Rutger Smets

Automated behavioral monitoring may offer opportunities to assess health in broiler chickens. This study aimed to (i) evaluate behavioral changes following challenge with Eimeria spp. and infectious bronchitis virus (IBV) combined with avian pathogenic Escherichia coli (APEC), and (ii) characterize patterns across age and time of the day. Across four rounds, 132 Ross 308 broilers were assigned to three groups (control, Eimeria, and IBV+APEC), with four replicate pens of 11 birds each. Challenges were applied on day 14 (Eimeria), 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.

Early posthatch nutrition is an important factor influencing broiler health and welfare. This study investigated the effects of delayed access to feed on production and health-related outcomes in slower-growing Hubbard Redbro broilers throughout the production cycle. Three treatments were tested: T0 (immediate access to feed), T24 (24 h delay), and T48 (48 h delay). Physiological, morphological, and welfare-related outcomes were assessed through plasma corticosterone (CORTp), bone measurements, skeletal fluctuating asymmetry (FA), gait score, litter moisture, and femur head necrosis (FHN). Delayed posthatch feeding altered CORTp dynamics in a time-dependent manner. On d 2, T48 birds tended to have lower CORTp compared to T0 (P = 0.068) and T24 (P = 0.089), while this pattern reversed on d 3, with T0 birds showing elevated corticosterone compared to both T24 (P = 0.013) and T48 (P = 0.005). Humerus length was reduced in the T48 group (P = 0.002), and the composite FA index followed a non-linear pattern, with the lowest asymmetry in T24 and the highest in T48. No differences were found in gait score, litter moisture, or FHN. Overall, delayed posthatch feeding had measurable short-term physiological and long-term morphological effects, but did not compromise welfare-related indicators by the end of the production cycle.

Corticosterone (CORT) is the primary avian stress hormone and regulates key physiological processes, but chronically elevated levels can be detrimental. This study simulated chronic stress by exogenously increasing CORT to assess effects on gait score, bone morphometry, immune indicators, and fluctuating asymmetry (FA) in broiler chickens. A total of 60 one-day-old male Ross 308 broiler chickens were allocated to six treatment groups (T0–T5; n = 10 per group). T0 received a placebo and served as the control group, while T1–T5 were gavaged daily with increasing corticosterone doses (1–5 mg/kg body weight). Treatments were administered from day 1 to day 42. CORT did not affect gait score on day 11 (p = 0.232) or day 42 (p = 0.112), but gait score was significantly correlated with body weight (day 11: p < 0.001; day 42: p = 0.004). Elevated CORT reduced bursa diameter (p < 0.001) and increased bursa follicle scores (p < 0.001), while heterophil-to-lymphocyte ratios remained unaffected (p = 0.349). Carcass and bone dimensions decreased consistently with higher doses (p < 0.001), and body weight correlated positively with all bone traits (p < 0.001). Length-to-width ratios increased with CORT dose (p < 0.001). Composite carcass FA showed dose-related variation in carcass asymmetry, with highest in T4, intermediate in T2, T3, and T5, and lowest in T0–T1 (p = 0.026). Trait-specific FA effects were detected for metatarsus length (p = 0.005) and wattle (p = 0.018), while bone FA remained unaffected (p = 0.272). Overall, exogenously increasing CORT impaired growth, suppressed immune function, and increased fluctuating asymmetry, indicating reduced developmental stability.