 23.36 22.52 22.57

6 6 6 6 6 6

0.75 0.43 0.68 0.58 0.46 0.56

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2 horses preferred (P , 0.05) the maze arm associated with R2 treatments. Six horses did not make statistically significant choices for 1 specific treatment, of which 1 showed a tendency (P , 0.1) toward choosing R1 treatments. For an additional 2 horses, the preference testing was ended after completing the predetermined maximum of 35 trials, not having crossed any barrier of the graph (Figure 2D). The pathways reflecting the different types of choices in the preference test of 4 selected horses (Q, O, J, G) are shown in Figure 2A-D. Eight horses repeatedly hesitated or even refused to walk into and/or out of the Y-maze. This hesitation was shown up to 16 times per horse, and frequencies increased during the course of repeated trials (e.g., none of the horses hesitated to enter the maze in their first test, and it was also not evident during the ridden conditioning trials, but all 8 horses showed hesitation during their last test). In addition, for 13 horses, a handler on the ground was required to hold the horse during mounting to prevent the horse from evading the mounting process, for example, by sidestepping or by moving forward while the rider attempted to place her foot into the stirrup. This evading of mounting likewise increased over repeated trials, with no horse requiring to be held during the first mounting and all of the 13 horses being held by the handler during their last mounting. The factorial logistic regression revealed that horses were more likely (OR [odds ratio] 5 1.26, P , 0.05) to exit the Y-maze to the right side when they were led by the handler on the left to the Y-maze entrance, and horses that their owners believed had no side preference were even more likely (OR 5 2.23, P , 0.05) to exit the Y-maze through the right rather than the left side. Horses that turned left in the first side bias test were more likely (OR 5 2.16, P , 0.05) to exit the Y-maze to the right rather than left during the preference test, whereas horses that turned left in the second side bias test were much less likely (OR 5 0.44, P , 0.05) to turn right rather than left during the preference test. Horses that were considered as fairly lazy by their owners did not differ significantly (P . 0.05) in their preferences from horses rated as more energetic.

Discussion The results of the preference test do not clearly support the hypothesis that horses choose a shorter riding treatment when given the chance. For more than half of the horses (n 5 8) of the main study, no significant preference for either a lower or higher workload could be detected, and only 4 of the remaining 6 horses chose the lower workload significantly more often than the higher workload. However, behavioral observations during choice-making, mounting, and riding suggest that horses perceive riding, and, in particular, the repeated mounting, as uncomfortable. Furthermore, results of the pilot study suggest that horses prefer exiting the riding arena rather than being ridden at all. It is likely that this motivation to exit the arena is caused by both the motivation

to rejoin their herd-mates as well the motivation to feed in the barn. Potentially, horses also prefer the open space to the enclosed area of the indoor arena with which horses were familiar only to a limited extent.

Conditioning phase Higher heart rates during R2 compared with R1 treatments are presumably mainly a physiological effect caused by the increase in exercise, but may potentially also be related to some form of psychological stress response. Significantly, more occurrences of tail swishing were found during R2 treatments, and these behavior patterns were associated with the nonpreferred riding treatment in our study investigating horses’ preferences for different head– neck positions (von Borstel et al., 2009). Because duration of treatment was simultaneously corrected for in the model, differences should mainly be because of the treatment per se rather than the duration of the treatment. Nevertheless, based on all analyzed behavior patterns, the difference between gaits seems to be more relevant than the differences between treatments (i.e., length of riding bout). More frequent occurrences of most analyzed behavior variables (averse bit, tail swishing, evasion toward door, leg use, voice use) at the trot than at the walk, regardless of treatment, suggest that being ridden at the trot represented greater discomfort to the horses than being ridden at the walk. However, these results are likely also influenced by the setup (Figure 1B), which involved narrow turns. Apparently, these narrow turns could not be easily managed by all horses at the trot. In addition, trotting presumably leads to a more unsteady seat ( Matsuura et al., 2008), and an unsteady seat is more pronounced in less-experienced riders (Lagarde et al., 2005), which applies to the majority of the participating riders. Therefore, it is likely that at a trot, there was more interference of the rider with the horses’ movements, which could have caused an increase in aversive behaviors. The lack of an effect of the observed intensity of rein contact on horses’ behavior patterns was surprising, but may be explained by the fact that evaluation of rein contact by visual inspection generally appears to correlate little with actual measurements of rein tension ¨ dberg, 2005). (de Cartier d’Yves and O

Preference test In a preference test, the animal is given some control over its environment. Observing the choices being made can be useful when assessing preferences as well as aversions toward certain resources. However, preference tests per se do not answer the question of how relevant the choice is to the animal: even consistent choices do not clearly indicate whether the animal is choosing resource A to avoid an unpleasant resource B, whether it does in fact perceive resource A as a positive event, or whether neither resource is

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important to the animal. As a consequence, preference tests can only be a first step in investigating how an animal feels about its environment, as it is necessary to quantify the strength of the choices made (Duncan, 2006). Yet, together with collecting other behavioral and physiological data, a preference test can be a helpful tool in assessing animal welfare (Kirkden and Pajor, 2006). All 4 horses in the pilot study significantly chose the maze arm that opened in the direction of the door, regardless of the treatment (2 horses chose R1, and 2 horses chose R2). These findings suggest, together with the behavioral observations of resistance to remounting, speeding up, or drifting toward the door throughout the conditioning phase and preference test, that horses perceived the procedures themselves (riding and/or mounting) as aversive; therefore, their choice indicated what they perceived as the lesser evil rather than a true preference. This assumption is further supported by the behavior of the horses that evaded being caught directly after exiting the maze and instead trotted to arena’s exit door. It is likely that these horses expressed their preference to return to the barn rather than being ridden at all, which is supported by the findings by Lee et al. (2011) showing that in a specifically designed preference test, most horses preferred to return to their stalls rather than to exercise on a treadmill. Similarly, Go´recka-Bruzda et al. (2011) showed that leisure horses preferred not to jump, if given the choice between riding bouts including or not including the jumping of an obstacle, indicating that horses generally avoid unnecessary physical effort. Nevertheless, the considerable individual differences found in the present study as well as in both aforementioned studies (Go´recka-Bruzda et al., 2011; Lee et al., 2011) suggest that although for the majority of horses higher workload in form of riding may be undesirable, there may be some horses that ‘‘enjoy’’ or do not mind exercise or being ridden, leading them to choose higher workload. Another reason for the ambiguous results of the present experiment may be found in equine learning behavior. From an evolutionary standpoint, it can be assumed that horses are comparatively quick learners (Nicol, 2005). Also, many riders experience how fast horses are able to anticipate certain events, particularly if the horses considered them as aversive. Furthermore, horses are considered to be good learners in tasks that involve spatial skills (see Nicol, 2002). Thus, in addition to the fact that the same conditioning regimen was used successfully in another study (von Borstel et al., 2009), it can be assumed that the given time frame was sufficient for horses to learn the association of maze arms with treatments. Potentially, many horses perceived both treatments as equally aversive or preferable, as no real reward or punishment was involved, unlike most experimental work on equine learning, where mainly primary positive reinforcement is used (Nicol, 2002). Additionally, the treatments involved less strenuous exercise than the usual riding routines. Wickler et al. (2001) showed that when horses were trotting with a load (w19% of body weight), the cost of transport

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increased while the preferred speed decreased to coincide with the new minimum cost of transport for trotting. In the present study, riders did not seem to interfere with the speed that the horses chose during the riding treatments (i.e., little use of visible leg aids or the whip was observed). Therefore, horses were possibly trotting at or very close to their preferred speed, and therefore close to the minimum cost of transport. If this was the case, neither treatment may have been very strenuous for the horses, thus lowering motivation to choose between higher or lower workload. Using a larger difference between treatments (e.g., 1 round vs. 10 rounds) might have led to different test outcomes. Another explanation for ambiguous results may be that riding horses might have learned not to make independent decisions while in contact with humansdespecially when tacked and/or being ridden, as such a behavior based on horses’ independent decision is often punished by the handler; some authors have described learned helplessness during riding (see Hall et al., 2008; McLean, 2008). Even if this was not the case for the horses in the present study, they presumably experienced stress to some degree during the experiment, and stress potentially affects cognitive function and therefore learning abilities (Mendl, 1999). It is of interest that when the horses were led by the handler on their left side into the Y-maze entrance, they were significantly more likely to exit the Y-maze through the right maze arm despite the fact that the handler tried to remain in a position as neutral as possible after releasing the horse. Possibly, this behavior also indicates that horses tried to avoid human contact that was linked to work. However, unintended influence by the handler’s position might not have been eliminated completely. As horses are in principle led on the left side and turns are executed away from the handler (see FN, 2005), the fact that horses tended to choose the right maze arm away from the handler could be attributed to a learned effect. According to McGreevy and Rogers (2005), it is worth considering that the convention to handle horses from their left-hand side has a possible effect on the side bias shown by horses when not being handled. The findings also revealed that the results of the side bias test neither corresponded with the owner’s assessment with regard to an existing side preference nor with the choices made by the horse in the preference test.

Considerations regarding the experimental setup Presumably, the most relevant aspect of the experimental design is the position of the arena door, as it very likely influenced the horses’ choices in the pilot study. For the horses that expressed their preference to leave the testing arena, it would be interesting to further investigate the relative motivation to return to herd-mates, to feed, and perhaps also additional factors such as to move to more open rather than enclosed space. For logistic reasons, the experiment could not be moved to a different location.

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Consequently, the experimental setting was changed to the setup of the main study in an attempt to eliminate the door as an influencing factor. However, this setup resulted in close spatial proximity of the 2 different treatments and might have been less ideal to enable the horses to make a clear differentiation between left- and right-side treatments, despite the visual barrier of jumping fences. Furthermore, this setup resulted in rather narrow turns, which may have been difficult to execute repeatedly for the horses. An overall better design of the present experiment could involve extending the conditioning phase to 1 conditioning session per day on multiple days during the course of several weeks, followed by 1 preference test in the end. For example, in studies on negative reinforcement by McCall et al. (1993), neither length nor number of trials per session was critical for the learning process, but frequency of sessions was. Finally, a greater difference between treatments could be implemented, for example, comparing one with several circles or walk with trot/canter treatments, or comparing riding with no riding, controlled for mounting. However, such an experimental design entails confounding of different motivational factors and thus greater difficulties to interpret the results. For example, differences in the amount or intensity of negative reinforcement will be present when comparing riding with standing still or some other form of movement without rider. Thus, it would be difficult to conclude whether differences in physical exercise or differences in reinforcement motivated the horses to make their choice. Ideally, a series of experiments should be conducted to compare the relative importance of different types and intensities of exercise as well nonexerciserelated motivational factors. Importantly, riders and horses of different skill levels should also be tested, as horse–rider pair skill level significantly affects behavior and stress experienced by the horses during riding (e.g., Ko¨nig von Borstel et al., 2011a,b). Most likely, rider’s actions (whether they are the result of deliberate cues or of an unbalanced seat and limited body control as is the case in lessskilled riders) strongly affect whether horses ‘‘enjoy’’ being ridden, which could be considered as a prerequisite to developing them into a ‘‘happy athlete.’’ In the present study, the majority of riders had lower skill levels, and potentially horses’ choices may have been different if only highly skilled riders would have ridden the horses. In future research, additional objective measurements should be recorded as well. For example, latency to pass through a maze has been used successfully to measure anticipatory behavior in rats (Capaldi et al., 1983) and could have provided additional information for the present study regarding the question whether horses preferred or avoided certain treatments. Also, the test for assessment of existing side-biases appeared to be not very predictive of horses’ behavior in the preference test. More established methods for assessment of lateralization should be used, such as described by Murphy and Arkins (2008) or van Heel et al. (2006).

Finally, the repeated mounting and dismounting appeared to interfere with horses’ learning or perception of the task. It was decided to use these procedures to eliminate the possibility of the rider influencing horses’ choices, as many speculate that this might have been the case with a few riders in our study regarding hyperflexion (von Borstel et al., 2009). In that study (von Borstel et al., 2009), the rider remained passively on the horse during horses’ decision making. However, findings from our present study suggest that dismounting and subsequent remounting is not a feasible alternative when conditioning and testing is to be conducted within 1 day. Even though the use of a mounting block reduces peak forces during mounting (Geutjens et al., 2008), there is still very high pressure at the withers during mounting (Geutjens et al., 2008). Repeated occurrence of this peak pressure probably resulted in discomfort or pain for the horses. This discomfort not only likely resulted in the frequent attempts to evade further mounting, but may have also overshadowed the subsequent treatments. Testing the horses additionally with the rider remaining mounted would help to verify, if indeed, that the repeated mounting was the major issue with the present experiment. However, it seems likely because besides the physical discomfort, the repeated remounting may have confused the horses. Dismounting is generally associated with the end of a riding bout and it is rarely immediately followed by another riding bout. This confusion may have existed to an extent that horses did not actively select a treatment but rather that they searched for ways to evade further mounting (and riding).

Conclusions Overall, the experimental setup did not seem to be appropriate to answer the research question. It is likely that the repeated mounting and dismounting caused discomfort or confused most of the horses to an extent that they did not actively select a treatment but rather they searched for ways to evade further mounting (and riding). Thus, on the whole, horses did not show a clear preference for either shorter or longer riding bouts, but their behavioral reactions indicate that they perceived mounting as discomfortable, that they perceived more discomfort during riding at a trot compared with a walk, and that they preferred to return to the barn rather than being ridden at all. Nevertheless, pronounced individual differences also seem to exist, with some horses showing little aversion to, and perhaps enjoyment of, being ridden, whereas others clearly preferred not to be ridden.

Acknowledgments The authors thank all staff members, riders, and horse owners at the University of Guelph Kemptville Campus for their help and cooperation. The scholarship awarded by the University of Veterinary Sciences in Vienna, Austria, to

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Horses’ preference for different riding workloads

J.K. for completion of the experiment is gratefully acknowledged. They also thank both reviewers for their very helpful comments to an earlier version of this article.

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