Gamma‐ray irradiation and microbiota transplantation to separate the effects of chemical and microbial diurnal variations on the fermentation characteristics and bacterial community of Napier grass silage

Abstract

BACKGROUND To investigate the contributions of chemical and microbial diurnal variations in fermentation characteristics and bacterial community of Napier grass silage, gamma‐ray irradiated Napier grass harvested at 07.00 h (AM), 12.00 h (M) and 17.00 h (PM) was inoculated with the microbiota derived from Napier grass harvested at AM, M and PM in a 3 (irradiated forage: AMG, MG and PMG) × 3 (microbiota: AMM, MM and PMM) design and then ensiled for 14 and 60 days. RESULTS Napier grass harvested at various times had different chemical compositions and epiphytic microbiota prior to ensiling. For silages inoculated with the same microbiota, the pH values, residual water soluble carbohydrates and dry matter contents increased, and lactic acid, acetic acid, propionic acid, butyric acid, ethanol and volatile fatty acids contents decreased in PMG and MG silages compared to AMG silages. MM and PMM inoculum promoted lactic acid fermentation as indicated by higher lactic acid contents and lactic/acetic acid ratios in MM and PMM‐inculated silages compared to those in AMM‐inoculated silages after 60 days of ensiling. During ensiling, epiphytic microbiota affected the Chao1 index, operational taxonomic units (OTUs) number and Shannon index, as well as the abundances, of more than half of the top 10 abundant genera, whereas chemical composition did not affect any of the bacterial diversity and richness indices and only showed significant impacts on the abundances of two genera. CONCLUSION The results indicated that chemical diurnal variation exerted an influence mainly on the extent of fermentation, whereas microbial diurnal variation affected more the bacterial community and fermentation types during Napier grass ensiling. © 2022 Society of Chemical Industry.

Epiphytic microbiota source stimulates the fermentation profile and bacterial community of alfalfa-corn mixed silage

“…Ensiling is a well-established and low-cost method for preserving fresh forage with high biological potential ( Pakarinen et al, 2011 ). In the natural ensiling process, the epiphytic bacteria converting water soluble carbohydrates (WSC) in forage under anaerobic conditions, thereby producing organic acids (mainly lactic acid), which creates an acid environment to inhibits undesirable microorganisms ( Dong et al, 2022 ), allowing the nutritional properties of forage to be preserved for a long time, this acidification inhibits the growth of spoilage microorganisms ( Xu et al, 2017 ), thus allowing for long-term preservation of forage nutritional characteristics. Silage has become increasingly important worldwide due to its resilience against climatic variations.…”

“…It is important to explore the dynamic changes occurring in the epiphytic microbiota source during ensiling ( Xu et al, 2017 ). The composition of epiphytic microbiota source on fresh forage surface is highly heterogenous ( Dong et al, 2022 ), being primarily composed of LAB, yeasts, and molds, and it varies considerably among different types of forage. The contribution of the epiphytic microbiota source to silage fermentation quality also varies.…”

Diurnal Variation of Epiphytic Microbiota: an Unignorable Factor Affecting the Anaerobic Fermentation Characteristics of Sorghum-Sudangrass Hybrid Silage

“…However, possible effects brought by these diurnal changes on silage fermentation are rarely explored, likely because those effects are difficult to differentiate from the effects brought by chemical changes. Recently, silage researchers started to use microbiota transplantation to clarify the role of exogenous epiphytic microbiota in silage quality ( 2 , 6 ). They demonstrated that exogenous microbiota can reconstruct a similar function in the recipient plant.…”

Addition of Organic Acids and Lactobacillus acidophilus to the Leguminous Forage Chamaecrista rotundifolia Improved the Quality and Decreased Harmful Bacteria of the Silage

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