Quantifying poultry litter conditions and relationships with odour emissions

Abstract

Litter conditions are managed during poultry rearing to provide a comfortable environment for the chickens and reduce the potential of odour impact on surrounding communities. This study aimed to identify and quantify the properties of poultry litter in Australian meat chicken sheds that influence odour formation and emissions. Litter conditions were evaluated in terms of litter moisture content, pH, water activity and oxygen concentration. Litter samples collected from meat chicken sheds during the eight week grow-out period showed that litter conditions varied spatially, within the litter profile, during the grow-out and between grow-outs. Litter conditions were measured at discrete positions across the litter and within the profile to describe the full range, rather than measuring average conditions.Water affects many of the chemical, physical and microbial properties of litter and yet research revealed a lack of knowledge in terms of the water balance within meat chicken sheds and litter properties, especially moisture content, water holding capacity and water activity. An equation combining theoretical and empirical inputs was developed to estimate the water addition to litter during a grow-out. This was combined with experimental measurements of water holding capacity and evaporation rate to identify periods of the grow-out when litter conditions were at risk of deteriorating. Addition of manure during a grow-out was found to increase the water holding capacity of litter and reduced water activity, which is a measure of the availability of water within litter that affects friability and microbial growth.Odorant emission rates were measured for different litter conditions in meat chicken sheds and during a laboratory based study where meat chickens were reared in a pen with a litter floor. Emission rates of volatile organic compounds and sulfur compounds (VOC and VSC) from the litter surface were measured using flux hoods and analysed by a combination of TD-GC-MS, TD-GC-SCD and PTR-TofMS methods. Emission rates of some odorants were found to be significantly affected by litter conditions (when litter was characterised as ‘wet’ or ‘dry’) and the length of the grow-out. Odour activity values indicated which individual odorants made the biggest contribution to wet and dry litter odours.