Analysis of Indoor Climatic Data to Assess the Heat Stress of Laying Hens

Abstract

Heat stress for laying hens means the adverse effects of high indoor thermal environments on their egg production (i.e. fewer eggs, reduced egg mass and thinner eggshells) and feed consumption and health. A commonly-used measure of heat stress for animals is Temperature-Humidity Index (THI). The values of temperature-humidity index above 70 indicate the existence of heat stress for the laying hens. Based on this fact, the decreases in both egg production and dry matter intake (DMI) were separately predicted by using daily total THI load as the driving variable of the mathematical models. THI load is the added values of excessive difference of hourly THI values from the threshold THI value (70) during a day. The daily loss of egg production ranged from 18.48 to 51.32 g egg per hen per day while the daily decrease of DMI ranged from 27.07 to 75.23 g DMI per hen per day for a commercial egg production facility located in Tokat, Turkey during summer seasons of 2003 and 2004. Predictions agreed with real data. Heat stress should be alleviated by modifying feed composition and applying special management strategies.