Inactivation of viruses and coccidia in broiler litter following heaping or windrowing at the end of the batch

Abstract

Two on-farm experiments were conducted to determine the effectiveness of windrowing or heaping end of batch broiler litter for up to 10 days on inactivation of pathogenic viruses and coccidia. In Expt 1 (Sydney) litter treatments were heaping, heaping with turning at day 4 or windrowing. In Experiment 2 (Brisbane) litter treatments were no heaping (simply turning litter 'in situ'), windrowing, or windrowing with turning at day 4. There were two replicates of both treatments in each experiment. On 4 occasions (days 0, 3, 6, 9 in Expt. 1 and days 0, 4, 7 and 10 in Expt. 2) representative litter samples from each treatment were subjected to a chick bioassay to measure litter infectivity for a number of key viral diseases as determined by seroconversion at 35 days post exposure to the litter. Coccidial oocyst counts in faeces were also conducted in Expt 1. Heaping or windrowing litter led to marked reduction in the proportion of bioassay chicks positive for chicken anaemia virus (CAV) and fowl adenovirus (FAV) but there was no clear effect on infectious bursal disease virus (IBDV) for which initial litter infectivity was low. Turning provided no additional benefit overall and heaping appeared to provide a greater level of inactivation than windrowing. Litter infectivity was very low or absent for pathogens such as infectious bronchitis virus (IBV) and Marek's Disease virus (MDV) so inferences could not be made about these. Serology for additional viral pathogens is ongoing. Coccidial oocysts were completely inactivated in the treated litter by day 6. These preliminary data suggest that heaping or windrowing of litter is beneficial in reducing viral pathogen load in litter, that most (but not all) inactivation is completed by days 6-7, that large heaps inactivate more effectively than windrows, and that turning of heaps or windrows does not provide an additional benefit.