Characterizing the development of normal behaviors in broiler chicks during early life.

In poultry production, behavior is used to evaluate bird welfare and assess the impact of management practices. This research aims to improve scientific understanding of normal development of broiler behaviors during early-life by quantifying their behavioral expressions and diurnal rhythms. Broiler chicks (75, mixed-sex) were randomly placed on day-of-hatch into three pens (25 birds/pen) and three chicks per pen were selected as focal subjects. Behavior was recorded from day 1 to 7 of age and assessed by 24-hour continuous sampling. Behavioral durations were analyzed by age and time-of-day, diversity by the Shannon diversity index, and sequences using time-lag probability transition matrices and a continuous-time Markov chain. As birds aged, the proportion of time chicks spent standing, walking, running, jumping, nudging, eating, drinking, foraging, allopreening, sparring, and worm-running increased whilst environmental pecking and conspecific pecking decreased (quadratic). Sleeping decreased linearly as birds aged while wing-flapping, body-shaking, scratching-self, and frolicking increased. Regarding time-of-day, chicks slept for the highest proportion of time (13.66 %) during the dark period. Walking (1.84 %), running (0.36 %), standing (1.58 %), head-shaking (0.04 %), and frolicking (0.23 %) occurred the most in the morning. Chicks spent the most time jumping (0.12 %, 0.10 %) and body-shaking (0.02 %, 0.02 %) in the morning and afternoon. During the morning and evening, birds allocated the most time towards eating (2.39 %, 2.09 %) and drinking (1.14 %, 0.82 %). Chicks spent the most time sitting (4.05 %) and allopreening (0.09 %) during midday. Birds sparred (0.15 %) the most in the afternoon. Nudging occurred more during pre-dark (0.02 %), dark (0.02 %), and mid-day (0.02 %) than other periods. During the pre-dark period, chicks engaged the most in foraging (0.52 %) and environmental pecking (0.59 %). Wing-flapping was greatest in the afternoon and evening (0.04 %, 0.04 %). Behavioral diversity increased with age. Regarding behavioral sequences, locomotive and resting behaviors were the most likely target behaviors following an antecedent behavior (4th quartile >0.09 %). This study provides valuable insights into the behavioral development of broiler chicks and the various factors, such as age and diurnal rhythm, influencing their behavior.