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Behavioural responses of dairy cows toward novel stimuli presented in the home environment
Applied Animal Behaviour Science 89 (2004) 27–40
Behavioural responses of dairy cows toward novel stimuli presented in the home environment Mette S. Herskin a,∗ , Anne-Marie Kristensen b , Lene Munksgaard a a
Department of Animal Health and Welfare, Danish Institute of Agricultural Sciences, Research Centre Foulum, P.O. Box 50, 8830 Tjele, Denmark b Department of Zoology, Institute of Biological Sciences, Building 135, University of Aarhus, 8000 Aarhus C, Denmark Accepted 22 April 2004
Abstract Several tests of behavioural and physiological responses toward novel stimuli are used in the study of stress and adaptability in cattle. The majority of them, however, are characterised by a relatively high degree of situational novelty and stimulus complexity. In the present experiment we examined behavioural responses of dairy cows toward novel stimuli presented in the home environment with minimal situational novelty, and investigated whether any consistency could be found across responses toward different novel stimuli. Four different stimuli were presented: usual food (30 min provision of 8 kg total mixed ration); novel food (30 min provision of 5 kg of carrots); novel object (30 min exposure to a white plastic container) and an unfamiliar person (5 min exposure to person dressed in hooded white overall). Sixteen Danish Friesian cows kept in tie-stalls were used, and one stimulus presented each day in a balanced order according to a Latin Square design. The presentations of novel food or a novel object resulted in several comparable variables, and a comparison of the responses showed that the novel food induced increased duration and frequency of sniffing (P < 0.05 for both), increased self-grooming (P < 0.01) as well as a longer duration of standing (P < 0.05) compared with the novel object. Responses toward the unfamiliar person could only be compared with responses toward the other novel stimuli for three variables. Here, the unfamiliar person induced a higher frequency of sniffing than the novel object (P < 0.01). These results suggest that dairy cows show increased behavioural responses characterised by increased exploration, arousal as well as behavioural conflict when exposed to novel food or an unfamiliar person compared with a novel object. ∗
Corresponding author. Tel.: +45-89-99-13-28; fax: +45-89-99-15-00. E-mail address: [email protected] (M.S. Herskin). 0168-1591/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2004.06.006
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Correlations between responses toward the different novel stimuli were low and non-significant. Thus, no evidence for consistent inter-test responses across the novel stimuli presented in the home environment were found. © 2004 Elsevier B.V. All rights reserved. Keywords: Novelty; Behavioural test; Cattle; Food; Fear; Neophobia
1. Introduction During the production cycle, dairy cows in intensive production systems are exposed to various challenging events including novel stimuli (e.g., handlers, food, group-mates). The welfare of an individual animal depends on the ability to cope with environmental challenges (Broom, 1988). Novelty is generally associated with negative emotions (Gray, 1987; Boissy, 1995), however, individual behavioural and physiological responses toward challenging events can be very variable (Manteca and Deag, 1993). If individual emotional reactivity is consistent across different challenging events, highly reactive animals may experience more fear when subjected to novel management routines, regrouping, etc. In cattle, however, there are conflicting reports on whether individual emotional reactivity is consistent across different challenging events as described by Boissy and Bouissou (1995) or whether responses depend on the challenging event in question as suggested by Schrader (2002) and Van Reenen et al. (2004). Several tests of behavioural and physiological responses toward novel stimuli have been used in the study of stress and adaptability in cattle (e.g., exposure to a novel arena (Boissy and Bouissou, 1995; Munksgaard and Simonsen, 1996), a novel object (Hemsworth et al., 1996; Schrader, 2002) or a novel person (Hemsworth et al., 1996; Munksgaard et al., 1997). Typically, behavioural tests of responses toward novel stimuli are standardised by the use of an arena, even though the stimulus in question is not the arena itself, but a person (Hemsworth et al., 1996), an object (Hemsworth et al., 1996) or even food (Boissy and Bouissou, 1988). As a consequence, the responses of the animals are affected by both the stimulus in question as well as situational factors (Manteca and Deag, 1993). Interpretation of responses in terms of stress and emotion is further complicated by the fact that the animals are subjected to handling and social isolation during testing (Le Neindre, 1989; Munksgaard and Jensen, 1996; Hopster, 1998). Separation of an individual cow from its group-mates induces stress responses (Boissy and Le Neindre, 1990) with a high degree of individual variation (Hopster et al., 1998). Using social isolation in an arena during testing, therefore, provokes behavioural responses, where the specific effects of each element of the test situation are (1) very difficult to separate from each other; and (2) varies considerably between individuals. Furthermore, Munksgaard et al. (1997) found no relation between individual behavioural responses of dairy cows when presented with an unfamiliar person in the home or a novel environment. Thus, responses to specific stimuli in a novel environment may not reflect the responses of the animals in their home environment. At present time, the information about behavioural responses toward novel stimuli presented in the home environment is sparse, mainly because individual testing of animals kept
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in groups might be confounded by the behaviour of group-mates (Veissier and Le Neindre, 1992). There has, however, been developed behavioural tests based on the approach behaviour of dairy cows presented with a human in the home environment (e.g., Munksgaard et al., 1997; Munksgaard et al., 2001). Furthermore, we have recently presented data on novel food testing in cattle kept in tie-stalls, suggesting that the use of food as a novel stimulus permits individual testing in a home environment, where the animals have limited social contact and are not handled during testing (Herskin and Munksgaard, 2000; Herskin et al., 2003a,b). The use of behavioural tests like these for the evaluation of emotional reactivity allows a marked reduction in the situational complexity, compared with the majority of the earlier tests of emotional reactivity in dairy cattle (e.g., Boissy and Bouissou, 1995; Hopster, 1998; Van Reenen et al., 2004). In the present paper dairy cows in their home environment were exposed to three different novel stimuli in order to: (1) compare behavioural responses toward novel food, a novel object and an unfamiliar person; and (2) investigate whether any inter-test consistency could be found across behavioural responses toward presentations of novel stimuli in the home environment.
2. Materials and methods 2.1. Animals, housing and feeding Sixteen Danish Friesian cows from the resident herd at Research Centre Foulum were used. All cows were in their first lactation 122 ± 15 days (mean ± S.E.) post partum. The cows were tethered with neck-bar ties in individual stalls measuring 180 cm × 120 cm on mats of hard rubber material and with chopped straw added daily. Feeding troughs in front of the cows were separated from neighbouring stalls by a 70 cm × 70 cm wooden partition. Experimental cows were never placed next to each other, and none of the cows had any experience with carrots, white plastic jars, the test-person or the clothing of the test-person before testing. The cows were fed a total mixed ration consisting of (% dry matter): 22 grass silage, 14 beet molasses, 12 barley, 33 wheat whole crop, 18 concentrates and 1 minerals. Feeding took place daily at 09:30 h from a fodder truck making the same route through the barn every day. Between 08:30 and 09:00 h all feeding troughs were emptied and all experimental cows had no access to food for at least 45 min before testing. 2.2. Experimental design Eight of the cows were subjected to one of the four different stimuli on four subsequent days in a balanced order according to a Latin Square design (Martin and Bateson, 1993). This was repeated the following week with the remaining eight cows. The experimental cows were kept in two rows in the barn to ensure that the unfamiliar person, who started testing in one end of the barn, did not need to walk in front of cows not yet tested.
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2.3. Types of stimuli 2.3.1. Provision of usual food At 09:45 h all experimental cows were standing. The fodder truck fed usual food to the non-experimental cows. Immediately after the fodder truck had passed each experimental cow, a person dressed like the usual caretakers emptied 8 kg of usual food into the cleaned feeding troughs from a basket made of orange plastic. The behaviour of the cows was video recorded in real time for the following 30 min. The videotapes were analysed by focal sampling and continuous recording (Martin and Bateson, 1993). An ethogram of the recorded behaviour is shown in Table 1. 2.3.2. Novel food Five kilograms of washed carrots without tops were used as novel food. During the novel food exposure, all procedures were similar to the provision of usual food. 2.3.3. Novel object A white plastic container measuring 35 cm × 25 cm × 10 cm filled with 800 g sand was used as novel object. In order to introduce the novel object without human presence, the container was fixed to a rope and placed on a bar above the experimental cow (but not in her field of vision) 23 h before the stimulus presentation. At 09:00 h when all experimental cows were standing, the container was lowered from the stall of the neighbouring cow and placed on the edge of the feeding trough in front of the experimental cow. The rope was tied to prevent the container from overturning. The behaviour of the experimental cow was video recorded in real time for 30 min before removal of the container. The videotapes were analysed by focal sampling and continuous recording (Martin and Bateson, 1993). An ethogram of the recorded behaviour is shown in Table 1. 2.3.4. Unfamiliar person The female test-person (height 1.60 m; weight 55 kg) was dressed in a hooded white overall and kept the hands hidden inside the sleeves. The person stood motionless in front of the cow at the edge of the feeding trough for 5 min. An observer dressed like the usual caretakers, was placed behind the test-person about two stalls away, making direct observations. The distance between the cow and the test-person was divided into scores according to Munksgaard et al. (1997) (Table 2) and registered by direct scanning (Martin and Bateson, 1993) every fifth second. 2.4. Variables 2.4.1. Provision of usual and novel food The following variables were calculated from the food exposures: (1) latency to sniff the food (s); (2) duration of sniffing/min of food exposure (s); (3) frequency of sniffing food/min of exposure; (4) latency to eat (s); (5) duration of eating/min of food exposure (s); (6) frequency of eating/min of food exposure; (7) duration of being away from food/min of exposure (s); (8) frequency of being away from food/min of exposure; (9) duration
Behavioural parameter Body posture States based on increasing distance between the animal and the stimulus
Definition Standing Lying Eat food/touch object Sniff stimulus
Head away
Maximum distance
Events
Self-grooming
Interaction with neighbour
Usual/novel food
Novel object
The cow is chewing/licking the food. Intervals of <10 s were ignored. The cow is not eating. The muzzle touches the food. Intervals of <3 s were ignored. The head is kept above the tie-bar and the chain is loose. Not chewing or self-grooming. Includes being at maximum distance. The cow maintains the maximum distance to the stimulus by pulling the chain backwards. Not chewing or self-grooming. Licking any part of the body or scratching body against the fixtures of the stall. At least one of the neighbouring cows has at least the muzzle inside the stall of the experimental cow or vice versa.
The cow touches the novel object or the rope. Intervals of <10 s were ignored. The distance between muzzle and object is no more than the width of the muzzle. If touching, only with the outer part of the muzzle. Intervals of <3 s were ignored.
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Table 1 Ethogram of the behaviour recorded from video tape during 30 min after provision of the usual food, the novel food or the novel object
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Table 2 Categories used to score the distance between the test-person and the experimental cow during the exposure to the unfamiliar person (adapted from Munksgaard et al., 1997) Score
Definition
1 2 3 4 5 6
Physical contact between the cow and the test-person. The muzzle of the cow is closer to the person than the horizontal tie-bar. The muzzle is above or below the horizontal tie-bar. The muzzle is behind the horizontal tie-bar. The head is behind the horizontal tie-bar, facing forward, and the chain is tight. As score 5, but with the head turned to the rear.
of standing/min of food exposure; (10) latency to perform self-grooming (s); and (11) frequency of self-grooming/min of food exposure. 2.4.2. Novel object The following variables were calculated from the exposure to the novel object: (1) latency to sniff the object (s); (2) duration of sniffing object/min of exposure (s); (3) frequency of sniffing object/min of exposure; (4) duration of being away from the object/min of exposure (s); (5) frequency of being away from the object/min of exposure; (6) duration of standing/min of object exposure (s); (7) latency to perform self-grooming (s); and (8) frequency of self-grooming behaviour/min of object exposure. 2.4.3. Unfamiliar person The following variables were calculated from the scoring of distance between the testperson and the experimental cow: (1) latency to physical contact (score 1) (s); (2) duration of physical contact = number of intervals × 5 s; (3) frequency of physical contact; (4) mean score during the 5 min test; and (5) maximum score during the 5 min test. 2.5. Statistical analysis Four behavioural variables (lying down, head far away, touching object and interaction with neighbour) had too little representation in the data and were excluded. 2.5.1. Continuous variables The following variables: frequency of sniffing, duration of sniffing, frequency of eating, frequency of head away, frequency of self-grooming and duration of standing were subjected to analysis of variance using the Mixed procedure of SAS (Littell et al., 1996). The basic model included type of stimuli and order of type of stimuli as fixed effects. Time since calving was included as a covariate if P < 0.05. Cow identity, week number (1, 2) and day of the week (1–4) were included as random factors. Each cow was used as the experimental unit and the results of the statistical analysis are given by means ± S.E. as well as F(dftreatment , dferror ) and the P-value. Duration of sniffing and the frequency of eating, sniffing and self-grooming were transformed to square root before analysis in order to approximate a normal distribution and homogeneity of variances. The duration of eating novel food and the duration of head away
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from novel food , however, did not show homogeneity of variances and were analysed using the non-parametric paired t-test (SigmaStat, Jandel Scientific Inc.© ). Results are then presented as means ± S.E., given P-values. In order to compare the behavioural responses toward the novel food and the novel object with the responses toward the unfamiliar person, three common variables were calculated from the three stimuli presentations: (1) duration of sniffing during the initial 5 min of exposure to the novel food or the novel object, and the number of intervals with score 1 × 5 s when confronted with the unfamiliar person; (2) frequency of sniffing during the initial 5 min of exposure to the novel food or the novel object, and the number of intervals with score 1 when confronted with the unfamiliar person; and (3) latency to sniff the novel stimulus. These variables were compared using one-way repeated measures ANOVA (SigmaStat, Jandel Scientific Inc.©). 2.5.2. Censored latencies The latencies to eat, sniff and self-groom were regarded as censored variables (Kleinbaum, 1996) and analysed using the non-parametric life test for survival data (SAS Institute, 1996). The results are presented as medians, total range and P-value. 2.5.3. Individual responses toward novel stimuli Possible relations between the responses toward the three novel stimuli were analysed using non-parametric Spearman rank correlations (SAS Institute, 1996). 2.5.4. Temporal development in the behavioural responses toward novel stimuli In order to evaluate whether the behavioural responses continued during the whole exposure time or ceased earlier, the following variables were chosen as key variables: duration of being away, sniffing and eating as well as frequency of being away, sniffing and selfgrooming. For each variable, the behaviour/min was calculated and cumulated for the first 19 min of the exposure. These new variables were then correlated with the behaviour during the whole exposure (30 min) using Spearman rank correlations of SAS (SAS Institute, 1996).
3. Results 3.1. Novel food versus novel object When provided with the novel food, the cows showed increased sniffing (frequency: F1,6 = 8.28; P < 0.05; duration: F1,6 = 8.98; P < 0.05) and remained standing for a longer time (F1,6 = 8.6; P < 0.05) than when the novel object was presented (Table 3). Furthermore, exposure to novel food led to increased frequency of self-grooming compared with the novel object (F1,6 = 16.77; P < 0.01). 3.2. Unfamiliar person versus novel food and novel object Comparison of responses toward the unfamiliar person versus the two other novel stimuli were only possible for three variables, and only one came out as significant: during the initial
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Behavioural variable
Usual food
Novel food
Novel object
Unfamiliar person
P-value
Latency to sniff (s) Duration of sniffing/min (s) Duration of sniffing/min during 5 min (s) Frequency of sniffing/min. Frequency of sniffing/min during 5 min Latency to eat (s) Duration of eating/min (s) Frequency of eating/min Duration of being away/min (s) Frequency of being away/min Maximal distance score Mean distance score Latency to self grooming (s) Frequency of self-grooming/min Duration of standing/min (s)
13 (5–1800) 0.3 ± 0.2***
67 (5–1800) 1.2 ± 0.4 5±2 0.2 ± 0.04 0.6 ± 0.2a
25 (5–300)
NS 0.05 NS NS 0.01
13 (0–186)*** 53 ± 2*** 0.2 ± 0.03** 7 ± 2*** 0.2 ± 0.04**
37 (2–115) 3±1 11 ± 1 0.3 ± 0.04 1.0 ±0.1ab 342 (51–1800) 1 ± 0.1 0.1 ± 0.02 54 ± 2 0.4 ± 0.04
470 (17–1800) 0.3 ± 0.1∗ 60 ± 0
268 (34–1000) 0.5 ± 0.1 55 ± 5
442 (59–1800) 0.1 ± 0.1 38 ± 5
0.03 ± 0.01***
57 ± 1 0.3 ± 0.04
9±2 1.8 ± 0.4b
NS NS 4.1 ± 0.2 2.8 ± 0.2 NS 0.01 0.05
Data are means ± S.E. except for latencies which are shown as medians followed by the full range. (∗ ) Indicates differences between usual and novel food, whereas different superscripts and P-values indicates differences between the three novel stimuli.
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Table 3 Behaviour of the dairy cows when exposed to either usual food (30 min; n = 16), novel food (30 min; n = 15), a novel object (30 min; n = 15) or an unfamiliar person (5 min; n = 15)
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5 min the cows sniffed the unfamiliar person at a higher frequency than the novel object (F2,27 = 5.70; P < 0.01) (Table 3). 3.3. Novel versus usual food When the cows were fed their usual food, they started eating almost immediately and spent 88% of the time eating (Table 3). When the same cows were fed novel food, the frequency (F1,7 = 17.43; P < 0.05) and duration (t = −31.2; P < 0.001) of eating decreased (Table 3). Provision of novel food led to an increased duration and frequency of head away from the food (frequency: F1,7 = 11.9; P < 0.01; duration: P < 0.001), increased duration and frequency of sniffing (frequency: F1,7 = 82.7; P < 0.001; duration: F1,7 = 49.0; P < 0.001) as well as increased frequency of self-grooming (F1,7 = 5.73; P < 0.05). 3.4. Correlations between responses toward novel stimuli Paired comparisons of variables from the three presentations of novel stimuli led to 164 possible inter-test correlations. However, only four (2.4%) came out as significant. The duration of sniffing the novel object correlated negatively with the duration of eating novel food (rs = −0.55; P < 0.05) and with the frequency of eating novel food (rs = −0.60; P < 0.05). Furthermore, the frequency of sniffing the novel object correlated negatively with the same two variables (rs = −0.59; P < 0.05 and rs = −0.63; P < 0.05), respectively). 3.5. Temporal development in the behavioural responses toward novel stimuli Figs. 1 and 2 show the correlations between the behaviour during the whole exposure and the cumulated values from the start of the test and up to 19 min after test initiation. After about 8 min of exposure the correlations for most variables were significant with rs between 0.8 and 1 for the novel food, and for the novel object most variables were significant with rs between 0.8 and 1 after about 14 min of exposure.
4. Discussion When dairy cows were exposed to novel stimuli in their home environment, novel food or an unfamiliar person induced increased behavioural responses compared with a novel object observed as increased exploration, increased signs of behavioural conflict as well as reduced lying behaviour. Compared with the provision of usual food, exposure to novel food led to signs of neophobia and behavioural conflict. Furthermore, very few inter-test correlations were found between individual responses toward the three novel stimuli. Exposing dairy cows to novel food in the home environment induced behavioural responses differing from responses toward the novel object. The cows showed increased sniffing behaviour, remained standing for a longer period after exposure to the novel stimulus, and performed a higher frequency of self-grooming behaviour during stimulus exposure. Fear has been suggested to be reflected in the level of approach and avoidance (Gray, 1987), but depending on characteristics of the fear inducing stimulus, behaviour associated
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with negative emotions can be very variable and even show opposite directions such as active defence, active avoidance or movement inhibition (Boissy, 1998). Furthermore, both displacement behaviours, behavioural transitions and inhibition of exploration have been suggested as indicators of fear (Hughes, 1997; Boissy, 1998). The increased sniffing behaviour observed during exposure to the novel food compared with the novel object could, therefore, indicate that the novel food induced the lowest level of fear, since exploration was not inhibited. The observed duration of standing and increased frequency of self-grooming, however, points in another direction. Firstly, when lying down, ruminating and turning the head away from the novel object, the cows appeared in-alert and not ready for defence or escape. Thus, this behaviour suggests a lack of responsiveness, a low level of arousal and no fear.
Fig. 1. Cummulative correlation coefficients (rs ) of each minute of testing with the total testing time for six variables from the behavioural responses toward novel food.
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Secondly, it has been shown that during exposure to novel food, heifers showing the largest decrease in consummatory behaviour showed the highest frequency of self-grooming (Herskin and Munksgaard, 2000), suggesting that the frequency of self-grooming might be used as a measure of behavioural responsiveness toward novel food. Accordingly, earlier reports have described self-grooming as an indicator of behavioural conflict in cattle (Simonsen, 1979; Kerr and Wood-Gush, 1987). In the present experiment the cows, therefore, seemed to be more in conflict when presented with the novel food than a novel object. Recently, Herskin et al. (2003a,b) concluded that exposure to novel food induces a low, but existing level of fear in dairy cows. The present results suggest that a novel food stimulus induces a higher level of fear than a novel object, however emphasizing the importance of including other behavioural states than approach or avoidance in the interpretation of negative emotions.
Fig. 2. Cumulative spearman correlation coefficients (rs ) of each minute of testing with the total testing time for six variables from the behavioural responses toward a novel object.
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The use of two very different types of sampling during the behavioural tests (continuous recording versus scanning) means that direct comparison of behavioural responses were only possible for three variables. Here, it was found that the dairy cows showed a higher frequency of sniffing directed at the unfamiliar person than at the novel object (sniffing toward the novel food was intermediate), while no differences were found for the latencies to sniff the novel stimuli or for the duration of sniffing. These results might suggest that the unfamiliar person was the less fear inducing of the three stimuli; a non-surprising suggestion since the cows were used to human presence, and therefore, only the identity of the test-person and the type of clothing were new to the cows. The analyses of inter-test correlations between individual responses toward the three novel stimuli were not as limited as the direct behavioural comparisons. Over all, 76 possible correlations between responses toward the unfamiliar person versus the two other novel stimuli were calculated, and none of them came out as significant. Therefore, the present data suggest that behavioural responses in the unfamiliar person test are not reflections of responses obtained in the novel food test or the novel object test. Thus, these results confirm earlier suggestions of stimulus specificity in the reactions of dairy toward challenging events (Herskin, 2004), even in the present tests, where situational factors were very comparable, and differences could not be attributed to handling or social isolation. Fearfulness might be a basal trait of the temperament of individuals, predisposing a response toward different alarming challenges (as discussed by Boissy, 1995; Desiré et al., 2002). However, no consistent individual behavioural responses toward the three novel stimuli were observed, since only four correlations out of 164 came out as significant, that is much less than would have been expected by chance. Van Reenen et al. (2004) reviews that the latency to approach a novel object has been used as a reference measurement of fear in poultry, pigs and cattle, with long latencies putatively indicating high levels of fear and vice versa, and the correlations between this measure and scores in other fear inducing test situations are though to reflect control by the same underlying variable e.g., fearfulness. In the present experiment, the latency to sniff the novel object varied considerably between individual cows (range: 5–1800 s), but this variable did not correlate with any of the variables from the two other tests. One reason for this lack of relation between the latency to sniff the novel object and the behavioural responses toward the other novel stimuli might be that the present presentation of a novel object in the home environment did not seem to be fear inducing. However, the present results suggest that the behavioural responses toward the three novel stimuli are not controlled by one single underlying mechanism or trait. Compared with the usual food, provision of novel food to the cows led to reduced consummatory behaviour, increased exploration, increased avoidance as well as increased self-grooming. From earlier experiments it is suggested that the degree of novelty in the food as well as the test situation is reflected in the behavioural responses (e.g., increased novelty leads to increased exploration, less consummatory behaviour, increased self-grooming as well as increased frequency of behavioural transitions) (Herskin et al., 2003a). The results from the present study confirm this on a larger animal material and using a longer duration of exposure (30 min versus 10 min). However, the results suggest that a test duration of 10 min is enough. Taken together, the present comparison of behavioural responses toward usual and novel food suggest that novel food elicits a strong behavioural response containing elements of motivational conflict, fear and exploration.
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In conclusion, the results of the present study suggest that dairy cows show behavioural responses characterised by increased exploration, reduced lying behaviour as well as increased behavioural conflict when exposed to novel food or an unfamiliar person compared with a novel object. Furthermore, very few inter-test correlations were found between individual responses toward the three novel stimuli. Thus, no evidence for consistent responses toward novel stimuli presented in the home environment were found.
Acknowledgements We wish to thank Gynther Nielsen and Anton Steen Jensen for technical assistance in the barn and Eric L. Decker for statistical advice.
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Littell, R.C., Miliken, G.A., Stroup, W.W., Wolfinger, R.S., 1996. SAS System for Mixed Models, SAS Inst. Inc., Cary, NC, USA. Manteca, X., Deag, J.M., 1993. Individual differences in temperament of domestic animals: a review of methodology. Anim. Welf. 2, 247–268. Martin, P., Bateson, P., 1993. Measuring Behaviour—An Introductory Guide, second ed. Cambridge University Press, 222 pp. Munksgaard, L., Jensen, M.B., 1996. The use of open field tests in the assessment of welfare of cattle. Acta Agric. Scand. Sect. A, Animal Sci. Suppl. 27, 82–85. Munksgaard, L., Simonsen, H.B., 1996. Behavioural and pituitary adrenal-axis responses of dairy cows to social isolation and deprivation of lying down. J. Anim. Sci. 74, 769–778. Munksgaard, L., De Passillé, A.M., Rushen, J., Thodberg, K., Jensen, M.B., 1997. Discrimination of people by dairy cows based on handling. J. Dairy Sci. 80, 1106–1112. Munksgaard, L., de Pasillé, A.M., Rushen, J., Herskin, M.S., Kristensen, A.M., 2001. Dairy cows’ fear of people: social learning, milk yield and behaviour at milking. Appl. Anim. Behav. Sci. 73, 15–26. SAS Institute, 1996. SAS/STAT User Guide 6.12, SAS Institute Inc., Cary, NC. Schrader, L., 2002. Consistency of individual behavioural characteristics of dairy cows in their home pen. Appl. Anim. Behav. Sci. 77 (4), 255–266. Simonsen, H.B., 1979. Grooming behaviour in domestic cattle. Nord. Vet. Med. 31, 1–5. Van Reenen, C.G., Engel, B., Ruis-Heutinck, L.F.M., Van der Wert, J.T.N., Buist, W.G., Jones, R.B., Blokhuis, H.J., 2004. Behavioural reactivity of heifer calves in potential alarming test situations: a multivariate and correlational analysis. Appl. Anim. Behav. Sci. 85, 11–30. Veissier, I., Le Neindre, P., 1992. Reactivity of Aubrac heifers exposed to a novel environment alone or in groups of four. Appl. Anim. Behav. Sci. 33, 1–15.
Behavioural responses of dairy cows toward novel stimuli presented in the home environment Mette S. Herskin a,∗ , Anne-Marie Kristensen b , Lene Munksgaard a a
Department of Animal Health and Welfare, Danish Institute of Agricultural Sciences, Research Centre Foulum, P.O. Box 50, 8830 Tjele, Denmark b Department of Zoology, Institute of Biological Sciences, Building 135, University of Aarhus, 8000 Aarhus C, Denmark Accepted 22 April 2004
Abstract Several tests of behavioural and physiological responses toward novel stimuli are used in the study of stress and adaptability in cattle. The majority of them, however, are characterised by a relatively high degree of situational novelty and stimulus complexity. In the present experiment we examined behavioural responses of dairy cows toward novel stimuli presented in the home environment with minimal situational novelty, and investigated whether any consistency could be found across responses toward different novel stimuli. Four different stimuli were presented: usual food (30 min provision of 8 kg total mixed ration); novel food (30 min provision of 5 kg of carrots); novel object (30 min exposure to a white plastic container) and an unfamiliar person (5 min exposure to person dressed in hooded white overall). Sixteen Danish Friesian cows kept in tie-stalls were used, and one stimulus presented each day in a balanced order according to a Latin Square design. The presentations of novel food or a novel object resulted in several comparable variables, and a comparison of the responses showed that the novel food induced increased duration and frequency of sniffing (P < 0.05 for both), increased self-grooming (P < 0.01) as well as a longer duration of standing (P < 0.05) compared with the novel object. Responses toward the unfamiliar person could only be compared with responses toward the other novel stimuli for three variables. Here, the unfamiliar person induced a higher frequency of sniffing than the novel object (P < 0.01). These results suggest that dairy cows show increased behavioural responses characterised by increased exploration, arousal as well as behavioural conflict when exposed to novel food or an unfamiliar person compared with a novel object. ∗
Corresponding author. Tel.: +45-89-99-13-28; fax: +45-89-99-15-00. E-mail address: [email protected] (M.S. Herskin). 0168-1591/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2004.06.006
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Correlations between responses toward the different novel stimuli were low and non-significant. Thus, no evidence for consistent inter-test responses across the novel stimuli presented in the home environment were found. © 2004 Elsevier B.V. All rights reserved. Keywords: Novelty; Behavioural test; Cattle; Food; Fear; Neophobia
1. Introduction During the production cycle, dairy cows in intensive production systems are exposed to various challenging events including novel stimuli (e.g., handlers, food, group-mates). The welfare of an individual animal depends on the ability to cope with environmental challenges (Broom, 1988). Novelty is generally associated with negative emotions (Gray, 1987; Boissy, 1995), however, individual behavioural and physiological responses toward challenging events can be very variable (Manteca and Deag, 1993). If individual emotional reactivity is consistent across different challenging events, highly reactive animals may experience more fear when subjected to novel management routines, regrouping, etc. In cattle, however, there are conflicting reports on whether individual emotional reactivity is consistent across different challenging events as described by Boissy and Bouissou (1995) or whether responses depend on the challenging event in question as suggested by Schrader (2002) and Van Reenen et al. (2004). Several tests of behavioural and physiological responses toward novel stimuli have been used in the study of stress and adaptability in cattle (e.g., exposure to a novel arena (Boissy and Bouissou, 1995; Munksgaard and Simonsen, 1996), a novel object (Hemsworth et al., 1996; Schrader, 2002) or a novel person (Hemsworth et al., 1996; Munksgaard et al., 1997). Typically, behavioural tests of responses toward novel stimuli are standardised by the use of an arena, even though the stimulus in question is not the arena itself, but a person (Hemsworth et al., 1996), an object (Hemsworth et al., 1996) or even food (Boissy and Bouissou, 1988). As a consequence, the responses of the animals are affected by both the stimulus in question as well as situational factors (Manteca and Deag, 1993). Interpretation of responses in terms of stress and emotion is further complicated by the fact that the animals are subjected to handling and social isolation during testing (Le Neindre, 1989; Munksgaard and Jensen, 1996; Hopster, 1998). Separation of an individual cow from its group-mates induces stress responses (Boissy and Le Neindre, 1990) with a high degree of individual variation (Hopster et al., 1998). Using social isolation in an arena during testing, therefore, provokes behavioural responses, where the specific effects of each element of the test situation are (1) very difficult to separate from each other; and (2) varies considerably between individuals. Furthermore, Munksgaard et al. (1997) found no relation between individual behavioural responses of dairy cows when presented with an unfamiliar person in the home or a novel environment. Thus, responses to specific stimuli in a novel environment may not reflect the responses of the animals in their home environment. At present time, the information about behavioural responses toward novel stimuli presented in the home environment is sparse, mainly because individual testing of animals kept
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in groups might be confounded by the behaviour of group-mates (Veissier and Le Neindre, 1992). There has, however, been developed behavioural tests based on the approach behaviour of dairy cows presented with a human in the home environment (e.g., Munksgaard et al., 1997; Munksgaard et al., 2001). Furthermore, we have recently presented data on novel food testing in cattle kept in tie-stalls, suggesting that the use of food as a novel stimulus permits individual testing in a home environment, where the animals have limited social contact and are not handled during testing (Herskin and Munksgaard, 2000; Herskin et al., 2003a,b). The use of behavioural tests like these for the evaluation of emotional reactivity allows a marked reduction in the situational complexity, compared with the majority of the earlier tests of emotional reactivity in dairy cattle (e.g., Boissy and Bouissou, 1995; Hopster, 1998; Van Reenen et al., 2004). In the present paper dairy cows in their home environment were exposed to three different novel stimuli in order to: (1) compare behavioural responses toward novel food, a novel object and an unfamiliar person; and (2) investigate whether any inter-test consistency could be found across behavioural responses toward presentations of novel stimuli in the home environment.
2. Materials and methods 2.1. Animals, housing and feeding Sixteen Danish Friesian cows from the resident herd at Research Centre Foulum were used. All cows were in their first lactation 122 ± 15 days (mean ± S.E.) post partum. The cows were tethered with neck-bar ties in individual stalls measuring 180 cm × 120 cm on mats of hard rubber material and with chopped straw added daily. Feeding troughs in front of the cows were separated from neighbouring stalls by a 70 cm × 70 cm wooden partition. Experimental cows were never placed next to each other, and none of the cows had any experience with carrots, white plastic jars, the test-person or the clothing of the test-person before testing. The cows were fed a total mixed ration consisting of (% dry matter): 22 grass silage, 14 beet molasses, 12 barley, 33 wheat whole crop, 18 concentrates and 1 minerals. Feeding took place daily at 09:30 h from a fodder truck making the same route through the barn every day. Between 08:30 and 09:00 h all feeding troughs were emptied and all experimental cows had no access to food for at least 45 min before testing. 2.2. Experimental design Eight of the cows were subjected to one of the four different stimuli on four subsequent days in a balanced order according to a Latin Square design (Martin and Bateson, 1993). This was repeated the following week with the remaining eight cows. The experimental cows were kept in two rows in the barn to ensure that the unfamiliar person, who started testing in one end of the barn, did not need to walk in front of cows not yet tested.
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2.3. Types of stimuli 2.3.1. Provision of usual food At 09:45 h all experimental cows were standing. The fodder truck fed usual food to the non-experimental cows. Immediately after the fodder truck had passed each experimental cow, a person dressed like the usual caretakers emptied 8 kg of usual food into the cleaned feeding troughs from a basket made of orange plastic. The behaviour of the cows was video recorded in real time for the following 30 min. The videotapes were analysed by focal sampling and continuous recording (Martin and Bateson, 1993). An ethogram of the recorded behaviour is shown in Table 1. 2.3.2. Novel food Five kilograms of washed carrots without tops were used as novel food. During the novel food exposure, all procedures were similar to the provision of usual food. 2.3.3. Novel object A white plastic container measuring 35 cm × 25 cm × 10 cm filled with 800 g sand was used as novel object. In order to introduce the novel object without human presence, the container was fixed to a rope and placed on a bar above the experimental cow (but not in her field of vision) 23 h before the stimulus presentation. At 09:00 h when all experimental cows were standing, the container was lowered from the stall of the neighbouring cow and placed on the edge of the feeding trough in front of the experimental cow. The rope was tied to prevent the container from overturning. The behaviour of the experimental cow was video recorded in real time for 30 min before removal of the container. The videotapes were analysed by focal sampling and continuous recording (Martin and Bateson, 1993). An ethogram of the recorded behaviour is shown in Table 1. 2.3.4. Unfamiliar person The female test-person (height 1.60 m; weight 55 kg) was dressed in a hooded white overall and kept the hands hidden inside the sleeves. The person stood motionless in front of the cow at the edge of the feeding trough for 5 min. An observer dressed like the usual caretakers, was placed behind the test-person about two stalls away, making direct observations. The distance between the cow and the test-person was divided into scores according to Munksgaard et al. (1997) (Table 2) and registered by direct scanning (Martin and Bateson, 1993) every fifth second. 2.4. Variables 2.4.1. Provision of usual and novel food The following variables were calculated from the food exposures: (1) latency to sniff the food (s); (2) duration of sniffing/min of food exposure (s); (3) frequency of sniffing food/min of exposure; (4) latency to eat (s); (5) duration of eating/min of food exposure (s); (6) frequency of eating/min of food exposure; (7) duration of being away from food/min of exposure (s); (8) frequency of being away from food/min of exposure; (9) duration
Behavioural parameter Body posture States based on increasing distance between the animal and the stimulus
Definition Standing Lying Eat food/touch object Sniff stimulus
Head away
Maximum distance
Events
Self-grooming
Interaction with neighbour
Usual/novel food
Novel object
The cow is chewing/licking the food. Intervals of <10 s were ignored. The cow is not eating. The muzzle touches the food. Intervals of <3 s were ignored. The head is kept above the tie-bar and the chain is loose. Not chewing or self-grooming. Includes being at maximum distance. The cow maintains the maximum distance to the stimulus by pulling the chain backwards. Not chewing or self-grooming. Licking any part of the body or scratching body against the fixtures of the stall. At least one of the neighbouring cows has at least the muzzle inside the stall of the experimental cow or vice versa.
The cow touches the novel object or the rope. Intervals of <10 s were ignored. The distance between muzzle and object is no more than the width of the muzzle. If touching, only with the outer part of the muzzle. Intervals of <3 s were ignored.
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Table 1 Ethogram of the behaviour recorded from video tape during 30 min after provision of the usual food, the novel food or the novel object
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Table 2 Categories used to score the distance between the test-person and the experimental cow during the exposure to the unfamiliar person (adapted from Munksgaard et al., 1997) Score
Definition
1 2 3 4 5 6
Physical contact between the cow and the test-person. The muzzle of the cow is closer to the person than the horizontal tie-bar. The muzzle is above or below the horizontal tie-bar. The muzzle is behind the horizontal tie-bar. The head is behind the horizontal tie-bar, facing forward, and the chain is tight. As score 5, but with the head turned to the rear.
of standing/min of food exposure; (10) latency to perform self-grooming (s); and (11) frequency of self-grooming/min of food exposure. 2.4.2. Novel object The following variables were calculated from the exposure to the novel object: (1) latency to sniff the object (s); (2) duration of sniffing object/min of exposure (s); (3) frequency of sniffing object/min of exposure; (4) duration of being away from the object/min of exposure (s); (5) frequency of being away from the object/min of exposure; (6) duration of standing/min of object exposure (s); (7) latency to perform self-grooming (s); and (8) frequency of self-grooming behaviour/min of object exposure. 2.4.3. Unfamiliar person The following variables were calculated from the scoring of distance between the testperson and the experimental cow: (1) latency to physical contact (score 1) (s); (2) duration of physical contact = number of intervals × 5 s; (3) frequency of physical contact; (4) mean score during the 5 min test; and (5) maximum score during the 5 min test. 2.5. Statistical analysis Four behavioural variables (lying down, head far away, touching object and interaction with neighbour) had too little representation in the data and were excluded. 2.5.1. Continuous variables The following variables: frequency of sniffing, duration of sniffing, frequency of eating, frequency of head away, frequency of self-grooming and duration of standing were subjected to analysis of variance using the Mixed procedure of SAS (Littell et al., 1996). The basic model included type of stimuli and order of type of stimuli as fixed effects. Time since calving was included as a covariate if P < 0.05. Cow identity, week number (1, 2) and day of the week (1–4) were included as random factors. Each cow was used as the experimental unit and the results of the statistical analysis are given by means ± S.E. as well as F(dftreatment , dferror ) and the P-value. Duration of sniffing and the frequency of eating, sniffing and self-grooming were transformed to square root before analysis in order to approximate a normal distribution and homogeneity of variances. The duration of eating novel food and the duration of head away
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from novel food , however, did not show homogeneity of variances and were analysed using the non-parametric paired t-test (SigmaStat, Jandel Scientific Inc.© ). Results are then presented as means ± S.E., given P-values. In order to compare the behavioural responses toward the novel food and the novel object with the responses toward the unfamiliar person, three common variables were calculated from the three stimuli presentations: (1) duration of sniffing during the initial 5 min of exposure to the novel food or the novel object, and the number of intervals with score 1 × 5 s when confronted with the unfamiliar person; (2) frequency of sniffing during the initial 5 min of exposure to the novel food or the novel object, and the number of intervals with score 1 when confronted with the unfamiliar person; and (3) latency to sniff the novel stimulus. These variables were compared using one-way repeated measures ANOVA (SigmaStat, Jandel Scientific Inc.©). 2.5.2. Censored latencies The latencies to eat, sniff and self-groom were regarded as censored variables (Kleinbaum, 1996) and analysed using the non-parametric life test for survival data (SAS Institute, 1996). The results are presented as medians, total range and P-value. 2.5.3. Individual responses toward novel stimuli Possible relations between the responses toward the three novel stimuli were analysed using non-parametric Spearman rank correlations (SAS Institute, 1996). 2.5.4. Temporal development in the behavioural responses toward novel stimuli In order to evaluate whether the behavioural responses continued during the whole exposure time or ceased earlier, the following variables were chosen as key variables: duration of being away, sniffing and eating as well as frequency of being away, sniffing and selfgrooming. For each variable, the behaviour/min was calculated and cumulated for the first 19 min of the exposure. These new variables were then correlated with the behaviour during the whole exposure (30 min) using Spearman rank correlations of SAS (SAS Institute, 1996).
3. Results 3.1. Novel food versus novel object When provided with the novel food, the cows showed increased sniffing (frequency: F1,6 = 8.28; P < 0.05; duration: F1,6 = 8.98; P < 0.05) and remained standing for a longer time (F1,6 = 8.6; P < 0.05) than when the novel object was presented (Table 3). Furthermore, exposure to novel food led to increased frequency of self-grooming compared with the novel object (F1,6 = 16.77; P < 0.01). 3.2. Unfamiliar person versus novel food and novel object Comparison of responses toward the unfamiliar person versus the two other novel stimuli were only possible for three variables, and only one came out as significant: during the initial
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Behavioural variable
Usual food
Novel food
Novel object
Unfamiliar person
P-value
Latency to sniff (s) Duration of sniffing/min (s) Duration of sniffing/min during 5 min (s) Frequency of sniffing/min. Frequency of sniffing/min during 5 min Latency to eat (s) Duration of eating/min (s) Frequency of eating/min Duration of being away/min (s) Frequency of being away/min Maximal distance score Mean distance score Latency to self grooming (s) Frequency of self-grooming/min Duration of standing/min (s)
13 (5–1800) 0.3 ± 0.2***
67 (5–1800) 1.2 ± 0.4 5±2 0.2 ± 0.04 0.6 ± 0.2a
25 (5–300)
NS 0.05 NS NS 0.01
13 (0–186)*** 53 ± 2*** 0.2 ± 0.03** 7 ± 2*** 0.2 ± 0.04**
37 (2–115) 3±1 11 ± 1 0.3 ± 0.04 1.0 ±0.1ab 342 (51–1800) 1 ± 0.1 0.1 ± 0.02 54 ± 2 0.4 ± 0.04
470 (17–1800) 0.3 ± 0.1∗ 60 ± 0
268 (34–1000) 0.5 ± 0.1 55 ± 5
442 (59–1800) 0.1 ± 0.1 38 ± 5
0.03 ± 0.01***
57 ± 1 0.3 ± 0.04
9±2 1.8 ± 0.4b
NS NS 4.1 ± 0.2 2.8 ± 0.2 NS 0.01 0.05
Data are means ± S.E. except for latencies which are shown as medians followed by the full range. (∗ ) Indicates differences between usual and novel food, whereas different superscripts and P-values indicates differences between the three novel stimuli.
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Table 3 Behaviour of the dairy cows when exposed to either usual food (30 min; n = 16), novel food (30 min; n = 15), a novel object (30 min; n = 15) or an unfamiliar person (5 min; n = 15)
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5 min the cows sniffed the unfamiliar person at a higher frequency than the novel object (F2,27 = 5.70; P < 0.01) (Table 3). 3.3. Novel versus usual food When the cows were fed their usual food, they started eating almost immediately and spent 88% of the time eating (Table 3). When the same cows were fed novel food, the frequency (F1,7 = 17.43; P < 0.05) and duration (t = −31.2; P < 0.001) of eating decreased (Table 3). Provision of novel food led to an increased duration and frequency of head away from the food (frequency: F1,7 = 11.9; P < 0.01; duration: P < 0.001), increased duration and frequency of sniffing (frequency: F1,7 = 82.7; P < 0.001; duration: F1,7 = 49.0; P < 0.001) as well as increased frequency of self-grooming (F1,7 = 5.73; P < 0.05). 3.4. Correlations between responses toward novel stimuli Paired comparisons of variables from the three presentations of novel stimuli led to 164 possible inter-test correlations. However, only four (2.4%) came out as significant. The duration of sniffing the novel object correlated negatively with the duration of eating novel food (rs = −0.55; P < 0.05) and with the frequency of eating novel food (rs = −0.60; P < 0.05). Furthermore, the frequency of sniffing the novel object correlated negatively with the same two variables (rs = −0.59; P < 0.05 and rs = −0.63; P < 0.05), respectively). 3.5. Temporal development in the behavioural responses toward novel stimuli Figs. 1 and 2 show the correlations between the behaviour during the whole exposure and the cumulated values from the start of the test and up to 19 min after test initiation. After about 8 min of exposure the correlations for most variables were significant with rs between 0.8 and 1 for the novel food, and for the novel object most variables were significant with rs between 0.8 and 1 after about 14 min of exposure.
4. Discussion When dairy cows were exposed to novel stimuli in their home environment, novel food or an unfamiliar person induced increased behavioural responses compared with a novel object observed as increased exploration, increased signs of behavioural conflict as well as reduced lying behaviour. Compared with the provision of usual food, exposure to novel food led to signs of neophobia and behavioural conflict. Furthermore, very few inter-test correlations were found between individual responses toward the three novel stimuli. Exposing dairy cows to novel food in the home environment induced behavioural responses differing from responses toward the novel object. The cows showed increased sniffing behaviour, remained standing for a longer period after exposure to the novel stimulus, and performed a higher frequency of self-grooming behaviour during stimulus exposure. Fear has been suggested to be reflected in the level of approach and avoidance (Gray, 1987), but depending on characteristics of the fear inducing stimulus, behaviour associated
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with negative emotions can be very variable and even show opposite directions such as active defence, active avoidance or movement inhibition (Boissy, 1998). Furthermore, both displacement behaviours, behavioural transitions and inhibition of exploration have been suggested as indicators of fear (Hughes, 1997; Boissy, 1998). The increased sniffing behaviour observed during exposure to the novel food compared with the novel object could, therefore, indicate that the novel food induced the lowest level of fear, since exploration was not inhibited. The observed duration of standing and increased frequency of self-grooming, however, points in another direction. Firstly, when lying down, ruminating and turning the head away from the novel object, the cows appeared in-alert and not ready for defence or escape. Thus, this behaviour suggests a lack of responsiveness, a low level of arousal and no fear.
Fig. 1. Cummulative correlation coefficients (rs ) of each minute of testing with the total testing time for six variables from the behavioural responses toward novel food.
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Secondly, it has been shown that during exposure to novel food, heifers showing the largest decrease in consummatory behaviour showed the highest frequency of self-grooming (Herskin and Munksgaard, 2000), suggesting that the frequency of self-grooming might be used as a measure of behavioural responsiveness toward novel food. Accordingly, earlier reports have described self-grooming as an indicator of behavioural conflict in cattle (Simonsen, 1979; Kerr and Wood-Gush, 1987). In the present experiment the cows, therefore, seemed to be more in conflict when presented with the novel food than a novel object. Recently, Herskin et al. (2003a,b) concluded that exposure to novel food induces a low, but existing level of fear in dairy cows. The present results suggest that a novel food stimulus induces a higher level of fear than a novel object, however emphasizing the importance of including other behavioural states than approach or avoidance in the interpretation of negative emotions.
Fig. 2. Cumulative spearman correlation coefficients (rs ) of each minute of testing with the total testing time for six variables from the behavioural responses toward a novel object.
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The use of two very different types of sampling during the behavioural tests (continuous recording versus scanning) means that direct comparison of behavioural responses were only possible for three variables. Here, it was found that the dairy cows showed a higher frequency of sniffing directed at the unfamiliar person than at the novel object (sniffing toward the novel food was intermediate), while no differences were found for the latencies to sniff the novel stimuli or for the duration of sniffing. These results might suggest that the unfamiliar person was the less fear inducing of the three stimuli; a non-surprising suggestion since the cows were used to human presence, and therefore, only the identity of the test-person and the type of clothing were new to the cows. The analyses of inter-test correlations between individual responses toward the three novel stimuli were not as limited as the direct behavioural comparisons. Over all, 76 possible correlations between responses toward the unfamiliar person versus the two other novel stimuli were calculated, and none of them came out as significant. Therefore, the present data suggest that behavioural responses in the unfamiliar person test are not reflections of responses obtained in the novel food test or the novel object test. Thus, these results confirm earlier suggestions of stimulus specificity in the reactions of dairy toward challenging events (Herskin, 2004), even in the present tests, where situational factors were very comparable, and differences could not be attributed to handling or social isolation. Fearfulness might be a basal trait of the temperament of individuals, predisposing a response toward different alarming challenges (as discussed by Boissy, 1995; Desiré et al., 2002). However, no consistent individual behavioural responses toward the three novel stimuli were observed, since only four correlations out of 164 came out as significant, that is much less than would have been expected by chance. Van Reenen et al. (2004) reviews that the latency to approach a novel object has been used as a reference measurement of fear in poultry, pigs and cattle, with long latencies putatively indicating high levels of fear and vice versa, and the correlations between this measure and scores in other fear inducing test situations are though to reflect control by the same underlying variable e.g., fearfulness. In the present experiment, the latency to sniff the novel object varied considerably between individual cows (range: 5–1800 s), but this variable did not correlate with any of the variables from the two other tests. One reason for this lack of relation between the latency to sniff the novel object and the behavioural responses toward the other novel stimuli might be that the present presentation of a novel object in the home environment did not seem to be fear inducing. However, the present results suggest that the behavioural responses toward the three novel stimuli are not controlled by one single underlying mechanism or trait. Compared with the usual food, provision of novel food to the cows led to reduced consummatory behaviour, increased exploration, increased avoidance as well as increased self-grooming. From earlier experiments it is suggested that the degree of novelty in the food as well as the test situation is reflected in the behavioural responses (e.g., increased novelty leads to increased exploration, less consummatory behaviour, increased self-grooming as well as increased frequency of behavioural transitions) (Herskin et al., 2003a). The results from the present study confirm this on a larger animal material and using a longer duration of exposure (30 min versus 10 min). However, the results suggest that a test duration of 10 min is enough. Taken together, the present comparison of behavioural responses toward usual and novel food suggest that novel food elicits a strong behavioural response containing elements of motivational conflict, fear and exploration.
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In conclusion, the results of the present study suggest that dairy cows show behavioural responses characterised by increased exploration, reduced lying behaviour as well as increased behavioural conflict when exposed to novel food or an unfamiliar person compared with a novel object. Furthermore, very few inter-test correlations were found between individual responses toward the three novel stimuli. Thus, no evidence for consistent responses toward novel stimuli presented in the home environment were found.
Acknowledgements We wish to thank Gynther Nielsen and Anton Steen Jensen for technical assistance in the barn and Eric L. Decker for statistical advice.
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