Fecal bacterial community of finishing beef steers fed ruminally protected and non-protected active dried yeast

Abstract Our previous study suggested that supplementation of high-grain diets with ruminally protected and non-protected active dried yeast (ADY) may potentially reduce manure pathogen excretion by feedlot cattle. We hypothesized that feeding ruminally protected ADY might change the fecal bacterial community of finishing cattle. The objective of this study was to investigate the effects of feeding ruminally protected and non-protected ADY to finishing beef steers on their fecal bacterial community. Fresh fecal samples were collected on day 56 from 50 steers fed one of five treatments: 1) control (no monensin, tylosin, or ADY), 2) antibiotics (ANT, 330 mg monensin + 110 mg tylosin·steer−1d−1), 3) ADY (1.5 g·steer−1d−1), 4) encapsulated ADY (EDY; 3 g·steer−1d−1), and 5) a mixture of ADY and EDY (MDY; 1.5 g ADY + 3 g EDY·steer−1d−1). Bacterial DNA was extracted from fecal samples and sequenced using a MiSeq high-throughput sequencing platform. A total number of 2,128,772 high-quality V4 16S rRNA sequences from 50 fecal samples were analyzed, and 1,424 operational taxonomic units (OTU) were detected based on 97% nucleotide sequence identity among reads, with 769 OTU shared across the five treatments. Alpha diversity indices, including species observed, Chao estimate, abundance-based coverage estimator, Shannon, Simpson, and coverage, did not differ among treatments, and principal coordinate analysis revealed a high similarity among treatments without independent distribution. Bacteroidetes and Firmicutes were dominant phyla in the fecal bacterial community for all treatments, with a tendency (P < 0.10) for greater relative abundance of Bacteroidetes but lesser Firmicutes with ANT, EDY, and MDY compared with control steers. Prevotella was the dominant genus in all treatments and steers supplemented with ANT, EDY, and MDY had greater (P < 0.05) relative abundance of Prevotella than control steers, but lesser (P < 0.03) relative abundance of Oscillospira. No differences between ADY and control were observed for the aforementioned variables. Fecal starch contents were not different among treatments, but the relative abundance of Bacteroidetes, as well as Prevotella at genera level, tended (P < 0.06) to be positively correlated to fecal starch content. We conclude that supplementing ruminally protected or non-protected ADY or ANT had no effect on diversity and richness of fecal bacteria of finishing beef cattle, whereas feeding protected ADY or ANT to finishing beef steers altered the dominant fecal bacteria at phylum and genus levels. Therefore, supplementation of ruminally protected ADY may potentially improve intestinal health by stimulating the relative abundance of Prevotella.

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PSXII-24 Effects of supplementing ruminally protected and non-protected active dried yeast on fecal bacterial community of finishing beef steers

Journal of Animal Science ◽

10.1093/jas/skz258.844 ◽

2019 ◽

Vol 97 (Supplement_3) ◽

pp. 425-426

Author(s):

Tao Ran ◽

Peixin Jiao ◽

Ousama AlZahal ◽

Xiaolai Xie ◽

Karen A Beauchemin ◽

...

Keyword(s):

Bacterial Community ◽

Bacterial Diversity ◽

Relative Abundance ◽

Alpha Diversity ◽

Diversity Indices ◽

Fecal Bacteria ◽

Beef Steers ◽

Fecal Bacterial Community ◽

Barley Silage ◽

And Control

Abstract The objective of this study was to evaluate the effects of supplementing ruminally protected and non-protected active dried yeast (ADY; AB Vista, UK) on fecal bacterial diversity of finishing beef steers. Seventy-five Angus steers (initial BW 448 kg) were randomly assigned to one of five treatments: control, antibiotics (ANT, 330 mg monensin + 110 mg tylosin/d), ADY (1.5 g/d), encapsulated ADY (EDY; 3 g/d), and mixture of ADY and EDY (MDY). The ADY (1.7×1010 cfu/g) was encapsulated with equal amount of ADY and capsule material. Steers were fed a diet containing 10% barley silage and 90% barley concentrate (DM basis), ANT, ADY, EDY and MDY were top-dressed at feeding. Fecal samples were rectally collected from 10 steers of each treatment on d 56 to determine fecal bacterial diversity using high throughput MiSeq sequencing. Alpha diversity indices were not different among treatments. Principal coordinate analysis revealed that samples were not clustered by treatments. Bacteroidetes and Firmicutes were dominant phyla in the fecal bacterial community for all treatments, with a tendency (P < 0.10) of ANT, EDY and MDY to have greater relative abundance of Bacteroidetes (averaged 51.3 vs 46.8%) but lesser Firmicutes (averaged 39.5 vs 47.9%) than control steers. About 50 to 61% of sequences remained unclassified and identified 32 genus, with Prevotella ranging from 15.8 to 25.5% as the dominant genus in all treatments. Notably, steers with ANT, EDY, MDY vs. control had greater (P < 0.05) relative abundance of Prevotella (averaged 23.5 vs 16.8%) but lesser (P < 0.03) Oscillospira (averaged 1.7 vs 2.8%). No differences between ADY and control were observed for aforementioned variables. The results indicate that supplementing ruminally protected or non-protected ADY have limited effect on diversity of fecal bacteria, whereas feeding protected ADY and ANT to finishing beef steers altered dominant fecal bacteria at phylum and genus level.

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PSVI-2 Effects of dietary supplementation of a Saccharomyces cerevisiae-based direct-fed microbial product on plasma carbonyl-metabolome and fecal bacterial community of beef steers

Journal of Animal Science ◽

10.1093/jas/skaa278.749 ◽

2020 ◽

Vol 98 (Supplement_4) ◽

pp. 430-430

Author(s):

Ibukun M Ogunade ◽

Devan M Compart ◽

Andres A Pech-Cervantes

Keyword(s):

Saccharomyces Cerevisiae ◽

Bacterial Community ◽

Relative Abundance ◽

Isotope Labeling ◽

Dietary Supplementation ◽

Basal Diet ◽

Plasma Metabolites ◽

Rrna Gene ◽

Beef Steers ◽

Fecal Bacterial Community

Abstract We examined the effects of dietary supplementation of a Saccharomyces cerevisiae-based direct-fed microbial on plasma carbonyl-metabolome and fecal bacterial community of beef steers during a 42-d receiving period. Forty newly-weaned beef steers were used in this study. The steers were stratified by BW and randomly assigned to receive a basal diet with no additive (CON; n = 20) or a basal diet supplemented with 19 g of CommenceTM (PROB; n = 20). CommenceTM (PMI, Arden Hills, MN) contains a blend of 6.2 × 1011 cfu/g of S. cerevisiae, 3.5 × 1010 cfu/g of a mixture of Enterococcus lactis, Bacillus subtilis, Enterococcus faecium, and L. casei. On d 0 and 40, rectal fecal samples were collected for bacterial community analysis via sequencing of the V3-V4 region of 16S rRNA gene. On d 42, blood was collected for analysis of carbonyl-containing metabolites in plasma using a chemical isotope labeling/liquid chromatography mass spectrometry-based untargeted metabolomics. The data were analyzed using the GLIMMIX procedure of SAS with treatment as a fixed effect) and (random effect). A total number of 812 unique plasma metabolites were detected. Up to 305 metabolites [fold change (FC) ≥ 1.5, FDR ≤ 0.01] including glucose, hippuric acid, glycoaldehyde, and 5-hydroxykynurenamine were increased by PROB supplementation, whereas 199 metabolites (FC ≤ 0.63, FDR ≤ 0.01) including acetoacetate were reduced. Correlation analysis showed that plasma concentrations of 5-oxopentanoate, 2-aceto-2-hydroxybutanoate, and 3-methyl-2-oxopentanoic acid were positively correlated (P ≤ 0.10) with average daily gain. Supplemental PROB increased (P ≤ 0.05) the relative abundance of Prevotellaceae, Megasphaera, Dorea, Acetitomaculum, and Blautia. In contrast, the relative abundance of Elusimicrobium, Moheibacter, and Stenotrophomonas were reduced (P ≤ 0.05). This study demonstrated that PROB altered the plasma carbonyl-metabolome and fecal bacterial community of the beef steers.

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The Liquid Diet Composition Affects the Fecal Bacterial Community in Pre-weaning Dairy Calves

Frontiers in Animal Science ◽

10.3389/fanim.2021.649468 ◽

2021 ◽

Vol 2 ◽

Author(s):

Gercino Ferreira Virgínio Júnior ◽

Marina Gavanski Coelho ◽

Ariany Faria de Toledo ◽

Horácio Montenegro ◽

Luiz Lehmann Coutinho ◽

...

Keyword(s):

Bacterial Community ◽

Diet Composition ◽

Illumina Miseq ◽

Liquid Diet ◽

Free Access ◽

Rrna Gene ◽

Fecal Samples ◽

Bacterial Phyla ◽

Whole Milk ◽

Fecal Bacterial Community

Feeding a liquid diet to the newborn calf has considerable implications for developing the intestinal microbiota, as its composition can shift the population to a highly adapted microbiota. The present work evaluated 15 Holstein calves individually housed and fed one of the three liquid diets: I – whole milk (n = 5), II – milk replacer (22.9% CP; 16.2% fat; diluted to 14% solids; n = 5) and III – acidified whole milk to pH 4.5 with formic acid (n = 5). All animals received 6 L of liquid diet, divided into two meals, being weaned at week 8 of life. Calves also had free access to water and starter concentrate. After weaning, all calves were grouped on pasture, fed with starter concentrate, and hay ad libitum. The fecal samples were collected at birth (0) and at weeks 1, 2, 4, 8, and 10 of life. The bacterial community was assessed the through sequencing of the V3-V4 region of the 16S rRNA gene on the Illumina MiSeq platform and analyzed using the DADA2 pipeline. Diversity indices were not affected by the liquid diets, but by age (P < 0.001) with weeks 1 and 2 presenting lower diversity, evenness, and richness values. The bacterial community structure was affected by diet, age, and the interaction of these factors (P < 0.01). Twenty-eight bacterial phyla were identified in the fecal samples, and the most predominant phyla were Firmicutes (42.35%), Bacteroidota (39.37%), and Proteobacteria (9.36%). The most prevalent genera were Bacteroides (10.71%), Lactobacillus (8.11%), Alloprevotella (6.20%). Over the weeks, different genera were predominant, with some showing significant differences among treatments. The different liquid diets altered the fecal bacterial community during the pre-weaning period. However, differences in the initial colonization due to different liquid diets are alleviated after weaning, when animals share a common environment and solid diet composition.

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The leaf bacterial microbiota of female and male kiwifruit plants in distinct seasons: assessing the impact of Pseudomonas syringae pv. actinidiae

Phytobiomes Journal ◽

10.1094/pbiomes-09-20-0070-r ◽

2021 ◽

Author(s):

Aitana Ares ◽

Joana Pereira ◽

Eva Garcia ◽

Joana Costa ◽

Igor Tiago

Keyword(s):

Bacterial Community ◽

Pseudomonas Syringae ◽

Relative Abundance ◽

Bacterial Communities ◽

Defense Mechanisms ◽

Abiotic Factors ◽

Illumina Miseq ◽

Rrna Gene ◽

Sequencing Platform ◽

The Impact

The pandemic Pseudomonas syringae pv. actinidiae (Psa) has been compromising the production of the kiwifruit industry in major producing countries. Abiotic factors and plant gender are known to influence the disease outcome. To better understand their impact, we have determined the diversity of the leafs bacterial communities using the V5-V6 region of the 16S rRNA gene amplicon on the Illumina MiSeq sequencing platform. Healthy and diseased female and male kiwifruit plants were analyzed in two consecutive seasons: spring and autumn. This work describes whether the season, plant gender and the presence of Psa can affect the leaves bacterial community. Fifty bacterial operational taxonomic units (OTUs) were identified and assigned to five phyla distributed by 14 different families and 23 genera. The leaves of healthy female and male kiwi plants share most of the identified bacterial populations, that undergoes major seasonal changes. In both cases a substantial increase of the relative abundance of genus Methylobacterium is observed in autumn. The presence of Psa induced profound changes on leaves bacterial communities structure translated into a reduction in the relative abundance of previously dominant genera that had been found in healthy plants, namely Hymenobacter, Sphingomonas and Massilia. The impact of Psa was less pronounced in the bacterial community structure of male plants in both seasons. Some of the naturally occurring genera have the potential to act as an antagonist or as enhancers of the defense mechanisms paving the way for environmentally friendly and sustainable disease control.

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Bacterial communities in paddy soil and ditch sediment under rice-crab co-culture system

AMB Express ◽

10.1186/s13568-021-01323-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Xu Jiang ◽

Hui Ma ◽

Qing-lei Zhao ◽

Jun Yang ◽

Cai-yun Xin ◽

...

Keyword(s):

Community Structure ◽

Bacterial Community ◽

Relative Abundance ◽

Paddy Soil ◽

Bacterial Communities ◽

Bacterial Community Structure ◽

High Throughput Sequencing ◽

Available Phosphorus ◽

Uncultured Bacterium ◽

Ditch Sediment

AbstractAs an important form of sustainable agriculture, rice-crab (Eriocheir sinensis) co-culture is rapid developing worldwide. However, the knowledge on the bacterial communities of the different components of the system is limited. In this study, we investigated the bacterial community structure in paddy soil and ditch sediment by using high-throughput sequencing technology. The results showed that compared with the ditch sediment, the content of NH4+-N in paddy soil decreased by 62.31%, and the content of AP (available phosphorus) increased by 172.02% (P < 0.05). The most abundant phyla in paddy soil and ditch sediment were Proteobacteria, Bacteroidetes and Chloroflexi, whose relative abundance was above 65%. Among the dominant genera, the relative abundance of an uncultured bacterium genus of Saprospiraceae and an uncultured bacterium genus of Lentimicrobiaceae in paddy soil was significantly lower than ditch sediment (P < 0.05). Alpha diversity indicated that the bacterial diversity of paddy soil and ditch sediment was similar. The bacterial community structure was affected by the relative abundance of bacteria, not the species of bacteria. Redundancy analysis (RDA) showed that the bacterial communities in paddy soil and ditch sediment were correlated with physicochemical properties. Our findings showed that the bacterial community structure was distinct in paddy soil and ditch sediment under rice-crab co-culture probably due to their different management patterns. These results can provide theoretical support for improving rice-crab co-culture technology.

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Assessing soil bacterial community and dynamics by integrated high-throughput absolute abundance quantification

PeerJ ◽

10.7717/peerj.4514 ◽

2018 ◽

Vol 6 ◽

pp. e4514 ◽

Cited By ~ 25

Author(s):

Jun Lou ◽

Li Yang ◽

Haizhen Wang ◽

Laosheng Wu ◽

Jianming Xu

Keyword(s):

Bacterial Community ◽

High Throughput ◽

Relative Abundance ◽

High Throughput Sequencing ◽

Laboratory Strain ◽

Soil Bacterial Community ◽

Absolute Abundance ◽

Internal Reference ◽

Biodegradation Study ◽

Soil Bacterial

Microbial ecological studies have been remarkably promoted by the high-throughput sequencing approach with explosive information of taxonomy and relative abundance. However, relative abundance does not reflect the quantity of the microbial community and the inter-sample differences among taxa. In this study, we refined and applied an integrated high-throughput absolute abundance quantification (iHAAQ) method to better characterize soil quantitative bacterial community through combining the relative abundance (by high-throughput sequencing) and total bacterial quantities (by quantitative PCR). The proposed iHAAQ method was validated by an internal reference strain EDL933 and a laboratory strain WG5. Application of the iHAAQ method to a soil phenanthrene biodegradation study showed that for some bacterial taxa, the changes of relative and absolute abundances were coincident, while for others the changes were opposite. With the addition of a microbial activity inhibitor (NaN3), the absolute abundances of soil bacterial taxa, including several dominant genera of Bacillus, Flavobacterium, and Paenibacillus, decreased significantly, but their relative abundances increased after 28 days of incubation. We conclude that the iHAAQ method can offer more comprehensive information to reflect the dynamics of soil bacterial community with both relative and absolute abundances than the relative abundance from high-throughput sequencing alone.

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Analyzing bacterial community in pit mud of Yibin Baijiu in China using high throughput sequencing

PeerJ ◽

10.7717/peerj.9122 ◽

2020 ◽

Vol 8 ◽

pp. e9122

Author(s):

Li Chen ◽

Yuzhu Li ◽

Lei Jin ◽

Li He ◽

Xiaolin Ao ◽

...

Keyword(s):

Bacterial Community ◽

High Throughput ◽

Relative Abundance ◽

High Throughput Sequencing ◽

Middle Layer ◽

Ammonia Nitrogen ◽

Western China ◽

Rrna Gene ◽

Linear Discriminant ◽

Pit Mud

“Yibin Baijiu” (YB) is a special Chinese strong-aroma Baijiu (CSAB) that originated in Yibin, a city in western China. YB is fermented in cellars lined with pit mud (PM), the microbiota in which may affect YB quality. In this study, high throughput sequencing of the 16S rRNA gene was used to demonstrate the bacterial community structure and diversity in PM of YB. In addition, the physicochemical characteristics of PM were also analyzed, including moisture content, pH, and available phosphorous, ammonia nitrogen, and humic acid levels. Results showed that Firmicutes was the dominant phylum in all PM samples with abundance > 70.0%, followed by Euryarchaeota (11.3%), Bacteroidetes (6.5%), Synergistetes (3.0%), Actinobacteria (1.4%), and Proteobacteria (1.2%). Furthermore, 14 different genera with average relative abundance of > 1% were detected. The Chao1 and Shannon indexes did not vary significantly between the sub-layer and middle-layer PM (P > 0.05). However, Linear discriminant analysis Effect Size (LEfSe) analysis showed that the relative abundance of Lactobacillus in the sub-layer PM was significantly higher than in middle-layer PM. pH differed significantly (P < 0.05) between the two groups. Canonical correspondence analysis revealed that bacterial community in PM correlated significantly with available phosphorous content and pH. Our study provides basic data for further elucidating the diversity of microbiota in the PM of YB and the potential mechanism of Baijiu production.

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Comparative effects of two multispecies direct-fed microbial products on energy status, nutrient digestibility, and ruminal fermentation, bacterial community, and metabolome of beef steers

Journal of Animal Science ◽

10.1093/jas/skaa201 ◽

2020 ◽

Vol 98 (9) ◽

Author(s):

Ibukun M Ogunade ◽

Megan McCoun ◽

Modoluwamu D Idowu ◽

Sunday O Peters

Keyword(s):

Bacterial Community ◽

Relative Abundance ◽

Plasma Glucose ◽

Basal Diet ◽

Nutrient Digestibility ◽

Neutral Detergent Fiber ◽

Beef Steers ◽

Ruminal Fermentation ◽

Energy Status ◽

Fermentation Products

Abstract We examined the effects of two direct-fed microbials (DFM) containing multiple microbial species and their fermentation products on energy status, nutrient digestibility, and ruminal fermentation, bacterial community, and metabolome of beef steers. Nine ruminally cannulated Holstein steers (mean ± SD body weight: 243 ± 12.4 kg) were assigned to three treatments arranged in a triplicated 3 × 3 Latin square design with three 21-d periods. Dietary treatments were 1) control (CON; basal diet), 2) Commence (PROB; basal diet plus 19 g/d of Commence), and 3) RX3 (SYNB; basal diet plus 28 g/d of RX3). Commence and RX3 are both multispecies DFM products. From day 16 to 20 of each period, feed and fecal samples were collected daily to determine the apparent total tract digestibilities of nutrients using indigestible neutral detergent fiber method. On day 21 of each period, blood samples were collected for analysis of plasma glucose and nonesterified fatty acid. Ruminal contents were collected at approximately 1, 3, 6, 9, 12, and 18 h after feeding on day 21 for analysis of volatile fatty acids (VFA), lactate, ammonia-N concentrations, bacterial community, and metabolome profile. Total tract digestibilities of nutrients did not differ (P > 0.05) among treatments. Compared with CON, steers fed either supplemental PROB or SYNB had greater (P = 0.04) plasma glucose concentrations. Compared with CON, total ruminal VFA, propionate, isovalerate, and valerate concentrations increased (P ≤ 0.05) or tended to increase (P ≤ 0.10) with either supplemental PROB or SYNB, but were not different (P > 0.05) between PROB and SYNB. Compared with CON, PROB reduced (P ≤ 0.05) the relative abundance of Prevotella 1 and Prevotellaceae UCG-001 but increased (P ≤ 0.05) the relative abundance of Rikenellaceae RC9, Succinivibrionaceae UCG-001, Succiniclasticum, and Ruminococcaceae UCG-002. Supplemental SYNB decreased (P ≤ 0.05) the relative abundance of Prevotella 1 and Prevotellaceae UCG-001 but increased (P ≤ 0.05) the relative abundance of Prevotella 7, Succinivibrio, Succiniclasticum, and Ruminococcaceae UCG-014. Compared with CON, metabolome analysis revealed that some amino acids were increased (P ≤ 0.05) in steers fed PROB. This study demonstrated that, compared with CON, supplementation of either PROB or SYNB altered the ruminal bacterial community and metabolome differently; however, their effects on the ruminal VFA profile and energy status of the steers were not different from each other.

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PSII-6 Comparative effects of two multi-species direct-fed microbial products on rumen fermentation, bacterial community and metabolome of beef steers

Journal of Animal Science ◽

10.1093/jas/skaa278.699 ◽

2020 ◽

Vol 98 (Supplement_4) ◽

pp. 398-398

Author(s):

Ibukun M Ogunade ◽

Devan M Compart ◽

Andres A Pech-Cervantes

Keyword(s):

Bacillus Subtilis ◽

Bacterial Community ◽

Relative Abundance ◽

Isotope Labeling ◽

Latin Square ◽

Basal Diet ◽

Beef Steers ◽

Ruminal Fermentation ◽

Metabolome Analysis ◽

Fermentation Products

Abstract We examined the effects of two direct-fed microbials (DFM) containing multiple microbial species and their fermentation products on ruminal fermentation, bacterial community and metabolome of beef steers. Nine rumen-cannulated Holstein steers were assigned to 3 treatments arranged in a 3 × 3 Latin square design with three 21-d periods. Dietary treatments were (1) CON (basal diet without additive), (2) PROB (basal diet plus 19 g/d of Commence), and (3) SYNB (basal diet plus 28 g/d of RX3). Commence is a blend of active S. cerevisiae, Enterococcus lactis, Bacillus subtilis, Enterococcus faecium, and L. casei, and their fermentation products. RX3 is a blend of active S. cerevisiae and the fermentation products of S. cerevisiae, Enterococcus lactis, Bacillus licheniformis, and Bacillus subtilis. Daily dry matter intake was calculated. On d 21 of each period, ruminal contents were sampled at 3, 6, 12, and 18 h after feeding for analysis of VFA, bacterial community via 16S rRNA sequencing, and metabolome via chemical isotope labeling liquid chromatography mass spectrometry. There was no effect on DMI. Compared to CON, supplementation of either PROB or SYNB increased or tended to increase (P ≤ 0.10) total VFA, propionate, and valerate concentrations. Compared to CON, PROB reduced (P ≤ 0.05) the relative abundance of Prevotella 1 and Prevotellaceae UCG-001, but increased those of Rikenellaceae RC9, Succinivibrionaceae UCG-001, Succiniclasticum, Ruminococcaceae UCG-014, and Ruminococcaceae UCG-002, whereas SYNB decreased (P ≤ 0.05) the relative abundance of Prevotella 1 and Prevotellaceae UCG-001, and increased those of Prevotella 7, Succinivibrio, Succiniclasticum, and Ruminococcaceae UCG-014. Metabolome analysis revealed that 8 ruminal metabolites, including some amino acids, were increased (P ≤ 0.05) by PROB, whereas no differences were found for SYNB. This study demonstrated that supplemental PROB or SYNB altered the ruminal bacterial community and metabolome differently to achieve a similar ruminal fermentation pattern.

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Specific enrichment of microbes and increased ruminal propionate production: the potential mechanism underlying the high energy efficiency of Holstein heifers fed steam-flaked corn

10.21203/rs.2.19347/v1 ◽

2019 ◽

Author(s):

Hao Ren ◽

Xiaodong Su ◽

Hanxun Bai ◽

Yuntian Yang ◽

Hongrong Wang ◽

...

Keyword(s):

Relative Abundance ◽

Starch Content ◽

Nitrogen Concentration ◽

Average Daily Gain ◽

High Energy ◽

Ammonia Nitrogen ◽

Feedlot Cattle ◽

Cellulolytic Bacteria ◽

Feed Conversion ◽

Host Animal

Abstract Corn grain is high in starch content and is primarily used as an energy source in ruminant diets. Compared with finely ground corn (FGC), steam-flaked corn (SFC) processing could improve the milk yield of lactating dairy cows and the growth performance of feedlot cattle, but the detailed mechanisms underlying this finding are unknown. The rumen microbiome contributes to feed efficiency by breaking down feedstuffs into energy substrates that can subsequently be utilized by the host animal. Therefore, the current study was conducted to investigate the ruminal bacterial community of heifers fed differently processed corn (SFC or FGC) with the same forage-to-concentrate ratio using 16S rRNA sequencing technologies and to uncover the detailed mechanisms underlying the high performance of ruminants fed the SFC diet. The results revealed that different processing methods resulted in changes in rumen characteristics and impacted the composition of the rumen bacterial structure. The SFC diet resulted in an increased average daily gain in heifers, an increased rumen propionate concentration and a decreased ammonia nitrogen concentration. The relative abundance of the phylum Firmicutes tended to increase and the relative abundance of the phylum Proteobacteria significantly increased in the heifers fed SFC diet compared with FGC diet. In addition, the relative abundance of amylolytic bacteria of the genera Succinivibrio , Rosebuia and Blautia ere evaluated, and cellulolytic bacteria (Ruminococcaceae_UCG-014 and Ruminococcaceae_UCG-013 ) decreased by the steam flaking method. Spearman correlation analysis between the relative abundances of the ruminal bacteria and the microbial metabolites showed that the rumen propionate concentration was positively correlated with Succinivibrio and Blautia abundance and negatively correlated with Ruminococcaceae_UCG-014 abundance. Evident patterns of efficient improvement in rumen propionate and changes in rumen microbes to further improve feed conversion were identified. This observation uncovers the potential mechanisms underlying the increased efficiency of the SFC processing method for enhancing ruminant performance.

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