Effects of wilting and molasses addition on fermentation and bacterial community in guinea grass silage

Abstract

Aims: Acetic acid is considered an important preservative in tropical grass ensiling. The objective of the current experiments was to follow the ensiling fermentation of low dry matter (DM) tropical grass as a model to study changes in bacterial communities during acetic acid fermentation. Methods and Results: Direct‐cut and wilted guinea grass silage was prepared with and without molasses. A high acetic acid level was observed during the fermentation of direct‐cut silage, and long storage increased the butyric acid and ethanol content if molasses was not added. The lactic acid production in wilted silage was greater than the acetic acid production, but prolonged ensiling decreased the lactic to acetic acid ratio regardless of molasses addition. Adding molasses enhanced the lactic acid content in both direct‐cut and wilted silage. The bacterial community, identified by denaturing gradient gel electrophoresis, was affected by wilting and molasses addition. Bands for Pantoea sp. and Morganella sp. became faint when acetic acid fermentation was suppressed, and those for Pediococcus pentosaceus and Lactococcus garvieae were detected when lactic acid fermentation was enhanced by wilting and molasses addition. Lactobacillus plantarum and Lactococcus lactis were found throughout the ensiling process in all silage types. Conclusion: Distinct changes occurred in the bacterial community in guinea grass silage because of wilting and molasses addition. These changes could explain how lactic acid fermentation was enhanced but could not help determine which bacteria were associated with enhanced acetic acid fermentation. Significance and Impact of the Study: The study reveals the effects of wilting and molasses during ensiling of low DM tropical grasses and the associated bacteria.

Adding distiller's grains and molasses on fermentation quality of rice straw silages

“…In the present study, the addition of molasses alone enhanced lactic acid fermentation, declining pH. The rapid and vigorous LA accumulation could depress the proteolysis and activity of clostridia or other undesirable bacteria (NISHINO et al, 2012). This is consistent with the lower AA, PA, BA and ammonia N concentration observed in the silages with molasses in the study.…”

The effect of cultivar, wilting and storage period on fermentation and the clostridial community of alfalfa silage

“…In this study, higher BC value in direct-cut A4 alfalfa could partly contribute to the higher pH in direct-cut A4 silage than in the other three cultivars. Nishino et al (2012) suggested that Lactobacillus plantarum was involved in the increase in acetic acid content with prolonged ensiling, because L. plantarum can metabolise lactic acid to acetic acid under sugardeficient conditions. The same metabolic process could have occurred in the case of direct-cut silage because of prolonged ensiling.…”

“…Ensilage under farm conditions is not a completely controlled process, because various factors can influence the ensiling process, such as plant species, method of ensiling, climate and DM content (Monteiro et al 1998;Namihira et al 2010;Nishino et al 2012). For the preparation of well-preserved silage, rapid development of the lactic acid fermentation is necessary to reduce the pH and inhibit the growth of inefficient and spoilage microorganisms such as clostridia, enterobacteria, yeast and moulds, which can cause degradation of plant material and/or production of undesirable metabolites (McDonald et al 1991).…”

“…One frequently used method is denaturing gradient gel electrophoresis (DGGE) analysis, which can demonstrate the dynamics of each microbial constituent in microcosms (Namihira et al 2010). DGGE analysis has been shown to help understand how LAB and non-LAB species function in the ensiling process for various crop species (Nishino et al 2012). However, sufficient data are not yet available on the clostridial community involved in alfalfa silage.…”

The use of crude glycerin as an alternative to reduce fermentation losses and enhance the nutritional value of Piatã grass silage

“…The challenge would be to make ensiling of grass feasible by increasing the growth rates of lactic acid bacteria, dropping silage pH, and enhancing fermentation (Keady and Kiely, 1998;McDonald and Henderson, 1962;Nishino et al, 2012;Chen et al, 2016). If possible, this would configure alternative usage of a potentially pollutant byproduct from biofuel production.…”