Housing and road transport modify the brain neurotransmitter systems of pigs: Do pigs raised in different conditions cope differently with unknown environments?

How housing and transport conditions may affect welfare in porcine production is a leading topic in livestock research. This study investigated whether pigs present a different neurological response to management conditions and to ascertain whether pigs living partially outdoors cope differently with road transport-associated stress. Twenty-four female pigs were divided in two groups: one living indoors (ID, n = 12) and the other housed combining indoor conditions with 4 hours per day of outdoor pasture (OD, n = 12). After one month, one set of animals from each housing condition were driven in a truck to the slaughterhouse in low-stress conditions (5 min drive, no mixing groups, soft management, LS group, n = 12) or high-stress conditions (2 hours drive, mixing groups, harsh management, HS group, n = 12). At the slaughterhouse, blood was collected, and the prefrontal cortex (PFC) and the hippocampus (HC) dissected. OD pigs had lower serum haptoglobin and increased dopaminergic pathway (DA-system) in the PFC, suggesting that living outdoors increases their wellbeing. HS conditions increased serum creatine kinase (CK) and affected several brain pathways: activation of the noradrenergic (NA-system) and DA -system in the PFC and the activation of the DA-system and an increase in c-Fos as well as a decrease in brain-derived neurotrophic factor (BDNF) in the HC. The serotonergic system (5-HT-system) was mildly altered in both areas. There was an interaction between housing and transport in serum NA and the DA-system in the HC, indicating that living conditions affected the response to stress. Multivariate analysis was able to discriminate the four animal groups. In conclusion, this work indicates that housing conditions and road transport markedly modifies the neurophysiology of pigs, and suggests that animals raised partially outdoors respond differently to transport-associated stress than animals raised indoors, indicating that they cope differently with unknown environments.

Effects of genotype on hematological and serum biochemical responses of turkey hens to stress

Abstract. Stress accompanying animal production is both an indicator of welfare and a factor that affects economic parameters. Dynamic development of alternative poultry production systems such as outdoor, free range or ecological, strives to achieve best-quality products and to improve the living conditions of birds. Apart from the type and intensity of the external stimuli, the response to stress is determined genetically. Poultry rearing in the aforementioned systems requires selecting the appropriate genotype of birds, often including crosses of fast-growing and slow-growing lines. The objective of this study was to demonstrate differences in the physiological response to stress of fast-growing (FG) and slow-growing (SG) turkeys and their crosses: SF (SG  ×  FG) and FS (FG  ×  SG), based on hematological and biochemical blood analyses. Blood was sampled from 30 turkey hens from each of four genotypes, aged 14 weeks, subjected to standard pre-slaughter handling procedures. Compared to FG and FS turkeys, the SG and SF birds had a high total protein concentration, a higher heterophil (H) ∕ lymphocyte (L) ratio and a higher concentration of cortisol. In turn, the FG turkeys had the highest activity of enzymes: alanine transaminase, aspartate transaminase, lactate dehydrogenase, creatine kinase. Conversely, the FS turkeys had the highest concentrations of total cholesterol and low-density lipoprotein (LDLC) and the lowest concentration of cortisol. Significant positive effects of crossing were reported for total protein, cholinesterase and cortisol. Effects of crossbreeding on the percentage of H, concentrations of total cholesterol, and LDLC and activity of aspartate transaminase in blood of the crosses were significant but negative and more dependent on the sire line. Except for albumins, whose concentration in blood of crosses was higher compared to birds of pure lines, there were no advantages of heterosis. Negative heterosis was estimated for creatinine, the enzymes alanine transaminase and lactate dehydrogenase, and for cortisol. The most similar regarding creatinine, bilirubin, albumins, total protein, H, L and H ∕ L were the FS and SF groups. The greatest differences were in the following parameters: triglycerides, total cholesterol, high-density lipoprotein (HDLC), LDLC, glucose and lactate, which occurred between the pure lines of turkeys. Study results demonstrate various responses to stress in the analyzed groups of turkeys, with the level of stress measured with hematological and biological blood markers being mostly determined by additive genetic variation, and to a lesser extent by the maternal and sire effects.

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.

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

Pigs differ in their behavioural responses towards environmental challenges. Individual variation in maladaptive responses such as tail biting, may partly originate from underlying biological characteristics related to (emotional) reactivity to challenges and serotonergic system functioning. Assessing relations between behavioural responses and brain and blood serotonin parameters may help in understanding susceptibility to the development of maladaptive responses. The objective of the current study was, therefore, to assess the relationship between the pigs' serotonergic parameters measured in both blood and brain, and the behaviour of pigs during a novelty test. Pigs (n=31) were subjected to a novelty test at 11weeks of age, consisting of 5-min novel environment exposure after which a novel object (a bucket) was introduced for 5min. Whole blood serotonin, platelet serotonin level, and platelet serotonin uptake were determined at 13weeks of age. Levels of serotonin, its metabolite and serotonin turnover were determined at 19weeks of age in the frontal cortex, hypothalamus and hippocampus. The behaviour of the pigs was different during exposure to a novel object compared to the novel environment only, with more fear-related behaviours exhibited during novel object exposure. Platelet serotonin level and brain serotonergic parameters in the hippocampus were interrelated. Notably, the time spent exploring the test arena was significantly correlated with both platelet serotonin level and right hippocampal serotonin activity (turnover and concentration). In conclusion, the existence of an underlying biological trait - possibly fearfulness - may be involved in the pig's behavioural responses toward environmental challenges, and this is also reflected in serotonergic parameters.

The use of pigs in neuroscience: Modeling brain disorders

The use of pigs in neuroscience research has increased in the past decade, which has seen broader recognition of the potential of pigs as an animal for experimental modeling of human brain disorders. The volume of available background data concerning pig brain anatomy and neurochemistry has increased considerably in recent years. The pig brain, which is gyrencephalic, resembles the human brain more in anatomy, growth and development than do the brains of commonly used small laboratory animals. The size of the pig brain permits the identification of cortical and subcortical structures by imaging techniques. Furthermore, the pig is an increasingly popular laboratory animal for transgenic manipulations of neural genes. The present paper focuses on evaluating the potential for modeling symptoms, phenomena or constructs of human brain diseases in pigs, the neuropsychiatric disorders in particular. Important practical and ethical aspects of the use of pigs as an experimental animal as pertaining to relevant in vivo experimental brain techniques are reviewed. Finally, current knowledge of aspects of behavioral processes including learning and memory are reviewed so as to complete the summary of the status of pigs as a species suitable for experimental models of diverse human brain disorders.