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The response of sows to novel visual, olfactory, auditory and tactile stimuli
Applied Animal Behaviour Science, 35 ( 1993 ) 2 5 5 - 2 6 6
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Elsevier Science Publishers B.V., A m s t e r d a m
The response of sows to novel visual, olfactory, auditory and tactile stimuli G.D. Hutson, L.G. Dickenson, J.L. Wilkinson and B.G. Luxford 1 School of Agriculture and Forestry, University of Melbourne, Parkville, Vic. 3052, Australia (Accepted 3 June 1992)
ABSTRACT Hutson, G.D., Dickenson, L.G., Wilkinson, J.L. and Luxford, B.G., 1993. The response of sows to novel visual, olfactory, auditory and tactile stimuli. AppL Anim. Behav. Sci., 35: 255-266. The responses of sows to 20 stimuli from five sensory categories were evaluated with the aim of selecting one stimulus from each category as a test of general environmental responsiveness. The visual stimuli evaluated were a novel rod, a hanging ball, a moving chime and an umbrella. The olfactory stimuli were eucalyptus oil, perfume, ammonia and glacial acetic acid. The auditory stimuli were the sound of a cap gun, a buzzer, playback of a piglet squeal and playback of a sow grunt. The tactile stimuli were a rub, a prod, a slap on the neck, a clip placed on the ear and water tipped on the back. The complex stimuli evaluated were response to a human, food and novel-coloured food. The effect of the stimuli was analysed by comparing changes in behaviour and posture of sows in 15-s scans for 5 min, before and after stimulus presentation. Sows showed little response to the visual stimuli; the umbrella and rod elicited more exploratory responses than the chime or ball. Sows ignored ammonia and glacial acetic acid, but responded to eucalyptus oil and perfume by raising their heads and rubbing their sides and backs on the side of the stall. Sows showed variable responses to the auditory stimuli; the buzzer elicited more movement away from the stimulus. Lying sows responded to the tactile stimuli by standing more rapidly in response to the water and a slap than to a rub or a prod. All sows responded to the clip by attempting to shake it off. Sows showed no fear responses towards the h u m a n and 12 out of 15 sows made frequent contacts. Sows showed a neophobic response to blue-coloured food and only three out of 15 sows attempted to eat it. The stimuli selected for further study of general environmental responsiveness were the novel rod, eucalyptus oil, playback of the sow grunt, the clip and exposure to a human.
INTRODUCTION
In a previous study of maternal responsiveness in sows Hutson et al. ( 1991 ) found that recently farrowed sows did not respond to visual and tactile stimuli associated with a model piglet inserted underneath the udder, but did respond to an auditory stimulus, playback of a piglet squeal. The response tended Correspondence to: G.D. Hutson, School o f Agriculture a n d Forestry, University o f Melbourne, Parkville, Vic. 3052, Australia. tPresent address: Bunge Meat Industries, P.O. Box 78, Corowa, N.S.W. 2646, Australia.
© 1993 Elsevier Science Publishers B.V. All rights reserved 0 1 6 8 - 1 5 9 1 / 9 3 / $ 0 5 . 0 0
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to be all or nothing, with sows either sitting or standing in response to the squeal, or ignoring it. There was significant individual variation in responsiveness, with about 60% of individuals responding. A similar proportion of responders to squeal playback has been reported by Cronin and Cropley ( 1991 ). It is possible that the failure of some individuals to respond to playback of a loud piglet distress call may not be a function of the stimulus, but may reflect underlying genetic variation. An alternative explanation for the lack of maternal responsiveness of confined sows is that general responsiveness may have been modified in some way by the intensive environment. Broom (1986) reported that stall-housed sows were less responsive to 200 ml of water tipped on their backs than grouphoused sows. However, stall-housed sows were still very responsive to cues associated with feeding. Thus it is quite conceivable that some responses of intensively housed sows have been attenuated by the immediate and past environments and others have not. The aim of this study was to select appropriate stimuli for evaluating general environmental responsiveness in the sow, with the long term goal of measuring genetic variation in this trait. When coupled with the test of maternal responsiveness developed in previous studies (Hutson et al., 1991, 1992) we would then be able to determine whether any genetic change in maternal responsiveness was independent of any shift in general responsiveness. We evaluated a range of 20 potential test stimuli, broadly grouped into five sensory categories: visual, olfactory, auditory, tactile and complex stimuli. The aim was to screen these stimuli and select one from each group for inclusion in the test of general environmental responsiveness. Sow responses were recorded for 5 min before and after stimulus presentation. Visual stimuli evaluated were a novel rod, a hanging ball, a moving chime and an umbrella. Olfactory stimuli evaluated were eucalyptus oil, perfume, ammonia and glacial acetic acid. Auditory stimuli were the sound of a cap gun, a buzzer, playback of a piglet squeal and playback of a sow grunt. Tactile stimuli were a rub, a prod, a slap, a clip placed on the ear and water tipped on the back. Complex stimuli evaluated were response to a human, food and novel food. ANIMALS, MATERIALS A N D M E T H O D S
Animals Sixteen sows (Large White or Large White × Landrace ) from the University of Melbourne Pig Centre herd, Mt. Derrimut, were used in the tests. Parities ranged from 2 to 9 with a median of 4. The sows were normally necktethered in partial stalls on a concrete floor in a dry sow house accommodating 80 sows. All tests were done on pregnant sows between 30 and 60 days of
RESPONSE OF SOWS TO SENSORY STIMULI
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gestation. The tests were done with the sow in her normal stall. One sow died before the completion o f testing and was excluded from the analysis.
Test procedure We tested the response o f the sows to the stimuli in blocks of four sows. Eight tests were done per day, at 10: 00, 11 : 00, 12: 00, 13 : 00, 14: 00, 15: 00, 16:00 and 17:00 h. Each sow was tested twice per day, once between 10:00 and 13:00 h (a.m. tests) and once between 14:00 and 17:00 h (p.m. tests). Stimuli 1-10 were used in a.m. tests and Stimuli 11-20 were used in p.m. tests. This division was adopted as some tests required the sow to be lying down, which was m o r e probable in the afternoon. The order of stimulus presentation was randomised for each sow for a.m. and p.m. tests. A video camera m o u n t e d on a tripod was placed in the aisle in front of the sow about 3 m away. The behaviour o f the sow was then videotaped for 5 min before and after presentation o f the stimulus. Twenty test stimuli, grouped into five sensory categories, were evaluated. Test stimuli were selected on the grounds that they were novel, or had been used successfully by other researchers. The specific procedures associated for each test were:
Visual stimuli (1) Umbrella. The experimenter approached the pig's stall, tapped the middle bar on the front o f the stall with the tip o f the umbrella if the sow was not looking forwards, and then unfolded the black umbrella at a distance of 10 cm from the bar of the stall. The umbrella was spring loaded so that unfolding was automatic and rapid. After 30 s the umbrella was folded and the experim e n t e r retreated. An umbrella was used because a rapidly expanding visual stimulus is alarming to m a n y animals. For example, Duncan and Filshie (1980) found that an inflating balloon was a potent stimulus for eliciting avoidance and escape behaviour in the domestic fowl. (2) Ball on a string. A yellow plastic ball, 20 cm in diameter was suspended on a string and pulley 2 m above the sow's trough, 1 h before stimulus presentation. At the m o m e n t o f stimulus presentation the experimenter lowered the ball to a set position between the b o t t o m and middle front bars o f the stall, about 40 cm above floor level. The ball stayed in this position for the duration of the test. (3) Revolving chime. A 24-cm diameter revolving multicoloured toy chime, m o u n t e d on a wooden stand, was placed 20 cm in front of the sow's stall. The chime was left in this position for the duration of the test. (4) Novel rod. A novel rod, similar to that used by Jones ( 1988 ) in tests of fear in laying hens was used. The 36 cm × 6-cm steel rod was welded to a 15cm base and covered with six differently coloured bands of plastic tape (blue,
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white, red, yellow, black and green). The rod was placed upright in the food trough at the front of the sow's stall.
Olfactory stimuli Responses to olfactory stimuli were tested by impregnating a cotton wool swab with the odour/liquid. The swab was placed in a plastic container, carried to the stall, and then tipped into the food trough. Odours and volumes used were: (5) Eucalyptus oil--ten drops. (6) Perfume--ten squirts from an atomiser of 'Le Cardon, No. 7, Paris'. (7) Cloudy ammonia--2.5 ml of domestic cleaning a m m o n i a (3.7% NH4OH ). (8) Glacial acetic acid--2.5 ml. Glacial acetic acid was selected because of its use as a test for olfaction. Sheep will show a violent head withdrawal to cotton wool soaked in glacial acetic acid held 6 cm from the nose (Chapple and Wodzicka-Tomaszewska, 1987 ).
Complex stimuli (9) Food. Five grammes of pellets were tipped from a plastic container into the food trough from a height of 30 cm. (10) Novel food. Five grammes of pellets which had been dyed blue with food dye were tipped into the food trough. (I 1) Human. The experimenter stood in front of the stall, with feet touching the base of the trough. An open palm was held 10 cm above and in line with the middle bar of the front of the stall for 5 min. Responses to humans have been a key component of the methods developed by Hemsworth et al. ( 1986 ) to assess the effects of handling on behaviour and welfare in pigs.
Auditory stimuli (12) Capgun. The experimenter stood with feet against the trough and fired a toy cap gun 30 cm above the sow's head. The experimenter then retreated. (13) Buzzer. An electric buzzer, m o u n t e d on a wooden stand, was placed 20 cm in front of the sow's stall. The buzzer was operated remotely for 30 s. (14) Piglet squeal. A speaker was placed in position 20 cm from the front of the stall and a recorded piglet squeal was played back remotely for 30 s. (15) Sow grunt. As for Test 14, but a recorded sow grunt was played back for 30 s.
Tactile stimuli The rub, prod and slap tests were based on the slap test used by Cronin ( 1985 ) to measure sow attentiveness after naloxone treatment. (16) Rub. This test was only carried out if the sow was lying. The experimenter stood in front of the stall with feet against the trough, and rubbed the
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sow's neck, over a distance o f 15 cm, once every 10 s until the sow stood. The experimenter then retreated for the remainder o f the test. (17) Prod. As for Test 16, except the experimenter p r o d d e d the sow firmly in the neck with a r o u n d e d 10 cm length o f 15 m m diameter w o o d e n dowel, once every 10 s until the sow stood. (18) Slap. As for Test 16, except the experimenter slapped the sow firmly with a fiat palm, once every 10 s, until the sow stood. (19) Clip. The experimenter placed a spring-action "Bulldog' paper clip (65 m m long) on the middle o f the leading edge of the sow's left ear. (20) Water. This test was based on a test developed by Broom ( 1986 ) and was only done when the sow was lying. T w o hundred millilitres of water were tipped onto the sow's back by remotely pulling a string which released a container positioned on a bar 1.5 m above the lying sow.
Observations and statistical analysis General behaviour Videotapes were analysed by recording the behaviour of the sow in the stall every 15 s in the 5-min period before and after stimulus presentation. The effect o f the stimuli on sow behaviour was analysed by comparing the behaviour of the sow in each 15 s scan after stimulus presentation with the equivalent scan before stimulus presentation. Thus the + 15 s scan was compared with the - 15 s scan, the + 30 s scan with the - 3 0 s scan, and so on, up to + 300 s versus - 300 s. If the behaviour was the same the sow scored 0, if it was different the sow scored 1. The total score for the 20 pairs of observations was used as a measure o f behaviour change following stimulus presentation. Scores were converted to proportions and then adequately transformed to normality with the angular transformation. A repeated measures ANOVA was done on each group o f stimuli, with stimulus type treated as a within-subjects factor. Differences between means within a group were compared using orthogonal a priori contrasts. U n t r a n s f o r m e d scores are shown in the results.
Posture Sow posture is an indicator o f whether a stimulus is attractive, aversive or neutral. In general, an aversive stimulus will result in a raised head, movement away and orientation away from the stimulus. An attractive stimulus will elicit head lowering and forward m o v e m e n t and orientation. Sow posture was scored by noting snout level, head position and orientation in each of the 15 s scans. Snout level was scored as 1 if the snout was below the level of the trough, 2 if it was above the trough and below the middle bar of the stall and 3 if it was above the middle bar. H e a d position was scored as 1 if the snout was in front of or over the trough, 2 if it was within 50 cm of the trough and 3 if it was further back than 50 cm from the trough. Orientation was scored
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as 1 if the sow faced forwards within a 45 ° arc, i.e. from 0 to 22.5 ° on either side, 2 if the sow faced to the side, i.e. from 22.5 ° to 67.5 °, and 3 if the sow faced away, i.e. greater than 67.5 °. In addition, any contacts with the stimulus, such as nosing, biting or licking were noted. Posture scores for snout level, head position and orientation were s u m m e d over the 20 observations before and after stimulus presentation and then the latter were subtracted from the former to give a total change in posture score. Scores for posture change were tested for normality and then the untransformed data were analysed by repeated measures analysis of variance within each group of stimuli, with type o f stimulus treated as a within-subjects factor. Differences between means within a group were compared using orthogonal a priori contrasts. The latency of the sow to stand in response to tactile tests was also recorded. Sows that did not stand were given the m a x i m u m score of 300 s. The data were transformed to c o m m o n logarithms and analysed by repeated measures analysis of variance. U n t r a n s f o r m e d means are given in the results. RESULTS
Effects of stimuli on behaviour The effect of the stimuli on general behaviour is summarised in Table 1. For the five stimulus groups, the coefficients of variation indicate that the most variable response was to tactile stimuli and the least variable to visual stimuli. There were no significant differences within the visual, olfactory and complex stimuli groups. For tactile stimuli, a priori contrasts showed no significant difference between the clip, in which the sow was standing for testing, and the other stimuli which required the sow to be lying. There was no significant difference when water was compared with rub, prod and slap, but a significant difference ( P < 0 . 0 1 ) when slap was compared with rub and prod. For auditory stimuli, comparisons of cap gun and buzzer versus squeal and grunt were not significant, but the buzzer elicited more change than the cap gun ( P < 0 . 0 5 ) , and there was no significant difference between the squeal and grunt.
Effects of stimuli on posture Visual stimuli The effect of visual stimuli on sow posture is summarised in Fig. 1 (a). All stimulus types caused sows to lift their snouts, but there was no significant difference between them. The stimuli had little effect on head position. Orientation was not influenced by the chime or ball, but sows were more likely to face forwards in response to the umbrella and novel rod. A priori contrasts
261
RESPONSE OF SOWSTO SENSORY STIMULI TABLE 1 Effect of stimulus presentation on behaviour Stimulus
Mean
S.E.
CV
P
Visual stimuli Umbrella Ball Chime Novel rod
11.6 11.1 11.1 11.2 12.9
0.6 1.4 1.3 1.3 1.1
32.5 48.8 44.3 44.2 32.5
0.52
Olfactory stimuli Eucalyptus oil Perfume Ammonia Acetic acid
11.8 13.1 12.5 11.7 9.7
0.7 1.2 1.3 1.2 1.6
44.9 36.1 39.0 41.2 63.3
0.34
Auditory stimuli Cap gun Buzzer Squeal Grunt
11.7 10.5 14.2 11.9 10.3
0.7 1.2 1.1 1.2 1.6
43.2 43.2 30.9 38.6 60.2
0.03
Tactile stimuli Rub Prod Slap Water Clip
11.6 10.5 8.0 15.3 14.2 9.8
0.9 1.9 2.1 1.3 2.2 1.4
64.9 68.4 102.6 32.5 60.5 60.5
0.01
Complex stimuli Human Food Novel food
11.7 10.7 11.9 12.4
0.8 1.6 1.3 1.2
46.5 59.5 42.2 37.9
0.73
Mean scores represent the number of scans in which behaviour following stimulus presentation had changed. Stimulus group means and significant differences within groups are also shown.
showed no significant difference when the moving stimulus, the chime, was compared with the stationary stimuli, the umbrella, ball and rod ( P > 0.05 ). The number of contacts with the stimulus in the first 30 s of exposure is shown in Fig. 2. Sows made fewer contacts with the chime (a moving stimulus) than the umbrella, ball and rod ( P < 0.01 ). There were no significant differences between the three stationary stimuli.
Olfactory stimuli Sows lifted their heads more in response to the aromatic odours, eucalyptus oil and perfume, than ammonia or acetic acid (P<0.05, Fig. 1 (b)). Head position and orientation were not affected by any of the odours. Many sows
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G.D. HUTSON ET AL (a)
Visual stimuli
(b)
Olfactory stimuli
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Fig. 1. Effect of novel stimuli on snout level ([]), head position ( [ ] ) and orientation ( [ ] ) of sows after stimulus presentation. Positive scores indicate lowering of the snout, movement of the head towards the front of the stall and orientation towards the stimulus. Negative scores indicate raising of the snout, m o v e m e n t towards the rear of the stall, and orientation away from the stimulus.
RESPONSE OF SOWSTO SENSORY STIMULI
263
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Fig. 2. M e a n n u m b e r o f contacts with visual stimuli in the 30-s period after stimulus presentation. Vertical bars indicate s t a n d a r d errors.
300 v .13
9
200
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Ammonia Acetic acid
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Fig. 3. M e a n latency of sows to rub in response to olfactory stimuli. The n u m b e r of sows rubbing a n d s t a n d a r d errors are also shown.
began to rub their flanks, heads or backs on the side of the stall in response to the odours. The number of sows rubbing and the latency to commence rubbing is shown in Fig. 3. More sows rubbed and commenced rubbing earlier in response to eucalyptus and perfume than to ammonia or acetic acid ( P < 0.001 ), but there was no difference ( P > 0.05 ) between eucalyptus and perfume, and between a m m o n i a and acid.
Auditory stimuli Sows tended to lift their heads in response to the cap gun and grunt, and lower their heads in response to the buzzer and squeal, but these differences
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were not significant (Fig. l ( c ) ) . The auditory stimuli influenced the head position of the sows with the buzzer and grunt causing sows to move to the rear of the stall and the cap gun and squeal to move forwards. A priori comparisons of physical versus biological sounds showed no significant differences between cap gun and buzzer versus squeal and grunt. However, the buzzer elicited a greater backward m o v e m e n t than the gun ( P < 0.01 ). There was no difference between the squeal and grunt. The orientation of the sows was not significantly influenced by the sounds ( P = 0.10).
Tactile stimuli Snout level and head position were not significantly affected by any of the tactile stimuli ( P > 0.05, Fig. 1 ( d ) ) . The clip had no effect on orientation, whereas all other stimuli caused the sows to face forwards ( P < 0 . 0 1 ) . The number of sows standing and the latency to stand in response to the four tests done on lying sows is shown in Fig. 4. A priori tests showed that sows stood more rapidly in response to the water compared with a rub, prod and slap ( P < 0 . 0 1 ) and more rapidly in response to a slap than a rub or prod ( P < 0.05 ). There was no difference ( P > 0.05 ) between a rub and a prod. All sows responded to the clip by attempting to shake it off. Of 15 sows, 14 succeeded, with a mean latency to removal of 53 s (S.E. 26.0).
Complex stimuli Snout level was significantly lowered by food compared with novel food and the human ( P < 0.001 ), but head position and orientation were not affected (Fig. 1 (e)). All sows ate all of the food, but only 3 out of 15 sows attempted to eat the novel food. None of the sows showed fear responses to300
v t-
200
O
¢-
100
._J
Rub
Prod
Slap
Water
Stimulus
Fig. 4. M e a n latency o f sows to stand in response to tactile stimuli. The n u m b e r o f sows standing a n d s t a n d a r d errors are also shown.
RESPONSE OF SOWS TO SENSORY STIMULI
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wards the h u m a n and 12 out of 15 sows made contact with the nose or mouth (mean 12.4 + 5.9 contacts). DISCUSSION The overall aim of these tests was to select one stimulus from each stimulus group for further evaluation of individual and genetic variation in responsiveness. Sows showed little response to the visual stimuli. They appeared to be least responsive to the moving visual stimulus, the revolving chime, and showed the strongest orientation response to the umbrella and rod. However, neither of these stimuli elicited fear responses as in other species (e.g. Jones, 1988), but were treated as objects to explore and make contact with the nose and mouth. The novel rod was selected as the visual stimulus. The sows showed very interesting responses to the olfactory stimuli. There was no response to a m m o n i a and acetic acid. This is a particularly surprising result as glacial acetic acid has a pungent and acrid smell to the h u m a n nose. Sows raised their heads in response to eucalyptus oil and perfume, which indicates that these compounds may be more aromatic and volatile. These odours also stimulated vigorous rubbing behaviour. The function of this response is unknown, although it may be related to marking behaviour. Eucalyptus oil was selected as the olfactory stimulus. The auditory stimuli had various effects. The short, sharp report of the cap gun had no observable effect. Movement and orientation towards this stimulus may have been directed towards the approaching and retreating human. The buzzer elicited more change in behaviour than the cap gun and caused sows to move to the rear of the stall. However, snout level and orientation were not affected. The grunt was selected as the auditory stimulus. Of the tactile stimuli presented to lying sows the slap and water were most effective in eliciting standing behaviour. The lack of response to rub and prod indicates that these sows are used to h u m a n handling and also may be insensitive to mild tactile stimulation. All sows responded to the clip by attempting to shake it off. The clip was selected as the tactile stimulus because it did not require the sow to be lying, and the response, latency to removal, could be easily recorded. Of the complex stimuli, the sows responded in a predictable manner to food, by immediately eating it. There was little response to the human, although there was variation in the number of contacts made. The response to novel food was startling and indicates that pigs have a strong food neophobia. Food neophobias are c o m m o n in a large number of mammals and are expressed as a hesitancy to eat novel or unfamiliar foods. However, many of these neophobias are related to taste (Hill, 1978) and there is an urgent need for further evaluation of this p h e n o m e n o n in pigs. The p h e n o m e n o n has broad implica-
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tions for commercial feeding of pigs, especially when there are changes in the form or appearance of a diet. The human was selected as the complex stimulus. In summary, after screening 20 potential novel stimuli we selected five stimuli for further evaluation: the novel rod, eucalyptus oil, playback of a sow grunting, a clip placed on the ear and exposure to a human. Future work will report on the responses of sows to these stimuli in a commercial situation and compare responsiveness to specific maternal responsiveness. ACKNOWLEDGEMENT
This study was funded by a grant from the Australian Pig Research and Development Council.
REFERENCES Broom, D.M., 1986. Responsiveness of stall-housed sows. Appl. Anim. Behav. Sci., 15:186 (abstract). Chapple, R.S. and Wodzicka-Tomaszewska, M., 1987. The learning behaviour of sheep when introduced to wheat. II. Social transmission of wheat feeding and the role of the senses. Appl. Anim. Behav. Sci., 18: 163-172. Cronin, G.M., 1985. The development and significance of abnormal stereotyped behaviours in tethered sows. Ph.D. Thesis, Agricultural University of Wageningen. Cronin, G.M. and Cropley, J.A., 1991. The effect of piglet stimuli on the posture changing behaviour of recently farrowed sows. Appl. Anim. Behav. Sci., 30: 167-172. Duncan, I.J.H. and Filshie, J.H., 1980. The use of radio telemetry devices to measure temperature and heart rate in domestic fowl. In: C.J. Amlaner and D.W. Macdonald (Editors), A Handbook on Biotelemetry and Radio Tracking. Pergamon, Oxford, pp. 579-588. Hemsworth, P.H., Barnett, J.L. and Hansen, C., 1986. The influence of handling by humans on the behaviour, reproduction and corticosteroids of male and female pigs. Appl. Anim. Behav. Sci., 15: 303-314. Hill, W.F., 1978. Effects of mere exposure on preferences in nonhuman mammals. Psychol. Bull., 85: 1177-1198. Hutson, G.D., Wilkinson, J.L. and Luxford, B.G., 1991. The response of lactating sows to tactile, visual and auditory stimuli associated with a model piglet. Appl. Anim. Behav. Sci., 32: 129-137. Hutson, G.D., Argent, M.F., Dickenson, L.G. and Luxford, B.G., 1992. The influence of parity and time since parturition on responsiveness of sows to a piglet distress call. Appl. Anim. Behav. Sci., 34:303-313. Jones, R.B., 1988. Repeatability of fear ranks among adult laying hens. Appl. Anim. Behav. Sci., 19: 297-304.
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The response of sows to novel visual, olfactory, auditory and tactile stimuli G.D. Hutson, L.G. Dickenson, J.L. Wilkinson and B.G. Luxford 1 School of Agriculture and Forestry, University of Melbourne, Parkville, Vic. 3052, Australia (Accepted 3 June 1992)
ABSTRACT Hutson, G.D., Dickenson, L.G., Wilkinson, J.L. and Luxford, B.G., 1993. The response of sows to novel visual, olfactory, auditory and tactile stimuli. AppL Anim. Behav. Sci., 35: 255-266. The responses of sows to 20 stimuli from five sensory categories were evaluated with the aim of selecting one stimulus from each category as a test of general environmental responsiveness. The visual stimuli evaluated were a novel rod, a hanging ball, a moving chime and an umbrella. The olfactory stimuli were eucalyptus oil, perfume, ammonia and glacial acetic acid. The auditory stimuli were the sound of a cap gun, a buzzer, playback of a piglet squeal and playback of a sow grunt. The tactile stimuli were a rub, a prod, a slap on the neck, a clip placed on the ear and water tipped on the back. The complex stimuli evaluated were response to a human, food and novel-coloured food. The effect of the stimuli was analysed by comparing changes in behaviour and posture of sows in 15-s scans for 5 min, before and after stimulus presentation. Sows showed little response to the visual stimuli; the umbrella and rod elicited more exploratory responses than the chime or ball. Sows ignored ammonia and glacial acetic acid, but responded to eucalyptus oil and perfume by raising their heads and rubbing their sides and backs on the side of the stall. Sows showed variable responses to the auditory stimuli; the buzzer elicited more movement away from the stimulus. Lying sows responded to the tactile stimuli by standing more rapidly in response to the water and a slap than to a rub or a prod. All sows responded to the clip by attempting to shake it off. Sows showed no fear responses towards the h u m a n and 12 out of 15 sows made frequent contacts. Sows showed a neophobic response to blue-coloured food and only three out of 15 sows attempted to eat it. The stimuli selected for further study of general environmental responsiveness were the novel rod, eucalyptus oil, playback of the sow grunt, the clip and exposure to a human.
INTRODUCTION
In a previous study of maternal responsiveness in sows Hutson et al. ( 1991 ) found that recently farrowed sows did not respond to visual and tactile stimuli associated with a model piglet inserted underneath the udder, but did respond to an auditory stimulus, playback of a piglet squeal. The response tended Correspondence to: G.D. Hutson, School o f Agriculture a n d Forestry, University o f Melbourne, Parkville, Vic. 3052, Australia. tPresent address: Bunge Meat Industries, P.O. Box 78, Corowa, N.S.W. 2646, Australia.
© 1993 Elsevier Science Publishers B.V. All rights reserved 0 1 6 8 - 1 5 9 1 / 9 3 / $ 0 5 . 0 0
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to be all or nothing, with sows either sitting or standing in response to the squeal, or ignoring it. There was significant individual variation in responsiveness, with about 60% of individuals responding. A similar proportion of responders to squeal playback has been reported by Cronin and Cropley ( 1991 ). It is possible that the failure of some individuals to respond to playback of a loud piglet distress call may not be a function of the stimulus, but may reflect underlying genetic variation. An alternative explanation for the lack of maternal responsiveness of confined sows is that general responsiveness may have been modified in some way by the intensive environment. Broom (1986) reported that stall-housed sows were less responsive to 200 ml of water tipped on their backs than grouphoused sows. However, stall-housed sows were still very responsive to cues associated with feeding. Thus it is quite conceivable that some responses of intensively housed sows have been attenuated by the immediate and past environments and others have not. The aim of this study was to select appropriate stimuli for evaluating general environmental responsiveness in the sow, with the long term goal of measuring genetic variation in this trait. When coupled with the test of maternal responsiveness developed in previous studies (Hutson et al., 1991, 1992) we would then be able to determine whether any genetic change in maternal responsiveness was independent of any shift in general responsiveness. We evaluated a range of 20 potential test stimuli, broadly grouped into five sensory categories: visual, olfactory, auditory, tactile and complex stimuli. The aim was to screen these stimuli and select one from each group for inclusion in the test of general environmental responsiveness. Sow responses were recorded for 5 min before and after stimulus presentation. Visual stimuli evaluated were a novel rod, a hanging ball, a moving chime and an umbrella. Olfactory stimuli evaluated were eucalyptus oil, perfume, ammonia and glacial acetic acid. Auditory stimuli were the sound of a cap gun, a buzzer, playback of a piglet squeal and playback of a sow grunt. Tactile stimuli were a rub, a prod, a slap, a clip placed on the ear and water tipped on the back. Complex stimuli evaluated were response to a human, food and novel food. ANIMALS, MATERIALS A N D M E T H O D S
Animals Sixteen sows (Large White or Large White × Landrace ) from the University of Melbourne Pig Centre herd, Mt. Derrimut, were used in the tests. Parities ranged from 2 to 9 with a median of 4. The sows were normally necktethered in partial stalls on a concrete floor in a dry sow house accommodating 80 sows. All tests were done on pregnant sows between 30 and 60 days of
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gestation. The tests were done with the sow in her normal stall. One sow died before the completion o f testing and was excluded from the analysis.
Test procedure We tested the response o f the sows to the stimuli in blocks of four sows. Eight tests were done per day, at 10: 00, 11 : 00, 12: 00, 13 : 00, 14: 00, 15: 00, 16:00 and 17:00 h. Each sow was tested twice per day, once between 10:00 and 13:00 h (a.m. tests) and once between 14:00 and 17:00 h (p.m. tests). Stimuli 1-10 were used in a.m. tests and Stimuli 11-20 were used in p.m. tests. This division was adopted as some tests required the sow to be lying down, which was m o r e probable in the afternoon. The order of stimulus presentation was randomised for each sow for a.m. and p.m. tests. A video camera m o u n t e d on a tripod was placed in the aisle in front of the sow about 3 m away. The behaviour o f the sow was then videotaped for 5 min before and after presentation o f the stimulus. Twenty test stimuli, grouped into five sensory categories, were evaluated. Test stimuli were selected on the grounds that they were novel, or had been used successfully by other researchers. The specific procedures associated for each test were:
Visual stimuli (1) Umbrella. The experimenter approached the pig's stall, tapped the middle bar on the front o f the stall with the tip o f the umbrella if the sow was not looking forwards, and then unfolded the black umbrella at a distance of 10 cm from the bar of the stall. The umbrella was spring loaded so that unfolding was automatic and rapid. After 30 s the umbrella was folded and the experim e n t e r retreated. An umbrella was used because a rapidly expanding visual stimulus is alarming to m a n y animals. For example, Duncan and Filshie (1980) found that an inflating balloon was a potent stimulus for eliciting avoidance and escape behaviour in the domestic fowl. (2) Ball on a string. A yellow plastic ball, 20 cm in diameter was suspended on a string and pulley 2 m above the sow's trough, 1 h before stimulus presentation. At the m o m e n t o f stimulus presentation the experimenter lowered the ball to a set position between the b o t t o m and middle front bars o f the stall, about 40 cm above floor level. The ball stayed in this position for the duration of the test. (3) Revolving chime. A 24-cm diameter revolving multicoloured toy chime, m o u n t e d on a wooden stand, was placed 20 cm in front of the sow's stall. The chime was left in this position for the duration of the test. (4) Novel rod. A novel rod, similar to that used by Jones ( 1988 ) in tests of fear in laying hens was used. The 36 cm × 6-cm steel rod was welded to a 15cm base and covered with six differently coloured bands of plastic tape (blue,
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white, red, yellow, black and green). The rod was placed upright in the food trough at the front of the sow's stall.
Olfactory stimuli Responses to olfactory stimuli were tested by impregnating a cotton wool swab with the odour/liquid. The swab was placed in a plastic container, carried to the stall, and then tipped into the food trough. Odours and volumes used were: (5) Eucalyptus oil--ten drops. (6) Perfume--ten squirts from an atomiser of 'Le Cardon, No. 7, Paris'. (7) Cloudy ammonia--2.5 ml of domestic cleaning a m m o n i a (3.7% NH4OH ). (8) Glacial acetic acid--2.5 ml. Glacial acetic acid was selected because of its use as a test for olfaction. Sheep will show a violent head withdrawal to cotton wool soaked in glacial acetic acid held 6 cm from the nose (Chapple and Wodzicka-Tomaszewska, 1987 ).
Complex stimuli (9) Food. Five grammes of pellets were tipped from a plastic container into the food trough from a height of 30 cm. (10) Novel food. Five grammes of pellets which had been dyed blue with food dye were tipped into the food trough. (I 1) Human. The experimenter stood in front of the stall, with feet touching the base of the trough. An open palm was held 10 cm above and in line with the middle bar of the front of the stall for 5 min. Responses to humans have been a key component of the methods developed by Hemsworth et al. ( 1986 ) to assess the effects of handling on behaviour and welfare in pigs.
Auditory stimuli (12) Capgun. The experimenter stood with feet against the trough and fired a toy cap gun 30 cm above the sow's head. The experimenter then retreated. (13) Buzzer. An electric buzzer, m o u n t e d on a wooden stand, was placed 20 cm in front of the sow's stall. The buzzer was operated remotely for 30 s. (14) Piglet squeal. A speaker was placed in position 20 cm from the front of the stall and a recorded piglet squeal was played back remotely for 30 s. (15) Sow grunt. As for Test 14, but a recorded sow grunt was played back for 30 s.
Tactile stimuli The rub, prod and slap tests were based on the slap test used by Cronin ( 1985 ) to measure sow attentiveness after naloxone treatment. (16) Rub. This test was only carried out if the sow was lying. The experimenter stood in front of the stall with feet against the trough, and rubbed the
RESPONSE OF SOWS TO SENSORY STIMULI
2 59
sow's neck, over a distance o f 15 cm, once every 10 s until the sow stood. The experimenter then retreated for the remainder o f the test. (17) Prod. As for Test 16, except the experimenter p r o d d e d the sow firmly in the neck with a r o u n d e d 10 cm length o f 15 m m diameter w o o d e n dowel, once every 10 s until the sow stood. (18) Slap. As for Test 16, except the experimenter slapped the sow firmly with a fiat palm, once every 10 s, until the sow stood. (19) Clip. The experimenter placed a spring-action "Bulldog' paper clip (65 m m long) on the middle o f the leading edge of the sow's left ear. (20) Water. This test was based on a test developed by Broom ( 1986 ) and was only done when the sow was lying. T w o hundred millilitres of water were tipped onto the sow's back by remotely pulling a string which released a container positioned on a bar 1.5 m above the lying sow.
Observations and statistical analysis General behaviour Videotapes were analysed by recording the behaviour of the sow in the stall every 15 s in the 5-min period before and after stimulus presentation. The effect o f the stimuli on sow behaviour was analysed by comparing the behaviour of the sow in each 15 s scan after stimulus presentation with the equivalent scan before stimulus presentation. Thus the + 15 s scan was compared with the - 15 s scan, the + 30 s scan with the - 3 0 s scan, and so on, up to + 300 s versus - 300 s. If the behaviour was the same the sow scored 0, if it was different the sow scored 1. The total score for the 20 pairs of observations was used as a measure o f behaviour change following stimulus presentation. Scores were converted to proportions and then adequately transformed to normality with the angular transformation. A repeated measures ANOVA was done on each group o f stimuli, with stimulus type treated as a within-subjects factor. Differences between means within a group were compared using orthogonal a priori contrasts. U n t r a n s f o r m e d scores are shown in the results.
Posture Sow posture is an indicator o f whether a stimulus is attractive, aversive or neutral. In general, an aversive stimulus will result in a raised head, movement away and orientation away from the stimulus. An attractive stimulus will elicit head lowering and forward m o v e m e n t and orientation. Sow posture was scored by noting snout level, head position and orientation in each of the 15 s scans. Snout level was scored as 1 if the snout was below the level of the trough, 2 if it was above the trough and below the middle bar of the stall and 3 if it was above the middle bar. H e a d position was scored as 1 if the snout was in front of or over the trough, 2 if it was within 50 cm of the trough and 3 if it was further back than 50 cm from the trough. Orientation was scored
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as 1 if the sow faced forwards within a 45 ° arc, i.e. from 0 to 22.5 ° on either side, 2 if the sow faced to the side, i.e. from 22.5 ° to 67.5 °, and 3 if the sow faced away, i.e. greater than 67.5 °. In addition, any contacts with the stimulus, such as nosing, biting or licking were noted. Posture scores for snout level, head position and orientation were s u m m e d over the 20 observations before and after stimulus presentation and then the latter were subtracted from the former to give a total change in posture score. Scores for posture change were tested for normality and then the untransformed data were analysed by repeated measures analysis of variance within each group of stimuli, with type o f stimulus treated as a within-subjects factor. Differences between means within a group were compared using orthogonal a priori contrasts. The latency of the sow to stand in response to tactile tests was also recorded. Sows that did not stand were given the m a x i m u m score of 300 s. The data were transformed to c o m m o n logarithms and analysed by repeated measures analysis of variance. U n t r a n s f o r m e d means are given in the results. RESULTS
Effects of stimuli on behaviour The effect of the stimuli on general behaviour is summarised in Table 1. For the five stimulus groups, the coefficients of variation indicate that the most variable response was to tactile stimuli and the least variable to visual stimuli. There were no significant differences within the visual, olfactory and complex stimuli groups. For tactile stimuli, a priori contrasts showed no significant difference between the clip, in which the sow was standing for testing, and the other stimuli which required the sow to be lying. There was no significant difference when water was compared with rub, prod and slap, but a significant difference ( P < 0 . 0 1 ) when slap was compared with rub and prod. For auditory stimuli, comparisons of cap gun and buzzer versus squeal and grunt were not significant, but the buzzer elicited more change than the cap gun ( P < 0 . 0 5 ) , and there was no significant difference between the squeal and grunt.
Effects of stimuli on posture Visual stimuli The effect of visual stimuli on sow posture is summarised in Fig. 1 (a). All stimulus types caused sows to lift their snouts, but there was no significant difference between them. The stimuli had little effect on head position. Orientation was not influenced by the chime or ball, but sows were more likely to face forwards in response to the umbrella and novel rod. A priori contrasts
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RESPONSE OF SOWSTO SENSORY STIMULI TABLE 1 Effect of stimulus presentation on behaviour Stimulus
Mean
S.E.
CV
P
Visual stimuli Umbrella Ball Chime Novel rod
11.6 11.1 11.1 11.2 12.9
0.6 1.4 1.3 1.3 1.1
32.5 48.8 44.3 44.2 32.5
0.52
Olfactory stimuli Eucalyptus oil Perfume Ammonia Acetic acid
11.8 13.1 12.5 11.7 9.7
0.7 1.2 1.3 1.2 1.6
44.9 36.1 39.0 41.2 63.3
0.34
Auditory stimuli Cap gun Buzzer Squeal Grunt
11.7 10.5 14.2 11.9 10.3
0.7 1.2 1.1 1.2 1.6
43.2 43.2 30.9 38.6 60.2
0.03
Tactile stimuli Rub Prod Slap Water Clip
11.6 10.5 8.0 15.3 14.2 9.8
0.9 1.9 2.1 1.3 2.2 1.4
64.9 68.4 102.6 32.5 60.5 60.5
0.01
Complex stimuli Human Food Novel food
11.7 10.7 11.9 12.4
0.8 1.6 1.3 1.2
46.5 59.5 42.2 37.9
0.73
Mean scores represent the number of scans in which behaviour following stimulus presentation had changed. Stimulus group means and significant differences within groups are also shown.
showed no significant difference when the moving stimulus, the chime, was compared with the stationary stimuli, the umbrella, ball and rod ( P > 0.05 ). The number of contacts with the stimulus in the first 30 s of exposure is shown in Fig. 2. Sows made fewer contacts with the chime (a moving stimulus) than the umbrella, ball and rod ( P < 0.01 ). There were no significant differences between the three stationary stimuli.
Olfactory stimuli Sows lifted their heads more in response to the aromatic odours, eucalyptus oil and perfume, than ammonia or acetic acid (P<0.05, Fig. 1 (b)). Head position and orientation were not affected by any of the odours. Many sows
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G.D. HUTSON ET AL (a)
Visual stimuli
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Fig. 1. Effect of novel stimuli on snout level ([]), head position ( [ ] ) and orientation ( [ ] ) of sows after stimulus presentation. Positive scores indicate lowering of the snout, movement of the head towards the front of the stall and orientation towards the stimulus. Negative scores indicate raising of the snout, m o v e m e n t towards the rear of the stall, and orientation away from the stimulus.
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300 v .13
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Fig. 3. M e a n latency of sows to rub in response to olfactory stimuli. The n u m b e r of sows rubbing a n d s t a n d a r d errors are also shown.
began to rub their flanks, heads or backs on the side of the stall in response to the odours. The number of sows rubbing and the latency to commence rubbing is shown in Fig. 3. More sows rubbed and commenced rubbing earlier in response to eucalyptus and perfume than to ammonia or acetic acid ( P < 0.001 ), but there was no difference ( P > 0.05 ) between eucalyptus and perfume, and between a m m o n i a and acid.
Auditory stimuli Sows tended to lift their heads in response to the cap gun and grunt, and lower their heads in response to the buzzer and squeal, but these differences
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were not significant (Fig. l ( c ) ) . The auditory stimuli influenced the head position of the sows with the buzzer and grunt causing sows to move to the rear of the stall and the cap gun and squeal to move forwards. A priori comparisons of physical versus biological sounds showed no significant differences between cap gun and buzzer versus squeal and grunt. However, the buzzer elicited a greater backward m o v e m e n t than the gun ( P < 0.01 ). There was no difference between the squeal and grunt. The orientation of the sows was not significantly influenced by the sounds ( P = 0.10).
Tactile stimuli Snout level and head position were not significantly affected by any of the tactile stimuli ( P > 0.05, Fig. 1 ( d ) ) . The clip had no effect on orientation, whereas all other stimuli caused the sows to face forwards ( P < 0 . 0 1 ) . The number of sows standing and the latency to stand in response to the four tests done on lying sows is shown in Fig. 4. A priori tests showed that sows stood more rapidly in response to the water compared with a rub, prod and slap ( P < 0 . 0 1 ) and more rapidly in response to a slap than a rub or prod ( P < 0.05 ). There was no difference ( P > 0.05 ) between a rub and a prod. All sows responded to the clip by attempting to shake it off. Of 15 sows, 14 succeeded, with a mean latency to removal of 53 s (S.E. 26.0).
Complex stimuli Snout level was significantly lowered by food compared with novel food and the human ( P < 0.001 ), but head position and orientation were not affected (Fig. 1 (e)). All sows ate all of the food, but only 3 out of 15 sows attempted to eat the novel food. None of the sows showed fear responses to300
v t-
200
O
¢-
100
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Rub
Prod
Slap
Water
Stimulus
Fig. 4. M e a n latency o f sows to stand in response to tactile stimuli. The n u m b e r o f sows standing a n d s t a n d a r d errors are also shown.
RESPONSE OF SOWS TO SENSORY STIMULI
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wards the h u m a n and 12 out of 15 sows made contact with the nose or mouth (mean 12.4 + 5.9 contacts). DISCUSSION The overall aim of these tests was to select one stimulus from each stimulus group for further evaluation of individual and genetic variation in responsiveness. Sows showed little response to the visual stimuli. They appeared to be least responsive to the moving visual stimulus, the revolving chime, and showed the strongest orientation response to the umbrella and rod. However, neither of these stimuli elicited fear responses as in other species (e.g. Jones, 1988), but were treated as objects to explore and make contact with the nose and mouth. The novel rod was selected as the visual stimulus. The sows showed very interesting responses to the olfactory stimuli. There was no response to a m m o n i a and acetic acid. This is a particularly surprising result as glacial acetic acid has a pungent and acrid smell to the h u m a n nose. Sows raised their heads in response to eucalyptus oil and perfume, which indicates that these compounds may be more aromatic and volatile. These odours also stimulated vigorous rubbing behaviour. The function of this response is unknown, although it may be related to marking behaviour. Eucalyptus oil was selected as the olfactory stimulus. The auditory stimuli had various effects. The short, sharp report of the cap gun had no observable effect. Movement and orientation towards this stimulus may have been directed towards the approaching and retreating human. The buzzer elicited more change in behaviour than the cap gun and caused sows to move to the rear of the stall. However, snout level and orientation were not affected. The grunt was selected as the auditory stimulus. Of the tactile stimuli presented to lying sows the slap and water were most effective in eliciting standing behaviour. The lack of response to rub and prod indicates that these sows are used to h u m a n handling and also may be insensitive to mild tactile stimulation. All sows responded to the clip by attempting to shake it off. The clip was selected as the tactile stimulus because it did not require the sow to be lying, and the response, latency to removal, could be easily recorded. Of the complex stimuli, the sows responded in a predictable manner to food, by immediately eating it. There was little response to the human, although there was variation in the number of contacts made. The response to novel food was startling and indicates that pigs have a strong food neophobia. Food neophobias are c o m m o n in a large number of mammals and are expressed as a hesitancy to eat novel or unfamiliar foods. However, many of these neophobias are related to taste (Hill, 1978) and there is an urgent need for further evaluation of this p h e n o m e n o n in pigs. The p h e n o m e n o n has broad implica-
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tions for commercial feeding of pigs, especially when there are changes in the form or appearance of a diet. The human was selected as the complex stimulus. In summary, after screening 20 potential novel stimuli we selected five stimuli for further evaluation: the novel rod, eucalyptus oil, playback of a sow grunting, a clip placed on the ear and exposure to a human. Future work will report on the responses of sows to these stimuli in a commercial situation and compare responsiveness to specific maternal responsiveness. ACKNOWLEDGEMENT
This study was funded by a grant from the Australian Pig Research and Development Council.
REFERENCES Broom, D.M., 1986. Responsiveness of stall-housed sows. Appl. Anim. Behav. Sci., 15:186 (abstract). Chapple, R.S. and Wodzicka-Tomaszewska, M., 1987. The learning behaviour of sheep when introduced to wheat. II. Social transmission of wheat feeding and the role of the senses. Appl. Anim. Behav. Sci., 18: 163-172. Cronin, G.M., 1985. The development and significance of abnormal stereotyped behaviours in tethered sows. Ph.D. Thesis, Agricultural University of Wageningen. Cronin, G.M. and Cropley, J.A., 1991. The effect of piglet stimuli on the posture changing behaviour of recently farrowed sows. Appl. Anim. Behav. Sci., 30: 167-172. Duncan, I.J.H. and Filshie, J.H., 1980. The use of radio telemetry devices to measure temperature and heart rate in domestic fowl. In: C.J. Amlaner and D.W. Macdonald (Editors), A Handbook on Biotelemetry and Radio Tracking. Pergamon, Oxford, pp. 579-588. Hemsworth, P.H., Barnett, J.L. and Hansen, C., 1986. The influence of handling by humans on the behaviour, reproduction and corticosteroids of male and female pigs. Appl. Anim. Behav. Sci., 15: 303-314. Hill, W.F., 1978. Effects of mere exposure on preferences in nonhuman mammals. Psychol. Bull., 85: 1177-1198. Hutson, G.D., Wilkinson, J.L. and Luxford, B.G., 1991. The response of lactating sows to tactile, visual and auditory stimuli associated with a model piglet. Appl. Anim. Behav. Sci., 32: 129-137. Hutson, G.D., Argent, M.F., Dickenson, L.G. and Luxford, B.G., 1992. The influence of parity and time since parturition on responsiveness of sows to a piglet distress call. Appl. Anim. Behav. Sci., 34:303-313. Jones, R.B., 1988. Repeatability of fear ranks among adult laying hens. Appl. Anim. Behav. Sci., 19: 297-304.