Vivarium Lighting as an Important Extrinsic Factor Influencing Animal-based Research

Abstract

Light is an extrinsic factor that exerts widespread influence on the regulation of circadian, physiologic, hormonal, metabolic, and behavioral systems of all animals, including those used in research. These wide-ranging biologic effects of light are mediated by distinct photoreceptors, the melanopsin-containing intrinsically photosensitive retinal ganglion cells of the nonvisual system, which interact with the rods and cones of the conventional visual system. Here, we review the nature of light and circadian rhythms, current industry practices and standards, and our present understanding of the neurophysiology of the visual and nonvisual systems. We also consider the implications of this extrinsic factor for vivarium measurement, production, and technological application of light, and provide simple recommendations on artificial lighting for use by regulatory authorities, lighting manufacturers, designers, engineers, researchers, and research animal care staff that ensure best practices for optimizing animal health and wellbeing and, ultimately, improving scientific outcomes.

Scientific and technical assistance on welfare aspects related to housing and health of cats and dogs in commercial breeding establishments

“…However, continuous exposition of light (24:0 light:dark) was disruptive for the reproductive rhythms in cats, since the queens' reproductive cycle and hormone production were impaired. This agrees with the principle that reproduction in animals can be altered by an aberrant administration of light (Dauchy and Blask, 2022).…”

“…As aforementioned, in cats, the light influences the release of hormones (Dauchy and Blask, 2022). Leyva et al (1984) investigated the effects of different photoperiods on melatonin, prolactin (PRL) and cortisol plasma levels.…”

“…Exposure to extended photoperiods is reported to alter the melatonin-to-serotonin ratio and compromise the synthesis of important enzymes for the correct functioning of the central nervous system (Morgan and Tromborg, 2007). Moreover, exposition to light at night increases the risk of physiological and behavioural circadian rhythms disruption (Dauchy and Blask, 2022). In contract to constant lighting, in the study by Levya et al (1984) the cats kept under 8:16 and 14:10 light:dark schemes were able to maintain their hormonal secretion rhythms.…”

“…3) Can controlling the frequency of pregnancies have beneficial impact on health and welfare of bitches and queens by preventing physical exhaustion? However, for welfare reasons it is important that there is a natural and gradual dark/light switch (Dauchy and Blask, 2022).…”

“…Reasoning Dauchy and Blask (2022) reported that setting parameters for artificial lighting is important for dogs but no studies were retrieved to suggest a specific setting. Schork et al (2022): relation between sleep and daylength (more than 12 h of natural daylight could affect sleeping behaviour).…”