Changes in the taxonomic and functional structure of microbial communities during vegetable waste mixed silage fermentation

Silage fermentation, a sustainable way to use vegetable waste resources, is a complex process driven by a variety of microorganisms. We used lettuce waste as the main raw material for silage, analyzed changes in the physico-chemical characteristics and bacterial community composition of silage over a 60-day fermentation, identified differentially abundant taxa, predicted the functional profiles of bacterial communities, and determined the associated effects on the quality of silage. The biggest changes occurred in the early stage of silage fermentation. Changes in the physico-chemical characteristics included a decrease in pH and increases in ammonia nitrogen to total nitrogen ratio and lactic acid content. The numbers of lactic acid bacteria (LAB) increased and molds, yeasts and aerobic bacteria decreased. The bacterial communities and their predicted functions on day 0 were clearly different from those on day 7 to day 60. The relative abundances of phylum Firmicutes and genus Lactobacillus increased. Nitrite ammonification and nitrate ammonification were more prevalent after day 0. The differences in the predicted functions were associated with differences in pH and amino acid, protein, carbohydrate, NH3-N, ether extract and crude ash contents.

LONGITUDINAL COMPRESSING AND SHEARING PROPERTIES OF SILAGE CORN STALK IN NORTH CHINA PLAIN

During silage harvesting, silage corn stalk is compressed by a feeding device and fed into the shearing device to be sheared into qualified segments to make silage fermentation easier. To optimize the working quality of the existing silage harvester and reduce energy consumption, it’s necessary to make a comprehensive analysis of the longitudinal compressing and shearing properties of the silage corn stalks and get a reliable shearing model. According to the different structural properties of the silage corn stalks, the main factors affecting the shearing energy consumption and their levels were obtained by compressing and shearing tests on internodes and nodes in this paper. The results of three-level and three-factor experiments showed that the overall shearing energy consumption for nodes was much higher than that for internodes. Compressing the silage corn stalk to some extent before shearing at the loading direction of 0° and lower shearing speed was beneficial to saving energy during the process of shearing off the silage corn stalk. The reduced energy requirements of the silage corn stalk could be exploited advantageously to present new reference for the feeding and cutting mechanisms of silage harvester. The research results can provide a reference for silage corn harvesting.

Effects of Phenyllactic Acid, Lactic Acid Bacteria, and Their Mixture on Fermentation Characteristics and Microbial Community Composition of Timothy Silage

This study investigated the effects of phenyllactic acid (PL), lactic acid bacteria (LAB), and their mixture on fermentation characteristics and microbial community composition of timothy silage. Timothy silages were treated without (CK) or with PL [10 mg/kg fresh matter (FM) basis], LAB inoculant (IN; a mixture of Lactobacillus plantarum and L.buchneri, 105 cfu/g FM), and their mixture (PI) and stored at ambient temperature (5°C∼15°C) in a dark room for 60 days. Compared with CK, all treated silages showed lower (P < 0.05) levels of butyric acid and ammonia-N. Treatment with PL enhanced (P < 0.05) the crude protein preservation of silage by favoring the growth of L. curvatus and Saccharomyces cerevisiae and inhibition of lactic acid–assimilating yeast belonging to Issatchenkia during ensiling. In particular, treatment with PL advanced (P < 0.05) the productions of lactic acid and volatile fatty acid in IN-treated silage. Therefore, PL used as a new additive exhibited potential for improving silage fermentation when it is combined with LAB IN during ensiling.

Impact of Long-Term Storage on Alfalfa Leaf and Stem Silage Characteristics

Fractionation of alfalfa (Medicago sativa L.) into leaves and stems can reduce cutting frequency while producing a high-value feedstuff. A difficulty with fractionation is the higher moisture content at ensiling due to the inability to wilt leaves without substantial dry matter loss or financial cost. To evaluate whether the silage quality of fractionated alfalfa is competitive with conventional methods under long-term storage conditions, high-moisture leaves (250–280 g·kg−1 dry matter, DM) and stems (190–240 g·kg−1 DM) were ensiled for 21 and 350 days and compared to wilted whole-plant silage for two alfalfa developmental stages. At 21 days, leaf and whole-plant silage fermentation characteristics indicated suitable lactic acid bacterial fermentation through decreased pH, high lactic acid–to-acetic acid ratio, and a lack of clostridial fermentation. At 350 days, leaf silage fermentation and nutritional quality decreased due to sustained proteolysis, but true protein still exceeded that of whole-plant silage. High-moisture stem fractions fermented poorly; at 21 days, stage 3 stems had significant amounts of butyric acid, while stage 5 stems became clostridial at 350 days. Long-term storage of high-moisture leaf silages can produce good-quality silage despite exceeding moisture contents typically recommended for alfalfa, while wilting is required for stem silages.

Silage Fermentation: A Potential Microbial Approach for the Forage Utilization of Cyperus esculentus L. By-Product

Cyperus esculentus L. leaves (CLL) are agricultural by-products produced from Cyperus esculentus L. harvesting, and can be used as livestock feed despite their low economic value for human consumption. This study aims to develop a favorable approach to processing Cyperus esculentus L. by-product as coarse fodder. The chopped CLL was pretreated by (1) mixing with canola straw at a 4:1 ratio, or (2) wilting it for 8 h, then it ensiling with or without compounded lactic acid bacteria (LAB) additives for 60 days. Our results demonstrated that compounded LAB additives: improved CLL silage fermentation quality by increasing acetic acid and lactic acid contents and decreasing ethanol and ammonia-N contents; preserved nutrients by raising the level of crude protein and water soluble carbohydrates; modified the bacterial community by increasing the relative abundance of Lactobacillus while decreasing the relative abundance of undesirable Enterococcus; and also might improve animal health by increasing the relative concentrations of antioxidant substances (such as 7-galloylcatechin) and antibacterial compounds (such as ferulic acid). This study provides strong evidence that Cyperus esculentus L. by-product can be a potential livestock feed after being ensiled with compounded LAB additives.

Effects of Additives on Silage Fermentation Characteristic and In Vitro Digestibility of Perennial Oat at Different Maturity Stages on the Qinghai Tibetan

To effectively use local grass resources to cover the winter feed shortage on the Qinghai-Tibetan Plateau, the silage fermentation and in vitro digestibility of perennial oat (Helictotrichonvirescens Henr.) were investigated. Perennial oat was harvested at the heading/flowering stage, wilted under sunny conditions, chopped, vacuumed in small bag silos, and stored at ambient temperatures (5–15 °C) for 60 days. The silages were treated without (CK) or with local lactic acid bacteria (LAB) inoculant (IN1), commercial LAB inoculant (IN2), and sodium benzoate (BL). Control silages of perennial oat at early heading stage showed higher (p < 0.05) lactate and acetate contents and lower (p < 0.05) final pH, butyrate, and ammonia-N contents than those at the flowering stage. High levels of dry matter recovery (DMR) and crude protein (CP) were observed in IN1- and BL-treated silages, with high in vitro gas production and dry matter digestibility. Compared to CK, additives increased (p < 0.05) aerobic stability by inhibiting yeasts, aerobic bacteria, and coliform bacteria during ensiling. In particular, the local LAB inoculant increased (p < 0.05) concentrations of lactate, acetate and propionate, and decreased concentrations of butyrate and ammonia-N in silages. This study confirmed that local LAB inoculant could improve the silage quality of perennial oat, and this could be a potential winter feed for animals such as yaks on the Qinghai Tibetan Plateau.

Succession of Microbial Communities of Corn Silage Inoculated with Heterofermentative Lactic Acid Bacteria from Ensiling to Aerobic Exposure

To further explore the effects of heterofermentative lactic acid bacteria (LAB) on silage fermentation and aerobic stability, whole-plant corn at around the 1/2 milk-line stage was freshly chopped and ensiled in laboratory silos with deionized water (control), Lactobacillus buchneri (LB), or L. rhamnosus (LR). Each treatment was prepared in triplicate for 3, 14, and 60 d of fermentation, followed by 3 and 7 days of aerobic exposure. The dynamic changes in microbial community were studied by single molecule real-time (SMRT) sequencing. The results showed that the two LAB inoculants altered the microbial communities in different ways. Succession from L. plantarum to L. buchneri and L. rhamnosus was observed in LB- and LR-treated silage, respectively. Both silages improved aerobic stability (82 and 78 h vs. 44 h) by occupying the microbial niche to produce higher levels of acetic acid at terminal fermentation. Because Acetobacter fabarum dominated in the silages after aerobic exposure, beta diversity dramatically decreased. In this study, a. fabarum was reported for the first time in silage and was related to aerobic spoilage. The two heterofermentative LAB produced acetic acid and improved the aerobic stability of the corn silage by occupying the microbial niche at terminal fermentation. Inoculated L. rhamnosus had a greater pH for a longer period of time after opening and less DM loss at day 7.

The Potential Effects on Microbiota and Silage Fermentation of Alfalfa Under Salt Stress

This study investigated the fermentation quality of alfalfa grown in different salt stress regions in China. Following the production of silage from the natural fermentation of alfalfa, the interplay between the chemical composition, fermentation characteristics, and microbiome was examined to understand the influence of these factors on the fermentation quality of silage. The alfalfa was cultivated under salt stress with the following: (a) soil content of &lt;1%0 (CK); (b) 1–2%0 (LS); (c) 2–3%0 (MS); (d) 3–4%0 (HS). The pH of the silage was high (4.9–5.3), and lactic acid content was high (26.3–51.0 g/kg DM). As the salt stress increases, the NA+ of the silages was higher (2.2–5.4 g/kg DM). The bacterial alpha diversities of the alfalfa silages were distinct. There was a predominance of desirable genera including Lactococcus and Lactobacillus in silage produced from alfalfa under salt stress, and this led to better fermentation quality. The chemical composition and fermentation characteristics of the silage were closely correlated with the composition of the bacterial community. Furthermore, NA+ was found to significantly influence the microbiome of the silage. The results confirmed that salt stress has a great impact on the quality and bacterial community of fresh alfalfa and silage. The salt stress and plant ions were thus most responsible for their different fermentation modes in alfalfa silage. The results of the study indicate that exogenous epiphytic microbiota of alfalfa under salt stress could be used as a potential bioresource to improve the fermentation quality.

PSII-14 Inclusion of popcorn and crawfish shells as components in non-feedstock silage production

As the future of agricultural sciences, it is imperative that student scientists seek to investigate alternatives to help improve production by lowering costs while meeting dietary requirements, increasing output, and maintaining sustainability. Anthropogenic waste as potential feedstock, we are engaging in an innovative wave of agricultural research. While previous research in our laboratory has evaluated newspaper, waste popcorn, and crawfish shells as feedstock, their potential for ensiling represents an alternative avenue for upcycling and long-term storage. The objective of this experiment was to determine the optimum concentrations of newspaper, waste popcorn, and crawfish shells for ideal silage fermentation. This experiment was conducted as a Box-Wilson composite design with four replications. Prescribed amounts of shredded newspaper, ground crawfish shells and heads, and waster popcorn were thoroughly mixed, and water and inoculant were added to achieve 25% dry matter. Central points for popcorn were 35.5, 1.3, 35.5, and 1.3% dry matter, respectively, for grain silage, grass silage, high combination, and low combination. Central points for crawfish were 4.0, 6.4, 4.0, and 6.4% dry matter, respectively, for grain silage, grass silage, high combination, and low combination. Samples were sealed using a food-grade sealer and allowed to ferment for 35 d. A subsample was frozen for assay of pH and silage acids. The remaining sample was dried at 55°C, ground, and assayed for NDF, ADF, CP, and IVTD. Across block, there was no effect of crawfish or popcorn inclusion on NDF (P ≥ 0.09; μ = 74%), ADF (P ≥ 0.24; μ = 60%), or IVTD (P ≥ 0.12; μ = 35%). Results are interpreted to mean that these feed ingredients may be used in non-feedstock silage production, but its usefulness to livestock production is questionable.