Poultry litter and the environment: Microbial profile of litter during successive flock rotations and after spreading on pastureland

Authors: Crippen, Tawni - Tc; SHEFFIELD, CYNTHIA - Retired ARS Employee; SINGH, BANESHWAR - Virginia Commonwealth University; Byrd Ii, James - Allen; Beier, Ross; Anderson, Robin

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2021
Publication Date: 3/13/2021
Citation: Crippen, T.L., Sheffield, C.L., Singh, B., Byrd II, J.A., Beier, R.C., Anderson, R.C. 2021. Poultry litter and the environment: Microbial profile of litter during successive flock rotations and after spreading on pastureland. Science of the Total Environment. 780. Article 146413. https://doi.org/10.1016/j.scitotenv.2021.146413.
DOI: https://doi.org/10.1016/j.scitotenv.2021.146413

Interpretive Summary: With the increasing demand for chicken meat, a thorough evaluation of the bacterial community within the grow-out houses and sites where litter is deposited is critical to animal and environmental wellbeing. However, not much is known, so our work evaluates the litter bacterial community within a house over a 2.5-year period through 11 flock rotations, a partial and a total cleanout, and the subsequent use of the litter as fertilizer on a cattle grazing pasture. Time and management practices caused changes in the litter bacterial community, leading to consistent increases and decreases in specific phyla of bacteria. The disturbance to the bacterial community by a partial cleanout seemed to be buffered by the conditions within the house, while the total cleanout showed small, but significant changes. The stockpiling of litter onto pasture affected the bacterial community within the litter over time and with environmental changes, such as weather. It showed an increase in the phyla of bacteria that commonly utilize nitrogen and decaying materials. Further, the soil from beneath where the litter had been stockpiled for 20 weeks lost microbial diversity. Knowing the populations of bacteria within the litter and in the soil where it is deposited for use as a fertilizer is necessary to maintaining a proper balance between the use of animal wastes and environmental health.

Technical Abstract: With the increasing demand for broiler meat, a thorough evaluation of the microbiome within the broiler houses and sites where litter is deposited is critical to animal and environmental wellbeing. However not much is known, so our work evaluates the litter microbiome within a house over a 2.5 year period through 11 flock rotations, a partial and a total cleanout, and the subsequent deposition of the litter onto a cattle grazing pasture as fertilizer. The effects of both time and management practices correlated with alterations of the litter microbiome. The cleanout practices and introduction of new bedding had minimal influence on the house microbiome once it was established, which generally showed a consistent increase in the proportion of Actinobacteria and a decrease in Firmicutes over the 11 flock rotations. Analysis of the bacterial profile at the genus level gave increased resolution, measuring changes during the first and second flock rotation and after the total cleanout. The disturbance of the partial cleanout seemed to be buffered by the supporting conditions within the house while the total cleanout showed a small, but significant influence. The remote deposition of litter, however, was affected by time and abiotic factors that changed the litter microbial community structure weekly. The stockpiled litter had an increase in the phyla Actinobacteria and Bacilli that commonly have microbes utilizing nitrogen and decaying materials, in comparison to native soil. Further, the soil beneath where the litter was stored for 20 weeks lost diversity, indicating a possible effect of the litter stockpiling on environmental quality at that site. How management practices affect the composition ofthe microbial community within the litter of the broiler house is of interest in terms of bird health and environmentally for future utilization of spent litter.