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No effect of variation in handling on behaviour in a
porcine elevated plus-maze — a brief report
Andrew M. Janczak
a,), Lene J. Pedersen
b, Karin H. Jensen
b,
Inger Lise Andersen
c, Knut Egil Bøe
c, Morten Bakken
a aDepartment of Animal Science, Agricultural UniÕersity of Norway, P.O. BOX 5025, N-1432 Aas, Norway
b
Department of Animal Health and Welfare, Danish Institute of Agricultural Science, P.O. BOX 50, D-8830 Tjele, Denmark
c
Department of Agricultural Engineering, Agricultural UniÕersity of Norway, P.O. BOX 5065,
N-1432 Aas, Norway
Accepted 31 January 2000
Abstract
The elevated plus-maze is a widely used model of anxiety in rodents and has recently been suggested as a putative model of anxiety or fear in swine. The aim of the present experiment was to examine the effects of a pretest blood sampling procedure on the behaviour of weaned pigs in an elevated plus-maze. Animals in the control group were lifted one-by-one into a transport trolley and moved to the test apparatus, where they were observed for a 5-min period. The treatment group differed from the control group in that these animals were immobilized with a nose snare and a blood sample was extracted from the jugular vein prior to transport to the test room. Behaviour in the porcine elevated plus-maze did not differ significantly between the two handling procedures.q2000 Published by Elsevier Science B.V. All rights reserved.
Keywords: Pig — fearful behaviour; Fear; Anxiety; Human–animal relationship; Elevated plus-maze; Blood
sampling
1. Introduction
The elevated plus-maze is widely used and well validated as a model of anxiety in
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rodents Lister, 1987; File, 1992; Rodgers and Cole, 1993; Cruz et al., 1994; Pellow et
)Corresponding author. Tel.:q47-649-48000; fax:q47-649-47960.
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E-mail address: [email protected] A.M. Janczak .
0168-1591r00r$ - see front matterq2000 Published by Elsevier Science B.V. All rights reserved. Ž .
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al., 1995; Hogg, 1996 . The apparatus is composed of four elevated arms of equal size radiating from a central platform. Exterior walls enclose two opposite arms, while the other two are open. Animals are free to enter all arms from the central platform, but avoid open arms. Avoidance of open arms is measured as the number of open entries
ŽOE and amount of time OT spent on open arms. OE and OT are the primary. Ž .
measures of anxiety in rodents. Our research group recently showed that pigs also avoid open arms and that avoidance is reduced by treatment with the anxiolytic drug
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Diazepam Andersen et al., 2000 . These findings indicate that OE and OT may be related to anxiety or fear in swine, a possibility that should be investigated by further studies. However, to better understand the model, it is also important to know which methodological factors lead to variation in behaviour. For rats, repeated gentle handling prior to testing leads to reduced avoidance of open arms in the elevated plus-maze, while more acute stress in the form of injections with saline prior to testing increases
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avoidance Adamec et al., 1991; Schmitt and Hiemke, 1998 . The aim of the present experiment was therefore to illuminate whether a blood sampling procedure prior to testing would affect behaviour in a porcine elevated plus-maze as suggested by the above findings in rats.
2. Materials and methods
2.1. Animals
The experiment was conducted using animals from the National Institute of Animal
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Science in Foulum, Denmark. The animals were 8-week-old female pigs Yorkshire=
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Danish Landrace . All animals were born in standard crates where they lived until weaning at the age of 28 days without access to food except milk from the sow. At weaning, animals were moved to weaning pens measuring 170=180 cm with 2r3 slatted floors. They lived in these cages in stable litter groups of F7 animals per cage throughout the period of testing. After weaning the piglets had ad libitum access to
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concentrated dry pig feed and water. Two animals from each of 10 litters 20 pigs in
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total were randomly assigned to either the control or treatment group and tested in the PEPM. Experienced technicians weighed the experimental pigs once each week from weaning until 8 weeks of age.
2.2. The porcine eleÕated plus-maze
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The PEPM was a modification of the apparatus described by Andersen et al. 2000 , adjusted to the size of pigs at 8 weeks of age. The apparatus was composed of two
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opposite, open arms without walls 160=80 cm and two closed arms with walls
Ž160=80=60 cm3.that radiated from a central platform 80Ž =80 cm2.to form a plus
to the plywood with transparent acrylic paint. The side and end walls of the enclosed arms were made of transparent 5-mm plexiglas, supported along all edges with 1=2-in. planks. The apparatus was set up in a test room measuring 4.4=5.6 m2. The test room was totally isolated, having concrete walls, iron sliding doors, and had no windows. The room was lit by neon lamps mounted on the ceiling.
2.3. Treatments
All testing was performed on 5 days over a 5-week period between 1400 and 1600 h with the 10 litters distributed over test days according to age. Pigs from the treatment group were removed singly from their home pen. Each test animal was lifted by two arms under its body and placed onto the floor outside the home cage. It was then led through a door to the hallway, the technician gripping the animal’s ear with one hand, the other hand placed behind its rump. Upon entering the hallway, a second technician fitted a nose snare on the animal. The nose snare circled over the test animal’s snout and
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passed through the mouth behind the incisor teeth . After this the technician took a blood sample from the jugular vein by vena puncture, while another technician held the animal firmly in the nose snare, effectively limiting its movement. From the time the technician entered the home pen until the needle was removed from the animal took
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55"33 s mean"s.d. . After taking the blood sample, the nose snare was immediately removed. The pigs were then lifted into a transport trolley and moved to the door outside of the test room before being placed into the center of the PEPM facing an open arm. The time from when the technician entered the home pen to catch the animal until it was placed onto the PEPM apparatus was always 5 min for the treatment group. After placing the animal onto the apparatus, the technician immediately exited the room and closed the door.
Animals in the control group were caught, transported and placed onto the test apparatus in the shortest possible time to minimize handling-related stress. Because of this attempt to minimize handling duration, the time from when the technician entered the home cage of animals in the control group until they were placed onto the maze was
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194"111 s mean"s.d. . Behaviour was filmed by a video camera mounted above the plus-maze apparatus and connected to a monitor and VCR in an adjacent observation
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room. Observations were made from film using a hand-held computer Psion
Work-.
about; Noldus Information Technology, 1997 and The Observer software package
ŽNoldus Information Technology, 1995 . Behaviour was observed for a period of 5 min.
from the time that the laboratory technician removed her hands from the pig after placing it into the centre of the test apparatus facing an open arm.
Measures included the number of open- and closed-arm entries and the time spent in the various sections of the maze, including the central platform, as well as the latency to enter an open arm. An arm entry was defined as all four feet being over a line separating the central platform from a maze arm. In addition to these spatiotemporal measures,
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frequency of the following behaviours were also observed: ‘‘rooting’’ defined as a
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scraping of the snout against the floor and walls of the apparatus , ‘‘standing’’ when
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Table 1
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Differences in porcine elevated plus-maze behavior between a treatment group subject to blood sampling
. Ž .
prior to testing and a control group no blood sampling were not significant. The percent of variation in behavior for which group accounted is given by the variable r2, derived from linear analysis of variance.
There were 10 weaned female pigs in each group
2
Behavior Treatment group Control group r
Mean SE Range Mean SE Range
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Open entries total 2.4 0.7 0–6 2.2 0.6 0–5 0.003
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Open time total 69.5 17.6 0–160 63.8 17.6 0–139 0.003
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Closed entries total 2.5 0.5 0–6 2.2 0.5 0–4 0.009
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Closed time total 86.7 21.2 0–166 98.8 25.8 0–218 0.008
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Center time total 143.8 30.1 36–300 137.4 24.6 61–300 0.002
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Total entries total 4.9 1.1 0–10 4.4 1.0 0–9 0.007
Latency to enter open arm 98.0 30.0 0–279 61.2 25.9 0–248 0.05
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Standing frequency 8.4 1.4 3–18 7.9 0.8 5–14 0.005
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Rooting frequency 8.4 1.4 1–15 6.1 1.3 0–13 0.07
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Dipping frequency 4.1 1.2 0–10 3.6 1.0 0–9 0.006
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Defecation frequency 0.1 0.1 0–1 0.4 0.2 0–1 0.12
Žplacement of the snout over the edge of open arms at floor level, the pig standing either .
in open arms or the central square of the apparatus .
3. Statistics
The Wilcoxon signed ranks test was used to test for differences in location between the two groups and r2, derived from linear analysis of variance, was used to estimate the percent of variation in behaviour for which the treatments accounted. Nonparametric methods were used, as some of the data did not conform to the assumption of parametric statistics. All tests were double sided.
4. Results
There were no significant differences in location between the mean values of
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behaviour for the two treatments Table 1 and treatment accounted for very little of the
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variation in behaviour between groups see r values in Table 1 .
5. Discussion and conclusion
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pig production see Gonyou et al., 1986; Hemsworth et al., 1990; Tanida et al., 1995 and subjective observations indicate that handling is aversive to animals in our experi-mental herd. A high level of fear towards humans in the transport situation may have reduced the behavioural differences between the groups through ceiling effects. In the present experiment it is therefore concluded that differences in the treatment, blood sampling followed by transport or ‘‘mere’’ transport, were not important in determining the plus-maze behaviour of the pigs tested. However, before any conclusive statement can be made, similar experiments should be performed on pigs that are less fearful of humans.
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