Variations in bacterial communities in laboratory-scale and big bale silos assessed by fermentation products, colony counts and denaturing gradient gel electrophoresis profiles

Abstract

Aims: To assess the variation in bacterial communities in laboratory-scale and big bale silos.

Methods and results: Wilted Italian ryegrass (628 g dry matter kg(-1)) was ensiled in vacuum-packed plastic pouches and big bales. Silos were opened after 3 months, and the fermentation products, colony counts and denaturing gradient gel electrophoresis (DGGE) profiles were determined. Eight samples were collected separately from a big bale, while one representative sample was taken from a plastic pouch. Significant variation was found between big bales in dry matter, ethanol, lactic acid, acetic acid and ammonia-N contents. No differences were shown between plastic pouches and big bales, except that more ethanol was produced in the former air-tight silos. Plastic pouches could resemble a specific silo and outer sampling sites of big bales based on fermentation products and DGGE profiles respectively.

Conclusions: Considerable variation in fermentation products may exist between big bale silos. Plastic pouches can serve as a model of big bale silos, although they do not provide information on the heterogeneity within and between bales.

Significance and impact of the study: Assessment of bacterial communities associated with ensiling can differ according to the criteria of fermentation products, colony counts and DGGE profiles.