Enhancing CO₂-based ventilation estimates in goat barns: introducing a day-night activity parameter

Gas emissions in naturally-ventilated barns are usually estimated from ventilation rates, with the CO2 balance as indirect method for daily estimates. Adding an animal activity parameter improves hourly accuracy. This study addresses the current gap on day and night activity parameters for estimating barn ventilation flow in goat farms, based on indoor CO2 concentrations, and provides new insights into goat activity patterns. Animal activity was indirectly monitored by video recording on three dairy goat farms in northern Italy. The videos were analysed every 15 minutes using a scan sampling method, to compile an ethogram of the main states and point behaviours. The percentage of active animals (i.e., performing feeding, moving, and drinking behaviours) was calculated for each scan and normalized to the daily average, to obtain an hourly activity value. The average, minimum, and maximum annual hourly activity levels were then determined separately for daytime (06:00–20:00) and nighttime (21:00–05:00). The mean annual activity parameters (i.e., variation of maximum and minimum activity from average) for day and night was 0.46 and 0.70, respectively. These parameters were included as constants in the sinusoidal dromedary model (which also includes a sine function to represent the periodic daily cycle, and a parameter to account for the time of day when activity is at its minimum) to estimate the relative animal activity.