Wren, M. A., Dauchy, R. T., Hill, S. M. et al. 2013. Colored enrichment devices influence behavior and circadian metabolism and physiology in Sprague-Dawley rats. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 608 (Abstract #PS2).

Enrichment devices and strategies, as currently endorsed by the Guide, are used to improve laboratory animal health and wellbeing. Many conclusions supporting this premise, however, are based primarily on observational studies with minimal consideration for circadian physiology and metabolism. Our previous studies demonstrated that spectral transmittance (color) of light passing through laboratory rodent caging impacts normal rhythms of physiology and metabolism in rats. Here, in conjunction with our GLAS-supported studies, we examined how the use of colored enrichment devices can influence laboratory rodents’ daily circadian melatonin signal and alter temporal coordination of normal physiologic functions. Adult male Sprague–Dawley rats (Crl:SD; n = 6 per group) were maintained on a lighting regimen 12:12-h light:dark cycle (300 lx; 123.0 μW/cm2; lights on 0600) in standard polycarbonate translucent clear rodent cages containing either polycarbonate translucent clear (C), amber (A), red (R), or PVC opaque (O) tubing (3 in. wide × 6 in. long; 1/8 in. wall thickness). After 1 wk acclimation, animals were assessed during light phase for time spent within the colored enrichment devices (CEDs) and for arterial plasma melatonin at 6 circadian time points (beginning at 0400). Results revealed no differences in dietary or water intake, or body growth rates among the groups. Time spent within the CED groups during light phase in week 2 of the study was significantly longer in duration (P < 0.05) at 40.3 ± 10.1% (R), 15.3 ± 3.8% (A), 9.4 ± 2.8% (O), and 1.0 ± 0.6% (C), respectively, compared with that of week 5 with R (5.3 ± 2.9%) > A (1.3 ± 1.2) > C (1.1 ± 0.6%) > O (1.0 ± 0.4%). Plasma melatonin levels in pg/mL (mean ± 1 SE) were low in the light phase (>10.0 ± 0.2) in all groups, but significantly higher (P < 0.05) during dark phase (0400) in group A (213 ± 74), compared with groups R (109 ± 21), C (92.0 ± 35.0), and O (64 ± 18). These findings indicate that use of colored enrichment devices impact behavior and circadian regulation of neuroendocrine parameters that influence laboratory animal health and wellbeing.