Influence of microbial additive on microbial populations, ensiling characteristics, and spoilage loss of delayed sealing silage of Napier grass

Improvements in fermentation and nutritive quality of elephant grass [Cenchrus purpureus (Schumach.) Morrone] silages: a review

Elephant grass [Pennisetum purpureum Schumach. syn. Cenchrus purpureus (Schumach.) Morrone], also known as Napier grass and King grass, includes varieties Taiwán, Gigante, Merkerón, Maralfalfa, and others. The grass achieves high biomass production in tropical-subtropical, temperate, and arid areas. The high-water concentration of elephant grass suggests that ensiling could offer an alternative way to preserve the nutritional quality of the grass during storage, however, some considerations should be addressed because of the particularities of the grass. Ensiling elephant grass may produce adequate fermentation but could suffer effluent losses and subsequent losses of nutrients due to leaching. To improve fermentation and nutrient characteristics of elephant grass silages, several studies were conducted with the inclusion of additives. Lactic acid bacteria inocula have reduced pH and increased crude protein content of elephant grass silage, but aerobic stability of silages could be affected by the bacterial inoculation. There is limited information, however, on the potential of different silage inoculants to reduce growth of spoilage microorganisms during the aerobic phase of silage prepared with elephant grass. Exogenous fibrolytic enzymes also may improve elephant grass silage quality by enhancing microbial fiber-degradation with subsequent increase in lactic acid and its associated pH reduction. Another study approach to improve fermentation and nutritional quality of elephant grass silages involved the addition of different feeds at ensiling, including conventional feeds such corn, wheat, rice bran, and molasses or alternative feeds such as different dehydrated by-products obtained from the food industries of juice and jelly. In the manuscript, the presented scientific information shows the great potential of the different manipulations to improve the quality of elephant grass silages and with possible enhance of the economic profit and sustainability of livestock farming in the tropical areas.

Microbial network and fermentation modulation of Napier grass and sugarcane top silage in southern Africa

IMPORTANCE

Feed shortage in the tropics is a major constraint to the production of livestock products such as milk and meat. In order to effectively utilize of local feed resources, the selected lactic acid bacteria (LAB) strain was used to prepare Napier grass and sugarcane top silage. The results showed that the two silages inoculated with LAB formed a co-occurrence microbial network dominated by Lactiplantibacillus during the fermentation process, regulated the microbial community structure and metabolic pathways, and improved the silage fermentation quality. This is of great significance for alleviating feed shortage and promoting sustainable production of livestock.

Silage preparation and sustainable livestock production of natural woody plant

As the global population increases and the economy grows rapidly, the demand for livestock products such as meat, egg and milk continue to increase. The shortage of feed in livestock production is a worldwide problem restricting the development of the animal industry. Natural woody plants are widely distributed and have a huge biomass yield. The fresh leaves and branches of some woody plants are rich in nutrients such as proteins, amino acids, vitamins and minerals and can be used to produce storage feed such as silage for livestock. Therefore, the development and utilization of natural woody plants for clean fermented feed is important for the sustainable production of livestock product. This paper presents a comprehensive review of the research progress, current status and development prospects of forageable natural woody plant feed resources. The nutritional composition and uses of natural woody plants, the main factors affecting the fermentation of woody plant silage and the interaction mechanism between microbial co-occurrence network and secondary metabolite are reviewed. Various preparation technologies for clean fermentation of woody plant silage were summarized comprehensively, which provided a sustainable production mode for improving the production efficiency of livestock and producing high-quality livestock product. Therefore, woody plants play an increasingly important role as a potential natural feed resource in alleviating feed shortage and promoting sustainable development of livestock product.

Effect of isolated lactic acid bacteria on the quality and bacterial diversity of native grass silage

Objective

The objective of this study was to isolate lactic acid bacteria (LAB) from native grasses and naturally fermented silages, determine their identity, and assess their effects on silage quality and bacterial communities of the native grasses of three steppe types fermented for 60 days.

Methods

Among the 58 isolated LAB strains, Limosilactobacillus fermentum (BL1) and Latilactobacillus graminis (BL5) were identified using 16S rRNA sequences. Both strains showed normal growth at 15- 45°C temperature, 3-6.5% NaCl concentration, and pH 4-9. Two isolated LAB strains (labeled L1 and L5) and two commercial additives (Lactiplantibacillus plantarum and Lentilactobacillus buchneri; designated as LP and LB, respectively) were added individually to native grasses of three steppe types (meadow steppe, MS; typical steppe, TS; desert steppe, DS), and measured after 60 d of fermentation. The fresh material (FM) of different steppe types was treated with LAB (1 × 10⁵ colony forming units/g fresh weight) or distilled water (control treatment [CK]).

Results

Compared with CK, the LAB treatment showed favorable effects on all three steppe types, i.e., reduced pH and increased water-soluble carbohydrate content, by modulating the microbiota. The lowest pH was found in the L5 treatment of three steppe types, at the same time, the markedly (p < 0.05) elevated acetic acid (AA) concentration was detected in the L1 and LB treatment. The composition of bacterial community in native grass silage shifted from Pantoea agglomerans and Rosenbergiella nectarea to Lentilactobacillus buchneri at the species level. The abundance of Lentilactobacillus buchneri and Lactiplantibacillus plantarum increased significantly in L1, L5, LP, and LB treatments, respectively, compared with CK (p < 0.05).

Conclusion

In summary, the addition of LAB led to the shifted of microbiota and modified the quality of silage, and L. fermentum and L. graminis improved the performance of native grass silage.

Characterization of Lactic Acid Bacteria Isolated from Banana and Its Application in Silage Fermentation of Defective Banana

To effectively utilize banana by-products, we prepared silage with defective bananas using screened lactic acid bacteria (LAB), sucrose, and tannase as additives. Eleven strains of LAB were isolated from the fruits and flowers of defective bananas, all of which were Gram-positive and catalase-negative bacteria that produced lactic acid from glucose. Among these LAB, homofermentative strain CG1 was selected as the most suitable silage additive due to its high lactic acid production and good growth in a low pH environment. Based on its physiological and biochemical properties and 16S rRNA gene sequence analysis, strain CG1 was identified as Lactiplantibacillus plantarum. Defective bananas contain 74.8−76.3% moisture, 7.2−8.2% crude protein, 5.9−6.5% ether extract, and 25.3−27.8% neutral detergent fibre on a dry matter basis. After 45 d of fermentation, the silage of deficient bananas treated with LAB or sucrose alone improved fermentation quality, with significantly (p < 0.05) lower pH and higher lactic acid contents than the control. The combination of LAB and sucrose had a synergistic effect on the fermentation quality of silage. The tannase-treated silage significantly (p < 0.05) decreased the tannin content, while the combination of tannase and LAB in silage not only decreased (p < 0.05) the tannin content, but also improved the fermentation quality. The study confirmed that defective bananas are rich in nutrients, can prepare good quality silage, and have good potential as a feed source for livestock.

Effects of Lactic Acid Bacteria and Molasses Additives on Dynamic Fermentation Quality and Microbial Community of Native Grass Silage

Ensiling native grass is an effective method to protect the nutritional quality of forage and alleviate feed shortages in the cold winter of the Inner Mongolian Plateau. To improve the usability of native grass resources as feed in China, the effects of lactic acid bacteria and molasses additions on the microbial population, fermentation quality, and nutritional quality of native grass during silage were investigated. Treatments were a control treatment with no additive (CK), lactic acid bacteria (L), molasses (M), and lactic acid bacteria in combination with molasses (L+M), all of which were stored at ambient temperature (17-28°C) for 7, 14, 30, and 60 days. The results showed that all additives improved nutritional value and fermentation quality with low pH and ammonia nitrogen (NH3-N) and high crude protein (CP) and water soluble carbohydrate (WSC) than control silage over the ensiling period. Compared with L or M silage, the L+M silage combination improved fermentability, as evidenced by higher LA content and a faster pH drop during the first 7 days of ensiling. With prolonged ensiling time, the combined addition of L and M could increase the count of desirable Lactobacillus, decrease microbial diversity, and inhibit the growth of undesirable microorganism, such as Clostridia, Escherichia, and Enterobacter abundance compared with silage treated with CK, L. or M. Application of L together with M could further improve the silage quality of native grass by altering bacterial community structure. In summary, the addition of lactic acid bacteria and molasses increased the relative abundance of Lactobacillus of native grass silage and improved fermentation quality.

Effects of applying cellulase and starch on the fermentation characteristics and microbial communities of Napier grass (Pennisetum purpureum Schum.) silage

This study investigated the effects of applying cellulase and starch on the fermentation characteristics and microbial communities of Napier grass silage after ensiling for 30 d. Three groups were studied: No additives (control); added cellulase (Group 1); and added cellulase and starch (Group 2). The results showed that the addition of cellulase and starch decreased the crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and pH significantly (p < 0.05) and increased water-soluble carbohydrate (WSC) content (p < 0.05). The addition of additives in two treated groups exerted a positive effect on the lactic acid (LA) content, lactic acid bacteria (LAB) population, and lactic acid / acetic acid (LA/AA) ratio, even the changes were not significant (p > 0.05). Calculation of Flieg’s scores indicated that cellulase application increased silage quality to some extent, while the application of cellulase and starch together significantly improved fermentation (p < 0.05). Compared with the control, both additive groups showed increased microbial diversity after ensiling with an abundance of favorable bacteria including Firmicutes and Weissella, and the bacteria including Proteobacteria, Bacteroidetes, Acinetobacter increased as well. For alpha diversity analysis, the combined application of cellulase and starch in Group 2 gave significant increases in all indices (p < 0.05). The study demonstrated that the application of cellulase and starch can increase the quality of Napier grass preserved as silage.

Effects of Delayed Harvest and Additives on Fermentation Quality and Bacterial Community of Corn Stalk Silage

This study aimed to investigate the effects of delayed harvest and additives on the fermentation quality and bacterial community of corn stalk silage in South China. The corn stalks after ear harvest at the 0 day (D0), 7 days (D7), and 15 days (D15) were used to produce small-bale silages. The silages at each harvest time were treated without (control, CK) or with Lactobacillus plantarum (LP) and sodium benzoate (BF). The results showed that delayed harvest increased pH and acetic acid content and reduced lactic acid content in corn stalk silage (p < 0.05). Compared with CK, the additives decreased the contents of butyric acid and ammonia nitrogen (NH3-N; p < 0.05). The silage treated with LP increased the content of lactic acid and decreased pH (p < 0.05); the silage treated with BF decreased counts of coliform bacteria and yeasts and increased residual water soluble carbohydrates (WSC) content (p < 0.05). Single Molecule, Real-Time sequencing (SMRT) revealed that the abundance of L. plantarum increased, while the abundance of Lactobacillus brevis and Lactobacillus ginsenosidimutans decreased with the delayed harvest. Additives influenced the bacterial community structure of corn stalk silage, revealed by enhanced bacterial diversity on D0 and reduced on D7 (p < 0.05). Our research indicated that delayed harvest could exert a positive effect on acetic acid production, and additives could inhibit the butyric acid fermentation and protein degradation of corn stalk silage by shifting bacterial community composition.

Influences of size reduction, hydration, and thermal-assisted hydration pretreatment to increase the biogas production from Napier grass and Napier silage

Pretreatment of lignocellulose materials prior to biogas production is required to minimize biomass recalcitrance and increase biomass digestibility. In this study, the effects of particle size reduction, hydration, and thermal-assisted hydration on Napier grass and silage for methane production were evaluated. Compared to the 4.75-mm particle size Napier grass and silage, 0.425-mm Napier grass and silage showed 72% and 46% increases in methane yield, respectively, whereas hydration pretreatment using hydrogenic effluent increased the methane yields from Napier grass and silage by 23% and 56%, respectively. Superior effects were observed when Napier grass and silage were pretreated with thermal-assisted hydration using hydrogenic effluent for 60 and 15 min, respectively, resulting in methane yields of 385 and 331 mL CH₄/g substrate_added. The results indicate that size reduction accompanied by thermal-assisted hydration using hydrogenic effluent as a hydration medium significantly improved the biodegradability of Napier grass and silage.