Effect of Heap Size, Shape, Covering, and Turning on Litter Pasteurization During In-Shed Partial Composting

Abstract

Limited availability and high cost of chicken bedding materials are driving some broiler producers to reuse litter for multiple chicken batches in Australia. Pasteurization of litter between batches by heaping or windrowing for up to ten d can greatly assist in reducing pathogen carryover to the next batch of chickens. We have previously reported litter temperatures of 50-70 °C inside broiler litter heaps between three and ten d after heaping, depending on depth within the heap (1). The surface of the heaps remained relatively cool (20-40 °C) and turning at d three significantly increased temperatures after turning. Larger heaps are generally hotter than long windrows (2), which are easier to make. There are reports in the USA that both increased moisture level (3) and covering (4) of litter can elevate heap temperatures significantly. It has been shown recently that using a tarpaulin to cover the heap can elevate heap temperatures between 5 and 10 °C, particularly closer to the surface (5). Pasteurization of litter has been shown to eliminate, or greatly reduce, the infective load of viral pathogens and coccidia in the litter (3). However, current industry demand is for short batch turnaround times of six d or less with a strong preference to avoid turning litter during pasteurisation if possible. Thus there is demand for quick and uniform pasteurisation of litter without turning. The objective of the current study was to investigate the effects of covering, heap size and shape (heap vs windrow) on intra-heap temperatures with a view to reducing the time to maximum temperature, increasing the maximum temperature achieved, slowing the decline in temperature after the peak, and achieving greater uniformity of temperatures in the heap particularly near the surface.