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The effects of blindfolding on behavior and heart rate in beef cattle during restraint
Applied Animal Behaviour Science 85 (2004) 233–245
The effects of blindfolding on behavior and heart rate in beef cattle during restraint Kelly D. Mitchell, Joseph M. Stookey∗ , Darrell K. Laturnas, Jon M. Watts, Derek B. Haley, Tara Huyde Department of Large Animal Clinical Sciences, University of Saskatchewan, Western College of Veterinary Medicine, Saskatoon, Sask., Canada S7N 5B4 Accepted 6 July 2003
Abstract Use of a blindfold or hood during handling and restraint has been suggested for many wild and captive animals. Two experiments were conducted to determine the effects of blindfolds on beef cattle during restraint. In Experiment 1, 60 beef heifers, na¨ıve to the restraint facility, were randomly assigned to either visual restriction (blindfold) or no visual restriction (control) and tested daily during a 4-day trial to determine the effects during restraint. Heart rate (HR) was measured via telemetry, during a baseline period prior to treatment and continuously recorded during a 1-min period of restraint, which included some manipulation of the animal. Manipulation was initiated 15 s into the restraint period. Two persons simultaneously approached the animal one on either side, grasped the ears, and touched the neck, sides and rump to simulate normal management tasks. Electronic strain gauges attached to the head gate quantified the animal’s struggle during this procedure. These were used to determine the average and maximum exertion forces upon the head gate during restraint. The association between treatment, sample time (day 0–4), animal weight and the various outcome measures were analyzed using a generalized estimating equation method. Mean HR of heifers did not differ at the end of the treatment (95.04 ± 4.66 bpm ) (P = 0.64), but the HR tended to decrease more for blindfolded heifers compared to controls during restraint (average decrease 16.3 ± 3.2 bpm and 14 ± 2.9 bpm, respectively) (P = 0.10). The average exertion forces applied by blindfolded heifers against the head gate were 23% lower (P < 0.05) during the 1-min period and maximum forces were 28% lower (P < 0.01). Heart rate and exertion forces declined over the 4 days for both treatment groups (P < 0.001). In Experiment 2, 93 commercial beef calves (average age 92.9 ± 2.0 days) were randomly assigned to either visual restriction (blindfold) (n = 46) or no visual restriction (control) (n = 47) treatments. Behavioral responses to treatment were quantified by measuring the amount of movement and recording the number of vocalizations while the calves were restrained for 1 min on a calf tilt table. Movement was recorded by an electronic device attached to a weighing platform that held the tilt table. After 30 s of restraint, one experimenter touched the animal’s ear while the ∗
Corresponding author. Tel.: +1-306-966-7154; fax: +1-306-966-7159. E-mail address: [email protected] (J.M. Stookey). 0168-1591/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2003.07.004
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other touched the neck, to simulate ear tagging and vaccination. Blindfolded calves moved 44% less than the control group (P < 0.01). However, the number of vocalizations that occurred during the 1-min test period did not differ (P > 0.05) between treatments. Overall, blindfolding cattle reduced the amount of struggle and tended to lower heart rate. Therefore, blindfolding may be advantageous during the routine invasive procedures commonly performed on cattle. © 2003 Elsevier B.V. All rights reserved. Keywords: Behavior; Blindfold; Cattle; Handling; Heart rate; Restraint; Vocalizations
1. Introduction Cattle are known to show physiological and behavioral changes in response to standard livestock handling and restraint techniques. In the absence of other painful stimuli, restraint alone can increase the heart rate and plasma cortisol concentrations of cattle to levels comparable to those recorded during transport and slaughter (Mitchell et al., 1988; Lay et al., 1992b). Ewbank (1961) observed that the majority of cattle restrained in a head gate became highly agitated and most struggled to withdraw their head or lunged forward when stimuli were applied to the neck. Attempts to escape and physical contact with the head gate can result in pain and injury, including bruising to the neck and back region (Grandin, 1998). Not only does increased carcass bruising represent an economic loss, it may also be an indicator of compromised animal welfare (Jarvis et al., 1996). Cattle have limited binocular vision, but roughly a 330◦ field of vision, which helps them to be keenly aware of visual stimuli in their environment. The most sensitive region in the retina is the horizontal foveal streak, which allows for a better means of detecting movement across a broader visual field (Heffner and Heffner, 1992). A subjective consideration of the animals’ visual perception has been a major factor in the design of handling facilities (Grandin, 1980). Cattle balk less and move calmly through handling systems with solid sides, which block the animal’s view of the handler (Grandin, 1998). Heifers restrained in a dark breeding box had lower plasma cortisol concentrations than heifers restrained in a conventional squeeze chute (Lay et al., 1992a). However, it is difficult to incorporate the dark box effect within a typical cattle head gate and race system used for restraint and handling. Blindfolding the animal once it is restrained in a head gate may be a practical method for taking advantage of the effects gained in the dark breeding box. Restriction of an animal’s visual field by means of a blindfold has been suggested for use during the handling and restraint of many wild and captive animals (Fowler, 1995). Covering of the head to block visual stimuli has been reported to keep raptors calm during restraint (Campbell, 1991; White, 1990). Struggling and wing flapping is greatly reduced in shackled and inverted broiler chickens, if a hood is pulled over the animal’s head prior to inversion (Jones and Satterlee, 1997; Jones et al., 1998a,b). Blindfolds are commonly used during the restraint and removal of antler from farmed elk (Thierman et al., 1999). Blindfolding of white-tailed deer is recommended to ease handling for routine procedures (Haigh and Friesen, 1995). Though it has been mentioned that blindfolds have a calming effect on restrained cattle (Grandin, 1990; Grandin, 2000; Ewbank, 2000), we are aware of only one controlled study
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that has provided data to support this claim (Andrade et al., 2001). The objective of the present study was to examine the potential calming effect of a blindfold on cattle during restraint.
2. Materials and methods 2.1. Experiment 1 Sixty yearling commercial beef heifers (mean weight 389.5 ± 3.33 kg) were divided into two groups for replication of the experiment. The heifers had been purchased from a local auction market and were of unknown origins. The main breed types represented were Hereford, Charolais, black Angus and their crosses. They were brought to the University of Saskatchewan Goodale Farm two weeks prior to being used in the experiment. All animals were housed outside and were na¨ıve to the facility where testing occurred. In each replicate 30 animals were randomly assigned to visual restriction (blindfold) (n = 15) or no visual restriction (control) (n = 15). A dark towel, held in place by a nylon halter, was used to restrict the vision of experimental animals. The blindfold was secured by fitting a standard nylon halter around the ears and muzzle of the animal and placing a dark towel under the straps of the halter so that it completely covered the eyes and the plane of the face, leaving ears, nose and mouth uncovered (Fig. 1). The blindfold was believed to block the heifers’ vision completely, as there was no response to movement in the normal field of view. Control animals were fitted with the standard nylon halter only, leaving the eyes and plane of the face uncovered. Fitting of the halter or blindfold took between 10 and 20 s.
Fig. 1. Photograph of an experimental animal with the blindfold treatment applied.
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Heart rate was measured as an indicator of the animal’s physiological response to the testing situation. The force exerted on the head gate during restraint was also measured and served as an objective measurement of the animal’s behavioral response. 2.1.1. Heart rate measurement Heart rate was recorded using remote telemetry (Paragon 420 Cardiac Monitoring System and TM8 Patient Transmitters: Quinton Instrument, Seattle, WA, USA) Heart rate was subsequently calculated from the ECG printout. The distance in mm (d) spanned by several interbeat intervals (n) was measured from the peak of the 0th to the nth QRS complex. Given that the paper moved at a constant speed of 1500 mm/min (s), heart rate was determined according to the following formula: HR = (n/d × s). Three days before testing, the heifers were moved through a separate chute and caught in a different head gate than the one used during the experiment. While restrained, two surgical staple (5.7 mm × 3.8 mm APOSE∗ ULC Disposable skin staples, American Cyanamnid, Wayne, NJ, USA) one on either side were inserted into the dermis of each heifer to serve as electrodes. The sites were shaved prior to the insertion of the staples. One staple was placed approximately 30 cm dorsal and 5 cm caudal to the right olecranon and the other approximately 5 cm both dorsal and caudal to the left olecranon. The electrode leads from the remote heart rate transmitter were fitted with alligator clips that were fastened to the surgical staples during the testing procedure. The heart rate transmitter was fixed to the top of the squeeze chute, near the head gate. Staples remained in the heifers for the duration of the experiment and were removed following testing on the fourth day. The animals appeared to suffer little or no pain or discomfort from the staples, given their lack of response upon application, during testing and at removal. 2.1.2. Strain gauge Several days prior to the experiment, the head gate was equipped with instruments, similar to those described by Schwartzkopf-Genswein et al. (1997), which could quantify the force exerted against the head gate. One pair of strain gauges was attached to the head gate at approximately the height of the animals’ neck, making it possible to measure the force exerted when an animal moved forward or backward in the chute. Output signals from the strain gauges were measured in volts (V). Signals from the strain gauges were amplified by a signal conditioner (Model 2310 Signal Amplifier, Vishay Measurement Group, Raleigh, NC) and stored as a single output file that included the animal identification, sample time and the digitized output. Average and maximum exertion force measurements were obtained from the digitized output of the strain gauge for each of three separate measurement periods. 2.1.3. Testing procedure Animals were tested daily on four consecutive days at roughly the same time each day. Each animal received the same treatment each day. Heifers were moved from their home pen and run single file through a curved race into the indoor testing facility. Only one animal at a time was inside the testing facility. The remaining animals were held either in the curved race or the connecting crowd pen.
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Once the animal was restrained in the head gate, the alligator clips of the electrode leads were attached to the surgical staples. Experimenters then positioned themselves one on either side of the animal approximately 1 m lateral to its head, where they remained silent and still. This position was maintained until a baseline heart rate had been established (pre-treatment). The control or blindfold treatment was then applied to the heifer for a period of 45 s. Strain gauge measurements were recorded for the entire 45-s period, and could be divided into three distinct periods of approximately 15 s each. The first 15 s (pre-contact) served to establish the baseline level of force exerted. After 15 s, the two experimenters simultaneously approached the animal from opposite sides and sequentially touched the ear, shoulder, flank and rump (contact) to simulate ear tagging, vaccinating and prodding. The heifer was then left undisturbed for the remainder of the 45 s (post-contact). Following the post-contact period, heart rate was again measured (post-treatment) for purpose of comparison with initial values. After recording the post-treatment heart rate, the transmitter electrodes and the halter and blindfold (if present) were removed and the animal was released from the head gate. 2.2. Experiment 2 Ninety three commercial beef calves, predominantly Hereford or Hereford crosses (mean 92.9 ± 1.96 days of age) were used in a single, 1-day trial. All animals were randomly assigned (balanced for gender) to either visual restriction (blindfold) (n = 46) or no visual restriction (control) (n = 47). Vision was restricted in the same manner as in Experiment 1. Behavioral response to treatment was quantified by measuring the amount of movement and the number of vocalizations recorded while the calves were restrained and on their side using a calf tilt table. 2.2.1. Movement measurement Movement was objectively quantified using an electronic movement-measuring device (MMD), first described by Stookey et al. (1994). The MMD was attached to the load cells of an electronic weigh scale. The tilt table was secured onto the scale platform. The MMD digitally sampled the analog voltage signal from the scale at 122 discrete time intervals per second. A peak was recorded whenever a trend towards increasing or decreasing voltage over 10 or more consecutive sample intervals was reversed. The number of peaks is indicative of the relative amount of movement made by the calf during the test period. After the 1-min test procedure, the number of peaks was displayed by the device and was recorded. Previous work showed that the number of peaks is correlated to the amount of movement that can be measured via video analysis (Stookey et al., 1994) and has also been correlated to heart rate (Waynert et al., 1999). 2.2.2. Testing procedure On the day of the experiment, 93 cow–calf pairs were moved from pasture into a holding pen. Animals were subsequently moved to a sorting area where cows and calves were separated. Calves were moved individually through a curved race to the indoor testing facility, where they were restrained using a calf tipping table (High Hog Manufacturing Co., Calgary, AL). The calf tipping table is similar in function to a head gate and squeeze, but can be tilted so that the animal can be held on its side, parallel to the ground. It is used for
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standard management practices that require head and side restraint, such as feet trimming of sheep or dehorning and castration of calves. The calves had previously been vaccinated and the bull calves were castrated the week prior to the experiment. However, the calves had never been restrained with a tipping table and were na¨ıve to the facility prior to the experiment. Only one calf was tested at a time although there was often more than one calf waiting in line within the indoor facility. The 1-min test period began as soon as the calf was restrained in the table and secured in the tilted position. After 30 s, experimenters positioned on either side, approached the animal. One experimenter grasped the animal’s ear while the other poked the neck with a finger to simulate ear tagging and vaccination. A third experimenter recorded the number of times the test animal vocalized during the procedure. After the 1-min test period, the halter and blindfold (if used) was removed and the animal released. All personnel moved and stood in the same manner and position during the testing of each calf. 2.3. Statistical analysis In the first experiment, the association between treatment status, sample time (day 0–4), trial repetition, animal weight and the various outcome measures were analyzed using a generalized estimating equations (GEE) method to account for the repeated measures design. Data were analyzed using a statistical computer software program (SAS, Version 8.2 for Windows (PROC GENMOD), SAS Institute, Cary, North Carolina, USA). Model specifications included a normal distribution, identity link function, repeated statement with subject equal to animal tag number and an AR(1) correlation structure. Variables remaining in the final multivariate model at P < 0.05, based on the robust empirical standard errors produced by GEE analysis, were considered statistically significant. The main-effects model was assessed for first-order interactions were treatment, repetition or time remained in the model with P = 0.05 for at least two of the variables in the GEE analysis. Only interactions significant as P < 0.05 are reported. Model diagnostics included visual examination of the raw and standardized residuals (SAS Institute Inc., 1997, pp. 247–319). The residuals were plotted against predicted values of each observation. Rankit plots and Wilk–Shapiro tests were used to assess the normality of the residuals. The ratio of the final-model deviance to the model degrees of freedom was also examined (SAS Institute Inc., 1997, pp. 247–319). In the second experiment, the results were analyzed using a general linear model to test for treatment effects. Calf age and weight were included as co-variates in the model statement. Statistical analysis was performed using Statistix, Version 4.1 (Analytical Software, 1996, Tallahassee, FL, USA).
3. Results 3.1. Experiment 1 The average heart rate of heifers prior to treatment was 105.9 ± 3.7 bpm and did not differ significantly between experimental groups (Fig. 2A). By the end of the 45-s treatment
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period heart rate had fallen to an average of 95.0 ± 4.6 bpm, with no significant difference between experimental groups (Fig. 2B, P > 0.05). However, there was a trend for the difference between pre- and post-treatment heart rates to be greater for blindfolded than control animals; average decrease 16.3 ± 3.2 bpm and 14 ± 2.9 bpm, respectively (Fig. 2C, P = 0.184). Blindfolded heifers exerted a lower maximal force against the head gate than nonblindfolded animals, during the pre-contact (Fig. 3A, P < 0.0001) and contact periods (Fig. 3B, P = 0.0147). During the post-contact period there was a trend for the blindfolded heifers to exert less force against the head gate (Fig. 3C, P = 0.07). Maximal forces declined over the 4 days of the trial across all measurement periods (P < 0.001). The mean force exerted against the head gate did not follow the same pattern as the maximum force data. There was no significant difference in mean force exerted against
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Fig. 3. The average maximal force exerted against the head gate, compared by treatment and by day during a 45-s period of restraint. The period was divided into three distinct phases: (A) 0–15 s of restraint prior to touching (contacting) the heifer (P < 0.0001 for treatment and for day); (B) time period when experimenters made contact with the animal and manipulated it in a sham ear tagging, vaccinating and prodding procedure (P < 0.01 for treatment; P < 0.0001 for day); (C) time period, post-contact, until the total 45 s of restraint had elapsed (P = 0.07 for treatment).
the head gate between treatment groups during any of the three testing periods (Fig. 4). 3.2. Experiment 2 Calves that were blindfolded, while restrained on a tilt table, displayed significantly less movement as measured by the MMD than the control group (15.17 ± 3.0 MMD peaks for blindfold compared with 26.8±2.9 peaks for control, during 1 min of recording, P < 0.01). However, the mean number of vocalizations that occurred during the 1-min test period did not differ significantly between treatment groups (1.04 ± 0.53 vocalizations for blindfold, 1.32 ± 0.42 for control, NS).
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Fig. 4. The mean force exerted against the head gate compared by treatment and by day during a 45-s period of restraint. The period was divided into three distinct phases: (A) 0–15 s of restraint prior to touching (contacting) the heifer; (B) time period when experimenters made contact with the animal and manipulated it in a sham ear tagging, vaccinating and prodding procedure; (C) time period, post-contact, until the total 45 s of restraint had elapsed.
4. Discussion The present study provides evidence that blindfolding may be of value in an animal production environment as a means to calm animals during a task which requires restraint. Although heart rate tended to decrease more over a 45-s test period for blindfolded heifers than it did for control animals (see Fig. 2C), the pre-treatment heart rates were uniformly high. It may be that the 45-s interval between pre- and post-treatment measurements was insufficient to allow heart rate to decline to a level where treatment differences would become significant. Andrade et al. (2001) detected a significant reduction in heart rate for blindfolded cattle, but they restrained and blindfolded the cattle for 3 min. It is possible that a longer period of restraint with repeated or later measurement of heart rates would have revealed a treatment difference. However, our rationale in these
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experiments was to measure responses to a simulated ear tagging and vaccinating procedure. Our experience is that these tasks can easily be performed in 15 s by two experienced operators working together. In Experiment 1 we wanted to measure exertion forces during this 15-s period and also have equivalent measurements before and after the handling treatment was applied. Thus strain gauge data were recorded during the whole of this 45-s period and later partitioned into before, during and after handling data. Our heart rate measurements were intended to be representative of the animals’ responses to this procedure, rather than to an artificially prolonged period of restraint. Thus heart rate was sampled for 15 s before and after the 45-s strain gauge measurement period. In Experiment 2, the 1-min measurement period was the sampling time required by the movement measuring device. This machine has an internal read-only memory chip preprogrammed to sample for that period of time. The 1-min sampling period gave a good indication of the animals’ response to this type of restraint and the simulated ear-tagging/vaccinating treatment. Much longer sampling, in either experiment, would have entailed a risk that we would have been measuring whether the blindfold influenced the time taken to habituate to the testing environment, rather than the response to handling. Previous rough handling can make animals more excitable and more resistant to subsequent handling (Grandin, 1993). Heart rate measurements, made at short time intervals, may not be the most sensitive indicator of the animals’ fear responses in this type of situation. The novelty of the facility and of the blindfold, coupled with a lack of significant handling experience prior to the testing procedure, may have masked any potential effect of blindfolding on heart rate. Andrade et al. (2001) reported that heart rate dropped significantly more for blindfolded cattle during restraint, but their cattle had been previously handled in the same facility a minimum of 18 times. Since commercial beef cattle are restrained infrequently, blindfolding should be effective during each restraint regardless of the frequency the cattle are handled and despite their previous experience. In our two experiments, we did detect a major benefit of using a blindfold during restraint, specifically a reduction in movement. This occurred in both heifers and calves. Movement or struggle against the head gate or a tilt table can be interpreted either as an indication of the animal’s motivation to escape the situation or reflects the relative calm an animal displays during restraint. Using strain gauges we were able to measure objectively the animals’ response without observer bias. Temperament scores were previously reported to be lower for blindfolded cattle (Andrade et al., 2001), but such scores have the inherent disadvantage of being subjective and vulnerable to observer bias. In addition to the effect of the two treatments, the act of fitting the blindfold or halter may contribute to the forces subsequently measured, especially the first measurement. So too might the period immediately following the exclusion of visual stimuli, which would only affect the blindfolded group. The average maximum forces exerted by blindfolded heifers were significantly less than controls both prior to and during contact with the handler (Fig. 3). The effect of blindfolding on behavior therefore was detectable even before the manipulation (which we assumed would be the more aversive part of the treatment) commenced. However, the mean values, which incorporate long periods of stillness for animals in both treatments, did not differ. Maximum force may be a more useful indicator of response to treatment, as mean values are attenuated by long periods that most animals spent inactive, even the highly agitated ones. Maximum force values demonstrate that when struggle did occur, the force exerted by blindfolded animals was significantly less than control.
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A possible explanation for these results is that blindfolded animals might struggle less during restraint not because they are calmer, but because they are more fearful. Tonic immobility is a fear-induced state, well documented in species such as the domestic chicken (Jones and Satterlee, 1997). We do not see any evidence that something similar occurred in these experiments. Since there was no difference in heart rate between treatment groups, the physiological evidence would suggest that blindfolded animals were not more fearful than non-blindfolded animals. Kilgour (1975) reported that only 1 cow in 50 becomes immobile in response to a fear-provoking situation. This further strengthens the suggestion that the observed decrease in movement was not due to an increase in fear. Reduction of ambient light intensity has been documented to have a calming effect on species such as the domestic chicken and the red deer (Pollard and Littlejohn, 1994; Jones et al., 1998a). It has been suggested that blindfolded animals are calmer during restraint because all visual communication with their environment has been eliminated (Fowler, 1995). Animals in the current experiments were not deprived of olfactory or auditory cues and may have been able to use these to detect the presence of humans. However, as a prey species, cattle are strongly dependent on vision to assess their environment. With this sense removed, blindfolded animals may have had no meaningful way of evaluating their environment and responded by decreasing their level of struggle. One source of anxiety for restrained animals is the extreme penetration of their flight zone by human handlers and their inability to flee (Grandin, 1993). Cattle and sheep move more calmly through a chute system with solid sides, when people are within their normal flight distance, but unseen (Grandin, 1998). Blindfolded cattle may have struggled less because they were not as aware of handlers within their flight zone and therefore did not feel as great a need to flee. In Experiment 1, the effect of the blindfold on the maximal force exerted against the head gate was apparent on day 1. Thus the blindfold treatment appeared to be effective in reducing the amount of struggling shown by animals, on their first exposure to the facility and these conditions. Over time the average maximal force exerted decreased for all three periods, suggesting that both control and treated animals were habituating to the testing situation. This suggests that blindfolds may be most effective for use on animals that are relatively unaccustomed to being handled or to the handling facility itself. Calves that are restrained in a positive manner are easier to handle and restrain as adults (Boivin et al., 1994). Using a blindfold on calves restrained in a tilt-table may make the experience less unpleasant for the calf thereby easing the stress of subsequent handling. Restricting visual input may also serve to decrease handling injuries. Reducing the amount an animal struggles should also reduce the need to compress the animal, say within a hydraulic squeeze, thereby reducing injuries due to over squeezing. Cattle that struggle will likely spend more time in the handling system than more passive animals, because the time to complete the procedure can be disrupted by their movement. Given that the majority of bruising injuries occur while cattle are in the race (Jarvis et al., 1996), it follows that the longer an animal is in the handling system, the greater the risk of injury. The current experiment did not distinguish between the benefits of removing all visual input using a blindfold, from the more specific effect of removing the sight of humans from the visual field. Future experiments could examine the effect of partial blinders on
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restrained cattle. Partial blinders would serve to restrict an animal’s visual field and might remove humans from the equation rather than eliminate vision entirely. This may help to determine if the calming effect of the blindfold was due to the absence of all visual information or rather the removal of the human threat. Previous work has shown that when human voices alone are removed from the handling facility, cattle are calmer (Waynert et al., 1999). The number of vocalizations made by blindfolded calves during restraint was no different from controls. The actual number of vocalizations made by blindfolded calves was less than the total count for controls, but the wide variation between calves essentially eliminated any treatment effects. In general, both groups vocalized at a very low level, probably because no painful procedure was imposed. It has been previously established that the propensity for cattle to vocalize is influenced by phenotype (Watts and Stookey, 2001) and by painful procedures (Watts and Stookey, 1999). While vocalizations or lack of vocalizations may be a useful indicator of the animal’s experience of a procedure (Watts and Stookey, 2000), our results indicate that the difference between being blindfolded or not during restraint, without pain, is insufficient, from the calf’s perspective, to elicit a different vocal response. It would be interesting to see if a painful procedure was perceived differently, as expressed by vocalizations, depending upon whether or not the animal was blindfolded.
5. Conclusion These results indicate that it may be advantageous to cattle and to their handlers to blindfold the animals during the periods of restraint required for some routine management procedures. Although the current study failed to demonstrate any clear effect of blindfolding on reducing heart rate and the number of vocalizations, blindfolding is still considered to be a beneficial procedure as it appears to reduce an animals’ struggling and the associated risk of injury to both animal and handler.
Acknowledgements Funding for this project was provided by the Western College of Veterinary Medicine through the Inter-provincial Undergraduate Student Summer Research Award and the Saskatchewan Agricultural Development Fund. Special thanks are extended to the staff of the Goodale Research Farm and to Cheryl Waldner for her help with the statistical analysis.
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Ewbank, R., 1961. The behaviour of cattle in crushes. Vet. Rec. 73, 853–856. Ewbank, R., 2000. Handling cattle in intensive systems. In: Grandin, T. (Ed.), Livestock Handling and Transport. CABI Publishing, New York, NY, pp. 87–102. Fowler, M.E., 1995. Tools of restraint. In: Restraint and Handling of Wild and Domestic Animals, second ed. Iowa State University Press, Ames, Iowa, pp. 7–17. Grandin, T., 1980. Livestock behaviour as related to handling facilities design. Int. J. Stud. Anim. Prob. 1 (1), 33–52. Grandin, T., 1990. Bovines: rules of restraint. Large Anim. Vet. 45 (4), 24–28. Grandin, T., 1993. The effect of previous experiences on livestock behavior during handling. Agri-Practice 14 (4), 15–20. Grandin, T., 1998. Handling methods and facilities to reduce stress on cattle. In: Food Animal Practice, Vol. 14 (2). Veterinary Clinics of North America, pp. 325–341. Grandin, T., 2000. Handling facilities and restraint of range cattle. In: Grandin, T. (Ed.), Livestock Handling and Transport Livestock, second ed. CABI Publishing, New York, NY. pp. 103–125. Haigh, J.C., Friesen, R.W., 1995. A handling system for white-tailed deer (Odocoileus virginianus). J. Zoo Wildlife Med. 26 (2), 321–326. Heffner, H.E., Heffner, R.S., 1992. Auditory perception. In: Phillips, C., Piggins, D. (Eds.), Farm Animals and the Environment. CAB International, Oxon, UK, pp. 159–184. Jarvis, A.M., Messer, C.D.A., Cockram, M.S., 1996. Handling, bruising and dehydration at the time of slaughter. Anim. Welfare 5, 259–270. Jones, R.B., Satterlee, D.G., 1997. Restricted visual input reduces struggle in shackled broiler chickens. Appl. Anim. Behav. Sci. 52, 109–117. Jones, R.B., Hagedorn, T.K., Satterlee, D.G., 1998a. Adoption of immobility by shackled broiler chickens: effects of light intensity and diverse hooding devices. Appl. Anim. Behav. Sci. 55, 327–335. Jones, R.B., Satterlee, D.G., Cadd, G.G., 1998b. Struggling responses of broiler chickens shackled in groups on a moving line: effects of light intensity, hoods, and ‘curtains’. Appl. Anim. Behav. Sci. 58, 341–352. Kilgour, R., 1975. The open-field test as an assessment of the temperament of dairy cows. Anim. Behav. 23, 615–624. Lay, D.C., Friend, T.H., Grissom, K.K., Hale, R.L., Bowers, C.L., 1992a. Novel breeding box has variable effects on heart rate and cortisol response of cattle. Appl. Anim. Behav. Sci. 35, 1–10. Lay, D.C., Friend, T.H., Randel, R.D., Bowers, C.L., Grissom, K.K., Jenkins, O.C., 1992b. Behavioural and physiological effects of freeze or hot iron branding on crossbred cattle. J. Anim. Sci. 70, 330–336. Mitchell, G., Hattingh, J., Gsnhao, M., 1988. Stress in cattle assessed after handling, after transport and after slaughter. Vet. Rec. 123, 201–205. Pollard, J.J., Littlejohn, R.P., 1994. Behavioural effects of light conditions on red deer in a holding pen. Appl. Anim. Behav. Sci. 41, 127–134. SAS Institute Inc., 1997. SAS/SAT Software: Changes and Enhancements through Release 6.12. SAS Institute Inc., Cary, NC. Schwartzkopf-Genswein, K.S., Stookey, J.M., Welford, R., 1997. Behavior of cattle during hot-iron and freeze branding and the effects on subsequent handling ease. J. Anim. Sci. 75, 2064–2072. Thierman, J.L., Crowe, T.G., Stookey, J.M., Valentine, B., 1999. Quantification of the response of elk during velvet antler removal. Can. Agr. Eng. 41, 233–237. Stookey, J.M., Nickel, T.L., Hanson, J., Vandenbosch, S., 1994. A movement-measuring-device for objectively measuring temperament in beef cattle and for use in determining factors that influence handling. J. Anim. Sci. 1 (Suppl.), 207. Watts, J.M., Stookey, J.M., 1999. Effects of restraint and branding on rates and acoustic parameters of vocalization in beef cattle. Appl. Anim. Behav. Sci. 62, 125–135. Watts, J.M., Stookey, J.M., 2000. Vocal behaviour in cattle: the animal’s commentary on its biological processes and welfare. Appl. Anim. Behav. Sci. 67, 15–33. Watts, J.M., Stookey, J.M., 2001. The propensity of cattle to vocalise during handling and isolation is affected by phenotype. Appl. Anim. Behav. Sci. 74, 81–95. Waynert, D.F., Stookey, J.M., Schwartzkopf-Genswein, K.S., Watts, J.M., Waltz, C.S., 1999. The response of beef cattle to noise during handling. Appl. Anim. Behav. Sci. 62, 27–42. White, J., 1990. Raptor restraint. J. Assoc. Avian Vet. 4 (2), 91–92.
The effects of blindfolding on behavior and heart rate in beef cattle during restraint Kelly D. Mitchell, Joseph M. Stookey∗ , Darrell K. Laturnas, Jon M. Watts, Derek B. Haley, Tara Huyde Department of Large Animal Clinical Sciences, University of Saskatchewan, Western College of Veterinary Medicine, Saskatoon, Sask., Canada S7N 5B4 Accepted 6 July 2003
Abstract Use of a blindfold or hood during handling and restraint has been suggested for many wild and captive animals. Two experiments were conducted to determine the effects of blindfolds on beef cattle during restraint. In Experiment 1, 60 beef heifers, na¨ıve to the restraint facility, were randomly assigned to either visual restriction (blindfold) or no visual restriction (control) and tested daily during a 4-day trial to determine the effects during restraint. Heart rate (HR) was measured via telemetry, during a baseline period prior to treatment and continuously recorded during a 1-min period of restraint, which included some manipulation of the animal. Manipulation was initiated 15 s into the restraint period. Two persons simultaneously approached the animal one on either side, grasped the ears, and touched the neck, sides and rump to simulate normal management tasks. Electronic strain gauges attached to the head gate quantified the animal’s struggle during this procedure. These were used to determine the average and maximum exertion forces upon the head gate during restraint. The association between treatment, sample time (day 0–4), animal weight and the various outcome measures were analyzed using a generalized estimating equation method. Mean HR of heifers did not differ at the end of the treatment (95.04 ± 4.66 bpm ) (P = 0.64), but the HR tended to decrease more for blindfolded heifers compared to controls during restraint (average decrease 16.3 ± 3.2 bpm and 14 ± 2.9 bpm, respectively) (P = 0.10). The average exertion forces applied by blindfolded heifers against the head gate were 23% lower (P < 0.05) during the 1-min period and maximum forces were 28% lower (P < 0.01). Heart rate and exertion forces declined over the 4 days for both treatment groups (P < 0.001). In Experiment 2, 93 commercial beef calves (average age 92.9 ± 2.0 days) were randomly assigned to either visual restriction (blindfold) (n = 46) or no visual restriction (control) (n = 47) treatments. Behavioral responses to treatment were quantified by measuring the amount of movement and recording the number of vocalizations while the calves were restrained for 1 min on a calf tilt table. Movement was recorded by an electronic device attached to a weighing platform that held the tilt table. After 30 s of restraint, one experimenter touched the animal’s ear while the ∗
Corresponding author. Tel.: +1-306-966-7154; fax: +1-306-966-7159. E-mail address: [email protected] (J.M. Stookey). 0168-1591/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2003.07.004
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other touched the neck, to simulate ear tagging and vaccination. Blindfolded calves moved 44% less than the control group (P < 0.01). However, the number of vocalizations that occurred during the 1-min test period did not differ (P > 0.05) between treatments. Overall, blindfolding cattle reduced the amount of struggle and tended to lower heart rate. Therefore, blindfolding may be advantageous during the routine invasive procedures commonly performed on cattle. © 2003 Elsevier B.V. All rights reserved. Keywords: Behavior; Blindfold; Cattle; Handling; Heart rate; Restraint; Vocalizations
1. Introduction Cattle are known to show physiological and behavioral changes in response to standard livestock handling and restraint techniques. In the absence of other painful stimuli, restraint alone can increase the heart rate and plasma cortisol concentrations of cattle to levels comparable to those recorded during transport and slaughter (Mitchell et al., 1988; Lay et al., 1992b). Ewbank (1961) observed that the majority of cattle restrained in a head gate became highly agitated and most struggled to withdraw their head or lunged forward when stimuli were applied to the neck. Attempts to escape and physical contact with the head gate can result in pain and injury, including bruising to the neck and back region (Grandin, 1998). Not only does increased carcass bruising represent an economic loss, it may also be an indicator of compromised animal welfare (Jarvis et al., 1996). Cattle have limited binocular vision, but roughly a 330◦ field of vision, which helps them to be keenly aware of visual stimuli in their environment. The most sensitive region in the retina is the horizontal foveal streak, which allows for a better means of detecting movement across a broader visual field (Heffner and Heffner, 1992). A subjective consideration of the animals’ visual perception has been a major factor in the design of handling facilities (Grandin, 1980). Cattle balk less and move calmly through handling systems with solid sides, which block the animal’s view of the handler (Grandin, 1998). Heifers restrained in a dark breeding box had lower plasma cortisol concentrations than heifers restrained in a conventional squeeze chute (Lay et al., 1992a). However, it is difficult to incorporate the dark box effect within a typical cattle head gate and race system used for restraint and handling. Blindfolding the animal once it is restrained in a head gate may be a practical method for taking advantage of the effects gained in the dark breeding box. Restriction of an animal’s visual field by means of a blindfold has been suggested for use during the handling and restraint of many wild and captive animals (Fowler, 1995). Covering of the head to block visual stimuli has been reported to keep raptors calm during restraint (Campbell, 1991; White, 1990). Struggling and wing flapping is greatly reduced in shackled and inverted broiler chickens, if a hood is pulled over the animal’s head prior to inversion (Jones and Satterlee, 1997; Jones et al., 1998a,b). Blindfolds are commonly used during the restraint and removal of antler from farmed elk (Thierman et al., 1999). Blindfolding of white-tailed deer is recommended to ease handling for routine procedures (Haigh and Friesen, 1995). Though it has been mentioned that blindfolds have a calming effect on restrained cattle (Grandin, 1990; Grandin, 2000; Ewbank, 2000), we are aware of only one controlled study
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that has provided data to support this claim (Andrade et al., 2001). The objective of the present study was to examine the potential calming effect of a blindfold on cattle during restraint.
2. Materials and methods 2.1. Experiment 1 Sixty yearling commercial beef heifers (mean weight 389.5 ± 3.33 kg) were divided into two groups for replication of the experiment. The heifers had been purchased from a local auction market and were of unknown origins. The main breed types represented were Hereford, Charolais, black Angus and their crosses. They were brought to the University of Saskatchewan Goodale Farm two weeks prior to being used in the experiment. All animals were housed outside and were na¨ıve to the facility where testing occurred. In each replicate 30 animals were randomly assigned to visual restriction (blindfold) (n = 15) or no visual restriction (control) (n = 15). A dark towel, held in place by a nylon halter, was used to restrict the vision of experimental animals. The blindfold was secured by fitting a standard nylon halter around the ears and muzzle of the animal and placing a dark towel under the straps of the halter so that it completely covered the eyes and the plane of the face, leaving ears, nose and mouth uncovered (Fig. 1). The blindfold was believed to block the heifers’ vision completely, as there was no response to movement in the normal field of view. Control animals were fitted with the standard nylon halter only, leaving the eyes and plane of the face uncovered. Fitting of the halter or blindfold took between 10 and 20 s.
Fig. 1. Photograph of an experimental animal with the blindfold treatment applied.
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Heart rate was measured as an indicator of the animal’s physiological response to the testing situation. The force exerted on the head gate during restraint was also measured and served as an objective measurement of the animal’s behavioral response. 2.1.1. Heart rate measurement Heart rate was recorded using remote telemetry (Paragon 420 Cardiac Monitoring System and TM8 Patient Transmitters: Quinton Instrument, Seattle, WA, USA) Heart rate was subsequently calculated from the ECG printout. The distance in mm (d) spanned by several interbeat intervals (n) was measured from the peak of the 0th to the nth QRS complex. Given that the paper moved at a constant speed of 1500 mm/min (s), heart rate was determined according to the following formula: HR = (n/d × s). Three days before testing, the heifers were moved through a separate chute and caught in a different head gate than the one used during the experiment. While restrained, two surgical staple (5.7 mm × 3.8 mm APOSE∗ ULC Disposable skin staples, American Cyanamnid, Wayne, NJ, USA) one on either side were inserted into the dermis of each heifer to serve as electrodes. The sites were shaved prior to the insertion of the staples. One staple was placed approximately 30 cm dorsal and 5 cm caudal to the right olecranon and the other approximately 5 cm both dorsal and caudal to the left olecranon. The electrode leads from the remote heart rate transmitter were fitted with alligator clips that were fastened to the surgical staples during the testing procedure. The heart rate transmitter was fixed to the top of the squeeze chute, near the head gate. Staples remained in the heifers for the duration of the experiment and were removed following testing on the fourth day. The animals appeared to suffer little or no pain or discomfort from the staples, given their lack of response upon application, during testing and at removal. 2.1.2. Strain gauge Several days prior to the experiment, the head gate was equipped with instruments, similar to those described by Schwartzkopf-Genswein et al. (1997), which could quantify the force exerted against the head gate. One pair of strain gauges was attached to the head gate at approximately the height of the animals’ neck, making it possible to measure the force exerted when an animal moved forward or backward in the chute. Output signals from the strain gauges were measured in volts (V). Signals from the strain gauges were amplified by a signal conditioner (Model 2310 Signal Amplifier, Vishay Measurement Group, Raleigh, NC) and stored as a single output file that included the animal identification, sample time and the digitized output. Average and maximum exertion force measurements were obtained from the digitized output of the strain gauge for each of three separate measurement periods. 2.1.3. Testing procedure Animals were tested daily on four consecutive days at roughly the same time each day. Each animal received the same treatment each day. Heifers were moved from their home pen and run single file through a curved race into the indoor testing facility. Only one animal at a time was inside the testing facility. The remaining animals were held either in the curved race or the connecting crowd pen.
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Once the animal was restrained in the head gate, the alligator clips of the electrode leads were attached to the surgical staples. Experimenters then positioned themselves one on either side of the animal approximately 1 m lateral to its head, where they remained silent and still. This position was maintained until a baseline heart rate had been established (pre-treatment). The control or blindfold treatment was then applied to the heifer for a period of 45 s. Strain gauge measurements were recorded for the entire 45-s period, and could be divided into three distinct periods of approximately 15 s each. The first 15 s (pre-contact) served to establish the baseline level of force exerted. After 15 s, the two experimenters simultaneously approached the animal from opposite sides and sequentially touched the ear, shoulder, flank and rump (contact) to simulate ear tagging, vaccinating and prodding. The heifer was then left undisturbed for the remainder of the 45 s (post-contact). Following the post-contact period, heart rate was again measured (post-treatment) for purpose of comparison with initial values. After recording the post-treatment heart rate, the transmitter electrodes and the halter and blindfold (if present) were removed and the animal was released from the head gate. 2.2. Experiment 2 Ninety three commercial beef calves, predominantly Hereford or Hereford crosses (mean 92.9 ± 1.96 days of age) were used in a single, 1-day trial. All animals were randomly assigned (balanced for gender) to either visual restriction (blindfold) (n = 46) or no visual restriction (control) (n = 47). Vision was restricted in the same manner as in Experiment 1. Behavioral response to treatment was quantified by measuring the amount of movement and the number of vocalizations recorded while the calves were restrained and on their side using a calf tilt table. 2.2.1. Movement measurement Movement was objectively quantified using an electronic movement-measuring device (MMD), first described by Stookey et al. (1994). The MMD was attached to the load cells of an electronic weigh scale. The tilt table was secured onto the scale platform. The MMD digitally sampled the analog voltage signal from the scale at 122 discrete time intervals per second. A peak was recorded whenever a trend towards increasing or decreasing voltage over 10 or more consecutive sample intervals was reversed. The number of peaks is indicative of the relative amount of movement made by the calf during the test period. After the 1-min test procedure, the number of peaks was displayed by the device and was recorded. Previous work showed that the number of peaks is correlated to the amount of movement that can be measured via video analysis (Stookey et al., 1994) and has also been correlated to heart rate (Waynert et al., 1999). 2.2.2. Testing procedure On the day of the experiment, 93 cow–calf pairs were moved from pasture into a holding pen. Animals were subsequently moved to a sorting area where cows and calves were separated. Calves were moved individually through a curved race to the indoor testing facility, where they were restrained using a calf tipping table (High Hog Manufacturing Co., Calgary, AL). The calf tipping table is similar in function to a head gate and squeeze, but can be tilted so that the animal can be held on its side, parallel to the ground. It is used for
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standard management practices that require head and side restraint, such as feet trimming of sheep or dehorning and castration of calves. The calves had previously been vaccinated and the bull calves were castrated the week prior to the experiment. However, the calves had never been restrained with a tipping table and were na¨ıve to the facility prior to the experiment. Only one calf was tested at a time although there was often more than one calf waiting in line within the indoor facility. The 1-min test period began as soon as the calf was restrained in the table and secured in the tilted position. After 30 s, experimenters positioned on either side, approached the animal. One experimenter grasped the animal’s ear while the other poked the neck with a finger to simulate ear tagging and vaccination. A third experimenter recorded the number of times the test animal vocalized during the procedure. After the 1-min test period, the halter and blindfold (if used) was removed and the animal released. All personnel moved and stood in the same manner and position during the testing of each calf. 2.3. Statistical analysis In the first experiment, the association between treatment status, sample time (day 0–4), trial repetition, animal weight and the various outcome measures were analyzed using a generalized estimating equations (GEE) method to account for the repeated measures design. Data were analyzed using a statistical computer software program (SAS, Version 8.2 for Windows (PROC GENMOD), SAS Institute, Cary, North Carolina, USA). Model specifications included a normal distribution, identity link function, repeated statement with subject equal to animal tag number and an AR(1) correlation structure. Variables remaining in the final multivariate model at P < 0.05, based on the robust empirical standard errors produced by GEE analysis, were considered statistically significant. The main-effects model was assessed for first-order interactions were treatment, repetition or time remained in the model with P = 0.05 for at least two of the variables in the GEE analysis. Only interactions significant as P < 0.05 are reported. Model diagnostics included visual examination of the raw and standardized residuals (SAS Institute Inc., 1997, pp. 247–319). The residuals were plotted against predicted values of each observation. Rankit plots and Wilk–Shapiro tests were used to assess the normality of the residuals. The ratio of the final-model deviance to the model degrees of freedom was also examined (SAS Institute Inc., 1997, pp. 247–319). In the second experiment, the results were analyzed using a general linear model to test for treatment effects. Calf age and weight were included as co-variates in the model statement. Statistical analysis was performed using Statistix, Version 4.1 (Analytical Software, 1996, Tallahassee, FL, USA).
3. Results 3.1. Experiment 1 The average heart rate of heifers prior to treatment was 105.9 ± 3.7 bpm and did not differ significantly between experimental groups (Fig. 2A). By the end of the 45-s treatment
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period heart rate had fallen to an average of 95.0 ± 4.6 bpm, with no significant difference between experimental groups (Fig. 2B, P > 0.05). However, there was a trend for the difference between pre- and post-treatment heart rates to be greater for blindfolded than control animals; average decrease 16.3 ± 3.2 bpm and 14 ± 2.9 bpm, respectively (Fig. 2C, P = 0.184). Blindfolded heifers exerted a lower maximal force against the head gate than nonblindfolded animals, during the pre-contact (Fig. 3A, P < 0.0001) and contact periods (Fig. 3B, P = 0.0147). During the post-contact period there was a trend for the blindfolded heifers to exert less force against the head gate (Fig. 3C, P = 0.07). Maximal forces declined over the 4 days of the trial across all measurement periods (P < 0.001). The mean force exerted against the head gate did not follow the same pattern as the maximum force data. There was no significant difference in mean force exerted against
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the head gate between treatment groups during any of the three testing periods (Fig. 4). 3.2. Experiment 2 Calves that were blindfolded, while restrained on a tilt table, displayed significantly less movement as measured by the MMD than the control group (15.17 ± 3.0 MMD peaks for blindfold compared with 26.8±2.9 peaks for control, during 1 min of recording, P < 0.01). However, the mean number of vocalizations that occurred during the 1-min test period did not differ significantly between treatment groups (1.04 ± 0.53 vocalizations for blindfold, 1.32 ± 0.42 for control, NS).
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4. Discussion The present study provides evidence that blindfolding may be of value in an animal production environment as a means to calm animals during a task which requires restraint. Although heart rate tended to decrease more over a 45-s test period for blindfolded heifers than it did for control animals (see Fig. 2C), the pre-treatment heart rates were uniformly high. It may be that the 45-s interval between pre- and post-treatment measurements was insufficient to allow heart rate to decline to a level where treatment differences would become significant. Andrade et al. (2001) detected a significant reduction in heart rate for blindfolded cattle, but they restrained and blindfolded the cattle for 3 min. It is possible that a longer period of restraint with repeated or later measurement of heart rates would have revealed a treatment difference. However, our rationale in these
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experiments was to measure responses to a simulated ear tagging and vaccinating procedure. Our experience is that these tasks can easily be performed in 15 s by two experienced operators working together. In Experiment 1 we wanted to measure exertion forces during this 15-s period and also have equivalent measurements before and after the handling treatment was applied. Thus strain gauge data were recorded during the whole of this 45-s period and later partitioned into before, during and after handling data. Our heart rate measurements were intended to be representative of the animals’ responses to this procedure, rather than to an artificially prolonged period of restraint. Thus heart rate was sampled for 15 s before and after the 45-s strain gauge measurement period. In Experiment 2, the 1-min measurement period was the sampling time required by the movement measuring device. This machine has an internal read-only memory chip preprogrammed to sample for that period of time. The 1-min sampling period gave a good indication of the animals’ response to this type of restraint and the simulated ear-tagging/vaccinating treatment. Much longer sampling, in either experiment, would have entailed a risk that we would have been measuring whether the blindfold influenced the time taken to habituate to the testing environment, rather than the response to handling. Previous rough handling can make animals more excitable and more resistant to subsequent handling (Grandin, 1993). Heart rate measurements, made at short time intervals, may not be the most sensitive indicator of the animals’ fear responses in this type of situation. The novelty of the facility and of the blindfold, coupled with a lack of significant handling experience prior to the testing procedure, may have masked any potential effect of blindfolding on heart rate. Andrade et al. (2001) reported that heart rate dropped significantly more for blindfolded cattle during restraint, but their cattle had been previously handled in the same facility a minimum of 18 times. Since commercial beef cattle are restrained infrequently, blindfolding should be effective during each restraint regardless of the frequency the cattle are handled and despite their previous experience. In our two experiments, we did detect a major benefit of using a blindfold during restraint, specifically a reduction in movement. This occurred in both heifers and calves. Movement or struggle against the head gate or a tilt table can be interpreted either as an indication of the animal’s motivation to escape the situation or reflects the relative calm an animal displays during restraint. Using strain gauges we were able to measure objectively the animals’ response without observer bias. Temperament scores were previously reported to be lower for blindfolded cattle (Andrade et al., 2001), but such scores have the inherent disadvantage of being subjective and vulnerable to observer bias. In addition to the effect of the two treatments, the act of fitting the blindfold or halter may contribute to the forces subsequently measured, especially the first measurement. So too might the period immediately following the exclusion of visual stimuli, which would only affect the blindfolded group. The average maximum forces exerted by blindfolded heifers were significantly less than controls both prior to and during contact with the handler (Fig. 3). The effect of blindfolding on behavior therefore was detectable even before the manipulation (which we assumed would be the more aversive part of the treatment) commenced. However, the mean values, which incorporate long periods of stillness for animals in both treatments, did not differ. Maximum force may be a more useful indicator of response to treatment, as mean values are attenuated by long periods that most animals spent inactive, even the highly agitated ones. Maximum force values demonstrate that when struggle did occur, the force exerted by blindfolded animals was significantly less than control.
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A possible explanation for these results is that blindfolded animals might struggle less during restraint not because they are calmer, but because they are more fearful. Tonic immobility is a fear-induced state, well documented in species such as the domestic chicken (Jones and Satterlee, 1997). We do not see any evidence that something similar occurred in these experiments. Since there was no difference in heart rate between treatment groups, the physiological evidence would suggest that blindfolded animals were not more fearful than non-blindfolded animals. Kilgour (1975) reported that only 1 cow in 50 becomes immobile in response to a fear-provoking situation. This further strengthens the suggestion that the observed decrease in movement was not due to an increase in fear. Reduction of ambient light intensity has been documented to have a calming effect on species such as the domestic chicken and the red deer (Pollard and Littlejohn, 1994; Jones et al., 1998a). It has been suggested that blindfolded animals are calmer during restraint because all visual communication with their environment has been eliminated (Fowler, 1995). Animals in the current experiments were not deprived of olfactory or auditory cues and may have been able to use these to detect the presence of humans. However, as a prey species, cattle are strongly dependent on vision to assess their environment. With this sense removed, blindfolded animals may have had no meaningful way of evaluating their environment and responded by decreasing their level of struggle. One source of anxiety for restrained animals is the extreme penetration of their flight zone by human handlers and their inability to flee (Grandin, 1993). Cattle and sheep move more calmly through a chute system with solid sides, when people are within their normal flight distance, but unseen (Grandin, 1998). Blindfolded cattle may have struggled less because they were not as aware of handlers within their flight zone and therefore did not feel as great a need to flee. In Experiment 1, the effect of the blindfold on the maximal force exerted against the head gate was apparent on day 1. Thus the blindfold treatment appeared to be effective in reducing the amount of struggling shown by animals, on their first exposure to the facility and these conditions. Over time the average maximal force exerted decreased for all three periods, suggesting that both control and treated animals were habituating to the testing situation. This suggests that blindfolds may be most effective for use on animals that are relatively unaccustomed to being handled or to the handling facility itself. Calves that are restrained in a positive manner are easier to handle and restrain as adults (Boivin et al., 1994). Using a blindfold on calves restrained in a tilt-table may make the experience less unpleasant for the calf thereby easing the stress of subsequent handling. Restricting visual input may also serve to decrease handling injuries. Reducing the amount an animal struggles should also reduce the need to compress the animal, say within a hydraulic squeeze, thereby reducing injuries due to over squeezing. Cattle that struggle will likely spend more time in the handling system than more passive animals, because the time to complete the procedure can be disrupted by their movement. Given that the majority of bruising injuries occur while cattle are in the race (Jarvis et al., 1996), it follows that the longer an animal is in the handling system, the greater the risk of injury. The current experiment did not distinguish between the benefits of removing all visual input using a blindfold, from the more specific effect of removing the sight of humans from the visual field. Future experiments could examine the effect of partial blinders on
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restrained cattle. Partial blinders would serve to restrict an animal’s visual field and might remove humans from the equation rather than eliminate vision entirely. This may help to determine if the calming effect of the blindfold was due to the absence of all visual information or rather the removal of the human threat. Previous work has shown that when human voices alone are removed from the handling facility, cattle are calmer (Waynert et al., 1999). The number of vocalizations made by blindfolded calves during restraint was no different from controls. The actual number of vocalizations made by blindfolded calves was less than the total count for controls, but the wide variation between calves essentially eliminated any treatment effects. In general, both groups vocalized at a very low level, probably because no painful procedure was imposed. It has been previously established that the propensity for cattle to vocalize is influenced by phenotype (Watts and Stookey, 2001) and by painful procedures (Watts and Stookey, 1999). While vocalizations or lack of vocalizations may be a useful indicator of the animal’s experience of a procedure (Watts and Stookey, 2000), our results indicate that the difference between being blindfolded or not during restraint, without pain, is insufficient, from the calf’s perspective, to elicit a different vocal response. It would be interesting to see if a painful procedure was perceived differently, as expressed by vocalizations, depending upon whether or not the animal was blindfolded.
5. Conclusion These results indicate that it may be advantageous to cattle and to their handlers to blindfold the animals during the periods of restraint required for some routine management procedures. Although the current study failed to demonstrate any clear effect of blindfolding on reducing heart rate and the number of vocalizations, blindfolding is still considered to be a beneficial procedure as it appears to reduce an animals’ struggling and the associated risk of injury to both animal and handler.
Acknowledgements Funding for this project was provided by the Western College of Veterinary Medicine through the Inter-provincial Undergraduate Student Summer Research Award and the Saskatchewan Agricultural Development Fund. Special thanks are extended to the staff of the Goodale Research Farm and to Cheryl Waldner for her help with the statistical analysis.
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