Effects of a 16-hour light, 8-hour dark lighting schedule on behavioral traits and performance in male broiler chickens

The objective of this study was to examine the effects of a 16L:8D lighting schedule from d 2 of age through a 6-wk production trial on the performance and behavior of Cobb broiler males compared with a continuous 24-h light schedule (control). Behavioral tests included social reinstatement behavior measured in runway tests and fear response measured by tonic immobility. The 16L: 8D group had BW and FCR similar to control birds at 6 wk. Based on behavior observations by scan sampling at 0900 to 1100 h and 1400 to 1600 h, the number of chicks eating, drinking, walking-standing, and pecking increased under the 16L: 8D lighting schedule, whereas resting (sitting and sleeping) decreased (P <= 0.05). The 16L: 8D group also exhibited comfort behaviors, such as preening and wing-shaking, more extensively than did control birds (P <= 0.05). Broilers in the 16L: 8D group had a shorter duration of tonic immobility (P <= 0.05) at 11 and 35 d of age, which might represent less fearfulness. In runway tests at 13 and 30 d of age, the 16L: 8D group exhibited shorter latencies to reach the zone of stimulus birds and spent more time near the stimulus birds (P <= 0.05). We therefore suggest that the birds in the 16L: 8D group had a greater degree of sociality. Although we did not measure whole-day activity, we speculate that this greater sociality might have resulted from increased interactions among birds caused by increased activity during the observation periods. The 16L: 8D program tended to have more natural daytime behavioral patterns in broilers, to reduce fearfulness (and thus psychological stress), and to increase sociality. We conclude, based on the morning and afternoon measurements of this study, that birds in the 16L: 8D group had a better welfare status than control birds without affecting 42-d broiler performance of the strain used.