In-shed heaping of broiler litter to inactivate poultry pathogens before reuse

Abstract

Reusing poultry litter for multiple batches of broiler chickens risks transfer of pathogens between batches. On two commercial farms we investigated the effects of various litter heaping treatments for 9-10 days between batches of chickens (heaping or windrowing, with or without turning at day 3-4, or litter turning only) on temperature profiles and loss of infectivity of litter for key viral pathogens and coccidia. Treatments within farm were replicated in two sheds. Temperature was monitored continuously at depths of 0, 25, 50 and 75-100 cm. On days 0, 3-4, 6-7, and 9-10, representative litter from these depths was collected, pooled and infectivity tested using a published chick bioassay measuring seroconversion or oocyst production in chicks exposed to litter in isolators. Temperature varied markedly with depth and time. Mean below surface maxima of 65-68 °C (Farm 1) and 55-63 °C (Farm 2) were reached more rapidly at 25 cm (3-4 days) than 50-100cm (7-10 days) with the highest peak temperatures recorded at 50cm. Temperatures were higher in heaps than windrows and turning did not increase temperature. Coccidial infectivity was undetectable by day 3. Fowl adenovirus infectivity was mostly undetectable by days 6-7 while chicken infectious anaemia virus and infectious bursal disease virus infectivity were undetectable by days 6-10. Marek's disease virus showed reduction in infectivity with significant infectivity remaining at days 9-10. This work confirmed litter transmission of several viral pathogens and showed that heaping of litter between batches will markedly reduce the infective load of most pathogens evaluated, and potentially eliminate some.