Search Results (295)

Goats are considered to be the ideal climate-resilient animal species in the tropics. Fewer studies are documented assessing the heat stress response of caprine ruminal microbiota, which can also be a crucial indicator of the resilience and/or adaptability of animals. This study was conducted to comparatively assess the heat stress responses of two indigenous goat breeds, Nandidurga and Bidri, based on changes associated with the rumen fermentation pattern and distribution pattern of rumen microbiota. A total of 24 adult animals were randomly allocated into four groups of six animals each, NC (n = 6; Nandidurga control), NHS (n = 6; Nandidurga heat stress), BC (n = 6; Bidri control) and BHS (n = 6; Bidri heat stress). The animals were reared in climate chambers for a duration of 45 days wherein the NC and BC animals were maintained under thermoneutral temperature while the NHS and BHS animals were subjected to simulated heat stress. Heat stress was observed to significantly reduce the rumen ammonia, extracellular CMCase, intracellular carboxy methyl cellulase (CMCase) and total CMCase both in Nandidurga and Bidri goats. In addition to this, a significant reduction in acetate, propionate and total volatile fatty acids (VFAs) was observed in Nandidurga goats. The V3–V4 16s rRNA sequencing further revealed a significant alteration in the rumen microbiota in heat-stressed Nandidurga and Bidri goats. While both the breeds exhibited nearly similar responses in the rumen microbial abundance levels due to heat stress, breed-specific differences were also observed. Furthermore, the LEFSe analysis revealed a significant alteration in the abundances of microbes at the genus level, which were observed to be relatively greater in Bidri goats than Nandidurga goats. Furthermore, these alterations were predicted to impair the functional pathways, especially pathways associated with metabolism. This study therefore provided an insight into the rumen microbial dynamics in heat-stressed goats. Though both the breeds exhibited excellent resilience to the subjected heat stress, there were relatively less ruminal alterations in Nandidurga goats than in Bidri goats. Full article

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

Feed supplementation strategies are essential for optimizing cattle productivity, and the incorporation of non-conventional feed resources may reduce both production costs and environmental impact. This study evaluated the effects of pelletized protein concentrates (including Acacia farnesiana, A. schaffneri, and Agave duranguensis bagasse) on rumen fermentation parameters, microbial communities, and gas emissions. Fistulated bullocks received the concentrate daily, and ruminal contents were collected and filtered before and after supplementation to assess in vitro gas and methane production, pH, and microbial composition using high-throughput sequencing of 16S rRNA and mcrA amplicons. In addition, in situ degradability was evaluated during and after the supplementation period. Supplementation led to a significant (p < 0.05) reduction in degradability parameters and methane production, along with a marked decrease in the abundance of Methanobrevibacter and an increase in succinate-producing taxa. These effects were attributed to the enhanced levels of non-fiber carbohydrates, hemicellulose, crude protein, and the presence of bioactive secondary metabolites and methanol. Rumen microbiota composition was consistent with previously described core communities, and mcrA-based sequencing proved to be a valuable tool for targeted methanogen detection. Overall, the inclusion of non-conventional ingredients in protein concentrates may improve ruminal fermentation efficiency and contribute to methane mitigation in ruminants, although further in vivo trials on a larger scale are recommended. Full article

Glycerol fatty acid esters (GFAEs) are recognized for their potential to improve lipid metabolism, energy utilization, and gut health due to their excellent emulsifying and antimicrobial properties. The objective of this research was to investigate the effects of dietary GFAE supplementation on production performance, serum biochemical profiles, and rumen fermentation in beef cattle. Thirty crossbred Simmental bulls, averaging 507.42 ± 9.59 kg in body weight, were assigned to three distinct cohorts, with 10 animals in each cohort. The CON cohort was fed a basal diet devoid of GFAE, whereas the treatment cohorts (GFAE1 and GFAE2) received GFAE supplements at concentrations of 0.1% and 0.2% of the dietary dry matter, respectively. Compared with the control group, supplementation with 0.1% GFAE significantly increased the ADG of beef cattle by 12.14% (p < 0.05); compared with the GFAE2 group, ADG was 7.86% higher (p > 0.05). The digestibility of NDF and ADF was significantly enhanced in the GFAE1 group relative to the control group (p < 0.05). Dietary GFAE supplementation significantly elevated rumen acetate, propionate, and total volatile fatty acid concentrations in both the GFAE1 and GFAE2 groups compared to the control group (p < 0.05). In contrast to the control group, there was a notable rise in serum levels of T-AOC, UREA, and TG in both GFAE1 and GFAE2 groups (p < 0.05). Conversely, the concentration of HDL-C was significantly decreased in the GFAE2 group. Additionally, at the phylum level, the abundance of Fibrobacterota was significantly higher in the GFAE1 group than in the control group (p < 0.01). At the genus level, the proportions of Bacteroides and Fibrobacter were significantly higher in the GFAE1 group compared to the control group (p < 0.05). In conclusion, this study demonstrates that the addition of 0.1% GFAE to beef cattle diets significantly enhances the digestibility of ADF and NDF nutrients, increases serum total antioxidant capacity, urea, and triglycerides, optimizes rumen fermentation parameters and microbial community structure, and ultimately improves production performance. As a result of the findings from this research, it is suggested that 0.1% GFAE be incorporated into the diet for beef cattle. Full article

The objective of this study was to evaluate the effect of tyrosine on behavior and ruminal meta-taxonomic profile of Altay sheep. Twelve rams with the lowest behavioral responses to humans and twelve rams with the highest behavioral responses were sorted into calm and nervous groups, respectively. Following the 2 × 2 factorial design, the rams from each group were equally assigned two treatments of a basal diet and a diet with an extra 4 g of tyrosine for 30 d. The temperament trait, growth performance, rumen fermentation parameters, ruminal epithelium antioxidant capacity, and rumen microbial composition were measured at the end of the feeding experiment. The results showed that tyrosine treatment led to a decreased number of crosses in the arena test in nervous sheep (p < 0.05). The tyrosine treatment led to increased antioxidant markers in the rumen epithelium, such as catalase, total antioxidant capacity, and GSH content in rumen epithelial tissues (p < 0.05) in calm and nervous sheep. The total volatile fatty acids and propionic acid content in the rumen were increased by tyrosine treatment in nervous and calm sheep (p < 0.05). The rumen microbial study revealed that the dominant microbial genera were Cryptobacteroides, Prevotella, Limivicinus, Quinella, UBA1711, RUG740, Sachharofermentans, Limomorpha, Soladiphilus, Flexinia, and others in both the tyrosine treatment and temperament groups. A combined effect of treatment and temperament was seen on the abundance of two microbial genera, UBA1711 and RUG740 (p < 0.05). These findings suggest that tyrosine-treated Altay sheep would experience less stress during production, resulting in reduced oxidative stress in the rumen epithelium and improved propionic acid production in the rumen compared with that of basal-diet-treated Altay sheep. Meanwhile, the effect of the dietary tyrosine treatment on ruminal microbial diversity was lower, suggesting lesser degradation of tyrosine by ruminal microbes in Altay sheep. Full article

Optimizing the metabolizable protein level in ruminant diets represents a promising strategy to increase nitrogen use efficiency and mitigate environmental pollution. This study explored the impacts of varying metabolizable protein (MP) levels on amino acid (AA) balance, nitrogen (N) utilization, and the ruminal microbiota in Hu lambs. Fifty-four female Hu lambs of 60 d old, with an average body weight (BW) of 18.7 ± 2.37 kg, were randomly allocated to three dietary MP groups: (1) low MP (LMP, 7.38% of DM), (2) moderate MP (MMP, 8.66% of DM), and (3) high MP (HMP, 9.93% of DM). Three lambs with similar BW within each group were housed together in a single pen, serving as one experimental replicate (n = 6). The feeding trial lasted for 60 days with 10 days for adaptation. The final BW of lambs in the MMP and HMP groups increased (p < 0.05) by 5.64% and 5.26%, respectively, compared to the LMP group. Additionally, lambs fed the MMP diet exhibited an 11.6% higher (p < 0.05) average daily gain than those in the LMP group. Increasing dietary MP levels enhanced (p < 0.05) N intake, urinary N, retained N, and percent N retained, but decreased apparent N digestibility (p < 0.05). Urinary uric acid, total purine derivatives, intestinally absorbable dietary protein, microbial crude protein, intestinally absorbable microbial crude protein, and actual MP supply all increased (p < 0.05) with higher MP values in the diet. The plasma concentrations of arginine, lysine, methionine, phenylalanine, threonine, aspartic acid, proline, total essential AAs, and total nonessential AAs were the lowest (p < 0.05) in the LMP group. In the rumen, elevated MP levels led to a significant increase (p < 0.05) in the ammonia N content. The relative abundances of Candidatus_Saccharimonas, Ruminococcus, and Oscillospira were the lowest (p < 0.05), whereas the relative abundances of Terrisporobacter and the Christensenellaceae_R-7_group were the highest (p < 0.05) in the MMP group. In conclusion, the moderate dietary metabolizable protein level could enhance growth performance, balance the plasma amino acid profiles, and increase nitrogen utilization efficiency in Hu lambs, while also altering the rumen bacterial community by increasing beneficial probiotics like the Christensenellaceae_R-7_group. Full article

Animal feed made from fermented agricultural residues using Lactobacillus sp. and Bacillus sp. has received significant attention. However, interactions between differentially expressed genes (DEGs) in adipose, liver, and muscle tissues and bacteria or fungi in the rumen remain largely unknown. This study determined effects of normal diet feed (NF) and alternative diet feed made by Lactobacillus sp. and Bacillus sp. (AF) on gene expression in major metabolic organs and on microbial populations in the rumen of Bos-Taurus using high-throughput sequencing methods. Rumen bacteria/fungi interaction with DEGs in key metabolic organs was also investigated. According to our findings, 34, 36, and 28 genes were differentially expressed in adipose, liver, and muscle tissues, respectively. Most DEGs were associated with osteoclast differentiation and immune functions. Microbial dynamics analysis showed that the AF diet significantly (p < 0.05) increased Firmicutes but reduced Bacterioidetes abundances. At the genus level, Faecalicatena, Intestinimonas, Lachnoclostridium, Faecalicatena, and Intestinimonas were significantly higher (p < 0.05) in animals fed with the AF diet. Regarding fungal populations, Neocallimastigomycota accounted for 98.2% in the NF diet and 86.88% in the AF diet. AF feeding increased Orpinomyces and Piromyces but decreased Neocallimastix abundances. These findings highlight the potential of fermented feeds to improve metabolic responses and rumen microbial balance, contributing to enhanced animal performance. Full article

Understanding the influence of the sheep breed and roughage source on the composition of rumen bacteria and methanogens is essential for optimizing roughage efficiency. The experiment employed a 2 × 2 factorial design. Twenty-four Dumont and Mongolian sheep (initial body weight of 18.94 ± 1.01 kg) were randomly assigned by breed to two dietary treatment groups (AH: alfalfa hay; CS: corn straw); the experiment lasted 90 days. The results showed that sheep fed alfalfa hay diets had a higher feed intake and weight gain, and Dumont sheep had a higher feed intake than Mongolian sheep (p < 0.05). The diversity and composition of ruminal bacteria and methanogens differed between Dumont and Mongolian sheep fed either AH or CS diets. The taxonomic analysis revealed a distinct clustering pattern based on the roughage source, but not on the breed. When fed a corn straw diet, the bacterial Chao1 index of Dumont sheep increased (p < 0.05), while the diversity and richness of methanogens in Mongolian sheep increased (p < 0.05). Additionally, we have identified unique biomarkers for the rumen bacteria and methanogens of Dumont and Mongolian sheep in response to different roughage sources. The results suggest that the differences in the microbiota of the sheep were associated with the roughage source and breed. The higher growth performance of Dumont sheep might be attributed to the increase in bacterial diversity and the decrease in methanogenic bacteria diversity. Full article

Our previous study has shown that supplementation of 0.50% benzoic acid (BA) increased growth performance, promoted rumen fermentation, and improved the composition and function of rumen microbiota. This research was designed to conduct a deeper exploration of the impacts of dietary supplementation with BA on the apparent digestibility of nutrients and the composition of rectal microbiota in weaned Holstein dairy calves. Sixteen Holstein heifer calves with similar body weights (91.2 ± 0.7 kg) were selected and randomly allocated into two groups, each comprising eight calves. Calves in the control group (CON group) were fed with a basal diet, while those in the benzoic acid group (BA group) were fed with the basal diet supplemented with 0.50% benzoic acid (on a dry matter basis). The experimental period started at 60 days of age and ended at 102 days of age, lasting for a total of 42 days. The calves were weaned at 60 days of age, with a transition period of 7 days. Feed samples were collected every two weeks, fecal samples were collected from 99 to 101 days of age, and blood samples were collected at 102 days of age. The results showed that supplementation with BA did not influence the digestibility of dry matter, crude protein, ether extract, neutral detergent fiber, acid detergent fiber, calcium, and phosphorus between the two groups. Compared with the CON group, BA supplementation tended to decrease the total cholesterol (TC) in the serum of the calves (p = 0.067). Supplementation with BA increased the relative abundances of the two beneficial bacteria, Bifidobacterium and Bifidobacterium pseudolongum (p < 0.05, LDA > 2), but decreased that of the harmful bacterium, Clostridium sensu stricto 1, in the rectum of dairy calves. The microbial functional prediction revealed that the fecal microbial metabolism involved in primary bile acid biosynthesis was higher in the calves from the BA group. In conclusion, the present study demonstrated that adding 0.50% BA to the diet did not influence the apparent nutrient digestibility, but improved rectal microbiota health, which finally promoted the growth performance in weaned Holstein dairy calves. Full article

The objective of this study is to investigate the degradation characteristics of oat grass in the rumen of Mindong goats and changes in microbial community attached to the grass surface. Four healthy male goats, aged 14 months, with permanent rumen fistula, in eastern Fujian, were selected as experimental animals. The rumen degradation rate of oat grass was measured at 4, 12, 24, 36, 48, and 72 h using the nylon bag method. Surface physical structure changes in oat grass were observed using scanning electron microscopy (SEM), cellulase activity was measured, and bacterial composition was analyzed using high-throughput 16S rRNA gene sequencing technology. The findings of this study indicate that oat grass had effective degradation rates (ED) of 47.94%, 48.69%, 38.41%, and 30.24% for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and acidic detergent fiber (ADF), respectively. The SEM was used to investigate the degradation process of oat grass in the rumen. After 24 h, extensive degradation of non-lignified tissue was observed, resulting in the formation of cavities. At 36 h, significant shedding was observed, and by 72 h, only the epidermis and thick-walled tissue, which exhibited resistance to degradation, remained intact. Surface-attached microorganisms produced β-GC, EG, CBH, and NEX enzymes. The activity of these enzymes exhibited a significant increase between 4 and 12 h and showed a positive correlation with the degradation rate of nutrients. However, the extent of correlation varied. Prevotella and Treponema were identified as key genera involved in the degradation of roughage, with their abundance decreasing over time. Principle Coordinate Analysis (PCOA) revealed no significant differences in the rumen microbial structure across different time points. However, Non-Metric Multidimensional Scaling (NMDS) indicated a discernible diversity order among the samples. According to the Spearman correlation coefficient test, Ruminococcus, Fibrobacter, and Saccharoferments exhibited the closest relationship with nutrient degradation rate and surface enzyme activity, displaying a significant positive correlation. In summary, this study delineates a time-resolved correlative framework linking microbial succession to structural and enzymatic dynamics during oat grass degradation. Full article

The rumen and intestinal microbiota play a pivotal role in the digestion and absorption processes of ruminants. Elucidating the mechanisms by which gastrointestinal microbiota influence the feed conversion ratio (FCR) in ruminants is significantly important for enhancing feed utilization efficiency in these animals. In this study, RT-qPCR, 16S rRNA sequencing, and metabolomic techniques were systematically employed to compare the microbial community structures in the rumen, cecum, and rectum, as well as the differences in rumen metabolites between high- and low-FCR Tan sheep. The results showed that, compared to the HFCR group of Tan sheep, the LFCR group exhibited a significant reduction in unclassified_f__Selenomonadaceae, Blvii28_wastewater-sludge_group, and Papillibacter in the rumen; a significant increase in Lachnospiraceae_AC2044_group and Sanguibacteroides; a significant reduction in unclassified_f__Peptostreptococcaceae, Clostridium_sensu_stricto_1, and Parasutterella in the cecum; a significant increase in norank_f__Bacteroidales_UCG-001; and a significant reduction in norank_f__Muribaculaceae, Blautia, and Turicibacter in the rectum. There is a significant positive correlation between Parasutterella in the cecum and three microorganisms, including unclassified_f__Selenomonadaceae, in the rumen. Additionally, Blvii28_wastewater-sludge_group was positively correlated with Lactobacillus. Furthermore, unclassified_f__Selenomonadaceae in the rumen was positively correlated with Turicibacter, unclassified_f__Peptostreptococcaceae, and Breznakia in the rectum. Blvii28_wastewater-sludge_group also showed positive correlations with Blautia, norank_f__Muribaculaceae, and Clostridium_sensu_stricto_1, while Papillibacter was positively correlated with Faecalitalea. The metabolomic results indicated that, compared to the HFCR group, 261 differential metabolites, including Phenylacetylglutamine and Populin, in the rumen of Tan sheep in the LFCR group were significantly downregulated, whereas 36 differential metabolites, including Glycyl-L-tyrosine, were significantly upregulated. Furthermore, the rumen microbe unclassified_f__Selenomonadaceae exhibited positive correlations with significantly differential metabolites such as L-tryptophan, Etiocholanolone glucuronide, N-acetyl-O-demethylpuromycin, and 6-deoxyerythronolide B. Blvii28_wastewater-sludge_group and Papillibacter also exhibited positive correlations with Icilin. High and low FCRs in the rumen of Tan sheep were investigated, especially in relation to unclassified_f__Selenomonadaceae, Blvii28_wastewater-sludge_group, and Papillibacter. Correlations can be seen with microorganisms such as Parasutatella and Lactobacillus in the cecum; Turicibacter, norank_f__Bacteroideales_UCG-001, and Blautia in the rectum; and metabolites such as L-tryptophan, Etiocholanolone glucuronide, and N-acetyl-O-demethylpuromycin. This reveals the role of microorganisms in the digestion and absorption of Tan sheep feed, thus providing a preliminary basis for further research on the microbial regulation of ruminant animal feed utilization and a theoretical basis for improving Tan sheep feed utilization efficiency. Full article

Rumen microbiota and metabolites play important roles in energy metabolism and immune regulation in the host. However, the underlying mechanisms of their interaction with the host to regulate yak plateau adaptation remain unknown. In this study, the effects of altitude on the rumen microbiome, metabolome, and fermentation parameters of yaks were analyzed. The fiber content of pasture grasses increased with altitude, while crude protein content was significantly higher at an altitude of 2800 m (T2800) compared to an altitude of 4500 m (T4500) (p < 0.05). The acetic acid, propionic acid, and volatile fatty acids of yaks in the T4500 group were significantly higher than in the T2800 group (p < 0.05). Simpson’s index of rumen microorganisms in the T4500 group of yaks was significantly higher than in T2800 and T3500 yaks. The relative abundance of Rikenellaceae_RC9_gut_group and Succiniclasticum was significantly higher in T4500 than in T2800, while Prevotella and Streptococcus were more abundant in T2800 than in T4500. Rumen metabolomics analyses revealed that yak rumen metabolites at different altitudes were influenced by forage and altitude, mainly affecting energy metabolism and fatty acid biosynthesis (such as purine and glycerophospholipid metabolism). In summary, altitude may influence rumen microbes and metabolites through pasture nutrient composition. Full article

The rumen microbiome impacts beef cattle feed efficiency, a key economic factor in production systems. This study investigated the rumen microbiome of Charolais bulls with divergent residual feed intake-expected progeny difference (RFI-EPD) values to identify microbial taxa associated with feed efficiency. Forty Charolais bulls were evaluated for feed intake and growth over 60 days, and RFI values were determined. The 10 most efficient (NegRFI) and 10 least efficient (PosRFI) bulls were selected for microbiome analysis. Rumen fluid samples were collected and analyzed via 16S rRNA gene sequencing. Microbial analysis revealed no significant differences in alpha or beta diversity between groups, but differential abundance analysis identified 20 operational taxonomic units (OTUs) as more prevalent in NegRFI bulls, while 15 OTUs were more abundant in PosRFI bulls. Two OTUs from the key genus Prevotella showed different relative abundances in the two RFI-EPD groups. NegRFI bulls had a higher relative abundance of Prevotella OTU 109358, while PosRFI bulls had more Prevotella OTU 626329. Additionally, OTUs from Ruminococcus, a genus involved in fiber degradation and volatile fatty acid (VFA) production, were more abundant in NegRFI bulls. In contrast, PosRFI bulls had a higher abundance of OTUs from Oscillospira and F16, both linked to butyrate production. The results of this study support the need for further exploration into the role of microbial taxa associated with feed efficiency. A deeper understanding of the functional profile of the microbiota could aid in the development of microbiome-informed strategies to enhance nutrient utilization and performance in beef cattle. Full article

This study aimed to evaluate the effects of studying the effects of the alkali metal ion complexes (AMIC) on the rumen of lambs. Eighteen 3-month-old male Hu lambs (30 ± 2.5 kg) were randomly assigned to three groups (n = 6). Dietary treatments were: control group (CG, base diet), group C1 (base diet + 0.15% AMIC), and group C2 (base diet + 0.30% AMIC). After 60 days of feeding, samples were collected for analysis. Compared with CG, rumen weight significantly increased in both C1 and C2 (p < 0.05). In C2, average daily gain (ADG), bacterial crude protein (BCP), propionic acid concentration, and rumen papillary length were significantly higher than in CG (p < 0.05). Rumen microbiota analysis showed that AMIC supplementation changed the microbial community composition, increasing the relative abundance of fiber-degrading bacteria (e.g., Prevotellaceae_UCG-001) and decreasing pathogenic Proteobacteria. In particular, rumen papillary length positively correlated with Unclassified Oscillospiraceae, Candidatus Saccharimonas, and Unclassified Clostridia vadinBB60 group. Metabolomic analysis revealed that quercetin 3-O-glucuronide levels increased in a dose-dependent manner with higher AMIC. This metabolite positively correlated with Prevotellaceae_UCG-001 abundance and ADG. At 0.30% AMIC, phospholipids PC(18:0/18:4(6Z,9Z,12Z,15Z)) and PE(18:0/16:1(9Z)) were significantly upregulated, and both positively correlated with Candidatus Saccharimonas, Unclassified Clostridia vadinBB60 group, and papillary morphology. In summary, AMIC supplementation affected metabolism by modulating the rumen microbiota, thereby promoting energy absorption and growth. The 0.30% AMIC inclusion significantly enhanced rumen papilla growth, increased the absorption area, promoted propionic acid production, reduced the acetic acid to propionic acid ratio, and ultimately improved the growth rate of Hu lambs. Thus, adding 0.30% AMIC was associated with improved growth performance. Full article

Rumen microbiota is crucial for cellulose degradation and nutrient metabolism in ruminants. Different feeding systems like grazing and housed feeding can significantly impact it. Mongolian cattle show unique cellulose degradation ability, but functional changes under different feeding conditions are unclear. This study aims to investigate the effects of grazing and housed feeding on rumen microbiota, cellulose degradation, and metabolism in Mongolian cattle. In a 90-day trial, 12 female Mongolian cattle were divided into grazing (F group) and housed feeding (S group). Rumen samples were collected to analyze fermentation parameters, enzyme activities, microbiomes, and metabolomes. The F group had higher acetate, cellulase, xylanase, and β-glucosidase activities (p < 0.05). Bacteroidota and Prevotella were more abundant (p < 0.05), while Firmicutes and Ruminococcus were less abundant (p < 0.05) in the F group. Carbohydrate metabolic pathways and CAZymes (GH2, GH10) were upregulated in the F group, while the S group had enriched purine metabolic pathways and CAZyme (GH31). A total of 64 differential metabolites were found, with subaphylline upregulated in the F group and L-arogenate in the S group (p < 0.05). Grazing increased cellulose degradation and subaphylline production in Mongolian cattle, while housed feeding improved starch utilization efficiency and fat synthesis. These findings provide a basis for optimizing feeding strategies and improving fibrous feed resource utilization in Mongolian cattle. Full article