Use of computer vision to automatically identify behaviors of healthy and disease-challenged male broiler chickens

), day 21 (IBV), and day 24 (APEC). A total of 12 behaviors were quantified from 10-min video recordings collected every 2 h between 07:00 and 21:00 from days 14 to 41, divided into four periods: Period 1 (d14-20), Period 2 (d21-27), Period 3 (d28-34), and Period 4 (d35-41). Behavior was primarily driven by age. In control birds, locomotion and exploratory/foraging decreased progressively, while sleeping increased; inactivity remained stable. Time-of-day analysis revealed diurnal patterns with higher afternoon/evening activity and lower sleeping in these periods compared with morning. Relative to controls, Eimeria-infected birds showed variable drinking and sustained increased locomotion and exploratory behavior (periods 1-4), representing a non-classical response to intestinal challenge. IBV+APEC-challenged birds exhibited modest changes: decreased inactivity (period 2) and increased panting (period 4), with largely unchanged activity patterns. Disease challenge altered diurnal patterns, with disease-specific effects on circadian-dependent behaviors. These findings highlight the importance of age-specific baselines and the potential of time-of-day-dependent behavioral analyses and circadian markers for detecting disease-related deviations and enabling early disease detection through automated behavioral monitoring.