More than numbers matter: The effect of social factors on behaviour and welfare of laboratory rodents and non-human primates

Contactless vital signs monitoring in macaques using a mm-wave FMCW radar

Heart rate (HR) and respiration rate (RR) play an important role in the study of complex behaviors and their physiological correlations in non-human primates (NHPs). However, collecting HR and RR information is often challenging, involving either invasive implants or tedious behavioral training, and there are currently few established simple and non-invasive techniques for HR and RR measurement in NHPs owing to their stress response or indocility. In this study, we employed a frequency-modulated continuous wave (FMCW) radar to design a novel contactless HR and RR monitoring system. The designed system can estimate HR and RR in real time by placing the FMCW radar on the cage and facing the chest of both awake and anesthetized macaques, the NHP investigated in this study. Experimental results show that the proposed method outperforms existing methods, with averaged absolute errors between the reference monitor and radar estimates of 0.77 beats per minute (bpm) and 1.29 respirations per minute (rpm) for HR and RR, respectively. In summary, we believe that the proposed non-invasive and contactless estimation method could be generalized as a HR and RR monitoring tool for NHPs. Furthermore, after modifying the radar signal-processing algorithms, it also shows promise for applications in other experimental animals for animal welfare, behavioral, neurological, and ethological research.

Months-long tracking of neuronal ensembles spanning multiple brain areas with Ultra-Flexible Tentacle Electrodes

We introduce Ultra-Flexible Tentacle Electrodes (UFTEs), packing many independent fibers with the smallest possible footprint without limitation in recording depth using a combination of mechanical and chemical tethering for insertion. We demonstrate a scheme to implant UFTEs simultaneously into many brain areas at arbitrary locations without angle-of-insertion limitations, and a 512-channel wireless logger. Immunostaining reveals no detectable chronic tissue damage even after several months. Mean spike signal-to-noise ratios are 1.5-3x compared to the state-of-the-art, while the highest signal-to-noise ratios reach 89, and average cortical unit yields are ~1.75/channel. UFTEs can track the same neurons across sessions for at least 10 months (longest duration tested). We tracked inter- and intra-areal neuronal ensembles (neurons repeatedly co-activated within 25 ms) simultaneously from hippocampus, retrosplenial cortex, and medial prefrontal cortex in freely moving rodents. Average ensemble lifetimes were shorter than the durations over which we can track individual neurons. We identify two distinct classes of ensembles. Those tuned to sharp-wave ripples display the shortest lifetimes, and the ensemble members are mostly hippocampal. Yet, inter-areal ensembles with members from both hippocampus and cortex have weak tuning to sharp wave ripples, and some have unusual months-long lifetimes. Such inter-areal ensembles occasionally remain inactive for weeks before re-emerging.

Neural cell-types and circuits linking thermoregulation and social behavior

Understanding how social and affective behavioral states are controlled by neural circuits is a fundamental challenge in neurobiology. Despite increasing understanding of central circuits governing prosocial and agonistic interactions, how bodily autonomic processes regulate these behaviors is less resolved. Thermoregulation is vital for maintaining homeostasis, but also associated with cognitive, physical, affective, and behavioral states. Here, we posit that adjusting body temperature may be integral to the appropriate expression of social behavior and argue that understanding neural links between behavior and thermoregulation is timely. First, changes in behavioral states-including social interaction-often accompany changes in body temperature. Second, recent work has uncovered neural populations controlling both thermoregulatory and social behavioral pathways. We identify additional neural populations that, in separate studies, control social behavior and thermoregulation, and highlight their relevance to human and animal studies. Third, dysregulation of body temperature is linked to human neuropsychiatric disorders. Although body temperature is a "hidden state" in many neurobiological studies, it likely plays an underappreciated role in regulating social and affective states.

Effects of social housing conditions on ethanol-induced behavioral sensitization in Swiss mice

RATIONALE

In previous animal model studies, it was shown that drug sensitization is dependent upon physical environmental conditions. However, the effects of social housing conditions on drug sensitization is much less known.

OBJECTIVE

The aim of the present study was to investigate the effects of social conditions, through the size of housing groups, on ethanol stimulant effects and ethanol-induced behavioral sensitization in mice.

MATERIALS AND METHODS

Male and female Swiss mice were housed in groups of different sizes (isolated mice, two mice per cage, four mice per cage and eight mice per cage) during a six-week period. A standard paradigm of ethanol-induced locomotor sensitization was then started with one daily injection of 2.5 g/kg ethanol for 8 consecutive days.

RESULTS

The results show that social housing conditions affect the acute stimulant effects of ethanol. The highest stimulant effects were observed in socially isolated mice and then gradually decreased as the size of the group increased. Although the rate of ethanol sensitization did not differ between groups, the ultimate sensitized levels of ethanol-induced stimulant effects were significantly reduced in mice housed in groups of eight.

CONCLUSIONS

These results are consistent with the idea that higher levels of acute and sensitized ethanol stimulant effects are observed in mice housed in stressful housing conditions, such as social isolation.

Behavioral responses of vervet monkey Chlorocebus pygerythrus infants in a novel fostering program

Vervet monkeys (Chlorocebus pygerythrus) are considered pests by farmers and homeowners. Consequent attempts to exterminate problem adult vervet monkeys often result in orphaned young offspring, which are sometimes taken to wildlife rehabilitation centers. We assessed the success of a novel fostering program at the Vervet Monkey Foundation, South Africa. Nine orphaned vervet monkeys were fostered to adult conspecific females of existing troops at the Foundation. The fostering protocol focused on reducing the time orphans spent in human rearing and involved a stepwise process of integration. We recorded the behaviors of orphans, including their interactions with their foster mother, to assess the process of fostering. Fostering success was high (89%). Orphans maintained close association with the foster mother and had little or no socio-negative and abnormal behavior. Comparison with literature showed a similar high fostering success in another vervet monkey study, regardless of the period and level of human-caregiving, and it is apparent that the duration of human care is less important than the protocol used for fostering. Nonetheless, our study has conservation relevance for vervet monkey rehabilitation.

A systematic review of the development and application of home cage monitoring in laboratory mice and rats

BACKGROUND

Traditionally, in biomedical animal research, laboratory rodents are individually examined in test apparatuses outside of their home cages at selected time points. However, the outcome of such tests can be influenced by various factors and valuable information may be missed when the animals are only monitored for short periods. These issues can be overcome by longitudinally monitoring mice and rats in their home cages. To shed light on the development of home cage monitoring (HCM) and the current state-of-the-art, a systematic review was carried out on 521 publications retrieved through PubMed and Web of Science.

RESULTS

Both the absolute (~ × 26) and relative (~ × 7) number of HCM-related publications increased from 1974 to 2020. There was a clear bias towards males and individually housed animals, but during the past decade (2011-2020), an increasing number of studies used both sexes and group housing. In most studies, animals were kept for short (up to 4 weeks) time periods in the HCM systems; intermediate time periods (4-12 weeks) increased in frequency in the years between 2011 and 2020. Before the 2000s, HCM techniques were predominantly applied for less than 12 h, while 24-h measurements have been more frequent since the 2000s. The systematic review demonstrated that manual monitoring is decreasing in relation to automatic techniques but still relevant. Until (and including) the 1990s, most techniques were applied manually but have been progressively replaced by automation since the 2000s. Independent of the year of publication, the main behavioral parameters measured were locomotor activity, feeding, and social behaviors; the main physiological parameters were heart rate and electrocardiography. External appearance-related parameters were rarely examined in the home cages. Due to technological progress and application of artificial intelligence, more refined and detailed behavioral parameters have been investigated in the home cage more recently.

CONCLUSIONS

Over the period covered in this study, techniques for HCM of mice and rats have improved considerably. This development is ongoing and further progress as well as validation of HCM systems will extend the applications to allow for continuous, longitudinal, non-invasive monitoring of an increasing range of parameters in group-housed small rodents in their home cages.

Towards substitution of invasive telemetry: An integrated home cage concept for unobtrusive monitoring of objective physiological parameters in rodents

This study presents a novel concept for a smart home cage design, tools, and software used to monitor the physiological parameters of mice and rats in animal-based experiments. The proposed system focuses on monitoring key clinical parameters, including heart rate, respiratory rate, and body temperature, and can also assess activity and circadian rhythm. As the basis of the smart home cage system, an in-depth analysis of the requirements was performed, including camera positioning, imaging system types, resolution, frame rates, external illumination, video acquisition, data storage, and synchronization. Two different camera perspectives were considered, and specific camera models, including two near-infrared and two thermal cameras, were selected to meet the requirements. The developed specifications, hardware models, and software are freely available via GitHub. During the first testing phase, the system demonstrated the potential of extracting vital parameters such as respiratory and heart rate. This technology has the potential to reduce the need for implantable sensors while providing reliable and accurate physiological data, leading to refinement and improvement in laboratory animal care.

Promoting Good Nonhuman Primate Welfare outside Regular Working Hours

Promoting good primate welfare outside of daylight hours is an important task. The responsibility to provide a complex environment and environmental enrichment is an essential element of primate wellbeing programs that should be approached from a 24-h perspective and planned according to the species and individual needs, including giving animals the ability to interact with and control their environment during hours when animal care staff are not present. One must be aware, however, that their needs may differ at night-time from their care needs during the day when staff are present. Assessing welfare and providing enrichment during times when staff are not on hand can be achieved through the use of a variety of technologies, such as night-view cameras, animal-centred technologies, and data loggers. This paper will address the relevant topics concerning the care and welfare of primates during off-hours, and the use of related technologies to facilitate and assess wellbeing at these times.

The impact of social and environmental factors on cancer biology in Black Americans

Low socioeconomic status (SES) is associated with early onset of chronic diseases and reduced life expectancy. The involvement of neighborhood-level factors in defining cancer risk and outcomes for marginalized communities has been an active area of research for decades. Yet, the biological processes that underlie the impact of SES on chronic health conditions, such as cancer, remain poorly understood. To date, limited studies have shown that chronic life stress is more prevalent in low SES communities and can affect important molecular processes implicated in tumor biology such as DNA methylation, inflammation, and immune response. Further efforts to elucidate how neighborhood-level factors function physiologically to worsen cancer outcomes for disadvantaged communities are underway. This review provides an overview of the current literature on how socioenvironmental factors within neighborhoods contribute to more aggressive tumor biology, specifically in Black U.S. women and men, including the impact of environmental pollutants, neighborhood deprivation, social isolation, structural racism, and discrimination. We also summarize commonly used methods to measure deprivation, discrimination, and structural racism at the neighborhood-level in cancer health disparities research. Finally, we offer recommendations to adopt a multi-faceted intersectional approach to reduce cancer health disparities and develop effective interventions to promote health equity.

Aggression in Group-Housed Male Mice: A Systematic Review

Aggression among group-housed male mice is a major animal welfare concern often observed at animal facilities. Studies designed to understand the causes of male mice aggression have used different methodological approaches and have been heterogeneous, using different strains, environmental enrichments, housing conditions, group formations and durations. By conducting a systematic literature review based on 198 observed conclusions from 90 articles, we showed that the methodological approach used to study aggression was relevant for the outcome and suggested that home cage observations were better when studying home cage aggression than tests provoking aggression outside the home cage. The study further revealed that aggression is a complex problem; one solution will not be appropriate for all animal facilities and all research projects. Recommendations were provided on promising tools to minimize aggression, based on the results, which included what type of environmental enrichments could be appropriate and which strains of male mice were less likely to be aggressive.

The effects of visitors and social isolation from a peer on the behavior of a mixed-species pair of captive gibbons

Human visitors affect the behavior of captive animals, which is the so-called visitor effect. The number and behavior of visitors may influence stress-related behaviors in captive animals, such as self-scratching, yawning, and visitor-directed vigilance. A social group setting can be applied to alleviate such negative visitor effects and facilitate social behavior and interactions between individuals. In this study, we examined how the number and behavior of visitors are related to stress-related behaviors of a captive mixed-species gibbon pair comprising a yellow-cheek gibbon (Nomascus gabriellae) and a white-handed gibbon (Hylobates lar). The two gibbons were separated during the study period, and we examined whether the social isolation stimulated the visitor effect. The frequency of stress-related behaviors of the gibbons increased and the social playing between them decreased proportionally to visitor number. In the indoor enclosure, the gibbons increased their visitor-directed vigilance when visitors shouted or struck the glass partition. Our findings indicate that the number and behavior of visitors negatively affect captive gibbons and that a mixed-species social setting can help gibbons reduce visitor-induced stress. Future studies with larger sample sizes will improve the understanding of the visitor effect and the social setting in the captivity.

A dynamic concept of animal welfare: The role of appetitive and adverse internal and external factors and the animal’s ability to adapt to them

Animal welfare is a multifaceted issue that can be approached from different viewpoints, depending on human interests, ethical assumptions, and culture. To properly assess, safeguard and promote animal welfare, concepts are needed to serve as guidelines in any context the animal is kept in. Several different welfare concepts have been developed during the last half decade. The Five Freedoms concept has provided the basis for developing animal welfare assessment to date, and the Five Domains concept has guided those responsible for safeguarding animal welfare, while the Quality of Life concept focuses on how the individual perceives its own welfare state. This study proposes a modified and extended version of an earlier animal welfare concept - the Dynamic Animal Welfare Concept (DAWCon). Based on the adaptability of the animal, and taking the importance of positive emotional states and the dynamic nature of animal welfare into account, an individual animal is likely in a positive welfare state when it is mentally and physically capable and possesses the ability and opportunity to react adequately to sporadic or lasting appetitive and adverse internal and external stimuli, events, and conditions. Adequate reactions are elements of an animal’s normal behavior. They allow the animal to cope with and adapt to the demands of the (prevailing) environmental circumstances, enabling it to reach a state that it perceives as positive, i.e., that evokes positive emotions. This paper describes the role of internal as well as external factors in influencing welfare, each of which exerts their effects in a sporadic or lasting manner. Behavior is highlighted as a crucial read-out parameter. As most animals under human care are selected for certain traits that may affect their behavioral repertoire it is crucial to have thorough ethograms, i.e., a catalogue of specific behaviors of the species/strain/breed under study. DAWCon highlights aspects that need to be addressed when assessing welfare and may stimulate future research questions.

Male and Female C57BL/6 Mice Respond Differently to Awake Magnetic Resonance Imaging Habituation

Traditionally, preclinical magnetic resonance imaging (MRI) has been performed in anesthetized animals. However, anesthesia has been shown to perturb normal brain function and physiology. Such effects limit our ability to detect subtle physiological alterations in disease models and treatment studies, thus hampering discovery and compromising generality of findings. Therefore, methods for awake animal MRI are needed to study the rodent brain in its natural physiological state, free of anesthetics. Current setups for awake animal MRI rely on restraining systems to avoid animal movement during scanning. To reduce restraint stress, animals are habituated to the scanner environment prior to MRI data collection. To date, however, most awake MRI studies employ male rodents only. This is a fundamental limitation as results obtained may be pertinent only to half of the population. We characterized training and habituation responses of male and female mice to provide improved, sex-dependent training procedures for awake mouse MRI. We recorded heart rate, monitored behavioral responses (body weight and fecal boli weight) and fecal corticosterone levels (FCM) as indicators of wellbeing and stress during a 14-day progressive habituation protocol. In addition, we also assessed discomfort levels and anxiety using the mouse grimace scale (MGS) and light/dark test (LDT), respectively. All scores were compared between both groups. We found that heart rate was significantly decreased after 10 and 11 days of training for both males and females, respectively. However, the specific time course for this decrease was significantly different between males and females, and females exhibited higher anxiety levels during habituation and 14 days after habituation than males. Lastly, we also found that mean FCM levels for both groups were decreased after 11 days of MRI habituation. The present work shows that mice can be successfully trained for extended MRI sessions which is necessary for many (particularly non-fMRI) studies. Importantly, we find that males and females differ in their response to awake MRI habituation, which should be considered in future awake MRI studies that aim to include male and female mice.

Effects of separated pair housing of female C57BL/6JRj mice on well-being

In laboratory animal facilities, it is a common code of practice to house female mice in groups. However, some experimental conditions require to house them individually, even though social isolation may impair their well-being. Therefore, we introduced a separated pair housing system and investigated whether it can refine single housing of adult female C57BL/6JRj mice. Individually ventilated cages (IVC) were divided by perforated transparent walls to separate two mice within a cage. The cage divider allowed visual, acoustic, and olfactory contact between the mice but prevented interindividual body-contact or food sharing. Short- and long-term effects of the separated pair housing system on the well-being of the mice were compared with single and group housing using a range of behavioral and physiological parameters: Nest building behavior was assessed based on the complexity of nests, the burrowing performance was measured by the amount of food pellets removed from a bottle, and trait anxiety-related behavior was tested in the free exploratory paradigm. For the evaluation of the ease of handling, interaction with the experimenter's hand was monitored. Social interaction with unknown conspecifics and locomotor activity were investigated in a test arena. Moreover, body weight and stress hormone (metabolites) were measured in feces and hair. After the mice spent a day under the respective housing conditions, concentrations of fecal corticosterone metabolites were higher in separated pair-housed mice, and they built nests of a higher complexity when compared to single-housed mice. The latter effect was still observable eight weeks later. In week 8, separated pair-housed mice showed less locomotor activity in the social interaction arena compared to mice from the other housing systems, i.e., single and group housing. Regardless of the time of testing, pair housing improved the burrowing performance. Separated pair-housed mice were more difficult to catch than group-housed mice. Hair corticosterone, progesterone, and dehydroepiandrosterone concentrations changed with increasing age independently of the housing system. There were no effects of the housing systems on trait anxiety-related behavior in the free exploratory paradigm, voluntary interaction with the experimenter’s hand, and body weight. Overall, the transfer to the separated pair housing system caused short-term stress responses in female C57BL/6JRj mice. Long-term effects of separated pair housing were ambiguous. On one hand, separated pair housing increased nesting and burrowing behavior and may therefore be beneficial compared to single housing. But on the other hand, locomotor activity decreased. The study underlined that the effects of the housing conditions on physiological and behavioral parameters should be considered when analyzing and reporting animal experiments.

Influence of Pair-housing on Sleep Parameters Evaluated with Actigraphy in Female Rhesus Monkeys

Rhesus monkeys are naturally social animals, and behavioral management strategies have focused on promoting pairhousing in laboratory settings as an alternative to individual or group housing. In humans, co-sleeping can have a major impact on bed partners' sleep, raising the possibility that pair-housing also may influence sleep parameters in monkeys. In the present study, we investigated if pair-housing would impact home-cage partner's sleep in female rhesus monkeys, and if nighttime separation using socialization panels would alter this pattern. Sleep parameters of 10 experimentally naïve adult female rhesus monkeys (5 pairs) were evaluated for 7 consecutive days using actigraphy monitors attached to primate collars. Paired animals then were separated by socialization panels during the night, and sleep-associated measures were evaluated for 7 consecutive days. The data showed that sleep efficiency was significantly lower when monkeys were pairhoused as compared with when they were separated. On the nights when subjects were pair-housed, a positive correlation was detected for sleep measures (both sleep latency and efficiency) of both members of a pair (R2's = 0.16-0.5), suggesting that pair-housing influences sleep quality. On nights when subjects were separated, no correlations were observed for sleep measures between members of the pairs (R2's = 0.004-0.01), suggesting that when separated, the home-cage partner's sleep no longer influenced the partner's sleep. Our results indicate that pair-housing has a strong impact on the home-cage partner's sleep, and that this pattern can be prevented by nighttime separation using socialization panels. Studies evaluating sleep in pair-housed monkeys should consider the effects that the partner's sleep may have on the subject's sleep. Sleep is a biologic phenomenon and experimental outcome that affects physical and behavioral health and altered sleep due to pair-housing may affect a range of research outcomes.

Early-life mice housed in standard stocking density reduce the spontaneous physical activity and increase visceral fat deposition before reaching adulthood

Laboratory rodents spend the entire day housed in standard cages that provide a restricted area for movements and might, therefore, limit physical activity. However, it has not been tested in immature rodents of ages ranging from weaning to adulthood (adolescence period) whether the restricted area per animal does actually reduce physical activity and impact the body composition. We analyzed the spontaneous physical activity and feeding behavior during the adolescence of mice kept in two different housing conditions (standard stocking density (SSD) versus low stocking density (LSD)). We aimed to compare the body composition between SSD and LSD groups before they reached adulthood. Differential housing began at four weeks of age and was maintained for four weeks until euthanasia at eight weeks of age. The SSD group had a floor space of 88 cm² available per animal, while LSD mice were housed with a floor space of 320 cm² per animal, increasing the individual radius for movement more than three-fold compared with standard requirements. Mice kept in SSD exhibit lower spontaneous physical activity than mice kept in LSD. Early-life exposure to reduced physical activity in mice housed in SSD resulted in greater visceral fat accumulation before adulthood. An environment enabling/stimulating physical activity should be established for rodents as early as possible. This study will be helpful in showing that mice kept in SSD are early exposed to a reduced physical activity already in the adolescence period. Our findings could raise reflections about the translatability of rodents kept in SSD to healthy active humans.

An apparatus for automatically training and collecting individualized behavioral data with socially housed rodents

BACKGROUND

Conventional methods for individually housing, training, and testing rodents in behavioral assays can impose constraints that may limit some kinds of experimental external validity, preempt environmental enrichment, impose heavy experimenter time burdens that limit high-throughput data collection, and negatively impact animal welfare.

NEW METHOD

To address these issues, we created a simple apparatus for automatically collecting individually identified data with rodents in social and/or enriched housing.

RESULTS

We validated this "One Rat Turnstyle" (ORT) apparatus by utilizing it to automatically teach socially housed rats to individually press a lever without experimenter intervention or shaping. Results confirmed the feasibility and reliability of the apparatus, with almost all rats learning to move through the ORT and press a lever for sugar water by the end of the experiment. Rats had lower fecal cortisol when engaging with the ORT than with experimenter conducted daily behavioral training sessions.

COMPARISON WITH EXISTING METHOD(S)

The ORT is less electronically complex and more scalable compared to previous similar ideas. It requires only a 3d printer and the purchase of few parts. It is also designed to allow animals to quickly learn how to utilize it by minimizing passthrough time.

CONCLUSIONS

Rats passed through the ORT both quickly and efficiently, self-administering reasonably timed behavioral sessions throughout the day. This success demonstrates that the ORT can enable the collection of both traditional and innovative, self-paced data in the context of socially housed animals, and may contribute to expanded, ecologically valid modelling.

Exploring Refinement Strategies for Single Housing of Male C57BL/6JRj Mice: Effect of Cage Divider on Stress-Related Behavior and Hypothalamic-Pituitary-Adrenal-Axis Activity

Introduction: Single housing of laboratory mice is a common practice to meet experimental needs, or to avoid intermale aggression. However, single housing is considered to negatively affect animal welfare and may compromise the scientific validity of experiments. The aim of this study was to investigate whether the use of a cage with a cage divider, which avoids physical contact between mice while maintaining sensory contact, may be a potential refinement strategy for experiments in which group housing of mice is not possible.

Methods: Eight-week-old male C57BL/6JRj mice were single housed, pair housed or pair housed with a cage divider for four (experiment 1) or ten (experiment 2) weeks, after which we performed an open field test, Y-maze spontaneous alternation test, elevated plus maze test, an auditory fear conditioning task, and assessed responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis.

Results: Housing conditions did not affect body weight, exploratory activity, anxiety, working memory, fear memory processing or markers for HPA-axis functioning in either experiment 1 or experiment 2. There was an increased distance traveled in mice housed with a cage divider compared to pair housed mice after 4 weeks, and after 10 weeks mice housed with a cage divider made significantly more arm entries in the Y-maze spontaneous alternation test.

Conclusion: Taken together, our study did not provide evidence for robust differences in exploratory activity, anxiety, working memory and fear memory processing in male C57BL/6JRj mice that were single housed, pair housed or pair housed with a cage divider.

Welfare Improvement by Enrichment Programs in Common Marmoset Females Under Social Isolation

Animal welfare is critical to buffer stress in captive animals and to ensure the reliability of data from studies. The most usual environmental enrichment technique (EE) for social non-human primates is the social enrichment. However, some experimental protocols require keeping individuals isolated, thus demanding other types of EE. We tested in six adult Callithrix jacchus females, single housed for experimental purpose, the stress buffering efficacy of a structural enrichment protocol (SEP) and SEP in combination with a foraging enrichment (FSEP) using  fecal cortisol and behaviors to infer stress levels. Both types of EE improved welfare in different ways, while cortisol levels decreased with both EE as compared to the baseline, autogrooming, and piloerection increased after FSEP probably due to the new foods. Therefore, these findings support alternative practices of EE when social animals are living in isolation and reinforce the positive role of structural and food enrichment for decreasing stress markers. It also encourages studies on welfare with females, since its use as an animal model has increased .

Temperament Predicts the Quality of Social Interactions in Captive Female Rhesus Macaques (Macaca mulatta)

Previous reports suggest that female macaques with greater similarity in emotionality and nervous temperament, as evaluated in a well-established BioBehavioral Assessment (BBA) at the California National Primate Research Center, were more likely to form successful pairs. We tested whether the same measures can also predict the quality of social interactions among 20 female rhesus macaque pairs. We correlated the pairs' emotionality and nervous temperament scores obtained in infancy and the levels of behaviors recorded systematically during the pairing process years later. Supporting previous findings, partners with similar emotionality scores were more affiliative, and pairs with similar nervous temperament expressed less dominance/submissive behavior. Exploratorily, we found that pairs that were better at processing social information (part of BBA) were also more anxious. Such animals should be prioritized to be introduced in rooms that house calmer, less aggressive animals and provide opportunities for hiding to alleviate their anxiety. Indeed, positive social experiences not only promote animal welfare, but also reduce stress related confounds and unexplained data variability. Therefore, by incorporating the animals' temperament into the pair configuration process we increase the likelihood of forming high-quality pairs, both in terms of welfare and the research of which they are a part.

Effect of Housing Conditions on Cortisol and Body Fat Levels in Female Rhesus Macaques

Macaques are among the most commonly used non-human primates in biomedical research. They are highly social animals, yet biomedical studies often require group-living animals to be pair-housed in a controlled environment. A change in environment causes only short-term stress in adapting individuals, while non-adapting animals may experience long-term stress that can adversely affect study results. Individuals likely differ in their ability to adapt depending on individual characteristics. Changes in cortisol and body fat levels may reflect these different individual responses. Here, we investigate the long-term effect of a change from group- to pair-housing on cortisol and body fat levels in 32 female rhesus macaques, exploring whether age, dominance rank, original cortisol, and body fat levels are related to long-term stress in pair-housing. Hair samples were analyzed for cortisol levels, while anthropometric measurements and computed tomography were performed to quantify body fat. Monkeys served as their own control with a 7.5-month period between the measurements. Cortisol levels increased, while average body fat levels did not differ when individuals were moved from group- to pair-housing. Cortisol and body fat levels were not significantly correlated. Changes in cortisol were independent of age and dominance rank, whereas individual variation in body fat alterations was related to the group-housed body fat level and dominance rank. Although this study did not identify individual characteristics related to long-term stress in pair-housing, the individual variation confirms that some individuals are more resilient to change than others and provides possibilities for future refinement studies.

Effects of high-intensity interval training in more or less active mice on biomechanical, biophysical and biochemical bone parameters

High-intensity interval training (HIIT) is of scientific interest due its role in improving physical fitness, but the effects of HIIT on bone health need be carefully explored. Further, it is necessary to know whether HIIT effects on bone health are dependent on the physical activity levels. This may be experimentally tested since we have built a large cage (LC) that allows animals to move freely, promoting an increase of spontaneous physical activity (SPA) in comparison to a small cage (SC). Thus, we examined the effects of HIIT on biophysical, biomechanical and biochemical parameters of bone tissue of C57BL/6J mice living in cages of two different sizes: small (SC) or large (LC) cages with 1320 cm² and 4800 cm² floor space, respectively. Male mice were subdivided into two groups within each housing type: Control (C) and Trained (T). At the end of the interventions, all mice were euthanized to extract the femur bone for biophysical, biomechanical and biochemical analyses. Based a significant interaction from two-way ANOVA, trained mice kept in large cage (but not for trained mice housed in SC) exhibited a reduction of tenacity and displacement at failure in bone. This suggests that long-term HIIT program, in addition with a more active lifestyle correlates with exerts negative effects on the bone of healthy mice. A caution must also be raised about the excessive adoption of physical training, at least regarding bone tissue. On the other hand, increased calcium was found in femur of mice housed in LC. In line with this, LC-C mice were more active (i.e. SPA) than other groups. This implies that an active lifestyle without long-term high intensity physical training seems to play a role in promoting benefits to bone tissue. Our data provides new insights for treatment of osteo-health related disorders.

A Stepwise Male Introduction Procedure to Prevent Inbreeding in Naturalistic Macaque Breeding Groups

Male introductions into captive primate breeding groups can be risky and unsuccessful. However, they are necessary to prevent inbreeding in naturalistic breeding groups. The procedure used to introduce new individuals may affect the success and influence the risks associated with group introductions. At the Biomedical Primate Research Centre (BPRC) in Rijswijk, the Netherlands, male rhesus macaque (Macaca mulatta) introductions into naturalistic social groups with a matrilineal structure and without a breeding male achieve relatively high success rates. This paper describes the male introduction procedure used at the BPRC. Males are stepwise familiarized with and introduced to their new group, while all interactions between the new male and the resident females are closely monitored. Monitoring the behaviour of the resident females and their new male during all stages of the introduction provides crucial information as to whether or not it is safe to proceed. The BPRC introduction procedure is widely applicable and may improve the management of captive primate groups in any housing facility worldwide. Thus, the careful introduction management can minimize the risk associated with male introductions and enhance the welfare of captive primates.

Not all mice are alike: Mixed-strain housing alters social behaviour

The use of millions of mice in scientific studies worldwide emphasises the continuing need for a reduction of sample sizes, however, not at the expense of scientific validity. Split-plot designs have been suggested to enhance statistical power while allowing a reduction of animal numbers in comparison to traditional experimental designs. Recently, a promising approach of a split-plot design has been implemented and proven useful using mixed-strain housing of at least three different mouse strains. However, the impact of co-housing different strains of mice in one cage on animal welfare has still to be defined. This study aimed at comparing the effects of mixed-strain and same-strain housing of female C57BL/6J and DBA/2N mice on welfare and behaviour in two experimental phases. In a first phase, mice were housed in either mixed- or same-strain pairs. Home cage behaviour, activity rhythm, body weight, and faecal corticosterone metabolites were assessed. Furthermore, tests for anxiety-like and exploratory behaviour as well as spatial learning were performed. In a second phase, sociability was investigated in newly formed mixed-strain quartets. Mixed-strain housing did not induce alterations in anxiety, locomotion, learning, stereotypic behaviour, and stress hormone levels. However, changes in social behaviours and activity rhythm were observed. Increased agonistic and decreased socio-positive behaviours might point towards mild impacts on welfare in C57BL/6J mice under co-housing conditions. Altogether, scientific research may greatly benefit from co-housing mice of different strains within the same cages (e.g. for the realisation of a split-plot design), provided that strains are carefully selected for compatibility.

Environmental Complexity and Research Outcomes

Environmental complexity is an experimental paradigm as well as a potential part of animals' everyday housing experiences. In experimental uses, researchers add complexity to stimulate brain development, delay degenerative brain changes, elicit more naturalistic behaviors, and test learning and memory. Complexity can exacerbate or mitigate behavioral problems, give animals a sense of control, and allow for expression of highly driven, species-typical behaviors that can improve animal welfare. Complex environments should be designed thoughtfully with the animal's natural behaviors in mind, reported faithfully in the literature, and evaluated carefully for unexpected effects.

Improved behavioral indices of welfare in continuous compared to intermittent pair-housing in adult female rhesus macaques (Macaca mulatta)

Limiting opportunities for captive nonhuman primates (NHPs) to express species-specific social behaviors may disrupt the adaptive drive for social companionship and may lead to increases in coping behaviors and inactivity. While captive NHPs show improved welfare when moving to pair-housing from single-housing, the impact of daily separation of pair-mates, as is implemented in intermittent pair-housing, is not fully understood. We compared behavioral indices of welfare exhibited by adult female rhesus macaques (Macaca mulatta) in two conditions: (1) intermittent pair-housing, involving daily overnight separation of pair-mates, and (2) continuous pair-housing, involving little separation of pair-mates. A within-subjects study design tested two groups of females experiencing both pairing conditions in an alternate order, switching either from continuous to intermittent pair-housing, or from intermittent to continuous pair-housing. Behavioral observations, recording activity state, self-directed, abnormal, and social behaviors, were conducted at midday when all females were paired, and in the afternoon when intermittent pairs were separated. Females exhibited higher levels of inactivity and self-directed behavior when separated due to intermittent pair-housing in comparison to continuous pair-housing. In addition, intermittently paired females showed higher levels of grooming and other types of affiliation when paired, than during the same time frame when they were continuously paired. These results suggest that females in the continuous presence of a social partner experience improved levels of activity and do not need to elevate levels of behavioral coping mechanisms (e.g., self-scratching, increased affiliation) as they receive the benefits associated with social companionship consistently throughout the day. Overall, this study provides the first evidence that continuous pair-housing affords better welfare than intermittent pair-housing in adult female rhesus macaques. Pair-housing options, such as continuous pairing, that reduce reliance on behavioral coping mechanisms and promote adaptive social behavior throughout the entirety of the day should be prioritized over husbandry care scheduled for convenience.

The Impact of Social and Behavioral Factors on Reproducibility in Terrestrial Vertebrate Models

The use of animal models remains critical in preclinical and translational research. The reliability of the animal models and aspects of their validity is likely key to effective translation of findings to medicine. However, despite considerable uniformity in animal models brought about by control of genetics, there remain a number of social as well as innate and acquired behavioral characteristics of laboratory animals that may impact on research outcomes. These include the effects of strain and genetics, age and development, sex, personality and affective states, and social factors largely brought about by housing and husbandry. In addition, aspects of the testing environment may also influence research findings. A number of considerations resulting from the animals' innate and acquired behavioral characteristics as well as their social structures are described. Suggestions for minimizing the impact of these factors on research are provided.

Effects of weaning age and housing conditions on phenotypic differences in mice

Poor reproducibility is considered a serious problem in laboratory animal research, with important scientific, economic, and ethical implications. One possible source of conflicting findings in laboratory animal research are environmental differences between animal facilities combined with rigorous environmental standardization within studies. Due to phenotypic plasticity, study-specific differences in environmental conditions during development can induce differences in the animals’ responsiveness to experimental treatments, thereby contributing to poor reproducibility of experimental results. Here, we studied how variation in weaning age (14–30 days) and housing conditions (single versus group housing) affects the phenotype of SWISS mice as measured by a range of behavioral and physiological outcome variables. Weaning age, housing conditions, and their interaction had little effect on the development of stereotypies, as well as on body weight, glucocorticoid metabolite concentrations, and behavior in the elevated plus-maze and open field test. These results are surprising and partly in conflict with previously published findings, especially with respect to the effects of early weaning. Our results thus question the external validity of previous findings and call for further research to identify the sources of variation between replicate studies and study designs that produce robust and reproducible experimental results.

Social enrichment by separated pair housing of male C57BL/6JRj mice

Laboratory male mice are often housed individually due to aggressive behavior or experimental requirements, though social isolation can cause welfare issues. As a strategy to refine housing of male mice, we introduce the separated pair housing system. A perforated transparent wall divides the cage into two compartments and allows olfactory, acoustic, and visual communication between the two mice but prevents fighting and injuries. Long-term effects of separated pair housing on well-being and distress of adult male C57BL/6JRj mice were investigated and compared with both single- and group-housed mice. Behavioral analysis after eight weeks in three different housing systems revealed no differences in burrowing performance, social interaction, anxiety, and stress hormone concentrations. However, pair-housed mice built more complex nests compared to single-housed mice and the nest position suggested that pair-housed mice preferred the close proximity to their cage mates. Moreover, pair-housed mice showed less locomotor activity compared to group- and single-housed mice. Body weight was higher in group-housed mice. All in all, no unambiguous long-term beneficial effects of pair housing on the well-being were found. However, the findings emphasized that effects of the housing systems on behavioral, physical, and biochemical parameters must be considered in the design of animal experimental studies.

INSPIRE: A European training network to foster research and training in cardiovascular safety pharmacology

Safety pharmacology is an essential part of drug development aiming to identify, evaluate and investigate undesirable pharmacodynamic properties of a drug primarily prior to clinical trials. In particular, cardiovascular adverse drug reactions (ADR) have halted many drug development programs. Safety pharmacology has successfully implemented a screening strategy to detect cardiovascular liabilities, but there is room for further refinement. In this setting, we present the INSPIRE project, a European Training Network in safety pharmacology for Early Stage Researchers (ESRs), funded by the European Commission's H2020-MSCA-ITN programme. INSPIRE has recruited 15 ESR fellows that will conduct an individual PhD-research project for a period of 36 months. INSPIRE aims to be complementary to ongoing research initiatives. With this as a goal, an inventory of collaborative research initiatives in safety pharmacology was created and the ESR projects have been designed to be complementary to this roadmap. Overall, INSPIRE aims to improve cardiovascular safety evaluation, either by investigating technological innovations or by adding mechanistic insight in emerging safety concerns, as observed in the field of cardio-oncology. Finally, in addition to its hands-on research pillar, INSPIRE will organize a number of summer schools and workshops that will be open to the wider community as well. In summary, INSPIRE aims to foster both research and training in safety pharmacology and hopes to inspire the future generation of safety scientists.

Body weight algorithm predicts humane endpoint in an intracranial rat glioma model

Humane endpoint determination is fundamental in animal experimentation. Despite commonly accepted endpoint criteria for intracranial tumour models (20% body weight loss and deteriorated clinical score) some animals still die before being euthanized in current research. We here systematically evaluated other measures as surrogates for a more reliable humane endpoint determination. Adult male BDIX rats (n = 119) with intracranial glioma formation after BT4Ca cell-injection were used. Clinical score and body weight were assessed daily. One subgroup (n = 14) was assessed daily for species-specific (nesting, burrowing), motor (distance, coordination) and social behaviour. Another subgroup (n = 8) was implanted with a telemetric device for monitoring heart rate (variability), temperature and activity. Body weight and clinical score of all other rats were used for training (n = 34) and validation (n = 63) of an elaborate body weight course analysis algorithm for endpoint detection. BT4Ca cell-injection reliably induced fast-growing tumours. No behavioural or physiological parameter detected deteriorations of the clinical state earlier or more reliable than clinical scoring by experienced observers. However, the body weight course analysis algorithm predicted endpoints in 97% of animals without confounding observer-dependent factors. Clinical scoring together with the novel algorithm enables highly reliable and observer-independent endpoint determination in a rodent intracranial tumour model.

Obesity and Age-Related Changes in the Brain of the Zucker Lepr fa/fa Rats

Metabolic syndrome (MetS) is an association between obesity, dyslipidemia, hyperglycemia, hypertension, and insulin resistance. A relationship between MetS and vascular dementia was hypothesized. The purpose of this work is to investigate brain microanatomy alterations in obese Zucker rats (OZRs), as a model of MetS, compared to their counterparts lean Zucker rats (LZRs). 12-, 16-, and 20-weeks-old male OZRs and LZRs were studied. General physiological parameters and blood values were measured. Immunochemical and immunohistochemical techniques were applied to analyze the brain alterations. The morphology of nerve cells and axons, astrocytes and microglia were investigated. The blood-brain barrier (BBB) changes occurring in OZRs were assessed as well using aquaporin-4 (AQP4) and glucose transporter protein-1 (GLUT1) as markers. Body weight gain, hypertension, hyperglycemia, and hyperlipidemia were found in OZRs compared to LZRs. In the frontal cortex and hippocampus, a decrease of neurons was noticeable in the older obese rats in comparison to their age-matched lean counterparts. In OZRs, a reduction of neurofilament immunoreaction and gliosis was observed. The BBB of older OZRs revealed an increased expression of AQP4 likely related to the development of edema. A down-regulation of GLUT1 was found in OZRs of 12 weeks of age, whereas it increased in older OZRs. The behavioral analysis revealed cognitive alterations in 20-week-old OZRs. Based on these results, the OZRs may be useful for understanding the mechanisms through which obesity and related metabolic alterations induce neurodegeneration.

ADHD medication and the inverted U-shaped curve: A pharmacological study in female mice performing the rodent Continuous Performance Test (rCPT)

BACKGROUND

The rodent Continuous Performance Test (rCPT) is an analogue of human CPTs where mice have to discriminate between target and non-target stimuli. The rCPT offers a readout of attentional performance and impulsive behaviour. This study aimed to determine if female C57BL/6 J mice could be trained in the rCPT since previously published rCPT studies have only used male mice and to study whether the effects of methylphenidate (MPH), atomoxetine (ATX), and dexamphetamine (AMPH) on attention and impulsivity depend on baseline (reference) levels of performance.

METHODS

48 female mice underwent rCPT training. Effects of MPH (1, 2, and 3 mg/kg), ATX (1, 3, and 5 mg/kg) and AMPH (0.3, 0.6, and 1 mg/kg) were assessed in a variable stimulus duration probe. Drugs were administered intraperitoneally and sequentially tested following a Latin-square design. Data were analysed using a repeated measurements mixed effect model and reference-dependent effects were studied.

RESULTS

ATX and AMPH improved performance as seen by increases in discriminability. These improvements were a result of a decreased false-alarm rate. AMPH showed a reference-dependent effect, improving the task performance of low-performing mice and decreasing the performance of high-performing mice. MPH also showed this reference-dependent effects, albeit to a lesser extent. ATX and AMPH decreased premature responses and increased response criterion, but no reference-dependent effects were observed for these parameters.

CONCLUSION

This study presents a novel method to analyse baseline-dependent effects. It shows that the rCPT can be successfully used in pharmacological studies in female mice and demonstrates that the effect of ADHD medication is in line with the inverted U-shape theory of performance-arousal relationship.

A New Look at an Old Drug: Cumulative Effects of Low Ribavirin Doses in Amphetamine-Sensitized Rats

Background

Psychotic states related to psychostimulant misuse in patients with hepatitis C virus infection may complicate acceptance and reaction to antiviral treatment. This observation equally applies to the widely used ribavirin therapy.

Objective

We examined psychomotor and body weight gain responses to low ribavirin doses after cessation of intermittent amphetamine treatment in adult rats to assess its role in neurobehavioral outcome during psychostimulant withdrawal.

Method

The model of amphetamine-induced (1.5 mg/kg/day, i.p., 7 consecutive days) motor sensitization and affected body weight gain was established in adult male Wistar rats. Then, additional cohort of amphetamine-sensitized rats was subjected to saline (0.9% NaCl; 1 mL/kg/day; i.p.) or ribavirin (10, 20 and 30 mg/kg/day, i.p.) treatment for 7 consecutive days. Animals’ motor activity in a novel environment was monitored after the 1^st and the 7^th saline/ribavirin injection. Body weight gain was calculated as appropriate. Determination and quantification of ribavirin in the brain tissue were performed also.

Results

The 1^st application of ribavirin to amphetamine-sensitized rats affected/decreased their novelty-induced motor activity only at a dose of 30 mg/kg. After the 7^th application, ribavirin 30 mg/kg/day still decreased, while 10 and 20 mg/kg/day increased novelty-induced motor activity. These behavioral effects coincided with the time required to reach maximum ribavirin concentration in the brain. Body weight gain during withdrawal was not influenced by any of the doses tested.

Conclusion

Ribavirin displays central effects that in repeated treatment, depending on the applied dose, could significantly influence psychomotor response but not body weight gain during psychostimulant/amphetamine withdrawal.

The effect of group size, age and handling frequency on inter-male aggression in CD 1 mice

Aggression in male mice often leads to injury and death, making social housing difficult. We tested whether (1) small group size, (2) early age of allocation to a group decreases aggression and 3) manipulation increases aggression in male mice. A 14wk study was performed to assess the following conditions in male CD-1/ICR mice: group size (1, 2, or 3), age at grouping (5 or 7wks), and manipulation (daily scruffing or minimal weekly handling). Wounds, body weights, food consumption, nest scores, sucrose consumption, fecal corticosterone and blood for hematology were collected. At the end of the study, mice were euthanized and pelted to assess wounding with the pelt aggression lesion scale (PALS). No signs of acute or chronic stress were observed in any of the groups. Trio housed mice showed less bite wounds than pair housed mice. In general, mice in larger groups ate less but weighed more. Individually housed mice, however, had high nest scores, low body weights, and increased sucrose and food consumption. These results suggest that even when nesting material is provided, individual mice may be experiencing thermal stress. Based on this data, CD-1 mice can successfully be housed for up to 14wks and groups of 3 may be the best for reducing even minor levels of aggression (i.e. wounding).

From Mice to Monkeys? Beyond Orthodox Approaches to the Ethics of Animal Model Choice

Simple Summary

New tools, allowing scientists to make precise changes to mammal genomes, have made possible future increased use of larger mammals in biomedical research, such as primates, pigs, and dogs. This paper addresses ethical issues that are raised by using larger mammals instead of smaller ones in this research. Because scientists who use animals in research follow strict guidelines, we first examine what those guidelines suggest for using larger mammals. We then consider what philosophers, who write about the ethics of animal use, consider as the important questions in evaluating which (if any) animals are acceptable to use in research. We find that philosophical perspectives have typically been interested in the question of when or if animal use is justified, while biomedical research guidance has assumed that animal use is justified but defined specific limits to that use. To address directly the ethical questions that arise in the practice of biomedical research in selecting which animals to use, we consider an approach to ethics that is focused on character and living well (or flourishing). This paper is valuable to society in drawing attention to the ethical questions, rather than merely the scientific issues, that are important in selecting which animals to use in biomedical research.

Abstract

Recent developments in genome editing tools, along with limits in the translational potential of rodent models of human disease, have spurred renewed biomedical research interest in large mammals like nonhuman primates, pigs, and dogs. Such scientific developments raise ethical issues about the use of these animals in comparison with smaller mammals, such as mice and rats. To examine these ethical questions, we first consider standard (or “orthodox”) approaches, including ethics oversight within biomedical research communities, and critical theoretical reflections on animal research, including rights-based and utilitarian approaches. We argue that oversight of biomedical research offers guidance on the profession’s permitted uses of animals within a research setting and orthodox approaches to animal ethics questions when and whether animals should be used in biomedicine; however, neither approach sufficiently investigates the nuances of ethical practices within the research setting. To fill this lacuna, we consider a virtue ethical approach to the use of specific animal models in biomedicine. From this perspective, we argued that limitations on flourishing for large mammals in a research setting, as well as potential human-animal bonds, are two sources of likely ethical tensions in animal care and use in the context of larger mammals.

Group and Single Housing of Male Mice: Collected Experiences from Research Facilities in Sweden

Simple Summary

The mouse is the most commonly used mammal in scientific research, and housed in research facilities around the world. Mice are a social species, but when housing male mice together in a confined environment in the laboratory, aggression is often observed and can be problematic. Fighting or trying to avoid fighting can be stressful. Furthermore, fighting can lead to injuries which can sometimes be fatal. Mouse aggression is therefore a significant welfare problem and has implications on the 3Rs (Replacing, Reducing, and Refining animal use in scientific procedures and education). In this study, we used a survey and workshops to collect the experiences of animal technicians, veterinarians, and researchers at Swedish research animal facilities relating to mouse aggression and what methods of preventing aggression they practice. Both group housing and single-housing as a consequence of aggression was perceived as problematic and stressful for the animals. In line with current recommendations from the literature, participants perceived that aggression occurred less if mice were grouped with litter mates at an early age, that nesting material was transferred at cage cleaning, and disturbance was kept to a minimum. Experience from practice will play a valuable part in developing guidelines for group-housed male mice.

Abstract

Animals used for scientific purposes are protected by EU legislation. Social animals should be kept in stable groups that enable species-typical social behavior and provide individuals with social comfort. However, when group-housing male mice, aggression within the homecage is a common husbandry and welfare problem. Excessive fighting and injuries due to aggression can cause pain and stress, resulting in individuals being euthanized or housed individually. In addition, stress can alter physiological parameters, risking scientific validity and generating larger sample sizes. Mouse aggression, and the consequences thereof, thus opposes the 3R goals of Refining the methods to minimize potential pain and suffering and Reducing the number of animals used. Animal technicians, veterinarians, and scientists using animals have valuable information on how these problems are experienced and handled in practice. We assembled these experiences from laboratory animal facilities in Sweden, mapping problems observed and identifying strategies used to prevent mouse aggression. In line with current literature, less aggression was perceived if mice were grouped before sexual maturity, re-grouping avoided and nesting material transferred at cage cleaning. Preventing aggression will minimize pain and suffering and enable housing of stable groups, leading to more reliable scientific outcomes and is thus of high 3Rs relevance.

Stress-induced changes in group behaviour

Testing animals in groups can provide valuable data for investigating behavioural stress responses. However, conventional measures typically focus on the behaviour of individual animals or on dyadic interactions. Here, we aimed to determine metrics describing the behaviour of grouping animals that can reveal differences in stress responses. Using zebrafish (Danio rerio) as a model, we observed replicated shoals both immediately and 24 hours after exposure to a novel environment, as an assessment of temporal change in response to an acute stressor. We quantified various standard behavioural measures in combination with metrics describing group structure, including different proximity, social, and spatial metrics. Firstly, we showed a high collinearity between most of the analysed metrics, suggesting that they describe similar aspects of the group dynamics. After metric selection, we found that under acute stress shoals had significantly higher shoal densities, a lower variation in nearest neighbour distances and were in closer proximity to the walls compared to the same groups tested 24 hours later, indicating a reduction in acute stress over time. Thus, the use of group metrics could allow for the refinement of behavioural protocols carried out in a range of research areas, by providing sensitive and rich data in a more relevant social context.

Wheel running behaviour in group-housed female mice indicates disturbed wellbeing due to DSS colitis

Voluntary wheel running (VWR) behaviour is a sensitive indicator of disturbed wellbeing and used for the assessment of individual experimental severity levels in laboratory mice. However, monitoring individual VWR performance usually requires single housing, which itself might have a negative effect on wellbeing. In consideration of the 3Rs principle, VWR behaviour was evaluated under group-housing conditions. To test the applicability for severity assessment, this readout was evaluated in a dextran sodium sulphate (DSS) induced colitis model. For continuous monitoring, an automated system with integrated radio-frequency identification technology was used, enabling detection of individual VWR. After a 14-day adaptation period mice demonstrated a stable running performance. Analysis during DSS treatment in combination with repeated facial vein phlebotomy and faecal sampling procedure resulted in significantly reduced VWR behaviour during the course of colitis and increased VWR during disease recovery. Mice submitted to phlebotomy and faecal sampling but no DSS treatment showed less reduced VWR but a longer-lasting recovery. Application of a cluster model discriminating individual severity levels based on VWR and body weight data revealed the highest severity level in most of the DSS-treated mice on day 7, but a considerable number of control mice also showed elevated severity levels due to sampling procedures alone. In summary, VWR sensitively indicated the course of DSS colitis severity and the impact of sample collection. Therefore, monitoring of VWR is a suitable method for the detection of disturbed wellbeing due to DSS colitis and sampling procedure in group-housed female laboratory mice.

Social Interactions in Zoo-Housed Elephants: Factors Affecting Social Relationships

Elephants have complex social systems that are predominantly driven by ecological factors in situ. Within zoos, elephants are held in relatively static social groups and the factors observed driving social relationships in the wild are largely absent. Little research has investigated the effect of social group factors in zoos on elephant social interactions. The aim of this research was to establish whether there is a relationship between social group factors and social behaviour, in order to identify factors that make elephant herds more or less likely to be compatible. Results will facilitate recommendations for optimum social groupings for zoo elephants. Behavioural data quantifying social interactions were collected between January 2016 and February 2017 at seven UK and Irish zoos and safari parks from 10 African and 22 Asian elephants. Social interactions were split into four categories: positive physical, positive non-physical, negative physical and negative non-physical. Social interactions were related to age (positive physical higher and negative non-physical lower in calves than adults), personality (elephants with higher sociability scores engaged in more positive interactions and less negative interactions), presence of calves in the herd (herds with calves had more positive non-physical), relatedness to other elephants in the herd (positive non-physical were higher when relatives were in the group and negative non-physical were higher between unrelated elephants) and species (Asian elephants engaged in more positive non-physical than African elephants). A greater understanding of factors that may contribute to the success of zoo-elephant social groups is important for individual and herd welfare as it will enable evidence-based decisions which have minimal impact on social structures to be executed. This knowledge will enable proactive management approaches to be undertaken and will thus be paramount in ensuring optimal welfare for elephant herds moving forwards.

Long-term metabolic cage housing increases anxiety/depression-related behaviours in adult male rats

There are several reports on unfavourable effects of metabolic cage housing on animal welfare mainly due to the characteristic structures of these cages such as single housing and grid flooring. This study was aimed to compare the effects of long-term metabolic cage housing and conventional housing (normal grouped housing in standard cages) on the anxiety/depression-like behaviours in male rats. Anxiety/depression-related behaviours were evaluated by use of forced swimming test and open field test. Swimming and climbing were significantly lower and immobility duration higher in the metabolic cage group. In the open field test, total distance, mean velocity, time spent in the central area, zone transition, grooming, and rearing scores were significantly lower in the metabolic cage. Moreover, serum corticosterone level was higher in the metabolic cage group. The results of the study indicate that long-term metabolic cage housing may cause an increase in the anxiety- and depression-related behaviours in male rats.

Hierarchical structure and the influence of individual attributes in the captive squirrel monkey (Saimiri collinsi)

The dominance structure of primate social groups varies widely. In addition to the groups' composition, intrinsic attributes such as sex, body size and life experience are important factors that can affect hierarchical dominance relations. All primates are social animals, and the social environment has a direct influence on the physiological conditions of vital systems such as immunological, reproductive and cardiovascular systems. In this study, we analyze the hierarchical structure of Saimiri collinsi in captivity, including the hierarchical structure type, the influence of individual intrinsic characteristics (sex, age, weight and origin-born in captivity or in the wild) based on the prior-attributes model, the relation between agonistic behavior frequency and hierarchical position, and hierarchy steepness, which represents the dominance gradient. We found that the group order was characterized by a partial hierarchy: a dominance position could be occupied by more than one individual simultaneously, including individuals of both sexes. Intrinsic characteristics had no influence on hierarchical structure, with the exception of the male in the highest hierarchical position, which had a markedly larger body than all other group members. Thus, the prior-attributes model did not apply to hierarchical formation of S. collinsi in captivity. Only the frequency of agonistic behavior of males correlated with their hierarchical position, and they differed from all other group members in their more aggressive behavior. The steepness between adjacent positions along the dominance gradient was significant only between the dominant male and the next individual in the group, with a smooth gradient between the other positions in the rank. As the access to resources is directly related to hierarchical dominance, a smooth dominance gradient is to be expected in species that form very large groups, such as wild Saimiri populations.