Design and Performance of an Experimental Cooled Perch System for Heat Stress Relief of Laying Hens

Abstract

<p>This article summarizes the engineering design and performance of a cooled perch system used in a multi-year collaborative study to evaluate cooled perch effects on hen production, health, and welfare during heat stress. The cooled perch system consisted of two replicates (CP-1 and CP-2) of three-tier cage units with galvanized perch pipes forming a complete loop in each tier (top, middle, bottom) in which chilled water circulated. A total of 324 White Leghorns at 17 weeks of age were randomly assigned to 36 cages (76 cm × 52 cm × 48 cm) in six banks placed in the same room. Flow for each loop was provided by loop pumps that drew chilled water from an open thermal storage manifold and returned it to the same manifold. Each thermal storage was cooled by continuously circulating water through a water chiller. Each loop pump was thermostatically controlled based on the cage air temperature. The water inlet and outlet temperatures, cage air temperatures, and loop water flow rates during stable system operation were measured for performance evaluation. Mean water flow rates in 2015 were 5.19 and 5.45 kg min-1 for CP-1 and CP-2, respectively, but significantly declined to 3.91 and 4.03 kg min-1 in 2016. The mean loop water temperature rise was about 2°C for both replicates. The mean loop net heat gain of CP-1 and CP-2 ranged from 690 to 850 W and from 551 to 1,298 W, respectively, with a significant difference between CP-2 loops (p < 0.0001), indicating a discrepancy between the manufacturer’s pump curve and field performance. There was a correlation between room air temperature and net heat gain for all loops of CP-1 and the top loop of CP-2 (p < 0.0001), suggesting that natural convection and radiation from the room to the pipe were the major contributors to loop heat gain. The average daily net heat gain was approximately 2,334 W per replicate, 256 W m-1 perch length, or 43.2 W per hen housed. This analysis provides a baseline for future cooled perch system design in other application settings. An example is provided for sizing the thermal water storage and chiller capacity. In addition, a closed water system with a properly sized expansion tank is recommended for future energy-efficient cooled perch applications.</p>