By Olga Burenkova
Olga V. Burenkova(1), Rory D. Lippert(1), Jacqueline M. Lavery(1,2)*, and Georgia J. Mason(1)
- Campbell Centre for the Study of Animal Welfare/Dept. of Integrative Biology, University of Guelph, Ontario, Canada
- Open Philanthropy
*These authors contributed equally to this work
Previous research from our lab revealed a link between the negative effects of the non-preferred barren (BH) housing condition on zebrafish welfare and cognition. The present pilot study examines the neurobiological mechanisms that may underlie these negative effects.
Ten zebrafish brains were collected from fish previously housed in either BH or well-resourced (WR) tanks, containing gravel and grass, after approximately 20 months of differential housing. Blinding was implemented to housing condition to ensure objective measurements of brain cell density and blood vessel density in three regions of interest: dorsolateral telencephalon, dorsomedial telencephalon (both involved in learning), and the optic tectum (involved in visual processing and coordinating appropriate behavioral responses). Statistical analysis included non-parametric methods and was also performed blind to housing condition.
Fish raised in BH tanks displayed significantly lower brain cell density in the dorsomedial telencephalon compared to barren tank fish (Mann-Whitney U = 2, p = 0.038). No significant differences were observed in other brain regions or for blood vessel density.
In our upcoming research, we are planning to increase statistical power, explore additional variables such as sex differences, and broaden the biological markers to include markers of proliferation, neuronal plasticity, and of metabolic activity. The observed link in this and previous studies between housing conditions, cognition, and brain cell proliferation underscores the importance of considering animal welfare in laboratory settings. Non-preferred barren environments not only hinder cognitive improvements but also induce stress-related issues associated with barren housing conditions such as suppressed brain cell proliferation. By prioritizing the well-being of research animals and adopting more naturalistic housing conditions, we can improve the translatability of animal research and contribute to advancements in biomedical science while upholding ethical standards.
