A Research Facility for Studying Poultry Responses to Heat Stress and its Relief

A control and measurement system was developed for studying physiological responses of poultry to thermal challenges and means of heat stress relief. The system features automatic control of air temperature and relative humidity (RH); manual setting of air velocity [ ± 0.1 m·s -1 ( ± 20 ft·min -1 )]; and continuous recording of surface and core body temperatures of the animal. The target thermal conditions in the animal occupied zone were achieved inside a wind tunnel [0 to 1.5 m·s -1 (0 to 300 ft·min -1 )] that was situated inside an environment-controlled room and re-circulated the room air. Target air temperature [ ± 0.2 ° C ( ± 0.36 ° F)] and RH ( ± 2%) were achieved by controlling the auxiliary heaters and humidifiers in two stages via a programmable measurement and control module and its peripherals. Animal surface temperatures were time-recorded with an infrared thermal imager [0.06 ° C (0.1 ° F) sensitivity]. Core body temperatures [ ± 0.1 ° C (0.18 ° F)] were collected with a surgery-free telemetric sensing unit that output the data to a PC. Moreover, a surveillance video system was used to monitor and archive animal behavior. The system has been used to quantify the responses of laying hens to various thermally challenging conditions and the efficacy of intermittent partial surface wetting in alleviating bird heat stress under these conditions

Optimization of Partial Surface Wetting to Cool Caged Laying Hens

Partial surface wetting to cool caged laying hens (Hy–Line W–98 breed, 34 µ1 wk) was investigated for a range of acute heat challenge conditions. The cooling water required to prevent surface and core body temperatures of the hen from escalating was expressed in terms of water spray interval (SI10, min) at a constant spray dosage (10 mL hen–1) and evaporation rate (ER, mL min–1) of the sprayed water. The thermal conditions used in this study consisted of air velocity (V) of 0.2 to 1.2 m s–1 in combination with air vapor pressure deficit (VPDair) of 2.1 to 5.3 kPa that corresponds to dry–bulb temperature (tdb) of 35³C to 41³C and dew–point temperature (tdp) of 21³C to 27³C. ER was directly proportional to VPDair· V. The empirical relationships provide a basis for optimizing operation of partial surface wetting systems to relieve caged layers of heat stress in commercial production settings

PC–Based Data Acquisition for a Solid Substrate Cultivation Deep Bed Reactor

This work describes an instrumentation and data acquisition system designed for a deep bed reactor used to cultivate Trichoderma longibrachiatum on wheat bran. The system allowed on–line measurements of substrate temperature, oxygen concentration within the reactor headspace, relative humidity and temperature of the inlet air, and inlet airflow rates while maintaining aseptic conditions and without disturbing the cultivation process. An error analysis for the instrumentation and data acquisition equipment was completed and provided insight into the reliability of the sensor readings. The collected data provided quantitative information about the reactor system dynamics which can be used to evaluate and apply environmental control schemes, gain knowledge on microbial growth characteristics, and develop and validate mathematical models describing heat and mass transfer interactions

Transient Overvoltage Testing of Environmental Controllers

The integrated electronic control system will provide a new method for the day-to-day management of environmental control of animal production systems. No standards are currently accepted for transient overvoltage protection of these controllers. To assess the adequacy of existing designs, a test circuit was designed and used for a transient open circuit over-voltage waveform (ANSI/IEEE C62.41-1980) of 16 environmental control units: a maximum spike of 770 V was applied to the power supplies, and a spike up to 100 V was applied to temperature sensor lines. For these relatively mild tests, no failures were noted due to power supply transients, but three units failed when subjected to transients on their temperature sensor lines. From this research it is suggested that an industry standard be adopted to define the minimum transient overvoltage design conditions by which environmental controllers should be tested

Development and Testing of a Low-Cost Condensation Detection System

A condensation sensing and control system was designed to detect condensation using a commercially available leaf wetness sensor (LWS). The leaf wetness sensor was a variable resistance grid-type that responded to moisture on the surface. A circuit was developed to compare the LWS voltage output to a user specified reference voltage, and operate a relay for possible switching of a humidity control device (for example a fan and/or heater). The condensation detection system operation was validated in an environmental chamber in the laboratory using a heat exchanger and water bath. Condensate was immediately detected when the plate was cooled below the dew point temperature of the chamber. When the water temperature increased above the dew point temperature, there was a delay as the moisture evaporated from the plate. Soil and other foreign material were added to the leaf wetness sensor with little effect on system performance. The soil acted to further delay the sensor from drying and predicted slightly longer condensation and recovery periods. The condensation detection system was tested in a transplant growing greenhouse and a grain bin, with operation verified by simultaneously measuring the relative humidity and dry bulb temperature. There were frequent periods of condensation in the greenhouse and the system accurately predicted them. Condensation did not occur in the grain bin, as was verified using the relative humidity and dry bulb temperature. The condensation detection system can provide a low-cost, rugged method for determining periods of condensation without the need for routine maintenance and calibration

Minimum Ventilation for Modern Broiler Facilities

New functions for whole-house broiler heat production as a function of bird age using modern straight run broiler growth rates are presented and compared to values in the literature. The approximations are based on field measurements of environmental conditions in modern broiler housing, using a technique that matches predicted to actual fuel use to estimate partitioning between latent and sensible heat. Development of a program utilizing these approximations to compute ventilation and heating requirements for temperature and humidity control in broiler housing is described. The program utilizes steady-state heat and moisture balances commonly used for design purposes, with hourly or daily time steps. Data input includes bird weight and numbers, house data including overall R-value and size, inside and outside temperature, and relative humidity. The program estimates ventilation for temperature and moisture control, minimum ventilation rate, and supplemental heat required. Example predictions are provided

Mechanical Backup Systems for Electronic Environmental Controllers

A series of mechanical backup systems for electronic environmental controllers is presented for a typical finishing swine barn and a typical tunnel ventilated broiler house. The systems consist of mechanical thermostats and timers used in parallel with the electronic controller, designed to ensure animal survival in the event of controller or related hardware failure. For swine housing, three distinct mechanical backup functions are identified; for broiler housing, four distinct mechanical backup functions are identified. Schematic diagrams of the mechanical backup functions are provided and their implementation is described