| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
ANIMAL PRODUCTION |
* Animal Welfare Program, Faculty of Land and Food Systems, University of British Columbia, Canada; and
Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Canada
 |
Abstract |
|---|
 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Key Words: blind • cattle • flight speed • injection • reactivity score
|
INTRODUCTION |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
). However, neck injections may increase aversion to squeeze chute procedures due to the increased proximity and visibility of the handler (Grandin, 1993b) and the increased duration and level of restraint required to complete a procedure (Van Donkersgoed et al., 1999).
An animal’s response to an injection is dependent on numerous factors. For example, venipunctures increased plasma cortisol concentrations in inexperienced dairy heifers (Hopster et al., 1999). Further, pain associated with insertion of the needle has been attributed to the mechanical pressure on tissues from undiluted drugs (Brazeau et al., 1998) and tissue damage in muscles postinjection (George et al., 1995).
Any experience by cattle linked with human contact can affect fearfulness (Hemsworth, 2003). For example, repeated nonaversive handling of beef cattle has been linked to increased aversion to enter a chute (Schwartzkopf-Genswein et al., 1997). Furthermore, fear increased in animals that learned to associate humans or places with a negative experience (de Passillé et al., 1996; Pajor et al., 2000). In addition, Ewbank (1961) observed that the majority of cattle restrained in a headgate became agitated when stimuli were applied to their neck.
Eyesight, in particular the lateral field (Rehkämper and Görlach, 1997), is important for identifying an aversive situation in cattle (Munksgaard et al., 1997; Rushen et al., 1999). Consequently, installing a solid barrier on the outside of the chute has been recommended to prevent visual contact between the animal and the handler (Grandin, 1993c).
The objectives of this study were to evaluate the aversiveness of 1) the visibility of the stockperson, and 2) a neck injection in beef cattle using different behavioral reactivity measurement techniques.
|
MATERIALS AND METHODS |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
All animals were cared for according to the guidelines set out by the Canadian Council on Animal Care (Olfert et al., 1993).
This study was conducted in January 2005 at the Agriculture and Agri-Food Canada Research Centre (Lethbridge, Alberta, Canada) with 120 Red Angus beef steers (approximately 10 mo of age and 298 ± 2.6 kg of BW). The steers came from a single herd at a local ranch, where they had been previously castrated and vaccinated as calves before they arrived at the research feedlot. Steers were sourced from a single herd to reduce the potential confounding effect of previous experience. Once at the feedlot, they were not administered any other injections, and they had not been exposed to a blind. Steers were randomly assigned to 1 of 12 outdoor pens (14 x 20 m), with a loafing area bedded with straw situated in the middle of the pen. Groups remained stable throughout the experiment. Steers were fed a total mixed ration consisting of 35% barley, 58% barley silage, 5% supplement, 2% premix (DM basis) once daily at 0900 h and received ad libitum access to water. All steers were previously ear-tagged for individual identification.
Experimental Design
A partial crossover design was used to access treatment effects. Before the experiment, steers were randomly assigned to 1 of 4 treatments according to a 2 x 2 factorial arrangement of treatments, with exposure to a blind and administration of an injection yielding: blind/injection (n = 24), blind/sham injection (n = 24), no blind/injection (n = 30), and no blind/sham injection (n = 42) treatment groups that were replicated over 2 d (3 d apart; Table 1).
|
A hydraulic squeeze chute (Cattlelac Handling System, Red Deer, Alberta, Canada), which included a headgate and a weigh scale, was fitted with a curtain (1.8 x 1.9 m) made of a dark blue, opaque fabric that served as the blind in the experiment. The blind was placed such that when drawn closed it prevented steers restrained in the squeeze chute from seeing the stock-person approach and administer a neck injection (or sham injection). In contrast, when the curtain was drawn open, the steer was able to visually observe the stockperson approaching the squeeze chute immediately before and during the injection procedure. All steers had been previously subjected to the squeeze chute, including capture in the head gate and the application of light lateral pressure to ensure immobility a total of 4 times to habituate them to the presence of the closed blind. Stock personnel involved in this study were familiar to the steers and remained constant throughout the study, including the habituation period.
On the day of the experiment, each pen of steers was moved to a holding pen. From the holding pen, the group of steers was moved via a solid-sided, semi-circular chute system (Hi-Hog Parallel Axis Squeeze Chute, Hi-Hog Farm and Ranch Equipment Ltd., Calgary, Alberta, Canada) to the squeeze chute. In the squeeze chute, steers were identified from their unique ear tag, their treatments were applied, and measurements of behavioral reactivity were taken. Steers were managed calmly over the course of the study, which included slow careful handling, no use of electric prods, and minimal noise.
Injection Procedure
The experiment was conducted between 0800 and 1200 h on each of the experimental days. Steers were lightly restrained in the squeeze chute for 20 s (pre-treatment interval), after which the injection or sham injection treatment was applied (treatment interval; lasting 20 s). The steers remained in the chute for another 20 s (posttreatment interval) after the conclusion of the treatment interval, which completed the 60-s testing period, before being released.
A multiple dose syringe (Allflex Canada, St-Hyacinthe, Quebec, Canada) fitted with a 0.41 x 25.4-mm needle was used for the injection. Steers were injected by placing the needle sideways under the skin and delivering 5 mL of sterilized phosphate buffered (pH = 7.5) physiological saline solution subcutaneously. A new needle was used for each injection. For the sham injection, the same procedure was carried out, with the exception that the syringe did not have a needle attached and did not contain saline solution. All stock personnel, including those that gave the injections, operated the headgate, and handled the steers remained the same and maintained the same positions on both days of the experiment.
Visual Reactivity Score
The behavioral reactivity of the steers in the squeeze chute was scored in three 20-s intervals (pretreatment, treatment, and posttreatment intervals) over the 60-s measurement period using a numerical scale (Grandin, 1993a): (1) calm, no movement; (2) slightly restless; (3) squirming, occasionally shaking the squeeze chute; (4) continuous, very vigorous movement and shaking of the squeeze chute; (5) rearing, twisting of the body, and struggling violently. The person who scored the steers in the squeeze chute stood approximately 1.5 m away from the squeeze chute on the side opposite of the blind. This ensured that the person doing the visual scores could not see if the blind was drawn open or closed; however, they could clearly see the steer’s behavioral response.
Electronic Reactivity Score
Movements of the steers in the chute were quantified with a strain gauge system similar to the system described by Schwartzkopf-Genswein et al. (1998, 1997). The strain gauges were mounted on the headgate (one on each side) at approximately the height of the steer’s neck, making it possible to measure the pressure exerted when a steer moved forward or backward in the chute. Output signals from each strain gauge were measured in mV and were amplified by a signal conditioner (Model 2310 signal amplifier, Vishay Measurement Group, Raleigh, NC). A multichannel analog input board (Model CIO-DAS08, Measurement Computing, Middleboro, MA) was used to retrieve and digitize data from the strain gauges. All digitized signals were captured onto a personal computer at a rate of 20 samples • channel–1•s–1. This sampling rate produced an accurate representation of the analog signal without providing an overwhelming number of data points. The DAS Wizard software (ComputerBoards, Middleboro, MA) was used to collect and export the data into a Microsoft Excel spreadsheet (Microsoft, Redmond, WA).
The exported data were summarized using a computer program written in Visual Basic (Microsoft) and run in SAS (SAS Inst. Inc., Cary, NC). Data from each strain gauge were collected, reported, and summarized in 1 of 2 ways: the first included the entire 60-s period while the steers were in the squeeze chute, and the second was for the three 20-s intervals as described previously for the visual reactivity scores. To account for individual variation in steer movement while restrained in the squeeze chute, a baseline value was calculated for each steer on each test day using the mean number of peaks within the pretreatment interval while the steers were held without being disturbed. The variables calculated included the number of peaks (defined as a change in direction of the digitized signal value) above or below and the total number of peaks above and below the baseline (pretreatment) mean. The number of peaks is an indication of how much an animal is moving in the chute; the more the animal moves, the greater the number of peaks generated. The maximum millivolt reading or exertion force above the baseline mean as well as the duration of time (s) the exertion force stayed above or below the baseline and the total time the exertion forces stayed above and below the baseline mean were also calculated. The exertion force measurements are an indication of how much pressure the steers are applying on the head gate as they move forward or backward in the chute; the greater the exertion force, the more forceful the escape response by the steers. The electronic system measures whole body movement and not just movement specific to the neck region.
Flight Speed Test
Flight speed was measured using an electronic system described previously by Müller and von Keyserlingk (2006). The flight speed measuring device consisted of 2 light-beam generators and reflectors that were positioned on stands, a timer, and a laptop computer. The first stand was positioned 1.55 m from the exit of the squeeze chute, and the second stand was 2.22 m beyond the first stand. The stands were 0.9 m above ground to record flight speed of the steer at head level. Upon release from the chute, the steer proceeded down a grooved concrete alley (8.2 x 2.1 m) at its own pace and broke the first light beam, starting the timer. When the steer broke the second beam, the timer stopped. The time it took for the steer to move the 2.22 m between the 2 light-beams was used to calculate flight speed (m/s). The subject could not see other steers while proceeding down the flight speed alley. Once a steer had moved along the alley, it was returned to its pen. Flight speed measurements were missed for 39 steers on the first day, as follows: blind/injection (n = 7); blind/sham injection (n = 6); no blind/injection (n = 12); and no blind/sham injection (n = 12); and from 2 steers on the second day, as follows: blind/injection (n = 1); and blind/sham injection (n = 1), due to problems encountered with the data capture software.
Statistics
Analyses were performed using SAS. Data collected over the 2-d study were combined due to the partial crossover design and lack of day effect (P > 0.05). The MIXED procedure was used with injection, blind, and their interactions as fixed effects and steer as the random effect, for flight speed, visual, and electronic reactivity scores. The experimental unit was steer. Treatment comparisons were made between steers as well as within steers by day for comparison of pretreatment and postinterval behavior for the reactivity scores. Injection x blind interactions were not significant (P > 0.05) for flight speed, visual, or electronic reactivity scores, and therefore only the main effects were discussed. A Kruskal-Wallis Test was used to make treatment group comparisons for the visual reactivity score data due to the ordinal nature of the data. Spearman’s rank correlation was used to calculate the relationship between individual steer scores at different time intervals while the steer was confined in the squeeze chute. Differences were considered significant at P < 0.05, and trends were reported at P < 0.10.
|
RESULTS |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Neither the blind nor the injection or their interactions affected (P > 0.40) the flight speed of the steers overall (Table 2) or on d 1 or 2 of testing. Furthermore, flight speed was consistent between the repeated measurements taken from the same steers across both days (r = 0.77; P < 0.001; n = 80).
|
No blind x injection interaction effects were observed (P > 0.10) over the 60-s test or for any of the intervals within that period. The average visual reactivity score over the 60-s test (mean score) was greater (P < 0.01; Table 2
) for both those steers exposed to the blind and given the actual injection treatments compared with the sham procedures. During the pre- and posttreatment intervals, steers had greater (P < 0.005) scores when the blind was used than when it was not (Table 2). However, there was no difference (P = 0.20) in the reactivity scores between the blind and no blind groups during the treatment interval. In contrast, steers receiving an actual injection had greater (P = 0.002) reactivity scores than those subjected to the sham injection during the treatment interval and tended (P = 0.07) to have a greater reactivity score during the posttreatment interval. No difference (P = 0.40) in reactivity score of injected and sham-treated steers was observed in the pretreatment interval (Table 2).
When visual reactivity scores were compared between intervals the posttreatment interval was greater (P < 0.04; Table 3) than the treatment intervals. Neither the treatment nor the posttreatment intervals were different from the pretreatment interval.
|
Electronic Reactivity Score
No blind x injection interaction effects were observed (P > 0.10) over the 60-s test or for any of the intervals within that period (Table 2). Treatment effects on steer reactivity, as measured by the strain gauge system over the 60-s test, were in contrast to the visual score results made over the same period. The number of peaks above the baseline mean and total number of peaks (above and below); the total duration of exertion force (above and below) as well as the duration of force above the baseline mean were all greater (P < 0.05; Table 2) in the absence of the blind. No differences (P > 0.10) were observed in any electronic reactivity score parameter between the injection and sham injection treatments over the 60-s test period.
Within the pretreatment interval the maximum exertion force was greater (P = 0.04; Table 2) for the group not exposed to the blind. No treatment (blind or injection) differences (P > 0.10; Table 2) were observed in any of the other electronic score parameters.
During the treatment interval, steers not exposed to the blind were more reactive than those exposed to the blind. This was supported by the fact that the no blind group had greater (P < 0.05; Table 2) scores than the blind group for the following parameters: number of peaks above the baseline mean, total duration of force, and the duration of force above the baseline mean. No electronic reactivity score differences were observed between the injection and sham injection treatments (P < 0.10; Table 2).
Contradictory results were obtained within the post-treatment interval. The maximum exertion force was greater (P = 0.02; Table 2) for steers exposed to the blind than those that were not. However, there was a tendency (P = 0.07; Table 2) for the no blind group to have a greater score for total number of peaks above and below the baseline mean. Consistent with the other intervals was the absence of a treatment difference (P > 0.10; Table 2) associated with the injection and sham injection procedures.
Differences (P < 0.01) in the electronic scores were found between the pretreatment, treatment, and post-treatment intervals (Table 3). All parameters with the exception of maximum exertion force were greater (P < 0.001) during the posttreatment interval than the pretreatment interval. Maximum exertion force during the treatment interval was greater (P < 0.001) than both pre- and posttreatment scores. Posttreatment scores were also greater (P < 0.001) than the treatment scores for the number of peaks above, below, and total from the baseline mean. Scores were not different between the posttreatment and treatment scores for any of the duration of force parameters. All pretreatment values were always less (P < 0.001) than treatment values.
|
DISCUSSION |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Flight speed values in our study agree with Petherick et al. (2003) who reported mean values of 2.3 m/s for 2- to 3-yr-old Bos indicus steers. No differences were observed in flight speed as a result of using a blind with or without administration of the injection in the present study. These findings are also consistent with those of Petherick et al. (2003) who reported flight speed was not affected by a moderately aversive treatment such as repeated blood sampling via venipuncture of the coccygeal vein. However, this is in contrast to results obtained from both the visual and electronic behavioral reactivity scores indicating that cattle exhibited some aversive behavior to the blind and the injection treatments. Similar findings have been observed in some recent studies looking at the relationship between flight speed and visual scores. In these studies greater visual scores during restraint did not necessarily mean a faster chute exit speed when assessing cattle temperament (K. S. Schwartzkopf-Genswein, unpublished data). However, our flight speed results are in contrast to Grandin (2003) who reported faster chute exit speeds were correlated with more struggling during restraint and slower exit velocities with less struggling. Similarly, Kilgour et al. (2006) reported a correlation of r = 0.44 (P < 0.05) between flight speed and visual scores during restraint for Angus calves. One reason for these discrepancies is that the studies by Grandin (2003) and Kilgour et al. (2006) were not designed to assess effects of aversive procedures during restraint as in our study. Previous work has suggested that increased flight speed upon exit from a squeeze chute can be used to predict fearfulness in beef cattle (Müller and von Keyserlingk, 2006).
The consistency of flight speed measures taken over the 2-d period in our study were similar to the findings of Müller and von Keyserlingk (2006), who reported a high individual within-day consistency of flight speed in beef cattle. Although flight speed in beef cattle appears to be an individually consistent measure over a short period of time, it appears to be an insensitive measure of minimally aversive experimental treatments.
Visual and Electronic Reactivity Scores
The visual reactivity scores obtained in the present study were similar to those of Red Angus cattle (mean behavioral reactivity score = 1.77 ± 0.07) assessed in a nonrestraining scale crate (Voisinet et al., 1997). However, they were less than those recorded by Müller and von Keyserlingk (2006) who reported a mean score of 2.62 for Aberdeen-Angus cattle of similar age but without the application of an aversive treatment such as the neck injection used in this study. Differences between studies may be attributed to several factors including different handling procedures and previous handling experience of the animals (Hemsworth, 2003). In addition, high interanimal variability in behavioral reactivity is common (Stookey et al., 1994) and is one reason why the use of within animal comparisons be made when testing for changes in reactivity over time or in relationship to specific treatments.
The electronic scores obtained in our study were similar to those reported by Mitchell et al. (2004; ranging from 0.80 to 3 V for maximum force) in British cross beef heifers used in a study to document the effect of a blindfold on reactivity to handlers. Mitchell et al. (2004) study only used the average force and the maximal force to access reactivity however; our study used several other relevant parameters calculated from the electronic system that may also be useful in assessing behavioral responses in restrained cattle. Because this was the first time some of these parameters have been used, no relevant literature comparisons could be made. All electronic parameters used in this study identified differences in animal reactivity between the pre-, test, and posttest intervals. However, of the same parameters used to assess within test interval differences, only the number of peaks above the baseline mean, the maximum force, total duration of force, and total duration of force above the mean identified treatment differences. This suggests that some of the parameters may be more useful and appropriate to assess the effects of minimally invasive treatment than others.
Visual reactivity scores indicated that cattle were more reactive when the blind (regardless of whether they received an injection or not) was used than when it was not in the pre- and posttreatment intervals but not during the treatment interval. This result is in contrast to the electronic reactivity scores in this study that indicated the cattle were as or more reactive when the blind was not in use during the treatment and post-treatment intervals where effects on behavior would most likely be seen. No treatment differences were observed in the pretreatment interval for electronic scores, which may be explained by the fact that a handler did not approach the animal in this interval. The visual score finding was also contrary to work done by Mitchell et al. (2004) who found that blindfolded animals were less responsive (had lower exertion forces on the chute and lower heart rates) than nonblindfolded controls when they were approached and touched on the neck. The electronic reactivity scores indicated that the presence of the blind did, as previously recommended by Grandin (1993a) and reported by Mitchell et al. (2004), mediate the negative behavioral reactions that can occur when visual and physical contact is made on the neck region.
The contrasting results obtained from the visual and electronic scores are most likely due in part to the fact that visual scoring methods may not be sensitive enough to identify treatment differences when minimally invasive treatments, like the use of a blind or injection, are applied. These findings are supported by an earlier study assessing beef cattle responses to different branding techniques. Schwartzkopf-Genswein et al. (1997) found that by using visual observations (100 animals/treatment) they could not differentiate responses of cattle to freeze and sham branding; however, using electronic measures, they could detect differences in the responses to the same treatments. In addition, it is possible that a 20-s interval may be too short a period to accurately visually assess an animal’s response to a procedure. Although Mitchell et al. (2004) did not use visual scores, they came to the same conclusions, using a similar scoring method to the one used in this study, regarding the effect of a blindfold.
Visual scores also showed that actual injection, regardless of blind use, resulted in more movement, suggesting it was more aversive than the sham procedure. Again, these results were in contrast to the electronic scores where no differences were found between the injection/sham injection treatments. The discrepancies between visual and electronic reactivity scores are difficult to explain particularly in light of the fact that electronic scores have been shown to be more sensitive than visual scores (Schwartzkopf-Genswein et al., 1997). One reason for these discrepancies, as stated previously, may be that the treatments were minimally invasive and therefore animal responses are minor and more difficult to access accurately using the visual method. Both scoring methods were sensitive to changes in animal reactivity across the pretreatment, treatment, and posttreatment intervals. Results of the electronic scores suggest that the animals reacted to the injection treatments (sham and actual) from the time of their application until at least 40 s after injection. In addition, as predicted the pretreatment interval was always characterized by the lowest score as no handler was in the vicinity of the animal’s neck during this period. These results are also different from those obtained using visual reactivity scores as pretreatment and posttreatment intervals were not different from the treatment interval, suggesting that the visual scores be interpreted carefully when assessing the effects of minimally invasive treatment.
Our study revealed that under the conditions described in this experiment the subcutaneous neck injection was not consistently aversive in comparison to a sham injection procedure depending on the assessment method used. Electronic scores indicated that the blind led to a reduction in the animal’s reaction to a handler regardless of whether a needle was inserted into the animal during the injection procedure. This reduced level of agitation may be explained by the loss of the visual field such that the handler administering the injection was not invisible to the animal during the approach or during the injection itself. Similar findings have been reported by many other researchers looking at the effect of a blindfold on cattle (Mitchell et al. 2004), elk (Thierman et al., 1999), and white-tailed deer (Haigh and Friesen, 1995). However, to our knowledge this is the first study to assess effects of a blind on reducing handler aversion during a routine management procedure.
The bovine eye has a streak of high cell density extending along a straight horizontal line in the retina (Hebel, 1976) running in parallel to the pupillary cleft. This morphology has been suggested to improve the horizontal view in cattle (Rehkämper et al., 2000). This highly developed lateral visual field is also evident in other prey species and allows them to flee for protection (Rehkämper and Görlach, 1997). Therefore, blocking this visual field with a blind or blindfold results in a calming effect because the cattle cannot see handlers approaching them or other visual cues that have been reported to cause fear in cattle such as bright lights, shadows, or novel objects (Grandin, 1993c).
In summary, use of a blind may help improve handling ease particularly with cattle having to undergo repeated aversive procedures and in cattle having little previous experience with humans. This is not surprising considering the evolution of cattle as a species in which use of visual cue is vital in launching appropriate escape responses to perceived and or real aversive or dangerous situations. A blind may have more practical application than a blindfold for use in reducing aversion in cattle to handling as it requires no further potentially dangerous and time consuming handling of the animals and is easy and inexpensive to install.
|
Footnotes |
|---|
2 Corresponding author: gensweink{at}agr.gc.ca
Received for publication July 24, 2007. Accepted for publication January 30, 2008.
|
LITERATURE CITED |
|---|
|
TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
