Silage fermentation and chemical composition of elephant grass inoculated with rumen strains of Streptococcus bovis

The objective of this study was to evaluate the effects of Streptococcus bovis JB1 and HC5 on the fermentation and chemical composition of elephant grass ensiled in laboratory silos. A complete randomized design was used with four treatments: elephant grass silage, elephant grass silage inoculated with 106 CFU/g S. bovis JB1 strains; elephant grass silage inoculated with 106 CFU/g S. bovis HC5 strains; elephant grass silage inoculated with 106 CFU/g Enterococcus faecium, and six replications. The highest number of enterobacteria, fungi and yeast occurred in the control and elephant grass silages inoculated with E. faecium (P<0.05). The silage inoculated with Streptococcus bovis JB1 and HC5 presented the lowest enterobacteria, fungi and yeast populations and the highest number of lactic acid bacteria, 10.03 and 9.97 log CFU/g, respectively. The pH and ammoniac nitrogen values were low (P<0.05) in the treatments with Streptococcus bovis JB1 and HC5, respectively. The observed pH values were 3.83 and 3.96 in the treatments with S. bovis JB1 and HC5, respectively, lower than the observed value of 4.01 in the control treatment. The silages inoculated with S. bovis JB1 and HC5 presented the highest (P<0.05) lactic acid values, 67.8 and 66.2 g/kg DM, respectively, and the lowest acetic, butyric and propionic acid values. Inoculation with Streptococcus bovis resulted in a higher (P<0.05) crude protein content in the silages, highest dry matter and crude protein recovery and lowest losses through gases and effluents. Treatments with S. bovis JB1 and HC5 presented values of 93.94 and 92.45 for dry matter recovery. There were no statistical differences (P>0.05) for the other chemical characteristics. Both S. bovis JB1 and HC5 improved the fermentation profile, reduced nutrient losses and increased the nutritional value of the elephant grass silage.