Individual housing influences certain biochemical parameters in the rat

Longitudinal Assessment of Behaviour and Associated Bio-Markers Following Chronic Consumption of β-Sitosterol β-D-Glucoside in Rats: A Putative Model of Parkinson’s Disease

The consumption of cycad (Cycas circinalis) seeds has been linked to the development of Amyotrophic Lateral Sclerosis-Parkinsonism Dementia Complex (ALS-PDC) in humans. ALS-PDC is a clinically variable disease presenting as a combination of symptoms typical of PD and/or ALS. Chronic consumption of β-sitosterol β-D-glucoside (BSSG), a component of the cycad seed, by rats (Rattus norvegicus) has been previously reported to initiate a progressive pathology that develops over several months and manifests as behavioural and histopathological changes that resemble characteristic features of Parkinson’s disease. As part of an independent multi-site validation study, we have tried to replicate and further characterize the BSSG model with a focus on motor function, and associated immunohistochemical markers. Beginning at 3 months of age, male CD^® (Sprague Dawley) rats (N = 80) were dosed orally with either a flour pellet or a flour pellet containing BSSG (3 mg) daily (5×/week) for 16 weeks consistent with previous reports of the model. Following BSSG intoxication, separate cohorts of animals (n = 10/treatment) were exposed to a behavioural test battery at 16, 24, 32, or 40 weeks post-initial BSSG feeding. The test battery consisted of the open field test, cylinder test, and ultrasonic vocalization (USV) assessment. No changes in behaviour were observed at any time point. Following behavioural testing, animals were processed for immunohistochemical markers of substantia nigra integrity. Immunohistochemistry of brain tissue revealed no differences in the microglial marker, Iba1, or the dopaminergic integrity marker, tyrosine hydroxylase (TH), in the substantia nigra at any assessment point. The absence of any group differences in behaviour and immunhistochemistry indicates an inability to replicate previous reports. Further investigation into the sources of variability in the model is necessary prior to further utilization of the BSSG model in preclinical studies.

Environmental Enrichment and Physical Exercise Attenuate the Depressive-Like Effects Induced by Social Isolation Stress in Rats

We assessed the antidepressant-like effects of environmental enrichment (EE) and physical exercise (PE) compared with the selective serotonin reuptake inhibitor fluoxetine against the depression-related neurobehavioral alterations induced by postweaning social isolation (SI) in rats. After 1 month of SI, rats were submitted to PE (treadmill), EE, or fluoxetine (10 mg/kg), which were compared with naïve SI and group-housed rats. After 1 month, behavior was analyzed in the open field (OFT), the sucrose preference (SPT), and the forced swimming (FST) tests. Afterward, the hippocampal serotonin contents, its metabolite, and turnover were measured. SI induced a depression-related phenotype characterized by a marginal bodyweight gain, anxiety, anhedonia, behavioral despair, and alterations of serotonin metabolism. EE produced the widest and largest antidepressive-like effect, followed by PE and fluoxetine, which were almost equivalent. The treatments, however, affected differentially the neurobehavioral domains investigated. EE exerted its largest effect on anhedonia and was the only treatment inducing anxiolytic-like effects. Fluoxetine, in contrast, produced its largest effect on serotonin metabolism, followed by its anti-behavioral despair action. PE was a middle-ground treatment with broader behavioral outcomes than fluoxetine, but ineffective to reverse the serotonergic alterations induced by SI. The most responsive test to the treatments was the FST, followed closely by the SPT. Although OFT locomotion and body weight varied considerably between groups, they were barely responsive to PE and fluoxetine. From a translational standpoint, our data suggest that exercise and recreational activities may have broader health benefits than antidepressants to overcome confinement and the consequences of chronic stress.

Minimum Information in In Vivo Research

Data quality, reproducibility and reliability are a matter of concern in many scientific fields including biomedical research. Robust, reproducible data and scientific rigour form the foundation on which future studies are built and determine the pace of knowledge gain and the time needed to develop new and innovative drugs that provide benefit to patients. Critical to the attainment of this is the precise and transparent reporting of data. In the current chapter, we will describe literature highlighting factors that constitute the minimum information that is needed to be included in the reporting of in vivo research. The main part of the chapter will focus on the minimum information that is essential for reporting in a scientific publication. In addition, we will present a table distinguishing information necessary to be recorded in a laboratory notebook or another form of internal protocols versus information that should be reported in a paper. We will use examples from the behavioural literature, in vivo studies where the use of anaesthetics and analgesics are used and finally ex vivo studies including histological evaluations and biochemical assays.

Recommended housing densities for research mice: filling the gap in data-driven alternatives

Space recommendations for mice made in the Guide for Care and Use of Laboratory Animals have not changed since 1972, despite important improvements in husbandry and caging practices. The 1996 version of the Guide put forth a challenge to investigators to produce new data evaluating the effects of space allocation on the well-being of mice. In this review, we summarize many studies published in response to this challenge. We distinguish between studies using ventilated or nonventilated caging systems and those evaluating reproductive performance or general well-being of adult mice. We discuss how these studies might affect current housing density considerations in both production and research settings and consider gaps in mouse housing density research. Additionally, we discuss reliable methods used to monitor and quantify general well-being of research mice. Collectively, this large body of new data suggests that husbandry practices dictating optimal breeding schemes and space allocation per mouse can be reconsidered. Specifically, these data demonstrate that prewean culling of litters has no benefit, trio breeding is an effective production strategy without adversely affecting pup survival and well-being, and housing of adult mice at densities of up to twice current Guide recommendations does not compromise well-being for most strains.-Svenson, K. L., Paigen, B. Recommended housing densities for research mice: filling the gap in data-driven alternatives.

Home alone: a systematic review and meta-analysis on the effects of individual housing on body weight, food intake and visceral fat mass in rodents

Rats and mice are widely used to study environmental effects on psychological and metabolic health. Study designs differ widely and are often characterized by varying (social) housing conditions. In itself, housing has a profound influence on physiology and behaviour of rodents, affecting energy balance and sustainable metabolic health. However, evidence for potential long-term consequences of individual versus social housing on body weight and metabolic phenotype is inconsistent. We conducted a systematic literature review and meta-analyses assessing effects of individual versus social housing of rats and mice, living under well-accepted laboratory conditions, on measures of metabolic health, including body weight, food intake and visceral adipose tissue mass. Seventy-one studies were included in this review; 59 were included in the meta-analysis. Whilst housing did not affect body weight, both food intake and visceral adipose tissue mass were significantly higher in individually compared with socially housed animals. A combination of emotional stress and lack of social thermoregulation likely contributed to these effects. Increased awareness of consequences and improved specifications of housing conditions are necessary to accurately evaluate efficacy of drugs, diets or other interventions on metabolic and other health outcomes because housing conditions are rarely considered as possible moderators of reported outcomes.

A Miniaturized, Programmable Deep-Brain Stimulator for Group-Housing and Water Maze Use

Pre-clinical deep-brain stimulation (DBS) research has observed a growing interest in the use of portable stimulation devices that can be carried by animals. Not only can such devices overcome many issues inherent with a cable tether, such as twisting or snagging, they can also be utilized in a greater variety of arenas, including enclosed or large mazes. However, these devices are not inherently designed for water-maze environments, and their use has been restricted to individually-housed rats in order to avoid damage from various social activities such as grooming, playing, or fighting. By taking advantage of 3D-printing techniques, this study demonstrates an ultra-small portable stimulator with an environmentally-protective device housing, that is suitable for both social-housing and water-maze environments. The miniature device offers 2 channels of charge-balanced biphasic pulses with a high compliance voltage (12 V), a magnetic switch, and a diverse range of programmable stimulus parameters and pulse modes. The device's capabilities have been verified in both chronic pair-housing and water-maze experiments that asses the effects of nucleus reuniens DBS. Theta-burst stimulation delivered during a reference-memory water-maze task (but not before) had induced performance deficits during both the acquisition and probe trials of a reference memory task. The results highlight a successful application of 3D-printing for expanding on the range of measurement modalities capable in DBS research.

Opportunities to Apply the 3Rs in Safety Assessment Programs

Before a potential new medicine can be administered to humans it is essential that its safety is adequately assessed. Safety assessment in animals forms an integral part of this process, from early drug discovery and initial candidate selection to the program of recommended regulatory tests in animals. The 3Rs (replacement, reduction, and refinement of animals in research) are integrated in the current regulatory requirements and expectations and, in the EU, provide a legal and ethical framework for in vivo research to ensure the scientific objectives are met whilst minimizing animal use and maintaining high animal welfare standards. Though the regulations are designed to uncover potential risks, they are intended to be flexible, so that the most appropriate approach can be taken for an individual product. This article outlines current and future opportunities to apply the 3Rs in safety assessment programs for pharmaceuticals, and the potential (scientific, financial, and ethical) benefits to the industry, across the drug discovery and development process. For example, improvements to, or the development of, novel, early screens (e.g., in vitro, in silico, or nonmammalian screens) designed to identify compounds with undesirable characteristics earlier in development have the potential to reduce late-stage attrition by improving the selection of compounds that require regulatory testing in animals. Opportunities also exist within the current regulatory framework to simultaneously reduce and/or refine animal use and improve scientific outcomes through improvements to technical procedures and/or adjustments to study designs. It is important that approaches to safety assessment are continuously reviewed and challenged to ensure they are science-driven and predictive of relevant effects in humans.

Effects of Varied Housing Density on a Hybrid Mouse Strain Followed for 20 Months

To evaluate the effect of increased housing density in a hybrid mouse strain, we evaluated a panel of physiological and behavioral traits in animals that were housed in groups of 3, 5, 8, or 12, using cages that provide 78.1 in² of floor space. Such groupings resulted in cage densities that ranged from half to almost twice the density recommended by the Guide for the Care and Use of Laboratory Animals. While previous studies have investigated physiological effects of increased housing density using inbred mouse strains, including C57BL/6J and 129S1/SvImJ, this study tested an F1 hybrid population of C57BL/6J x 129S1/SvImJ for changes resulting from either decreased or increased housing density. Mice were followed until they were 20 months old, a substantially longer duration than has been used in previous density studies. We evaluated mortality, growth, home cage behavior, blood pressure, body composition, clinical plasma chemistries, immune function, and organ weights (heart, kidney, adrenal glands, and testes) as endpoints of chronic stress that may arise from sub-optimal housing conditions. Few statistically different parameters were observed in this study, none of which describe chronic stress and all within normal physiological ranges for research mice, suggesting that this hybrid strain was not adversely affected by housing at twice the density currently recommended.

Versatile 3D-printed headstage implant for group housing of rodents

BACKGROUND

An unfavourable yet necessary side-effect of stereotaxic surgery involves the social isolation of post-surgery rats, in order to protect their wound site or skull-mounted implant from damage. Social isolation can cause a myriad of behavioural and physiological changes that are detrimental to the well-being of rats, with potential negative implications for a range of experimental paradigms. New method. Female Sprague Dawley rats (n=40) were implanted onto the skull with a novel 3D-printed headstage socket that surrounded an electrode connector. The socket accommodated a removable stainless-steel headcap for the purposes of protecting the implant. Rats were pair-housed following surgery, and their behaviour was monitored for up to several weeks under two experimental conditions that involved EEG recording and deep-brain stimulation, as well as behavioural test sessions inside an open-field maze. Rat weights were compared between individually- and pair-housed rats at up to 3 weeks post-surgery.

RESULTS

These experiments were successfully carried out using pair-housed rats, with no damage or complications observed regarding the implant and its headcap. Rats were able to carry out a range of normal behaviours including running, grooming, foraging and sleeping. Compared to individually-housed rats, pair-housed rats gained less weight over the 3 weeks post-implantation period. Comparison with existing method(s). This method offers additional protection compared to group-housed post-surgical rats that lack the protective headcap. It is also potentially more practical and versatile than a fully-implantable device for the safe post-surgery group housing of rodents.

CONCLUSIONS

This implant design can reduce the cost of rodent upkeep, whilst potentially avoiding a myriad of behavioural and physiological changes that are known to result from social isolation.

Refining Housing, Husbandry and Care for Animals Used in Studies Involving Biotelemetry

Simple Summary

Biotelemetry, the remote detection and measurement of an animal function or activity, is widely used in animal research. Biotelemetry devices transmit physiological or behavioural data and may be surgically implanted into animals, or externally attached. This can help to reduce animal numbers and improve welfare, e.g., if animals can be group housed and move freely instead of being tethered to a recording device. However, biotelemetry can also cause pain and distress to animals due to surgery, attachment, single housing and long term laboratory housing. This article explains how welfare and science can be improved by avoiding or minimising these harms.

Abstract

Biotelemetry can contribute towards reducing animal numbers and suffering in disciplines including physiology, pharmacology and behavioural research. However, the technique can also cause harm to animals, making biotelemetry a ‘refinement that needs refining’. Current welfare issues relating to the housing and husbandry of animals used in biotelemetry studies are single vs. group housing, provision of environmental enrichment, long term laboratory housing and use of telemetered data to help assess welfare. Animals may be singly housed because more than one device transmits on the same wavelength; due to concerns regarding damage to surgical sites; because they are wearing exteriorised jackets; or if monitoring systems can only record from individually housed animals. Much of this can be overcome by thoughtful experimental design and surgery refinements. Similarly, if biotelemetry studies preclude certain enrichment items, husbandry refinement protocols can be adapted to permit some environmental stimulation. Nevertheless, long-term laboratory housing raises welfare concerns and maximum durations should be defined. Telemetered data can be used to help assess welfare, helping to determine endpoints and refine future studies. The above measures will help to improve data quality as well as welfare, because experimental confounds due to physiological and psychological stress will be minimised.

Long-term social isolation in the adulthood results in CA1 shrinkage and cognitive impairment

Social isolation in adulthood is a psychosocial stressor that can result in endocrinological and behavioral alterations in different species. In rodents, controversial results have been obtained in fear conditioning after social isolation at adulthood, while neural substrates underlying these differences are largely unknown. Neural cell adhesion molecule (NCAM) and its polysialylated form (PSA-NCAM) are prominent modulators of synaptic plasticity underlying memory processes in many tasks, including fear conditioning. In this study, we used adult female Octodon degus to investigate the effects of long-term social isolation on contextual and cued fear conditioning, and the possible modulation of the synaptic levels of NCAM and PSA-NCAM in the hippocampus. After 6½ months of social isolation, adult female degus showed a normal auditory-cued fear memory, but a deficit in contextual fear memory, a hippocampal dependent task. Subsequently, we observed reduced hippocampal synaptic levels of PSA-NCAM in isolated compared to grouped-housed female degus. No significant differences were found between experimental groups in hippocampal levels of the three main isoforms of NCAM (NCAM180, NCAM140 and NCAM120). Interestingly, social isolation reduced the volume of the hippocampal CA1 subfield, without affecting the volume of the CA3 subregion or the total hippocampus. Moreover, attenuated body weight gain and reduced number of granulocytes were detected in isolated animals. Our findings indicate for the first time, that long-term social isolation of adult female animals induces a specific shrinkage of CA1 and a decrease in synaptic levels of PSA-NCAM in the hippocampus. These effects may be related to the deficit in contextual fear memory observed in isolated female degus.

Influence of environmental enrichment on hypothalamic-pituitary-adrenal (HPA) responses to single-dose nicotine, continuous nicotine by osmotic mini-pumps, and nicotine withdrawal by mecamylamine in male and female rats

In the present study, we determined the effects of environmental enrichment (EE; Kong Toys and Nestlets) on sexually diergic HPA axis responses to single-dose nicotine (NIC), single-dose NIC following continuous NIC administration for two weeks, and NIC withdrawal by single-dose mecamylamine (MEC) in male and female rats. Blood sampling occurred before and after MEC and NIC administrations for the determination of adrenocorticotropic hormone (ACTH) and corticosterone (CORT). Supporting and extending our previous findings, EE appeared to produce anxiolytic effects by reducing hormone responses: Male and female rats housed with EE had lower baseline ACTH and significantly lower HPA axis responses to the mild stress of saline (SAL) injection than did those housed without EE. The sexually diergic responses to single dose NIC, continuous NIC, and MEC-induced NIC withdrawal were reduced by EE in many male and female groups. ACTH responses to continuous NIC and MEC-induced NIC withdrawal were blunted to a greater extent in female EE groups than in male EE groups, suggesting that females are more sensitive to the anxiolytic effects of EE. Because EE lowered stress-responsive hormones of the HPA axis in most groups, EE may be a useful intervention for stress reduction in animal models of NIC addiction. As well, the effectiveness of EE in animal studies of NIC withdrawal may enlighten human studies addressing coping styles and tobacco cessation in men and women.

Care of rats with complete high-thoracic spinal cord injury

The complications of spinal cord injury (SCI) increase in number and severity with the level of injury. A recent survey of SCI researchers reveals that animal models of high SCI are essential. Despite this consensus, most laboratories continue to work with mid- or low-thoracic SCI. The available data on cervical SCI in animals characterize incomplete injuries; for example, nearly all studies published in 2009 examine discrete, tract-specific lesions that are not clinically-relevant. A primary barrier to developing animal models of severe, higher SCI is the challenge of animal care, a critical determinant of experimental outcome. Currently, many of these practices vary substantially between laboratories, and are passed down anecdotally within institutions. The care of animals with SCI is complex, and becomes much more challenging as the lesion level ascends. In our experience, the care of animals with high-thoracic (T3) SCI is much more demanding than the care of animals with low-thoracic SCI, even though both injuries result in paraplegia. We have developed an animal care regimen for rats with complete high-thoracic SCI. Our practices have been refined over the past 7 years, in collaboration with animal care centre staff and veterinarians. During this time, we have cared for more than 300 rats with T3 complete transection SCI, with experimental end-points of up to 3 months. Here we provide details of our animal care procedures, including acclimatization, housing, diet, antibiotic prophylaxis, surgical procedures, post-operative monitoring, and prevention of complications. In our laboratory, this comprehensive approach consistently produces good outcomes following T3 complete transection SCI: using body weight as an objective indicator of animal health, we have found that our rats typically return to pre-operative weights within 10 days of T3 complete SCI. It is our hope that the information provided here will improve care of experimental animals, and facilitate adoption of models that directly address the complications associated with higher level injuries.

Atypical antipsychotic medications increase postprandial triglyceride and glucose levels in male rats: relationship with stearoyl-CoA desaturase activity

Recent preclinical and clinical evidence suggests that the stearoyl-CoA desaturase-1 (Scd1) enzyme plays a key role in the regulation of triglyceride (TG) biosynthesis and insulin sensitivity, and in vitro studies have found that antipsychotic medications up-regulate Scd1 mRNA expression. To investigate these effects in vivo, rats were treated with risperidone (1.5, 3, and 6mg/kg/d), paliperidone (1.5, 3, and 6mg/kg/d), olanzapine (2.5, 5, and 10mg/kg/d), quetiapine (5, 10, and 20mg/kg/d), haloperidol (1, and 3mg/kg/d) or vehicle through their drinking water for 40days. Effects on liver Scd1 mRNA expression and an index of Scd1 activity (the plasma 18:1/18:0 ratio, 'desaturation index') were determined, as were postprandial plasma triglyceride (TG), glucose, insulin, and polyunsaturated fatty acid (PUFA) levels. All atypical antipsychotics increased the plasma 18:1/18:0 ratio, but not liver Scd1 mRNA expression, at doses found to also increase plasma TG levels. Among all rats (n=122), the plasma 18:1/18:0 ratio accounted for 56% of the variance in TG concentrations. The plasma 18:1/18:0 ratio was also positively associated with erythrocyte and heart membrane phospholipid 18:1n-9 composition. All antipsychotics except risperidone increased glucose levels at specific doses, and none of the antipsychotics significantly altered insulin levels. The plasma 18:1/18:0 ratio accounted for 20% of the variance in glucose levels. Plasma omega-3 and omega-6 PUFA levels were inversely correlated with the plasma 18:1/18:0 ratio and TG and glucose levels. These in vivo data demonstrate that different atypical antipsychotic medications increase the plasma 18:1/18:0 ratio in association with elevations in postprandial TG and glucose levels, and that concomitant elevations in PUFA biosynthesis oppose these effects.

High-fat diet-induced obesity in animal models

Epidemiological studies have shown a positive relationship between dietary fat intake and obesity. Since rats and mice show a similar relationship, they are considered an appropriate model for studying dietary obesity. The present paper describes the history of using high-fat diets to induce obesity in animals, aims to clarify the consequences of changing the amount and type of dietary fats on weight gain, body composition and adipose tissue cellularity, and explores the contribution of genetics and sex, as well as the biochemical basis and the roles of hormones such as leptin, insulin and ghrelin in animal models of dietary obesity. The major factors that contribute to dietary obesity - hyperphagia, energy density and post-ingestive effects of the dietary fat - are discussed. Other factors that affect dietary obesity including feeding rhythmicity, social factors and stress are highlighted. Finally, we comment on the reversibility of high-fat diet-induced obesity.

A gold standard publication checklist to improve the quality of animal studies, to fully integrate the Three Rs, and to make systematic reviews more feasible

Systematic reviews are generally regarded by professionals in the field of evidence-based medicine as the highest level of medical evidence, and they are already standard practice for clinical studies. However, they are not yet widely used nor undertaken in the field of animal experimentation, even though there is a lot to be gained from the process. Therefore, a gold standard publication checklist (GSPC) for animal studies is presented in this paper. The items on the checklist have been selected on the basis of a literature analysis and the resulting scientific evidence that these factors are decisive in determining the outcome of animal studies. In order to make future systematic reviews and meta-analyses of animal studies possible, to allow others to replicate and build on work previously published, diminish the number of animals needed in animal experimentation (reduction), improve animal welfare (refinement) and, above all, improve the quality of scientific papers on animal experimentation, this publication checklist needs to be used and followed. We have discussed and optimised this GSPC through feedback from interviews with experts in the field of animal experimentation. From these interviews, it became clear that scientists will adopt this GSPC when journals demand it. The GSPC was compared with the current instructions for authors from nine different journals, selected on the basis that they featured a high number of publications on animal studies. In general, the journals' demands for the description of the animal studies are so limited that it is not possible to repeat the studies, let alone carry out a systematic review. By using the GSPC for animal studies, the quality of scientific papers will be improved. The use of the GSPC and the concomitant improvement in the quality of scientific papers will also contribute to decreased variation and increased standardisation and, as a consequence, a reduction in the numbers of animals used and a more reliable outcome of animal studies. It is of major importance that journal editors become convinced of and adopt these recommendations, because only then will scientists follow these guidelines to the full extent.

Enriching the metabolic cage: effects on rat physiology and behaviour

Metabolic cages are used for housing rats and mice for up to five days for collection of urine and/or faeces. The small, barren area of the metabolic cage compromises animal welfare as the animals lack a solid floor, shelter, nest material and social contact. We constructed and tested a practically-applicable enrichment device designed to meet behavioural needs for environmental complexity. The influence of this device on the cage preferences and stress levels of the animals was evaluated. A box-shaped enrichment device was designed and implemented in existing metabolic cages. Male Tac:SD rats were housed for five days in an enriched metabolic cage (EMC; n = 12) or a standard metabolic cage (SMC; n = 12), and data were collected on bodyweight, food and water intake, urination and defaecation, as well as urinary corticosterone and creatinine. Moreover, open-field behaviour and cage preferences were assessed. Rats in both groups gained significantly less weight when housed in metabolic cages. Furthermore, SMC rats failed to increase their weight gain after being housed in the metabolic cage. Defaecation was significantly higher in the SMC than in the EMC and so was urinary creatinine. No group differences were found in open-field behaviour. However, in comparing activity before and after housing in the metabolic cage, only SMC animals exhibited significantly lower total activity. In a preference test, a preference for the tunnel connecting the cages in the preference test and a side preference for the left side were found. This side preference was eliminated when the EMC was placed on the right side, whereas the right side was significantly avoided when the EMC was placed on the left side. Based on these results, we conclude that, to some extent, the enrichment device improved the welfare of rats housed in EMC, compared to those in SMC.

Effect of a cage divider permitting social stimuli on stress and food intake in rats

The need to obtain data from individual laboratory animals has forced many researchers to singly-house small animals. This is costly to the researcher and isolation can adversely affect animal physiology and behavior which in turn may threaten the validity and generalization of experiment results to humans. We assessed the practical use of a housing device - dubbed "Buddy Barrier" (BB) - that allows social stimulation in a paired-housing situation while at the same time permitting the collection of individual measures that traditionally require individual-housing. To assess stress responses to the BB, adult male rats were single or pair-housed for several days with and without a BB in the cage. Fecal corticosterone metabolites (fCORT), food intake and body weight were monitored daily. Plasma CORT and adrenal catecholamine levels were assessed at the end of the housing manipulation. Stress hormone measures did not differ in paired vs. singly-housed rats and paired rats quickly habituated to introduction and removal of the BB. Barring a trend for paired rats to eat more in the first 4 h of the dark, there was no difference in 24 h intakes or body weight gain between singly and paired-housed rats. While the BB attenuated 24 h intakes in both groups, intakes normalized to non-BB conditions by the third BB reintroduction. A device such as the BB can enhance the welfare of animals by providing social enrichment without compromising the integrity of experimental protocols traditionally requiring single-housing. In times of lagging research funding it can also substantially reduce housing costs.

A renewed look at laboratory rodent housing and management

Since its publication in 1996, the Guide for the Care and Use of Laboratory Animals (National Research Council, Washington DC, National Academy Press) has become a primary source of information for institutional animal care and use committees (IACUCs) and research facility managers. In the ensuing years, recommendations relating to laboratory animal care have evolved in response to new scientific information and use of new technology such as ventilated caging. In this article, recent publications are examined to determine the potential impact of new scientific evidence on current practices for the housing and care of laboratory rodents. The discussion points out recent advances in technology and new knowledge of the conditions for the housing of various laboratory rodents, including cage space, single versus group housing, ventilated caging systems, thermoregulation, bedding materials, and enrichment. This new information is provided to aid IACUCs and facility managers in making decisions regarding the housing and care of laboratory rodents.

Physiological profile of juvenile rats: effects of cage size and cage density

Although there is a general consensus that housing conditions affect the well-being of laboratory animals, the ideal cage size and density for housing laboratory rodents has not been established. The authors investigated the effects of cage size and cage density on growth, organ development, metabolic profile, and hemogram in juvenile Sprague-Dawley rats. Larger cages and increased cage density were associated with depressions in body weight and in the weights of several organs. In general, increasing group size and density correlated more strongly with detrimental effects on the growth of females than males, although hemogram values indicated that males are more prone to emotional stress and immune suppression than females in response to increasing group size and crowding.

The effects of individual housing on mice and rats: a review

Isolating an animal refers to the situation where the animal is physically fully demarcated from conspecifics without physical, visual, olfactory and auditory contact. Animals housed in separate cages in the same room are, although deprived of physical and visual contact, still in olfactory and auditory contact, and thus not totally isolated. During the fifties and sixties several studies claimed to show physiological and behavioural differences between individually and group housed rats and mice. The so-called ‘Isolation Syndrome’ characterised by changes in corticosterone levels, metabolism, growth, and behaviour was introduced, rather as a model for psychoneurosis than through any concern for animal welfare. Today, it is often stated as common knowledge in laboratory animal science textbooks that individual housing as well as isolation of rats and mice has an effect on physiology and behaviour. It is, however, unclear whether this effect actually impairs animal welfare.

The aim of this paper is to analyse studies on individual housing of mice and rats to evaluate whether there is documented proof that individual housing affects welfare, and, alternatively whether it is possible to house these animals individually without negative impact on welfare, eg by providing special housing improvements.

A range of studies have shown that individual housing or isolation has effects on corticosterone, the open field behaviour, barbiturate sleeping time and the metabolism of different pharmaceuticals in the animals. However, this review of 37 studies in rats and 17 studies in mice showed divergence in test results difficult to explain, as many studies lacked basal information about the study, eg information on genetic strains and housing conditions, such as bedding, enrichment and cage sizes. Furthermore, test and control groups most frequently differed in cage sizes and stocking densities, and behavioural tests differed in ways which may very well explain the differences in results. Overall, there seemed to be an effect of individual housing, although it may be small, and it seems reasonable to assume that, through making small changes in the procedures and housing environments, the effects can be minimised or even eliminated. More well-controlled and standardised studies are needed to give more specific answers to the questions this issue poses.

Preparation of Animals for Research--Issues to Consider for Rodents and Rabbits

This article provides details to consider when preparing to use animals in biomedical research. The stress of transport and receipt of animals into a new environment mandate the need for a period of stabilization and acclimation. This allotment of time often occurs in conjunction with the quarantine period and permits a stress "recovery" period. Discussions in the article include specific effects of the environment on the animal, such as housing and environmental enrichment. Suggestions are offered regarding how to minimize the effects of procedures and equipment through the use of preconditioning techniques. Guidelines for these techniques and for acclimation should be instituted by the institutional animal care and use committee. Stress and distress are placed in perspective as they relate to the preparation of laboratory animals for research.

Mouse functional genomics requires standardization of mouse handling and housing conditions

The study of mouse models is crucial for the functional annotation of the human genome. The recent improvements in mouse genetics now moved the bottleneck in mouse functional genomics from the generation of mutant mice lines to the phenotypic analysis of these mice lines. Simple, validated, and reproducible phenotyping tests are a prerequisite to improving this phenotyping bottleneck. We analyzed here the impact of simple variations in animal handling and housing procedures, such as cage density, diet, gender, length of fasting, as well as site (retro-orbital vs. tail), timing, and anesthesia used during venipuncture, on biochemical, hematological, and metabolic/endocrine parameters in adult C57BL/6J mice. Our results, which show that minor changes in procedures can profoundly affect biological variables, underscore the importance of establishing uniform and validated animal procedures to improve reproducibility of mouse phenotypic data.

Potential for Unintended Consequences of Environmental Enrihment for Laboratory Animals and Research Results

Many aspects of the research animal's housing environment are controlled for quality and/or standardization. Of recent interest is the potential for environmental enrichment to have unexpected consequences such as unintended harm to the animal, or the introduction of variability into a study that may confound the experimental data. The effects of enrichment provided to nonhuman primates, rodents, and rabbits are described to illustrate that the effects can be numerous and may vary by strain and/or species. Examples of parameters measured where no change is detected are also included because this information provides an important counterpoint to studies that demonstrate an effect. In addition, this review of effects and noneffects serves as a reminder that the provision of enrichment should be evaluated in the context of the health of the animal and research goals on a case-by-case basis. It should also be kept in mind that the effects produced by enrichment are similar to those of other components of the animal's environment. Although it is unlikely that every possible environmental variable can be controlled both within and among research institutions, more detailed disclosure of the living environment of the subject animals in publications will allow for a better comparison of the findings and contribute to the broader knowledge base of the effects of enrichment.

The influences of standard laboratory cages on rodents and the validity of research data

Standard cages for laboratory animals are often small, minimalist and barren. Such cages can compromise animal welfare, indicating that there are welfare-based reasons for improving their designs. However, a second issue, that is, whether animals from standard laboratory housing and husbandry conditions provide valid research data, also indicates that cage designs and husbandry methods need to be improved. This paper reviews various influences of standard laboratory cage design and husbandry. These include their effects on the repeatability of studies, models of neuro-degenerative disease, sensory development, physiology, and behaviour, the effects of standard social housing and standard handling, and the effects of maternal experience on the responses of offspring. These studies show that the development and responses of animals from standard laboratory housing and husbandry conditions are often unrepresentative and idiosyncratic, indicating that data are likely to have reduced external validity. An underlying question is whether animals from standard, barren laboratory cages are ‘abnormal’ and therefore might not provide valid baseline data. In terms of animal welfare, these studies indicate that standard laboratory housing may sometimes be associated both with reduced welfare and with reduced benefits gained from research. It is suggested that in a similar manner to the use of production measures when assessing cages for production animals, laboratory cages could be assessed in terms of their suitability to provide valid research data.

Enrichment of laboratory caging for rats: a review

Rats are a well-understood and widely used laboratory species that should be provided with environmentally enriched caging in line with modern animal welfare guidelines. This paper reviews which sources of enrichment are effective and should be prioritised, and how methods for providing enrichment might be selected using rats’ preferences as a guide. Rats demonstrate high demand for social contact and prefer larger cages, and cages with shelters, nesting material and foraging devices. Rats also discriminate between different methods of providing a given type of enrichment. It is clear that rats should be provided with enrichments such as social contact and shelter, and, in fact, that these should probably be considered basic husbandry requirements rather than optional improvements. It is still difficult, however, for animal caretakers to access proven, standardised methods for providing appropriately enriched caging, and the level of enrichment routinely provided to most rats in the laboratory appears to be low. Further research is required to assess the impact of enrichment upon research variables and to develop commercially viable enrichment products for rats in the laboratory.

Cage size preference in rats in the laboratory

The size of an enclosure is an integral part of how well it accommodates a nonhuman animal's welfare; however, most enrichment studies concentrate on modifying the area inside the enclosure rather than enlarging it. It has been suggested that rats have little need for more cage space, but there is no empirical evidence about rats' need for space. This experiment provides preliminary evidence for the preferences of 5 male and 5 female albino rats using T-maze choices followed by 5 min dwelling times. The rats showed a moderate but significant preference for the larger of 2 cages [540 cm2 vs. 1,620 cm2; binomial z, p <.05]. When the rats shared the chosen cage with 4 familiar cage mates, their preference for the larger cage did not become any stronger [paired t[9] = -.820, p >.05]. The results suggest that rats should be given a somewhat larger space allowance but could share it with up to 4 other rats.

Influence of restraint stress on ligature-induced periodontitis in rats

The influence of stress on periodontal breakdown in Wistar rats was analyzed during experimental periodontitis, induced by placing silk ligatures around the maxillary right second molar teeth. The rats were divided into three groups with 10 animals in each; the first group was exposed to restraint stress for 12 h d(-1) for a period of 4 wk; the second group was exposed to restraint stress for 2.5 h d(-1) for a period of 4 wk; the third group served as a control group. Ligation for 4 wk resulted in an accelerated periodontal degradation, whereas the restraint stress by itself had no significant effect. Combined stress and ligation resulted in a significantly higher attachment loss and alveolar bone resorption than either treatment alone, while no differences were seen between the two stress regimens. After 4 wk, a reduced body weight was found in both restrained groups of rats and a reduced weight of the thymus in the rats restrained for 12 h d(-1), while no changes were observed in the weight or composition of the suprarenal glands. We conclude that stress alone does not result in periodontal disease but may modulate the pathophysiological processes of already present periodontal inflammation, resulting in accelerated degradation of periodontal tissues.

Pair housing induced feeding suppression: individual housing not novelty

Male rats that are moved from individual to pair housing suppress their feeding for a few days [O'Connor R, Eikelboom R. The effects of changes in housing on feeding and wheel running. Physiol Behav 2000;68:361-371]. The present study explored whether the suppression was a result of the period of individual housing or the novelty of the other animal. Two groups of 16 rats were pair-housed and one group of rats was individually housed for 21 days. The individually housed rats were then pair-housed (IP group) and rats in one of the pair-housed groups were re-housed with novel partners (NP group), while rats in the other pair-housed group remained with the same partner (SP group). Feeding was suppressed only for rats in the IP group, suggesting that the novelty of the partner did not suppress feeding, but rather, the change from individual to pair housing did. Water consumption was also measured, but was unaffected by the re-housing manipulation.

The effects of changes in housing on feeding and wheel running

The experiments explored the effects on feeding when rats were moved between individual and paired housing. In Experiment 1, rats moved to paired housing showed a 3-day suppression in feeding (initially 23%) compared to chronically individual- or pair-housed rats. In Experiment 2, half of the rats from the two control groups of Experiment 1 were moved between individual and paired housing on alternate days. Only the rats moved to paired housing showed a feeding suppression (initially 40%), but the nature of the suppression differed from Experiment 1: it appeared that only one rat of each pair showed a feeding suppression. Experiment 3 examined simultaneous introduction of running wheels and moves to paired housing. The feeding suppression induced by the move to paired housing was more immediate and shorter lived than the wheel-induced suppression. Unlike wheel access, paired housing produced only a temporary suppression of body weight. These experiments suggest that the relatively simple manipulation of moving rats from individual to paired housing results in a temporary stress-induced decrease in feeding.