A Comparison of LED with Fluorescent Lighting on the Stress, Behavior, and Reproductive Success of Laboratory Zebra Finches (Taeniopygia guttata)

Abstract

There are limited evidence-based husbandry recommendations for laboratory zebra finches (Taeniopygia guttata), including appropriate light sources. Light-emitting diode (LED) technology has been shown to improve circadian regulation and reduce stress in some laboratory animal species, such as mice and rats, when compared with cool-white fluorescent (CWF) lighting, but the effects of LED lighting on zebra finches have not been published. We compared the effects of broad-spectrum, blue-enriched (6,500 Kelvin) CWF and flicker-free LED lighting on the behavior, stress, and reproductive outcomes of indoor-housed zebra finches. Using breeding pairs housed in cubicles illuminated with either CWF or LED lighting, we compared the reproductive output as determined by clutch size, hatching rate, and hatchling survival rate. We also compared the behavior of group-housed adult males, first housed under CWF followed by LED lighting, using video recordings and an ethogram. Fecal samples were collected from these males at the end of each recording period, and basal fecal corticosterone metabolite (FCM) levels were compared. A FCM assay for adult male zebra finches was validated for efficacy and accuracy using a capture-restraint acute stress response and parallelism analysis, respectively. The breeding pairs had no significant difference in the clutch size or percent hatching rate, but percent hatchling survival improved under LED with an increased proportion achieving 100% survival. There was no significant difference in FCM between the lighting treatments. However, the activity budgets of the birds were altered, with a reduction in flighted movement and an increase in enrichment manipulation under LED. Overall, these results support the use of blue-enriched, broad-spectrum flicker-free LED as a safe alternative to CWF lighting for breeding and nonbreeding indoor-housed zebra finches.

Figure 1.

Lighting setup and measurements. Each cubicle (n = 3 total) consisted of 1 to 2 racks that were included in the study. Each rack had 3 rows of breeding cages or a single flight cage. (A) Each cubicle contained a hard-wired 4-ft T8-sized fixture in the ceiling and a single 4-ft T5-sized light across each row of breeding cages or each flight cage; inset is a graphic of rack setup. (B) Radiospectrometry measurements were recorded at the cage level from 6 cages in each breeding cubicle and from each flight cage approximately once weekly throughout the study. A representative image of the recording location in the breeding cages is shown. Representative (C) spectral irradiance distributions and (D) normalized temporal flicker or power modulation of the LED (red line) and fluorescent (black line) lights as measured by a handheld spectrometer at the cage level.

Figure 2.

Summary of experiment comparing reproductive success of newly formed male-female zebra finch breeding pairs under fluorescent or LED lighting systems in different, adjacent cubicles. The study timeline for each reproductive pair is demonstrated (A). Pairs were monitored at least twice weekly for an average of 40 d from pairing through 11 d post-hatch (11 dph). Reproductive parameters of breeding pairs housed either under fluorescent lighting (control; white) or LED lighting (experimental treatment; red) are summarized. There was no difference between the 2 treatment groups for bonding time (B) and clutch size (C). Results displayed as scatter plots with the means ± SD. The hatch rate did not differ between the treatments (D), but the hatchling survival rate was significantly higher for the LED-treated pairs (E). Results displayed as scatter plots with the median ± 95% confidence interval. (*, P ≤ 0.05; ns, not significant).

Figure 3.

Summary of experiments evaluating welfare in nonbreeding adult males. (A) Three cage replicates were used, with each cage containing 11 to 16 birds. A cross-over design was used with the males housed under fluorescent lighting and then under LED. Video recordings were made 3 times a week for 4 wk, after a 3-wk acclimation period for each lighting type. Fecal samples were collected at the end of the recording periods at 5 standardized time points in a single day. (B) Behavior time budgets of adult males were created for each lighting treatment type based on an ethogram. Proportions of total activity for each treatment group are displayed as means ± SD to demonstrate relative changes in activity budgets. Pair-wise comparisons were made with Student t tests and Holm-Šídák correction. (C) Diurnal pattern of fecal corticosterone (CORT) in male zebra finches housed under fluorescent or LED lights. Means ± SD are displayed. Fecal CORT did not differ between the 2 treatments and did not significantly fluctuate during the sampling period (2-way ANOVA, time × treatment, P > 0.05; ng/g = ng CORT per g of dried feces; *, P ≤ 0.05).

Figure 4.

Fecal corticosterone (CORT) metabolite assay validation. (A) Schematic of capture/restraint physiologic stress test. Basal fecal samples were collected. Birds were then restrained to generate a stress-induced CORT release. Post-stress samples were collected at 1, 2, 3, and 5.5 h post-restraint. On a separate day from restraint, time-matched fecal samples were collected from unstressed birds from the same cages to serve as controls (n = 4 cages). (B) Stress was induced using either an established “capture/restraint” protocol with an opaque cotton bag (method 1) or a novel protocol with an extended hand capture and new home cage (method 2). Means ± SD over the time course are presented. There was no significant difference between the methods (2-way ANOVA time × stress method, F_4,8 = 1.442, P = 0.305); the results were combined for comparison against unstressed controls. (C) Mean ± SD fecal CORT in stressed male finches compared with time-matched, unstressed controls. Restraint resulted in a significant elevation compared with controls at 2 and 3 h post-stress (2-way ANOVA, time × treatment, P ≤ 0.0001), with a return to baseline by 5.5 h post-stress (Bonferroni post hoc test). (†, P ≤ 0.001; §, P ≤ 0.0001; ng/g = ng CORT per g of dried feces).

Figure 5.

Parallelism between serially diluted standards and pooled fecal corticosterone (CORT) levels detected in feces using ELISA. A log–logit transformed standard curve (Y = −2.210 × X + 6.506, r² = 0.9940, P ≤ 0.0001) and log–logit transformed curve of serial dilutions of fecal extracts collected from adult male zebra finches (Y = −2.262 × X + 6.723, r² = 0.9925, P ≤ 0.0001). The standard curve is indicated by the red line and closed circles. The fecal dilutions are indicated by the black line and open circles.