Next Article in Journal
Research on Countermeasures for Improving the Digital Literacy Level of Moderate-Scale Tea Farmers
Previous Article in Journal
Monitoring Agricultural Land Use Intensity with Remote Sensing and Traits
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Agriculture
Volume 15
Issue 21
10.3390/agriculture15212234
agriculture-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Tannin-Based Strategies for Mitigating Greenhouse Gas Emissions Through Nitrogen and Carbon Metabolism in Ruminants

by
Xiaoqiang Zhao
1,
Shuo Zhang
2 and
Yuanqing Zhang
2,*
1
College of Agricultural Economics and Management, Shanxi Agricultural University, Jinzhong 030801, China
2
College of Animal Science, Shanxi Agricultural University, Jinzhong 030801, China
*
Author to whom correspondence should be addressed.
Agriculture 2025, 15(21), 2234; https://doi.org/10.3390/agriculture15212234
Submission received: 12 September 2025 / Revised: 16 October 2025 / Accepted: 23 October 2025 / Published: 27 October 2025
(This article belongs to the Section Farm Animal Production)
Browse Figures
Versions Notes

Abstract

Annual greenhouse gas emissions from livestock (CO2 equivalent) are estimated at approximately 7.1 billion tons, accounting for 14.5% of global emissions, with beef and dairy cattle production contributing 41% and 20% of total emissions, respectively. Greenhouse gases released by ruminants not only lead to feed energy loss but also result in environmental degradation. Therefore, reducing greenhouse gas emissions from ruminants is crucial for the sustainable development of the ruminant industry. The primary greenhouse gases produced by ruminants include nitrous oxide from ruminant manure storage and methane generated in the rumen via the action of methanogenic archaea. Tannins, a class of polyphenolic compounds present in many plants, play a significant role in animal feed. Recent studies have shown that incorporating certain tannins and their metabolic products into diets can modulate protein metabolism and the ruminal microbiome, thereby regulating greenhouse gas emissions from ruminants. This review summarizes the types and properties of dietary tannins, as well as the latest advancements in understanding the impacts of tannins and their metabolites on cattle nutrient digestion and greenhouse gas emissions, concluding that dietary tannin supplementation can reduce greenhouse gas emissions from ruminants. Future research should focus on identifying the optimal concentrations of different tannins and their metabolites in diets to minimize ruminant greenhouse gas production while maintaining animal performance and health.

1. Introduction

In recent years, climate change has received increasing attention, with the 2023 Climate Report revealing a concerning escalation—a record-breaking number of days with a more than 1.5 °C increase in global average temperature due to increased greenhouse gas emissions—and this trend is likely to continue to increase [1]. In this context, global livestock production annually emits greenhouse gases (GHGs) equivalent to 7.1 billion tons of CO2, representing 14.5% of anthropogenic GHG emissions (Figure 1A) [2]. Notably, direct methane (CH4) and nitrous oxide (N2O) emissions from ruminants account for more than 60% of GHG emissions from livestock (Figure 1B) [3]. In recent years, numerous countries have committed to reducing their national agricultural greenhouse gas emissions. By 2030, global agricultural CH4 emissions need to be reduced by 48% and N2O emissions by 26%, relative to 2010 to limit global warming to 1.5 °C [4]. Meanwhile, it is forecasted that by 2050, as the world population increases further to 9.15 billion, increases in milk and meat production by 63% to 76% will be required to meet the growing dietary needs of the global population [5]. Hence, GHG emissions from ruminants are expected to increase further as ruminant production develops [6]. The divergence between the expansion of ruminant animal production and environmental conservation is becoming increasingly apparent. Reducing enteric GHG emissions is of paramount importance for ensuring the sustainable development of ruminant animal production. Consequently, the development of cost-effective methods for mitigating the GHG emissions of ruminant animals holds significant implications for achieving greenhouse gas reduction objectives. Thus, this review examines the formation processes and mechanisms of enteric greenhouse gas emissions in ruminant animals, summarizes recent progress in emissions reduction strategies, assesses the influence of dietary tannin supplementation, and identifies key knowledge gaps and priorities for future research.

2. Materials and Methods

This review presents a thorough analysis of the current literature on nitrogen and carbon metabolism in ruminants. It concentrates on strategies for greenhouse gas abatement and evaluates the potential utility of tannins. A structured methodology was utilized to identify and choose pertinent studies from peer-reviewed publications and scientific proceedings. To maintain data quality and uniformity, the selection was limited to documents classified as “Article”, IPCC reports, and meta-analyses, without any language limitations. An initial search yielded 1768 records. Following manual removal of duplicates and a screening of titles and abstracts, 1743 relevant articles were retained and exported as plain text for the ensuing bibliometric analysis. The inclusion of studies was contingent upon predefined criteria, including thematic pertinence, methodological rigor, and research design (encompassing experimental studies, in vitro/in vivo trials, and meta-analyses). The literature survey was performed using the Scopus, Web of Science, and Google Scholar databases, covering the period from January 2015 to August 2025. Search queries included the following keywords: ruminant nitrogen metabolism; carbon metabolism; greenhouse gas emissions; methane mitigation; tannin supplementation; condensed tannins and nitrous oxide emissions. The review prioritized research published within the last ten years, with special attention given to studies assessing intrinsic metabolic pathways, mechanisms of emission reduction, and the effectiveness of tannins in altering ruminal functions to improve environmental sustainability. This synthesis underscored shared patterns and conflicting findings across the literature, seeking to pinpoint knowledge gaps and propose directions for future research into tannin-based interventions.

3. Formation and Excretion of Greenhouse Gases in Ruminants

3.1. Nitrogen Metabolism and Nitrous Oxide Formation in Ruminants

3.1.1. Patterns of Nitrogen Metabolism in Ruminants

The utilization of N is a critical aspect of livestock production. Firstly, N represents the most expensive part of the diet [7]. Secondly, the efficiency of N utilization directly impacts the quality and the production efficiency of animal products [8]. Furthermore, the environmental impact of substantial nitrogen excretion on air and water quality has reached a non-negligible level. Therefore, improving nitrogen utilization efficiency is one of the major challenges currently faced by the livestock industry.
Rumen harbors a diverse array of prokaryotic and eukaryotic microorganisms, which are actively involved in N metabolism [9]. Although microbial involvement enhances nutrient digestion, it limits ruminant nitrogen utilization efficiency to about 25%, lower than the roughly 30% achieved in swine and poultry [10]. Crude protein intake by ruminants can be divided into rumen undegradable protein (RUP) and rumen degradable protein (RDP) [11]. Dietary RDP can be broken down into amino acids and small peptides under the action of proteases or deaminated into ammonia [12]. The fate of peptides and amino acids (AAs) absorbed into the rumen microbial cells is determined by the availability of utilizable energy sources, primarily carbohydrates (CHO). With ample CHO, AAs are transaminated or integrated into microbial protein; if they lack CHO, AAs are deaminated, with their carbon skeletons forming volatile fatty acids (VFAs) as energy sources [13]. Certain rumen bacteria are incapable of exporting amino acids (AAs) from cells, leading to the complete breakdown of surplus AAs into ammonia (NH3/NH4+), subsequently released into the rumen [14]. Meanwhile, excess rumen RDP is converted by microbes into NH3/NH4+, which is absorbed by the rumen wall and transformed into urea in the liver [15]. Between 40% and 80% of the urea synthesized in the liver re-enters the rumen via the salivary glands for microbial protein synthesis, with the remainder being excreted in urine [15]. Dietary RUP remains resistant to microbial breakdown and subsequently transits with the ruminal digesta into the lower gastrointestinal tract (Figure 2).
At the microbial level of the rumen, ammonia is mainly assimilated into microbial protein via the glutamate dehydrogenase and the glutamine synthetase–glutamate synthase pathways when fermentable carbohydrates are available, thereby coupling nitrogen capture to energy supply [16]. Post-ruminally, microbial protein and dietary RUP are hydrolyzed by abomasal and pancreatic proteases to peptides and free amino acids, which are absorbed in the small intestine and partitioned between tissue protein synthesis and oxidation [17]. Amino-nitrogen released during oxidation is converted to urea through the hepatic urea cycle, and blood urea is either excreted by the kidney or recycled to the rumen via salivary flow and epithelial UT-B transporters; recycled urea is hydrolyzed by microbial urease to NH3/NH4+ to sustain microbial protein synthesis when RDP is limiting [18]. Collectively, fluxes across microbial assimilation, post-ruminal digestion/absorption, hepatic ureagenesis, urea recycling, and urinary/fecal excretion determine overall nitrogen utilization efficiency and the downstream forms of nitrogen loss relevant to environmental emissions.

3.1.2. Nitrogen Excretion and Nitrous Oxide Production in Ruminants

The N not assimilated by ruminant animals is excreted through feces and urine. In ruminant N excretion, fecal N accounts for 27.9–36.8% of total N excretion, while urinary N accounts for 63.2–72.1% [19]. Fecal N mainly includes undigested dietary N, endogenous N, and microbial N [20]. Urine contains complex nitrogenous compounds, predominantly the urea (52.1–93.5%) of N content, along with creatinine, creatine, uric acid, allantoin, hippuric acid, and minor levels of amino acids, NH3, xanthine, and hypoxanthine [21]. When urine and feces interact with soil, microbial urease activity in soil rapidly hydrolyzes the urinary urea to NH4+ with partial atmospheric emission and partial soil absorption for N2O production. Fecal N, predominantly in recalcitrant proteins and nucleic acids, exhibits limited degradation and volatilization, thus contributing to slower N2O emission. Soil N2O synthesis predominantly involves nitrification (autotrophic and heterotrophic), denitrification, chemo-denitrification, and dissimilatory nitrate reduction to ammonium pathways (Figure 3) [22,23].
Nitrification
Nitrification primarily involves the oxidation of NH3+ and NO2−, occurring under aerobic conditions where NH4+ or NH3+ is oxidized to NO2−, and eventually to NO3−, facilitated by chemolithoautotrophic microorganisms and nitrite-oxidizing bacteria [24]. During this oxidation process, a small portion of the produced hydroxylamine (NH2OH) reacts to form N2O−. The primary effect of this process is to provide NO3−, with the N2O yield from hydroxylamine being 3 to 6 orders of magnitude lower than that produced from NO3−. Heterotrophic nitrification follows a similar pathway to autotrophic nitrification, while heterotrophic nitrification is carried out by heterotrophic microorganisms (primarily fungi), which utilize inorganic or organic nitrogen to transform it into O3−. Heterotrophic nitrification is generally recognized as occurring mainly in grassland and forest soils, with almost negligible occurrence in cultivated land soils [25].
Denitrification
Denitrification is a process occurring under anaerobic conditions where soil NO2− and NO3− are reduced to N2, NO, and N2O [26]. This process facilitates the transfer of nitrogen from the soil to the atmospheric environment and is a key biological process in the nitrogen cycle. Unlike nitrification, N2O is an intermediate product in the denitrification process. The production of N2O is influenced by various factors, such as lower soil pH or higher NO3− content, which can lead to increased N2O emissions during denitrification [27]. Generally, nitrification and denitrification occur concurrently. In an optimal environment, NO2− and NO3− produced via nitrification can be directly utilized by denitrifying bacteria. Besides the denitrification process mediated by denitrifying bacteria, Smith et al. have identified a subset of soil bacteria not traditionally associated with denitrification that nonetheless possess the ability to reduce nitrate nitrogen to ammonium, incidentally producing nitrous oxide (N2O) [28]. Further research indicates that under conducive soil conditions, the production of N2O via this dissimilatory nitrate reduction to ammonium can, in fact, exceed the levels generated through the denitrifying bacteria [29]. Chemical denitrification is a process occurring purely through chemical decomposition and catalysis, without reliance on microbial activity. This process typically takes place in low-pH environments [30]. NO is the primary product of this chemical reaction, while N2O is a secondary byproduct. The quantity of N2O produced via chemical denitrification is so minimal that it is considered negligible [31].

3.2. CH4 Formation in Ruminants

3.2.1. CH4 Formation in Rumen

Most methane (CH4) produced by ruminants originates from the rumen. Rumen CH4 is a byproduct of the digestion of ruminant feed. However, ruminants do not produce CH4 directly; instead, CH4 is produced through the fermentation of feed by the abundant microbial populations in the rumen. The microbial fermentation of dietary organic matter results in the production of volatile fatty acids (VFAs), alongside the concurrent generation of CO2 and H2, and methanogenic archaea in the rumen exploit these by-products to produce CH4 (Figure 4) [32].
Based on the substrates utilized by methanogens, methane (CH4) production encompasses three primary pathways: hydrogenotrophic (reduction of H2/CO2), acetoclastic (decarboxylation of acetate), and methylotrophic (involving the transformation of methanol, formate, and other one-carbon molecules). Predominantly, the hydrogenotrophic route accounts for about 82% of ruminal CH4, with about 18% of CH4 synthesis occurring through other organic substrates such as formate, acetate, and methanol [33].
Ruminal CH4 production involves a series of enzymatic processes. In the hydrogenotrophic pathway, C1 units are transformed into CH4 through enzymes such as formylmethanofuran dehydrogenase and methyl coenzyme M reductase (mcr). Similar enzymatic steps occur in CH4 production from acetate or methyl compounds, with the final reduction to CH4 also mediated by mcr [34]. The process is supported by coenzymes such as F420, which facilitates initial electron transfer; F430, an mcr activator; and Coenzyme B (CoB), which provides electron carriers for CH4 synthesis. Moreover, the dominant archaeal taxa in the rumen belong to Methanobacteriales, with contributions from Methanomicrobiales and methyl-reducing Methanomassiliicoccales (which reduce methanol/methylamines with H2); acetoclastic Methanosarcinales are generally minor in the rumen ecosystem [35,36]. At the pathway level, CO2 reduction proceeds via the Wolfe cycle: CO2 is fixed to formyl-methanofuran (catalyzed by formyl-methanofuran dehydrogenase), transferred to tetrahydromethanopterin (H4MPT), and stepwise-reduced through methenyl-H4MPT/methylene-H4MPT intermediates (F420-dependent dehydrogenase/reductase) to methyl-H4MPT; and then the methyl group is transferred to coenzyme M (CoM) by the methyl-H4MPT:CoM methyltransferase (Mtr); and finally methyl-CoM is reduced to CH4 by methyl-coenzyme M reductase (mcr, cofactor F430) with coenzyme B (CoB) as the electron donor. Energy conservation is coupled to ion-translocating Mtr and heterodisulfide reduction (Hdr) systems [37,38,39].

3.2.2. CH4 Formation in Feces

The decomposition of cows’ feces represents the second largest source of methane (CH4) emissions in the dairy industry [40]. In particular, manure stored in the cool-temperate European climate significantly contributes to these emissions. It is estimated that approximately 12% of total CH4 emissions from the dairy system are attributable to the decomposition processes occurring within these manure storage environments [41]. Ruminant feces, rich in organic matter and moisture, caters to the needs of various microorganisms. The organic matter in animal feces undergoes sequential decomposition via microbial action, resulting in the production of substances such as CH4. This process mainly comprises three stages: hydrolysis, acidogenesis, and methanogenesis. Fecal CH4 formation is governed by the coupling between fermentative consortia and methanogenic archaea within dung/manure microenvironments. Primary fermentation yields acetate, H2, and CO2, which are converted to CH4 via the acetoclastic and hydrogenotrophic pathways [42]. The relative contributions of these pathways are modulated via temperature, moisture, pH, oxygen diffusion, residence time, and system configuration: liquid/slurry storage or deep heaps sustain anoxia and favor methanogenesis, whereas pasture dung pats frequently develop an aerobic surface crust that limits the diffusion of reduced intermediates and permits partial CH4 oxidation by methanotrophs [43]. Urine co-deposition further alters pH/redox via ureolysis, and warm–humid conditions, larger/thicker pats, and prolonged storage systematically increase fecal CH4 potential, which helps to explain the variability in reported emission factors across climates and management systems [44]. Comparative assessments identify volatile solids load and residence time as primary predictors of manure-borne CH4 in housing/storage systems and provide the basis for mitigation strategies centered on storage management and stabilization [45].

4. Sources and Classification of Tannins

4.1. Sources of Tannins

Tannins are widely distributed in trees, shrubs, leguminous forages, cereal grains, and other crops, and concentrations are influenced by various factors such as temperature, light exposure, rainfall, soil quality, and stress. Different tissues of plants, such as stems, leaves, flowers, fruits, and seeds, contain varying concentrations of tannins, with higher levels typically found in leaves and petals. Both HT and CT may coexist in the same plant, although their relative quantities vary among different species [46]. CTs are predominantly found in dicotyledonous plants, such as legumes, Rosaceae, and Rutaceae, and to a lesser extent in monocotyledonous plants including grasses. HTs are mainly present in tropical and subtropical plants, including oaks, acacias, and tropical legumes (such as Terminalia and Caesalpinia species) [47]. Current research on fruit tannins primarily focuses on persimmons, grapes, and pomegranates. Studies on persimmons reveal that condensed tannins accumulate continuously throughout the fruit’s growth period and reach relatively high levels after flowering [48]. Related studies indicate that fruit tannin cells are primarily found in processing byproducts such as peel and seeds. Among common animal feed ingredients such as corn, soybeans, sorghum, wheat, and barley, sorghum is the feed material with the highest tannin content [49].

4.2. Types and Characteristics of Tannins

Tannins, which are water-soluble polyphenolic compounds, are prevalent in a variety of plants, displaying significant structural variation with molecular weights typically ranging between 500 and 3000, though highly polymerized tannins can have weights exceeding 10,000 [50]. These compounds can form both reversible and irreversible complexes with proteins, polysaccharides (including cellulose, hemicellulose, and pectin), nucleic acids, and minerals, though they more commonly form irreversible complexes with proteins [51]. Tannins are generally classified into two categories: hydrolysable tannins (HTs) and condensed tannins (CTs) (Figure 5) [52,53]. HTs are complexes formed through esterification reactions between carbohydrates (such as glucose, glucitol, and quinic acid) and polyphenolic substances (such as gallic acid (GA) or hexahydroxydiphenic acid) [54]. HTs readily undergo hydrolysis under acidic conditions or in the presence of tannin hydrolases, yielding products including GA, catechol, and resorcinol [55]. Gallotannin is not widely distributed, whereas tannic acid is a well-known HT formed via the esterification of 8–10 GA units centered on a glucose moiety. CTs, also known as proanthocyanidins, are polymers composed of flavonoid compounds. Both HTs and CTs can form stable, insoluble tannin–protein complexes in acidic conditions through hydrogen bonding [53]. These complexes remain stable until the pH falls below 3.5, at which point they decompose, releasing free proteins [56]. With respect to greenhouse gas mitigation, both HTs and CTs can lower enteric CH4 by reducing reductant supply (via suppressing protozoa and some fibrolytic microbes) and, in some cases, through direct antimethanogenic effects, and both decrease ruminal proteolysis/deamination, shifting N from urine to feces, which tends to reduce NH4+ volatilization and urine-derived N2O. CTs, being non-hydrolysable, generally provide more persistent protein protection at rumen pH and more consistent responses at low–moderate doses, whereas HTs rely on hydrolysis to phenolic acids and show more dose-sensitive effects on intake and digestibility, so overall outcomes differ by type, dose, source/purity, delivery form, and basal diet.

5. Impacts and Mechanisms of Tannins on Greenhouse Gas Mitigation in Ruminants

5.1. Influence of Tannins on Feed Intake and Digestive Efficiency in Ruminants

Table 1 presents research findings on the effects of tannins from different plant sources on ruminant feed intake and nutrient digestibility. It shows that dietary supplementation with tannin generally decreased the ruminant’s dry matter intake (DMI) and nutrient digestibility, with variations based on tannin type, dosage, and animal species. When ruminants consume plants with high tannin levels, the tannins react with salivary and oral mucosal proteins to cause astringency, affecting palatability and feed intake [57]. Numerous studies have reported reductions in DMI and associated growth performance with tannin supplementation [58,59,60,61]. For instance, Grainger et al. found that adding 163 and 326 g/kg of dry matter (DM) of blackthorn bark extract (a type of CT) to dairy cow diets reduced milk yield, fat, and protein, as well as DMI [62]. Similarly, Pifeiro-Vazquez et al. showed that adding 4% DM of chestnut tannin extract (a type of CT) to heifer diets decreased feed intake, DM, organic matter (OM) and neutral detergent fiber (NDF) digestibility [63]. Min et al. noted that dietary supplementation with 55 g/kg of DM CT significantly reduced feed intake and nutrient digestibility in ruminants [64]. However, these effects are not universal. Froutos et al. reported that adding chestnut tannin (a type of HT) to sheep diets did not affect dry matter intake [65]. Puchala et al. found that feeding goats Lespedeza cuneata (a plant rich in CT) increased dry matter intake [66]. These varying results suggest that tannins’ effect on animal feed intake is largely influenced by tannin type, dosage, and the animal’s physiological state. From an emissions standpoint, lower DMI may reduce daily enteric CH4, but concomitant decreases in milk yield or weight gain can increase product-based emission intensity.
Research also indicates that elevated tannin levels in ruminant diets can impair nutrient digestibility, particularly at higher doses [67]. For example, Wischer et al. found that adding 43.5 g/kg of chestnut tannin (a type of HT) to sheep diets decreased crude protein (CP) digestibility, but not DM, OM, and NDF digestibility [68]. Carulla et al. (2005) observed that adding 41 g/kg of DM of blackthorn extract (a type of CT) to sheep diets significantly reduced OM, CP, NDF, and acid detergent fiber (ADF) digestibility [69]. Conversely, several studies also indicated that dietary supplementation with tannins did not affect nutrient digestibility [70,71,72]. These discrepancies underscore the need for further research to elucidate the dose- and context-dependent effects of tannins on nutrient utilization. Lower digestibility can divert more degradable volatile solids to feces, increasing manure CH4 potential; conversely, low-to-moderate inclusion that reduces hydrogen availability without impairing performance can lower both the CH4 yield and intensity, underscoring the need to match the dose, tannin type (CT vs. HT), basal diet, and delivery form, as well as to report both absolute emissions and intensity metrics.

5.2. Regulation of Rumen GHG Production by Tannins

5.2.1. Tannins Alter the Type of Nitrogen Emission from Ruminants

Table 2 presents research findings on the effects of tannins from different plant sources on CH4 and N2O emissions in ruminants. It indicates that tannin supplementation can reduce CH4 and N2O production, though results vary by tannin type and animal species. A previous study indicated that mitigating protein degradation in the rumen improves N utilization and reduces GHG emissions when ruminants are fed high-N forages (25–35 g/kg DM) [52]. Tannins, despite their structural diversity, exhibit a common functional property of protein binding, thereby shifting nitrogen metabolism from the rumen to the hindgut [73]. This attribute is significant in decreasing the solubility and degradation rate of dietary proteins within the rumen. Al-Dobaib et al. demonstrated that including 2–3% chestnut tannins in alfalfa hay-based diets significantly reduced ruminal protein degradation in sheep [74]. The findings of Carulla et al. corroborate this, where 41 g of mimosa tannin addition to sheep diets led to a reduced rumen NH3-N concentration [69]. Moreover, Getachew et al. observed that while tannic acid additions of 20 or 40 g/kg of DM to alfalfa hay did not alter the 72 h NH3-N concentration, dietary supplementation with 60 g/kg of DM tannic acid significantly reduced the NH3-N concentration [75]. Notably, Yang et al. reported reduced rumen NH3-N concentrations with the addition of 13.0 or 26.0 g/kg DM of tannic acid in beef cattle diets. In another study, Mueller-Harvey discovered that the degree to which tannins enhance protein digestion and absorption in ruminants is influenced by the binding affinity between tannins and proteins [67].
Tannins also modulate ruminant N metabolism by adjusting the excretion ratio of fecal N to urinary N. In a study conducted by Getachew et al. on sheep fed a diet based on alfalfa hay, adding 30, 60, or 90 g/kg of DM of tannic acid increased the fecal N fraction of the total excreted N while decreasing the urinary N proportion [75]. Similarly, Yang et al. found that supplementing beef cattle diets with 6.5, 13.0, or 26.0 g/kg of DM of tannic acid raised the fecal N percentage of total excreted N and reduced the urinary N fraction, along with decreasing the proportion of urea N in the urine [76]. Zhou et al. found that dietary supplementation with 16.9 g/kg of DM tannic acid significantly decreased urine N2O emissions [77]. However, a previous study also indicated that dietary supplementation with 0.14%, 0.29% and 0.43% of DM CT significantly increased urine N2O emissions [78]. In dairy cows and sheep, including CT also increased fecal N excretion and decreased urinary N excretion without affecting N balance [64]. The reason for this may be that the similarity in pH levels between the large intestine (5.5–7.0) and the rumen allows certain free tannins to re-form tannin–protein complexes in the colon, thus decreasing the breakdown of nitrogen into absorbable NH3 [56]. This is a key mechanism via which tannins elevate fecal N and reduce urinary N. From an environmental conservation perspective, the tannin-induced alteration in N excretion is advantageous because nitrogen in feces is predominantly organic and less volatile compared to urinary N, which primarily exists as urea and is more susceptible to microbial degradation into NH3 and subsequent N2O production [21]. Therefore, increasing fecal N and decreasing urinary N can lead to reductions in NH3 and N2O emissions [79], contributing positively to environmental protection. Additionally, tannin–protein complexes in feces slow the degradation of fecal N in soil. Notably, a previous study has shown that supplementation with 15.2 g/kg of DM of the HT metabolite GA significantly reduces N2O-N emissions, decreasing N2O-N flux by 32.4% under low-crude-protein (CP) conditions and by 33.6% under high-CP conditions, while also markedly reducing soil NH4-N and NO3− concentrations [80].

5.2.2. Tannins Alter the CH4 Emission from Ruminants

CH4, as a byproduct of rumen metabolism, not only results in the loss of feed energy but also exacerbates GHG effects in the atmosphere. Several studies have demonstrated that adding either CT or HT to the diet significantly inhibits CH4 production [81,82,83,84].For example, Roth et al. examined the impact of tannins extracted from chestnut, mimosa, and oak on in vitro gas production and CH4 output, finding that tannin addition significantly reduced CH4 production [85]. Additionally, Geerkens et al. reported that adding 83 or 167 mg/g of dry forage of gallic acid (GA) significantly reduced 24 h CH4 production [86]. As previously mentioned, the primary pathway of CH4 production involves ruminal methanogens. Tavendale et al. investigated the mechanism of CT’s inhibitory effect on CH4 through pure culture experiments with methanogens, proposing that CT reduces CH4 output by directly inhibiting methanogen growth and indirectly suppressing fiber digestion [87]. Similarly, Jayanegara et al. suggested that dietary supplementation with tannins inhibits rumen carbohydrate degradation, reducing H2 production, thereby diminishing the substrate available for CH4 synthesis [88]. In vivo experiments by Carulla et al. showed that adding 41 g of mimosa tannin (purity 0.615 g/g CT) to sheep diets significantly reduced CH4 production by an average of 13% [69]. Likewise, Grainger et al. reported that adding 163 g/d and 244 g/d of mimosa tannin to dairy cow diets significantly reduced CH4 output by 14% and 29%, respectively [62]. Moreover, Yang et al. noted significant CH4 reduction upon adding 6.5, 13.0, or 26.0 g/kg of DM of tannic acid without affecting beef cattle feed intake [89]. However, Beauchemin et al. (2007) reported no effect on CH4 production when adding 2% chestnut tannin to growing beef cattle diets [90]. Studies indicate that when the diet contains high levels of tannin, some free tannins can bind with cellulose to form complexes that inhibit fiber breakdown while also suppressing fiber-degrading microbial growth and enzyme activity, thereby decreasing CH4 emissions [91]. These results suggest that the CH4 inhibitory effect of tannins is influenced by factors such as the tannin source, additive dosage, and diet composition. Therefore, to achieve CH4 emission reduction through tannin supplementation in the diet, a balance must be found in conjunction with animal production. Differences among studies regarding CH4 mitigation efficacy can be attributed to several interacting factors, including animal species, basal diet composition, supplementation method, and extract purity. For instance, small ruminants often show stronger responses due to higher methanogen sensitivity, while high-fiber diets can alter hydrogen dynamics, thereby affecting CH4 yield.
From a practical perspective, including tannins raises several limitations. Their cost may increase feed expenses, and excessive inclusion can impair fiber digestibility or animal intake, compromising performance. Furthermore, interactions with other methane inhibitors (e.g., 3-NOP or lipid supplements) remain underexplored but could have synergistic potential. Hence, optimizing dosage and integration strategies is crucial for sustainable and economically viable CH4 mitigation.
Table 2. Studies of plant tannins regulating rumen CH4 and N2O production.
Table 2. Studies of plant tannins regulating rumen CH4 and N2O production.
Types of
Tannins		SourcesExperimental AnimalsAdditive DosageCH4 and N2O ProductionReference
Tannic acid–Castrated male cattle16.9 g/kg of DMN2O production ↓[77]
CTAcacia mearnsiiSheep0.14%, 0.29% and 0.43% DMN2O production ↑[78]
HT metabolite–Beef cattle15.2 g/kgN2O production ↓[80]
HT metabolite–In vitro rumen fermentation5, 10, 15 and 20 mgCH4 production ↓[86]
CTL. pedunculatusIn vitro rumen fermentation0.5g DMCH4 production ↓[87]
CTAcacia mearnsiiSheep41 gCH4 production ↓[69]
CTAcacia mearnsiiDairy cattle163 and 244 g/dCH4 production ↓[62]
Tannic acid–Beef cattle6.5, 13.0, or 26.0 g/kg of DMCH4 production ↓[89]
CTChestnutBeef cattle2% DMDid not affect CH4 production[90]
Note: CT, condensed tannin; HT, hydrolyzed tannin; DM, dry matter; ↓, down regulated, ↑, up regulated, –, unreported.

6. Perspectives

Current research indicates that adding tannins or their metabolites to ruminant diets can mitigate nitrous oxide emissions by altering the mode of nitrogen excretion, specifically by increasing the proportion of fecal nitrogen and decreasing urinary nitrogen. Additionally, including tannins in the diet modulates the gastrointestinal microbial ecosystem, primarily by altering the activities of methanogens and fiber-degrading microbes, thereby reducing methane emissions from ruminants. This process is influenced by factors such as the source of tannins, dosage, and dietary composition.
However, tannin supplementation may negatively impact nutrient digestibility and feed intake in ruminants, emphasizing the need for a balanced approach that aligns greenhouse gas emissions mitigation with animal productivity. Future studies should focus on mechanistic elucidation using metagenomic, metatranscriptomic, and metabolomic analyses to characterize the microbial pathways and host–microbe interactions underlying tannin-mediated mitigation. Moreover, long-term in vivo trials under tropical and subtropical conditions are essential for validating the consistency of these effects under diverse production systems.
Further, integrative approaches combining tannins with complementary additives (e.g., 3-NOP, essential oils, or nitrate) should be explored to optimize synergistic effects while minimizing anti-nutritional impacts. Isotopic tracing and multi-omics data integration could help to uncover the molecular regulation of nitrogen partitioning and rumen fermentation dynamics, advancing precision feeding strategies. Overall, emerging technologies and context-specific trials will be critical for translating tannin-based mitigation strategies into sustainable livestock production practices.

Author Contributions

Conceptualization, Y.Z.; methodology, S.Z.; writing—original draft preparation, X.Z. and S.Z.; writing—review and editing, Y.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was financially supported by the Earmarked Fund for Modern Agro-Industry Technology Research System (2025CYJSTX13).

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Acknowledgments

The authors express their gratitude to fellow students in the laboratory for their assistance.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Ripple, W.J.; Wolf, C.; Gregg, J.W.; Rockström, J.; Newsome, T.M.; Law, B.E.; Marques, L.; Lenton, T.M.; Xu, C.; Huq, S.; et al. The 2023 State of the Climate Report: Entering Uncharted Territory. BioScience 2023, 73, 841–850. [Google Scholar] [CrossRef]
  2. Gerber, P.J.; Hristov, A.N.; Henderson, B.; Makkar, H.; Oh, J.; Lee, C.; Meinen, R.; Montes, F.; Ott, T.; Firkins, J.; et al. Technical Options for the Mitigation of Direct Methane and Nitrous Oxide Emissions from Livestock: A Review. Animal 2013, 7, 220–234. [Google Scholar] [CrossRef]
  3. Gerber, P.J.; Steinfeld, H.; Henderson, B.; Mottet, A.; Opio, C.; Dijkman, J.; Falcucci, A.; Tempio, G. Tackling Climate Change Through Livestock: A Global Assessment of Emissions and Mitigation Opportunities; Food and Agriculture Organization of the United Nations: Rome, Italy, 2013. [Google Scholar]
  4. Jantke, K.; Hartmann, M.J.; Rasche, L.; Blanz, B.; Schneider, U.A. Agricultural Greenhouse Gas Emissions: Knowledge and Positions of German Farmers. Land 2020, 9, 130. [Google Scholar] [CrossRef]
  5. Alexandratos, N.; Bruinsma, J. World Agriculture Towards 2030/2050: The 2012 Revision; Food and Agriculture Organization of the United Nations: Rome, Italy, 2012. [Google Scholar]
  6. Eshel, G.; Shepon, A.; Makov, T.; Milo, R. Land, Irrigation Water, Greenhouse Gas, and Reactive Nitrogen Burdens of Meat, Eggs, and Dairy Production in the United States. Proc. Natl. Acad. Sci. USA 2014, 111, 11996–12001. [Google Scholar] [CrossRef]
  7. Paul, S.S.; Chanu, Y.M.; Dey, A. Options for Improving Nitrogen Utilization Efficiency in Ruminants. Indian J. Anim. Nutr. 2016, 33, 1–10. [Google Scholar] [CrossRef]
  8. Tan, P.; Liu, H.; Zhao, J.; Gu, X.; Wei, X.; Zhang, X.; Ma, N.; Johnston, L.J.; Bai, Y.; Zhang, W. Amino Acids Metabolism by Rumen Microorganisms: Nutrition and Ecology Strategies to Reduce Nitrogen Emissions from the inside to the Outside. Sci. Total Environ. 2021, 800, 149596. [Google Scholar] [CrossRef]
  9. Ungerfeld, E.M.; Cancino-Padilla, N.; Vera-Aguilera, N. Fermentation in the Rumen. In Microbial Fermentations in Nature and as Designed Processes; Hurst, C.J., Ed.; Wiley: Hoboken, NJ, USA, 2023; pp. 133–165. ISBN 978-1-119-84997-1. [Google Scholar]
  10. Kohn, R.A.; Dinneen, M.M.; Russek-Cohen, E. Using Blood Urea Nitrogen to Predict Nitrogen Excretion and Efficiency of Nitrogen Utilization in Cattle, Sheep, Goats, Horses, Pigs, and Rats. J. Anim. Sci. 2005, 83, 879–889. [Google Scholar] [CrossRef]
  11. Pérez-Barbería, F.J. The Ruminant: Life History and Digestive Physiology of a Symbiotic Animal. In Sustainable and Environmentally Friendly Dairy Farms; SpringerBriefs in Applied Sciences and Technology; Springer International Publishing: Cham, Switzerland, 2020; pp. 19–45. ISBN 978-3-030-46059-4. [Google Scholar]
  12. Klatt, B.J. Determining Rumen Degradable Protein Requirements in Growing Beef Cattle. Ph.D. Thesis, University of Illinois at Urbana-Champaign, Champaign, IL, USA, 2019. [Google Scholar]
  13. Van Soest, P.J. Nutritional Ecology of the Ruminant; Cornell University Press: Ithaca, NY, USA, 2018. [Google Scholar]
  14. Tamminga, S. Protein Degradation in the Forestomachs of Ruminants. J. Anim. Sci. 1979, 49, 1615–1630. [Google Scholar] [CrossRef]
  15. Reynolds, C.K.; Kristensen, N.B. Nitrogen Recycling through the Gut and the Nitrogen Economy of Ruminants: An Asynchronous Symbiosis. J. Anim. Sci. 2008, 86, E293–E305. [Google Scholar] [CrossRef]
  16. Pengpeng, W.; Tan, Z. Ammonia Assimilation in Rumen Bacteria: A Review. Anim. Biotechnol. 2013, 24, 107–128. [Google Scholar] [CrossRef]
  17. Reddy, P.R.K.; Hyder, I. Ruminant Digestion. In Textbook of Veterinary Physiology; Das, P.K., Sejian, V., Mukherjee, J., Banerjee, D., Eds.; Springer Nature: Singapore, 2023; pp. 353–366. ISBN 978-981-19-9410-4. [Google Scholar]
  18. Getahun, D.; Alemneh, T.; Akeberegn, D.; Getabalew, M.; Zewdie, D. Urea Metabolism and Recycling in Ruminants. Biomed. J. Sci. Tech. Res. 2019, 20, 14790–14796. [Google Scholar] [CrossRef]
  19. Li, Y.L.; Beauchemin, K.A.; McAllister, T.A.; Yang, W.Z. Intakes and Excretion Route of Nitrogen, Phosphorous and Sulfur by Finishing Beef Heifers Fed Increasing Levels of Wheat Dried Distillers Grains with Solubles to Substitute for Barley Grain and Barley Silage. Livest. Sci. 2014, 170, 43–52. [Google Scholar] [CrossRef]
  20. Harmeyer, J.; Martens, H. Aspects of Urea Metabolism in Ruminants with Reference to the Goat. J. Dairy Sci. 1980, 63, 1707–1728. [Google Scholar] [CrossRef]
  21. Dijkstra, J.; Oenema, O.; Van Groenigen, J.W.; Spek, J.W.; Van Vuuren, A.M.; Bannink, A. Diet Effects on Urine Composition of Cattle and N2O Emissions. Animal 2013, 7, 292–302. [Google Scholar] [CrossRef]
  22. Zhu, X.; Burger, M.; Doane, T.A.; Horwath, W.R. Ammonia Oxidation Pathways and Nitrifier Denitrification Are Significant Sources of N2O and NO under Low Oxygen Availability. Proc. Natl. Acad. Sci. USA 2013, 110, 6328–6333. [Google Scholar] [CrossRef]
  23. Schils, R.L.M.; Eriksen, J.; Ledgard, S.F.; Vellinga, T.V.; Kuikman, P.J.; Luo, J.; Petersen, S.O.; Velthof, G.L. Strategies to Mitigate Nitrous Oxide Emissions from Herbivore Production Systems. Animal 2013, 7, 29–40. [Google Scholar] [CrossRef]
  24. Arp, D.J.; Stein, L.Y. Metabolism of Inorganic N Compounds by Ammonia-Oxidizing Bacteria. Crit. Rev. Biochem. Mol. Biol. 2003, 38, 471–495. [Google Scholar] [CrossRef]
  25. Chen, Z.; Ding, W.; Xu, Y.; Müller, C.; Rütting, T.; Yu, H.; Fan, J.; Zhang, J.; Zhu, T. Importance of Heterotrophic Nitrification and Dissimilatory Nitrate Reduction to Ammonium in a Cropland Soil: Evidences from a 15N Tracing Study to Literature Synthesis. Soil Biol. Biochem. 2015, 91, 65–75. [Google Scholar] [CrossRef]
  26. Philippot, L.; Čuhel, J.; Saby, N.P.A.; Chèneby, D.; Chroňáková, A.; Bru, D.; Arrouays, D.; Martin-Laurent, F.; Šimek, M. Mapping Field-scale Spatial Patterns of Size and Activity of the Denitrifier Community. Environ. Microbiol. 2009, 11, 1518–1526. [Google Scholar] [CrossRef]
  27. Knowles, R. Denitrification. Microbiol. Rev. 1982, 46, 43–70. [Google Scholar] [CrossRef]
  28. Smith, M.S.; Zimmerman, K. Nitrous Oxide Production by Nondenitrifying Soil Nitrate Reducers. Soil Sci. Soc. Am. J. 1981, 45, 865–871. [Google Scholar] [CrossRef]
  29. Binnerup, S.J.; Jensen, K.; Revsbech, N.P.; Jensen, M.H.; Sørensen, J. Denitrification, Dissimilatory Reduction of Nitrate to Ammonium, and Nitrification in a Bioturbated Estuarine Sediment as Measured with 15N and Microsensor Techniques. Appl. Environ. Microbiol. 1992, 58, 303–313. [Google Scholar] [CrossRef]
  30. Van Cleemput, O.; Baert, L. Nitrite: A Key Compound in N Loss Processes under Acid Conditions? Plant Soil 1984, 76, 233–241. [Google Scholar] [CrossRef]
  31. Kappelmeyer, U.; Kuschk, P.; Stottmeister, U. Model Experiments on the Influence of Artificial Humic Compounds on Chemodenitrification. Water Air Soil Pollut. 2003, 147, 317–330. [Google Scholar] [CrossRef]
  32. Lan, W.; Yang, C. Ruminal Methane Production: Associated Microorganisms and the Potential of Applying Hydrogen-Utilizing Bacteria for Mitigation. Sci. Total Environ. 2019, 654, 1270–1283. [Google Scholar] [CrossRef]
  33. Hungate, R.E.; Smith, W.; Bauchop, T.; Yu, I.; Rabinowitz, J.C. Formate as an Intermediate in the Bovine Rumen Fermentation. J. Bacteriol. 1970, 102, 389–397. [Google Scholar] [CrossRef]
  34. Ferry, J.G. Methane: Small Molecule, Big Impact. Science 1997, 278, 1413–1414. [Google Scholar] [CrossRef]
  35. Janssen, P.H.; Kirs, M. Structure of the Archaeal Community of the Rumen. Appl. Environ. Microbiol. 2008, 74, 3619–3625. [Google Scholar] [CrossRef]
  36. Henderson, G.; Cox, F.; Ganesh, S.; Jonker, A.; Young, W.; Janssen, P.H. Rumen Microbial Community Composition Varies with Diet and Host, but a Core Microbiome Is Found across a Wide Geographical Range. Sci. Rep. 2015, 5, 14567. [Google Scholar] [CrossRef] [PubMed]
  37. Liu, Y.; Whitman, W.B. Metabolic, Phylogenetic, and Ecological Diversity of the Methanogenic Archaea. Ann. N. Y. Acad. Sci. 2008, 1125, 171–189. [Google Scholar] [CrossRef]
  38. Thauer, R.K.; Kaster, A.-K.; Seedorf, H.; Buckel, W.; Hedderich, R. Methanogenic Archaea: Ecologically Relevant Differences in Energy Conservation. Nat. Rev. Microbiol. 2008, 6, 579–591. [Google Scholar] [CrossRef] [PubMed]
  39. Ermler, U.; Grabarse, W.; Shima, S.; Goubeaud, M.; Thauer, R.K. Crystal Structure of Methyl-Coenzyme M Reductase: The Key Enzyme of Biological Methane Formation. Science 1997, 278, 1457–1462. [Google Scholar] [CrossRef]
  40. Ramin, M.; Chagas, J.C.; Pal, Y.; Danielsson, R.; Fant, P.; Krizsan, S.J. Reducing Methane Production from Stored Feces of Dairy Cows by Asparagopsis taxiformis. Front. Sustain. Food Syst. 2023, 7, 1187838. [Google Scholar] [CrossRef]
  41. Hindrichsen, I.K.; Wettstein, H.R.; Machmüller, A.; Jörg, B.; Kreuzer, M. Effect of the Carbohydrate Composition of Feed Concentratates on Methane Emission from Dairy Cows and Their Slurry. Environ. Monit. Assess. 2005, 107, 329–350. [Google Scholar] [CrossRef]
  42. Sutaryo, S.; Adiwinarti, R.; Ward, A.J.; Kurihara, M.; Purnomoadi, A. Effect of Different Feeding Management on the Respiratory Methane Emission and Feces-Derived Methane Yield of Goat. J. Adv. Vet. Anim. Res. 2019, 6, 431–437. [Google Scholar] [CrossRef]
  43. Liu, C.; Zhu, Z.P.; Liu, Y.F.; Guo, T.J.; Dong, H.M. Diversity and Abundance of the Rumen and Fecal Methanogens in Altay Sheep Native to Xinjiang and the Influence of Diversity on Methane Emissions. Arch. Microbiol. 2012, 194, 353–361. [Google Scholar] [CrossRef] [PubMed]
  44. Malheiros, J.M.; Correia, B.S.B.; Ceribeli, C.; Bruscadin, J.J.; Diniz, W.J.S.; Banerjee, P.; Vieira, D.d.S.; Cardoso, T.F.; Andrade, B.G.N.; Petrini, J.; et al. Ruminal and Feces Metabolites Associated with Feed Efficiency, Water Intake and Methane Emission in Nelore Bulls. Sci. Rep. 2023, 13, 18001. [Google Scholar] [CrossRef] [PubMed]
  45. Lileikis, T.; Nainienė, R.; Bliznikas, S.; Uchockis, V. Dietary Ruminant Enteric Methane Mitigation Strategies: Current Findings, Potential Risks and Applicability. Animals 2023, 13, 2586. [Google Scholar] [CrossRef]
  46. Haslam, E. Plant Polyphenols: Vegetable Tannins Revisited; CUP Archive: Cambridge, UK, 1989. [Google Scholar]
  47. Reed, J.D. Nutritional Toxicology of Tannins and Related Polyphenols in Forage Legumes. J. Anim. Sci. 1995, 73, 1516–1528. [Google Scholar] [CrossRef]
  48. Tessmer, M.A.; Kluge, R.A.; Appezzato-da-Glória, B. The Accumulation of Tannins during the Development of ‘Giombo’ and ‘Fuyu’ Persimmon Fruits. Sci. Hortic. 2014, 172, 292–299. [Google Scholar] [CrossRef]
  49. Dykes, L.; Rooney, L.W. Phenolic Compounds in Cereal Grains and Their Health Benefits. Cereal Foods World 2007, 52, 105–111. [Google Scholar] [CrossRef]
  50. Schofield, P.; Mbugua, D.M.; Pell, A.N. Analysis of Condensed Tannins: A Review. Anim. Feed Sci. Technol. 2001, 91, 21–40. [Google Scholar] [CrossRef]
  51. Smith, A.H.; Zoetendal, E.; Mackie, R.I. Bacterial Mechanisms to Overcome Inhibitory Effects of Dietary Tannins. Microb. Ecol. 2005, 50, 197–205. [Google Scholar] [CrossRef]
  52. Ghosh, D. Tannins from Foods to Combat Diseases. Int. J. Pharm. Res. Rev. 2015, 4, 40–44. [Google Scholar]
  53. Patra, A.K.; Saxena, J. Exploitation of Dietary Tannins to Improve Rumen Metabolism and Ruminant Nutrition. J. Sci. Food Agric. 2011, 91, 24–37. [Google Scholar] [CrossRef]
  54. Ajeet, S. Isolation, Characterization, and Therapeutic Applications of Natural Bioactive Compounds; IGI Global: Palmdale, PA, USA, 2022; ISBN 978-1-6684-7338-2. [Google Scholar]
  55. Singh, B.; Bhat, T.K.; Sharma, O.P. Biodegradation of Tannic Acid in an in Vitro Ruminal System. Livest. Prod. Sci. 2001, 68, 259–262. [Google Scholar] [CrossRef]
  56. Jones, W.T.; Mangan, J.L. Complexes of the Condensed Tannins of Sainfoin (Onobrychis viciifolia Scop.) with Fraction 1 Leaf Protein and with Submaxillary Mucoprotein, and Their Reversal by Polyethylene Glycol and pH. J. Sci. Food Agric. 1977, 28, 126–136. [Google Scholar] [CrossRef]
  57. Kumar, K.; Chaudhary, L.C.; Kumar, S. Exploitation of Tannins to Modulate Rumen Ecosystem and Ruminants Performance: A Review. Indian J. Anim. Sci 2014, 84, 609–618. [Google Scholar] [CrossRef]
  58. Zhang, J.; Xu, X.; Cao, Z.; Wang, Y.; Yang, H.; Azarfar, A.; Li, S. Effect of Different Tannin Sources on Nutrient Intake, Digestibility, Performance, Nitrogen Utilization, and Blood Parameters in Dairy Cows. Animals 2019, 9, 507. [Google Scholar] [CrossRef]
  59. Aguiar, F.d.S.; Bezerra, L.R.; Cordão, M.A.; Cavalcante, I.T.R.; de Oliveira, J.P.F.; do Nascimento, R.R.; de Souza, B.B.; Oliveira, R.L.; Pereira, E.S.; Filho, J.M.P. Effects of Increasing Levels of Total Tannins on Intake, Digestibility, and Balance of Nitrogen, Water, and Energy in Hair Lambs. Animals 2023, 13, 2497. [Google Scholar] [CrossRef] [PubMed]
  60. Tseu, R.J.; Junior, F.P.; Carvalho, R.F.; Sene, G.A.; Tropaldi, C.B.; Peres, A.H.; Rodrigues, P.H.M. Effect of Tannins and Monensin on Feeding Behaviour, Feed Intake, Digestive Parameters and Microbial Efficiency of Nellore Cows. Ital. J. Anim. Sci. 2020, 19, 262–273. [Google Scholar] [CrossRef]
  61. Costa, E.I.d.S.; Ribiero, C.V.D.M.; Silva, T.M.; Ribeiro, R.D.X.; Vieira, J.F.; Lima, A.G.V.d.O.; Barbosa, A.M.; da Silva Júnior, J.M.; Bezerra, L.R.; Oliveira, R.L. Intake, Nutrient Digestibility, Nitrogen Balance, Serum Metabolites and Growth Performance of Lambs Supplemented with Acacia mearnsii Condensed Tannin Extract. Anim. Feed Sci. Technol. 2021, 272, 114744. [Google Scholar] [CrossRef]
  62. Grainger, C.; Clarke, T.; Auldist, M.J.; Beauchemin, K.A.; McGinn, S.M.; Waghorn, G.C.; Eckard, R.J. Potential Use of Acacia mearnsii Condensed Tannins to Reduce Methane Emissions and Nitrogen Excretion from Grazing Dairy Cows. Can. J. Anim. Sci. 2009, 89, 241–251. [Google Scholar] [CrossRef]
  63. Piñeiro-Vázquez, A.T.; Jiménez-Ferrer, G.; Alayon-Gamboa, J.A.; Chay-Canul, A.J.; Ayala-Burgos, A.J.; Aguilar-Pérez, C.F.; Ku-Vera, J.C. Effects of Quebracho Tannin Extract on Intake, Digestibility, Rumen Fermentation, and Methane Production in Crossbred Heifers Fed Low-Quality Tropical Grass. Trop. Anim. Health Prod. 2018, 50, 29–36. [Google Scholar] [CrossRef]
  64. Min, B.R.; Barry, T.N.; Attwood, G.T.; McNabb, W.C. The Effect of Condensed Tannins on the Nutrition and Health of Ruminants Fed Fresh Temperate Forages: A Review. Anim. Feed Sci. Technol. 2003, 106, 3–19. [Google Scholar] [CrossRef]
  65. Frutos, P.; Raso, M.; Hervás, G.; Mantecón, Á.R.; Pérez, V.; Giráldez, F.J. Is There Any Detrimental Effect When a Chestnut Hydrolysable Tannin Extract Is Included in the Diet of Finishing Lambs? Anim. Res. 2004, 53, 127–136. [Google Scholar] [CrossRef]
  66. Puchala, R.; Min, B.R.; Goetsch, A.L.; Sahlu, T. The Effect of a Condensed Tannin-Containing Forage on Methane Emission by Goats. J. Anim. Sci. 2005, 83, 182–186. [Google Scholar] [CrossRef]
  67. Mueller-Harvey, I. Unravelling the Conundrum of Tannins in Animal Nutrition and Health. J. Sci. Food Agric. 2006, 86, 2010–2037. [Google Scholar] [CrossRef]
  68. Wischer, G.; Greiling, A.M.; Boguhn, J.; Steingass, H.; Schollenberger, M.; Hartung, K.; Rodehutscord, M. Effects of Long-Term Supplementation of Chestnut and Valonea Extracts on Methane Release, Digestibility and Nitrogen Excretion in Sheep. Animal 2014, 8, 938–948. [Google Scholar] [CrossRef] [PubMed]
  69. Carulla, J.E.; Kreuzer, M.; Machmüller, A.; Hess, H.D. Supplementation of Acacia mearnsii Tannins Decreases Methanogenesis and Urinary Nitrogen in Forage-Fed Sheep. Aust. J. Agric. Res. 2005, 56, 961–970. [Google Scholar] [CrossRef]
  70. Dschaak, C.M.; Williams, C.M.; Holt, M.S.; Eun, J.-S.; Young, A.J.; Min, B.R. Effects of Supplementing Condensed Tannin Extract on Intake, Digestion, Ruminal Fermentation, and Milk Production of Lactating Dairy Cows. J. Dairy Sci. 2011, 94, 2508–2519. [Google Scholar] [CrossRef] [PubMed]
  71. Benchaar, C.; McAllister, T.A.; Chouinard, P.Y. Digestion, Ruminal Fermentation, Ciliate Protozoal Populations, and Milk Production from Dairy Cows Fed Cinnamaldehyde, Quebracho Condensed Tannin, or Yucca schidigera Saponin Extracts. J. Dairy Sci. 2008, 91, 4765–4777. [Google Scholar] [CrossRef] [PubMed]
  72. Baah, J.; Ivan, M.; Hristov, A.N.; Koenig, K.M.; Rode, L.M.; McAllister, T.A. Effects of Potential Dietary Antiprotozoal Supplements on Rumen Fermentation and Digestibility in Heifers. Anim. Feed Sci. Technol. 2007, 137, 126–137. [Google Scholar] [CrossRef]
  73. McSweeney, C.S.; Palmer, B.; McNeill, D.M.; Krause, D.O. Microbial Interactions with Tannins: Nutritional Consequences for Ruminants. Anim. Feed Sci. Technol. 2001, 91, 83–93. [Google Scholar] [CrossRef]
  74. Al-Dobaib, S.N. Effect of Different Levels of Quebracho Tannin on Nitrogen Utilization and Growth Performance of Najdi Sheep Fed Alfalfa (Medicago sativa) Hay as a Sole Diet. Anim. Sci. J. 2009, 80, 532–541. [Google Scholar] [CrossRef]
  75. Getachew, G.; Pittroff, W.; Putnam, D.H.; Dandekar, A.; Goyal, S.; DePeters, E.J. The Influence of Addition of Gallic Acid, Tannic Acid, or Quebracho Tannins to Alfalfa Hay on in Vitro Rumen Fermentation and Microbial Protein Synthesis. Anim. Feed Sci. Technol. 2008, 140, 444–461. [Google Scholar] [CrossRef]
  76. Yang, K.; Wei, C.; Zhao, G.; Xu, Z.; Lin, S. Dietary Supplementation of Tannic Acid Modulates Nitrogen Excretion Pattern and Urinary Nitrogenous Constituents of Beef Cattle. Livest. Sci. 2016, 191, 148–152. [Google Scholar] [CrossRef]
  77. Zhou, K.; Bao, Y.; Zhao, G. Effects of Dietary Crude Protein and Tannic Acid on Nitrogen Excretion, Urinary Nitrogenous Composition and Urine Nitrous Oxide Emissions in Beef Cattle. Anim. Physiol. Nutr. 2019, 103, 1675–1683. [Google Scholar] [CrossRef]
  78. de Souza, M.N.; Bayer, C.; Lassalas, M.; Michelon, G.M.; Schaitz, L.H.; Biasiolo, R.; Civiero, M.; Ribeiro-Filho, H.M.N. Effects of Ground Corn and Acacia mearnsii Tannin Extract Supplementation on Nitrogen Excretion and Nitrous Oxide Emissions from Sheep. Livest. Sci. 2021, 246, 104458. [Google Scholar] [CrossRef]
  79. Eckard, R.J.; Grainger, C.; De Klein, C.A.M. Options for the Abatement of Methane and Nitrous Oxide from Ruminant Production: A Review. Livest. Sci. 2010, 130, 47–56. [Google Scholar] [CrossRef]
  80. Bao, Y.; Zhou, K.; Zhao, G. Nitrous Oxide Emissions from the Urine of Beef Cattle as Regulated by Dietary Crude Protein and Gallic Acid. J. Anim. Sci. 2018, 96, 3699–3711. [Google Scholar] [CrossRef]
  81. Alves, T.P.; Dall-Orsoletta, A.C.; Ribeiro-Filho, H.M.N. The Effects of Supplementing Acacia mearnsii Tannin Extract on Dairy Cow Dry Matter Intake, Milk Production, and Methane Emission in a Tropical Pasture. Trop. Anim. Health Prod. 2017, 49, 1663–1668. [Google Scholar] [CrossRef] [PubMed]
  82. Zhang, F.; Li, B.; Ban, Z.; Liang, H.; Li, L.; Zhao, W.; Yan, X. Evaluation of Origanum Oil, Hydrolysable Tannins and Tea Saponin in Mitigating Ruminant Methane: In Vitro and in Vivo Methods. J. Anim. Physiol. Anim. Nutr. 2021, 105, 630–638. [Google Scholar] [CrossRef]
  83. Bhatta, R.; Enishi, O.; Yabumoto, Y.; Nonaka, I.; Takusari, N.; Higuchi, K.; Tajima, K.; Takenaka, A.; Kurihara, M. Methane Reduction and Energy Partitioning in Goats Fed Two Concentrations of Tannin from Mimosa spp. J. Agric. Sci. 2013, 151, 119–128. [Google Scholar] [CrossRef]
  84. Pathak, A.K.; Dutta, N.; Pattanaik, A.K.; Chaturvedi, V.B.; Sharma, K. Effect of Condensed Tannins from Ficus Infectoria and Psidium Guajava Leaf Meal Mixture on Nutrient Metabolism, Methane Emission and Performance of Lambs. Asian-Australas. J. Anim. Sci. 2017, 30, 1702–1710. [Google Scholar] [CrossRef]
  85. Roth, S.; Steingass, H.; Drochner, W.; Pen, A. Wirkungen von Tanninextrakten Auf Die Parameter Der Pansenfermentation in Vitro. In Proceedings of the 10th Conference on Nutrition of Domestic Animals-Adolf Pen Zadravec-Erjavec Days, Radenci, Slovenia, 8–9 November 2001; pp. 64–70. [Google Scholar]
  86. Geerkens, C.H.; Schweiggert, R.M.; Steingass, H.; Boguhn, J.; Rodehutscord, M.; Carle, R. Influence of Apple and Citrus Pectins, Processed Mango Peels, a Phenolic Mango Peel Extract, and Gallic Acid as Potential Feed Supplements on in Vitro Total Gas Production and Rumen Methanogenesis. J. Agric. Food Chem. 2013, 61, 5727–5737. [Google Scholar] [CrossRef] [PubMed]
  87. Tavendale, M.H.; Meagher, L.P.; Pacheco, D.; Walker, N.; Attwood, G.T.; Sivakumaran, S. Methane Production from in Vitro Rumen Incubations with Lotus pedunculatus and Medicago sativa, and Effects of Extractable Condensed Tannin Fractions on Methanogenesis. Anim. Feed Sci. Technol. 2005, 123, 403–419. [Google Scholar] [CrossRef]
  88. Jayanegara, A.; Goel, G.; Makkar, H.P.; Becker, K. Divergence between Purified Hydrolysable and Condensed Tannin Effects on Methane Emission, Rumen Fermentation and Microbial Population in Vitro. Anim. Feed Sci. Technol. 2015, 209, 60–68. [Google Scholar] [CrossRef]
  89. Yang, K.; Wei, C.; Zhao, G.Y.; Xu, Z.W.; Lin, S.X. Effects of Dietary Supplementing Tannic Acid in the Ration of Beef Cattle on Rumen Fermentation, Methane Emission, Microbial Flora and Nutrient Digestibility. J. Anim. Physiol. Anim. Nutr. 2017, 101, 302–310. [Google Scholar] [CrossRef]
  90. Beauchemin, K.A.; McGinn, S.M.; Martinez, T.F.; McAllister, T.A. Use of Condensed Tannin Extract from Quebracho Trees to Reduce Methane Emissions from Cattle. J. Anim. Sci. 2007, 85, 1990–1996. [Google Scholar] [CrossRef]
  91. Patra, A.K.; Saxena, J. Dietary Phytochemicals as Rumen Modifiers: A Review of the Effects on Microbial Populations. Antonie Van Leeuwenhoek 2009, 96, 363–375. [Google Scholar] [CrossRef] [PubMed]
Agriculture 15 02234 g001
Figure 1. Greenhouse gas emissions from livestock farming. Modified based on Gerber et al. [3]. (A) Contributions of different animal species to total CH4 emissions (Mt CO2-eq)2 from livestock. (B) Greenhouse gas emissions from ruminant animals.
Figure 1. Greenhouse gas emissions from livestock farming. Modified based on Gerber et al. [3]. (A) Contributions of different animal species to total CH4 emissions (Mt CO2-eq)2 from livestock. (B) Greenhouse gas emissions from ruminant animals.
Agriculture 15 02234 g001
Agriculture 15 02234 g002
Figure 2. Nitrogen metabolism in ruminants. Modified based on Pérez-Barbería [11]. CP, Crude protein; RDP, Rumen-degradable protein; RUP, Ruminal indigestible protein; MCP, Microbial protein.
Figure 2. Nitrogen metabolism in ruminants. Modified based on Pérez-Barbería [11]. CP, Crude protein; RDP, Rumen-degradable protein; RUP, Ruminal indigestible protein; MCP, Microbial protein.
Agriculture 15 02234 g002
Agriculture 15 02234 g003
Figure 3. N excretion and N2O production in ruminants. Modified based on Schils et al. [23].
Figure 3. N excretion and N2O production in ruminants. Modified based on Schils et al. [23].
Agriculture 15 02234 g003
Agriculture 15 02234 g004
Figure 4. Carbohydrate metabolism and methane production in ruminants. Created in BioRender. Shuo, Z. (2025) https://BioRender.com/w754jy9 (accessed on 22 October 2025).
Figure 4. Carbohydrate metabolism and methane production in ruminants. Created in BioRender. Shuo, Z. (2025) https://BioRender.com/w754jy9 (accessed on 22 October 2025).
Agriculture 15 02234 g004
Agriculture 15 02234 g005
Figure 5. Types of tannins and their basic structures. From Ghosh [52].
Figure 5. Types of tannins and their basic structures. From Ghosh [52].
Agriculture 15 02234 g005
Table 1. Studies of plant tannins that regulate ruminant nutrient digestibility.
Table 1. Studies of plant tannins that regulate ruminant nutrient digestibility.
Types of TanninsSourcesExperimental AnimalsAdditive DosageDigestive EfficiencyReference
CTAcacia mearnsiiDairy cow163 and 326 g/kg DMDry matter intake ↓[62]
CTChestnutHeifers4%Dry matter intake, DM, OM and NDF digestibility ↓[63]
CT–Sheep55 g/kg DMFeed intake and nutrient digestibility ↓[64]
HTChestnutLamb20.8 g/kg DM=[65]
CTLespedeza cuneataDoes17.7%Dry matter intake ↑[66]
CTAcacia mangiumCows3%Nutrient digestibility ↓[58]
CTMimosa tenuiflora hayLamb26.2 and 52.4 g/kg DMNutrient intake and digestibility ↑[59]
CTMimosa tenuiflora hayLamb78.6 g/kg DMNutrient intake and digestibility ↓[59]
CTbark of A. mearnsiiCow0.00, 0.75, 1.50, and 2.25% of DMNutrient digestibility ↓[60]
CTAcacia mearnsiiLamb20, 40, 60, and 80 g/kg DMNutrient digestibility ↓, Nutrient intake ↑[61]
Note: CT, condensed tannin; HT, hydrolyzed tannin; DM, dry matter, ↓, down regulated, ↑, up regulated, –, unreported; =, no effect.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Zhao, X.; Zhang, S.; Zhang, Y. Tannin-Based Strategies for Mitigating Greenhouse Gas Emissions Through Nitrogen and Carbon Metabolism in Ruminants. Agriculture 2025, 15, 2234. https://doi.org/10.3390/agriculture15212234

AMA Style

Zhao X, Zhang S, Zhang Y. Tannin-Based Strategies for Mitigating Greenhouse Gas Emissions Through Nitrogen and Carbon Metabolism in Ruminants. Agriculture. 2025; 15(21):2234. https://doi.org/10.3390/agriculture15212234

Chicago/Turabian Style

Zhao, Xiaoqiang, Shuo Zhang, and Yuanqing Zhang. 2025. "Tannin-Based Strategies for Mitigating Greenhouse Gas Emissions Through Nitrogen and Carbon Metabolism in Ruminants" Agriculture 15, no. 21: 2234. https://doi.org/10.3390/agriculture15212234

APA Style

Zhao, X., Zhang, S., & Zhang, Y. (2025). Tannin-Based Strategies for Mitigating Greenhouse Gas Emissions Through Nitrogen and Carbon Metabolism in Ruminants. Agriculture, 15(21), 2234. https://doi.org/10.3390/agriculture15212234

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop