Abstract
Gas production in broiler houses and their emissions are closely related to the microclimate established inside the house according to air temperature, humidity, and velocity. Therefore, the internal house environment is influenced by building typology and ventilation system. The objective of the present study was to evaluate ammonia emission rates in broiler houses equipped with different ventilation systems (negative or positive pressure) and litter conditions (new or built-up). The environment of six commercial broiler houses was evaluated internal and external NH3 concentrations. Ventilation rates were recorded to estimate ammonia emission rates. The efficiency of circulation and exhaust fans was assessed, and higher ventilation rates were determined in negative-pressure houses due to the higher flow of the fans. Houses with new litter increased ammonia emission rates along the rearing period, indicating the relationship between gas emissions, bird age and ventilation rates, and presented a typical curve of NH3 emission increase. Negative-pressure houses with built-up litter presented higher emission rates during the first rearing week due to the high NH3 concentration during the brooding period, when the ventilation rates required to maintain chick thermal comfort are low. Although the results of the present study indicate an advantage of the positive-pressure systems as to gas emissions, further research is needed reduce gas emissions in broiler houses with negative-pressure systems.
Highlights
The broiler industry is one of the most technology-intensive and automated livestock activities
The inaccuracy in the evaluation of gas emissions is probably due to factors such as long ventilation systems inside the poultry houses, and the complexity of measurement of air renewal in naturally-ventilated houses (Hinz & Linke, 1998; Calvet et al, 2010)
Houses with negative-pressure systems use exhaust fans and blue curtains or are completely closed, and are called dark houses, which are characterized by low lighting intensity. These differences among broiler houses must be considered when evaluating the relationship between commonly used ventilation systems and the house environment
Summary
The broiler industry is one of the most technology-intensive and automated livestock activities. Houses with negative-pressure systems use exhaust fans and blue curtains (blue houses) or are completely closed, and are called dark houses, which are characterized by low lighting intensity. These differences among broiler houses must be considered when evaluating the relationship between commonly used ventilation systems and the house environment. Based on this knowledge, improvements can be made in house air quality and litter conditions, thereby reducing health problems, carcass downgrading, and improving meat quality. This study aimed at evaluating ammonia emissions in broiler houses with different ventilation systems and litter conditions (new or built-up litter). The concentration of NH3 was measured using a portable gas analyzer (BW Technologies®), which monitors atmospheric levels of up to five gases, including carbon monoxide (CO), oxygen (O2), ammonia (NH3), hydrogen sulfide (H2S), and combustible gases (LEL)
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