Influence of age, time of day, and environmental changes on vocalization patterns in broiler chickens

Sound analysis of animal vocalizations may provide valuable insights into their emotional state and behavioral responses to environmental stimuli. In broiler chickens, four primary vocalization types-distress calls (DC), short peeps (SP), warbles (W), and pleasure notes (PN)-are well-characterized through sound analysis. The objective of this study was to identify the normal vocalization patterns of broiler chickens throughout the on-farm stage, considering different times of the day (morning, midday, afternoon, and night), and to assess the effects of heat stress (HS) and multifunctional elevated platforms (MP) enrichment on these patterns. The trial included 1,680 male Ross 308 chickens, housed under either thermoneutral or HS conditions during the final two weeks, with half the pens enriched with MP. DC, SP, PN, and W were automatically monitored using custom-build broiler vocalization recognizer. When a vocalization did not fit one of the four categories, it was classified as another type of vocalization (OV). Time of day significantly influenced SP, DC, W, and PN. Throughout the starter, grower, and finisher phases, all treatments exhibited similar vocalization patterns across age and time of the day, highlighting the strong influence of daily periods on vocalizations. SP had the highest frequency in the evening and the lowest at night. DC peaked at midday, while W reached its highest frequency at night and was least frequent at midday. PN were most common at night but significantly lower during midday and evening. SP and DC were the most prevalent vocalizations, while PN occurred less frequently and were most prominent in broilers of 1 week old. W remained consistently low throughout the broilers' lifespan. DC, SP, and OV increased with age, whereas PN declined, indicating a shift and more diverse vocal communication patterns as broilers mature. The presence of MP and HS did not influence vocalization patterns. These results demonstrate significant changes in vocalization patterns with age and time of the day throughout the on-farm cycle, while remaining relatively unaffected by the presence of MP or HS.