Stratification of bacterial concentrations, from upper to lower, in broiler litter

Abstract

There have been numerous research studies concerning the different types of bacteria in broiler litter. However, very little is known about the spatial distribution of bacteria from the top to the bottom of the litter bed. Two experiments were conducted, one of a single flock in a pen trial, and the second on a commercial broiler farm for 8 consecutive flocks. Core litter samples were taken and 3 fractions of litter were removed from each core for bacterial analysis: the upper 5.08 cm of litter, the exact middle of the litter, and the lower section of litter directly on top of the dirt pad, being sure to include some dirt pad. Core litter samples were taken specifically at 7 d before placement then again at 1, 7, 14, 21, 35, and 49 d of age in experiment 1, and 14 and 35 d of age in experiment 2. Core samples were removed from 6 pens in the first experiment. In experiment 2, core litter samples were taken near the evaporative cooling cells, the environmental control room or middle of the house, and near the exhaust fans. Litter fractions were analyzed for Staphylococcus spp., Clostridium perfringens, Escherichia coli, Salmonella spp., total aerobes, and total anaerobes. A decrease was observed from the top to middle and from middle to bottom fractions of litter for all bacteria. From upper to lower, all bacteria concentrations were reduced by at least 99%. Therefore, the concentration of bacterial populations within broiler litter could shift dramatically within only a few inches of litter and the lower fraction of litter holds relatively less bacteria than the upper or middle fractions.