Poultry litter is often highlighted to be the major source of odour associated with emissions from broiler production. Mitigation strategies for the management of odours from poultry litter require great understanding of the litter properties, bird numbers and shed operation and management that can affect the emission of odours. In this study, fresh and used litter from two mechanically ventilated broiler sheds was analysed for odour emissions to identify and characterise the changes in odours for a full broiler growth cycle in winter and summer seasons. Dynamic olfactometry analysis revealed an increase in the odour concentration pattern from week 0 to week 5 in wet winter litter samples and from 0 to week 6 in dry and wet summer litter samples before declining in the following week. The greatest odour emission was encountered for the caked wet broiler litter. No significant impacts on odour concentration were identified for season, bedding types and the number of birds during the investigation. The deposition of manure, other biological fluids and solids substantially transformed the water content and pH of the bedding litters, which subsequently altered the physical, chemical and microbial properties of the bedding material and most likely contributed to the formation and emission of odours from the bedding material. The results suggest that odour concentration (and therefore emission rate) can be minimised with proper management of the litter moisture content and maintenance of the drinker systems. [ABSTRACT FROM AUTHOR]