Recommendations for measuring and standardizing light for laboratory mammals to improve welfare and reproducibility in animal research.

Light enables vision and exerts widespread effects on physiology and behavior, including regulating circadian rhythms, sleep, hormone synthesis, affective state, and cognitive processes. Appropriate lighting in animal facilities may support welfare and ensure that animals enter experiments in an appropriate physiological and behavioral state. Furthermore, proper consideration of light during experimentation is important both when it is explicitly employed as an independent variable and as a general feature of the environment. This Consensus View discusses metrics to use for the quantification of light appropriate for nonhuman mammals and their application to improve animal welfare and the quality of animal research. It provides methods for measuring these metrics, practical guidance for their implementation in husbandry and experimentation, and quantitative guidance on appropriate light exposure for laboratory mammals. The guidance provided has the potential to improve data quality and contribute to reduction and refinement, helping to ensure more ethical animal use.
Competing Interests: RJL has received research grant funding from Philips Lighting/Signify and honoraria from Samsung Electronics. GCB has received research grant funding from the Nova Institute, Toshiba Materials Science, Seoul Semiconductor, BIOS, Robern, and PhotoPharmics Inc. He has a current patent (USPTO 7678140 B2) that is licensed by Litebook Company Ltd. He is a paid member of the PhotoPharmics Scientific Advisory Board; has been a paid consultant by Lutron, Inc. and McCullough Hill LLC; and has received honoraria from the Institute for Functional Medicine. BNG has received funding from Tecniplast to travel and present at a symposium. RAH has received research grant funding from Philips Lighting/Signify and is a scientific advisor for the Good Light Group and Chrono@Work. JST is a co-founder and SAB member of Synchronicity Pharma. SNP has received consulting fees from NASA Ames and Sleep Standards.
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