Open research questions in Ruminant Nutrition and Digestive Physiology

What the literature leaves open

• There is a need to understand the microbial basis of goat health and productivity. The current study aims to address this gap by investigating the microbial community in dairy goat feces using metagenomic analysis.

  Metagenomic analysis of fecal microbial communities in dairy goats from different farms · 2026 · DOI

• One of the challenges is the variation in the concentration of fibre and dry matter in mesquite pods due to harvesting conditions and phenological stage. Another challenge is the need to evaluate the effects of Neltuma spp. pods on in vitro ruminal fermentation kinetics and digestive health indicators in sheep.

  Effects of Neltuma spp. Pod Inclusion on In Vitro Ruminal Fermentation Kinetics, Ruminal Metabolic Activity Indicators, and Digestive Health in Sheep · 2026 · DOI

• One of the challenges is to evaluate the impact of grazing pressure on species richness and forage quality in alkali grasslands. Another challenge is to understand the effects of grazing on biodiversity and ecosystem functions in grassland ecosystems. The study also faced the challenge of collecting data in a remote area with limited access.

  What Are the Effects of Cattle Grazing on Conservation and Forage Value Across Grazing Pressure Gradients in Alkali Grasslands? · 2025 · DOI

• The economic return on extensive livestock farming is low. There is a need to evaluate the potential of pasture plant community composition as an indicator to assess the effects of intensification strategies.

  Pasture Floristic Composition as an Indicator of Soil pH Correction and Sheep Stocking Rate in Montado Ecosystem · 2025 · DOI

• The high fiber lignin content and low crude protein content of corn straw limit its use as a roughage resource. The low digestibility of corn straw is a challenge that needs to be addressed.

  Effects of Replacing Rice Straw with Corn Straw Silage Treated with Different Additives on Growth Performance, Blood Parameters, and Rumen Microorganisms of Fattening Cattle · 2025 · DOI

• The study was conducted in vitro. The study used a limited number of rumen fluid donors (two non-lactating Holstein cows). The study did not account for potential variability in rumen fluid collection and donor animal physiological status.

  In Vitro and In Situ Evaluation of White Mulberry (Morus alba) Pomace and Leaf: Fermentation Kinetics, Digestibility, and Potential as Alternative Ruminant Feed Sources · 2025 · DOI

• In vivo validation of the results is needed. Further studies on the effects of MP and ML on ruminant nutrition and health are required. Investigation of the optimal inclusion levels and ratios of MP and ML in ruminant diets.

  In Vitro and In Situ Evaluation of White Mulberry (Morus alba) Pomace and Leaf: Fermentation Kinetics, Digestibility, and Potential as Alternative Ruminant Feed Sources · 2025 · DOI

• There is a lack of understanding about the effects of alpine herbs on rumen microbiota. The study aims to fill this gap by assessing the effects of supplementing alpine herbs on rumen microbiota via in vitro fermentation.

  The Effect of Alpine Herbs on the Microbiota of In Vitro Rumen Fermentation · 2025 · DOI

• The contradiction between forage supply and demand has intensified in the Northwest Sichuan Plateau. There is a need to improve the quality of oat and common vetch silage to support the development of the local animal husbandry economy.

  Effects of Compound Lactic Acid Bacteria Additives on the Quality of Oat and Common Vetch Silage in the Northwest Sichuan Plateau · 2025 · DOI

• Limited understanding of the effects of RDS levels on rumen fermentation and microbial protein synthesis.

  Effects of Rumen-Degradable Starch Levels on In Vitro Rumen Fermentation and Microbial Protein Synthesis in Alfalfa Silage · 2025 · DOI

• The study had to account for variations in cow rumen conditions during the in sacco incubation procedure. The need to avoid overfilling the rumen during the 336 h incubations. The challenge of analyzing the complex relationships between grass composition, ruminal degradation, and cow milk production.

  Species and Harvest Time of Fresh Tropical Grasses Affect Rumen Fermentation as Determined by In Sacco and In Vitro Incubations · 2025 · DOI

• Detailed knowledge on the NDF degradation of tropical grasses is scant. There is a need for region-specific nutritional research on the NDF degradation of tropical grasses.

  Species and Harvest Time of Fresh Tropical Grasses Affect Rumen Fermentation as Determined by In Sacco and In Vitro Incubations · 2025 · DOI

• The accumulation of dihydrogen during methane inhibition can impact rumen fermentation and decrease dry matter intake. The variability in outcomes across studies due to differences in additive combinations and adaptation periods. The need to optimize microbial pathways for hydrogen utilization through targeted co-supplementation and microbial adaptation.

  Insights into the Feed Additive Inhibitor and Alternative Hydrogen Acceptor Interactions: A Future Direction for Enhanced Methanogenesis Inhibition in Ruminants · 2025 · DOI

• The need to evaluate the effectiveness of different treatments. The challenge of measuring gas production and rumen degradation characteristics.

  Rumen Degradation Characteristics of Rumen-Protected Fermented Soybean Meal Investigated Using the Nylon Bag and In Vitro Gas Production Method · 2025 · DOI

• The lack of effective treatments to protect fermented soybean meal from rumen degradation. The need to investigate the rumen degradation characteristics of rumen-protected fermented soybean meal. The importance of finding a feasible treatment solution for applying fermented soybean meal to dairy cows.

  Rumen Degradation Characteristics of Rumen-Protected Fermented Soybean Meal Investigated Using the Nylon Bag and In Vitro Gas Production Method · 2025 · DOI

• The small sample size (n = 2) limited the statistical power and generalizability of the findings. The assumption of uniform forage intake relied on previous reports, and variations in forage composition cannot be completely ruled out. The small number of biological replicates in some molecular assays reduces confidence in microbial abundance estimates.

  Changes in Ruminal Dynamics and Microbial Populations Derived from Supplementation with a Protein Concentrate for Cattle with the Inclusion of Non-Conventional Feeding Sources · 2025 · DOI

• Small sample size of 36 lambs, - Limited to male Kangal Akkaraman lambs, - Study duration of 63…

  Effects of oral administration of lavender ( Lavandula angustifolia ) essential oil on growth performance, serum biochemistry and muscle fatty acid profile in Kangal Akkaraman lambs · 2026 · DOI

• Investigate the effects of lavender oil on other breeds of lambs, - Examine the effects of different dosages of lavender oil, - Study the long-term effects of lavender oil…

  Effects of oral administration of lavender ( Lavandula angustifolia ) essential oil on growth performance, serum biochemistry and muscle fatty acid profile in Kangal Akkaraman lambs · 2026 · DOI

• Investigating the effects of mesquite pods on live animals, - Studying the variations in harvesting conditions and phenological stage of mesquite pods, - Examining the potential of mesquite pods as a strategic source of nutrients for livestock…

  Effects of Neltuma spp. Pod Inclusion on In Vitro Ruminal Fermentation Kinetics, Ruminal Metabolic Activity Indicators, and Digestive Health in Sheep · 2026 · DOI

• The study was conducted in vitro, - Further in vivo validation trials are recommended to confirm these in vitro results, - The levels of 50% WCS inclusion exceed the recommended limit of fat in ruminant diets…

  Whole Cottonseed as an Alternative to Mitigate In Vitro Methane Emissions on Low-Quality Forage-Based Diets · 2025 · DOI

• In vivo validation trials to confirm the in vitro results, - Evaluation of long-term impacts on animal performance and CH4…

  Whole Cottonseed as an Alternative to Mitigate In Vitro Methane Emissions on Low-Quality Forage-Based Diets · 2025 · DOI

• Small sample size of 18 cattle, - Limited to Simmental cattle, - No comparison to other types of silage or feed…

  Effects of Replacing Rice Straw with Corn Straw Silage Treated with Different Additives on Growth Performance, Blood Parameters, and Rumen Microorganisms of Fattening Cattle · 2025 · DOI

• Investigate the effects of other types of alpine herbs on the rumen microbiota, - Examine the impact of alpine herbs on the rumen microbiota in vivo, - Study the effects of alpine herbs on the quality and composition of milk and dairy…

  The Effect of Alpine Herbs on the Microbiota of In Vitro Rumen Fermentation · 2025 · DOI

• Further in vivo trials on a larger scale are recommended, - Measurement of volatile fatty acid (VFA) profiles to allow direct correlations between microbial shifts and fermentation end-products, - Investigation of the impact of variations in forage composition…

  Changes in Ruminal Dynamics and Microbial Populations Derived from Supplementation with a Protein Concentrate for Cattle with the Inclusion of Non-Conventional Feeding Sources · 2025 · DOI

• Variation in outcomes across studies due to differences in additive combinations, dosages, and adaptation periods, - Limited number of laboratory experiments and animal studies, - Differences in inclusion rates of the feed additives, ration formulation, duration of adaptation to the ingredients, and animal…

  Insights into the Feed Additive Inhibitor and Alternative Hydrogen Acceptor Interactions: A Future Direction for Enhanced Methanogenesis Inhibition in Ruminants · 2025 · DOI

Most-cited papers in Ruminant Nutrition and Digestive Physiology

• Metabolic Hydrogen Flows in Rumen Fermentation: Principles and Possibilities of Interventions · Frontiers in Microbiology · 2020 · 467 citations
• Multi-omics reveals that the rumen microbiome and its metabolome together with the host metabolome contribute to individualized dairy cow performance · Microbiome · 2020 · 409 citations
• Red seaweed (Asparagopsis taxiformis) supplementation reduces enteric methane by over 80 percent in beef steers · PLoS ONE · 2021 · 391 citations
• Mitigating the carbon footprint and improving productivity of ruminant livestock agriculture using a red seaweed · Journal of Cleaner Production · 2020 · 374 citations
• Nutrient Profiles of Vegetarian and Nonvegetarian Dietary Patterns · Journal of the Academy of Nutrition and Dietetics · 2013 · 305 citations
• An integrated gene catalog and over 10,000 metagenome-assembled genomes from the gastrointestinal microbiome of ruminants · Microbiome · 2021 · 287 citations
• Feed additives as a strategic approach to reduce enteric methane production in cattle: modes of action, effectiveness and safety · Animal Production Science · 2021 · 209 citations
• Benefits and risks of including the bromoform containing seaweed Asparagopsis in feed for the reduction of methane production from ruminants · Algal Research · 2022 · 203 citations
• Integrated meta-omics reveals new ruminal microbial features associated with feed efficiency in dairy cattle · Microbiome · 2022 · 166 citations
• Strategies Used to Reduce Methane Emissions from Ruminants: Controversies and Issues · Agriculture · 2023 · 128 citations

Most recent work

• Phytochemicals in Ruminant Diets: Mechanistic Insights, Product Quality Enhancement, and Pathways to Sustainable Milk and Meat Production—Invited Review · Animals · 2026
• Tannins in ruminant feeding: effects of tannin type and dosage on rumen fermentation, production performance, health, and sustainability · Research in Veterinary Science · 2026
• Invited review: Perspectives on nitrogen in dairy cattle nutrition · Journal of Dairy Science · 2026
• Fermentation of wheat bran by edible fungal mycelium: A pathway to high-quality protein for sustainable ruminant feed · Animal Feed Science and Technology · 2026
• In Vitro Assessment of Essential Oils for Their Methane Mitigation Potential and Impact on Rumen Fermentation in Cattle · Animals · 2026
• Nano/microencapsulation of feed additives for ruminal microbiome modulation and enteric methane mitigation in ruminants: a critical review · Frontiers in Veterinary Science · 2026
• Integrative analysis of rumen microbiota and host multi-organ interactions underlying feed conversion efficiency in Hu sheep · Journal of Animal Science and Biotechnology/Journal of animal science and biotechnology · 2026
• Associations of growth rates during the first 2 months of life with feeding behavior, development, and first-lactation performance in Holstein heifers · Journal of Dairy Science · 2026
• F3-metabolomics: Integrating feed, fluid, and food metabolomics in dairy production · Animal Feed Science and Technology · 2026
• Comparative analysis of rumen metagenomes with dietary supplementation of 3-nitrooxypropanol revealed divergent modes of action in hydrogen metabolism and reductant pathways between beef and dairy cattle · Microbiome · 2026

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