Variations in the Behavior of Pigs During an Open Field and Novel Object Test

Investigating the correlation between phenotypes, adrenal transcriptome, and serum metabolism in laying ducks exhibiting varying behaviours under the same stressor

Laying ducks in cage environments face various stressors, including the fear of novelty, which negatively affects their behaviour and performance. The reasons behind the variation in behaviour under identical stress conditions are not well understood. This study investigated how different behaviours affect production performance, immune response, antioxidant capabilities, adrenal gene expression, and serum metabolite profiles in caged laying ducks subjected to the same stressor. Overall, 42-week-old laying ducks (N = 300) were selected, fed for 60 days, and simultaneously underwent behavioural tests. Based on their behavioural responses, 24 ducks were chosen and categorised into two groups: high-active avoidance (HAA) and low-active avoidance (LAA). The study utilised phenotypic, genetic, and metabolomic analyses, coupled with bioinformatics, to identify crucial biological processes, genes, and metabolites. The results indicated that ΔW (BW gain) and average daily egg weight (ADEW) were significantly lower in the HAA group compared to the LAA group (P < 0.05). By contrast, the feed-to-egg ratio was higher in the HAA group than in the LAA group (P < 0.05). Levels of serum immunoglobulin A, total antioxidant capacity, and the activities of enzymes like superoxide dismutase and catalase (CAT) were significantly lower in the HAA than in the LAA group (P < 0.05), whereas serum ACTH levels were significantly higher in HAA than in the LAA group (P < 0.05). The adrenal transcriptome analysis revealed 148 differentially expressed genes in the HAA group, with 97 up-regulated and 51 down-regulated. Moreover, enrichment analysis highlighted significant differences in two metabolic pathways: neuroactive ligand-receptor interaction and oxidative phosphorylation (P < 0.05). Serum metabolomics identified 11 differentially accumulated metabolites between the groups, with variations in up and down-regulation. Integrative analysis of phenotype, transcriptome, and metabolome data showed a strong correlation between the exosome component 3 (EXOSC3) gene, phenotypic traits, and differential metabolites. Thus, we deduced that the differences in average daily egg weight among ducks could be linked to variations in gabapentin and EXOSC3 gene expressions, affecting serum CAT levels.

Open field test for the assessment of anxiety-like behavior in Gnathonemus petersii fish

The open field test (OFT) is a basic and most widely used test for investigation in animal studies of the neurobiological basis of anxiety and screening for novel drug targets. Here, we present the results of an OFT for weakly electric fish Gnathonemus petersii. This study aimed to describe the behavioral response of G. petersii exposed to an OFT, simultaneously with an evaluation of electrical organ discharges (EOD), to determine whether any association between EOD and patterns of motor behavior in the OFT exists. Treatment of OFT activity and its temporal patterning was assessed for the whole 6-min trial as well as per-minute distributions of activity using a near-infrared camera and an EOD data acquisition system. Our results demonstrated that the time spent, distance moved, and time of activity were significantly higher in the periphery of the OFT arena. The zone preference pattern over the 6-min test session showed that G. petersii prefer the outer zone (83.61%) over the center of the arena (16.39%). The motor behavior of fish measured as distance moved, active time, and swim speed were correlated with the number of EODs; however, no relationship was found between EOD and acceleration.

A 24-h restraint with food and water deprivation: a potential method to establish a model of depression in pigs

Adverse stress, such as the long-term restriction of food intake and activity in intensive production, leads to a depression-like mental state in sows. Mood disorder, such as depression, is a widely concerned animal welfare issue. However, little is known about the biological mechanisms that underlie mood disorders in pigs. This study is the first attempt to establish a pig depression model by acute stress. A total of 16 adult Bama pigs were divided into the control and model groups, with 8 pigs (half male and half female) per group. The pigs in the model group were restrained for 24 h in a dark and ventilated environment, with food and water deprivation. After the restraint, behavioral tests (feed intake, sucrose preference test, open field test, and novel object test) were used to evaluate apparent indicators. The levels of COR and ACTH in the serum and the levels of 5-HT, NE, and BDNF in the hippocampus and medial prefrontal cortex were detected using ELISA to identify the physiological state. After acute stress, pigs exhibited decreased feed intake and sucrose preference, increased serum COR levels, decreased hippocampal 5-HT levels, and exhibited more fear. Finally, the model was evaluated according to the weight of the test indicators. The overall score of the model was 0.57, indicating that modeling was feasible. Although the reliability and stability require further verification, this novel model revealed typical depression-like changes in behavior and provided a potential method to establish a model of depression in pigs.

The Pig as a Translational Animal Model for Biobehavioral and Neurotrauma Research

In recent decades, the pig has attracted considerable attention as an important intermediary model animal in translational biobehavioral research due to major similarities between pig and human neuroanatomy, physiology, and behavior. As a result, there is growing interest in using pigs to model many human neurological conditions and injuries. Pigs are highly intelligent and are capable of performing a wide range of behaviors, which can provide valuable insight into the effects of various neurological disease states. One area in which the pig has emerged as a particularly relevant model species is in the realm of neurotrauma research. Indeed, the number of investigators developing injury models and assessing treatment options in pigs is ever-expanding. In this review, we examine the use of pigs for cognitive and behavioral research as well as some commonly used physiological assessment methods. We also discuss the current usage of pigs as a model for the study of traumatic brain injury. We conclude that the pig is a valuable animal species for studying cognition and the physiological effect of disease, and it has the potential to contribute to the development of new treatments and therapies for human neurological and psychiatric disorders.

Exposure to a sensory functional ingredient in the pig model modulates the blood-oxygen-level dependent brain responses to food odor and acute stress during pharmacological MRI in the frontostriatal and limbic circuits

Introduction

In the present study, we examined the effects of a supplementation with a sensory functional ingredient (FI, D16729, Phodé, France) containing vanillin, furaneol, diacetyl and a mixture of aromatic fatty acids on the behavioural and brain responses of juvenile pigs to acute stress.

Methods

Twenty-four pigs were fed from weaning with a standard granulated feed supplemented with the functional ingredient D16729 (FS animals, N = 12) or a control formulation (CT animals, N = 12). After a feed transition (10 days after weaning), the effects of FI were investigated on eating behaviour during two-choice feed preference tests. Emotional reactivity to acute stress was then investigated during openfield (OF), novel suddenly moving object (NSO), and contention tests. Brain responses to the FI and the two different feeds' odour, as well as to an acute pharmacological stressor (injection of Synacthen®) were finally investigated with functional magnetic resonance imaging (fMRI).

Results

FS animals tended to spend more time above the functional feed (p = 0.06) and spent significantly more time at the periphery of the arena during NSO (p < 0.05). Their latency to contact the novel object was longer and they spent less time exploring the object compared to CT animals (p < 0.05 for both). Frontostriatal and limbic responses to the FI were influenced by previous exposure to FI, with higher activation in FS animals exposed to the FI feed odor compared to CT animals exposed to a similarly familiar feed odor without FI. The pharmacological acute stress provoked significant brain activations in the prefrontal and thalamic areas, which were alleviated in FS animals that also showed more activity in the nucleus accumbens. Finally, the acute exposure to FI in naive animals modulated their brain responses to acute pharmacological stress.

Discussion

Overall, these results showed how previous habituation to the FI can modulate the brain areas involved in food pleasure and motivation while alleviating the brain responses to acute stress.

Novel saliva biomarkers for stress and infection in pigs: Changes in oxytocin and procalcitonin in pigs with tail-biting lesions

There is a need for feasible and reliable measures to improve and evaluate production animal health and welfare. Oxytocin is a promising novel stress-related biomarker and procalcitonin may be a measure of sepsis. Both have potential for use in pigs and can be measured from saliva, which allows on-farm sampling with minimal impact on the animals. The current study sought to further validate these measures using a spontaneous situation that causes both stress and an increased risk for infections in pigs, namely a tail-biting outbreak. Grower pigs on a commercial farm belonging to three different phenotype groups were selected: control pigs from control pens (CC, N = 30), control pigs (CTB, N = 10), and pigs with tail lesions from pens with a tail-biting outbreak (LTB, N = 27). A single sample of saliva was collected from each pig and analysed for a range of biomarkers related to stress, infection, inflammation, and immune activation. Oxytocin tended to be higher in CC pigs than in LTB pigs, while cortisol was higher in CTB than CC pigs. Procalcitonin tended to be higher, and haptoglobin was higher in LTB than in CC pigs. Adenosine-deaminase levels were similar between phenotypes. These results provide further evidence for the link between stress and tail biting, and indicate that tail-biting lesions are potential routes for systemic spread of bacteria. Further research into saliva oxytocin as a stress biomarker and saliva procalcitonin as a sepsis biomarker in pigs is warranted.

The Open Field Test as a Tool for Behaviour Analysis in Pigs: Recommendations for Set-Up Standardization - A Systematic Review

INTRODUCTION

The open field test (OFT) is a common tool to assess anxiety and behavioural changes in rodents. It has been adapted to pigs with no systematic investigation of how environmental changes may alter the performance of pigs. Currently, the number of published studies including the OFT in domestic pig models is increasing without standardization.

METHODS

Our review aimed to investigate the open field (OF) set-ups in published studies and the similarities between performance and published parameters.

RESULTS

Following the PRISMA guidelines for reviews, we selected 69 studies for inclusion in this systematic review. We determined the specific set-up conditions such as dimensions, duration, and time of day for most of the included studies; we found high variability across studies with respect to these test specifics.

DISCUSSION

Our results indicate the inconsistent implementation of the set-up, including dimensions, timing, parameters, and additional combined tests (e.g., new object tests). Based on our findings, we have made recommendations for the performance of the OFT, according to the current literature.

Multimodal characterization of Yucatan minipig behavior and physiology through maturation

Brain injuries induced by external forces are particularly challenging to model experimentally. In recent decades, the domestic pig has been gaining popularity as a highly relevant animal model to address the pathophysiological mechanisms and the biomechanics associated with head injuries. Understanding cognitive, motor, and sensory aspects of pig behavior throughout development is crucial for evaluating cognitive and motor deficits after injury. We have developed a comprehensive battery of tests to characterize the behavior and physiological function of the Yucatan minipig throughout maturation. Behavioral testing included assessments of learning and memory, executive functions, circadian rhythms, gait analysis, and level of motor activity. We applied traditional behavioral apparatus and analysis methods, as well as state-of-the-art sensor technologies to report on motion and activity, and artificial intelligent approaches to analyze behavior. We studied pigs from 16 weeks old through sexual maturity at 35 weeks old. The results show multidimensional characterization of minipig behavior, and how it develops and changes with age. This animal model may capitulate the biomechanical consideration and phenotype of head injuries in the developing brain and can drive forward the field of understanding pathophysiological mechanisms and developing new therapies to accelerate recovery in children who have suffered head trauma.

Like Mother Like Child: Do Fearful Sows Have Fearful Piglets?

Gestational and early life experiences affect subsequent behavioural and physical development. The objective of the current study was to investigate associations between gilts' fear of humans, gestational stress level, and feeding and maternal behaviour, as well as how these related to aspects of the personality and growth of their offspring. A total of 37 gilts were used. Four human approach tests were performed between d 104 and d 111 of gestation to classify gilts as fearful or friendly. Gilt feeding behaviour and salivary cortisol concentration was measured between d 90 and d 108 of gestation, and gilt nursing behaviour assessed at d 13 of lactation. Piglets were subject to a back test at d 13 of age, to an open field test and a human approach test at d 20 of age, and growth was monitored to weaning (d 26 of age). Gilts classified as having a fearful behavioural profile had higher cortisol levels than friendly gilts (p < 0.05). Human fear level did not affect reproductive performance or the growth of offspring (p > 0.05). The offspring of friendly gilts tended to have a more active response to the back test (p = 0.09), less freezing response in the open field test (p < 0.05), and received human contact more than piglets from fearful gilts (p < 0.05). The present study shows that gilt human fear level is linked to their stress levels, which can affect the personality of their piglets.

Welfare-Related Behaviors in Chickens: Characterization of Fear and Exploration in Local and Commercial Chicken Strains

Fear and exploration are crucial traits determining how animals behave in novel situations, and thus, they influence animal welfare. The aim of this study was the characterization of these behavioral traits among different strains to identify interesting alternatives for future poultry production. Whereas the Novel Object Test (NOT) focuses on fear and exploration of novel objects, the Avoidance Distance Test (ADT) addresses this in the context of humans. Here, a commercial hybrid line, a dual-purpose hybrid and a local adapted strain were tested. For the differences between strains and development of fear, Lohmann Brown (n = 714), Lohmann Dual (n = 844) and Rhinelander (n = 458) were observed weekly until maturity. Results show that fear and exploration towards unknown objects and humans are breed-specific (all p < 0.01). Additionally, development of fear in NOT and ADT differed between all three strains (both p < 0.01). The expressions of fear of humans or objects should be regarded as characteristics adapted for different husbandry systems and breeding goals, e.g., high exploratory behavior in aviary or high avoidance of predators in free-ranging husbandry or at least a balanced ratio between fear and exploration. Characterization of behavioral traits among different strains, understanding diversity and integrating these behaviors into future breeding and husbandry systems might reflect the need to preserve local strains and the potential to improve animal welfare.