Effects of seaweed extracts on in vitro rumen fermentation characteristics, methane production, and microbial abundance

Potential use of seaweed as a dietary supplement to mitigate enteric methane emission in ruminants

Seaweeds or marine algae exhibit diverse morphologies, sizes, colors, and chemical compositions, encompassing various species, including red, green, and brown seaweeds. Several seaweeds have received increased research attention and application in animal feeding investigations, particularly in ruminant livestock, due to their higher yield and convenient harvestability at present. Recent endeavors encompassing both in vitro and in vivo experiments have indicated that many seaweeds, particularly red seaweed (Asparagopsis taxiformis and Asparagopsis armata), contain plant secondary compounds, such as halogenated compounds and phlorotannins, with the potential to reduce enteric ruminal methane (CH4) emissions by up to 99 % when integrated into ruminant diets. This review provides an encompassing exploration of the existing body of knowledge concerning seaweeds and their impact on rumen fermentation, the toxicity of ruminal microbes, the health of animals, animal performance, and enteric ruminal CH4 emissions in both in vitro and in vivo settings among ruminants. By attaining a deeper comprehension of the implications of seaweed supplementation on rumen fermentation, animal productivity, and ruminal CH4 emissions, we could lay the groundwork for devising innovative strategies. These strategies aim to simultaneously achieve environmental benefits, reduce greenhouse gas emissions, enhance animal efficiency, and develop aquaculture and seaweed production systems, ensuring a high-quality and consistent supply chain. Nevertheless, future research is essential to elucidate the extent of the effect and gain insight into the mode of action.

Temporal dynamics of volatile fatty acids profile, methane production, and prokaryotic community in an in vitro rumen fermentation system fed with maize silage

Anaerobic in vitro fermentation is widely used to simulate rumen kinetics and study the microbiome and metabolite profiling in a controlled lab environment. However, a better understanding of the interplay between the temporal dynamics of fermentation kinetics, metabolic profiles, and microbial composition in in vitro rumen fermentation batch systems is required. To fill that knowledge gap, we conducted three in vitro rumen fermentations with maize silage as the substrate, monitoring total gas production (TGP), dry matter degradability (dDM), and methane (CH4) concentration at 6, 12, 24, 36, and 48 h in each fermentation. At each time point, we collected rumen fluid samples for microbiome analysis and volatile fatty acid (VFA) analysis. Amplicon sequencing of 16S rRNA genes (V4 region) was used to profile the prokaryotic community structure in the rumen during the fermentation process. As the fermentation time increased, dDM, TGP, VFA concentrations, CH4 concentration, and yield (mL CH4 per g DM at standard temperature and pressure (STP)) significantly increased. For the dependent variables, CH4 concentration and yield, as well as the independent variables TGP and dDM, polynomial equations were fitted. These equations explained over 85% of the data variability (R2 > 0.85) and suggest that TGP and dDM can be used as predictors to estimate CH4 production in rumen fermentation systems. Microbiome analysis revealed a dominance of Bacteroidota, Cyanobacteria, Desulfobacterota, Euryarchaeota, Fibrobacterota, Firmicutes, Patescibacteria, Proteobacteria, Spirochaetota, and Verrucomicrobiota. Significant temporal variations in Bacteroidota, Campylobacterota, Firmicutes, Proteobacteria, and Spirochaetota were detected. Estimates of alpha diversity based on species richness and the Shannon index showed no variation between fermentation time points. This study demonstrated that the in vitro fermentation characteristics of a given feed type (e.g., maize silage) can be predicted from a few parameters (CH4 concentration and yield, tVFA, acetic acid, and propionic acid) without running the actual in vitro trial if the rumen fluid is collected from similar donor cows. Although the dynamics of the rumen prokaryotes changed remarkably over time and in accordance with the fermentation kinetics, more time points between 0 and 24 h are required to provide more details about the microbial temporal dynamics at the onset of the fermentation.

Effects of guanidinoacetic acid on in vitro rumen fermentation and microflora structure and predicted gene function

The fermentation substrate was supplemented with 0% guanidinoacetic acid (GAA) (control group, CON), 0.2% GAA (GAA02), 0.4% GAA (GAA04), 0.6% GAA (GAA06) and 0.8% GAA (GAA08) for 48 h of in vitro fermentation. Gas production was recorded at 2, 4, 6, 8, 12, 24, 36, and 48 h of fermentation. The gas was collected, and the proportions (%, v/v) of H2, CH4 and CO2 were determined. The rumen fermentation parameters, including pH, ammonia nitrogen (NH3-N), microbial protein (MCP) and volatile fatty acids (VFAs), were also determined. Furthermore, the bacterial community structure was analyzed through 16S rRNA high-throughput sequencing. The gene functions were predicted using PICRUSt1 according to the Kyoto Encyclopedia of Genes and Genomes (KEGG). The results showed that with the increase in GAA supplementation levels, the MCP and the concentration of rumen propionate were significantly increased, while the concentration of isovalerate was significantly decreased (p < 0.05). The results of microbial diversity and composition showed that the Shannon index was significantly decreased by supplementation with GAA at different levels (p < 0.05), but the relative abundance of norank_f_F082 and Papillibacter in the GAA06 group was significantly increased (p < 0.05). Especially in group GAA08, the relative abundances of Bacteroidota, Prevotella and Prevotellaceae_UCG-001 were significantly increased (p < 0.05). The results of gene function prediction showed that the relative abundances of the functions of flagellar assembly, bacterial chemotaxis, plant-pathogen interaction, mismatch repair and nucleotide excision repair were significantly decreased (p < 0.05), but the relative abundances of bile secretion and protein digestion and absorption were significantly increased (p < 0.05). In conclusion, supplementation with 0.8% GAA enhanced in vitro rumen fermentation parameters, increased the relative abundance of Prevotella and Prevotellaceae_UCG-001 in the rumen, and increased the metabolic pathways of bile secretion and protein digestion and absorption.

Improving the nutritional values of yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae) larvae as an animal feed ingredient: a review

Yellow mealworm larvae (YML; Tenebrio molitor) are considered as a valuable insect species for animal feed due to their high nutritional values and ability to grow under different substrates and rearing conditions. Advances in the understanding of entomophagy and animal nutrition over the past decades have propelled research areas toward testing multiple aspects of YML to exploit them better as animal feed sources. This review aims to summarize various approaches that could be exploited to maximize the nutritional values of YML as an animal feed ingredient. In addition, YML has the potential to be used as an antimicrobial or bioactive agent to improve animal health and immune function in production animals. The dynamics of the nutritional profile of YML can be influenced by multiple factors and should be taken into account when attempting to optimize the nutrient contents of YML as an animal feed ingredient. Specifically, the use of novel land-based and aquatic feeding resources, probiotics, and the exploitation of larval gut microbiomes as novel strategies can assist to maximize the nutritional potential of YML. Selection of relevant feed supplies, optimization of ambient conditions, the introduction of novel genetic selection procedures, and implementation of effective post-harvest processing may be required in the future to commercialize mealworm production. Furthermore, the use of appropriate agricultural practices and technological improvements within the mealworm production sector should be aimed at achieving both economic and environmental sustainability. The issues highlighted in this review could pave the way for future approaches to improve the nutritional value of YML.

Anti-methanogenic potential of seaweeds and seaweed-derived compounds in ruminant feed: current perspectives, risks and future prospects

With methane emissions from ruminant agriculture contributing 17% of total methane emissions worldwide, there is increasing urgency to develop strategies to reduce greenhouse gas emissions in this sector. One of the proposed strategies is ruminant feed intervention studies focused on the inclusion of anti-methanogenic compounds which are those capable of interacting with the rumen microbiome, reducing the capacity of ruminal microorganisms to produce methane. Recently, seaweeds have been investigated for their ability to reduce methane in ruminants in vitro and in vivo, with the greatest methane abatement reported when using the red seaweed Asparagopsis taxiformis (attributed to the bromoform content of this species). From the literature analysis in this study, levels of up to 99% reduction in ruminant methane emissions have been reported from inclusion of this seaweed in animal feed, although further in vivo and microbiome studies are required to confirm these results as other reports showed no effect on methane emission resulting from the inclusion of seaweed to basal feed. This review explores the current state of research aiming to integrate seaweeds as anti-methanogenic feed additives, as well as examining the specific bioactive compounds within seaweeds that are likely to be related to these effects. The effects of the inclusion of seaweeds on the ruminal microbiome are also reviewed, as well as the future challenges when considering the large-scale inclusion of seaweeds into ruminant diets as anti-methanogenic agents.

Chemical composition and in vitro rumen fermentation characteristics of various tropical seaweeds

Objective

This research aimed to evaluate potential tropical seaweed from Indonesia as an ingredient or supplement feed for ruminants based on chemical composition and in vitro rumen fermentation parameters.

Materials and Methods

The seven natural tropical seaweeds (three green and four red species) were collected from Ndrini and Sepanjang Beach, Gunungkidul, Yogyakarta, Indonesia. The experimental design on secondary metabolite profiles used a completely randomized design, and the in vitro gas production test used a randomized complete block design with seven seaweed species variances and four replications (blocks) based on rumen fluid collection time. The data obtained was analyzed using analysis of variance (ANOVA), and Duncan's Multiple Range Test was used to test the variation in the analysis.

Results

The seven tropical seaweed species have potential as mineral sources for ruminants, except for macromineral (P and S) and micromineral (Cu). The red tropical seaweed has potential as a protein source (Gelidium spinosum (S.G.Gmelin) P.C. Silva, Hypnea pannosa, and Acanthopora muscoides (L.) Bory), and the green seaweed (Chaetomorpha linum (O.F. Mull.) Kutz and Cladopora sp.) has potential as a crude fiber (CF) source for ruminants. As indicated by secondary metabolites and gas production in vitro, the green species (C. linum (O.F. Mull.) Kutz and Enteromorpha compressa) and red species (A. muscoides (L.) Bory and Gelidium amansii (J.V. Lamouroux) J.V. Lamouroux) could be degraded in the rumen and had quite high phenolic compounds.

Conclusion

The seven tropical seaweed species have the potential to be an ingredient or supplement feed for ruminants, and there were four species that have the potential to reduce methane emissions.

Effect of Pelagic Sargassum on In Vitro Dry Matter and Organic Matter Degradation, Gas Production, and Protozoa Population

This study determined the effect of pelagic Sargassum on in vitro dry matter and organic matter degradation, total gas production (TGP), and protozoa population. The treatments were different levels of Sargassum inclusion on a basal substrate (Stargrass hay; Cynodon nlemfuensis) as follows: T0 (control treatment based on Stargrass hay), T10 (90% Stargrass hay + 10% Sargassum), T20 (80% Stargrass hay + 20% Sargassum), and T30 (70% Stargrass hay + 30% Sargassum). Ruminal fermentation kinetics and protozoa population were determined during 72 h of in vitro incubations. Compared to control, dry matter degradability at 48 and 72 h and organic matter degradability at 24 and 48 h were higher in Sargassum treatments. TGP was lower with T20 at 48 h. The total population of protozoa and the concentration of Entodinium spp. were lower at T20 at 48 h and T30 at 72 h. Cl, S, Ca, K, and Zn (103, 5.97, 88.73, 285.70 g/kg, and 15,900 mg/kg) were high in Sargassum, reaching twice or even nine times higher than the contents in Stargrass (11.37, 1.60, 43.53, 87.73 g/kg, and 866.67 mg/kg). Overall, up to 30% pelagic Sargassum could be included in hay-based substrates from tropical grasses without negative effects on in vitro dry matter and organic matter degradability.

Oral administration of Pinus koraiensis cone essential oil reduces rumen methane emission by altering the rumen microbial composition and functions in Korean native goat (Capra hircus coreanae)

This study aimed to investigate Pinus koraiensis cone essential oil (PEO) as a methane (CH₄) inhibitor and determine its impact on the taxonomic and functional characteristics of the rumen microbiota in goats. A total of 10 growing Korean native goats (Capra hircus coreanae, 29.9 ± 1.58 kg, male) were assigned to different dietary treatments: control (CON; basal diet without additive) and PEO (basal diet +1 g/d of PEO) by a 2 × 2 crossover design. Methane measurements were conducted every 4 consecutive days for 17-20 days using a laser CH₄ detector. Samples of rumen fluid and feces were collected during each experimental period to evaluate the biological effects and dry matter (DM) digestibility after PEO oral administration. The rumen microbiota was analyzed via 16S rRNA gene amplicon sequencing. The PEO oral administration resulted in reduced CH₄ emission (eructation CH₄/body weight^0.75, p = 0.079) without affecting DM intake; however, it lowered the total volatile fatty acids (p = 0.041), molar proportion of propionate (p = 0.075), and ammonia nitrogen (p = 0.087) in the rumen. Blood metabolites (i.e., albumin, alanine transaminase/serum glutamic pyruvate transaminase, creatinine, and triglyceride) were significantly affected (p < 0.05) by PEO oral administration. The absolute fungal abundance (p = 0.009) was reduced by PEO oral administration, whereas ciliate protozoa, total bacteria, and methanogen abundance were not affected. The composition of rumen prokaryotic microbiota was altered by PEO oral administration with lower evenness (p = 0.054) observed for the PEO group than the CON group. Moreover, PICRUSt2 analysis revealed that the metabolic pathways of prokaryotic bacteria, such as pyruvate metabolism, were enriched in the PEO group. We also identified the Rikenellaceae RC9 gut group as the taxa potentially contributing to the enriched KEGG modules for histidine biosynthesis and pyruvate oxidation in the rumen of the PEO group using the FishTaco analysis. The entire co-occurrence networks showed that more nodes and edges were detected in the PEO group. Overall, these findings provide an understanding of how PEO oral administration affects CH₄ emission and rumen prokaryotic microbiota composition and function. This study may help develop potential manipulation strategies to find new essential oils to mitigate enteric CH₄ emissions from ruminants.

Red seaweed extracts reduce methane production by altering rumen fermentation and microbial composition in vitro

A series of in vitro batch culture incubations were carried out to investigate changes in rumen fermentation characteristics, methane (CH4) production, and microbial composition in response to supplementation with five different red seaweed species (Amphiroa anceps, AANC; Asparagopsis taxiformis, ATAX; Chondracanthus tenellus, CTEN; Grateloupia elliptica, GELL; and Gracilaria parvispora, GPAR). Prior to the incubations, the total flavonoid and polyphenol content of the red seaweed extracts was quantified. The incubated substrate consisted of timothy hay and corn grain [60:40 dry matter (DM) basis]. Treatments were substrate mixtures without seaweed extract (CON) or substrate mixtures supplemented with 0.25 mg/mL of red seaweed extract. Samples were incubated for 6, 12, 24, 36, and 48 h. Each sample was incubated in triplicates in three separate runs. In vitro DM degradability, fermentation parameters (i.e., pH, volatile fatty acids, and ammonia nitrogen), total gas production, and CH4 production were analyzed for all time points. Microbial composition was analyzed using 16S rRNA amplicon sequencing after 24 h of incubation. The highest CH4 reduction (mL/g DM, mL/g digested DM, and % of total gas production) was observed in ATAX (51.3, 50.1, and 51.5%, respectively, compared to CON; P &lt; 0.001) after 12 h of incubation. The other red seaweed extracts reduced the CH4 production (mL/g DM; P &lt; 0.001) in the range of 4.6–35.0% compared to CON after 24 h of incubation. After 24 h of incubation, supplementation with red seaweed extracts tended to increase the molar proportion of propionate (P = 0.057) and decreased the acetate to propionate ratio (P = 0.033) compared to the CON. Abundances of the genus Methanobrevibacter and total methanogens were reduced (P = 0.050 and P = 0.016) by red seaweed extract supplementation. The linear discriminant analysis effect size (P &lt; 0.05, LDA ≥ 2.0) showed that UG Succinivibrionaceae, Anaeroplasma, and UG Ruminococcaceae, which are associated with higher propionate production, starch degradation, and amylase activity were relatively more abundant in red seaweed extracts than in the CON. Our results suggest that supplementation with red seaweed extracts altered the microbiota, leading to the acceleration of propionate production and reduction in CH4 production.

Polyphenols for Livestock Feed: Sustainable Perspectives for Animal Husbandry?

There is growing interest in specialized metabolites for fortification strategies in feed and/or as an antioxidant, anti-inflammatory and antimicrobial alternative for the containment of disorders/pathologies that can also badly impact human nutrition. In this context, the improvement of the diet of ruminant species with polyphenols and the influence of these compounds on animal performance, biohydrogenation processes, methanogenesis, and quality and quantity of milk have been extensively investigated through in vitro and in vivo studies. Often conflicting results emerge from a review of the literature of recent years. However, the data suggest pursuing a deepening of the role of phenols and polyphenols in ruminant feeding, paying greater attention to the chemistry of the single compound or to that of the mixture of compounds more commonly used for investigative purposes.

Evaluation of Different Brown Seaweeds as Feed and Feed Additives Regarding Rumen Fermentation and Methane Mitigation

This study investigated the impacts of different brown seaweed species—Ascophyllum nodosum, Sargassum fulvellum, Ecklonia maxima, Lessonia flavicans, Lessonia nigrescens, and Laminaria japonica—on rumen fermentation and methane (CH4) mitigation. The current in vitro batch culture study for 24 h at 39 °C evaluated these species in two experimental designs: as feed additive and as feed. The control group for both experimental designs was composed of 500 mg of basal diet (50% grass hay/50% concentrate). For the feed additives experimental design, each seaweed species was evaluated when it was added at 20% of the basal diet, while as a feed, the inclusion level of each species was 20% to partially replace the concentrate in the basal diet as follows (50% hay/30% concentrate/20% seaweed). Chemical analyses showed that the seaweeds were characterized by a high fiber content and high amounts of minerals such as calcium, potassium, and phosphorus, while the protein content ranged within 7 and 13%. When they were applied as feed additives, they increased the production of volatile fatty acids, with L. japonica being the most effective; however, they failed to suppress CH4 production. In contrast, their inclusion as a feed in the basal diet led to a significant reduction (p < 0.05) in CH4, especially for E. maxima and L. japonica, by up to 18 and 21%, respectively, but this was associated with general inhibition of the rumen fermentation. Therefore, the tested seaweeds could be used as a source of minerals and as a feed additive to improve rumen fermentation, but without anti-methanogenic potential. Meanwhile, their inclusion as feed at 20% could reduce CH4 production with an adverse effect on fermentation. Thus, further trials are needed to identify the appropriate inclusion level to achieve effective CH4 reduction without any detrimental effects on rumen fermentation.

In vitro and in vivo Studies of Soybean Peptides on Milk Production, Rumen Fermentation, Ruminal Bacterial Community, and Blood Parameters in Lactating Dairy Cows

Soybean peptides (SPs), a feed additive derived from soybean, exhibit nutritional function and biological activity in monogastric animals, but limited studies have been conducted in dairy cows. Our experiments were conducted to evaluate the effects of SPs on the nutrient degradability of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) in vitro and milk production, rumen fermentation and bacterial community, and blood parameters of dairy cows. For in vitro experiment, ruminal fluids were collected from three ruminal cannulated Holstein dairy cows. A total of three levels of SPs (0, 0.38, and 1.92 g/kg DM of SPs) were added to the total mixed ration (TMR). Nutrient degradability and fermentation fluid pH were determined at 24 and 48 h using 3.0 g samples of the substrate. Gas production after 48 h was recorded by an automated trace gas recording system using 0.5 g samples of the substrate. The results showed that DM, NDF, ADF (p < 0.01), and CP (p < 0.05) degradabilities were significantly increased at 1.92 g/kg DM of SPs at 24 h, and asymptotic gas production (p = 0.05) was increased at 48 h. For in vivo experiment, 110 lactating Holstein cows (209.7 ± 65.2 DIM; 37.2 ± 6.4 kg/d milk yield) were randomly assigned to 0 (control group, CON) or 50 g/head/day SPs (SP-supplemented group). Yields of milk (p < 0.05), milk protein (p < 0.05), and milk lactose (0.05 < p < 0.10) increased on SPs supplementation; however, the milk fat percentage decreased (p < 0.05). The concentrations of individual volatile fatty acids (VFAs) (p < 0.05) and superoxide dismutase (SOD) (p < 0.01) were also increased. Rumen bacterial diversity in SP-supplemented cows was higher (p < 0.05). The relative abundances of Rikenellaceae_RC9_gut_group, Butyrivibrio, Selenomonas, and Shuttleworthia were significantly increased and that of Coprococcus was decreased (p < 0.05). Our results showed that supplementing 1.92 g/kg DM of SPs could improve the nutrient degradability in vitro and 50 g/head/day of SPs could improve milk production and antioxidant ability of dairy cows. The rumen bacterial diversity was also enhanced by SP supplementation.

Effects of Polymeric Media-Coated Gynosaponin on Microbial Abundance, Rumen Fermentation Properties and Methanogenesis in Xinjiang Goats

Gynosaponin is known to modulate rumen methanogenesis and microbial fermentation characteristics in ruminants. The current experiment aimed to determine the time-dependent effects of intraruminal polymeric media-coated gynosaponin (PMCG) supplementation on the methanogenesis, rumen fermentation properties and microbial abundance in Xinjiang goats. Eight goats were used in a 2 × 2 crossover arrangement with a PMCG group (8 g/kg DMI) and a control group (0 g/kg DMI). The experiment was divided into four phases, each lasted 21 d. Ruminal contents were obtained for analysis of rumen fermentation properties and microbial abundance. Protozoa numbers were counted by microscope and the abundance of methanogens, rumen fungi and cellulolytic bacteria were quantified by real-time PCR. The results indicated that PMCG significantly reduced methane production (p < 0.05) during the first two phases but this increased to baseline again during the last two phases. Meanwhile, the concentration of acetate decreased remarkably, which resulted in a significant reduction in the acetate to propionate ratio and total VFA concentration (p < 0.05). However, other rumen properties and dry matter intake were not affected (p > 0.05). During the first and second phases, the protozoa numbers and gene copies of methanogens, total bacteria and F. succinogens relative to the 16 s rDNA were all slightly decreased, but the statistical results were not significant. However, the ruminal supplementation of PMCG had little effect on other tested microbes. Accordingly, it was concluded that the addition of PMCG had an inhibitory effect on methane production probably due to a decline in methanogen numbers.