Changes in microbial and nutrient composition associated with rumen content compost incubation

Physico-chemical and microbiological investigations were carried out on rumen content material composted for nine months, fresh vermicasts (obtained after passing the same compost through the guts of a mixture of three species of earthworms: Eisenia fetida, Lumbricus rubellus and Perionyx excavates) and microbially enhanced extracts derived from rumen compost, vermicast and vermicast leachate incubated for up to 48 h. Compared to composted rumen contents, vermicast was only improved in terms of microbial biomass C, while vermicast leached extract was significantly higher in NH4+-N,PO4--P, humic acid, bacterial counts and total microbial activity compared to rumen compost extract. Although no difference between treatments was observed in genetic diversity as indicated by DGGE analysis, community level functional diversity of vermicast leached extract (Biolog™) was higher than that of composted rumen contents, vermicast and rumen compost extract indicating an enhancement of microbial activity rather than diversity due to liquid incubation.