Altered microbial community structure contributes to foam production in swine manure storage facilities
Extensive spontaneous foam production in deep-pit swine manure storages has become a serious concern in the US pork industry. Foam production is undesirable from a management standpoint, and leads to accumulation of flammable gases produced by microbial communities in the manure storages. This phenomenon has resulted in explosions and flash fires in Midwestern US swine facilities, creating a critical need to identify and address the causes of foam production. Our working hypothesis was that foam production was related to a disturbance or shift in the composition or activity of microbial assemblages in manure storage facilities, and that swine industry management factors could be identified as ecological drivers that alter the microbial ecology of these managed systems. Changes in feed formulation were specifically investigated as potential drivers of shifts in manure microbial communities.
Vertically stratified manure samples were collected monthly from 103 barns in Iowa, including sites that were foaming and non-foaming sites, and sites that transitioned between these states. Bacterial and archaeal microbial communities were characterized by DNA sequencing and fingerprinting approaches. Correspondence analysis was used to relate patterns in microbial community composition to management factors and manure composition.
Across many barns, time points, and two producer groups, microbial communities in foaming sites were significantly different in composition (Group A: ANOSIM R=0.36, p<0.001; Group B: ANOSIM R=0.465, p<0.001). Richness of microbial communities was significantly reduced in sites experiencing foaming (p<0.05), and the proportion of several bacterial taxa were increased in foaming sites: Ruminococcus,Turcibacter, Bacteroidales. These shifts in composition were also correlated with increased methane production in foaming sites, and altered methanogen community structure. Feed ingredients, particularly total digestible fiber and starch, were correlated with differences in microbial community composition, as well as manure chemical and physical characteristics (pH, solids and manure temperature).
These results suggest that feed formulation can shift the composition of the microbial community, resulting in increased methane production that contributes to foaming in manure storage facilities.