Laboratory Animals

Assessing laboratory animals’ welfare – their current and/or past subjective affective states – is essential for ethical and regulatory reasons (and central to biomedical research into, for example, pain, nausea or anxiety). But this is challenging; and in the quest for quantification (and perhaps simplicity), it can be tempting to overlook construct validity. Nevertheless, that our indicators have good construct validity – that is, they accurately reflect the construct or concept of interest – is essential. This is true whether we are interested in short-term emotions like fear, longer-term mood-like states such as malaise, or markers of cumulative stress over a project or even a lifespan. Without it, welfare assessments risk being incorrect: inaccurate and unhelpful for the animals they aim to evaluate and assist. Here (summarising text from a forthcoming edited book), I introduce five validatory tests, as well as highlighting the importance of considering indicators’ responsiveness/sensitivity and selectivity/specificity. I also outline how these principles could help improve the construct validation of both humane endpoints and retrospective severity assessments. Careful construct validation can never fully solve the ‘Other Minds’ problem: that animals’ subjective experiences are private (such that we can never measure them, only infer them). However, done well, construct validation would add additional logical rigour to laboratory animal welfare assessment, increase its accuracy, and make benchmarking (e.g. severity classification) more transparent.

Single outcome measures often fall short of the sensitivity and objectivity expected under European Directive 2010/63, particularly in fast progressing disease models. To address this gap, the German Research Foundation consortium FOR2591 collated data from 55 routinely used models in six species and narrowed more than 50 candidate readouts down to a 15-parameter core panel spanning behaviour, physiology, biochemistry and imaging. Quantitative tools such as the Composite Measure Schemes, the endpointR and the Relative Severity Assessment algorithm fuse these multidimensional streams into more objective severity scores that outperform singular readouts such as body weight change and clinical scoring in detecting early distress and refine humane endpoint decisions. More than 10 external laboratories have already integrated the open-source toolbox, illustrating practical scalability. A consortium survey showed that no single metric is both widely applied and consistently valued, underscoring the need for multi-parameter monitoring. Ongoing Phase III analyses extract model specific digital fingerprints that trigger real-time risk alerts in home-cage systems. By providing a shared yet adaptable framework, FOR2591 charts a feasible path toward Directive 2010/63 compliance, improved model validity and individualized animal care, establishing a path of a more evidence-based severity assessment.

COST Action TEATIME unites experts to advance automated monitoring technologies for laboratory animals, with a focus on Home Cage Monitoring (HCM) systems. The use of HCM has great potential to revolutionise welfare monitoring by enabling continuous, non-invasive tracking of physiological and behavioural patterns in group-housed animals within their undisturbed housing environment. These systems capture spontaneous behaviours – such as feeding, grooming, social interactions and sleep cycles – across day and night phases, offering objective data for welfare and scientific assessments. This real-time monitoring might allow for early detection of distress, disease progression and subtle welfare changes, supporting timely interventions and refined humane endpoints. Unlike traditional clinical scoring, which relies on brief daily observations, HCM provides longitudinal, individualised insights and reduces observer bias. It might also facilitate better characterisation of positive affective states, contributing to more holistic welfare evaluations. Despite technological progress, challenges remain in data integration, sensitivity and standardisation across facilities. Effective implementation requires real-time alert capabilities, robust data management, and interdisciplinary collaboration among scientists, veterinarians and data experts. HCM systems should complement – not replace – human expertise, enriching welfare monitoring and scientific reproducibility. Their integration can improve husbandry, refine severity assessments, advancing both animal welfare and scientific replicability.

A continuing professional development (CPD) process should be implemented in all organisations involved in animal research to ensure professionals stay up to date with scientific advancements, best practices and regulations regarding animal welfare and laboratory animal science. These recommendations advocate for a lean and transparent CPD process to maintain the competence of professionals performing functions, roles and tasks outlined in Directive 2010/63/EU throughout a professional’s career. CPD starts after initial training and once individual competence has been achieved. The first step involves creating a CPD portfolio, which the ‘Person(s) Responsible for Training and Competence’ reviews regularly to ensure it aligns with the professional’s personal development plan (PDP). A structured portfolio is proposed for tracking and assessing CPD activities, enabling monitoring. We recommend this monitoring in cycles of up to 5 years.

This document discusses the various types and formats of CPD activities, the minimum CPD requirements for professionals and the essential information that CPD certificates should include. This will be pivotal when developing a common framework for assessing CPD activities across institutions. To conclude, a harmonised CPD strategy that incorporates planning and record-keeping will facilitate mutual recognition and mobility of personnel. Moreover, promoting high-quality CPD will help motivate and reward staff while fostering a culture of care.

The thyroid gland’s proper function is essential for controlling the metabolism, which varies to some extent between the sexes, thus maintaining the homeostasis. This research aimed to investigate differences in the histological structure and number of mast cells in the thyroid gland of male and female rats, and to establish whether there is a correlation between the levels of thyroid-stimulating hormone (TSH) and the activation index (Ia), which quantifies the functional activity of the gland based on histological parameters. Thyroid glands of 20 Wistar rats were analyzed morphometrically and stereologically to determine follicle size, distribution, and volume density of the epithelium, colloid, and connective tissue. Male thyroid glands had more small and medium follicles and a higher volume density of epithelium, while female thyroid glands had more large follicles and a higher volume density of connective tissue. The volume density of colloid was not significantly different between the sexes. The histological structure of the thyroid glands in both groups was in accordance with the measured TSH levels. The correlation between TSH serum levels and Ia were established in both sexes. Both the TSH serum levels and Ia were lower in females compared to males. A higher number of mast cells was noted in the connective tissue of female thyroid glands, compared to those of males, but this difference was not significant. The results of this study indicate that there are differences in the histological structure of male and female rat thyroid glands and that Ia can be used as a reliable complementary parameter for assessment of thyroid gland function.

Laboratory animal welfare has received increasing attention in recent years as housing protocols move toward favoring environments that allow natural behaviors. Within this study, the effects of housing male and female Sprague Dawley rats in standard cages versus taller cages with an upper shelf were investigated. To determine differences in behavior and physiology based upon cage type, home-cage assessment of ultrasonic vocalizations and analysis of fecal corticosterone metabolites, as well as various behavioral tests, were performed. Rats in shelved cages produced significantly less 50 kHz calls, demonstrated better working memory in the spontaneous alternation task and had higher concentrations of fecal corticosterone metabolites. No differences were observed in the open field, elevated plus maze or light–dark box. While no significant treatment differences were found in the ultrasonic vocalization playback paradigm, results confirmed previous evidence of approach behavior upon 50 kHz call playback. The observed differences in behavior and physiology as a consequence of housing conditions inevitably have implications for experimental reproducibility as comparing studies across laboratories may be difficult if different housing parameters are utilized. The results of this study can also be used in guiding future animal welfare protocols given that certain cage modifications such as increased vertical space and/or the presence of a shelf might improve welfare. Investigation of additional parameters and strains of rodents will enhance our understanding of optimal laboratory animal housing conditions.

This work presents the characterization of tembleque (SDtq) rats as a novel animal model for myelination abnormalities, primarily manifesting as tremors and ataxia, which notably declined by 16 weeks of age. This model originated from a spontaneous autosomal recessive mutation in an outbred Sprague Dawley colony. Histological and electron microscopy analyses revealed significant hypomyelination in the central nervous system of SDtq rats compared with wild-type controls. The thoracic spinal cords of SDtq rats exhibited reduced white matter areas, while the gray matter remained consistent. Peripheral nerves showed no change in myelin thickness, though a decrease in axonal diameter was observed. Transcript analysis indicated reduced expression of mature oligodendrocyte markers and increased activity of astrocytes and microglia in SDtq rats, suggesting compensatory mechanisms. Preliminary mapping studies showed that the causative mutation is located on proximal chromosome 19. These findings highlight the SDtq rat as a promising model for studying the underlying biology of myelin disorders and the role of glial cells in leukodystrophies.

The aim of this experimental, descriptive study was to evaluate feasibility, safety and side effects of alfaxalone and midazolam by intranasal instillation for anaesthesia induction in rabbits. We included 26, healthy, female New Zealand White Rabbits undergoing general anaesthesia in context of a study to test different coatings for stifle joint endoprosthesis. Midazolam (0.1 mg/kg) and alfaxalone 3 mg/kg (group 1) or 4 mg/kg (group 2) were mixed and administered intranasally. The number of sneezes, swallows and evasive attempts were recorded. Time to lateral recumbency, presence of salivation, nystagmus, induction and intubation qualities were scored. If intubation was not possible, a top-up of 1 mg/kg alfaxalone was administered intranasally. If still not sufficient, anaesthesia was induced by mask-insufflation of isoflurane. Data were analysed using IBM SPSS Statistics 30.0.0.0 and non-parametric data compared using either a Mann–Whitney test or a chi-square test. Overall, 10 animals assigned to group 1 and 16 animals to group 2 were included in the study. In 24/26 rabbits (92.3%) no significant complications were noted. One rabbit showed 20 s of apnoea after induction and one rabbit died during induction. Top-up dosages of alfaxalone were necessary in three cases and in two of these three, isoflurane administration was also required to complete anaesthetic induction. The median time to lateral recumbency was 32.5 s in group 1 and 15 s in group 2. By intranasal application of midazolam with alfaxalone at both dosages, the anaesthetic state was induced shortly after application.

The use of Vascular Access Buttons™ (VABs) is gaining traction in animal research as a less invasive alternative to traditional venipuncture methods and a superior option compared with existing alternatives, such as vascular access ports (VAPs). By enabling repeated blood collection and intravenous drug administration with reduced stress and discomfort for the animals, VABs contribute to improved data quality and enhanced animal welfare in animal studies. While increasingly used in rodents, their application in non-rodent species remains underexplored. This study evaluated the feasibility and reliability of the VAB system in two Göttingen Minipigs, comparing its performance with the conventional vena cava cranialis puncture. Pharmacokinetic assessments and clinical pathology analyses revealed consistent results across both techniques, demonstrating the VAB system’s ability to generate reproducible, high-quality data. Additionally, its durability and ease of use highlight its potential as a practical and ethical alternative to both traditional venipunctures and VAPs in pharmacokinetic and long-term studies in minipigs. These findings support the integration of the VAB system in toxicological and pharmacokinetic research, particularly in studies requiring repeated blood collection or chronic intravenous dosing.

Isolated kidney perfusion forms the bridge between in vitro and in vivo experiments and is mainly performed with rodent kidneys. It enables the controlled investigation of kidney function without systemic influences and is therefore currently, for instance, considered the gold standard for investigating the regulation of renin release, a central regulator of blood pressure. Renin secretion is controlled by several intrarenal signalling cascades and thus cannot be fully modelled in cell cultures. On the other hand, the in vivo investigation of renin release is confounded by systemic counter-regulatory systemic mechanisms. For ethical and logistical reasons, human kidney tissue has not been used for isolated organ perfusion yet. To reduce the use of rodents and to achieve the translation to larger species, including humans, we developed a method for isolated perfusion of slaughterhouse pig kidney segments. This method allows for future use with human kidney segments obtained from nephrectomies. Pig kidney segments were perfused at constant pressure and renin secretion was determined. The sympathomimetic agent isoproterenol, the Ca²⁺ chelator ethylene glycol tetraacetic acid, the NO-donor S-nitroso-N-acetylpenicillamine and the loop diuretic bumetanide stimulated renin release while angiotensin II suppressed it. These responses were similar to those observed in isolated perfused rodent kidneys, demonstrating that central regulatory mechanisms of renin release are conserved across species and in tissue segments. Moreover, the newly developed model of perfusion of kidney segments of large animals is suitable for the investigation of renin release from human kidneys and provides an ethical method for isolated kidney perfusion in accordance with animal welfare.

The EU Directive 2010/63 on the protection of animals used for scientific purposes, as well as the Swiss Animal Welfare Legislation, demand monitoring and documentation of specific aspects of an animal experiment, including welfare-related issues and the (retrospective) assessment of the severity of the procedures that the animals underwent. A score sheet is an efficient tool for the evaluation of the burden of an animal during an experiment and, if properly designed and used, helps adhere to the 3Rs principle. It must be adapted to the specifics of each experiment and explicitly conceived for it. Several score sheet examples have been published; however, some contain fundamental flaws or are designed for specific settings only, requiring modifications to fit other experimental designs. This paper suggests an eight-step procedure to design a score sheet that can be adapted to any animal species and experimental conditions.