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ARS Home » Midwest Area » West Lafayette, Indiana » Livestock Behavior Research » Research » Publications at this Location » Publication #405148
Research Project: Optimizing Welfare for Food Producing Animals

Location: Livestock Behavior Research

Title: Daylight exposure and circadian clocks in broilers: part I—photoperiod effect on broiler behavior, skeletal health, and fear response

Author
item JIANG, SHA - Southwest University
item FU, YIECHI - Purdue University
item Cheng, Heng-Wei

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2023
Publication Date: 12/1/2023
Citation: Jiang, S., Fu, Y., Cheng, H. 2023. Daylight exposure and circadian clocks in broilers: part I—photoperiod effect on broiler behavior, skeletal health, and fear response. Poultry Science. https://doi.org/10.1016/j.psj.2023.103162.
DOI: https://doi.org/10.1016/j.psj.2023.103162

Interpretive Summary: The current lighting regimes with continuous (24 light:0 dark) or near continuous (23 light:1 dark) photoperiod increase broiler growth rate, feed consumption, and feed conversion, but the short resting time may affect broiler health and welfare. The aim of this study was to examine effects of various daylight exposure protocols during the 24-h light (L) -dark (D) cycle on growth performance, skeletal health, and welfare state in broilers. The broilers were randomly assigned to 1 of 4 photoperiod treatments: 20L:4D, 18L:6D, 16L:8D, and 12L:12D. The results indicate that a short photoperiod, close to the natural light cycle, 12L:12D as well as 16L:8D broilers had improved production performance, leg bone health, and suppressed stress reactions when compared to both 18L: 6D and 20L:4D broilers. Study results provide some insights for poultry producers to refine management strategies and improve broiler health and welfare.

Technical Abstract: Environmental photoperiod and related circadian clock, the 24-h light (L)-dark (D) cycle, are important factors in maintaining productive performance, pathophysiological homeostasis, and psychological reaction in humans and animals. Currently, various lighting programs as management tools for providing a satisfactory environmental condition have been used in commercial broiler production. The aim of this study was to examine effects of various daylight exposure protocols during the 24-h L-D cycle on growth performance, skeletal health, and welfare state in broilers. Four hundred thirty-two 1-d-old Rose 308 broiler chicks were assigned to 24 pens (18 birds/pen). The pens were randomly assigned to 1 of 4 thermal and lighting control rooms, then the birds (n=6/treatment) were exposed to : 1) 12L, 2) 16L, 3) 18L, or 4) 20L at 15 d of age. Lighting program effects on bird body weight, behavioral patterns, bone health, and stress levels were evaluated from d 35 to 45, respectively. The birds in the 12L and 16L groups, reared under shorter photoperiods close to the natural 24-h light-dark cycle, had improved production performance, leg bone health, and suppressed stress reactions when compared to the birds in the 18L and 20L groups. Specifically, 12L birds had a greater final body weight and average daily weight gain (P < 0.05), increased BMD and BMC with longer and wider femurs (P < 0.05), a decreased H/L ratio (P < 0.05), and more birds reached the observer during the touch test (P < 0.05) but spent shorter latency during the tonic immobility test (P < 0.05). Taken together, these data suggest that providing 12 h of light per day may be more suitable for broiler production. Further studies will be conducted to investigate the cellular mechanisms underlying the photoperiod effects on broiler health and welfare.