Sandra Düpjan

Acetylcholine injection into the amygdala elicits vocalization in domestic pigs (Sus scrofa)

In a pilot study we have injected the amygdala of five female pigs (age 8 weeks) with acetylcholine (ACh, 5.5muM/20mul) and recorded short latency utterances. The evoked vocalizations displayed the characteristics of natural screams in sonagram appearance and hearing impression. Quantitative analyses, too, revealed the similarity of the ACh-evoked vocalizations with natural screaming. The results demonstrate for the first time that aversive vocalizations can be triggered by cholinergic amygdala stimulation.

Serotonin depletion induces pessimistic-like behavior in a cognitive bias paradigm in pigs

Cognitive and affective processes are highly interrelated. This has implications for neuropsychiatric disorders such as major depressive disorder in humans but also for the welfare of non-human animals. The brain serotonergic system might play a key role in mediating the relationship between cognitive functions and affective regulation. The aim of our study was to examine the influence of serotonin depletion on the affective state and cognitive processing in pigs, an important farm animal species but also a potential model species for biomedical research in humans. For this purpose, we modified a serotonin depletion model using para-chlorophenylalanine (pCPA) to decrease serotonin levels in brain areas involved in cognitive and affective processing (part 1). The consequences of serotonin depletion were then measured in two behavioral tests (part 2): the spatial judgement task (SJT), providing information about the effects of the affective state on cognitive processing, and the open field/novel object (OFNO) test, which measures behavioral reactions to novelty that are assumed to reflect affective state. In part 1, 40 pigs were treated with either pCPA or saline for six consecutive days. Serotonin levels were assessed in seven different brain regions 4, 5, 6, 11 and 13days after the first injection. Serotonin was significantly depleted in all analyzed brain regions up to 13days after the first application. In part 2, the pCPA model was applied to 48 animals in behavioral testing. Behavioral tests, the OFNO test and the SJT, were conducted both before and after pCPA/saline injections. While results from the OFNO tests were inconclusive, an effect of treatment as well as an effect of the phase (before and after treatment) was observed in the SJT. Animals treated with pCPA showed more pessimistic-like behavior, suggesting a more negative affective state due to serotonin depletion. Thus, our results confirm that the serotonergic system is a key player in cognitive-emotional processing. Hence, the serotonin depletion model and the spatial judgement task can increase our understanding of the basic mechanisms underlying both human neuropsychiatric disorders and animal welfare.

Behavioural lateralization in domestic pigs (Sus scrofa)—variations between motor functions and individuals

ABSTRACT Motor lateralization is hypothesized to depend on the complexity of the motor function, but it might at the same time reflect hemispheric dominance within an individual across motor functions. We investigated possible motor lateralization patterns in four motor functions of different complexity (snout use in a manipulative task, foot use in two-stepping tasks and tail curling) in the domestic pig, a tetrapod species relevant as farm animal but also as a model in human neuroscience. A significant majority of our sample showed individual biases for manipulation with their snout and for curling their tail. Interestingly, the tail curling was lateralized towards the right at the population level and showed stronger lateralization patterns than the snout. Using a cluster analysis with combined tail and snout laterality, we identified groups of individuals with different lateralization patterns across motor functions that potentially reflect the individuals’ hemispheric dominance. To conclude, our results suggest that pigs show lateralization patterns that depend on the motor function and on the individual. Such individual lateralization patterns might have broader implications for animal personality and welfare. Our study lays the methodological groundwork for future research on laterality in pigs.

Dietary tryptophan supplementation and affective state in pigs

ABSTRACT 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.

Vocalization as an indicator of estrus climax in Holstein heifers during natural estrus and superovulation

The reliable detection of estrus is an important scientific and practical challenge in dairy cattle farming. Female vocalization may indicate reproductive status, and preliminary evidence suggests that this information can be used to detect estrus in dairy cattle. The aim of this study was to associate the changes in the vocalization rate of dairy heifers with behavioral estrus indicators as well as test the influence of the type of estrus (natural estrus vs. superovulation-induced estrus). We analyzed 6 predefined estrus-related behavior patterns (standing to be mounted, head-side mounting, active mounting, chin resting, being mounted while not standing, and active sniffing in the anogenital region) and vocalization rates in the peri-estrus period (day of estrus ± 1 d) of 12 German Holstein heifers using audio-visual recordings. Each heifer was observed under natural estrus and a consecutive superovulation induced by FSH and cloprostenol. Estrus was determined by behavioral patterns and confirmed by clinical examination (vaginoscopy and ultrasound imaging of the ovaries) as well as by the concentration of peripheral progesterone. Estrus behavior and vocalization rates were analyzed in 3-h intervals (an average of 19 intervals for each heifer), and an estrus score was calculated based on the 6 behaviors. The interval with the highest estrus score (I0) was considered the estrus climax. We demonstrated similar time courses for the estrus score and vocalization rate independent of estrus type. However, in natural estrus, the maximum vocalization rate (±SE) occurred in the interval before estrus climax (I-1; 42.58 ± 21.89) and was significantly higher than that in any other interval except estrus climax (I0; 27.58 ± 9.76). During natural estrus, the vocalization rate was significantly higher within the interval before estrus climax (I-1; 42.58 ± 21.89 vs. 11.58 ± 5.51) than under superovulation. The results underscore the potential use of vocalization rate as a suitable indicator of estrus climax in automated estrus detection devices. Further studies and technical development are required to record and process individual vocalization rates.

Looking on the Bright Side of Livestock Emotions—the Potential of Their Transmission to Promote Positive Welfare

Emotions can be defined as an individuals affective reaction to an external and/or internal event that, in turn, generates a simultaneous cascade of behavioral, physiological, and cognitive changes. Those changes that can be perceived by conspecifics have the potential to also affect others emotional states, a process labeled as “emotional contagion.” Especially in the case of gregarious species, such as livestock, emotional contagion can have an impact on the whole group by, for instance, improving group coordination and strengthening social bonds. We noticed that the current trend of research on emotions in livestock, i.e., investigating affective states as a tool to assess and improve animal welfare, appears to be unbalanced. A majority of studies focuses on the individual rather than the social component of emotions. In this paper, we highlight current limitations in the latter line of research and suggest a stronger emphasis on the mechanisms of how emotions in livestock are transmitted and shared, which could serve as a promising tool to synergistically enhance the welfare of all individuals within a group.