Abstract
To investigate the effects of lactic acid bacterial (LAB) inoculants and vacuuming on the fermentation quality and bacterial community, alfalfas were ensiled with or without a commercial LAB YX or Lactobacillus plantarum strain ZZUA493 for 10, 30, 60, and 90 days while undergoing either vacuum (V) or nonvacuum (NV) treatment. At 90 days, analysis of the microbial community by high-throughput sequencing was performed, and contents of aflatoxin B1 and deoxynivalenol (DON) mycotoxins in alfalfa silage were determined. In all inoculated alfalfa silage, irrespective of V or NV treatment, lactic acid (LA) content increased, pH (p < 0.05), and ammonia nitrogen (p < 0.05) content decreased, and no butyric acid was detected. Lactobacillus or Pediococcus became the dominant genus, and the abundance of Garciella decreased in alfalfa silage with the addition of either inoculant. The LAB inoculants YX and ZZUA493 helped reduce the mycotoxin content in alfalfa silage. The abundance of Garciella in the control and DON content in all alfalfa silage groups were higher (p < 0.05) in NV than V. In summary, LAB inoculants and vacuuming had a positive influence on alfalfa silage quality, and LAB inoculants were effective in reducing mycotoxins in silage alfalfa.
Highlights
Alfalfa is a perennial herbaceous plant cultivated widely in humid and rainy southern China, characterized by high crude protein, nutritional value, and digestibility [1]
This study aimed to explore the effects of inoculation with or without lactic acid bacteria (LAB) inoculants with V and NV treatment on the bacterial community, fermentation quality and mycotoxins of alfalfa silage
This study confirmed that inoculation of alfalfa silage with YX and 493 improved fermentation quality under V or NV treatment
Summary
Alfalfa is a perennial herbaceous plant cultivated widely in humid and rainy southern China, characterized by high crude protein, nutritional value, and digestibility [1]. Alfalfa is often difficult to ensile because of its high buffering capacity and low water-soluble carbohydrate (WSC) content [4], hindering successful fermentation. Adding lactic acid bacteria (LAB) inoculant has become an effective measure to enhance the fermentation quality of alfalfa silage. Silage fermentation occurs under anaerobic conditions by forming an acidic environment by epiphytic LAB [5]. These can convert WSC into organic acids, mainly lactic acid (LA), and promote the reduction in pH, effectively preventing putrefaction of the alfalfa silage and inhibiting the growth of undesirable microorganisms [6,7]. Some research has focused on enhancing alfalfa fermentation indicators by LAB additives, such as reduction of ammonia nitrogen (NH3 -N) and pH and the increase in LA content [8,9]
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