Physiology of Stress and Welfare in Laboratory Animal Science

In laboratory animal science, understanding the physiology of stress and welfare is essential for ensuring the integrity of scientific research and the well-being of the animals. Stress may arise from environmental and procedural factors that disrupt homeostasis and affect physiological and psychological functions, influencing experimental outcomes.

Environmental and Procedural Stressors

Laboratory animals encounter multiple stressors during routine maintenance and experimentation. Environmental factors—light, noise, temperature fluctuations, cage cleaning, and transport—can induce stress responses (Castelhano-Carlos & Baumans, 2009). In addition, routine procedures such as handling, restraint, surgical interventions, injections, and anesthesia (especially in disease models) contribute to physiological disturbances that may affect cardiovascular, immunological, and metabolic functions (Layton et al., 2023).

Physiological Mechanisms of Stress

When a laboratory animal is exposed to stress, a cascade of responses is initiated:

• Hypothalamic-pituitary-adrenal (HPA) Axis Activation Releases cortisol (in rodents) or corticosterone (in other species) Increases blood glucose, suppresses immune responses, and alters neural activity. Elevated glucocorticoid levels can influence behavioral and pharmacological study outcomes
• Sympathetic Nervous System (SNS) Activation Initiates the “fight-or-flight” response with the release of adrenaline and noradrenaline. Increases heart rate, blood pressure, and respiration. Chronic activation may affect tumor growth, neuroplasticity, and inflammatory responses

?? Studies have indicated that gentle handling methods can substantially reduce the activation of these stress pathways, contributing to more consistent experimental results.

Impact on Animal Welfare and Research Data

Stress can manifest as both behavioral and physiological symptoms, including altered pain thresholds, anxiety, and reduced predictability in responses (Wiepkema & Koolhaas, 1993). Such changes can lead to variability in experimental data, affecting reproducibility and the validity of research findings (Bailey, 2018). Moreover, stress-induced physiological alterations in immune function and metabolism may compromise the translational value of laboratory studies. Environmental enrichment—such as providing nesting materials, toys, and opportunities for social interaction—has been shown to reduce stress and promote natural behaviors (Lee et al., 2023; Charles, 2024). In social species like rodents and primates, stable group housing is crucial in maintaining welfare (Olsson & Westlund, 2007).

Enhancing Welfare and Minimizing Stress

Refinements in animal care and handling can lead to significant improvements in both welfare and research quality. Recommended strategies include:

• Gentle Handling Techniques: Using tunnel handling instead of tail-picking to minimize corticosterone spikes.
• Environmental Enrichment: Providing opportunities for natural behaviors through toys, nesting material, and social housing.
• Refinement of Experimental Procedures: Incorporating preemptive analgesia, improved anesthesia protocols, and habituation routines to reduce procedural stress.
• Non-Invasive Monitoring: Utilizing AI-assisted behavioral tracking and thermal imaging to detect early stress markers without additional stress from direct handling.

?? Evidence indicates that well-enriched environments and refined handling reduce stress hormone levels, supporting improved learning, memory, and overall research consistency.

Professional Quality of Life for Laboratory Personnel

The welfare of laboratory animals is interlinked with the quality of life experienced by laboratory personnel. Elevated stress and compassion fatigue among these professionals can impede optimal animal care. Enhanced social support, increased control over challenging procedures (such as euthanasia), and improved working conditions contribute to better animal and staff outcomes (Rumpel et al., 2023; LaFollette et al., 2020).

Future Directions in Stress and Welfare Research

Innovative approaches are emerging to improve further laboratory animal welfare and the reliability of scientific data:

• AI-Powered Behavioral Monitoring: Real-time activity tracking facilitates early detection of stress.
• Physiological Biomarkers: Advanced non-invasive assessments help in monitoring stress hormone levels.
• Gene Expression and Epigenetic Studies: Investigating how stress influences gene expression and neuroplasticity.
• Personalized Welfare Approaches: Tailoring environmental enrichment and handling protocols to individual animals’ responses.

?? These developments are poised to refine animal welfare protocols further and support data-driven laboratory animal science improvements.

Join the Conversation

How do you address stress and welfare in your laboratory research? Have you implemented new handling techniques or non-invasive monitoring technologies? Engage in the discussion to explore innovative strategies for reducing stress in laboratory animals. ??

References

Castelhano-Carlos, M., & Baumans, V. (2009). The impact of light, noise, cage cleaning and in-house transport on welfare and stress of laboratory rats. Laboratory Animals, 43, 311–327. https://doi.org/10.1258/la.2009.0080098

Layton, R., Layton, D., Beggs, D., Fisher, A., Mansell, P., & Stanger, K. (2023). The impact of stress and anesthesia on animal models of infectious disease. Frontiers in Veterinary Science, 10. https://doi.org/10.3389/fvets.2023.1086003

Wiepkema, P., & Koolhaas, J. (1993). Stress and Animal Welfare. Animal Welfare. https://doi.org/10.1017/s0962728600015876

Lee, G., Kim, K., & Jo, W. (2023). Stress Evaluation of Mouse Husbandry Environments for Improving Laboratory Animal Welfare. Animals: an Open Access Journal from MDPI, 13. https://doi.org/10.3390/ani13020249

Charles, S. (2024). Effects of Environmental Enrichment on Stress and Welfare in Laboratory Animals. Animal Health Journal. https://doi.org/10.47941/ahj.1776

Meyer, N., Kr?ger, M., Thümmler, J., Tietze, L., Palme, R., & Touma, C. (2020). Impact of three commonly used blood sampling techniques on the welfare of laboratory mice: Taking the animal’s perspective. PLoS ONE, 15. https://doi.org/10.1371/journal.pone.0238895

Olsson, I., & Westlund, K. (2007). More than numbers matter: the effect of social factors on behaviour and welfare of laboratory rodents and non-human primates. Applied Animal Behaviour Science, 103, 229–254. https://doi.org/10.1016/J.APPLANIM.2006.05.022

Bailey, J. (2018). Does the Stress of Laboratory Life and Experimentation on Animals Adversely Affect Research Data? A Critical Review. Alternatives to Laboratory Animals, 46, 291–305. https://doi.org/10.1177/026119291804600501

Rumpel, S., Kempen, R., Merle, R., & Thoene-Reineke, C. (2023). Psychological stress and strain in laboratory animal professionals – a systematic review. Laboratory Animals, 57, 396–411. https://doi.org/10.1177/00236772221129111

LaFollette, M., Riley, M., Cloutier, S., Brady, C., O’Haire, M., & Gaskill, B. (2020). Laboratory Animal Welfare Meets Human Welfare: A Cross-Sectional Study of Professional Quality of Life, Including Compassion Fatigue in Laboratory Animal Personnel. Frontiers in Veterinary Science, 7. https://doi.org/10.3389/fvets.2020.00114