Why spectrum, not CRI, drives laying
Hens have fewer cone types than humans and read peak wavelengths, not colour rendering. Red near 660 nm stimulates the hypothalamic photoreceptors that govern the reproductive axis, supporting follicle development; blue around 450–480 nm calms birds and aids muscle. A green peak (520–560 nm) supports growth. CRI is a human-centric metric and is irrelevant to the flock, so tune the spectrum per species rather than chasing a high number on the box.
Photoperiod sets the lay cycle
Layers need a stimulatory day length, typically 14–16 h, to sustain clutch size; below about 11–12 h the ovary winds down. The response is photoperiodic, not simply "brighter is better," so a stable schedule matters more than raw intensity. A short, gradual dark period lets birds rest without breaking the stimulatory signal, and any change should be a slow fade, not a step that the bird reads as a season flipping.
Intensity: bright enough to feed, dim enough to calm
Hold 5–15 lux across the floor. Too bright drives aggression and pecking; too dim and birds miss feed and water, which shows up as uneven body weight and a lower share of settable eggs. Measure uniformity, not just the average, because a dark corner is exactly where production quietly drops. A lux map before install turns "about right" into a number you can defend.
Flicker is silent lost production
Chickens detect flicker far above the human threshold. PWM dimming that strobes stresses the flock and suppresses laying, shows up as feather pecking and lowers eggs per hen-housed. Specify 0.1% smooth, non-PWM dimming so the ramp from dark to full is invisible to the birds. A controller running automatic sunrise/sunset curves removes the manual step-change that spikes cortisol and flattens the curve.
What trials show for LED programs
Side-by-side houses running a tuned red/blue program against fixed warm-white typically post 2–5% more eggs per hen-housed and steadier daily output, with the gain concentrated in the peak-lay weeks. The larger lever is often the dimming curve and floor uniformity, not the peak wavelength, so spec the controller and layout before chasing a specific colour. Treat light as a management input with a daily schedule, not a fitting you buy once.
A practical layer-house spec
Red-dominant plus blue LED tubes, 0.1% flicker-free dimming, 5–15 lux with uniformity above 0.7, 14–16 h photoperiod with dawn/dusk fade, and an IP69K, anti-ammonia build for between-flock washdown. Zone the house so dimming tracks bird age: brighter in the rear as birds grow, dimmer at the feed line during lay. One controller, separate curves per zone, pays back faster than a higher lumen figure.