Effects of inoculation on ensiling characteristics, chemical composition and aerobic stability of regular and brown midrib millet silages

This study was conducted to determine the effects of inoculation on ensiling characteristics, chemical composition and aerobic stability of two forage millet cultivars in a 2×2 factorial experiment. Second cut regular and brown midrib forage millet were treated with a commercial inoculum containing Lactobacillus plantarum and Enterococcus faecium or left untreated. The forages were then ensiled in laboratory silos for 2, 4, 8, 16, and 45 days. The pH of treated silages was below 4.0 at day 2 post-ensiling, while untreated silages reached that pH at day 8 post-ensiling. Untreated and inoculated silages, however, had similar pH at 45 days post-ensiling with no cultivar×treatment interaction. Lactic acid concentration was higher (P<0.05) while that of acetic acid was lower (P<0.05) for inoculated than untreated silages at all ensiling times. Lactic acid bacteria were numerically higher for inoculated than untreated silages at day 0 and 2 post-ensiling. Proteolysis during ensiling was not affected by inoculation or forage millet cultivar. Inoculation reduced (P<0.05) aerobic stability of forage millet silages by an average of 40 h. Inoculation also increased (P<0.05) dry matter loss (in the laboratory silos) and yeast and mold populations in aerobically exposed millet silages by 4% and 1 colony forming unit/g, respectively. Chemical composition of the 45-day silages was affected by millet cultivar but not by inoculation. Brown midrib millet silages had lower (P<0.05) neutral detergent fibre (593 g/kg versus 620 g/kg), acid detergent fibre (332 g/kg versus 368 g/kg) and acid detergent lignin (14 g/kg versus 32 g/kg) concentrations and higher (P<0.05) in vitro dry matter disappearance (783 g/kg versus 746 g/kg) than regular millet silages. It was concluded that inoculation caused significant changes in concentrations of organic acids during ensiling which resulted in less aerobically stable forage millet silages. Most of the differences in chemical composition and in vitro disappearance were due to cultivar differences and not inoculation.