Construction and Performance of a Self-Contained, Temperature-Controlled Heat Source (Electronic Chicken) to Quantify Thermal Load during Live Haul of Broilers

Abstract

Abstract. Strategies for quantifying heat loss of broilers on live-haul trailers would be beneficial, particularly under conditions of environmental extremes. We have developed an electronic chicken (a self-contained, temperature-controlled heat source) to simulate the sensible heat loss of a live broiler during the transit and holding periods in commercial live-haul trips. The simulated electronic chicken is an aluminum box, having surface area equivalent to a 2.3 to 2.8 kg broiler chicken (0.13 m2), with a thermostatically controlled power source to maintain the internal temperature at 41°C (typical broiler core body temperature). Different cover materials were tested to identify an appropriate cover that resulted in measured values of electronic chicken heat production being similar to published values of sensible heat production for broilers. A double layer of fleece fabric provided a reasonable match. The sensible heat loss of the electronic chickens exhibited positive correlation with exposed wind, and a positive correlation with temperature gradient between internal and external environment. Wetting the fabric cover of electronic chickens only slightly increased heat loss as compared to the dry fabric cover. Wet fabric cover experienced lower heat loss than that expected from the wetted surface of a live chicken, therefore heat loss under the wet scenario would be underestimated. Electronic chickens were installed in modules on trailers with live chickens during commercial live-haul process under various environmental conditions and different management practices. Measured heat losses from electronic chickens were in the range of 8.2 to 20.3 W with outside temperature of -17°C to 3.0°C in winter, and 4.5 to 6.7 W with 28°C to 34°C in summer. Based on literature-reported sensible heat loss under thermoneutrality, it was determined that the measured air temperature inside the live-haul modules on the trailer in the range of 11°C to 25.1°C during transit (outdoor temperature range of 1.7°C to 22.2°C) and 5.3°C to 21.7°C during holding (outdoor temperature range of -9.1°C to 19.8°C) would allow the live chickens to regulate heat by their metabolism and stay comfortable. For the holding period, the winter trips were mostly in the zone of thermal comfort. In summers, hyperthermic conditions were possible during transit, although additional cooling due to surface wetting of birds as a result of misting (on the farm prior to beginning the transit) could have been beneficial but not detectable by electronic chickens. The electronic chickens can be used effectively as a model to evaluate and identify conditions that cause thermal stress conditions during live-haul conditions and to design systems and strategies to alleviate that stress. Keywords: Broiler transport, Physiological stress, Thermal micro-environment, Thermoneutral zone.