Early Dark Periods Do Not Reduce Broiler Performance
Poultry producers spend thousands on continuous lighting early in their chicks’ lives, believing it drives better growth. New research from the University of Georgia just shattered this costly myth.
A comprehensive four-part study involving both controlled trials and commercial field tests revealed that broiler chicks given just 18-20 hours of light daily (with 4-6 hours of darkness) achieved identical final weights, feed conversion ratios, and mortality rates compared to birds under 24-hour continuous lighting (Ashabranner et al., 2025).
The industry has long operated under the assumption that Day 7 weights predict final flock performance. This research proves otherwise. While birds given early dark periods initially weighed less during the first week (182g vs 188g), they demonstrated remarkable compensatory growth, typically matching continuous light groups by Day 10 (306g vs 299g). In one study the early dark group even surpassed the 24-hour light control group by Day 14 (Ashabranner et al., 2025).
The biological mechanism behind this involves melatonin production. Chicks provided with dark periods from day one showed melatonin levels up to three times higher than continuously lit birds. These elevated levels persisted for up to 35 days (Ashabranner et al., 2025), potentially enhancing immune function and stress resistance.
Perhaps most striking was the consistency across all four experiments, including commercial field trials with thousands of birds. No performance penalties emerged from providing natural dark periods from placement (Ashabranner et al., 2025).
This challenges producers to reconsider expensive continuous or near continuous lighting programs. Dark periods reduce energy costs while improving welfare standards without sacrificing productivity. Birds naturally adjust their feeding patterns during these rest periods, maintaining growth performance while expressing natural behaviors.
However, optimizing lighting programs requires precise monitoring to ensure management changes deliver expected results. Accurate, frequent weight data becomes essential for validating that operational tweaks are actually improving profitability rather than masking problems.
Modern automatic weighing systems provide the continuous data streams necessary to detect subtle performance changes quickly, enabling producers to fine-tune their operations with confidence.
Source:
Ashabranner, G.G., et al. „Evaluating the effect of daylength (24, 20, and 18 hours) during brooding on broiler performance and physiological responses to light environment.“ Journal of Applied Poultry Research, 2025.