Hans W. Erhard

Individual aggressiveness of pigs can be measured and used to reduce aggression after mixing

Abstract Many studies have been carried out with the aim of reducing aggression after mixing unfamiliar pigs. A major problem in these studies has been the individual variation in aggressiveness between pigs. This study examined whether aggressiveness, as measured in tests on individual animals in a resident-intruder situation, is predictive of the level of aggression shown after mixing unfamiliar pigs, and whether information on this individual aggressiveness can be used to reduce aggression after mixing. One hundred eighty-nine pigs were tested for individual aggressiveness in their home pens and categorised as high- or low-aggressive (H or L), according to their attack latency. Eighty-eight of these pigs were then mixed in groups of eight, with four pigs from each of two litters. The combinations used were H H (4H + 4H), H L (4H + 4L) and L L (4L + 4L). In a follow-up study, a further 32 pigs were mixed into the combinations HL HL (HHLL + HHLL). The pigs were observed for 3 h on the day of mixing, and for 2 h on days 1, 2, 6 and 7 after mixing. During observations, aggressive interactions, and whether the pigs avoided lying down next to a pig from the unfamiliar litter were recorded. Fresh skin lesions were counted on each pig 2 h following mixing, and again 2 days later. In the majority of the groups, there was a clear distinction between a winner- and a loser-litter within the first 2 h after mixing. The number of pairs fighting in the 2 h immediately following mixing was lowest in the H L groups. The number of skin lesions on the pigs from the winner-litter both immediately after mixing and 2 days later was highest in H H groups. Thus, the relative level of aggressiveness seemed to determine the number of pairs that fought and the absolute level determined the intensity of fighting, with L pigs fighting less vigorously than H pigs. Speed of group integration was again affected by the absolute level of aggressiveness. The presence of H pigs in a group slowed down group integration. These data, particularly those relating to group integration, suggest that if mixing is unavoidable, it is preferable for pigs to be mixed into groups containing low-aggressive pigs only.

Effects of prenatal undernutrition on emotional reactivity and cognitive flexibility in adult sheep

The experiment reported was designed to test two hypotheses: that prenatal undernutrition (a) increases emotional reactivity and (b) impairs cognitive flexibility in sheep. The mothers of one group were fed live weight maintenance requirements throughout pregnancy (control, C) while those of another group were fed 50% of that amount from days 1 to 95 of pregnancy and 100% from then onwards (prenatal undernutrition, PU). At 18 months of age, PU sheep were more active during restraint (P < 0.05) and approached a novel stimulus more slowly (P = 0.02). In response to a sudden stimulus, PU males and C females showed a higher initial level of locomotion compared to C males, which only gradually declined, while PU females started at a high initial rate, changing rapidly to immobility. In a T-maze, PU resulted in a shift of side preferences (laterality) from a general right-bias to neutrality in males and to a left-bias in females (P < 0.05). In the two reversal tasks, C males and PU females had a preference for one side over the other, while PU males showed no preference. In contrast to C males, PU males failed to improve their learning speed from the first to the second reversal (P < 0.05). It is concluded that PU can lead to increased emotional reactivity and changes in side preference in both sexes and impaired cognitive flexibility in males. Undernutrition during pregnancy, therefore, not only affects the welfare of the dam, but also the personality of her offspring.

Individual differences in tonic immobility may reflect behavioural strategies

Abstract Many species of animals have been reported to show tonic immobility (TI) in response to physical restraint. In this paper, we investigate the interrelationship between the behaviour of pigs in three different situations, which are assumed to present challenges to the pigs. Individual piglets were tested for TI at 2.5 weeks of age (susceptibility to and duration of immobility), for their response to routine administration of an anti-parasite injection at 4 weeks of age (relaxed (R), tense (T), and struggle (S); vocalising yes/no), and for their speed and ease of movement through an unfamiliar environment at 10 weeks of age. We found TI to be predictive of behaviour across the two month test period. In the handling/injection situation pigs who vocalised were either tense or struggled. Relaxed pigs did not vocalise. We interpret this link between response (tense or struggle) and vocalisations as suggesting that both T and S were responses indicating that the pigs found the situation challenging, while the absence of vocalisations in conjunction with the relaxed muscles of the R pigs may indicate that the situation was perceived as presenting little or no challenge to the pigs. T/S pigs did not differ from R pigs in their behaviour in the TI test at 2.5 weeks. However, T pigs did show longer TI durations than S pigs. In the movement test, pigs who had previously shown a low susceptibility to TI moved faster through the unfamiliar environment than those who had become immobile. We propose that TI is one possible way of assessing whether individual pigs are more likely to adopt a more active (low susceptibility/short duration of TI, struggle, move fast) or a more passive behavioural strategy (high susceptibility to/long duration of TI, tense, move more slowly) in a challenging situation.

Measuring aggressiveness in growing pigs in a resident-intruder situation

Abstract Studies concerning aggression after mixing unfamiliar pigs have shown that there is a great variability in the levels of aggression shown by individual pigs. This study examined whether individual aggressiveness can be measured in a resident-intruder situation and whether it is a stable characteristic of individuals, which does not simply reflect the age or sex class of the animal. These latter requirements are of fundamental importance in establishing the existence of individual personality or temperament characteristics in animals. The research was carried out in three datasets, with a total of 218 pigs, females and entire males, at the age of 7 and 11 weeks. For the test, individual pigs were isolated in one half of their home pen, and an intruder pig was introduced. This pig was 2–3 weeks younger than the resident pig. The time from when the resident first made contact to when it attacked the intruder pig was used as a measure of aggressiveness. If the resident did not attack, the test was terminated after 3.5 min. The test was repeatable across two consecutive days as well as across four weeks. Aggressiveness was found to be unrelated to characteristics of the test pigs, such as sex, age, body weight and body weight ranked within litter. Attack latency was not affected by the sex of the intruder pig. If the intruder was less than half the body weight of the test pig, it was less likely to be attacked. Considerable variation was found within as well as between litters. The importance of the nature of the test arena, and implications of the duration of the test are discussed. Using attack latency as a measure of aggressiveness and a relatively short time limit, the test provides a useful tool for measuring aggressiveness without compromising the welfare of the animals involved.

Tonic immobility and emergence time in pigs—more evidence for behavioural strategies

The aim of this study was to further investigate the link between tonic immobility (TI) in pigs and active/passive behavioural strategies. Twenty-nine female and entire male pigs were subjected to a series of tests at the age of 3 weeks. Individual pigs were tested for their latency to emerge from a box and this was followed by a tonic immobility test. This procedure was carried out on four consecutive days. The behaviour of the pigs on day 1 differed from the behaviour on the other test days in that the emergence time was shorter (p<0.01), and in that pigs looked out of the box less frequently before leaving it (p<0.01). Emergence times on days 2–4 were correlated, but not with the emergence time on day 1. Pigs tended to be less resistant to TI on days 3 and 4 than on days 1 and 2. Pigs who did not become immobile in the TI test on day 1 had significantly shorter emergence times on that day than pigs who did become immobile (p<0.01). There were no other significant relationships between TI and emergence test behaviour. It is suggested that the link between TI and emergence time on the first test day reflects an underlying tendency to bring about change more or less quickly when faced with a challenging situation. These situations may therefore reveal differences in the active/passive dimension of personality.

Experience in Substrate-Enriched and Substrate-Impoverished Environments Affects Behaviour of Pigs in a T-Maze Task

Previous research showed that pigs reared in substrate-impoverished conditions performed a smaller proportion of their total behavioural repertoire in their home pens (showed lower behavioural diversity), than pigs reared in substrate-enriched conditions. This study examined whether these differences were the result of fundamental changes in behavioural organisation. A T-maze task was used to test the hypothesis that substrate-impoverished pigs are prone to develop fixed, unvarying behaviour which may underlie their reduced behavioural diversity. They were predicted to be poorer at reversing previous response patterns in the maze, and less able to alter their behaviour in response to a novel (distracting) stimulus. Female pigs were housed singly for five months in substrate-impoverished pens with bare concrete floors (N = 10) or substrate-enriched pens with straw and other foraging material (N = 10). The pigs were then trained to negotiate a T-maze to reach a food source. There were no differences in responses to a distracting stimulus in the start arm of the maze but, contrary to expectation, substrate-enriched pigs were less able to change their behaviour when the route to food was switched. Thus, the hypothesis was not supported. During training trials, substrate-enriched pigs moved fairly rapidly to the food

Prepubertal gonadotropin-releasing hormone analog leads to exaggerated behavioral and emotional sex differences in sheep.

In mammals, sex specialization is reflected by differences in brain anatomy and function. Measurable differences are documented in reproductive behavior, cognition, and emotion. We hypothesized that gonadotropin-releasing hormone (GnRH) plays a crucial role in controlling the extent of the brains sex specificity and that changes in GnRH action during critical periods of brain development, such as puberty, will result in altered sex-specific behavioral and physiological patterns. We blocked puberty in half of the 48 same-sex Scottish mule Texel cross sheep twins with GnRH analog (GnRHa) goserelin acetate every 3 weeks, beginning just before puberty. To determine the effects of GnRHa treatment on sex-specific behavior and emotion regulation in different social contexts, we employed the food acquisition task (FAT) and measurement of heart rate variability (HRV). ANOVA revealed significant sex and sex×treatment interaction effects, suggesting that treated males were more likely to leave their companions to acquire food than untreated, while the opposite effect was observed in females. Concordant results were seen in HRV; treated males displayed higher HRV than untreated, while the reverse pattern was found in females, as shown by significant sex and sex×treatment interaction effects. We conclude that long-term prepubertal GnRHa treatment significantly affected sex-specific brain development, which impacted emotion and behavior regulation in sheep. These results suggest that GnRH is a modulator of cognitive function in the developing brain and that the sexes are differentially affected by GnRH modulation.

How Studying Interactions Between Animal Emotions, Cognition, and Personality Can Contribute to Improve Farm Animal Welfare

This chapter provides an overview of the current behavioral and cognitive aspects of emotions in animals and explore the impacts of emotional experiences on the animals adaptation to its current challenging circumstances. There is evidence that animal welfare results from the animals perception of its environment and its background. The chapter is structured in four complementary sections. The first one addresses the nature of emotions that the animals can feel which is validated from commonalties in physiological and behavioral responses to dangers across and within species. The second section presents advanced features of the relationships between cognition and emotions originally studied in humans, which are now developed in animals to better access their affective states. The third section is devoted to the relevance of the personality concept, as resulting from both genetics and developmental experience, for assessing animal individuality in emotional behaviors and stress. The last section explores some approaches that can alleviate fear and induce positive affective states, with the potential to mitigate detrimental stress-induced effects on the welfare and health status by eliciting positive emotions in animals.

Ultradian activity rhythms in large groups of newly hatched chicks (Gallus gallus domesticus).

A clutch of young chicks housed with a mother hen exhibit ultradian (within day) rhythms of activity corresponding to the brooding cycle of the hen. In the present study clear evidence was found of ultradian activity rhythms in newly hatched domestic chicks housed in groups larger than natural clutch size without a mother hen or any other obvious external time-keeper. No consistent synchrony was found between groups housed in different pens within the same room. The ultradian rhythms disappeared with time and little evidence of group rhythmicity remained by the third night. This disappearance over time suggests that the presence of a mother hen may be pivotal for the long-term maintenance of these rhythms. The ultradian rhythm of the chicks may also play an important role in the initiation of brooding cycles during the behavioural transition of the mother hen from incubation to brooding. Computer simulations of individual activity rhythms were found to reproduce the observations made on a group basis. This was achievable even when individual chick rhythms were modelled as independent of each other, thus no assumptions of social facilitation are necessary to obtain ultradian activity rhythms on a group level.

Effects of pre- and postnatal polychlorinated biphenyl exposure on emotional reactivity observed in lambs before weaning

Humans and animals are exposed to PCBs and influences on developmental and endocrine processes are among the most pronounced effects. In the present study it was hypothesised that exposure to PCBs may interfere with sexually dimorphic behaviour. To test this hypothesis, behavioural studies in developmentally exposed sheep were conducted. Ewes were orally administered PCB 153 (98 μg/kg bw day), PCB 118 (49 μg/kg bw day) or corn oil from conception until delivery. However, because of accidental cross-contamination occurring twice causing a mixed exposure scenario in all three groups, the focus of this paper is to compare three distinct groups of lambs with different PCB levels (PCB 153 high-PCB 153 h, PCB 118 high-PCB 118 h, and low combined group-LC) rather than comparing animals exposed to single PCB congeners to those of a control group. Lambs were tested between 2 and 6 weeks of age. When LC males started the light/dark choice test in a dark box, they spent significantly more time in the dark part of the pen than LC females. This gender-related difference was not found in groups exposed to PCBs. A significant inhibitory effect on the activity level of males exposed to stress of confinement was found in the PCB 118 h group. In a high stress situation females from PCB 118 h and males from PCB 153 h were less active than their gender counterparts. The results support the hypothesis that intrauterine exposure to PCBs can alter sexually dimorphic behaviour of offspring.