ELECTRO-IMMOBILIZATION VERSUS MECHANICAL RESTRAINT IN AN AVOID-AVOID CHOICE TEST FOR EWES

Journal of Animal Science (1986) volume 62: 1469-1480

Temple Grandin1, Stanley E. Curtis1,
Tina M. Widowskii1 and John C. Thurmon2,3,4

University of Illinois
Urbana 61801

ABSTRACT

A Y-maze avoid-avoid choice test was used to elucidate pregnant ewes' relative preference for electro-immobilization as opposed to restraint by a squeeze-tilt table. Choices in successive trials evaluating three commercial electro-immobilizers were: electro-immobilizer-13, 13 and 8% for respective models; squeeze-rift table-79, 57 and 71%; and no choice-8, 30 and 21%. In all trials combined, 56% of the ewes never chose the electro-immobilizer after once experiencing it, while 94% did choose the squeeze-tilt table one or more tunes after being restrained by it. Most ewes became more willing to enter the table as experience with it increased, but those that had been both electro-immobilized and table-restrained became more hesitant to pass the test facility' s entrance gate as these experiences increased. Ewes accepted a feed reward only reluctantly if at all after being electro-immobilized, but readily after table restraint. Electro-immobilization was clearly more aversive to the ewes than was restraint by a squeeze/tilt table. When restraint by either electro-immobilization or squeeze/tilt table is necessary, use of the table would be indicated in terms of its being less aversive.

(Key Words: Immobilization, Restraint, Handling, Sheep, Behavior.)

1 Anim. Sci. Dept., 126 Anim. Sci. Lab., 1207 Gregory Dr., Urbana, IL 61801.
2 Vet. Clin. Med. Dept.
3 The authors gratefully acknowledge the assistance of Knut Boe, Karen Charhut, Richard Cobb, Iain Curtis, Rhonda Feinmehl, Robert Hurst, James McFarlane, Balaam Mujuni, Mary Rowland, Andreas Siegerink and Sharon Zaccone.
4 Supported by a grant from Humane Information Services, Inc., St. Petersburg FL.
Received June 10, 1985.
Accepted January8, 1986.


Introduction

Livestock traditionally have been restrained by squeeze chutes and tilt tables so a variety of procedures can be performed on them. More recently, electro-immobilizers have been designed to restrain sheep and cattle for shearing and other husbandry proce dures. A small electrical current is passed through an animal's body, causing the skeletal muscles to contract. For example, one commerical model uses 55 V DC maximum at 20 to 240 mA with a 1-ms pulse repeated 50 times/e (Carter et al., 1983; Crouse and S mith, 1984). The humaneness of electro-immobilization has been questioned (Carter et al., 1983; Lambooy, 1985; Pascoe and McDonell, 1985). To determine which was less aversivečrestraint by one of three commercial electro-immobilizers or by a squeeze-tilt tablečadult ewes were given the choice between the two in a Y-maze avoid-avoid situation on the way to a feed reward, and their behavior was studied.

Materials and Methods

Animals. Forty-five pregnant Suffolk ewes aged 1 to 9 yr and in good physical condition were maintained on bluegrass pasture (free choice) and shelled corn (.9 kg/d) for several months before experimentation. The ewes had no previous experience with an electro-immobilizer, squeeze chute or tilt table.

Adjustment. In each of three trials, 12 naive experimental ewes selected at random from the University flock and three flock mate decoys were kept in a holding area (figure 1) for a 2-d adjustment period before training. The crowd gate was tied open to g ive the ewes access to the crowd-pen space. Holding area and crowd pen were bedded with wheat straw. The ewes already had access to good alfalfa hay and water. Feed rewards enhance movement of sheep through handling facilities (Hutson, 1985), so the ewes were offered a mixture of cracked corn, whole oats, linseed pellets and wheat bran in a human's hand twice daily during the adjustmnet period.

Test Facility. The ewes were trained and tested in a windowless, 10.4 X 9.1 meter concrete floored room illuminated by incandescent lamps. The test facility (figure 1) was constructed from portable fence panels, guillotine and swing gates and chute supports5, all painted brown.

5 Livestock Systems Inc., Sidney, NE.

Figure 1.

Plan of a sheep handling facility for choice tests. Hexagons = locations of experimenters on day 2 (testing day; all nine positions were occupied):

On day 1 (training day) only four experimenters were present; one person worked at positions 2 and 3, and positions 1, 4, 5, and 7 were not occupied.

Ewes were admitted to the Y decision point one at a time through the plywood-covered guillotine start gate. Beyond the decision point, the right alley of the Y led to the electro-immobilizer station, the left to the squeeze-tilt table station. To help the ewes discriminate between alleys, six 4- x 40-cm yellow tape strips 3 cm apart (vertical on the electro-immobilizer side, horizontal on the other) were placed just past the Y's fork on panels on both sides of both alleys.

The single-file chute leading to the start gate was 38 cm wide with solid sides. The decision point of the Y was 61 cm wide with solid sides, enabling a ewe to turn around easily and switch among the Y's start leg and two alleys while making a decision. Both electro-immobilizer and squeeze-tilt table stations had guillotine gates at both ends. These gates were constructed of bars so an approaching ewe could see the decoys. Both electro-immobilizer and squeeze-tilt table stations were 33 cm wide and 1.2 m long in the open position.

To induce a ewe to move through the test facility, 100 g of the feed mixture already described was offered on the floor in the feed-reward pen. The ewe was allowed to ingest the feed and to leave the pen via the open exit at her will. In addition, 150-W flood lamps 1.8 m above the floor were installed over entrance gate, start gate and back gates at both electro-immobilizer and table stations. The lamps were aimed to illuminate the floor and not to shine into an approaching ewe's eyes (Grandin, 1983).

Restraint Methods. Ewes were restrained by one of three commercial electro-immobilizers6 in successive trials. Model A was used in Trial 1, B in 11 and C in 111. A spring-clamp electrode was attached to the ewe's upper-lip mucous membrane, and a needle electrode was inserted under rump skin 5 cm from the spine and spring-clamped to wool. The electro-immobilizer used in Trial I operated at 100 Hz (Amend, 1983), while that in Trial 11 was at 50 Hz (Carter et al., 1983); the model used in Trial 111 was operated at the preset, but unknown, pulse frequency. The devices were set at "low-range 40", "200 mA" and "low-range 10", respectively, and electro-immobilization--as judged by a marked and continuous rigor-like stiffening and often a toppling of the entire body--was imposed for 5 s.

6 Model A--Vet-Master 303051, AgTronic Int., Inc., Hastings, NE; Model B--Stockstill Mark 1, Feenix Int. Pty. Ltd., Tarlee, S. Australia; Model C--Little Seize'er, L-8 Products, San Diego, CA.

Mechanical restraint was accomplished by a sheep squeeze-tilt table5. The unit had one moveable side panel, hinged at the bottom, to squeeze the ewe against the stationary solid side, which formed the table when the operator tilted the unit manually. Each mechanically restrained ewe was held for 15 s in the table while positioned horizontally.

Training: Day 1

Training took place on one day, day 1. Decoy ewes were placed in the decoy pen and offered alfalfa hay (free-choice). Then the experimental ewes were trained in the choice test procedure. They were handled gently while being trained to enter the Y when t he start gate was opened. Once they did so voluntarily, the ewes were directed to 10 training passes through the test facility, as follows

Training Passes 1 and 3. Directional gate installed in Y to direct all ewes through squeeze tilt table. All guillotine gates open. All ewes allowed to move through facility as group. No restraint applied.

Training Passes 2 and 4. Same as 1, except all ewes directed through electro-immobilizer station.

Training Passes 5 and 7. Each ewe admitted to Y one at a time via start gate. Directional gate directed all ewes to table. When ewe entered, she was locked in table station for 15 s by front and back gates. No restraint applied.

Training Passes 6 and 8. Same as 5, except all ewes directed to electro-immobilizer station, in which they were locked for 15 s.

Training Passes 9 and 10. Directional gate removed. Each ewe admitted to Y one at a time via start gate. Then each ewe locked in station of her choice for 15 s. No restraint applied.

Each ewe passed through the feed-reward pen as she returned to holding area through the open exit after she left either station. Ewes waited to enter the test facility in either the crowd pen or the single-file chute (three or four at a time).

Testing: Day 2

Testing took place on one day, day 2, the day after training. Procedures for rewarding the ewe and returning her to the holding area after being released from her chosen station were as on the training day, day 1.

Pre-Choice Passes 1 and 2. Ewes admitted to Y one at a time via start gate. Directional gate not in place. Ewe locked in station of her choice for 15 s. No restraint applied.

Treatment Pass. Ewes admitted to Y one at a time via start gate. Each ewe had been assigned at random to one of two groups-- one-half directed by directional gate to electro-immobilizer station, the other one-half to table station. Each ewe locked in station to which she had been directed, and electro-immobilization or table, as appropriate, operated immediately. (Served to ensure that onehalf of the ewes experienced the electro-immobilizer first, one-half restraint by the table).

Choice Passes 1 through 4. Directional gate not in place. Each ewe allowed to make choice. Electro-immobilizer or table, as appropriate, operated. If ewe refused to enter one station or other within 5 min, she was registered as making no choice and relea sed by opening center section of Y (figure 1).

Choice Pass 5. Same as Choice Pass 1, except after ewe expressed choice, electro-immobilizer or squeeze-tilt table not operated.

Data Registered and Statistical Analysis. During each choice pass, data registered7 were entrance time (time at start gate), number of times and time in table alley of Y, number of times and time in electro-immobilizer alley of Y, decision time (time from start gate open until choice made; maximum 5 min), choice made and quality of acceptance of feed reward (refused, took one bite or took more than one bite). Statistical significance of differences between or among choice-pass choices, frequencies of vac illations, frequencies of hesitations and feed-reward acceptance scores was determined using the Yates-corrected chi-square test (Lehner, 1979). Decision time was subjected to multiple regression analysis accounting for trial, animal and choice-pass number (SAS, 1982).

7 Datamyte 800, Electro General Corp., Minnetonka, MN.

Results

The ewes expressed clear preference for being restrained by the squeeze-tilt table as opposed to any of the electro-immobilizers tested (tables 1, 2 and 3). Choices were tabulated and analyzed only for choice passes coming after a ewe had experienced restraint by both electro-immobilizer and squeeze-tilt table.

In Trial I (table 1), the 12 ewes made 47 choice passes after all had experienced both electro-immobilizer and squeeze-tilt table. Of these, six (13%) resulted in electro-immobilizer choices, 37 (79%) table choices and four (8%) no choices (P<.001). Six e wes never chose the electro-immobilizer after experiencing it once, while all ewes chose the squeeze-tilt table at least twice after experiencing it once.

Table 1. Ewes' Choices on Testing Day (Trial I) a




Choice during choice pass After experiencing both I and S
Ewe Pre-choice pass 1 Pre-choice pass 2 Treatment imposed during treatment pass 1 2 3 4 5 No. choice passes No. 1 choices No. S choices No. no choices
78-20 S I S S I S I S 3 1 2 0
77-32 S I I S S S S S 4 0 4 0
79-18 S I S I S S S S 4 0 4 0
81-13 I I I S S NC I S 4 1 2 1
80-37 I I S I I S S S 4 1 3 0
82-60 I I S I I S S S 4 1 3 0
81-36 I I I S S S S S 4 0 4 0
82-55 I I S I S I S S 4 1 3 0
83-48 I I I S S S I NC 4 1 2 1
79-26 I I I S S S NC NC 4 0 2 2
556 S S I S S S S S 4 0 4 0
83-38 S I S I S S S S 4 0 4 0
Totalsb







47 6 37 4
a I = electo-immobilizer; S = squeeze-tilt table; NC = no choice within 5 minutes.
b Frequencies of I and S choices differed (P<.001)

In Trial 11 (table 2), the 12 ewes made 46 choice passes after all had been restrained by both devices six (13%) resulted in electro-immobilizer choices, 26 (57%) table choices and 14 (30%) no choices (P<.001). Six ewes never chose the electro-immobilizer after once experiencing it, and likewise two never chose the table again.

Table 2. Ewes' Choices on Testing Day (Trial II) a




Choice during choice pass After experiencing both I and S
Ewe Pre-choice pass 1 Pre-choice pass 2 Treatment imposed during treatment pass 1 2 3 4 5 No. choice passes No. 1 choices No. S choices No. no choices
80-85 S S I S S S S S 4 0 4 0
80-17 I I S I S I S NC 4 1 2 1
83-47 S I S I S S S I 4 1 3 0
81-26 S S I S S NC NC NC 4 0 1 3
82-74 S I S S I NC S S 3 0 2 1
80-20 S S I S I NC S NC 4 1 1 2
81-25 I I S NC I NC NC NC 3 0 0 3
82-3 S I I S S NC S S 4 0 3 1
78-62 I I S I S S S I 4 1 3 0
80-91 S S I S S S S S 4 0 4 0
82-5 I I S I I I NC NC 4 2 0 2
75-17 S S I S S S S NC 4 0 3 1
Totalsb







46 6 26 14
a I = electo-immobilizer; S = squeeze-tilt table; NC = no choice within 5 minutes.
b Frequencies of I and S choices differed (P<.001)

In Trial III (table 3), two ewes directed to the table in the treatment pass never chose and thus never experienced the electro-immobilizer. The other 10 of the 12 ewes engaged in 38 choice tests after they had experienced both electro-immobilization and table restraint. In the 38 passes, three (8%) resulted in electro-immobilizer choices, 27 (71%) table choices and eight (21%) no choices (P<.001). Seven of the ten ewes that experienced the electro-immobilizer never chose it again, while all ewes chose the table at least once more after having been restrained by it.

Table 3. Ewes' Choices on Testing Day (Trial III) a




Choice during choice pass After experiencing both I and S
Ewe Pre-choice pass 1 Pre-choice pass 2 Treatment imposed during treatment pass 1 2 3 4 5 No. choice passes No. 1 choices No. S choices No. no choices
78-67 I I S I I S S NC 4 1 2 1
78-37 S S I S S S S S 4 0 4 0
79-19 S S I S NC S S S 4 0 3 1
81-66 I I S I S I S S 4 1 3 0
83-12 I I S I S I NC NC 4 1 1 2
82-76 S I I S S S S S 4 0 4 0
83-16 S S S S S S S S NA NA NA NA
83-31 I I I I S S S S 3 0 3 0
81-43 I I I S NC NC S NC 4 0 1 3
82-31 I I I I S NC S S 3 0 2 1
83-5 I I S I S S S S 4 0 4 0
82-16 S S S S S S S S NA NA NA NA
Totalsb







38 3 27 8
a I = electo-immobilizer; S = squeeze-tilt table; NC = no choice within 5 minutes; NA = not applicable (did not experience both restraint methods).
b Frequencies of I and S choices differed (P<.001)

Sixteen of the 36 experimental ewes in the three trials made no choice on one or more choice passes. Six of these spent more time in the Y's table alley (table 4), while 10 displayed no preference for either alley; most of them never passed the start gate. No ewe favored the electro-immobilizer alley during a no-choice pass (P<.01).

Table 4. Ewes' Activities During Choice Passes In Which They Made No Choice On Testing Day



Stem of Y Electro-immobilizer alley of Y Sqeeze-tilt table alley of Y
Ewe Choice Pass Time waiting at starting gate, min. No. of entries Time, min. No. of entries Time, min. No. of entries Time, min.
Trial I
81-13 3 .10 2 .07 0 0 2 4.83
79-26 4 .06 1 .02 8 1.46 8 3.46
79-26 5 .07 2 .11 12 1.33 13 3.49
83-48 5 .83 2 4.03 0 0 1 .14
Trial II
81-25 1 5.00 0 0 0 0 0 0
81-25 3 5.00 0 0 0 0 0 0
81-25 4 5.00 0 0 0 0 0 0
81-25 5 5.00 0 0 0 0 0 0
81-26 3 .05 2 4.78 1 .03 2 .14
81-26 4 5.00 0 0 0 0 0 0
81-26 5 0 2 2.52 5 .76 4 1.76
82-74 3 5.00 0 0 0 0 0 0
80-20 3 4.93 1 .07 0 0 0 0
80-20 5 5.00 0 0 0 0 0 0
82-3 3 5.00 0 0 0 0 0 0
82-5 4 5.00 0 0 0 0 0 0
82-5 5 5.00 0 0 0 0 0 0
75-17 5 0 2 .09 2 .18 1 4.73
80-17 5 5.00 0 0 0 0 0 0
Trial III
79-19 2 4.40 2 .60 0 0 0 0
81-43 2 4.13 2 .12 0 0 1 .75
81-43 3 .08 2 .81 1 .25 2 3.96
81-43 5 5.00 0 0 0 0 0 0
83-12 4 .03 4 3.93 1 .11 4 1.04
83-12 5 5.00 0 0 0 0 0 0
78-67 5 5.00 0 0 0 0 0 0
82-31 3 4.86 1 .14 0 0 0 0

There was no significant difference among trials for electro-immobilizer and table choices, but Trial II had the most no choices (P<.05). Perhaps the ewes became more hesitant to enter the Y after having been restrained by the particular electro-immobili zer used in Trial II, but because electro-immobilizer models were confounded with trials, no conclusion as to model differences would be valid.

Ewes vacillated more often while deciding to enter the electro-immobilizer station than while choosing the squeeze-tilt table (table 5). If choice-pass entrance time was longer than three standard deviations beyond the mean of the prechoice entrance time for respective trials, it was registered that the ewe had "hesitated". There was a higher incidence of hesitation during choice passes in w hich ewes ultimately chose to subject themselves to electro-immobilization (table 5).

Table 5. Vacillation And Hesitation In Ewes Which Made Choices After Experiencing Both Electro-Immobilization And Squeeze-Tilt Table Restraint On Testing Day

No. of electro-immobilizer choices No. of squeeze-tilt choices
Trial Total With Vacillation With Hesitation Total With Vacillation With Hesitation
I 6 4 (67%) 4 (67%) 37 10 (27%)d 9 (24%)c
II 6 4 (67%) 3 (50%) 26 3 (12%)b 9 (35%)
III 3 2 (67%) 2 (67%) 27 3 (11%)c 5 (19%)d
All Trials 15 10 (67%) 9 (60%) 90 16 (18%)a 23 (26%)b
a Lower frequency of vacillation or hesitation than in passes resulting in electro-immobilizer choices (P<.001).
b Lower frequency of vacillation or hesitation than in passes resulting in electro-immobilizer choices (P<.01).
c Lower frequency of vacillation or hesitation than in passes resulting in electro-immobilizer choices (P<.05).
d Lower frequency of vacillation or hesitation than in passes resulting in electro-immobilizer choices (P<.10).

All ewes in trials ate the feed reward after passing through the facility in the pre-choice passes. All ewes also ate the feed reward after their first experience in the squeeze-tilt table, while electro-immobilization reduced feed reward acceptance (table 6).

Table 6. Nature Of Ewes' Acceptance Of Feed Reward At End Of Treatment Pass On Testing Day


No. of ewes
Trial Treatment during treatment pass Refused reward Took one bite Took more than one bite Probability that difference between treatment groups was due to chance
I Electro-immobilizer
Squeeze-tilt table
1
0
2
0
3
6
>.10
II Electro-immobilizer
Squeeze-tilt table
2
0
2
0
2
6
<.05
III Electro-immobilizer
Squeeze-tilt table
3
0
0
0
3
6
>.10
All trials Electro-immobilizer
Squeeze-tilt table
6
0
4
0
8
18
<.001

Total time that ewes took to make a decision is summarized in table 7. There was a tendency for ewes either to make a quick decision (within 15 s) or to take longer than 1 min to make a choice. Decision time increased (P<.001) after the ewes had experien ced restraint by electro-immobilizer, squeeze-tilt table or both (table 7). Results of multiple regression analysis indicated that, in all trials combined, decision time was .37 min longer (P<.001) in each successive choice pass.

Table 7. Total Time (Min.) Before Ewes Arrived At Electro-Immobilization Or Squeeze-Tilt Table Station (Decision Time) In Respective Passes On Testing Day




Choice pass
Trial Pre-choice
pass 1
Pre-choice
pass 2
Treatment
pass
1 2 3 4 5
I .12 - .01a .10 - .02 .13 - .04 .22 - .12 .56 - .30 .72 - .47 .91 - .44 1.79 - .58
II .08 - .004 .08 - .004 .09 - .01 .82 - .50 .49 - .37 2.33 - .71 2.46 - .56 3.27 - .81
III .07 - .004 .07 - .004 .20 - .10 .16 - .09 1.08 - .57 1.23 - .57 .65 - .43 1.33 - .64
All trials .09 - .006 .08 - .007 .14 - .04 .40 - .17 .71 - .24 1.45 - .35 1.34 - .30 1.91b - .37
a Mean - SE.
b Ewes tended to take progressively longer time to arrive at station after gate was opened (decision time) in successive choice passes (P<.001).

Discussion

In an earlier study, sheep learned to turn right or left in a maze to find a feed reward (Liddell, 1954). Also, calves learned to discriminate between black and white pails (Wieckert et al., 1966) and between different shapes (Baldwin, 1981).

Y- and T-mazes, as means of testing animals' preferences, have been used to study aspects of both physical and social environments in several species, e.g., flooring and social preferences in chickens (Hughes, 1976; Dawkins, 1982) and mating preferences in pigs (Signoret, 1976). The Ymaze also has been used to determine handling facility preferences. Sheep preferred a level chute floor as opposed to a ramp (Hitchcock and Hutson, 1979), and chute-floor battens laid crosswise as opposed to lengthwise (Huts on, 1981).

The present two-choice preference test was of the avoid-avoid type, in which both choice alternatives facing the animal are more or less aversive.

Previous experience can affect an animals' expressed preferences. Experience with different pastures led to different grazing preferences in sheep (Arnold and Maller, 1977). Rearing environment affected subsequent flooring and social preferences in caged hens (Hughes, 1976). To help ensure that the ewes in our trials made unbiased choices, we used ewes that had had no previous experience with electro-immobilizers, squeeze chutes or tilt tables.

Pre-Choice Passes. During the pre-choice passes on the testing day, day 2, all ewes willingly passed the entrance gate and entered the single-file chute leading to the start gate. As choice passes progressed and the ewes experienced restraint by both electro-immobilization and squeeze-tilt table, they became less willing to pass the entrance gate. Some ewes in Trials I and 11 had to be caught and pushed through the gate. Hutson (1984) found sheep reluctant to re-enter a device in which they had been held upside down. Cows that had been electro-immobilized were more reluctant to reenter a set of stocks and had higher heart rates than did control animals or cows which had received an injection of saline solution (Pascoe and McDonell, 1985), and those authors concluded that electro-immobilization was painful.

During pre-choice passes, ewes tended to prefer the electro-immobilization station; perhaps its physical arrangement made it easier to walk through (figure 1). During pre-choice pass 2, no ewe switched from electro-immobilizer station to table station, but eight switched vice versa. Thus, the ewes' marked preference for the squeeze-tilt table station during choice passes was not associated with a pre-choice pass preference for it due to laterality or some other factor.

Choice Passes. Both squeeze-tilt table and electro-immobilizers were aversive to ewes during choice passes. The possibility that the electro-immobilizers' electrodes themselves were aversive, either in addition to or even instead of the electrical current itself, was not evaluated; the units were simply operated as they would have been in commercial practice. Ewes moved through the Y-maze with little or no hesitation in pre-choice passes, but a few refused to make another choice after experiencing restraint in both stations. Rats were reluctant to leave the starting compartment and enter the passageway where they had been shocked (Hoge and Stocking, 1912; Lashley, 1912).

Ewes hesitated and vacillated between the Y's two alleys more during choice passes in which they ultimately chose to subject themselves to electro-immobilization than while choosing the squeeze-tilt table. Perhaps they were attempting to avoid the electro-immobilizer, but could not remember which side it was on. Vacillation ("vicarious trial and error") occurs when an animal is unsure or learning to discriminate (Muenzinger, 1938; Goss and Wischner, 1956). It tends to occur frequently in avoid-avoid situations, when animals must choose between unpleasant alternatives (Brown, 1942; Miller, 1944; Goss and Wischner, 1956).

Electro-immobilizers. The ewes' reactions differed after the three respective electro-immobilizers were turned off. Because each individual experienced only one electro-immobilizer, comparison among types would not be valid. Nevertheless, in Trial 11, when model B was used, the rear quarters of some ewes remained partially collapsed for as long as 10 s after the electro-immobilizer had been turned off; in this trial, a ewe typically squatted as she exited the electro-immobilizer station, and several seconds were required for her to stand normally. Also, electro-immobilized ewes were more agitated after the device was turned off in Trial I (Model A) than in Trial 11 (Model B).

We used relatively high electro-immobilizer settings in these trials to ensure that the ewes would be immobilized instantly and on the first attempt (but, in contrast to much longer periods in practice, for only 5 s). Operator manuals generally recommend that a high setting be used for initial electro-immobilization, and then that a lower setting be employed to allow breathing to restart while maintaining electro-immobilization. Conversely, when the setting is low at first and then raised, the device sometimes stimulates the animal. A setting of 200 mA or greater has been recommended for initial electro-immobilization of cattle (Anonymous, 1980). Lambooy and van Voorst (1983) found that the setting required to maintain electro-immobilization of ewes with Model B (Trial 11) ranged from 60 to 140 mA. The 200-mA setting was chosen for this model in our study. For electro-immobilizing sheep, Amend (1983) recommended using the low range on Model A (Trial 1). "Low-range 40"č 40% of maximum intensity on the low-range dial--reliably electro-immobilized our sheep. Manufacturer's instructions with Model C (Trial 111) did not include specific recommendations as to setting. This device has both high and low ranges, and the maximum low-range setting worked reliably in our hands and was used in this work.

Alleged Analgesic Effect. It has been alleged that electro-immobilization has an analgesic effect on the animal in addition to restraining it. If so, procedures performed under electro-immobilization would be less painful than when performed under other k inds of restraint. This possibility was not tested in this experiment. However, the ewes' reactions to electro-immobilization in the present experiment indicate that it is unlikely that the aversiveness of even painful experiences under squeeze tilt table restraint would exceed that of electro-immobilization alone. Little evidence for analgesia was found in a recent study; electro-immobilized calves, sheep and pigs still had a positive corneal reflex, and one-half reacted to painful stimuli (Lambooy, 1985).

Conclusion

Ewes clearly found electro-immobilization aversive. (1) They preferred to be restrained by the squeeze-tilt table rather than by any of the three electro-immobilizers used. (2) Electro-immobilization reduced the ewes' acceptance of a feed reward after being restrained. (3) Ewes that had been restrained by both electro-immobilizer and squeeze-tilt table became progressively more hesitant to enter the test facility as the number of such experiences increased. (4) In the avoidavoid choice situation, ewes that ultimately chose the electro-immobilizer vacillated and hesitated more while making that choice than did those in the process of choosing to be restrained by the squeeze-tilt table.

The results suggest the need for further studies of electro-immobilization with regard to its humaneness. When animal restraint by either electro-immobilization or squeeze-tilt table is necessary, use of the table would be indicated in terms of its being much less aversive to the animals.

Literature Cited

Amend, J. F. (1983)
Preliminary verdict for electro-immobilization
Int. Journal Stud. Anim. Prob. 4:11

Anonymous (1980)

Feenix Stockstill Mark 1 Operator's Manual
Feenix International Pty., Ltd., / Tarlee, S. Australia

Arnold, G. W. and R. A. Maller (1977)

Effects of nutritional experience in early and adult life on the performance and dietary habits of sheep
Applied Animal Ethology 3:5

Baldwin, B. A. (1981)

Shape discrimination in sheep and calves
Animal Behaviour 29:830

Brown, J. S. (1942)

Factors determining conflict reactions in difficult discriminations
Journal of Experimental Psychology 31:272

Carter, P. D., N. E. Johnston, L. A. Corner and R. G. Jarrett (1983)

Observations on the effect of electro-immobilization on the dehorning of cattle
Australian Veterinary Journal 60:17

Crouse, J. D. and S. B. Smith (1984)

The effects of electrically induced live-animal muscle contraction on bovine muscle glycogen
pp 19 - 21. / Proc. 30th Eur. Meet. Meat Res. Workers, Bristol

Dawkins, M. S. (1982)

Elusive concept of preferred group size in domestic hens
Applied Animal Etholology 8:365

Goss, A. E. and G. J. Wischner (1956)

Vicarious trial and error and related behavior
Psychology Bull. 53:335

Grandin, T. (1983)

Welfare requirements of handling facilities
In: S. H. Baxter, M. H. Baxter and J.A.D. MacCormack (Ed.)
Farm Animal Housing and Welfare (pp 137-149)
Martinus Nijhoff ,Publishers, Boston, MA.

Hitchcock, D. K. and G. D. Hutson (1979)

The movement of sheep on inclines
Australian Journal of Experimental Agricultural Animal Husbandry 19:176

Hoge, M. A. and R. A. Stocking (1912)

A note on the relative value of punishment and reward motives
Journal of Animal Behaviour 2:43

Hughes, B. O. (1976)

Preference decisions of domestic hens for wire or litter floors
Applied Animal Etholology 2:155

Hutson, G. D. (1981)

Sheep movement on slatted floors
Australian Journal Experimental Agricultural Animal Husbandry 21:474

Hutson, G. D. (1985)

The influence of barley food rewards on sheep movement through a handling system
Applied Animal Ethology 14:263

Lambooy, E. (1985)

Electroanesthesia or electro-immobilisation of calves, sheep and pigs with the Feenix Stockstill
Veterinary Quarterly 7: 120

Lambooy, E. and N. van Voorst (1983)

Electroanesthesia of calves and sheep
In: G. Eikelenboom (Ed.) Stunning of Animals for Slaughter (pp 117-122)
Martinus Nijhoff Publishers, Boston, MA.

Lashley, K. S. (1912)

Visual discrimination of size and form in the albino rat
Journal of Animal Behaviour 2:310

Lehner, P. N. (1979)

Handbook of Ethological Methods
Garland STPM Press, New York

Liddell, H. S. (1954)

Conditioning and emotions
Scientific America 190:48

Miller, N. E. (1944)

Experimental studies of conflict
In: J. McV. Hunt (Ed.) Personality and the Behavior Disorders( pp 431-465)
The Ronald Press Co., New York

Muenzinger, K. F. (1938)

Vicarious trial and error at the point of choice: a general survey of its relation to learning efficiency
Journal of General Psychology 53:75

Pascoe, P. J. and W. N. McDonell (1985)

Aversive conditioning used to test the humaneness of a commercial electro-immobilization unit in cattle
Veterinary Surg. 14:75 (Abstr.)

SAS (1982)

SAS User's Guide: Statistics
Statistical Analysis System Institute, Inc., Cary, NC.

Signoret, J. P. (1976)

Chemical communication and reproduction in domestic animals
In: R. L. Doty (Ed.) Mammalian Olfaction, Reproductive Processes and Behavior (pp 243-256)
Academic Press, New York

Wieckert, D. A., L. P. Johnson, K. P. Offord and G. R. Barr (1966)

Measuring learning ability in dairy calves
Journal of Dairy Science 49:729


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