Relations between peripheral and brain serotonin measures and behavioural responses in a novelty test in pigs

Possible relations between emotional contagion and social buffering

Emotional contagion can be defined as the transfer of an emotional state from the demonstrator of that state towards an observer. Social buffering is a process by which the demonstrator has a reduced stress response due to the presence of one or more other individuals. While both processes are well studied separately, it is unknown whether and how both processes are related. Therefore, the aim of this study was to investigate the relation between emotional contagion and social buffering in pigs. Hereto correlations were performed between measures of emotional contagion (i.e., the difference in behaviour of observer pigs between a situation with and without demonstrator pigs present) and measures of social buffering (i.e., the difference in behaviour of demonstrator pigs in a negative situation with and without observer pigs present). The results did not point towards a clear and consistent relation as only few and contrasting correlations between measures of emotional contagion and social buffering were found, and after correcting for chance no significant correlations remained. To conclude, more research is needed on the relation between emotional contagion and social buffering to shed light on how and when emotions will spread through and/or are buffered in a group of animals.

The Relation between Plasma Nesfatin-1 Levels and Aggressive Behavior in Pit Bull Dogs

Aggression is a prevalent and concerning behavioral issue in dogs. Pit Bull dogs, known for their high levels of aggression, are recognized as a focus of concern in society. In our study, we aimed to investigate the behavioral characteristics of Pit Bull dogs and explore the potential roles of peptides involved in the neurobiology of aggression. Initially, female, and male dogs underwent aggression tests, and their aggression levels were categorized. Plasma nesfatin-1, serotonin, oxytocin, and dopamine levels were quantified using ELISA, with blood samples collected after a 24 h fasting period and 2 h post-refeeding. Our findings indicate that aggression in Pit Bull dogs correlates with decreased plasma nesfatin-1, serotonin, and oxytocin levels, while dopamine levels increase. The study's findings indicate that fasted dogs exhibited lower plasma levels of nesfatin-1, serotonin, and dopamine, while plasma oxytocin levels were higher. Furthermore, while the research findings do not suggest a significant relationship between the severity of aggression and the gender of the dog, male Pit Bull breeds appear to have higher plasma nesfatin-1 and serotonin levels compared to their female counterparts. The study's findings demonstrate that nesfatin-1, serotonin, oxytocin, and dopamine play pivotal roles in Pit Bull dogs' aggression, indicating potential interactions among these neuropeptides at the central nervous system level.

Effects of a variable light intensity lighting program on the welfare and performance of commercial broiler chickens

Our previous variable-light intensity lighting program studies indicate the light intensity preference behavior of broilers for their daily activity including eating and resting. To evaluate the effects of variable-light intensity lighting program on performance and welfare of broilers, four commercial trials were conducted for looking at behaviors, mortality, leg-health, performance, and brain welfare indicator genes including tryptophan hydroxylase 2 and tyrosine hydroxylase (TH), glucocorticoid receptor (GR), brain-derived neurotropic factor (BDNF), and melanopsin (Opn4) gene expression. One-day-old broilers were housed in four commercial broiler houses. Each quadrant (section) of the house was placed with 4,800 chicks. A total of four lighting programs began on day 7 with 5 lux (lx), 20 lx, natural light (NL, 480 lx), and variable light (2-5/40 lx) using LED lights on a 16L:8D photoperiod. In the variable-light house, the number of dustbathing holes was significantly higher than that in natural-light houses and 5-lx and 20-lx houses. Daily physical activities, footpad condition, fear response to novel objects, body weight, feed conversion ratio, and the number of leg-problem induced culled birds were affected by the variable-light intensity lighting program. Expression of tryptophan hydroxylase 2 in the DRN and VTA of variable-light treated birds was lower than that of 5-lx- and 20-lx-treated birds on day 42 (p < 0.05). Higher expression of VTA-TH in 5-lx-treated birds than that in 20-lx-, NL-, and variable-light-treated birds suggests the high stress-susceptibility of 5-lx treated birds. Lower VTA-GR expression in 20-lx- and variable-light-treated birds indicates lower stress than that in NL- and 5-lx-treated birds (p < 0.05). The VTA-BDNF expression of NL-treated birds was 2.5 fold higher than that of 5-lx-, 20-lx-, and variable-light-treated birds (p < 0.05), and variable-light-treated birds showed the lowest level of BDNF expression (p < 0.05), suggesting the chronic social defeat stress in NL-treated birds. The result of VTA-Opn4 expression on day 42 suggests the possible role of VTA-Opn4 in broiler welfare through central light perception. Taken together, the variable-light intensity lighting program increased volunteer natural behaviors and physical activity, which may improve footpad condition and leg health of birds, consequently. Performance data including the increased daily weight gain and the lowered feed conversion ratio and results of brain welfare indicator gene expression showed the beneficial effect of the variable-light intensity lighting program on the performance and welfare of commercial broilers.

Effects of a variable light intensity lighting program on the welfare and performance of commercial broiler chickens

Our previous variable-light intensity lighting program studies indicate the light intensity preference behavior of broilers for their daily activity including eating and resting. To evaluate the effects of variable-light intensity lighting program on performance and welfare of broilers, four commercial trials were conducted for looking at behaviors, mortality, leg-health, performance, and brain welfare indicator genes including tryptophan hydroxylase 2 and tyrosine hydroxylase (TH), glucocorticoid receptor (GR), brain-derived neurotropic factor (BDNF), and melanopsin (Opn4) gene expression. One-day-old broilers were housed in four commercial broiler houses. Each quadrant (section) of the house was placed with 4,800 chicks. A total of four lighting programs began on day 7 with 5 lux (lx), 20 lx, natural light (NL, 480 lx), and variable light (2-5/40 lx) using LED lights on a 16L:8D photoperiod. In the variable-light house, the number of dustbathing holes was significantly higher than that in natural-light houses and 5-lx and 20-lx houses. Daily physical activities, footpad condition, fear response to novel objects, body weight, feed conversion ratio, and the number of leg-problem induced culled birds were affected by the variable-light intensity lighting program. Expression of tryptophan hydroxylase 2 in the DRN and VTA of variable-light treated birds was lower than that of 5-lx- and 20-lx-treated birds on day 42 (p < 0.05). Higher expression of VTA-TH in 5-lx-treated birds than that in 20-lx-, NL-, and variable-light-treated birds suggests the high stress-susceptibility of 5-lx treated birds. Lower VTA-GR expression in 20-lx- and variable-light-treated birds indicates lower stress than that in NL- and 5-lx-treated birds (p < 0.05). The VTA-BDNF expression of NL-treated birds was 2.5 fold higher than that of 5-lx-, 20-lx-, and variable-light-treated birds (p < 0.05), and variable-light-treated birds showed the lowest level of BDNF expression (p < 0.05), suggesting the chronic social defeat stress in NL-treated birds. The result of VTA-Opn4 expression on day 42 suggests the possible role of VTA-Opn4 in broiler welfare through central light perception. Taken together, the variable-light intensity lighting program increased volunteer natural behaviors and physical activity, which may improve footpad condition and leg health of birds, consequently. Performance data including the increased daily weight gain and the lowered feed conversion ratio and results of brain welfare indicator gene expression showed the beneficial effect of the variable-light intensity lighting program on the performance and welfare of commercial broilers.

Exploring the association between microbiota and behaviour in suckling piglets

It is increasingly recognised that the microbes residing in the gastrointestinal tract can influence brain physiology and behaviour, via the microbiota-gut-brain axis. Here, we made a first explorative evaluation at the association between the gut microbiota and behaviour in suckling piglets. 16S microbiota profiling information was obtained from two independent replicate experiments at 2 and 4 weeks of age. Piglets underwent a backtest to assess their personality or coping style at 2 weeks of age, and were subjected to a combined open field and novel object test at 3.5 weeks of age, recording anxiety-related and exploratory behaviour. The number of squeals vocalised during the open field test was associated with microbial groups such as Coprococcus 3 and CAG-873, whereas in the novel object test, explorative behaviour was significantly associated with microbial genera like Atopobium and Prevotella. Overall, this study explores the microbiota-behavioural relation by employing multivariate analysis and exemplifies the importance of individualised analyses when evaluating such relationships.

Assessing the Effectiveness of Providing Live Black Soldier Fly Larvae (Hermetia illucens) to Ease the Weaning Transition of Piglets

Weaning is a stressful event for piglets, involving substantial changes to their nutritional and social environment. Providing edible enrichment around weaning may ease the weaning transition by increasing pre-weaning feed intake and improving post-weaning performance, health, behavior, and affective state. In this study, we investigated the effects of providing live black soldier fly larvae (BSFL) as edible enrichment pre- and/or post-weaning. Pre-weaning, piglets received either only creep feed (Pre-C, n = 14 litters) or creep feed and live BSFL (Pre-L, n = 15 litters) ad libitum, and post-weaning piglets either had no access to live BSFL (Post-C, n = 24 pens) or they could rotate tubes that released BSFL (Post-L, n = 24 pens) at levels up to 20% of their expected daily dry matter intake, resulting in treatments CC, CL, LC, and LL. No interaction between pre- and post-weaning treatment was found for any of the measured parameters. Before weaning, Pre-L piglets preferred to interact with larvae over creep feed, and Pre-C piglets interacted more with creep feed than Pre-L piglets. Total time spent on feed-directed behaviors did not differ. Continuous larvae provisioning increased caecum length and proximal stomach digesta pH, while it decreased the passage of glucose and fluorescein isothiocyanate through the colon wall on d3 post-weaning (CC vs. LL, n = 12 piglets/treatment). Post-weaning diarrhea and final body weight were not affected by treatment. After weaning, Pre-C piglets tended to eat more and grew marginally faster than Pre-L piglets. Post-C piglets spent more time eating and had a higher feed intake post-weaning than Post-L piglets. Based on home-pen behavioral observations, Post-L piglets actively explored and ate the larvae. Post-C piglets spent more time on exploring the environment and nosing pen mates, and they spent more time on manipulating pen mates on d8 and played more on d8 & 15 compared to Post-L piglets. Piglet responses to a novel environment and an attention bias test on d4 & 5 post-weaning were not influenced by larvae provisioning. In conclusion, pre-weaning larvae provisioning did not improve pre-weaning feed intake and post-weaning performance, however post-weaning larvae provisioning did benefit piglet behavior as less manipulation of pen mates was observed.

Evaluation of miRNA as Biomarkers of Emotional Valence in Pigs

Simple Summary

It is widely recognized that the assessment of animal welfare should include measures of positive emotional (affective) state. Existing behavioral and physiological indicators of a positive affective state frequently lack sensitivity, objectivity or are unsuitable in a production environment. Therefore, there is a need to develop new approaches to accurately and objectively measure a positive emotional state in animals, including novel molecular markers such a miRNA. These biomarkers must be measurable in the peripheral circulation and provide an accurate account of the physiological and molecular activity in regions of the brain associated with emotional processing. Further, such markers require validation against established behavioral and physiological indices. Here we investigated the efficacy of circulating miRNA as biomarkers of emotional state in the pig.

Abstract

The ability to assess the welfare of animals is dependent on our ability to accurately determine their emotional (affective) state, with particular emphasis being placed on the identification of positive emotions. The challenge remains that current physiological and behavioral indices are either unable to distinguish between positive and negative emotional states, or they are simply not suitable for a production environment. Therefore, the development of novel measures of animal emotion is a necessity. Here we investigated the efficacy of microRNA (miRNA) in the brain and blood as biomarkers of emotional state in the pig. Female Large White × Landrace pigs (n = 24) were selected at weaning and trained to perform a judgment bias test (JBT), before being exposed for 5 weeks to either enriched (n = 12) or barren housing (n = 12) conditions. Pigs were tested on the JBT once prior to treatment, and immediately following treatment. MiRNA and neurotransmitters were analyzed in blood and brain tissue after euthanasia. Treatment had no effect on the outcomes of the JBT. There was also no effect of treatment on miRNA expression in blood or the brain (FDR p > 0.05). However, pigs exposed to enriched housing had elevated dopamine within the striatum compared to pigs in barren housing (p = 0.02). The results imply that either (a) miRNAs are not likely to be valid biomarkers of a positive affective state, at least under the type of conditions employed in this study, or (b) that the study design used to modify affective state was not able to create differential affective states, and therefore establish the validity of miRNA as biomarkers.

Effect of short-term high tryptophan diet fed to sows on their subsequent piglet behavior

Housing sows in groups create the challenge of decreasing fighting amongst sows. One proposed method to do so is to feed a high tryptophan diet, but the effect on the fetus is unknown. To investigate this, 66 sows were fed one of three diets: Control (0.14% SID tryptophan), Medium (0.28% SID tryptophan), or High (0.42% SID tryptophan), from days 28 to 35 of gestation. Sows gestated in standard gestation stalls. Blood samples were taken on day 27 prior to and on day 35 after tryptophan supplementation. On days 1, 2, and 3, nursing bouts were observed so as to record disputes and displacements from teat competition. The piglets' activity and fighting were recorded on days 3, 7, and 11 from 0700 to 1700 h. On day 12, four piglets per litter were blood sampled: two to be used in later behavior tests and two to act as controls for blood cortisol levels. On day 14, the two behavior test piglets from each litter were subjected to a 10-min Isolation Test and 5-min Human Approach Test. On day 15, the behavior test piglets were paired by sex and treatment (for example, a male Medium piglet paired with another male Medium piglet from a different crate) and each pair was subjected to a 10-min Social Challenge Test and immediately blood sampled. Piglet cortisol and serotonin did not differ among treatments (P > 0.10). There were no differences (P > 0.10) for number born (12.7 ± 0.4), born alive (11.7 ± 0.4), or mortality (1.1 ± 0.2). Behavior during nursing bouts was similar, with no treatment differences in number of disputes or displacements, and similar bout lengths among treatments (199.5 ± 4.6 s, P > 0.10). No differences were detected for any of the variables for Isolation or the Human Approach Tests (P > 0.10). During the Social Challenge Test, High piglets had more contacts approaching the head of the companion piglet than did either Medium or Control piglets (14.3 ± 1.1, 10.7 ± 1.1, and 9.69 ± 0.8, respectively, P < 0.02). Total number of aggressive interactions during the test tended to be greater for Medium piglets compared to High piglets (9.3 ± 1.5 vs 5.1 ± 0.9, P < 0.07). Time budget data of the litter indicate that piglets from all three treatments spent equal amounts of time active and inactive (P > 0.10). Aggression was low with 0.3 ± 0.04% of piglets displaying aggressive behavior. Feeding high concentrations of tryptophan for a short duration early in gestation does not have a negative impact on sows' subsequent offspring.

Providing live black soldier fly larvae (Hermetia illucens) improves welfare while maintaining performance of piglets post-weaning

During weaning, piglets experience concurrent social, physical, and nutritional stressors. Consequently, piglets often have poor feed intake and display increased oral manipulative behaviours post-weaning, indicative of compromised welfare. Black soldier fly larvae (BSFL) possess many attractive properties for pigs and could therefore function as effective edible enrichment, potentially alleviating weaning stress by facilitating exploration and promoting feed intake. In this study, pairs of piglets received a small amount of either live BSFL or wood shavings (8 pens/treatment) scattered throughout the pen twice a day for 11 days after weaning. Home-pen behaviour was scored by instantaneous scan sampling on day 2, 5 and 8, and behavioural responses to a novel environment and novel object were scored on day 10/11. Performance-related parameters were observed regularly. Larvae provisioning increased floor-directed exploration and decreased object-directed exploration, pig-directed oral manipulation, fighting and eating of pellets, and reduced neophobia towards a novel object. Pellet intake was significantly decreased by BSFL provisioning during day 4-11 post-weaning, although feed and net energy intake including BSFL never differed between treatments. BSFL provisioning did not influence piglet growth, feed efficiency, energy efficiency, and faecal consistency. To conclude, live BSFL provisioning positively affected post-weaning piglet behaviour while maintaining performance.

Serotonin and Tryptophan Serum Concentrations in Shelter Dogs Showing Different Behavioural Responses to a Potentially Stressful Procedure

In mammals, serotonin (5-HT) levels depend on the availability of tryptophan (TRP). Low 5-HT concentrations have been linked to behavioural disorders in dogs. This study aimed at investigating possible differences in dogs’ serum TRP and 5-HT concentrations according to their behavioural response to a potentially stressful procedure. Thirty-nine physically healthy shelter dogs, 15 females and 24 males, mean age = 5.6 years, were categorized by a certified veterinary behaviourist according to their behavioural response to medical examination and blood collection, in: relaxation, stress signals, tension without growling, tension with growling, escape attempts, and aggression attempts. Extraction and quantification of 5-HT and TRP were performed using a HLPC method. Data were statistically analysed, applying Chi-square and Spearman tests. Results showed no significant difference in TRP (χ² = 2.084, p = 0.555) nor 5-HT (χ² = 0.972, p = 0.808) serum concentrations among different categories of dogs; however, some categories were underrepresented (relaxation = 20.5%, stress signals = 30.8%, tension without growling = 43.6%, tension with growling = 5.1%, escape attempts = 0%, aggression attempts = 0%). No correlation between serum TRP and 5-HT concentrations was found (ρ = 0.086, p = 0.602). Serum 5-HT levels do not seem to be associated with dogs’ behavioural response to a stressful situation nor with serum TRP concentrations. The relationship between serum TRP and 5-HT concentrations and behaviour needs further research.

A Proposed Role for Pro-Inflammatory Cytokines in Damaging Behavior in Pigs

Sickness can change our mood for the worse, leaving us sad, lethargic, grumpy and less socially inclined. This mood change is part of a set of behavioral symptoms called sickness behavior and has features in common with core symptoms of depression. Therefore, the physiological changes induced by immune activation, for example following infection, are in the spotlight for explaining mechanisms behind mental health challenges such as depression. While humans may take a day off and isolate themselves until they feel better, farm animals housed in groups have only limited possibilities for social withdrawal. We suggest that immune activation could be a major factor influencing social interactions in pigs, with outbreaks of damaging behavior such as tail biting as a possible result. The hypothesis presented here is that the effects of several known risk factors for tail biting are mediated by pro-inflammatory cytokines, proteins produced by the immune system, and their effect on neurotransmitter systems. We describe the background for and implications of this hypothesis.

Influence of toys on behavioural patterns of pigs and their association with the concentration of serotonin in blood plasma

Improvement of welfare of piglets is one of the key factors which underlie the effectiveness of producing pork and the profitability of pig farming. This article offers a solution to the main industrial problem – creation of comfortable maintenance conditions for pigs using toys which satisfy their ethological needs. Piglets used in the experiment were kept in the swine complex of agricultural production of Agrofirm Mig-Service-Agro Cooperative in Novoodesky district of Mykolaiv Oblast (Ukraine). The objective of the study was assessment of the effect of toys on the behaviour of piglets, level of concentration of hormone serotonin in blood plasma and their energy of growth. The experiment was performed on 120 weaned piglets aged 28 days, which were divided according to the principle of analogues with 60 individuals in each group: I – the control group, the animals were kept with no toys; II – the experimental group, where the animals had toys. During the experiment chronometric monitoring of the piglets’ behavioural acts was carried out using video observation, we extracted blood samples for determination of the content of the hormone serotonin using the method of highly-efficient fluid chromatography and assessed the growth of the piglets. After the end of the experiment, we determined that the presence of toys reduced the intragroup aggression, which was accompanied by decrease in the duration of fights and almost three-fold increase in playing behaviour. Among piglets which had access to toys, the number of individuals observed to bite tails and ears decreased from 11 to 3. In the period of the study, the concentration of serotonin in the blood plasma of piglets who had free access to toys was 10 times higher compared with animals of the control group. Change in the behaviour patterns among the animals of the experimental group led to significant differences regarding the parameters of growth, where probable increase in the live weight at the age of 90 days was observed, which was associated with significant increase in their mean daily weight gain compared with the animals of the control group. This study confirms that use of toys for piglets during growth completion can prevent features of aggression and abnormal forms of stereopathy within groups, increase the live weight and mean daily weight gain and improve emotional condition, which affects the welfare of pigs.

Effects of light intensity and dual light intensity choice on plasma corticosterone, central serotonergic and dopaminergic activities in birds, Gallus gallus

Light intensity plays an important role in the regulation of growth, behavior, reproduction, and welfare of avian species. Light intensity preference behavior has been suggested to be involved in welfare of birds. This study aims to investigate the effects of different light intensity and dual light intensity choice (DLIC) lighting program on plasma corticosterone (CORT), and tryptophan hydroxylase 2 (TPH2, the rate-limiting enzyme of serotonin biosynthesis) and tyrosine hydroxylase (TH, the rate-limiting enzyme of dopamine biosynthesis) gene expression in the brainstem of male chickens. Day old broilers were housed in two commercial houses, and placed in 24 pens. All the treatment groups were provided with 23 h light (L) /1 h dark (D) and 30 lx (lx) light intensity during the first week and then 18L:6D (10 lx) from day 7 to 14. Blood and brain were sampled at 14 days of age (10 lx) before the onset of light treatments. On day 15, four treatments (2, 10, 20, and 100 lx), and DLIC treatment (2/20 lx) were initiated. Samples were collected on days 15, 16, 17, 30 and 41. TPH2 expression in the dorsal raphe nucleus (DRN) and caudal raphe nucleus (CRN) of brainstem, and TPH2 and TH expression in ventral tegmental areas (VTN) of the midbrain were determined by qPCR. Results showed that bright light and DLIC lighting program temporarily attenuated plasma CORT, suggesting the short-term stress attenuating effect of bright light and DLIC lighting program. Differential TPH2 expression in the DRN and CRN observed in the DLIC birds indicate a significant effect of DLIC lighting program on the serotonergic activity in the avian brainstem. At the 41 days of age, the significant downregulation of TPH2 and TH expression occurred in the VTA of DLIC treated birds compared to the other group of birds. Taken together, temporal and spatial regulation of TPH2 and TH expression by DLIC lighting program indicate that compensatory regulation of serotonergic and dopaminergic activities might be involved in the light intensity preference behavior of birds, suggesting a possible beneficial effect of the DLIC lighting program on broiler welfare.

Indirect Genetic Effects for Growth in Pigs Affect Behaviour and Weight Around Weaning

Selection for indirect genetic effects (IGE), i.e. the genetic effect of an individual on a trait of another individual, is a promising avenue to increase trait values in plant and animal breeding. Studies in livestock suggest that selection for IGE for growth (IGEg) might increase animals' capacity to tolerate stress. We assessed the effect of a stressful phase (weaning) on the behaviour and performance of pigs (n = 480) divergently selected for high or low IGEg. High IGEg pigs were significantly slower to explore the feed and gained less weight than low IGEg pigs in the days after weaning. In line with previous findings, high IGEg animals may have prioritized the formation of social ranks.

Vocal correlates of emotional reactivity within and across contexts in domestic pigs (Sus scrofa)

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.

Effect of handling on neurotransmitter profile in pig brain according to fear related behaviour

Chemical neurotransmitters (NT) are principal actors in all neuronal networks of animals. The central nervous system plays an important role in stress susceptibility and organizes the response to a stressful situation through the interaction of the dopaminergic and the serotonergic pathways, leading to the activation of the hypothalamus-pituitary-adrenal axis (HPA). This study was designed to investigate: a) the effects of stressful handling of pigs at the slaughterhouse on the neurotransmitter profile in four brain areas: amygdala, prefrontal cortex (PFC), hippocampus and hypothalamus, and b) whether the alterations in the brain NT profile after stressful handling were associated with fear, determined by the tonic immobility (TI) test. In the first place, the characterization of the NT profile allowed to distinguish the four brain areas in a principal component analysis. The most crucial pathway involved in the reaction of pigs to a stressful handling was the serotonergic system, and changes were observed in the amygdala with a decrease in serotonin (5-HT) and total indoleamines, and in the hippocampus, where this pathway was activated. Fearful and non-fearful pigs did not show significant differences in their NT profile in control conditions, but when subjected to a stressful handling in the slaughterhouse, fearful animals showed a significant variation in the serotonin pathway and, in a lesser extent, the dopamine (DA) pathway. In conclusion, the existence of an underlying biological trait - possibly fearfulness - may be involved in the pig's response toward stressful challenges, and the serotonergic system seems to play a central role in this response.

Omnivores Going Astray: A Review and New Synthesis of Abnormal Behavior in Pigs and Laying Hens

Pigs and poultry are by far the most omnivorous of the domesticated farm animals and it is in their nature to be highly explorative. In the barren production environments, this motivation to explore can be expressed as abnormal oral manipulation directed toward pen mates. Tail biting (TB) in pigs and feather pecking (FP) in laying hens are examples of unwanted behaviors that are detrimental to the welfare of the animals. The aim of this review is to draw these two seemingly similar abnormalities together in a common framework, in order to seek underlying mechanisms and principles. Both TB and FP are affected by the physical and social environment, but not all individuals in a group express these behaviors and individual genetic and neurobiological characteristics play an important role. By synthesizing what is known about environmental and individual influences, we suggest a novel possible mechanism, common for pigs and poultry, involving the brain-gut-microbiota axis.

Perinatal Exposure to a Diet High in Saturated Fat, Refined Sugar and Cholesterol Affects Behaviour, Growth, and Feed Intake in Weaned Piglets

The increased consumption of diets high in saturated fats and refined sugars is a major public health concern in Western human societies. Recent studies suggest that perinatal exposure to dietary fat and/or sugar may affect behavioural development. We thus investigated the effects of perinatal exposure to a high-fat high-sugar diet (HFS) on behavioural development and production performance of piglets. Thirty-two non-obese sows and their piglets were allocated to 1 of 4 treatments in a 2 × 2 factorial design, with 8-week prenatal (gestation) and 8-week postnatal (lactation and post-weaning) exposure to a HFS diet (12% saturated fat, 18.5% sucrose, 1% cholesterol) or control low-fat low-sugar high-starch diets as factors. From weaning onwards (4 weeks of age), piglets were housed in group of 3 littermates (n = 8 groups/treatment) and fed ad libitum. After the end of the dietary intervention (8 weeks of age), all the piglets were fed a standard commercial diet. Piglet behaviours in the home pens were scored, and skin lesions, growth, feed intake and feed efficiency were measured up to 8 weeks after the end of the dietary treatment, i.e. until 16 weeks of age. At the end of the dietary treatment (8 weeks of age), response to novelty was assessed in a combined open field and novel object test (OFT/NOT). During the weeks following weaning, piglets fed the postnatal HFS diet tended to be less aggressive (p = 0.06), but exhibited more oral manipulation of pen mates (p = 0.05) than controls. Compared to controls, piglets fed the prenatal or postnatal HFS diet walked more in the home pen (p ≤ 0.05), and tended to have fewer skin lesions (p < 0.10). Several behavioural effects of the postnatal HFS diet depended on the prenatal diet, with piglets subjected to a switch of diet at birth being more active, and exploring feeding materials, pen mates, and the environment more than piglets that remained on the same diet. Behaviours during the OFT/NOT were not affected by the diet. The intake of the postnatal HFS diet drastically reduced feed intake, but improved feed efficiency up to 8 weeks after the end of the dietary intervention, i.e. 16 weeks of age (p < 0.0001 for both). Our study highlights the key role of prenatal and postnatal nutritional interactions for early behavioural development, and reveals programming effects of early life nutrition on voluntary feed intake of piglets later in life.

A study of blood serotonin and serotonin transporter promoter variant (5-HTTLPR) polymorphism in Egyptian autistic children

Background:

Autism spectrum disorder (ASD) is a complex, heterogeneous neurodevelopmental disorder with onset during early childhood. Most studies have reported an elevation in platelet serotonin in persons with autism. The serotonin (5-hydroxytryptamine; 5-HT) transporter in the brain uptakes 5-HT from extracellular spaces. It is also present in platelets, where it takes up 5-HT from plasma. Polymorphisms in serotonin transporter gene (SLC6A4) were frequently studied in many neuropsychiatric disorders.

Materials and Methods:

We have measured the plasma 5-HT levels in 20 autistic male children and 20 control male children by the enzyme-linked immunosorbent assay (ELISA) method. In addition, the SLC6A4 promoter region (5-HTTLPR) insertion/deletion (I/D) polymorphism was studied, using whole genomic DNA.

Results:

Plasma serotonin was significantly low in autistic children compared to control (P = 0.001), although correlation to severity of autism was not significant. The frequency of short (S) allele in autism cases was 10% and in the control group it was absent.

Conclusion:

Our study demonstrated an increased prevalence of 5-HTTLPR S allele in autism subjects. Significantly decreased plasma serotonin was detected in autism subjects, with no significant relationship between 5-HTTLPR genotype and plasma 5-HT being evident.

Monoamine oxidase A gene promoter methylation and transcriptional downregulation in an offender population with antisocial personality disorder

BACKGROUND

Antisocial personality disorder (ASPD) is characterised by elevated impulsive aggression and increased risk for criminal behaviour and incarceration. Deficient activity of the monoamine oxidase A (MAOA) gene is suggested to contribute to serotonergic system dysregulation strongly associated with impulsive aggression and antisocial criminality.

AIMS

To elucidate the role of epigenetic processes in altered MAOA expression and serotonin regulation in a population of incarcerated offenders with ASPD compared with a healthy non-incarcerated control population.

METHOD

Participants were 86 incarcerated participants with ASPD and 73 healthy controls. MAOA promoter methylation was compared between case and control groups. We explored the functional impact of MAOA promoter methylation on gene expression in vitro and blood 5-HT levels in a subset of the case group.

RESULTS

Results suggest that MAOA promoter hypermethylation is associated with ASPD and may contribute to downregulation of MAOA gene expression, as indicated by functional assays in vitro, and regression analysis with whole-blood serotonin levels in offenders with ASPD.

CONCLUSIONS

These results are consistent with prior literature suggesting MAOA and serotonergic dysregulation in antisocial populations. Our results offer the first evidence suggesting epigenetic mechanisms may contribute to MAOA dysregulation in antisocial offenders.

Tail biting in pigs: blood serotonin and fearfulness as pieces of the puzzle?

Tail biting in pigs is a widespread problem in intensive pig farming. The tendency to develop this damaging behaviour has been suggested to relate to serotonergic functioning and personality characteristics of pigs. We investigated whether tail biting in pigs can be associated with blood serotonin and with their behavioural and physiological responses to novelty. Pigs (n = 480) were born in conventional farrowing pens and after weaning at four weeks of age they were either housed barren (B) or in straw-enriched (E) pens. Individual pigs were exposed to a back test and novel environment test before weaning, and after weaning to a novel object (i.e. bucket) test in an unfamiliar arena. A Principal Component Analysis on behaviours during the tests and salivary cortisol (novel object test only) revealed five factors for both housing systems, labeled ‘Early life exploration’, ‘Near bucket’, ‘Cortisol’, ‘Vocalizations & standing alert’, and ‘Back test activity’. Blood samples were taken at 8, 9 and 22 weeks of age to determine blood platelet serotonin. In different phases of life, pigs were classified as tail biter/non-tail biter based on tail biting behaviour, and as victim/non-victim based on tail wounds. A combination of both classifications resulted in four pig types: biters, victims, biter/victims, and neutrals. Generally, only in phases of life during which pigs were classified as tail biters, they seemed to have lower blood platelet serotonin storage and higher blood platelet uptake velocities. Victims also seemed to have lower blood serotonin storage. Additionally, in B housing, tail biters seemed to consistently have lower scores of the factor ‘Near bucket’, possibly indicating a higher fearfulness in tail biters. Further research is needed to elucidate the nature of the relationship between peripheral 5-HT, fearfulness and tail biting, and to develop successful strategies and interventions to prevent and reduce tail biting.