Mind the ramp: Association between early life ramp use and spatial cognition in laying hen pullets

Ramps facilitate earlier access to complex environments and increase early life voluntary exercise, which may positively affect the cognitive development of chickens. This study focused on quantifying individual differences in ramp use and its impact on spatial cognition of laying hen pullets. Sixteen identical pens were housed with Lohmann Selected Leghorn (LSL) chicks of which eight chicks from each pen were colour marked from one day of age (DoA) to serve as focal birds. We quantified overall ramp use (walk/run, wing-assisted incline running, and jump/fly to and from ramps) by scan sampling recorded videos for 6, 10, 12, 20, 27, 41, and 55 DoA for all focal birds. From 56 to 95 DoA, long and short-term spatial memory of three focal birds per pen were assessed in a holeboard test in three consecutive phases: cued, uncued and reversal. Mixed model analysis showed that the spatial cognitive abilities of the birds were linked to differences in ramp use frequency averaged across all observation days. Birds with higher ramp use made fewer reference (Estimate ± Confidence Interval = 0.94 [0.88, 0.99], p = 0.08) and working memory errors (Est ± CI = 0.77 [0.59, 1.00], p = 0.06) in the cued phase than birds with lower ramp use. In contrast, birds with higher ramp use made more reference memory errors (Est ± CI = 1.10 [1.01, 1.20], p = 0.05) in the reversal phase. Birds with higher ramp use also made more reference memory errors compared to birds with lower ramp use as the phases changed from cued to uncued (p = 0.001). Our results indicate that there might be a relationship between early life ramp use and spatial cognition of laying hens.

The Effects of Social vs. Individual Housing of Zebrafish on Whole-Body Cortisol and Behavior in Two Tests of Anxiety

Two of the most used models of anxiety in zebrafish research, the novel tank-diving test (NTDT) and the black-white preference test (BWPT), are modifications of assays used in rodent research (open field test and light/dark test). There has been a thorough validation of these tests in rodents, but a similar level of knowledge is still missing in zebrafish. Adult zebrafish naturally live in shoals with conspecifics, and group housing is therefore assumed to be the optimal housing condition for zebrafish, as it allows for shoaling behavior. This study investigated how housing in social isolation affected whole-body cortisol and the behavioral responses in the NTDT and BWPT. We also examined the correlation between the behavioral responses in the two behavioral tests. We found that zebrafish housed in groups had significantly higher whole-body cortisol than individually housed zebrafish (F_{1, 85} = 25.51, P < 0.0001). Regardless of treatment, all groups had a general preference for the lower compartment in the NTDT and the black compartment in the BWPT. Individually housed zebrafish had a higher total number of entries to the white compartment in BWPT compared to group housed zebrafish when their first test was BWPT (F_{1, 48} = 5.79, P = 0.0201), but not when BWPT was their second behavioral test. Fish that had higher whole-body cortisol had a tendency toward fewer entries into the white compartment the first 3 min of the BWPT (F_{1, 48} = 3.90, P = 0.0540). There was no effect of housing on the behaviors registered in the NTDT. There was a positive correlation (correlation coefficient 0.40; p = 0.003) between transitions from black to white compartment in BWPT and transitions from lower to upper compartment in NTDT, but we did not find any association between duration in white compartment in BWPT and upper compartment in NTDT. Considering this, we suggest that further model validation is needed.

Classification of pig calls produced from birth to slaughter according to their emotional valence and context of production

Vocal expression of emotions has been observed across species and could provide a non-invasive and reliable means to assess animal emotions. We investigated if pig vocal indicators of emotions revealed in previous studies are valid across call types and contexts, and could potentially be used to develop an automated emotion monitoring tool. We performed an analysis of an extensive and unique dataset of low (LF) and high frequency (HF) calls emitted by pigs across numerous commercial contexts from birth to slaughter (7414 calls from 411 pigs). Our results revealed that the valence attributed to the contexts of production (positive versus negative) affected all investigated parameters in both LF and HF. Similarly, the context category affected all parameters. We then tested two different automated methods for call classification; a neural network revealed much higher classification accuracy compared to a permuted discriminant function analysis (pDFA), both for the valence (neural network: 91.5%; pDFA analysis weighted average across LF and HF (cross-classified): 61.7% with a chance level at 50.5%) and context (neural network: 81.5%; pDFA analysis weighted average across LF and HF (cross-classified): 19.4% with a chance level at 14.3%). These results suggest that an automated recognition system can be developed to monitor pig welfare on-farm.

The use of social network analysis to describe the effect of immune activation on group dynamics in pigs

The immune system can influence social motivation with potentially dire consequences for group-housed production animals, such as pigs. The aim of this study was to test the effect of a controlled immune activation in group-housed pigs, through an injection with lipopolysaccharide (LPS) and an intervention with ketoprofen on centrality parameters at the individual level. In addition, we wanted to test the effect of time relative to the injection on general network parameters in order to get a better understanding of changes in social network structures at the group level. 52 female pigs (11-12 weeks) were allocated to four treatments, comprising two injections: ketoprofen-LPS (KL), ketoprofen-saline (KS), saline-LPS (SL) and saline-saline (SS). Social behaviour with a focus on damaging behaviour was observed continuously in 10 × 15 min bouts between 0800 am and 1700 pm 1 day before (baseline) and two subsequent days after injection. Activity was scan-sampled every 5 min for 6 h after the last injection in the pen. Saliva samples were taken for cortisol analysis at baseline and at 4, 24, 48, 72 h after the injections. A controlled immune activation affected centrality parameters for ear manipulation networks at the individual level. Lipopolysaccharide-injected pigs had a lower in-degree centrality, thus, received less interactions, 2 days after the challenge. Treatment effects on tail manipulation and fighting networks were not observed at the individual level. For networks of manipulation of other body parts, in-degree centrality was positively correlated with cortisol response at 4 h and lying behaviour in the first 6 h after the challenge in LPS-injected pigs. Thus, the stronger the pigs reacted to the LPS, the more interactions they received in the subsequent days. The time in relation to injection affected general network parameters for ear manipulation and fighting networks at the group level. For ear manipulation networks, in-degree centralisation was higher on the days following injection, thus, certain individuals in the pen received more interactions than the rest of the group compared to baseline. For fighting networks, betweenness decreased on the first day after injection compared to baseline, indicating that network connectivity increased after the challenge. Networks of tail manipulation and manipulation of other body parts did not change on the days after injection at the group level. Social network analysis is a method that can potentially provide important insights into the effects of sickness on social behaviour in group-housed pigs.

Prenatal and Early Postnatal Behavioural Programming in Laying Hens, With Possible Implications for the Development of Injurious Pecking

Injurious pecking (IP) represents a serious concern for the welfare of laying hens (Gallus gallus domesticus). The risk of IP among hens with intact beaks in cage-free housing prompts a need for solutions based on an understanding of underlying mechanisms. In this review, we explore how behavioural programming via prenatal and early postnatal environmental conditions could influence the development of IP in laying hens. The possible roles of early life adversity and mismatch between early life programming and subsequent environmental conditions are considered. We review the role of maternal stress, egg conditions, incubation settings (temperature, light, sound, odour) and chick brooding conditions on behavioural programming that could be linked to IP. Brain and behavioural development can be programmed by prenatal and postnatal environmental conditions, which if suboptimal could lead to a tendency to develop IP later in life, as we illustrate with a Jenga tower that could fall over if not built solidly. If so, steps taken to optimise the environmental conditions of previous generations and incubation conditions, reduce stress around hatching, and guide the early learning of chicks will aid in prevention of IP in commercial laying hen flocks.

The Effect of LPS and Ketoprofen on Cytokines, Brain Monoamines, and Social Behavior in Group-Housed Pigs

Poor health is a risk factor for damaging behaviors, but the mechanisms behind this link are unknown. Injection of pigs with lipopolysaccharide (LPS) can be used to model aspects of poor health. Recent studies have shown that LPS-injected pigs perform more tail- and ear-directed behavior compared to saline-injected pigs and suggest that pro-inflammatory cytokines may play a role in these behaviors. The aims of this study were to test the effect of LPS on the social behavior of pigs and the neurotransmitters and modulators in their brains and to test the effect of a nonsteroidal anti-inflammatory drug on the effects of LPS. Fifty-two female pigs (11-12 weeks) were allocated to four treatments comprising two injections: saline-saline (SS), saline-LPS (SL), ketoprofen-saline (KS), and ketoprofen-LPS (KL). Activity was scan-sampled every 5 min for 6 h after the last injection in the pen. Social behavior was observed continuously in 10 × 15-min bouts between 8 a.m. and 5 p.m. 1 day before (baseline) and 1 and 2 days after the injection. Saliva was analyzed for cortisol and plasma for tryptophan and kynurenine. The frontal cortex, hippocampus, hypothalamus, and brain stem were sampled 72 h after the injection and analyzed for cytokines and monoamines. LPS activated the HPA axis and decreased the activity within 6 h after the injection. Ketoprofen lowered the effect of LPS on cortisol release and attenuated the behavioral signs of sickness in challenged pigs. SL pigs manipulated the ears of their pen mates significantly longer than SS pigs 2 days after the injection. LPS had no observed effect on IFN-γ, TNF-α, and IL-18. At 72 h after the injection, plasma tryptophan was depleted in SL pigs, and tryptophan and kynurenine concentrations in the frontal cortex and brain stem of SL pigs were significantly lower compared to those in SS pigs. Dopamine concentrations in the hypothalamus of SL pigs were significantly lower compared to those in SS pigs. Serotonin concentrations in the hypothalamus and noradrenaline concentrations in the hippocampus of SL pigs were significantly lower compared to those in KL pigs. In conclusion, LPS influenced the different neurotransmitters and modulators in the brain that are hypothesized to play an important role in the regulation of mood and behavior.

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.

Sick and grumpy: Changes in social behaviour after a controlled immune stimulation in group-housed gilts

Poor health is associated with an increased risk of tail biting outbreaks in pigs. We propose that this is because illness changes social dynamics either by changing the behaviour of the sick pig towards its penmates, the behaviour of the healthy penmates towards the sick pig, or both. We tested the effect of immune stimulation (lipopolysaccharide (LPS) injection: O111:B4; 1.5 μg kg^-1 IV) on social behaviour in gilts housed in triplets in a cross-over experiment. Each pen was subjected to the control treatment (all three pigs injected with saline) and then LPS treatment (one pig injected with LPS, two injected with saline), or vice versa. LPS injected pigs had a shift in social motivation and performed more tail- and ear- directed behaviour than saline pigs two days after injection. They seemed to fit the description of 'sick and grumpy'. This change was seen about 40 h after the signs of acute illness dissipated and was not accompanied by a similar increase in activity. We discuss possible mechanisms for this behavioural change in light of changes in neurotransmitter levels at three days after LPS injection described in a previous experiment.

The effect of lipopolysaccharide (LPS) on inflammatory markers in blood and brain and on behavior in individually-housed pigs

Most of us have experienced deterioration of mood while ill. In humans, immune activation is associated with lethargy and social withdrawal, irritability and aggression; changes in social motivation could, in theory, lead to less functional interactions. This might also be the case for animals housed in close confinement. Tail biting in pigs is an example of damaging social behavior, and sickness is thought to be a risk factor for tail biting outbreaks. One possible mechanism whereby sickness may influence behavior is through cytokines. To identify possible mediators between immune activation and behavioral change, we injected 16 gilts with lipopolysaccharide (LPS; O111:B4; 1.5 μg kg^-1 IV through a permanent catheter). In LPS-treated pigs, a significant increase in cortisol, TNF-α, IL-1 receptor antagonist, IL-6, and IL-8 was observed alongside decreased activity within the first 6 h after the injection. CRP was elevated at 12 and 24 h after injection, and food intake was reduced for the first 24 h after injection. Three days post-injection, LPS pigs had lower levels of noradrenaline in their hypothalamus, hippocampus and frontal cortex compared to saline-injected pigs. Pigs injected with LPS also had higher levels of the pro-inflammatory cytokine IFN-γ in their frontal cortex compared to saline-injected pigs. Thus, a low dose of LPS can induce changes in brain cytokine levels and neurotransmitter levels that persist after inflammatory and stress markers in the periphery have returned to baseline levels.

DNA methylation profiles in red blood cells of adult hens correlate with their rearing conditions

Stressful conditions are common in the environment where production animals are reared. Stress in animals is usually determined by the levels of stress-related hormones. A big challenge, however, is in determining the history of exposure of an organism to stress, because the release of stress hormones can show an acute (and recent) but not a sustained exposure to stress. Epigenetic tools provide an alternative option to evaluate past exposure to long-term stress. Chickens provide a unique model to study stress effects in the epigenome of red blood cells (RBCs), a cell type of easy access and nucleated in birds. The present study investigated whether two different rearing conditions in chickens can be identified by looking at DNA methylation patterns in their RBCs later in life. These conditions were rearing in open aviaries versus in cages, which are likely to differ regarding the amount of stress they generate. Our comparison revealed 115 genomic windows with significant changes in RBC DNA methylation between experimental groups, which were located around 53 genes and within 22 intronic regions. Our results set the ground for future detection of long-term stress in live production animals by measuring DNA methylation in a cell type of easy accessibility.

To be blamed or pitied? The effect of illness on social behavior, cytokine levels and feed intake in undocked boars

Tail biting is detrimental to animal welfare and has negative consequences for producer economy. Poor health is one of the risk factors for tail biting. The first aim of this study was therefore to test for links between health status and behavior related to tail biting at the individual level. The second aim of this study was to test whether variation in cytokines was related to variation in social behavior. These small molecules produced upon immune activation are known to influence behavior both in the direction of withdrawal and increased aggression. This could potentially increase non-functional social behavior and thereby the risk of a tail biting outbreak. To investigate this, we collected behavioral data, health data, feeding data and blood samples from undocked boars at a test station farm in Norway. We compared groups with three different diagnoses: osteochondrosis diagnosed by computer tomography scanning (OCSAN), osteochondrosis diagnosed by clinical examination (OCCLIN) and respiratory tract disease (RESP), with healthy controls (CTR). We tested whether the diagnoses were associated with feeding and growth, social behavior and cytokine levels. We then tested whether there were correlations between cytokine levels and social behavior. We also provide raw data on cytokine levels in the extended sample (N=305) as there are few publications on cytokine levels measured in pigs living under commercial conditions. OCCLIN pigs visited the feeder less, and fed longer compared to CTR pigs. Pigs diagnosed with RESP showed a large drop in growth the first week after filming, which corresponds to the week they were likely to have been diagnosed with illness, and a tendency to compensatory increase in the week after that. Social behavior differed between experimental groups with OCSCAN pigs receiving more social behavior (both aggressive and non-aggressive) compared to CTR, and RESP pigs tending to perform more ear- and tail-biting than controls. There were no differences in absolute levels of cytokines between categories. However IL1-ra and IL-12 showed correlations with several behaviors that have been shown by others to be associated with current or future tail biting activity. To our knowledge, this is the first published study indicating a role for illness in non-functional social behavior in pigs and the first showing a correlation between cytokine levels and social behavior.

Effects of litter provision during early rearing and environmental enrichment during the production phase on feather pecking and feather damage in laying hens

Feather pecking is a multi-factorial behavioral disorder and a serious welfare issue in the poultry industry. Several studies report early life experience with litter to be a major determinant in the development of feather pecking. The current study aimed to test the large-scale on-farm efficiency of a simple and cheap husbandry procedure applied during the rearing period with the ultimate goal of reducing the incidence of feather pecking and plumage damage during the production stage in laying hens. Five laying hen-rearing farmers from across Norway participated in the study. These farmers were asked to create divisions within their hen rearing houses and to separate their chicks into 2 groups: one reared with access to a paper substrate from the first d of age, the other a control group without access to paper substrate during rearing. All flocks were visited at the production farms at 30 wk of age and observed for pecking behavior and feather damage. Birds in the control group had higher odds of having more feather damage compared to the birds from the treatment group. In addition, flocks provided with environmental enrichment at the production farms had a reduced incidence of feather pecking, irrespective of the treatment. These results indicate that husbandry procedures during both rearing and production stages have the potential to alleviate feather pecking and increase laying hen welfare.

Exposure to Increased Environmental Complexity during Rearing Reduces Fearfulness and Increases Use of Three-Dimensional Space in Laying Hens (Gallus gallus domesticus)

The complexity of the rearing environment is important for behavioral development and fearfulness. The aim of this study was to test the hypothesis that laying hens reared in a complex aviary system with exposure to mild intermittent stressors would be less fearful, less sensitive to stress, and would use elevated areas of the pen more often as adults than hens reared in a barren cage environment. Laying hens (N = 160) were housed in the same rearing house; half of the birds (n = 80) in an aviary and the other half (n = 80) in cages. At 16 weeks of age, the birds were transported to the experimental facilities. Their behavior was recorded at 19 and 23 weeks of age and analyzed by analysis of variance on individual scores for a fearfulness-related principal component generated using principal component analysis. The results indicate that aviary-reared birds have lower levels of fearfulness compared with cage-reared birds both at 19 weeks and at 23 weeks of age. When comparing the response induced by initial exposure to a novel object at 19 and 23 weeks of age, more aviary-reared birds tended to fly up at 19 weeks compared to the cage-reared birds, indicating a tendency toward a more active behavioral response in the aviary-reared birds than in cage-reared birds. There was no difference between treatments in the flight response at 23 weeks. The groups did not differ in defecation frequency or the concentration of fecal corticosterone metabolites at either age. At 19 weeks, observation of the spatial distribution in the home pens indicated that more aviary-reared birds spent time on the low perch, the elevated platform, and the upper perch, compared to the cage-reared birds. However, at 23 weeks of age, these differences were no longer detected. The results of this study support the hypothesis that increased environmental complexity during rearing reduces fearfulness of adult laying hens.

Rearing Laying Hens in Aviaries Reduces Fearfulness following Transfer to Furnished Cages

Appropriate rearing is essential for ensuring the welfare and productivity of laying hens. Early experience has the potential to affect the development of fearfulness. This study tested whether rearing in aviaries, as opposed to cages, reduces the fearfulness of laying hens after transfer to furnished cages. Fear responses were recorded as avoidance of a novel object in the home cage. Lohmann Selected Leghorns were reared in an aviary system or conventional rearing cages and then transported to furnished cages at 16 weeks, before the onset of lay. Observations of a selection of birds were conducted at 19 (N = 50 independent cages) and 21 (N = 48 independent cages) weeks of age. At 19 and 21 weeks, cage-reared birds showed higher levels of fearfulness indicated by spending more time away from the novel object compared to aviary-reared birds. These results suggest that rearing in an enriched aviary environment reduces fearfulness up to the fifth week after transfer to a new housing system, compared to rearing in cages.

Does Early Environmental Complexity Influence Tyrosine Hydroxylase in the Chicken Hippocampus and "Prefrontal" Caudolateral Nidopallium?

In adult chickens, the housing system influences hippocampal morphology and neurochemistry. However, no work has been done investigating the effects of the early life environment on chicken brain development. In the present study, we reared 67 commercial laying hens (Gallus gallus domesticus) in two environments that differed in the degree of complexity (aviary or cage system). These two groups were further divided into two age groups. At 20 weeks of age, 18 aviary-reared birds and 15 cage-reared birds were humanely euthanized and their brains dissected. At 24 weeks of age, a further 16 brains from aviary-reared birds and 18 brains from cage-reared birds were collected. These brains were prepared for immunohistochemical detection of tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of dopamine, in the hippocampus and the caudolateral nidopallium (NCL). There were no differences between the treatment groups in TH staining intensity in the hippocampus or the NCL. In the medial hippocampus, the right hemisphere had higher TH staining intensity compared to the left hemisphere. The opposite was true for the NCL, with the left hemisphere being more strongly stained compared to the right hemisphere. The present study supports the notion that the hippocampus is functionally lateralized, and our findings add to the body of knowledge on adult neural plasticity of the avian brain.

Review of rearing-related factors affecting the welfare of laying hens

Laying hens may face a number of welfare problems including: acute and chronic pain caused by beak trimming; exaggerated fearfulness that may cause stress and suffocation; difficulties in locating resources, resulting potentially in emaciation and dehydration; frustration and boredom, caused by an environment that is barren; feather pecking; cannibalism; foot lesions; and bone fractures. In Europe, a greater proportion of laying hens are housed in non-cage systems compared to the rest of the world. The extent of the different welfare problems may therefore vary between countries as the type of housing system influences the risk of suffering. More generally, many of these welfare problems are influenced by the rearing environment of the pullets. This article therefore focuses on welfare problems in laying hens that can be traced back to rearing. Factors that have been studied in relation to their effects on bird welfare include beak trimming, housing type, furnishing, enrichment, feeding, stocking density, flock size, sound and light levels, concentration of gasses, age at transfer from rearing to production facilities, similarity between rearing and production facilities, competence of staff, and interactions between bird strain and environment. The present review aims to summarize rearing-related risk factors of poor welfare in adult laying hens housed according to European Union legislation. It aims to identify gaps in current knowledge, and suggests strategies for improving bird welfare by improving rearing conditions. Two main conclusions of this work are that attempts should be made to use appropriate genetic material and that beak trimming should be limited where possible. In addition to this, the rearing system should provide constant access to appropriate substrates, perches, and mashed feed, and should be as similar as possible to the housing system used for the adult birds. Finally, young birds (pullets) should be moved to the production facilities before 16 weeks of age. The measures outlined in this review may be useful for improving the welfare of pullets and adult laying hens.

Early Life in a Barren Environment Adversely Affects Spatial Cognition in Laying Hens (Gallus gallus domesticus)

Spatial cognition in vertebrates is adversely affected by a lack of environmental complexity during early life. However, to our knowledge, no previous studies have tested the effect of early exposure to varying degrees of environmental complexity on specific components of spatial cognition in chickens. There are two main rearing systems for laying hens in the EU: aviaries and cages. These two systems differ from one another in environmental complexity. The aim of the present study was to test the hypothesis that rearing in a barren cage environment relative to a complex aviary environment causes long-lasting deficits in the ability to perform spatial tasks. For this purpose, 24 white Dekalb laying hens, half of which had been reared in an aviary system and the other half in a conventional cage system, were tested in a holeboard task. Birds from both treatment groups learnt the task; however, the cage-reared hens required more time to locate rewards and had poorer levels of working memory. The latter finding supports the hypothesis that rearing in a barren environment causes long-term impairment of short-term memory in chickens.

Anticipatory and foraging behaviors in response to palatable food reward in chickens: effects of dopamine D2 receptor blockade and domestication

Behaviors associated with anticipation and search for palatable food may provide information about dopaminergic reward processes and positive motivational affect in animals. The overall aim was to investigate the involvement of dopamine signaling in the regulation of cue-induced anticipation and search for palatable food reward in chicken, and whether domestication has affected expression of reward-related behaviors. The specific aims were to describe effects of mealworms (palatable food for hens) and haloperidol (a dopamine D2 antagonist) on foraging behaviors and cue-induced anticipatory behaviors in Red Junglefowl (RJF; the wild ancestor of modern laying hens) and a white layer hybrid (LSL). RJF (n=26) and LSL (n=20) were initially trained on a conditioning schedule to anticipate mealworms (unconditioned stimulus; US) 25s after exposure to a red light (conditioned stimulus; CS). For the experiment, hens received haloperidol or saline injections 30 min before exposure to one CS+US combination. Behavior was registered 10 min before CS and 10 min after US (foraging behaviors), and during the CS-US interval (anticipatory behaviors). Higher frequencies of CS-induced anticipatory head movements, faster approach to rewards, and higher frequency of foraging behaviors were found in LSL compared to RJF. Haloperidol suppressed CS-induced head movements in both breeds, and the frequency of foraging behaviors after reward delivery. The results support a role of dopamine signaling in the regulation of reward processes in chickens, and suggest that domestication has changed the threshold for perceiving food incentives and/or for expressing reward-related behaviors that may be indicative of positive motivational affect in hens.

Ectoparasitic sea lice (Lepeophtheirus salmonis) affect behavior and brain serotonergic activity in Atlantic salmon (Salmo salar L.): Perspectives on animal welfare

Scientific research and public debate on the welfare of animals in human custody is increasing at present. Fish are in this context mentioned with particular attention to the high numbers of individuals reared in aquaculture. Research on fish has also contributed to the understanding of individual variation in the ability to cope with stress and disease. One mediator of such variation is the brain serotonergic (5-hydroxytryptamine, 5-HT) system, which conveys physiological and behavioral responses to stress and sub-optimal rearing conditions. Here we study links between the 5-HT response, melanin-based skin pigmentation, and behavior in laboratory-reared Atlantic salmon (Salmo salar) experimentally infested with ectoparasitic sea lice (Lepeophtheirus salmonis). Lice numbers were more variable in less pigmented fish, while the neurochemical response to ectoparastic lice-increased levels of the main 5-HT catabolite 5-HIAA in the brain stem-did not differ between pigmentation groups. A strong depression of growth and locomotor activity was seen in all infested fish but less pigmented fish grew better than fish with more skin melanization regardless of infestation status. The observed combination of neurochemical and behavioral effects clearly suggest that animal welfare concerns can be added to the list of negative effects of ectoparasitic sea lice.

Behavioural effects of the commonly used fish anaesthetic tricaine methanesulfonate (MS-222) on zebrafish (Danio rerio) and its relevance for the acetic acid pain test

The pros and cons of using anaesthesia when handling fish in connection with experiments are debated. A widely adopted practice is to wait thirty minutes after anaesthesia before behavioural observations are initiated, but information about immediate effects of a treatment is then lost. This is pertinent for responses to acute stressors, such as acid injection in the acetic acid pain test. However, omission of anaesthetics in order to obtain data on immediate responses will compromise the welfare of fish and contribute to experimental noise due to stress. We therefore tested the effect of tricaine methanesulfonate on the behaviour of zebrafish. We predicted that tricaine (MS 222) would decrease swimming velocity and that the control fish would show an increased level of anxiety- and stress-related behaviours compared to the tricaine group. Following acclimatization to the test tank, baseline behaviour was recorded before immersion in either tricaine (168 mg l⁻¹, treatment group, N = 8) or tank water (control group, N = 7). Latencies to lose equilibrium and to lose response to touch were registered. The fish was then returned to the test tank, and the latency to regain equilibrium was registered in anaesthetized fish. When equilibrium was regained, and at five, thirty and sixty minutes after the fish had been returned to the test tank, behaviour was recorded. The tricaine fish showed the following responses (mean ± sd): latency to lose equilibrium 22.6 s±3.9; latency to lose response to touch 101.9 s±26.8; latency to regain equilibrium 92.0 s±54.4. Contrary to our predictions, neither treatment caused a change in any of the behaviours registered. This indicates that tricaine has no effect on several commonly used behavioural parameters, and that it may be unnecessary to postpone behavioural observations to 30 min after anaesthesia.

Brucella pinnipedialis hooded seal (Cystophora cristata) strain in the mouse model with concurrent exposure to PCB 153

Brucellosis, a worldwide zoonosis, is linked to reproductive problems in primary hosts. A high proportion of Brucella-positive hooded seals (Cystophora cristata) have been detected in the declined Northeast Atlantic stock. High concentrations of polychlorinated biphenyls (PCBs) have also been discovered in top predators in the Arctic, including the hooded seal, PCB 153 being most abundant. The aim of this study was to assess the pathogenicity of Brucella pinnipedialis hooded seal strain in the mouse model and to evaluate the outcome of Brucella spp. infection after exposure of mice to PCB 153. BALB/c mice were infected with B. pinnipedialis hooded seal strain or Brucella suis 1330, and half from each group was exposed to PCB 153 through the diet. B. pinnipedialis showed a reduced pathogenicity in the mouse model as compared to B. suis 1330. Exposure to PCB 153 affected neither the immunological parameters, nor the outcome of the infection. Altogether this indicates that it is unlikely that B. pinnipedialis contribute to the decline of hooded seals in the Northeast Atlantic.

Early adverse experience alters dendritic spine density and gene expression in prefrontal cortex and hippocampus in lambs

In the laboratory, prenatal stress produces alterations in the structure and function of corticolimbic neurons. Here we report changes in gene expression and corticolimbic dendritic spine morphology in the offspring of pregnant ewes subjected to aversive interactions with human handlers during the last five weeks of pregnancy (AVS) compared to control dams that received gentle handling (GEN). AVS lambs had higher spine density on pyramidal neurons in area CA1 of the hippocampus and in medial prefrontal cortex compared to GEN lambs, as well as a lower ratio of mushroom spines to stubby and thin spines in area CA1. Expression of genes involved in brain development and spine morphogenesis was decreased in hippocampus and prefrontal cortex in AVS compared to GEN lambs. This study is the first demonstration that an ecologically relevant aversive experience in a field setting alters neuronal structure similarly to previous reports from laboratory settings and that even for animals domesticated over 12,000 years ago, an apparently mild stressor, resulting from human-animal interactions, can have similarly profound impacts on corticolimbic morphology.

Factors affecting mechanical (nociceptive) thresholds in piglets

Objective

To evaluate the stability and repeatability of measures of mechanical (nociceptive) thresholds in piglets and to examine potentially confounding factors when using a hand held algometer.

Study design

Descriptive, prospective cohort.

Animals

Forty-four piglets from four litters, weighing 4.6 ± 1.0 kg (mean ± SD) at 2 weeks of age.

Methods

Mechanical thresholds were measured twice on each of 2 days during the first and second week of life. Data were analyzed using a repeated measures design to test the effects of behavior prior to testing, sex, week, day within week, and repetition within day. The effect of body weight and the interaction between piglet weight and behaviour were also tested. Piglet was entered into the model as a random effect as an additional test of repeatability. The effect of repeated testing was used to test the stability of measures. Pearson correlations between repeated measures were used to test the repeatability of measures. Variance component analysis was used to describe the variability in the data.

Results

Variance component analysis indicated that piglet explained only 17% of the variance in the data. All variables in the model (behaviour prior to testing, sex, week, day within week, repetition within day, body weight, the interaction between body weight and behaviour, piglet identity) except sex had a significant effect (p < 0.04 for all). Correlations between repeated measures increased from the first to the second week.

Conclusions and Clinical relevance

Repeatability was acceptable only during the second week of testing and measures changed with repeated testing and increased with increasing piglet weight, indicating that time (age) and animal body weight should be taken into account when measuring mechanical (nociceptive) thresholds in piglets. Mechanical (nociceptive) thresholds can be used both for testing the efficacy of anaesthetics and analgesics, and for assessing hyperalgesia in chronic pain states in research and clinical settings.

Identification of low and high frequency ranges for heart rate variability and blood pressure variability analyses using pharmacological autonomic blockade with atropine and propranolol in swine

Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for assessing farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency domain analyses may provide a sensitive and reliable measure of affective states and stress-mediated changes in sympathetic and parasympathetic tones. The aim of this research was to define low (LF) and high frequency (HF) power spectral ranges using pharmacological autonomic blockade, and to examine HRV and BPV parameter changes in response to atropine and propranolol in swine. Ten, 13-week old, barrows (n=6) and gilts (n=4) underwent surgery to place an intra-cardiac electrode and a blood pressure catheter attached to a biotelemetric transmitter; pigs had a 3-week recovery period prior to data collection. Each pig was subjected to administration of 4 intravenous (i.v.) drug treatments: a control treatment, 3 mL of saline, and 3 blockade treatments; 0.1 mg/kg of atropine, 1.0 mg/kg of propranolol, and .1 mg/kg of atropine together with 1.0 mg/kg of propranolol. All treatments were delivered by injection in the jugular vein with a minimum of 48 h between individual treatments. Behavior, ECG and blood pressure data were recorded continuously for a total of 1h, from 30 min pre-injection to 30 min post-injection. For data analyses, two 512-beat intervals were selected for each treatment while the pig was lying and inactive. The first interval was selected from the pre-injection period (baseline), and the second was selected between 10 and 30 min post-injection. Time and frequency domain (power spectral density) analyses were performed on each data interval. Subsequent, LF and HF bands from the power spectral densities were defined based on general linear and regression analyses. The HRV and BPV were computed with a covariate (baseline) factorial analysis of treatment by sex interaction, and day of injection, with mixed models and Tukey's post-hoc tests. The best-fit range for LF was 0.0-0.09 Hz, and HF was 0.09-2.0 Hz (r²: 0.41 and 0.43, respectively). Propranolol and saline injections led to a greater overall total power and overall higher inter-beat interval, HF and LF power. Atropine led to a dominant sympathovagal balance of the cardiac activity in pigs. In addition, atropine led to an increase in LF power of both systolic and diastolic blood pressures in gilts suggesting vagal tone mediation of BPV. The understanding of autonomic regulation of HRV and BPV in domestic swine facilitates our ability to detect and quantify stress responses, and broadens its application in assessing farm animal welfare.

Effects of haloperidol, a dopamine D2-like receptor antagonist, on reward-related behaviors in laying hens

In order to investigate the involvement of dopaminergic transmission in the regulation of reward-related behaviors in laying hens, the effects of systemic injections of dopamine D2-like receptor antagonist haloperidol (0.3, 0.5, 1.0 and 2.0 mg/kg s.c.) 30 min prior to a conditioned cue signaling a reward were tested and compared to the effects of a saline injection. Head movements and latency to initiate display of anticipatory behavior were significantly affected by 0.3 and 0.5 mg/kg haloperidol, respectively. More hens were found lying down resting prior to the cue at 0.5 mg/kg and higher doses, and increased latency to peck at reward and shorter duration of anticipatory behavior was significant at 2.0 mg/kg. The findings are consistent with the involvement of dopamine in control of reward-related behaviors in laying hens. It is suggested that the lowest dose of haloperidol (0.3 mg/kg) affects reward-related behaviors, whereas the effects of higher doses of haloperidol could be confounded by sedative effects. A high inter- and intra observer agreement in the assessment of head movements together with their dopamine dependency further suggest that this behavior in classical conditioning paradigm represents an indicator of the state of the reward system in laying hens that can be assessed with good reliability.

Transmission of stress-induced learning impairment and associated brain gene expression from parents to offspring in chickens

Background

Stress influences many aspects of animal behaviour and is a major factor driving populations to adapt to changing living conditions, such as during domestication. Stress can affect offspring through non-genetic mechanisms, but recent research indicates that inherited epigenetic modifications of the genome could possibly also be involved.

Methodology/Principal Findings

Red junglefowl (RJF, ancestors of modern chickens) and domesticated White Leghorn (WL) chickens were raised in a stressful environment (unpredictable light-dark rhythm) and control animals in similar pens, but on a 12/12 h light-dark rhythm. WL in both treatments had poorer spatial learning ability than RJF, and in both populations, stress caused a reduced ability to solve a spatial learning task. Offspring of stressed WL, but not RJF, raised without parental contact, had a reduced spatial learning ability compared to offspring of non-stressed animals in a similar test as that used for their parents. Offspring of stressed WL were also more competitive and grew faster than offspring of non-stressed parents. Using a whole-genome cDNA microarray, we found that in WL, the same changes in hypothalamic gene expression profile caused by stress in the parents were also found in the offspring. In offspring of stressed WL, at least 31 genes were up- or down-regulated in the hypothalamus and pituitary compared to offspring of non-stressed parents.

Conclusions/Significance

Our results suggest that, in WL the gene expression response to stress, as well as some behavioural stress responses, were transmitted across generations. The ability to transmit epigenetic information and behaviour modifications between generations may therefore have been favoured by domestication. The mechanisms involved remain to be investigated; epigenetic modifications could either have been inherited or acquired de novo in the specific egg environment. In both cases, this would offer a novel explanation to rapid evolutionary adaptation of a population.