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Ruminal Fermentation: 2nd Edition

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A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Microbial Metabolism, Physiology & Genetics".

Deadline for manuscript submissions: 31 May 2026 | Viewed by 5177

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Prof. Dr. Cláudia Braga Pereira Bento

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Department of Animal Science, Universidade Federal dos Vales do Jequitinhonha e Mucuri, Unaí, Brazil
Interests: alternative additives; antimicrobials; beef and dairy cattle; composition of ruminal microbiota; deamination; nitrogen metabolism
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Dear Colleagues,

The success of ruminant animals is associated with their ability to digest fiber-rich plant material. Although ruminants do not secrete digestive enzymes in the rumen, a number of various microorganisms, including bacteria, methanogenic archaea, anaerobic fungi, and protozoa, which live in symbiosis with the host, are capable of performing ruminal fermentation and hydrolyzing soluble and insoluble carbohydrates, proteins, and lipids from the diet.

Ruminal fermentation is the result of the balance of interactions among the different species of microorganisms present in the rumen. It is the outcome of microbiological activities responsible for converting food components (carbohydrates and nitrogen) into products used in animal metabolism, such as volatile organic acids (VOAs), microbial proteins, and B vitamins. This process also produces substances not utilized by the animal (CH₄ and CO₂), which are physiologically eliminated and represent energy losses.

The proportion and quantity of by-products resulting from the ruminal fermentation process depend on various factors, such as the type of feed, the manner in which the feed is offered, balanced diets, the use of feed additives, and physiological factors related to the ruminal environment, such as temperature, pH, and redox potential.

The aim of this Special Issue is to publish both recent innovative research results and review papers that assess ruminal fermentation both in vitro and in vivo using different strategies aimed not only at improving the health and performance of ruminants but also at playing a role in mitigating climate change by reducing ammonia production and greenhouse gas emissions, such as methane. If you would like to contribute a review paper, please contact one of the editors to discuss the topic's relevance before submitting the manuscript.

Prof. Dr. Cláudia Braga Pereira Bento
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fermentation is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

ammoniacal nitrogen
animal nutrition
antimicrobials
enteric methane
environmental impact
feed additives
feed efficiency
next-generation sequencing
rumen parameters
ruminal microbiota
ruminants

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Related Special Issue

Ruminal Fermentation in Fermentation (13 articles)

Published Papers (6 papers)

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Research

12 pages, 1231 KB

Open AccessArticle

Hydroponically Sprouted Grains: Effects on In Situ Ruminal Nutrient Degradation, Fractional Disappearance Rate, and Effective Ruminal Degradation

by Gerald K. Salas-Solis, Ana Carolina S. Vicente, Jose A. Arce-Cordero, Martha U. Siregar, Mikayla L. Johnson, James R. Vinyard, Richard R. Lobo, Efstathios Sarmikasoglou and Antonio P. Faciola

Fermentation 2026, 12(1), 55; https://doi.org/10.3390/fermentation12010055 - 18 Jan 2026

Viewed by 200

Abstract

This study aimed to evaluate in situ ruminal nutrient degradation, fractional disappearance rate, and effective ruminal degradation of hydroponically sprouted barley, wheat, and triticale. Two ruminally canulated lactating cows were used in a complete randomized block design with four treatments and nine incubation times (0, 2, 4, 8, 12, 24, 48, 72, and 240 h). Treatments were corn silage (control), and sprouted barley, triticale, and wheat. Quadruplicate samples (5 g each) were placed in Dacron bags and incubated in the rumen. Then, bags were rinsed and spun, dried (48 h × 55 °C; 3 h × 105 °C), and weighed to determine residual dry matter (DM). Data were analyzed using mixed models (MIXED, SAS 9.4) with treatment, time, and their interaction as fixed effects, and cow and replicate (cow) as random effects. Denominator degrees of freedom were adjusted using the Kenward–Roger method, and means were separated by Tukey–Kramer. Significance was declared at p ≤ 0.05 and tendencies at 0.05 < p ≤ 0.10. Sprouted triticale and wheat treatments had a greater rapidly soluble fraction for DM (p < 0.01), the greatest fractional disappearance rate for DM (p < 0.01) and neutral detergent fiber (NDF; p < 0.01), and greater effective ruminal degradability (ERD) for DM (p < 0.01) and crude protein (CP; p < 0.01). Sprouted wheat also had the greatest ERD for NDF (p < 0.01). In contrast, sprouted barley had the lowest rapidly soluble fractions for DM (p < 0.01), NDF (p < 0.01), and CP (p < 0.01), lower fractional disappearance rate for DM (p < 0.01) and NDF (p < 0.01) than sprouted triticale and wheat, and the lowest ERD for DM (p < 0.01) and CP (p < 0.01). Overall, sprouted triticale and wheat had greater in situ ruminal nutrient degradation, effective ruminal degradation, and nutrient degradation kinetics, indicating their potential for inclusion in dairy cattle diets to improve nutrient degradability. Full article

(This article belongs to the Special Issue Ruminal Fermentation: 2nd Edition)

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12 pages, 307 KB

Open AccessArticle

Evaluation of Plant Essential Oils as Natural Alternatives to Monensin in In Vitro Ruminal Fermentation

by Amelia Barbosa Lima, Kemmily Lima de Almeida, Bruna Eduarda Teixeira de Lima, Khalid Haddi, Ludmila Couto Gomes Passetti, Gustavo Leão Rosado and Cláudia Braga Pereira Bento

Fermentation 2025, 11(12), 693; https://doi.org/10.3390/fermentation11120693 - 14 Dec 2025

Viewed by 493

Abstract

Extensive growth promoter use in livestock production has raised concerns about their role in selective pressure on resistant microorganisms, driving interest in natural alternatives such as essential oils (EOs). This study aimed to evaluate the effects of tea tree, holy wood, and citronella EOs on in vitro ruminal fermentation. The study follows a completely randomized design with the following five treatments: control, monensin (5 μM), tea tree EO (50 mg/L), holy wood EO (50 mg/L), and citronella EO (50 mg/L), each conducted in triplicate. Incubations were performed at 39 °C for 48 h in the rumen fluid collected from fistulated cattle fed a 20:80 forage-to-concentrate diet. Notably, EOs exhibited no significant effects on pH, microbial protein production, total volatile fatty acids, or in vitro dry matter digestibility (p > 0.05). Tea tree and holy wood EOs enhanced deamination activity, and all treatments increased ammonia concentration compared with that in the control. Monensin treatment increased acetate concentration and reduced in vitro neutral detergent fiber digestibility; holy wood EO exhibited a similar trend. Altogether, the findings of this study suggest that EOs can selectively modulate the ruminal microbiota, influencing nitrogen metabolism and fermentation patterns without impairing rumen stability. Full article

(This article belongs to the Special Issue Ruminal Fermentation: 2nd Edition)

19 pages, 306 KB

Open AccessArticle

In Vitro and In Situ Evaluation of White Mulberry (Morus alba) Pomace and Leaf: Fermentation Kinetics, Digestibility, and Potential as Alternative Ruminant Feed Sources

by Zekeriya Safa İnanç and Huzur Derya Arik

Fermentation 2025, 11(12), 692; https://doi.org/10.3390/fermentation11120692 - 12 Dec 2025

Viewed by 539

Abstract

Mulberry (Morus alba) by-products represent underutilized feed resources with potential for ruminant nutrition. This study evaluated the rumen fermentation kinetics and rumen digestibility of dried mulberry pomace (MP) and leaf (ML) to determine optimal inclusion strategies in dairy cattle diets. Mulberry pomace (MP) and mulberry leaf (ML) were sun-dried and incorporated at 50% substitution levels into total mixed rations (TMR) with varying concentrations (30%, 35%, 40%, 45%, and 50%) of neutral detergent fiber (NDF). This created ten treatment groups: 30NP through 50NP (pomace-supplemented, where the number represents basal TMR NDF%) and 30NL through 50NL (leaf-supplemented), plus control groups containing only MP or ML and five basal TMR controls (30N through 50N). Rumen fluid was collected from two non-lactating Holstein cows fitted with ruminal cannulas. Chemical analysis revealed that ML contained 19% crude protein and 27.4% NDF, while MP contained 14.9% crude protein and 35.8% NDF. The highest gas production was observed in the 45NP (43.20 mL) and 50NL (43.50 mL) groups. Results demonstrated that MP achieved optimal fermentation when combined with 40–45% NDF TMR (maximum total volatile fatty acid (VFA): 88.86 mmol/L in 40NP at 48 h), whereas ML performed best with 45% NDF TMR (45NL: 88.03 mmol/L total VFA), indicating these as the most promising treatment combinations for ruminant feeding systems pending in vivo validation. Acetate proportions were higher in ML groups (84–96%), while propionate ratios were elevated in MP groups. Both materials maintained optimal ruminal pH (6.2–6.8). In vitro NDF digestibility was significantly higher for ML, with differences increasing from 2.97% at 2 h to 16.44% at 240 h. In situ degradation of MP was nearly complete at 48 h, while ML reached maximum degradation at 24 h. These findings indicate the potential of MP and ML as valuable alternative feed sources for ruminants, particularly in TMRs containing 40–45% NDF. Full article

(This article belongs to the Special Issue Ruminal Fermentation: 2nd Edition)

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17 pages, 456 KB

Open AccessArticle

Enhanced In Vitro System for Predicting Methane Emissions from Ruminant Feed

by Seongwon Seo and Mingyung Lee

Fermentation 2025, 11(12), 681; https://doi.org/10.3390/fermentation11120681 - 7 Dec 2025

Viewed by 600

Abstract

Mitigating enteric methane emissions through diet formulation remains a significant challenge in cattle nutrition. This study developed a system to evaluate the methane production potential of feeds, expressed as the effective ruminal methane production rate (eRMR, mL/g dry matter [DM]), using a discontinuous in vitro ruminal fermentation system using rumen fluid. Sixteen concentrate feeds and two forages were tested, with a reference diet (ryegrass straw:corn:corn gluten feed = 1:1:1) included in each batch to standardize conditions and account for associative effects among feeds. Test feeds were incubated with the reference diet in closed bottles under strictly anaerobic conditions. Methane and total gas production were measured at 2, 4, 6, and 24 h, and true dry matter digestibility was calculated after 6 and 24 h. For each batch, sample feed values were corrected and standardized using those of the reference diet. The eRMR value was calculated by integrating a differential equation with parameters incorporating ruminal digestion and passage dynamics. The test feed eRMR values ranged from 1.2 mL/g DM (soybean meal) to 56.7 mL/g DM (soybean hull), with the reference diet at 14.8 mL/g DM. Evaluation of feed eRMR using data from two in vivo studies demonstrated strong correlations between predicted diet-specific eRMR values and measured methane emissions from Hanwoo steers (r = 0.93 and 0.85). This system, incorporating rumen dynamics with a reduced sampling schedule, provides a precise and practical tool for predicting in vivo enteric methane production and optimizing diet formulations to mitigate methane emissions from cattle. Full article

(This article belongs to the Special Issue Ruminal Fermentation: 2nd Edition)

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29 pages, 5748 KB

Open AccessArticle

Metatranscriptome Analysis of Sheep Rumen Reveals Methane Production Changes Induced by Moringa oleifera as a Dietary Supplement

by Alicia Alejandra Grijalva-Hinojos, Vicente Arnau, Wladimiro Díaz, Samuel Piquer, Daniel Díaz-Plascencia, Yamicela Castillo-Castillo, Joel Domínguez-Viveros and Perla Lucia Ordoñez-Baquera

Fermentation 2025, 11(10), 568; https://doi.org/10.3390/fermentation11100568 - 1 Oct 2025

Viewed by 1652

Abstract

Global warming has become a significant public health concern, with intensive livestock farming as a major contributor. To mitigate greenhouse gas emissions, strategies such as manipulating the ruminal environment with dietary additives are essential. This study evaluated Moringa oleifera, a globally widespread tree with antioxidant, multivitamin, protein-rich, and anti-inflammatory properties, as a feed additive. Rumen fluid was collected from three Pelibuey sheep, homogenized, and subjected to an in vitro fermentation study for 48 h with three alfalfa/moringa ratio treatments: T0 Control (100:0), T1 Low (85:15), and T2 High (70:30). Total RNA was extracted, followed by high-definition sequencing of the metatranscriptome. The sequencing yielded approximately 456 million sequences. A total of 117 phyla were identified and approximately 1300 genera were mapped. Predominant phylum differed by treatment: T0, Firmicutes; T1, Proteobacteria; and T2 with Synergistetes, at least one sample per treatment. Archaea were nearly absent in T1, which explains a statistically significant decrease in methane production. In the Gene Set Enrichment Analysis (GSEA), it was observed that one of the metabolic pathways with a statistically significant difference (p-value < 0.05) was that of methane, specifically in the low moringa treatment (T1) compared to the control (T0). From the functional analysis, differentially expressed enzymes were identified, some of which are involved in the methane metabolic pathway, such as formate dehydrogenase (EC 1.17.1.9) and glycine hydroxymethyltransferase (EC 2.1.2.1), which are intermediates in methane formation. These results suggest that 15% Moringa oleifera supplementation alters ruminal microbiota, reduces archaeal activity, and suppresses methane-related pathways. These findings provide molecular evidence supporting the potential of M. oleifera as a methane mitigation strategy in ruminant nutrition. Full article

(This article belongs to the Special Issue Ruminal Fermentation: 2nd Edition)

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15 pages, 1919 KB

Open AccessArticle

Degradation of Microplastics in an In Vitro Ruminal Environment

by Sonia Tassone, Rabeb Issaoui, Valentina Balestra, Salvatore Barbera, Marta Fadda, Hatsumi Kaihara, Sara Glorio Patrucco, Stefania Pragliola, Vincenzo Venditto and Khalil Abid

Fermentation 2025, 11(8), 445; https://doi.org/10.3390/fermentation11080445 - 31 Jul 2025

Cited by 2 | Viewed by 1289

Abstract

Microplastic (MP) pollution is an emerging concern in ruminant production, as animals are exposed to MPs through air, water, and feeds. Ruminants play a key role in MP transmission to humans via animal products and contribute to MP return to agricultural soil through excreta. Identifying effective strategies to mitigate MP pollution in the ruminant sector is crucial. A promising yet understudied approach involves the potential ability of rumen microbiota to degrade MPs. This study investigated the in vitro ruminal degradation of three widely distributed MPs—low-density polyethylene (LDPE), polyethylene terephthalate (PET), and polyamide (PA)—over 24, 48, and 72 h. PET MP exhibited the highest degradation rates (24 h: 0.50 ± 0.070%; 48 h: 0.73 ± 0.057%; and 72 h: 0.96 ± 0.082%), followed by LDPE MP (24 h: 0.03 ± 0.020%; 48 h: 0.25 ± 0.053%; and 72 h: 0.56 ± 0.066%) and PA MP (24 h: 0.10 ± 0.045%; 48 h: 0.02 ± 0.015%; and 72 h: 0.14 ± 0.067%). These findings suggest that the ruminal environment could serve as a promising tool for LDPE, PET, and PA MPs degradation. Further research is needed to elucidate the mechanisms involved, potentially enhancing ruminants’ natural capacity to degrade MPs. Full article

(This article belongs to the Special Issue Ruminal Fermentation: 2nd Edition)

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