Ventilation rate, balance temperature and supplemental heat need in alternative vs. conventional laying-hen housing systems

An Excel-based spreadsheet model was developed to delineate ventilation rate (VR), supplemental heat requirement (H_s), balance temperature (t_bal, outdoor temperature below which H_s is required), energy consumption and cost for H_s in alternative (aviary and enriched colony) versus conventional cage laying-hen housing systems. The model was then applied to the Midwestern U.S. housing characteristics at winter weather conditions (-30°C to 5°C temperature, 70% RH). Effects of stocking density, target house temperature and RH (t_i, RH _i), building insulation level, and light vs. dark period on VR, t_baland H_s were examined. For the housing characteristics considered, t_bal for the alternative housing systems was found to be 2.5°C to 3.7°C higher than that for the conventional cage counterpart to maintain the houses at 25°C t_i and 60% RH_i. The heater capability needs to be at least 26.6 to 28.4 kW per 10,000 birds for the aviary houses (107,000-bird capacity), and 22.7 kW per 10,000 birds for the enriched colony house (124,000-bird capacity). Annual H_s use was estimated to be 0.17 to 0.25 MJ [kg egg]^-1in the alternative houses. Among the influencing factors considered, t_i and RH_j setpoints have more pronounced impact on t_baland H_s than other factors. The H_s energy cost for the alternative housing systems in the Midwestern US was shown to account for less than 0.5% of the total production cost. The interactive model can be readily used for analysis of other production and climatic conditions.