Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2008
Publication Date: 7/16/2008
Citation: Rothrock Jr, M.J., Cook, K.L., Warren, J.G., Sistani, K.R. 2008. The effect of alum addition on microbial communities in poultry litter. Poultry Science. 87(8) 1493-1503
Interpretive Summary: Alum is a common poultry litter amendment used to reduce ammonia emissions from poultry houses. While its effectiveness has been widely studied on the physical and chemical levels, very little research has concerned the effect of alum addition on the microbial communities in the poultry litter. In this study, we observed how alum addition affects a variety of microbial groups in poultry litter, including general bacteria and fungi, specific bacterial groups known to dominate poultry litter, and also at pathogenic bacteria such as E. coli, Salmonella, and Campylobacter. To track these communities, we employed a variety of molecular microbiological methods (denaturing gradient gel electrophoresis, community cloning and quantitative real-time PCR). We found that alum addition to poultry litter significant reduces the most dominant group of bacteria in the litter (low %GC gram positives) as well as pathogenic bacteria. It also resulted in a large fungal bloom, which was not observed in the non-alum treated litter. These results indicate that more attention needs to be paid to the fungal communities in alum-treated litter, especially when considering the organic nitrogen value of the litter as a fertilizer, as well as potential ammonia emissions from the poultry house.
Technical Abstract: Alum (Al2(SO4)3 • 14 H2O) is a common poultry litter amendment used to decrease water soluble phosphorus and/or reduce ammonia volatilization. While the physiochemical effects of alum addition has been well researched, little attention has been given to the poultry litter microbial communities. The goal of this study was to use molecular biological methods (denaturing gradient gel electrophoresis (DGGE), community cloning, and quantitative real-time PCR (QRT-PCR)) to characterize general, group specific and pathogenic microbial communities in alum (10% w/w) and non-alum treated litter. According to QRT-PCR analyses, alum addition to the poultry litter resulted in significant reductions in both Campylobacter jejnui and E. coli concentrations by the end of the first month of the experiment (3 log and 2 log, respectively). Salmonella spp. were below detection (< 5 x 103 cell g-1 litter) for the entire experiment. DGGE analyses revealed significant reductions in the Clostridium/Eubacterium and Low %GC Gram Positive groups in the alum treated litters by the end of the first month, with no bands detectable for either group after 8 weeks of incubation. Conversely, minimal effects of alum addition were observed in the Actinomycetes community. The most significant shift in the microbial community (based on DGGE analyses) occurred in the fungal population, with a large increase in diversity and abundance within one month of alum addition (1 dominant band on day 0 to 9 dominant bands at 4 weeks). Specifically, the incidence of Aspergillus spp. increased from 0% to 50% of the sequences in fungal clone libraries (n = 80) over the entire course of the experiment. This suggests that the addition of alum to poultry litter potentially shifts the microbial populations from dominated by bacteria to one that is dominated by fungi. The ramifications of this shift in dominance are still unknown, and future work will be aimed at characterizing these fungi and elucidating their role in the acidified litter environment.