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Both humans and nonhuman animals need to show self-control and wait for a larger or better reward instead of a smaller or less preferred but instant reward on an everyday basis. We investigated whether this ability undergoes ontogenetic development in domestic pigs (similar to what is known in human infants) by testing if and for how long nine- and 16-week-old pigs wait for a larger amount of their preferred reward. In a delay-of-gratification task, animals first learned that a small reward was hidden under a white cup and a large reward under a black cup, and then the delay to deliver the large reward was gradually increased. The results show that older pigs could wait longer for a larger reward than younger pigs (10.6 ± 1.3 s vs. 5.2 ± 1.5 s), thereby confirming our hypothesis of ontogenetic development of self-control in pigs. This self-control is likely to be regulated by the behavioural inhibition system and associated systems. Self-control or, more specifically the lack of it may be involved in the development of abnormal behaviours, not only in humans but also in animals. Therefore, research on self-control in decision-making might provide a new perspective on abnormal behaviours in captive animals.

Since the introduction of the backtest for the early detection of coping strategies in piglets by Hessing in the 1990s, this behavioural test has been intensively investigated with ambiguous results. One possible explanation for this lack of consistency might be the different classification methods used in many studies, so the first aim of this research was to investigate the inter-situational consistency of backtest behaviour in a set of 120 piglets. Through a correlation analysis, we related backtest behaviour with behaviours in other test situations (mixing/dominance; group testing: human approach test (HAT), novel object test (NOT), open door test (ODT); and individual testing: open field test (OFT)). Second, in a larger number of piglets (n = 3555), we investigated four different classification methods that use different parameters (latency, duration, and frequency) and different test repetitions (1, 2, 3, and 4). We then tested the effect of classifying the animals according to each method and analysing their distribution across categories and the variance in the behavioural data using the 120-piglet dataset (category analysis). Finally, we validated the results of the category analysis with the results of the correlation analysis. The correlation analysis revealed weak (dominance: rS

The assessment and provision of welfare in farm animals has become a major issue in animal science. A key element for providing good welfare is the enabling of positive affective states in the animals. As the serotonergic system plays a central role in regulating affective behavior, an increase in centrally available serotonin (5-HT) via dietary supplementation of its precursor, tryptophan (TRP), might be an approach to induce positive affective states. Therefore, the aim of our study was to investigate the effects of dietary TRP supplementation on brain TRP metabolism and 5-HT levels but also on affective state and behavioral reactivity in pigs. All subjects were fed a standard diet until 8 weeks of age, then feed was changed for all animals, with half the animals (control) receiving a diet with the recommended TRP content (2.5 g/kg), whereas the other half (TRP+) received a TRP-enriched diet (10.2 g/kg). In part 1 of our study, we investigated the effects of the dietary TRP supplementation on TRP metabolism in brain areas related to affective and cognitive processing. We found significantly increased concentrations of TRP and its metabolites in nearly all analyzed brain tissues. In part 2 of our study, we analyzed the effects of these alterations on the affective state as measured in a cognitive bias test, namely the spatial judgment task, but also on behavioral reactivity as measured in a combined open field/novel object test. The TRP enrichment revealed no significant behavioral changes in the open field/novel object tests. In the spatial judgment task, the TRP+ group showed more pessimistic behavior after dietary change than before. Thus, our results do not support the suggestion that TRP supplementation induces positive affective states and thus improves animal welfare in pigs.

Public concern for farm animal welfare calls for reliable scientific tools to measure it. Measuring cognitive bias, i.e., the influence of affective states on cognitive processing, has gained importance during recent years. The one most often adapted experimental design to test cognitive bias in non-human animals is the spatial judgement task, where animals must judge a goal box/pot based on its location. First, they learn to discriminate between a positively reinforced and a negatively reinforced location, and then they are confronted with ambiguous, intermediate locations. The responses to these so-called probe cues are assumed to be influenced by the animal’s affective state. Current methods for the assessment of cognitive bias in domestic pigs, one of the most intensively housed farm animal species in Europe, still need to be refined and validated. Hence, we developed an improved, reliable design to test pigs repeatedly and induce graded responses to graded probe cues. For this, we used a spatial judgement task in a go/no-go paradigm with partial reinforcement and a mildly aversive negative reinforcer. A total of 16 female juvenile German Landrace pigs underwent discrimination learning of the rewarded vs. punished goal box location; this was then repeatedly tested on three probe locations in between (eight times in four weeks). The subjects learned to discriminate between the two reference locations and showed graded responses (latency to open the goal box) to the probe locations. Analyses of the subjects’ general behaviour implied that additional information on the animals’ state can be derived. The subjects showed no signs of learning with respect to the outcome of probe cues but exhibited stable response levels during test weeks two to four. In conclusion, the design presented in this paper is suitable for spatial judgement tasks in domestic pigs. After successful validation it might be used for testing affective valence based on judgement bias and hence can contribute to our understanding of the welfare of this intensively farmed species.

Intensive husbandry usually offers only limited opportunities for animals to perform their characteristic species–specific behavior and can lead to boredom, stress or frustration. The positive impact of structural forms of environmental enrichment on animal welfare is well investigated because it is relatively low-cost and quickly performed. In contrast, approaches that integrated cognitive enrichment into the housing of animals are hardly investigated. The present study assessed the impact of structural and cognitive enrichment on learning as well as on the behavioral and physiological responses of 34 female dwarf goats ( Capra aegagrus hircus ) using a 2 × 2 factorial design. After weaning at the age of 5 weeks, the animals were randomly allocated to four groups (8–9 goats per group). Two of the animal groups were housed under conditions of structural enrichment; the other two groups under barren housing conditions. One group, respectively, obtained drinking water at a normal water bowl, the other obtained drinking water as a reward for a correct choice at a learning device, which was integrated into the housing pen and presented automatically visual four-choice discrimination tasks. Before the first and after each of three different learning tasks, the reactions of the animals to external challenges in a combined open-field/novel-object test were recorded. An enriched environment was shown to positively affect the learning performance of the goats. Structural enrichment of the housing conditions increased the motor activity of the animals in the external test situation, whereas cognitive enrichment lead to enhanced curiosity toward and prolonged contact with the unknown object. However, there were no differences in stress levels, which were measured through salivary cortisol, between any of the groups. We conclude that the combination of structural and cognitive enrichment in particular can improve the behavioral competence of dwarf goats in challenging situations and may have beneficial effects for their welfare.

a b s t r a c t The occurrence of different behavioural phenotypes in animals (regarding temperament and personality) has increasingly attracted the attention of scientists dealing with farm animal breeding, management and welfare. As part of the adaptation repertoire, coping behaviour describes how animals deal with chal- lenging situations. To detect different coping strategies (active vs. passive) in domestic pigs, Hessing et al. (1993) suggested using the backtest at an early age. However, the literature contains ambiguous results and criticism of the backtest. Thus, referring to Jensen (1995), the aim of our study was to analyse the backtest in terms of intra-situational behaviour (frequency distribution, behavioural consistency, heri- tability) in a large sample of domestic piglets (n = 3555). By using a statistical resampling analysis we wanted to verify whether the individual variation in the behaviour of the piglets in the repeated back- test indicates coping strategies or just random variation. The backtest was repeated four times between the first and fourth week of life (ages 5, 12, 19 and 26 days), and the latency, total duration and fre- quency of all struggling attempts were recorded. Our results show a continuous, unimodal distribution in the frequency parameter and an apparent bimodal distribution in the latency and duration parame- ter, that probably represents a unimodal distribution with a 'ceiling-effect'. The intra-test consistency of the behaviour (Spearman rank correlation (rS) and repeatability (R)) was moderate (rS = 0.19-0.45, p < 0.001; R = 0.25-0.39), indicating at least a certain degree of behavioural consistency. The resampling analysis revealed that the piglets did not show just random variation in behaviour. Moreover, the piglets did not display a general habituation to the repeated backtest. Based on a large pedigree, we calculated that the heritability of the behavioural parameters ranged from 0.17 to 0.43. In conclusion, the repeated backtest does not provide evidence for definitive coping strategies that are clearly separable. We instead found pronounced individual dispositions that are partly determined by genetics along a continuum from active to passive coping behaviour. This means that individuals show both behavioural consistency and flexibility in behaviour.

Vocalizations have long been recognized to encode information about an individual's emotional state and, as such, have contributed to the study of emotions in animals. However, the potential of vocalizations to also encode information about an individual's emotional reactivity has received much less attention. In this study, we aimed to test whether the vocalizations of domestic pigs contain correlates of emotional reactivity that are consistent between different contexts. We recorded vocalizations of 120 young female pigs in an experimental arena in two consecutive recording contexts, social isolation and an encounter with a familiar human. Simultaneously, we measured their heart rate and behaviour to determine their emotional reactivity in the same context (within-context). In addition, we aimed to determine the subjects' emotional reactivity in other contexts (across-context) by measuring their behaviour in four common tests of emotional reactivity, the human approach test, the open door test, the open field test and the novel object test. Using a cluster analysis, we identified four different call types. Significant inter-context correlations were found for all call types, suggesting that pig vocalizations are consistent within an individual across contexts. The call rate and the proportions of the individual call types were found to correlate significantly with indices of emotional reactivity both within and across contexts. Thereby, we found more significant correlations to indices of emotional reactivity within context (behavioural and physiological response during recording) compared to across context (behavioural response in the four emotional reactivity tests). The consistency of the vocal correlates to emotional reactivity between the different contexts depended on the call type. While we found moderate evidence that the high grunt is indicative of more active, more explorative and less fearful individuals both within as well as across contexts, the other call types provided less consistent results. Thus, it seems that some call types are better suited to provide information on a caller's emotional reactivity than others, and further research is needed to clarify the underlying influential factors.

Based on individual adaptive strategies (coping), animals may react differently to environmental challenges in terms of behavior and physiology according to their emotional perception. Emotional valence as well as arousal may be derived by measuring vagal and sympathetic tone of the autonomic nervous system (ANS). We investigated the situation-dependent autonomic response of 16 domestic pigs with either a reactive or a proactive coping style, previously selected according to the backtest which is accepted in piglets to assess escape behavior. At 11 weeks of age, the pigs were equipped with an implantable telemetric device, and heart rate (HR), blood pressure (BP) and their respective variabilities (HRV, BPV) were recorded for 1 hour daily over a time period of 10 days and analyzed in four behavioral contexts (resting, feeding, idling, handling). Additionally, the first minute of feeding and handling was used for a short-term analysis of these parameters in 10-s intervals. Data from day 1-3 (period 1) and day 8-10 (period 2) were grouped into two separate periods. Our results revealed general differences between the coping styles during feeding, resting and handling, with proactive pigs showing higher HR compared to reactive pigs. This elevated HR was based on either lower vagal (resting) or elevated sympathetic activation (feeding, handling). The short-term analysis of the autonomic activation during feeding revealed a physiological anticipation reaction in proactive pigs in period 1, whereas reactive pigs showed this reaction only in period 2. Food intake was characterized by sympathetic arousal with concurrent vagal withdrawal, which was more pronounced in proactive pigs. In contrast, neither coping style resulted in an anticipation reaction to handling. Vagal activation increased in reactive pigs during handling, while proactive pigs showed an increase in sympathetically driven arousal in period 2. Our findings confirm significant context-related differences in the general autonomic reaction of pigs with different coping styles. Additionally, the two coping styles differ in their affective appraisal over the time course of the experiment, underlining the importance of taking individual differences into account when studying affect and emotion in humans and animals.

Studies on consequences of affect on cognitive processing (cognitive bias) seem to provide proxy measures of the valence (positive/negative) of affective states. This article presents a pilot study testing a design for studies of judgment bias we adapted to the specific needs and abilities of domestic pigs. We used a spatial judgment paradigm, in which subjects learned to discriminate a food rewarded from an unrewarded position of a goal box during a training period, and then were tested for their responses to 3 equidistant intermediate probe positions during a testing period. After the training period, half of the subjects were repeatedly isolated from their social group to manipulate their affective state. Subjects learned the required discrimination task (positive vs. negative stimulus) and showed consistent differences in approach latencies toward and exploration of stimuli of different valence. Hence, the subjects' expectations could be inferred from their behavior. However, repeated social isolation had no effect on judgment of ambiguous stimuli and on both basal and test-related cortisol levels. In conclusion, the spatial judgment approach seems to provide a useful tool to detect and discriminate diverse affective states in domestic pigs based on their responses to graded ambiguous stimuli.

Cognitive enrichment, a special form of environmental enrichment, addresses the cognitive abilities of animals in captivity. Through cognitive interaction with the environment, the animals regain a certain control over their environment, and essential resources, such as food or water, act as a reward for successful coping. It is assumed that this process has important implications for animal welfare, especially in the intensive housing systems of farm animals. This study investigates the effects of cognitive enrichment on welfare-relevant behaviour (agonistic interactions and behavioural reactivity in a repeated open-field test) and autonomic control (heart rate variability during feeding, resting and in a repeated open-field test) in domestic pigs. A total of forty-eight pigs, Sus scrofa, were housed in groups of four. In six replicates, an experimental group was compared with a conventionally fed control group. The pigs in the experimental group were confronted with a cognitive challenge that was integrated into their familiar housing environment. Pigs were rewarded with food after they successfully mastered the discrimination of an individual acoustical signal followed by an operant task. The pigs in both groups reacted with sympathetic arousal to feeding announcement (increased heart rate (HR)). During feeding, the experimental pigs' HR decreased, and heart rate variability (HRV) increased, while the control pigs' HR stayed highly elevated and HRV decreased. These results are supported by a considerably larger number of agonistic interactions during feeding in the control group. During resting, the basal HRV of the experimental pigs increased (during operant conditioning) compared to the control. In the repeated open-field test, the experimental pigs displayed less locomotion and elimination as well as more contact with the wall and an unknown object compared to the control group. We conclude that cognitive enrichment leads to relaxed feeding and evokes longer lasting positive emotions. Moreover, the pigs displayed more explorative and less fearful behaviour in stressful situations. These findings support the use of cognitive enrichment to improve animal welfare.

The study and protection of animal welfare are based on the assumption that animals are sentient beings, capable of experiencing emotions. Still, our understanding of animal emotions is limited. In this review we focus on the potential of cerebral-lateralization research to provide new insights into animal emotional processing. Thereby, our aims were, first, to find a universal lateralization pattern in emotional processing across vertebrates and, second, to discuss how knowledge of emotional-lateralization patterns can be used in science and practice to contribute to improve farm-animal welfare. A literature review suggests evidence of lateralized functioning during emotional contexts across the vertebrate classes, from early vertebrates such as fish and amphibians to non-human primates. With the possible exception of fish, all vertebrate classes seem to show a similar lateralization pattern for emotional processing, with a right-hemisphere dominance for processing rather negatively connotated emotions, such as fear and aggression, and a left-hemisphere dominance for processing positively connotated emotions, such as those elicited by a food reward. Thus, both hemispheres are involved in emotional processing and hemispheric dominance may be used as an indicator of emotional valence (negative-positive). Although only a few domestic animal species (e.g. chicken, sheep, dog and horse) have been extensively studied with regard to emotional lateralization, evidence gathered so far suggests that the right-hemisphere dominance for fear and aggression and left-hemisphere dominance in responses to food rewards also applies to these species. Such patterns could be exploited in animal welfare studies to gain insight into how an animal experiences a potentially emotional situation and to improve farm-animal management. Further research should focus on rarely-studied species and on rarely-studied emotional contexts, such as sex and positive social situations, to improve our understanding of animal emotional lateralization.

The presence of an affiliative conspecific may alleviate an individual's stress response in threatening conditions. However, the mechanisms and neural circuitry underlying the process of social buffering have not yet been elucidated. Using the domestic pig as an animal model, we examined the effect of a 4-h maternal and littermate deprivation on stress hormones and on mRNA expression of the glucocorticoid receptor (GR), mineralocorticoid receptor (MR), 11ß-hydroxysteroid dehydrogenase (11ß-HSD) types 1 and 2 and the immediate early gene c-fos in various brain regions of 7-, 21- and 35-day old piglets. The deprivation occurred either alone or with a familiar or unfamiliar age-matched piglet. Compared to piglets deprived alone, the presence of a conspecific animal significantly reduced free plasma cortisol concentrations and altered the MR/GR balance and 11ß-HSD2 and c-fos mRNA expression in the prefrontal cortex (PFC), amygdala and hypothalamus, but not in the hippocampus. The alterations in brain mRNA expression were particularly found in 21- or 35-day old piglets, which may reflect the species-specific postnatal ontogeny of the investigated brain regions. The buffering effects of social support were most pronounced in the amygdala, indicating its significance both for the assessment of social conspecifics as biologically relevant stimuli and for the processing of emotional states. In conclusion, the present findings provide further evidence for the importance of the cortico-limbic network underlying the abilities of individuals to cope with social stress and strongly emphasize the benefits of social partners in livestock with respect to positive welfare and health.

Cognitive processes, such as stimulus appraisal, are important in generating emotional states and successful coping with cognitive challenges is thought to induce positive emotions. We investigated learning behaviour and autonomic reactions, including heart rate (HR) and its variability (standard deviation (SDNN) and root mean square of successive differences (RMSSD) of a time series of interbeat intervals). Twenty-four domestic pigs, Sus scrofa, housed in six groups of four, were confronted with a cognitive challenge integrated into their familiar housing environment. Pigs were rewarded with food after they mastered the discrimination of an individual acoustic signal followed by an operant task. All pigs quickly learned the tasks, while baseline SDNN and RMSSD increased significantly throughout the experiment. In reaction to the signals, pigs showed a sudden increase in HR, SDNN and RMSSD, and a decrease in the RMSSD/SDNN ratio. Immediately after this reaction, the HR and SDNN decreased, and the RMSSD/SDNN ratio increased. During feeding, the HR and the RMSSD/SDNN ratio stayed elevated. The pigs showed no cardiac reaction to the sound signals for other pigs or their feeding pen mates. We concluded that the level of cognitive challenge was adequate and that the observed changes in the autonomic tone, which are related to different dimensions of the affective response (e.g. arousal and valence), indicated arousal and positive affective appraisal by the pigs. These findings provide valuable insight into the assessment of positive emotions in animals and support the use of an adequate cognitive enrichment to improve animal welfare.

Cognitive challenges presented in connexion with the foraging behaviour of animals may have the potential to enrich the housing environment of captive animals, and thus can have beneficial effects on their behaviour and welfare. Therefore, we have developed a food-rewarded learning system based on a combination of classical and operant conditioning for groups of domestic pigs using acoustic cues (‘call-feeding station'). The present study investigated the characteristics of learning behaviour in seven experimental groups ( n =8 individuals each) of growing pigs in postnatal weeks 7–20. The behavioural budget of each group was observed weekly within the housing environment and compared to seven conventionally fed control groups ( n =8) which were supplied with an equal food amount. The alterations of individual behavioural responses after 6 and 12 weeks of cognitive enrichment were analysed in combined open-field/novel-object tests and compared to controls. All experimental pigs were able to discriminate reliably an individual tone that was associated with a locally changing feeding site. Generally, the animals were also willing to work for food (push a button with increasing fixed ratio, FR) but this motivation varied considerably between the groups ranging from FR 1 to 10. Sustained cognitive enrichment also affected other behavioural patterns within the housing environment as indicated by an increased locomotor behaviour and less belly nosing. Behavioural test responses were altered towards a greater reduction in open-field activity as well as a reduced excitement and fear behaviour compared to control pigs. Behavioural differences seem to be more pronounced the longer pigs were faced with the cognitive challenge. However, with equal food intake, the weight gain of the experimental pigs was not different compared to the controls. The present study suggests that, in domestic pigs, the presented cognitive enrichment may induce repeated positive appraisals in pigs by the association of successful coping with a demanding behavioural task rewarded by several small portions of food during the day. This appears to agree very well with pigs' motivational needs and may also be applicable for animal welfare enhancing management of feeding.

In the study of animal emotions, emotional valence has been found to be difficult to measure. Many studies of farm animals' emotions have therefore focussed on the identification of indicators of strong, mainly negative, emotions. However, subtle variations in emotional valence, such as those caused by rather moderate differences in husbandry conditions, may also affect animals' mood and welfare when such variations occur consistently. In this study, we investigated whether repeated moderate aversive or rewarding events could lead to measurable differences in emotional valence in young, weaned pigs. We conditioned 105 female pigs in a test arena to either a repeated startling procedure (sudden noises or appearances of objects) or a repeated rewarding procedure (applesauce, toy and straw) over 11 sessions. Control pigs were also regularly exposed to the same test arena but without conditioning. Before and after conditioning, we measured heart rate and its variability as well as the behavioural reactions of the subjects in the test arena, with a special focus on detailed acoustic analyses of their vocalisations. The behavioural and heart rate measures were analysed as changes compared to the baseline values before conditioning. A limited number of the putative indicators of emotional valence were affected by the conditioning. We found that the negatively conditioned pigs showed changes that were significantly different from those in control pigs, namely a decrease in locomotion and an increase in standing. The positively conditioned pigs, however, showed a stronger increase in heart rate and a smaller decrease in SDNN (a heart rate variability parameter indicating changes in autonomic regulation) compared to the controls. Compared to the negatively conditioned pigs, the positively conditioned pigs produced fewer vocalisations overall as well as fewer low-frequency grunts but more high-frequency grunts. The low-frequency grunts of the negatively conditioned pigs also showed lower frequency parameters (bandwidth, maximum frequency, 25% and 50% quartiles) compared to those of the positively conditioned pigs. In any of the statistically significant results, the conditioning accounted for 1.5-11.9% of variability in the outcome variable. Hence, we conclude that repeated moderate aversive and rewarding events have weak but measurable effects on some aspects of behaviour and physiology in young pigs, possibly indicating changes in emotional valence, which could ultimately affect their welfare. The combination of ethophysiological indicators, i.e., the concurrent examination of heart rate measures, behavioural responses and especially vocalisation patterns, as used in the current study, might be a useful way of examining subtle effects on emotional valence in further studies.

In modern intensive husbandry systems there is an increasing tendency for animals to interact with technical equipment. If the animal–technology interface is well-designed this may improve animal welfare by offering challenges for cognitive adaptation. Here a system and its application is presented that acoustically calls individual pigs out of a group (n = 8) to a feeding station. In three different learning phases, the computer-controlled “call-feeding-station” (CFS) trained the animals to recognize a specific acoustic signal as a summons for food, using a combination of classical and operant conditioning techniques. The experimental group's stall contained four CFSs, at each of which one animal at a time was able to feed. When an animal had learned to discriminate and recognize its individual acoustic signal it had to localize the particular CFS that was calling and to enter inside it. Then, it received a portion of feed, the amount of which was adapted to the respective age of the animals. Each animal was called at several, unpredictable times each day and the computer programme ensured that the total feed supply was sufficient for each animal. In the last phase of the experiment the animals, in addition, had to press a button with an increasing fixed ratio for the delivery of feed. It was demonstrated that the pigs were able to adapt quickly to the CFSs. Although they were challenged over 12 h daily by requirements of attention, sensory localization and motor efforts to gain comparatively low amounts of feed, they performed well and reached fairly constant success rates between 90 and 95% and short delays between 14 and 16 s between a summons and the food release in the last phase of the experiment. The weight gain during the experiment was the same as in a conventionally fed control group (n = 8). We therefore conclude that CFSs present a positive challenge to the animals with no negative effects on performance but with a potentially beneficial role for welfare and against boredom. The system is also a suitable experimental platform for research on the effects of successful adaptation by rewarded cognitive processes in pigs.

Emotionally relevant external events, hormone concentrations affecting mood and appetitive behaviour, thirst and hunger are able to stimulate a complex central nervous network that regulates endocrine feedback and behaviour in order to maintain or regain homeostasis. Particular states of mood or emotion may thus be accompanied by specific behaviours, vocalization being one of them. Hence, in farm animals vocalizations may supply us with hints on their well-being in an easy way, given that the meanings of the respective calls are well-established. Then, it is possible to judge acoustically uttered current needs and impaired welfare by non-invasive, continuous monitoring. Vocalizations may also modulate emotions of the receivers such that welfare may also be affected in conspecifics hearing distress utterances, e.g., in an abattoir. For these reasons, the analysis of farm animal vocalization has gained increasing interest in the last years and a variety of attempts to decode the meaning has been made. Concentrating on important farm animal species (pig, cattle, poultry) an overview of the present state-of-the-art in this discipline is given and present problems as well as possible future developments are discussed. Modern techniques of sound analysis have provided tools to discriminate, analyse and classify specific vocalizations. Taking advantage of this, future bioacoustical research for welfare assessment should focus on comprehensive studies of a broad spectrum of species specific distress vocalizations. Increasingly precise attributions of such utterances to environments, behavioural contexts and relevant physiological parameters will lead to a deeper understanding of their meaning and significance with respect to well-being of farm animals. The result will offer applicable acoustic tools for farming environments where non-invasive techniques for welfare judgements are urgently needed.

The nursing vocalisation of lactating sows is an important part of the complex nursing and suckling behaviour of domestic pigs (Sus scrofa). It helps to lead the young through the several phases of a nursing episode. A total of 135 suckling piglets were investigated regarding their reactions to different vocalisations and sounds successively replayed in combined choice/open-field experiments. Two piglet samples were used to determine the impact of age (sample 1: weeks 1 and 5, n=93) and previous test experience of naive older piglets (sample 2: week 5, n=42) on their behavioural responses. In the 1st week after birth, the nursing vocalisation of sows released an initial generalised approach and contact response in the young, indicating high motivation to gain nutritional or social support. Close to the sound source, the piglets then strongly preferred the nursing vocalisation produced by their own mothers compared to that produced by another, unrelated and unfamiliar sow, or an artificial sound composed of similar frequencies as the nurse grunting, or a control without sound. However, at the end of the suckling period (5-week-old piglets) no clear differences in the reactions to the sounds could be identified. Moreover, the lack of a clear response at week 5 seems largely independent of any earlier test experience of the piglets. As well in the 1st as in the 5th week the piglets showed a decrease in open-field activity when sow grunting was present, indicating that the replay of the nursing vocalisation might have some calming effect.

The effects of familiarity and relatedness on agonistic pair relationships (dyads) in different pen regions (pen area or trough area) were studied in 16 groups of newly mixed domestic pigs of similar weight (9 pigs per group) at an age of 12 weeks. The agonistic interactions (AI) within 124 familiar (related) and 452 unfamiliar (related and unrelated) dyads were continuously recorded for 3 days (10 h daily) after mixing. Whereas pigs, both in dyads familiar and unfamiliar to each other, showed the same frequency of AI in the trough area, unfamiliar dyads exhibited significantly more AI in the pen area than familiar dyads. The relatedness of unfamiliar dyads had apparently no influence on AI. It is discussed that, besides establishing a dominance hierarchy, pigs react aggressively on strange subjects. Furthermore, the results are briefly discussed with reference to dominance and resource usage in pigs.

Four trials were carried out, where in each trial during a selection test two groups of growing pigs (12 weeks old) with nine animals each were randomly formed. After a week, the top (TR) and bottom (BR) ranking pig from each group was isolated and kept under single housing conditions. At the age of 15 to 16 weeks, the test animals were confronted once with the familiar and once with the unfamiliar group. During the 10-h social confrontation test, agonistic behaviour (agonistic interactions, individual dominance values) and physiological stress reactions (epinephrine, norepinephrine, cortisol, heart rate) were investigated simultaneously. The social confrontation of a pig with a familiar or an unfamiliar group caused very frequent agonistic interactions during the first 30 min. This behaviour was accompanied by a rapid increase of the heart rate and the plasma catecholamine concentrations and a delayed increase of cortisol. TR pigs elicited more agonistic interactions during the first 30 min and displayed higher plasma catecholamine concentrations. Additionally, TR animals showed significantly higher dominance values during the 10-h testing situation compared to the BR pigs. The confrontation of an animal with the unfamiliar group resulted in a more pronounced adrenocortical reaction compared to the confrontation with the familiar group. In particular, the TR animals showed a distinct increase of plasma cortisol during the first hour and a later bradycardia when they were confronted with the unfamiliar group. The preliminary results presented in this paper indicate that pigs show different, but inconsistent behavioural and physiological reactions when they are confronted with a social group. The agonistic behaviour and the physiological stress reactions during a social confrontation test are still influenced by the former rank of the animal, even when the animal was isolated under single housing conditions in the meantime for 2 to 3 weeks.

Social deprivation is a severe stressor affecting a number of behavioral and physiological functions of gregarious species. It is assumed that, dependent upon the level of familiarity, social support given by a conspecific may attenuate the adverse consequences of stress. We investigated the effects of a 4h maternal and littermate deprivation on behavioral reactions, stress hormone responses and brain corticosteroid receptor expression in 7-, 21- and 35-day-old domestic piglets (Sus scrofa) that were left alone or in the presence either of a familiar or unfamiliar age-matched piglet. Compared to control animals, all of the socially deprived piglets showed significant stress responses, such as impaired habituation in repeated open-field/novel-object tests, enhanced ACTH and cortisol release, and altered corticosteroid receptor expression in the hypothalamus. In addition, our results demonstrated that younger piglets had more difficulty coping with stress. The presence of an age-matched conspecific had a direct calming effect on the deprived piglet during the deprivation procedure, which was revealed by diminished stress-induced HPA activity and altered reactions in the behavioral test situations (e.g., activity, escape, and vocalization). Furthermore, because the presence of a familiar piglet causes a more pronounced buffering effect, we have shown for the first time that the degree of familiarity between the piglets may influence the effectiveness of social support. Our study emphasizes the benefits of social partners on positive welfare and the ability for pigs to cope with stress; therefore, our results should be taken into account during handling practices such as weaning and mixing.

Studies on animal temperament have often described temperament using a one-dimensional scale, whereas theoretical framework has recently suggested two or more dimensions using terms like “valence” or “arousal” to describe these dimensions. Yet, the valence or assessment of a situation is highly individual. The aim of this study was to provide support for the multidimensional framework with experimental data originating from an economically important species (Bos taurus). We tested 361 calves at 90 days post natum (dpn) in a novel-object test. Using a principal component analysis (PCA), we condensed numerous behaviours into fewer variables to describe temperament and correlated these variables with simultaneously measured heart rate variability (HRV) data. The PCA resulted in two behavioural dimensions (principal components, PC): novel-object-related (PC 1) and exploration-activity-related (PC 2). These PCs explained 58% of the variability in our data. The animals were distributed evenly within the two behavioural dimensions independent of their sex. Calves with different scores in these PCs differed significantly in HRV, and thus in the autonomous nervous system’s activity. Based on these combined behavioural and physiological data we described four distinct temperament types resulting from two behavioural dimensions: “neophobic/fearful – alert”, “interested – stressed”, “subdued/uninterested – calm”, and “neoophilic/outgoing – alert”. Additionally, 38 calves were tested at 90 and 197 dpn. Using the same PCA-model, they correlated significantly in PC 1 and tended to correlate in PC 2 between the two test ages. Of these calves, 42% expressed a similar behaviour pattern in both dimensions and 47% in one. No differences in temperament scores were found between sexes or breeds. In conclusion, we described distinct temperament types in calves based on behavioural and physiological measures emphasising the benefits of a multidimensional approach.

In domestic pigs, vocalisation can be an indicator of distress and negative emotional states. It might play a role in the transfer of emotion between individuals (‘emotional contagion’ or ‘empathy’), which could result in impaired animal welfare on a group level based on the distress in an individual member of the group. The aim of this study was to characterise the responses of pigs to conspecific distress calls. We performed a playback experiment in an open arena with 24 juvenile German Landrace pigs, during which individual subjects were exposed to both conspecific distress calls and an artificial sine tone (control) on consecutive experimental days. Both behavioural (locomotion, vocalisation, elimination and distance to the speakers) and physiological responses (heart rate and heart rate variability) were measured for 2 min before, during and after the playback of the stimuli (distress calls/control). Subjects showed decreased locomotion and vocalisation rates during both stimuli, suggesting that the animals responded to both stimuli. Heart rates decreased at the onset of both stimuli due to an activation of the parasympathetic system, indicating an orientation response to sudden stimuli. However, heart rates decreased after the end of the distress calls but not after control stimuli, illustrating that conspecific calls and other sounds are evaluated differently. We conclude that pigs exposed to isolation are attentive to conspecific distress vocalisation and hence the information about threat possibly conveyed in it, but they do not share the distress of the caller. Therefore, we could not find direct effects of distress calls of unfamiliar conspecifics on the welfare of isolated juvenile pigs. However, the state of heightened attention elicited by conspecific distress calls may affect a pig's subsequent evaluation of its environment.

In most studies on animal learning, individual animals are tested separately in a specific learning environment and with a limited number of trials per day. An alternative approach is to test animals in a familiar environment in their social group. In this study, the authors--applying a fully automated learning device--investigated voluntary, self-controlled visual shape discrimination learning of group-housed dwarf goats (Capra hircus). The majority of the tested goats showed successful shape discrimination, which indicates the adaptive value of an effective learning strategy. However, in each group, a few individual goats developed behavioral strategies different from shape discrimination to get reward. Relocation impairs memory retrieval (probably by attention shifting) only temporarily for previously learnt shapes. The results demonstrate the usefulness of a self-controlled learning paradigm to assess learning abilities of social species in their normal social settings. This may be especially relevant for captive animals to improve their welfare.