Abstract
The objective of this study was to investigate the mechanism of Lactobacillus plantarum (L. plantarum) involved in improving fermentation quality of naturally ensiled alfalfa under poor conditions. High-moisture wilted alfalfa was ensiled without inoculants (CK) or with inoculation of two L. plantarum additives (LPI and LPII). The pH and fermentation products of silage were determined after 30 and 90 days of ensiling. Additionally, the bacterial community compositions were analyzed. The L. plantarum inoculants significantly promoted lactic acid accumulation, and Lactobacillus abundance for both periods. At 90 days, silage in CK exhibited a high pH, a loss in dry matter, and a high concentration of ammoniacal nitrogen. The inoculations of L. plantarum significantly inhibited the growth of Clostridia, and reduced ammoniacal nitrogen concentration in silage (P < 0.05). Thus, inoculation with L. plantarum improved the fermentation quality of alfalfa silage and inhibited the growth of spoilage microorganisms, and further delayed spoilage of alfalfa silage under adverse ensiling conditions.
Highlights
Ensiling is an anaerobic microbial-based fermentation process, dominated by lactic acid bacteria (LAB), which produce the lactic acid (LA) required for pH decline and inhibition of harmful microorganisms
It can be hard to ensile owing to its high buffering capacity (BC) and lack of water soluble carbohydrates (WSCs) (Nkosi et al, 2016), especially when the moisture concentration exceeds 70%, resulting in clostridial fermentation (Coblentz and Muck, 2012)
The L. plantarum inoculants effectively accelerated the LA fermentation and acetic acid (AA) accumulation, resulting in a lower pH compared with the CK group (P < 0.001) at 30 days; and the enhanced LA accumulation was significantly greater in the LPII group (P < 0.001)
Summary
Ensiling is an anaerobic microbial-based fermentation process, dominated by lactic acid bacteria (LAB), which produce the lactic acid (LA) required for pH decline and inhibition of harmful microorganisms. It has long been a common method for forage preservation (Eikmeyer et al, 2013). High precipitation in some areas can make it difficult to wilt the Abbreviations: AA, acetic acid; BA, butyric acid; BC, buffering capacity; DM, dry matter; FW, fresh weight; LA, lactic acid; LAB, lactic acid bacteria; LDA, linear discriminant analysis; NH3-N, ammoniacal nitrogen; PA, propionic acid; WSC, water soluble carbohydrate
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