Research note: Individual variability in early-life play and social behaviors of broiler chicks

Play and social behaviors are important in behavioral development as they support neurodevelopment, social bonding, and skills development. The individual differences in performance of these behaviors in poultry are currently unknown. This study assessed individual variability of play and social behaviors in broiler chicks across the first week of life. Seventy-five chicks (25 birds/pen) were randomly placed in three pens. Continuous focal sampling of nine birds (3 chicks/pen; labeled A-I) was performed from D 1-7. The play behaviors assessed were sparring, frolicking, and worm-running, and allopreening was used to assess social behavior. Play initiation was calculated as the number of times a chick initiated play divided by its total play frequency. The duration Bird A performed sparring was greater than Birds B, E, F, and H. Bird C performed a greater amount of frolicking than Bird E. Birds D and I spent more time performing worm-running than Bird G. For play duration tertiles, top-ranked birds for sparring were A, C, and I while bottom-ranked birds were B, E, and H. For frolicking, Birds C, D, and I were top-ranked and Birds B, E, and H were bottom. For the duration of worm-running, top ranks included Birds B, D, and I and the bottom ranks were Birds A, E, and H. For allopreening, Birds A, F, and H were ranked top and Birds B, E, and G were ranked bottom for duration. Bird C had significantly higher odds to initiate play (Odds = 4.06; P = 0.034), and Bird I tended to initiate play behaviors more often (Odds = 3.25; P = 0.07). The duration of sparring strongly positively correlated with frolicking (r = 0.78; P < 0.01) and worm-running (r = 0.83; P < 0.01) and frolicking strongly positively correlated with worm-running (r = 0.80; P < 0.01). Overall, individual differences in play behaviors performance were found in the first week of life. Chicks engaging in one type of play not only performed more play behaviors overall but also showed greater propensity to initiate play.