Agricultural engineers develop improved poultry house ventilation system
Ohio farms produce more than 8 billion eggs annually, ranking the state second in the nation. The robust supply meets significant demand, as the average American eats 250 eggs per year.
Technology advances in egg production facilities over the years have enabled very efficient operations of large-scale poultry layer houses. However, existing ventilation systems pose challenges to maintaining healthy indoor air conditions for the flock. Department of Food, Agricultural and Biological Engineering (FABE) Prof. Lingying Zhao and Graduate Research Associate Xinjie Tong have designed an innovative ventilation system to improve indoor environment and limit disease outbreaks in layer houses.
The most commonly used ventilation systems are tunnel ventilation and cross ventilation. With cross ventilation, air enters a layer house through inlets under the eaves or on the ceiling and exits through exhaust fans on side walls. It creates relatively uniform airflow inside the house, but is not able to effectively abate heat stress of hens in the summer. Tunnel ventilation systems have been widely adopted to alleviate heat stress. It provides wind-chill cooling with high-speed air flow across animals, but can create significant air condition and quality variances along airflow pathways. This non-uniformity results in differentiation in hen performance, such as various sized eggs, which is not desirable.
Heat stress is a common problem in layer houses. Under heat stress, hens usually spend less time feeding and moving, and more time drinking, resting and panting. It often results in decreased egg production, reduced egg quality and increased hen mortality. Disease outbreaks are another big threat to the poultry industry. In 2015, the highly pathogenic H5 avian flu infected about 57 million birds in the U.S., resulting in a disastrous loss to poultry and egg industries. Because the flu spread quickly, researchers suspect that the viruses were possibly airborne. The current ventilation systems are not designed for disease control because the air mixing can facilitate the transmission of viruses among hens and hasten the spread of the disease.
To reduce economic losses due to heat stress and disease outbreaks, Zhao and Tong are developing an upward airflow displacement ventilation (UADV) system for commercial layer houses. In this new system, fresh air is uniformly supplied from air ducts located beneath the cages. As it reaches the hens and collects heat, the heated air will escape the cages and flow upward in the aisles due to the buoyancy effect and suction caused by exhaust fans installed on the roof. This upward airflow design allows for the shortest pathways of contaminated air and provides efficient removal of heat, moisture, air pollutants, and viruses compared to existing tunnel and cross ventilation systems.
According to the researchers, computational fluid dynamics simulations show the new UADV system potentially can provide uniform thermal conditions, decrease heat stress and limit disease transmission in layer houses. They look forward to performing practical engineering designs and tests in commercial laying hen farms.