Intercomparison of headspace sampling methods coupled to TD-GC-MS/O to characterise key odorants from broiler chicken litter

Abstract

Since limited studies exist on the emissions of odours from tunnel ventilated broiler sheds under the Australian climate, this research study aims to determine the key odorants in the headspace of litter at ambient temperature across the poultry production cycle in two seasons (winter and summer) using headspace sampling coupled to TD-GC-MS/O analysis. Dynamic dilution olfactometry analysis was performed on litter odour samples producing odour concentrations ranging from 1421 to 115372 OU/m3 and from 604 to 104379 OU/m3 for winter and summer litters with greatest emission encountered from winter caked wet litter that sustained high amount of water and low pH. Analysis of litter odorant composition employing headspace sampling coupled to TD-GC-MS/O provided a greater understanding of the fate of odorants in the litter during bird growth cycle. The study also showed that characterise odorous volatiles can be correlated with dynamic dilution olfactometry responses. The results revealed that the odorous contributions were ketones, volatile fatty acids, sulfur and nitrogen compounds that were highly offensive substances, which impose significant effect on the odour annoyance from the emissions compared to other chemical functionalities. The assessment of activated carbon, silica gel and zeolite as a potential odour reducing strategy was directly applied to litters. The studies exhibited mixed trends in chemical and sensory responses and selectivity in reducing the volatilisation of odorants attributed to the efficacy of the additive itself, heterogeneous condition of litter particles in contact with the reduction materials and the exposed surface area. Based on the chemical and sensory responses, activated carbon and silica gel exhibited noticeable interactions on excessively wet litter with trial litters appeared remarkably drier and friable than the control and zeolite sets. However, complete elimination of odour or decrease in odour hedonic tone was unachievable mainly due to emission of ammonia from trial sets. Therefore, it is evident that no one product is capable of reducing or removing all volatiles presents in the emission of odours from poultry shed litter. Appropriate litter management within the shed conditions would still be the best method to avoid or reduce the generation of odours at source point before considering application of odour control products.