ASABE Technical Library - Abstract

Abstract. Heat stress in egg production facilities, especially in caging systems, is an ongoing problem for the egg industry, and affects the vast majority of laying hens in the United States. To address this challenge, alternative cooling approaches, including direct wetting of bird surface and cooled perch systems have been developed to provide positive welfare aspect to the laying hens during heat stress events. An experiment in which laying hens were subjected to chronic heat stress was conducted during summer 2014, and is being continued for summer 2015. A caging system with perches in which chilled water is circulated (cooled perch, CP) was equipped with environmental monitoring and thermostatic controls to assess the efficacy of heat stress alleviation, compared to a perch without chilled water (air perch, AP) and a statistical control (CTRL) without any perch. A wireless system for monitoring cage air temperature and relative humidity, water temperature of the perches containing chilled water, and air temperature of AP perches was developed to assess the thermal environment inside the cages. An assessment of the CP system thermal performance, including estimates for heat gains due to convection, conduction from bird, and radiation from surrounding surfaces was done. A database was developed to assist data storage and analysis. Results showed that the CP system performed favorably for the hens. The chiller capacity utilized was marginally capable of maintaining designed cold water temperatures during the heat stress events. A 3.1 to 4.2 kW total heat gain of the cooled perch system with birds perched was observed, with 72, 28 and <1 % from convection, radiation and conduction, respectively. At full chronic heat stress, with all birds on a perch, it is expected that much of the perch heat gain will come from room convective and radiative loading on the perch, rather than from birds.