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Effect of housing on open-field test behavior of gestating gilts
Applied Animal Behaviour Science, 17 {1987) 83-93
83
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Effect of Housing on Open-Field Test B e h a v i o r of Gestating Gilts LATHROP TAYLOR and T.H. FRIEND'
Department of Animal Science, Texas A & M University, College Station, TX 77843 (U.S.A.) Technical article 21190 from the Texas Agricultural Experimental Station (Accepted for publication 1 August 1986)
ABSTRACT Taylor, L. and Friend, T.H., 1987. Effect of housing on open-field test behavior of gestating gilts. Appl. Anim. Behav. Sci., 17: 83-93. Open-field test behaviors of 36 gestating gilts maintained in either tethers, crates, loose stalls or dirt-lot (N=9 per treatment) were recorded. The gestation crates (C) were 0.6 m wide by 1.7 m long and enclosed by bars on all 4 sides. Tethered (T) gilts were anchored to the concrete floor by 50.8-cm chains attached to neck collars. The 0.6 X 1.7-m loose stalls ( LS ) opened into a slatted concrete dunging area ( 0.7 X 1.7 m) containing a nipple waterer which was shared by 3 loose stalls. The dirt-lot (DL) was 15.2X30.5 m with a 2-sided shed at one end which contained 3 feeding stalls (each 0.6X 1.7 m) and a den area (2.9X 1.9 m). The gilts were tested for 5 min 3 days after being bred and placed in their respective treatments, and weekly thereafter for 8 weeks. The field tests were conducted in a 3 X 12-m enclosure on pasture. Data collected included numbers of bouts and time spent chewing, grazing, snout employment (rooting, nudging and sniffing), vocalizations, standing, walking, trotting, running/buckingand distance traveled. Across all test days, the T and C gilts performed more bouts of standing and walking than did DL gilts. Crated gilts ran/bucked more than T gilts, who ran/bucked more than LS gilts, and LS gilts ran/bucked more than DL gilts. These findings suggest that an increased specific-action potential for specific innate motor patterns results from maintaining gilts in housing with minimal amounts of maneuvering and interaction room.
INTRODUCTION
Maintaining livestock at high density levels is a well-established practice, both nationally and internationally (Fraser, 1975). Concomitant with this trend has been a decrease in the degree of environmental complexity experienced by the animals, which has led to increases in behavioral problems (Stolba, 1981). 'Author to w h o m correspondence should be addressed.
0168-1591/87/$03.50
© 1987 Elsevier Science Publishers B.V.
84 Behavior is the function by which an individual mediates with his/her immediate environment ( Fraser and Fox, 1983 ). Normally, behavior is an adaptive response to some change in the internal or external environment. Therefore, the degree of behavioral adaptation possible is determined by features of the environment (Fraser, 1975). Many motivations are constantly frustrated due to the absence of certain key stimuli in intensive-housing situations. Impeded motivations, or drives, do not wane with time; rather they build up in intensity (Lorenz, 1981 ). In addition, internal readiness to perform a given innate motor pattern does not recover from exhaustion to a predetermined level, but continues to build up as long as the animal is deprived of adequate stimulation. This accumulation of specific-action potential (SAP) or "damming-up" of an instinctive action results in threshold lowering and an increase in general excitability. The increase in excitability and threshold lowering due to increased SAP for an instinctive action often causes that behavior to be re-directed (i.e. the behavior is performed in response to a substitute stimulus). Vacuum activities, the performance of innate behavior patterns in the apparent absence of releasing stimuli, frequently result from lowering of the threshold for those behaviors (Lorenz, 1981 ). The frequency with which a motor pattern is performed as a vacuum activity is correlated with the frequency with which it is normally performed. Craig (1918) demonstrated that the "dammed-up" motor pattern actually creates an excitation of its own, which activates the animal and causes him to search for appropriate releasing stimuli (appetitive behavior). Two side effects can obscure the accumulation of this action-specific excitability: (1) true atrophy of the activity caused by its remaining inactive for extended periods; (2) waning of general arousal (Lorenz, 1981). As a result of the second effect, environmental constancy for captive animals is a "dangerous pathogenic factor" because it tends to slow down both basal metabolism and nervous processes ( Lorenz, 1981 ). Only a few innate motor patterns are known which fail to result in appetitive behavior due to deprivation of the appropriate releasing stimuli. The "damming up" phenomenon has been documented in several species of mammals (Chepko, 1971; Leyhausen, 1979; Lorenz, 1981 ), but has only recently been investigated in intensively-housed farm animals (Dellmeier et al., 1985 ). The latter authors used an open-field test situation to study the effects of chronic movement restriction on young calves. Mean number of bucks, canter and trotting steps, and number of social encounters exhibited during a 20-min open-field test increased with increasing levels of housing restriction. High occurences of these behaviors were correlated with physiological changes indicative of chronic stress (Friend et al., 1985). The psychological procedure of "open-field" refers to the freedom perceived by the subject to perform any behaviors it feels the drive to do. Open-field
85 testing has been used to study the effects of early handling (Doty and Doty, 1967), drugs (Leavitt, 1969) and temperament (Kilgour, 1975) in both lab° oratory and farm species. Open-field test situations have been used to study the reactions of growing pigs to brief periods of isolation ( Fraser, 1974) and to index "emotionality" of pigs (Beilharz and Cox, 1967). The relationships between different types of vocalizations and their suitability as a gross index of individual differences were used to propose a "reactivity" test for swine (Fraser, 1974). Differences in behavior were attributed to a build-up of general excitement level. The concept of impeded drives due to intensive housing of livestock has been mentioned by other researchers also i Fraser, 1980; Buchanauer, 1982; Fox, 1984). For example, kinetic behaviors are innate, but are often prevented by intensive husbandry conditions. Fraser (1980) asserts that when the kinetic needs of an animal are not met, the result is often hypokinethesia (a decreased input of the movement sensation system) which generates anomalous forms of behavior such as orosthenia (e.g. tail-biting, bar-biting), but Fraser does not suggest a mechanism for the development of orosthenia. The objectives of this study were to determine if the type of housing and the amount of time spent in each type influence behaviors displayed by gestating gilts during open-field testing. MATERIALSAND METHODS Twelve Dekalb crossbred gilts were blocked by breeding date and randomly assigned in groups of 3 to each of the 4 treatments crates (C), tethers i T ) , loose stalls (LS), and dirt-lot (DL), for each of 3 replications iN= 36). The gestation crates were 0.6 m wide by 1.7 m long and enclosed on all four sides. Tethered gilts were restricted to a slightly smaller amount of space than that of a crate by collars attached to 50.8-cm chains which were bolted to the floor. The 0.6 X 1.7-m LS opened into a slatted concrete dunging area (0.7 X 1.7 m ) which contained a nipple waterer and was shared by 3 loose stalls. The DL was 15.2 X 30.5 m, with a 2-sided shed at one end which contained 3 feeding stalls ( each 0.6 X 1.7 m ) and a den area ( 2.9 X 1.9 m ). Water was available ad libitum via a nipple valve in all treatments. All gilts were fed 2.3 kg of a standard gestation ration per day. Gilts (6-7 months old) were estrous-synchronized via the use of transport phenomena ( Zimmerman, 1976). Each trio of gilts was moved simultaneously into their respective treatment (Day 0) as soon as they were bred. All gilts were bred by a boar at least twice during estrus, with the last breeding covering a time-period of not more than 24 h between members of a group. Each gilt was released from her housing treatment weekly for an individual 5-rain open-field test in a 3 X 12-m enclosure on pasture. Kilgour i1975) found that behavior exhibited during the initial 5 min of an open-field test was rep-
86
resentative of t h a t exhibited during a 15-rain test. This pen was novel to all test animals during their first field test. The traveling distance between home and test pens was approximately equal for all treatments. Behaviors performed during open-field testing were reported to an audio tape recorder and each gilt's path within the pen was traced on a scale-drawn map. Gilts were tested between 15.00 and 16.00 h beginning on Day 3 of t r e a t m e n t and weekly throughout the gestation period. Data collected included the number of bouts and total time per 5-min test of the behaviors shown in Table I. Data were analyzed using 2-way repeated measures techniques via the B M D P statistical package (Dixon, 1983). Multiple comparisons for main effects for t r e a t m e n t used Fisher's protected LSD (Snedecor and Cochran, 1980). Main effects for test day were examined with Spearman's rank test for independence. In cases of significant test day X t r e a t m e n t interactions, the interactions were found to be due to outliers a n d / o r unequal variances. These occurrences constituted violations of parametric test assumptions so non-parametric tests, Page's test for ordered alternatives and Spearman's rank correlation, were used to examine these data ( Daniel, 1978). TABLE I Definitionsof behaviors Chew: Mastication in the head-up position; mouth contains no plant material which is attached to the ground. Graze: Head in loweredposition; mouth contains plant material which is attached to the ground. Nudging: Pushing with the snout-discon an object in the environment. Rooting: Similar to nudgingbut with more forcefulpushing of snout so as to dig up the ground surface. Sniffing:Placing snout close to an object and audiblyinhaling through nostrils. Standing: Bodyis supported by all four limbs; no significant motion of body trunk is detectable. Walking: Bodyis supported by limbs while movingin a slow 4-beat gait. Trotting: Bodyis supportedby diagonal limbs alternately while movingforwardin a 2-beat gait. Running/Bucking:Canter; may includebucks and/or kicks. Distance Traveled: Length of path traveledby gilts during open-fieldtest (m). Vocalization:Any sound emitted by the vocal apparatus; includesgrunts, barks and squeals.
87 RESULTS
Gilts from all treatments showed increases in standing time, grazing time, number of grazing bouts, chewing time and number of chewing bouts as time passed (Table II ). Concomitantly, the gilts decreased the number of trotting bouts and number of vocalizations (except LS gilts) (Table II). Total time spent walking (Table III) had a test-day X treatment interaction. This interaction is due to an outlier in the dirt-lot group. The authors feel that the DL Day-10 value is not elevated, but that the DL Day-3 value is depressed due to the relative difficulty of getting some DL gilts into the test pen for their first test. Tether, C and DL animals showed decreasing trends for walking time over test days. Crated gilts spent more time walking than the other 3 treatments. TABLE II Behaviors displayed during 5-min open-field tests that had only test-day effects Test day
Time standing (s) ~ No. trotting bouts 2
3
10
17
24
31
38
45
52
200
210
220
233
221
219
235
242
1.8
2.5
3.3
1.5
2.2
1.7
1.3
1.0
No vocalizations 3
37.1
28.1
16.4
10.0
11.1
11.1
7.7
4.2
Time grazing (s) ~
98.5
95.4
118.5
139.2
128.8
124.6
130.0
134.8
No. grazing bouts 4
15.3
15.2
16.4
17.7
19.4
19.1
19.2
19.5
Time chewing (s) 4
82.3
77.2
82.3
95.0
102.1
99.3
111.2
105.1
No. chewing bouts 5
13.9
13.2
14.9
17.5
19.8
18.4
18.7
19.0
'Test day effect (P<0.0001); values in row show an increasing trend over (0.01 < P < 0 . 0 2 ) . 2Test day effect ( P < 0.007 ); values in row show a decreasing trend over test days ( 0.02 < 3Test day effect (P<0.0001); values in row show a decreasing trend over (0.001 < P < 0 . 0 0 5 ) . 4Test day effect (P<0.0001); values in row show an increasing trend over (O.001 < P < 0 . 0 0 5 ) . 5Test day effect (P<0.0001); values in row show an increasing trend over (O.005 < P < 0 . 0 1 ) .
test days P < 0.05 ). test days test days test days
88 TABLE III Total time (s) spent walking during 5-rain open-field tests 1'2 Test day
Treatment Tether s
Crate ~
Loose stall
Dirt-lots
Mean
3 10 17 24 31 38 45 52
90.3 58.7 52.5 60.8 79.5 51.5 55.2 36.3
96.1 84.9 59.7 68.2 79.4 80.6 57.4 55.6
57.2 59.9 54.9 49.7 57.6 67.8 54.4 53.6
72.0 107.8 71.0 39.6 47.9 55.9 39.5 44.1
78.1 78.7 59.8 54.5 65.4 65.3 51.7 48.5
Mean
60.6
72.7
56.9
59.7
1Test day × treatment interaction (P < 0.03). 2Crate > tether = loose stall = dirt-lot (P < 0.05). SShows a decreasing trend (0.025 < P < 0.05). 4Shows a decreaisng trend (0.01 < P < 0.025). SShows a decreasing trend (0.001 < P < 0.005).
Data for rooting, nudging and sniffing were combined into a single snoutemployment category. The gilts used their snouts on numerous aspects of their test environment, including fences, grass, ground and fire ant mounds. The number of snout-employment bouts decreased as time passed (Table IV). The findings indicate that differences in field-test behavior patterns occurred between housing treatments over all test days. Crated gilts wagged their tails most often and DL gilts wagged their tails the least over all test days (Table V). Tether and C gilts exhibited more bouts of standing and walking (Table V) than did DL animals. Crated gilts also performed more standing and walking bouts than LS animals. Time spent running/bucking showed a test d a y × t r e a t m e n t interaction (Table VI ). Decreases in the total time spent running/bucking occurred from the C to T to LS to DL treatments. Tether gilts increased their running/bucking time as the tests proceeded. Number of run/buck bouts also had a test day × treatment interaction. As with total time spent in these behaviors, the numbers of bouts also decreased from C to T to LS to DL treatments. Tether gilts also increased the number of running/bucking bouts over test days. The other treatments did not show any trend over test days. A decreasing trend over test day for DL gilts combined with a marginally increasing trend for T caused a test day × treatment interaction for distance traveled (Table VII). Crate gilts traveled farther than the other treatments during open-field testing.
89
T A B L E IV Number of snout-employment bouts during 5-min open-fieldtests~ Test day
Treatment Tether
Crate
Loose stall
Dirt-lot
Mean 2
3 10 17 24 31 38 45 52
14.2 12.6 16.4 13.0 9.9 6.9 9.6 10.4
11.3 12.4 8.2 7.9 7.3 8.7 7.9 4.1
8.2 10.1 6.2 6.3 7.7 9.7 5.8 12.0
9.8 4.8 3.1 3.5 2.6 4.6 1.4 4.5
10.9 10.1 8.7 7.8 7.0 7.5 6.3 7.9
Mean 3
11.6 a
8.5 as
8.2 ab
4.3 b
~Test day effect ( P < 0 . 0 2 ) . 2Shows a decreasing t r e n d (0.01 < P < 0.025). 3Values in the same row t h a t do not have a common superscript differ ( P < 0 . 0 3 ) .
TABLE V Behaviors displayed during 5-min open-field tests t h a t had only t r e a t m e n t effects Treatment Tether
Crate
Loose stall
Dirt-lot
No. of standing bouts 1
17.3 ab
18.8 a
14.2 bc
11.8 ¢
No. of walking bouts 2
17.2 de
19.7 d
17.8 ef
12.3 ~
Total time (s) of snout employment3
22.2 hi
2 5 . 4 hi
33.1 i
10.4 h
No. of tail wags 4
1Values in the same row t h a t Walues in the same row t h a t ~Values in the same row t h a t 4Crate > tether = loose stall >
105.0
107.7
105.3
do not have a common superscript differ (P
54.4
90 TABLE VI Running/bucking behavior during 5-min open-field tests Test day
Treatment Tether
Crate
Loose stall
Dirt-lot
Mean
8.9 3.1 7.3 11.8 5.7 7.4 6.8 7.6
1.1 0.0 0.4 0.0 5.1 0.6 0.2 0.4
4.6 5.2 11.2 9.3 8.1 9.2 9.0 7.5
13.4
7.3
1.0
Number of running/bucking bouts 4~'~ 3 0.46 2.7 10 3.9 4.1 17 3.8 10.1 24 6.1 7.7 31 4.8 5.1 38 6.9 7.7 45 6.1 7.9 52 6.8 3.9
3.7 1.2 3.8 4.8 2.1 3.0 2.7 4.1
0.1 0.0 0.1 0.0 1.5 0.4 0.1 0.1
Mean
3.2
0.3
Total time (s) running/bucking ''2 3 1.23 5.7 10 9.8 8.8 17 10.7 25.0 24 13.0 12.6 31 11.2 11.2 38 10.3 17.9 45 12.0 17.1 52 14.5 9.2 Mean
10.3
4.8
6.1
1.8 2.4 4.6 4.8 3.4 4.6 4.3 3.8
'Test day×treatment interaction (P<0.003). 2Crate > tether > loose stall > dirt-lot (P < 0.001 ). :'Shows an increasing trend (0.01 < P < 0.025) over test days. 4Test day×treatment interaction (P<0.03). '~Crate > tether > loose stall > dirt-lot (P < 0.001 ). 6Shows an increasing trend (0.005 < P < 0.01 ) over test days. DISCUSSION The data suggest that several factors affected the gilts' motivational states. The nature of the strangeness of the test arena can pose problems in differentiating between behaviors performed in response to the novelty of the arena and behaviors originating from other motivations (Kilgour, 1975). The relative novelty of the field test situation would be expected to be higher during the first test than on subsequent tests. Therefore, one would expect more investigatory behavior ( snout employment and locomotor activity) during the first exposure to a test pen than during later open-field tests. Although time
91 T A B L E VII Distance traveled (m) during 5-min open-field tests ''2
Test
Treatment
day Tether
Crate
Loose stall
Dirt-lot 3
Mean
3 10 17 24 31 38 45 52
35.5 46.3 45.0 51.4 63.5 49.9 45.5 55.4
84.6 73.9 113.4 71.7 70.1 94.9 78.9 50.3
52.7 40.4 50.7 54.3 49.5 65.9 49.8 56.0
77.1 86.7 70.7 23.2 51.6 30.9 24.5 28.7
64.6 62.5 72.3 50.9 58.5 62.3 50.8 47.5
Mean
49.1
79.7
52.4
49.2
1Test day × treatment interaction ( P < 0.03). 2Crate > loose stall > tether = dirt-lot ( P < 0.01 ). 3Shows a decreasing trend (0.025 < P < 0.05).
spent in snout employment and trotting did not change, the number of bouts performed did decrease over subsequent test days. This finding, coupled with the decreased time spent walking and increased standing time over test days, may be interpreted as indicating lowered excitement levels due to the decreased relative novelty of the testing area with repeated exposure. The lowered number of vocalizations over time also indicate decreased excitement levels. The greater number of bouts of standing, walking, running/bucking and the greater amount of time spent running/bucking exhibited by the individuallyhoused ( T, C) gilts when compared to the group-housed (LS, DL) gilts suggest a group size and/or "maneuvering and interacting room" (MIR) effect on field test behavior. This finding is in contradiction to Fraser's {1974) report of no differences between group-housed and individually-housed pigs fieldtested on a concrete runway. The differing results of the two studies may be attributed to the testing procedures. The results of this study indicate that accumulation of SAP for specific motor patterns did occur in the gilts. Number of bouts and total time spent grazing and chewing increased over test days. The DL gilts (most MIR) decreased their distance traveled during subsequent field testing, while the T gilts ( least MIR) showed a marginally increasing trend in distance traveled (0.05 < P < 0.1 ). The T gilts performed more bouts of snout enployment than did DL gilts. These findings suggest that the T gilts, who had minimal opportunities to move about and use their snouts for investigatory activities, intensified their "desire" to perform such behavior patterns. In addition, the T gilts spent more time, and performed more bouts of, running/bucking across test
92 days. This finding indicates that they had also experienced increased SAP for fast locomotion and continued to do so despite being given the opportunity to exercise for a 5-min period each week. On the other hand, the DL gilts had much more opportunity to perform these types of activity in their housing treatment and did not experience intensified SAP for these behavior patterns. In conclusion, all gilts responded to the initially novel testing environment by performing investigatory behaviors. With repeated field testing, the gilts showed increases in standing time, grazing time, grazing bouts, chewing time and chewing bouts. These findings may reflect adjustment to the housing treatments and/or field test situation. Decreases in the number of trotting bouts, vocalizations and number of snout-employment bouts also indicate adjustment to the housing/field test regime. The gilts in more intense confinement performed more bouts of standing and walking than did the gilts from higher-MIR housing situations. This finding, coupled with the fact that the total time spent in these behaviors did not differ between treatments, indicates an increased level of "restlessness" due to "damming up" of the drives for certain innate motor patterns among the lowerMIR housed gilts. In addition, gilts from low-MIR housing spent more of the field-test period performing snout employment and locomotory activities than gilts from treatments with higher MIR. These findings suggest an increased specific-action potential for specific innate motor patterns related especially to grazing results from maintaining gilts in housing with minimal amounts of maneuvering and interacting room. ACKNOWLEDGEMENTS The authors gratefully acknowledge partial financial support for this research by the National Pork Producers Council. L.T. gratefully acknowledges partial financial support by a Tom Slick Research Fellowship.
REFERENCES Beilharz, R.G. and Cox, D.F., 1967. Genetic analysis of open fieldtest behavior in swine. J. Anita. Sci., 26: 988-990. Buchanauer, D., 1982. Parameters for assessing welfare; ethological criteria.In: W. Sybesma (Editor), The Welfare of Pigs. Martinus Nijhoff, London, pp. 75-89. Chepko, B.D., 1971. A preliminary study of the effects of play deprivation on young goats. Z. Tierpsychol., 28: 517-526. Craig, W., 1918. Appetites and aversions as constituents of instincts. Biol. Bull. Woods Hole, 34: 91-107. Daniel, W.W., 1978. Applied Nonparametric Statistics.Houghton Miffline, Boston. Dellmeier, G.R., Friend, T.H. and Gbur, E.E., 1985. Comparison of four methods of calfconfinement. II. Behavior. J. Anita. Sci.,60: 1102-1109. Dixon, W.J. (Editor), 1983. BMDP StatisticalSoftware. University of California Press, Berkeley.
93 Doty, B.A. and Doty, L.A., 1967. Effect of handling at various ages on later open field behavior. Can. J. Psychol., 21: 463-470. Fox, M.W., 1984. Farm Animals - - Husbandry, Behavior, and Veterinary Practice (Viewpoints of Critic). University Park Press, Baltimore. Fraser, A.F., 1975. The behaviour of livestock under intensive conditions of husbandry. Appl. Anita. Ethol., 1: 111-112. Fraser, A.F., 1980. Ethics and ethology. Anita. Regul. Stud., 2: 155-163. Fraser, A.F. and Fox, M.W., 1983. The effects of ethostasis on farm animal behavior: A theoretical overview. Int. J. Stud. Anita. Probl., 4: 59-70. Fraser, D., 1974. The volcalizations and other behaviour of growing pigs in an "open field" test. Appl. Anita. Ethol., 1: 3-16. Friend, T.H., Dellmeier, G.R. and Gbur, E.E., 1985. Comparison of four methods of calf confinement. I. Physiology. J. Anita. Sci., 60: 1095-1101. Kilgour, R., 1975. The open field test as an assessment of the temperament of dairy cows. Anita. Behav., 23: 615-624. Leavitt, F.I., 1969. Drug-induced modifications in sexual behavior and open-field locomotion of male rats. Physiol. Behav., 4: 677-683. Leyhausen, P., 1979. Cat Behavior. Garland, New York. Lorenz, K., 1981. The Foundations of Ethology. Springer-Verlag, New York. Snedecor, G.W. and Cochran, W.G., 1980. Statistical Methods. 7th edn. Iowa State University Press, Ames. Stolba, A., 1981. A family system in enriched pens as a novel method of pig housing. In: Alternatives to Intensive Husbandry Systems. U.F.A.W. Symposium, Potters Bar, Hefts., England, July, pp. 52-67. Zimmerman, D.R., 1976. Repalcement gilt management. Proc. 1976 American Pork Congress, pp. 25-26.
83
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Effect of Housing on Open-Field Test B e h a v i o r of Gestating Gilts LATHROP TAYLOR and T.H. FRIEND'
Department of Animal Science, Texas A & M University, College Station, TX 77843 (U.S.A.) Technical article 21190 from the Texas Agricultural Experimental Station (Accepted for publication 1 August 1986)
ABSTRACT Taylor, L. and Friend, T.H., 1987. Effect of housing on open-field test behavior of gestating gilts. Appl. Anim. Behav. Sci., 17: 83-93. Open-field test behaviors of 36 gestating gilts maintained in either tethers, crates, loose stalls or dirt-lot (N=9 per treatment) were recorded. The gestation crates (C) were 0.6 m wide by 1.7 m long and enclosed by bars on all 4 sides. Tethered (T) gilts were anchored to the concrete floor by 50.8-cm chains attached to neck collars. The 0.6 X 1.7-m loose stalls ( LS ) opened into a slatted concrete dunging area ( 0.7 X 1.7 m) containing a nipple waterer which was shared by 3 loose stalls. The dirt-lot (DL) was 15.2X30.5 m with a 2-sided shed at one end which contained 3 feeding stalls (each 0.6X 1.7 m) and a den area (2.9X 1.9 m). The gilts were tested for 5 min 3 days after being bred and placed in their respective treatments, and weekly thereafter for 8 weeks. The field tests were conducted in a 3 X 12-m enclosure on pasture. Data collected included numbers of bouts and time spent chewing, grazing, snout employment (rooting, nudging and sniffing), vocalizations, standing, walking, trotting, running/buckingand distance traveled. Across all test days, the T and C gilts performed more bouts of standing and walking than did DL gilts. Crated gilts ran/bucked more than T gilts, who ran/bucked more than LS gilts, and LS gilts ran/bucked more than DL gilts. These findings suggest that an increased specific-action potential for specific innate motor patterns results from maintaining gilts in housing with minimal amounts of maneuvering and interaction room.
INTRODUCTION
Maintaining livestock at high density levels is a well-established practice, both nationally and internationally (Fraser, 1975). Concomitant with this trend has been a decrease in the degree of environmental complexity experienced by the animals, which has led to increases in behavioral problems (Stolba, 1981). 'Author to w h o m correspondence should be addressed.
0168-1591/87/$03.50
© 1987 Elsevier Science Publishers B.V.
84 Behavior is the function by which an individual mediates with his/her immediate environment ( Fraser and Fox, 1983 ). Normally, behavior is an adaptive response to some change in the internal or external environment. Therefore, the degree of behavioral adaptation possible is determined by features of the environment (Fraser, 1975). Many motivations are constantly frustrated due to the absence of certain key stimuli in intensive-housing situations. Impeded motivations, or drives, do not wane with time; rather they build up in intensity (Lorenz, 1981 ). In addition, internal readiness to perform a given innate motor pattern does not recover from exhaustion to a predetermined level, but continues to build up as long as the animal is deprived of adequate stimulation. This accumulation of specific-action potential (SAP) or "damming-up" of an instinctive action results in threshold lowering and an increase in general excitability. The increase in excitability and threshold lowering due to increased SAP for an instinctive action often causes that behavior to be re-directed (i.e. the behavior is performed in response to a substitute stimulus). Vacuum activities, the performance of innate behavior patterns in the apparent absence of releasing stimuli, frequently result from lowering of the threshold for those behaviors (Lorenz, 1981 ). The frequency with which a motor pattern is performed as a vacuum activity is correlated with the frequency with which it is normally performed. Craig (1918) demonstrated that the "dammed-up" motor pattern actually creates an excitation of its own, which activates the animal and causes him to search for appropriate releasing stimuli (appetitive behavior). Two side effects can obscure the accumulation of this action-specific excitability: (1) true atrophy of the activity caused by its remaining inactive for extended periods; (2) waning of general arousal (Lorenz, 1981). As a result of the second effect, environmental constancy for captive animals is a "dangerous pathogenic factor" because it tends to slow down both basal metabolism and nervous processes ( Lorenz, 1981 ). Only a few innate motor patterns are known which fail to result in appetitive behavior due to deprivation of the appropriate releasing stimuli. The "damming up" phenomenon has been documented in several species of mammals (Chepko, 1971; Leyhausen, 1979; Lorenz, 1981 ), but has only recently been investigated in intensively-housed farm animals (Dellmeier et al., 1985 ). The latter authors used an open-field test situation to study the effects of chronic movement restriction on young calves. Mean number of bucks, canter and trotting steps, and number of social encounters exhibited during a 20-min open-field test increased with increasing levels of housing restriction. High occurences of these behaviors were correlated with physiological changes indicative of chronic stress (Friend et al., 1985). The psychological procedure of "open-field" refers to the freedom perceived by the subject to perform any behaviors it feels the drive to do. Open-field
85 testing has been used to study the effects of early handling (Doty and Doty, 1967), drugs (Leavitt, 1969) and temperament (Kilgour, 1975) in both lab° oratory and farm species. Open-field test situations have been used to study the reactions of growing pigs to brief periods of isolation ( Fraser, 1974) and to index "emotionality" of pigs (Beilharz and Cox, 1967). The relationships between different types of vocalizations and their suitability as a gross index of individual differences were used to propose a "reactivity" test for swine (Fraser, 1974). Differences in behavior were attributed to a build-up of general excitement level. The concept of impeded drives due to intensive housing of livestock has been mentioned by other researchers also i Fraser, 1980; Buchanauer, 1982; Fox, 1984). For example, kinetic behaviors are innate, but are often prevented by intensive husbandry conditions. Fraser (1980) asserts that when the kinetic needs of an animal are not met, the result is often hypokinethesia (a decreased input of the movement sensation system) which generates anomalous forms of behavior such as orosthenia (e.g. tail-biting, bar-biting), but Fraser does not suggest a mechanism for the development of orosthenia. The objectives of this study were to determine if the type of housing and the amount of time spent in each type influence behaviors displayed by gestating gilts during open-field testing. MATERIALSAND METHODS Twelve Dekalb crossbred gilts were blocked by breeding date and randomly assigned in groups of 3 to each of the 4 treatments crates (C), tethers i T ) , loose stalls (LS), and dirt-lot (DL), for each of 3 replications iN= 36). The gestation crates were 0.6 m wide by 1.7 m long and enclosed on all four sides. Tethered gilts were restricted to a slightly smaller amount of space than that of a crate by collars attached to 50.8-cm chains which were bolted to the floor. The 0.6 X 1.7-m LS opened into a slatted concrete dunging area (0.7 X 1.7 m ) which contained a nipple waterer and was shared by 3 loose stalls. The DL was 15.2 X 30.5 m, with a 2-sided shed at one end which contained 3 feeding stalls ( each 0.6 X 1.7 m ) and a den area ( 2.9 X 1.9 m ). Water was available ad libitum via a nipple valve in all treatments. All gilts were fed 2.3 kg of a standard gestation ration per day. Gilts (6-7 months old) were estrous-synchronized via the use of transport phenomena ( Zimmerman, 1976). Each trio of gilts was moved simultaneously into their respective treatment (Day 0) as soon as they were bred. All gilts were bred by a boar at least twice during estrus, with the last breeding covering a time-period of not more than 24 h between members of a group. Each gilt was released from her housing treatment weekly for an individual 5-rain open-field test in a 3 X 12-m enclosure on pasture. Kilgour i1975) found that behavior exhibited during the initial 5 min of an open-field test was rep-
86
resentative of t h a t exhibited during a 15-rain test. This pen was novel to all test animals during their first field test. The traveling distance between home and test pens was approximately equal for all treatments. Behaviors performed during open-field testing were reported to an audio tape recorder and each gilt's path within the pen was traced on a scale-drawn map. Gilts were tested between 15.00 and 16.00 h beginning on Day 3 of t r e a t m e n t and weekly throughout the gestation period. Data collected included the number of bouts and total time per 5-min test of the behaviors shown in Table I. Data were analyzed using 2-way repeated measures techniques via the B M D P statistical package (Dixon, 1983). Multiple comparisons for main effects for t r e a t m e n t used Fisher's protected LSD (Snedecor and Cochran, 1980). Main effects for test day were examined with Spearman's rank test for independence. In cases of significant test day X t r e a t m e n t interactions, the interactions were found to be due to outliers a n d / o r unequal variances. These occurrences constituted violations of parametric test assumptions so non-parametric tests, Page's test for ordered alternatives and Spearman's rank correlation, were used to examine these data ( Daniel, 1978). TABLE I Definitionsof behaviors Chew: Mastication in the head-up position; mouth contains no plant material which is attached to the ground. Graze: Head in loweredposition; mouth contains plant material which is attached to the ground. Nudging: Pushing with the snout-discon an object in the environment. Rooting: Similar to nudgingbut with more forcefulpushing of snout so as to dig up the ground surface. Sniffing:Placing snout close to an object and audiblyinhaling through nostrils. Standing: Bodyis supported by all four limbs; no significant motion of body trunk is detectable. Walking: Bodyis supported by limbs while movingin a slow 4-beat gait. Trotting: Bodyis supportedby diagonal limbs alternately while movingforwardin a 2-beat gait. Running/Bucking:Canter; may includebucks and/or kicks. Distance Traveled: Length of path traveledby gilts during open-fieldtest (m). Vocalization:Any sound emitted by the vocal apparatus; includesgrunts, barks and squeals.
87 RESULTS
Gilts from all treatments showed increases in standing time, grazing time, number of grazing bouts, chewing time and number of chewing bouts as time passed (Table II ). Concomitantly, the gilts decreased the number of trotting bouts and number of vocalizations (except LS gilts) (Table II). Total time spent walking (Table III) had a test-day X treatment interaction. This interaction is due to an outlier in the dirt-lot group. The authors feel that the DL Day-10 value is not elevated, but that the DL Day-3 value is depressed due to the relative difficulty of getting some DL gilts into the test pen for their first test. Tether, C and DL animals showed decreasing trends for walking time over test days. Crated gilts spent more time walking than the other 3 treatments. TABLE II Behaviors displayed during 5-min open-field tests that had only test-day effects Test day
Time standing (s) ~ No. trotting bouts 2
3
10
17
24
31
38
45
52
200
210
220
233
221
219
235
242
1.8
2.5
3.3
1.5
2.2
1.7
1.3
1.0
No vocalizations 3
37.1
28.1
16.4
10.0
11.1
11.1
7.7
4.2
Time grazing (s) ~
98.5
95.4
118.5
139.2
128.8
124.6
130.0
134.8
No. grazing bouts 4
15.3
15.2
16.4
17.7
19.4
19.1
19.2
19.5
Time chewing (s) 4
82.3
77.2
82.3
95.0
102.1
99.3
111.2
105.1
No. chewing bouts 5
13.9
13.2
14.9
17.5
19.8
18.4
18.7
19.0
'Test day effect (P<0.0001); values in row show an increasing trend over (0.01 < P < 0 . 0 2 ) . 2Test day effect ( P < 0.007 ); values in row show a decreasing trend over test days ( 0.02 < 3Test day effect (P<0.0001); values in row show a decreasing trend over (0.001 < P < 0 . 0 0 5 ) . 4Test day effect (P<0.0001); values in row show an increasing trend over (O.001 < P < 0 . 0 0 5 ) . 5Test day effect (P<0.0001); values in row show an increasing trend over (O.005 < P < 0 . 0 1 ) .
test days P < 0.05 ). test days test days test days
88 TABLE III Total time (s) spent walking during 5-rain open-field tests 1'2 Test day
Treatment Tether s
Crate ~
Loose stall
Dirt-lots
Mean
3 10 17 24 31 38 45 52
90.3 58.7 52.5 60.8 79.5 51.5 55.2 36.3
96.1 84.9 59.7 68.2 79.4 80.6 57.4 55.6
57.2 59.9 54.9 49.7 57.6 67.8 54.4 53.6
72.0 107.8 71.0 39.6 47.9 55.9 39.5 44.1
78.1 78.7 59.8 54.5 65.4 65.3 51.7 48.5
Mean
60.6
72.7
56.9
59.7
1Test day × treatment interaction (P < 0.03). 2Crate > tether = loose stall = dirt-lot (P < 0.05). SShows a decreasing trend (0.025 < P < 0.05). 4Shows a decreaisng trend (0.01 < P < 0.025). SShows a decreasing trend (0.001 < P < 0.005).
Data for rooting, nudging and sniffing were combined into a single snoutemployment category. The gilts used their snouts on numerous aspects of their test environment, including fences, grass, ground and fire ant mounds. The number of snout-employment bouts decreased as time passed (Table IV). The findings indicate that differences in field-test behavior patterns occurred between housing treatments over all test days. Crated gilts wagged their tails most often and DL gilts wagged their tails the least over all test days (Table V). Tether and C gilts exhibited more bouts of standing and walking (Table V) than did DL animals. Crated gilts also performed more standing and walking bouts than LS animals. Time spent running/bucking showed a test d a y × t r e a t m e n t interaction (Table VI ). Decreases in the total time spent running/bucking occurred from the C to T to LS to DL treatments. Tether gilts increased their running/bucking time as the tests proceeded. Number of run/buck bouts also had a test day × treatment interaction. As with total time spent in these behaviors, the numbers of bouts also decreased from C to T to LS to DL treatments. Tether gilts also increased the number of running/bucking bouts over test days. The other treatments did not show any trend over test days. A decreasing trend over test day for DL gilts combined with a marginally increasing trend for T caused a test day × treatment interaction for distance traveled (Table VII). Crate gilts traveled farther than the other treatments during open-field testing.
89
T A B L E IV Number of snout-employment bouts during 5-min open-fieldtests~ Test day
Treatment Tether
Crate
Loose stall
Dirt-lot
Mean 2
3 10 17 24 31 38 45 52
14.2 12.6 16.4 13.0 9.9 6.9 9.6 10.4
11.3 12.4 8.2 7.9 7.3 8.7 7.9 4.1
8.2 10.1 6.2 6.3 7.7 9.7 5.8 12.0
9.8 4.8 3.1 3.5 2.6 4.6 1.4 4.5
10.9 10.1 8.7 7.8 7.0 7.5 6.3 7.9
Mean 3
11.6 a
8.5 as
8.2 ab
4.3 b
~Test day effect ( P < 0 . 0 2 ) . 2Shows a decreasing t r e n d (0.01 < P < 0.025). 3Values in the same row t h a t do not have a common superscript differ ( P < 0 . 0 3 ) .
TABLE V Behaviors displayed during 5-min open-field tests t h a t had only t r e a t m e n t effects Treatment Tether
Crate
Loose stall
Dirt-lot
No. of standing bouts 1
17.3 ab
18.8 a
14.2 bc
11.8 ¢
No. of walking bouts 2
17.2 de
19.7 d
17.8 ef
12.3 ~
Total time (s) of snout employment3
22.2 hi
2 5 . 4 hi
33.1 i
10.4 h
No. of tail wags 4
1Values in the same row t h a t Walues in the same row t h a t ~Values in the same row t h a t 4Crate > tether = loose stall >
105.0
107.7
105.3
do not have a common superscript differ (P
54.4
90 TABLE VI Running/bucking behavior during 5-min open-field tests Test day
Treatment Tether
Crate
Loose stall
Dirt-lot
Mean
8.9 3.1 7.3 11.8 5.7 7.4 6.8 7.6
1.1 0.0 0.4 0.0 5.1 0.6 0.2 0.4
4.6 5.2 11.2 9.3 8.1 9.2 9.0 7.5
13.4
7.3
1.0
Number of running/bucking bouts 4~'~ 3 0.46 2.7 10 3.9 4.1 17 3.8 10.1 24 6.1 7.7 31 4.8 5.1 38 6.9 7.7 45 6.1 7.9 52 6.8 3.9
3.7 1.2 3.8 4.8 2.1 3.0 2.7 4.1
0.1 0.0 0.1 0.0 1.5 0.4 0.1 0.1
Mean
3.2
0.3
Total time (s) running/bucking ''2 3 1.23 5.7 10 9.8 8.8 17 10.7 25.0 24 13.0 12.6 31 11.2 11.2 38 10.3 17.9 45 12.0 17.1 52 14.5 9.2 Mean
10.3
4.8
6.1
1.8 2.4 4.6 4.8 3.4 4.6 4.3 3.8
'Test day×treatment interaction (P<0.003). 2Crate > tether > loose stall > dirt-lot (P < 0.001 ). :'Shows an increasing trend (0.01 < P < 0.025) over test days. 4Test day×treatment interaction (P<0.03). '~Crate > tether > loose stall > dirt-lot (P < 0.001 ). 6Shows an increasing trend (0.005 < P < 0.01 ) over test days. DISCUSSION The data suggest that several factors affected the gilts' motivational states. The nature of the strangeness of the test arena can pose problems in differentiating between behaviors performed in response to the novelty of the arena and behaviors originating from other motivations (Kilgour, 1975). The relative novelty of the field test situation would be expected to be higher during the first test than on subsequent tests. Therefore, one would expect more investigatory behavior ( snout employment and locomotor activity) during the first exposure to a test pen than during later open-field tests. Although time
91 T A B L E VII Distance traveled (m) during 5-min open-field tests ''2
Test
Treatment
day Tether
Crate
Loose stall
Dirt-lot 3
Mean
3 10 17 24 31 38 45 52
35.5 46.3 45.0 51.4 63.5 49.9 45.5 55.4
84.6 73.9 113.4 71.7 70.1 94.9 78.9 50.3
52.7 40.4 50.7 54.3 49.5 65.9 49.8 56.0
77.1 86.7 70.7 23.2 51.6 30.9 24.5 28.7
64.6 62.5 72.3 50.9 58.5 62.3 50.8 47.5
Mean
49.1
79.7
52.4
49.2
1Test day × treatment interaction ( P < 0.03). 2Crate > loose stall > tether = dirt-lot ( P < 0.01 ). 3Shows a decreasing trend (0.025 < P < 0.05).
spent in snout employment and trotting did not change, the number of bouts performed did decrease over subsequent test days. This finding, coupled with the decreased time spent walking and increased standing time over test days, may be interpreted as indicating lowered excitement levels due to the decreased relative novelty of the testing area with repeated exposure. The lowered number of vocalizations over time also indicate decreased excitement levels. The greater number of bouts of standing, walking, running/bucking and the greater amount of time spent running/bucking exhibited by the individuallyhoused ( T, C) gilts when compared to the group-housed (LS, DL) gilts suggest a group size and/or "maneuvering and interacting room" (MIR) effect on field test behavior. This finding is in contradiction to Fraser's {1974) report of no differences between group-housed and individually-housed pigs fieldtested on a concrete runway. The differing results of the two studies may be attributed to the testing procedures. The results of this study indicate that accumulation of SAP for specific motor patterns did occur in the gilts. Number of bouts and total time spent grazing and chewing increased over test days. The DL gilts (most MIR) decreased their distance traveled during subsequent field testing, while the T gilts ( least MIR) showed a marginally increasing trend in distance traveled (0.05 < P < 0.1 ). The T gilts performed more bouts of snout enployment than did DL gilts. These findings suggest that the T gilts, who had minimal opportunities to move about and use their snouts for investigatory activities, intensified their "desire" to perform such behavior patterns. In addition, the T gilts spent more time, and performed more bouts of, running/bucking across test
92 days. This finding indicates that they had also experienced increased SAP for fast locomotion and continued to do so despite being given the opportunity to exercise for a 5-min period each week. On the other hand, the DL gilts had much more opportunity to perform these types of activity in their housing treatment and did not experience intensified SAP for these behavior patterns. In conclusion, all gilts responded to the initially novel testing environment by performing investigatory behaviors. With repeated field testing, the gilts showed increases in standing time, grazing time, grazing bouts, chewing time and chewing bouts. These findings may reflect adjustment to the housing treatments and/or field test situation. Decreases in the number of trotting bouts, vocalizations and number of snout-employment bouts also indicate adjustment to the housing/field test regime. The gilts in more intense confinement performed more bouts of standing and walking than did the gilts from higher-MIR housing situations. This finding, coupled with the fact that the total time spent in these behaviors did not differ between treatments, indicates an increased level of "restlessness" due to "damming up" of the drives for certain innate motor patterns among the lowerMIR housed gilts. In addition, gilts from low-MIR housing spent more of the field-test period performing snout employment and locomotory activities than gilts from treatments with higher MIR. These findings suggest an increased specific-action potential for specific innate motor patterns related especially to grazing results from maintaining gilts in housing with minimal amounts of maneuvering and interacting room. ACKNOWLEDGEMENTS The authors gratefully acknowledge partial financial support for this research by the National Pork Producers Council. L.T. gratefully acknowledges partial financial support by a Tom Slick Research Fellowship.
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93 Doty, B.A. and Doty, L.A., 1967. Effect of handling at various ages on later open field behavior. Can. J. Psychol., 21: 463-470. Fox, M.W., 1984. Farm Animals - - Husbandry, Behavior, and Veterinary Practice (Viewpoints of Critic). University Park Press, Baltimore. Fraser, A.F., 1975. The behaviour of livestock under intensive conditions of husbandry. Appl. Anita. Ethol., 1: 111-112. Fraser, A.F., 1980. Ethics and ethology. Anita. Regul. Stud., 2: 155-163. Fraser, A.F. and Fox, M.W., 1983. The effects of ethostasis on farm animal behavior: A theoretical overview. Int. J. Stud. Anita. Probl., 4: 59-70. Fraser, D., 1974. The volcalizations and other behaviour of growing pigs in an "open field" test. Appl. Anita. Ethol., 1: 3-16. Friend, T.H., Dellmeier, G.R. and Gbur, E.E., 1985. Comparison of four methods of calf confinement. I. Physiology. J. Anita. Sci., 60: 1095-1101. Kilgour, R., 1975. The open field test as an assessment of the temperament of dairy cows. Anita. Behav., 23: 615-624. Leavitt, F.I., 1969. Drug-induced modifications in sexual behavior and open-field locomotion of male rats. Physiol. Behav., 4: 677-683. Leyhausen, P., 1979. Cat Behavior. Garland, New York. Lorenz, K., 1981. The Foundations of Ethology. Springer-Verlag, New York. Snedecor, G.W. and Cochran, W.G., 1980. Statistical Methods. 7th edn. Iowa State University Press, Ames. Stolba, A., 1981. A family system in enriched pens as a novel method of pig housing. In: Alternatives to Intensive Husbandry Systems. U.F.A.W. Symposium, Potters Bar, Hefts., England, July, pp. 52-67. Zimmerman, D.R., 1976. Repalcement gilt management. Proc. 1976 American Pork Congress, pp. 25-26.