MATERIALS AND METHODS
Animals and Housing
One-day-old ducklings (n = 110) were obtained from
Maple Leaf Farms, Inc. (Leesburg, IN) and placed
in a controlled environment aviary at Hope College
(Holland, MI) within 5 h hatching. The aviary conditions
adhered to industry standards for 18L:6D cycle,
temperature, humidity, ad libitum access to commercial
feed and pin-metered water (nipple lines), and duck
density (∼0.16 m2/duck). Ducklings were placed into
one of 3 pens: pens with red light (peak at 650 nm,
range = 600 to 710 nm), blue light (peak at 450 nm,
range 395 to 480 nm) and white light (range of 390 to
720 nm; approximately 25 lx). All lights were from fluorescent
bulbs and the energy of all lights was normalized
to the quantal energy of 1.6 × 103 μM photons/m2/s
at the level of the ducks’ heads as determined by spectrophotometry.
Although the red and blue light sources
did not emit a single wavelength of light, the range of
wavelengths does fall within the visible red and blue
spectra, respectively. Ducks were raised on pine litter
and fresh litter was spread twice daily over the entire
pen. All housing and study procedures were approved
by the Hope College Animal Care and Use Committee
following the Institutional Animal Care and Use Committee
guidelines.