Towards Improved Inactivation and Monitoring of Viral Pathogens in Reused Broiler Litter

Re-use of litter by broiler chickens can reduce the cost and environmental impact of production but uptake of the practice is limited largely by the risk of pathogen carryover between batches. On a recent project funded by the Australian Poultry CRC (Project 06-15) our research team developed an effective chick bioassay to measure viral infectivity in litter (1). We also conducted field experiments investigating the effects of various litter heaping treatments on decay of viral infectivity over 9-10 days (2) and associated temperature, pH, moisture and litter chemistry measurements (3,4). One objective of this work was to link the temperatures and other changes achieved during litter treatments to the rate of pathogen inactivation as determined by bioassay of litter infectivity. Ideally such information would be generated for the complete range of viral pathogens, but a problem with the approach taken was that sometimes there was a limited range of pathogens on a given farm in question. One solution would be to experimentally infect chickens and thus litter with a wide range of pathogens, but it is difficult and expensive to do this on scale which would generate sufficient litter for composting studies that would mimic the field situation. Another problem with wider application of methodology to measure viral pathogen load in litter is the comparatively high cost of the chick bioassay.