Bioenergetics of Hy-Line Brown hens in aviary houses

In considering hen-housing systems, applicable heat and moisture production values are essential to producing properly designed and managed ventilation and supplemental heating systems. The aviary system is one housing type under consideration by egg producers. The aviary system has a much lower bird stocking density and more freedom of movement compared to conventional cage housing. This study was conducted to obtain baseline heat and moisture production values for Hy-Line Brown hens in such barns in the Midwestern US. The study continually monitored the house-level thermal environment, air quality, and bird production performance of two commercially operated 50,000-hen aviary houses over a 19-month period. The two houses used similar management strategies and Hy-Line Brown hens with a 20-week difference in age. Data were collected for a complete flock (17-83 weeks, no molt) in each house. Total heat production (THP) of the hens, house-level moisture production (MP), house-level sensible heat production (SHP), and respiratory quotient (RQ) were determined from monitored variables using indirect calorimetry and mass/energy balance, respectively. Variations in THP, MP, SHP and RQ within the day were delineated. Results of the study showed the THP, house-level MP, house-level SHP and RQ values of 5.94 W/kg, 1.83 W/kg, 4.11 W/kg, and 0.94 for the aviary housing system. The new data are expected to improve the design and operation of building ventilation and supplemental heating system, and ultimately production efficiency of the aviary housing systems. The THP and RQ data will also prove useful to indirect determination of building ventilation rate using CO₂ balance method.