Functional organization of the bovine rumen epithelium

Effects of feeding difructose anhydride on the mineral status and milking performance of transition cows

The objective of this study was to assess the potential effect of difructose anhydride III (DFAIII) on calcemia, magnesemia, and milking performance in dairy cows. A total of 66 multiparous Holstein cows in late pregnancy (gestation days, mean ± SD = 253.8 ± 2.13 d) were blocked according to their expected calving date and randomly assigned to either receiving no supplementation (control) or receiving 40 g/d of DFAIII (DFA) between -14 and +7 d relative to calving following a complete randomized block design. Cows in the control group received 640 g/d of a pellet containing no DFAIII, whereas DFA cows received the same pellet but containing 6.25% DFAIII. Pellets of each treatment were top-dressed on a daily basis while cows were dry and were fed via an automatic feeding system twice daily (320 g each feeding) during milking. Dry cows were fed once a day, whereas lactating cows were fed twice daily. Dry matter intake was individually monitored on a daily basis. Cows were milked twice daily and milk production and milk protein and fat contents recorded at every milking. Cows were kept on the study until they reached 21 d postpartum. Cows were weighed at dry-off (∼45 d before study enrollment) and twice daily after calving at the exit of the milking parlor. Cows were blood sampled for subsequent determination of serum Ca and Mg concentrations 3 d before the expected calving date and at 6, 12, 24, and 48 h and 7 and 14 d after calving. We found no differences in DMI before calving, but DFA cows consumed more feed than control cows at ∼15 DIM. All cows lost BW after calving, but DFA cows lost slightly less BW during the first 5 DIM than control cows. Cows on DFAIII produced more milk at ∼10 DIM compared with control cows, and DFAIII cows produced more milk protein than control cows 3 d after calving. Serum Ca concentrations were not affected by DFAIII supplementation; however, serum Mg concentrations at 6, 12, and 24 h after calving were greater in DFA than in control cows. In all, DFAIII did not affect postpartum calcemia but improved magnesemia between 6 and 24 h after calving. Milk production in DFA cows was improved around 10 d after calving and milk protein yield after 3 d postpartum compared with control cows. The mechanism leading to increased Mg availability is not clear and warrants further research.

Effects of the Interaction between Rumen Microbiota Density-VFAs-Hepatic Gluconeogenesis on the Adaptability of Tibetan Sheep to Plateau

During the adaptive evolution of animals, the host and its gut microbiota co-adapt to different elevations. Currently, there are few reports on the rumen microbiota-hepato-intestinal axis of Tibetan sheep at different altitudes. Therefore, the purpose of this study was to explore the regulatory effect of rumen microorganism-volatile fatty acids (VFAs)-VFAs transporter gene interactions on the key enzymes and genes related to gluconeogenesis in Tibetan sheep. The rumen fermentation parameters, rumen microbial densities, liver gluconeogenesis activity and related genes were determined and analyzed using gas chromatography, RT-qPCR and other research methods. Correlation analysis revealed a reciprocal relationship among rumen microflora-VFAs-hepatic gluconeogenesis in Tibetan sheep at different altitudes. Among the microbiota, Ruminococcus flavefaciens (R. flavefaciens), Ruminococcus albus (R. albus), Fibrobactersuccinogenes and Ruminobacter amylophilus (R. amylophilus) were significantly correlated with propionic acid (p < 0.05), while propionic acid was significantly correlated with the transport genes monocarboxylate transporter 4 (MCT4) and anion exchanger 2 (AE2) (p < 0.05). Propionic acid was significantly correlated with key enzymes such as pyruvate carboxylase, phosphoenolpyruvic acid carboxylase and glucose (Glu) in the gluconeogenesis pathway (p < 0.05). Additionally, the expressions of these genes were significantly correlated with those of the related genes, namely, forkhead box protein O1 (FOXO1) and mitochondrial phosphoenolpyruvate carboxykinase 2 (PCK2) (p < 0.05). The results showed that rumen microbiota densities differed at different altitudes, and the metabolically produced VFA contents differed, which led to adaptive changes in the key enzyme activities of gluconeogenesis and the expressions of related genes.

Metabolomics and proteomics insights into subacute ruminal acidosis etiology and inhibition of proliferation of yak rumen epithelial cells in vitro

BACKGROUND

Untargeted metabolomics and proteomics were employed to investigate the intracellular response of yak rumen epithelial cells (YRECs) to conditions mimicking subacute rumen acidosis (SARA) etiology, including exposure to short-chain fatty acids (SCFA), low pH5.5 (Acid), and lipopolysaccharide (LPS) exposure for 24 h.

RESULTS

These treatments significantly altered the cellular morphology of YRECs. Metabolomic analysis identified significant perturbations with SCFA, Acid and LPS treatment affecting 259, 245 and 196 metabolites (VIP > 1, P < 0.05, and fold change (FC) ≥ 1.5 or FC ≤ 0.667). Proteomic analysis revealed that treatment with SCFA, Acid, and LPS resulted in differential expression of 1251, 1396, and 242 proteins, respectively (FC ≥ 1.2 or ≤ 0.83, P < 0.05, FDR < 1%). Treatment with SCFA induced elevated levels of metabolites involved in purine metabolism, glutathione metabolism, and arginine biosynthesis, and dysregulated proteins associated with actin cytoskeleton organization and ribosome pathways. Furthermore, SCFA reduced the number, morphology, and functionality of mitochondria, leading to oxidative damage and inhibition of cell survival. Gene expression analysis revealed a decrease the genes expression of the cytoskeleton and cell cycle, while the genes expression associated with inflammation and autophagy increased (P < 0.05). Acid exposure altered metabolites related to purine metabolism, and affected proteins associated with complement and coagulation cascades and RNA degradation. Acid also leads to mitochondrial dysfunction, alterations in mitochondrial integrity, and reduced ATP generation. It also causes actin filaments to change from filamentous to punctate, affecting cellular cytoskeletal function, and increases inflammation-related molecules, indicating the promotion of inflammatory responses and cellular damage (P < 0.05). LPS treatment induced differential expression of proteins involved in the TNF signaling pathway and cytokine-cytokine receptor interaction, accompanied by alterations in metabolites associated with arachidonic acid metabolism and MAPK signaling (P < 0.05). The inflammatory response and activation of signaling pathways induced by LPS treatment were also confirmed through protein interaction network analysis. The integrated analysis reveals co-enrichment of proteins and metabolites in cellular signaling and metabolic pathways.

CONCLUSIONS

In summary, this study contributes to a comprehensive understanding of the detrimental effects of SARA-associated factors on YRECs, elucidating their molecular mechanisms and providing potential therapeutic targets for mitigating SARA.

Postnatal Growth and Development of the Rumen: Integrating Physiological and Molecular Insights

The rumen plays an essential role in the physiology and production of agriculturally important ruminants such as cattle. Functions of the rumen include fermentation, absorption, metabolism, and protection. Cattle are, however, not born with a functional rumen, and the rumen undergoes considerable changes in size, histology, physiology, and transcriptome from birth to adulthood. In this review, we discuss these changes in detail, the factors that affect these changes, and the potential molecular and cellular mechanisms that mediate these changes. The introduction of solid feed to the rumen is essential for rumen growth and functional development in post-weaning calves. Increasing evidence suggests that solid feed stimulates rumen growth and functional development through butyric acid and other volatile fatty acids (VFAs) produced by microbial fermentation of feed in the rumen and that VFAs stimulate rumen growth and functional development through hormones such as insulin and insulin-like growth factor I (IGF-I) or through direct actions on energy production, chromatin modification, and gene expression. Given the role of the rumen in ruminant physiology and performance, it is important to further study the cellular, molecular, genomic, and epigenomic mechanisms that control rumen growth and development in postnatal ruminants. A better understanding of these mechanisms could lead to the development of novel strategies to enhance the growth and development of the rumen and thereby the productivity and health of cattle and other agriculturally important ruminants.

Early concentrate starter introduction induces rumen epithelial parakeratosis by blocking keratinocyte differentiation with excessive ruminal butyrate accumulation

INTRODUCTION

Rumen epithelial parakeratosis, a common disease in ruminants caused by abnormalities in the ruminal stratified squamous epithelial keratinization process, negatively impacts ruminant health and performance. However, we still lack a comprehensive perception of the underlying mechanisms and the predisposing factors for this disorder.

OBJECTIVES

Here, we investigated rumen epithelial cell heterogeneity, differentiation trajectories, and cornification to clarify the rumen epithelial keratinization process and discern the key ruminal metabolites contributing to rumen epithelial parakeratosis.

METHODS

Twenty-four 14-day-old lambs were divided into three groups, including only milk feeding, milk plus alfalfa hay feeding, and milk plus corn-soybean concentrate starter feeding. At 42 days of age, the lambs were slaughtered, and rumen tissues were collected for single-cell RNA-sequencing (scRNA-seq), immunofluorescence, and quantitative real-time PCR (qRT-PCR) analyses. Ruminal fluid samples were collected for metabolomic analyses. Rumen epithelial organoid was used to verify the key ruminal metabolites contributing to parakeratosis.

RESULTS

As expected, we observed that concentrate starter introduction resulted in rumen epithelial parakeratosis. Moreover, scRNA-seq analysis revealed a developmental impediment in the transition from differentiated keratinocytes to terminally differentiated keratinocytes (TDK) in lambs with concentrate starter introduction. Immunofluorescence and qRT-PCR analyses further verified the location and expression of marker genes of TDK. Metabolomic analysis showed a robust positive correlation between ruminal butyrate levels and rumen epithelial keratinization. More importantly, we successfully established a rumen organoid model capable of facilitating the study of the keratinization process in the rumen epithelia and further confirmed that high dose butyrate indeed contributed to rumen epithelial parakeratosis.

CONCLUSION

Collectively, concentrate starter introduction induces ruminal epithelial parakeratosis by blocking keratinocyte differentiation with excessive ruminal butyrate accumulation in a neonatal lamb model. These findings enhance our understanding of rumen epithelial keratinization and provide valuable insights for addressing rumen epithelial parakeratosis using early nutritional intervention strategies.

3D sheep rumen epithelial structures driven from single cells in vitro

Ruminants play a vital economic role as livestock, providing high-quality protein for humans. At present, 3D-cultured ruminant abomasum and intestinal organoids have been successfully established to study host and pathogen interaction. The rumen is a unique digestive organ of ruminants that occupies 70% of the volume of the digestive tract and its microbiota can decompose lignocellulose to support animal growth. Here we report a method for culturing rumen epithelial organoids. We found that single rumen epithelial cells form self-organized 3D structures representative of typical stratified squamous epithelium, which is similar to rumen epithelium. EGF, Noggin, Wnt3a, IGF-1, and FGF-10 significantly enhanced the seeding efficiency of organoids. Moreover, the inclusion of CHIR-99021, A83-01, SB202190, and Y-27632 is crucial for organoid formation and maintenance. Importantly, we demonstrate that rumen epithelial cells retain their ability to form organoids after passage, cryopreservation, and resuscitation. The rumen epithelial organoids express rumen cell type-specific genes, uptake fatty acids, and generate 2D cultures. In summary, our data demonstrate that it is feasible to establish organoids from single rumen epithelial cells, which is a novel in vitro system that may reduce the use of experimental animals.

Transcriptomic analysis reveals that non-forage or forage fiber source promotes rumen development through different metabolic processes in lambs

Dietary fiber supplementation can stimulate rumen development in lambs during the pre-weaning period. However, it is unclear whether different sources of fiber have varying effects on rumen development. This study aimed to investigate the molecular mechanism of rumen morphological and functional development based on non-forage or forage as a starter dietary fiber source. Twenty-four male Hu lambs with similar body weights (BW, 3.67 ± 0.08 kg) were selected and divided into two groups that received diets supplemented with either alfalfa hay (AH) or soybean hull (SH). At the age of 70 days, six lambs were slaughtered from each treatment group for rumen fermentation and morphological analyses. Three samples of the rumen tissue from the ventral sac were collected for transcriptomic analysis. The results identified 633 differentially expressed genes (DEGs), of which 210 were upregulated and 423 were downregulated in the SH group compared with those in the AH group. The upregulated DEGs were most enriched in the immune function and proteolysis pathways, whereas the downregulated DEGs were mainly involved in cell proliferation, apoptosis, and differentiation pathways. These findings indicated that non-forage as a starter dietary fiber source improved immune function and enhanced nitrogen utilization, whereas forage facilitated rumen morphological development.

Effect of increased intake of concentrates and sodium butyrate supplementation on ruminal epithelium structure and function in growing rams

Increased ruminal butyrate production is considered to have a positive impact on rumen epithelium growth and function. However, excessive ruminal butyrate production may affect the rumen negatively, particularly when the rumen is already challenged with low pH. The aim of this study was to determine the effect of the inclusion of concentrates in the diet and sodium butyrate (SB) supplementation on ruminal epithelium growth and function in growing rams. Forty-two rams (27.8 ± 7.3 kg; 9-14 months of age) were allocated into six treatments and fed a diet with low (22.5% of diet DM; LOW) or high (60% of diet DM; HIGH) inclusion of concentrates in combination with no (SB0), 1.6% (SB1.6) or 3.2% (SB3.2) of diet DM inclusion of SB. There was no impact of the investigated factors on papilla dimensions and mucosa surface area, either in the atrium ruminis or ventral rumen (P ≥ 0.11). Stratum corneum thickness was higher for HIGH compared to LOW treatments (P ≤ 0.04), independently of the location in the rumen. In the atrium ruminis, the epithelium and living strata thickness quadratically increased due to SB supplementation for LOW treatments but quadratically decreased for HIGH treatments (concentrate inclusion × butyrate supplementation interaction; P ≤ 0.03); conversely, in the ventral sac of the rumen, a thicker epithelium was observed due to both increased concentrate inclusion in the diet and SB supplementation (P < 0.01) but living strata thickness was increased only by SB supplementation (linear effect; P < 0.01). The epithelium damage index in the ventral sac of the rumen was higher for LOW compared to HIGH treatments (P = 0.02). Increased inclusion of concentrates in the diet increased mRNA expression of monocarboxylate transporter 1 in both the epithelium of the atrium ruminis and ventral rumen, occludin in the epithelium of the atrium ruminis and downregulated in adenoma in the epithelium of the ventral rumen (P ≤ 0.02). Protein expression of claudin-4 in the epithelium of the ventral rumen was the highest for the HIGH/SB1.6 and HIGH/SB3.2 treatments (significant effect of interaction between main effects; P < 0.01). Under the conditions of the current study, increased intake of concentrates had mostly positive effects on ruminal epithelium in growing rams, and the same was observed for the effect of SB supplementation. However, the effect of SB supplementation was at least partially affected by the inclusion of concentrates in the diet.

The early life immune dynamics and cellular drivers at single-cell resolution in lamb forestomachs and abomasum

BACKGROUND

Four-chambered stomach including the forestomachs (rumen, reticulum, and omasum) and abomasum allows ruminants convert plant fiber into high-quality animal products. The early development of this four-chambered stomach is crucial for the health and well-being of young ruminants, especially the immune development. However, the dynamics of immune development are poorly understood.

RESULTS

We investigated the early gene expression patterns across the four-chambered stomach in Hu sheep, at 5, 10, 15, and 25 days of age. We found that forestomachs share similar gene expression patterns, all four stomachs underwent widespread activation of both innate and adaptive immune responses from d 5 to 25, whereas the metabolic function were significantly downregulated with age. We constructed a cell landscape of the four-chambered stomach using single-cell sequencing. Integrating transcriptomic and single-cell transcriptomic analyses revealed that the immune-associated module hub genes were highly expressed in T cells, monocytes and macrophages, as well as the defense-associated module hub genes were highly expressed in endothelial cells in the four-stomach tissues. Moreover, the non-immune cells such as epithelial cells play key roles in immune maturation. Cell communication analysis predicted that in addition to immune cells, non-immune cells recruit immune cells through macrophage migration inhibitory factor signaling in the forestomachs.

CONCLUSIONS

Our results demonstrate that the immune and defense responses of four stomachs are quickly developing with age in lamb's early life. We also identified the gene expression patterns and functional cells associated with immune development. Additionally, we identified some key receptors and signaling involved in immune regulation. These results help to understand the early life immune development at single-cell resolution, which has implications to develop nutritional manipulation and health management strategies based on specific targets including key receptors and signaling pathways.

Establishment of SV40 Large T-Antigen-Immortalized Yak Rumen Fibroblast Cell Line and the Fibroblast Responses to Lipopolysaccharide

The yak lives in harsh alpine environments and the rumen plays a crucial role in the digestive system. Rumen-associated cells have unique adaptations and functions. The yak rumen fibroblast cell line (SV40T-YFB) was immortalized by introducing simian virus 40 large T antigen (SV40T) by lentivirus-mediated transfection. Further, we have reported the effects of lipopolysaccharide (LPS) of different concentrations on cell proliferation, extracellular matrix (ECM), and proinflammatory mediators in SV40T-YFB. The results showed that the immortalized yak rumen fibroblast cell lines were identified as fibroblasts that presented oval nuclei, a fusiform shape, and positive vimentin and SV40T staining after stable passage. Chromosome karyotype analysis showed diploid characteristics of yak (n = 60). LPS at different concentrations inhibited cell viability in a dose-dependent manner. SV40T-YFB treated with LPS increased mRNA expression levels of matrix metalloproteinases (MMP-2 and MMP-9), inflammatory cytokines (TNF-α, IL-1β, IL-6), and urokinase-type plasminogen activator system components (uPA, uPAR). LPS inhibits the expression of tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2), plasminogen activator inhibitor-2 (PAI-2), fibronectin (FN), anti-inflammatory factor IL-10, and collagen I (COL I) in SV40T-YFB. Overall, these results suggest that LPS inhibits cell proliferation and induces ECM degradation and inflammatory response in SV40T-YFB.

Physical, Metabolic, and Microbial Rumen Development in Goat Kids: A Review on the Challenges and Strategies of Early Weaning

The digestive system of newborn ruminant functions is similar to monogastric animals, and therefore milk flows into the abomasum instead of rumen for digestion. The rumen undergoes tremendous changes over time in terms of structure, function, and microbiome. These changes contribute to the smooth transition from the dependence on liquid diets to solid diets. Goat kids are usually separated at early ages from their dams in commercial intensive systems. The separation from dams minimizes the transfer of microbiota from dams to newborns. In this review, understanding how weaning times and methodologies could affect the normal development and growth of newborn goats may facilitate the development of new feeding strategies to control stress in further studies.

Blend of Cinnamaldehyde, Eugenol, and Capsicum Oleoresin Improved Rumen Health of Lambs Fed High-Concentrate Diet as Revealed by Fermentation Characteristics, Epithelial Gene Expression, and Bacterial Community

We investigated the effects of CEC on the fermentation characteristics, epithelial gene expression, and bacterial community in the rumen of lambs fed a high-concentrate diet. Twenty-four 3-month-old female crossbred lambs with an initial body weight of 30.37 ± 0.57 kg were randomly allocated to consume a diet supplemented with 80 mg/kg CEC (CEC) or not (CON). The experiment consisted of a 14 d adaptation period and a 60 d data collection period. Compared with the CON group, the CEC group had higher ADG, epithelial cell thickness, ruminal butyrate proportion, and lower ammonia nitrogen concentration. Increases in the mRNA expression of Occludin and Claudin-4, as well as decreases in the mRNA expression of apoptotic protease activating factor-1 (Apaf-1), cytochrome c (Cyt-C), Caspase-8, Caspase-9, Caspase-3, Caspase-7, and toll-like receptor 4 (TLR4), were observed in the CEC group. Moreover, CEC treatment also decreased the concentration of IL-1β, IL-12, and TNF-α. Supplementation with CEC altered the structure and composition of the rumen bacterial community, which was indicated by the increased relative abundances of Firmicutes, Synergistota, Rikenellaceae_RC9_gut_group, Olsenella, Schwartzia, Erysipelotrichaceae_UCG-002, Lachnospiraceae_NK3A20_group, Acetitomaculum, [Eubacterium]_ruminantium_group, Prevotellaceae_UCG-004, Christensenellaceae_R-7_group, Sphaerochaeta, Pyramidobacter, and [Eubacterium]_eligens_group, and the decreased relative abundances of Acidobacteriota, Chloroflexi, Gemmatimonadota, and MND1. Furthermore, Spearman correlation analysis revealed that the altered rumen bacteria were closely correlated with rumen health-related indices. Dietary CEC supplementation improved growth performance, reduced inflammation and apoptosis, protected barrier function, and modulated the bacterial community of lambs fed a high-concentrate diet.

Abundance of Amino Acid Transporters and mTOR Pathway Components in the Gastrointestinal Tract of Lactating Holstein Cows

Data from non-ruminants indicate that amino acid (AA) transport into cells can regulate mTOR pathway activity and protein synthesis. Whether mTOR is expressed in the ruminant gastrointestinal tract (GIT) and how it may be related to AA transporters and the AA concentrations in the tissue is unknown. Ruminal papillae and the epithelia of the duodenum, jejunum, and ileum collected at slaughter from eight clinically healthy Holstein in mid-lactation were used. Metabolites and RNA were extracted from tissue for liquid chromatography–mass spectrometry and RT-qPCR analysis. The glycine and asparagine concentrations in the rumen were greater than those in the intestine (p < 0.05), but the concentrations of other AAs were greater in the small intestine than those in the rumen. Among the 20 AAs identified, the concentrations of glutamate, alanine, and glycine were the greatest. The mRNA abundances of AKT1 and MTOR were greater in the small intestine than those in the rumen (p < 0.05). Similarly, the SLC1A1, SLC6A6, SLC7A8, SLC38A1, SLC38A7, and SLC43A2 mRNA abundances were greater (p < 0.05) in the small intestine than those in the rumen. The mRNA abundances of SLC1A5, SLC3A2, and SLC7A5 were greater in the rumen than those in the small intestine (p < 0.05). Overall, the present study provides fundamental data on the relationship between mTOR pathway components and the transport of AAs in different sections of the gastrointestinal tract.

Proteome changes of dairy calves rumen epithelium from birth to postweaning

Background: Rumen epithelium plays a central role in absorbing, transporting, and metabolizing of short-chain fatty acids. For dairy calves, the growth of rumen papillae greatly enhances the rumen surface area to absorb nutrients. However, the molecular mechanism underlying dairy calves rumen postnatal development remains rarely understood. Results: Here, we firstly describe the histological change of rumen epithelium from birth to day 90 of age. Then, a shotgun approach and bioinformatics analyses were used to investigate and compare proteomic profiles of Holstein calve rumen epithelium on day 0, 30, 60 and 90 of age. A total of 4372 proteins were identified, in which we found 852, 342, 164 and 95 differentially expressed proteins between D0 and D30, between D30 and D60, between D60 and D90, respectively. Finally, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to provide a comprehensive proteomic landscape of dairy calves rumen development at tissue level. Conclusion: To conclude, our data indicated that keratinocyte differentiation, mitochondrion formation, the establishment of urea transport and innate immune system play central roles during rumen epithelium development. Tetrahydrobiopterin (BH4) presents an important role in rumen epithelial keratinization. The biological processes of BH4 biosynthesis and molecular function of nicotinamide adenine dinucleotide phosphate binding participate in mitochondrial cristae formation. The proposed datasets provide a useful basis for future studies to better comprehend dairy calves rumen epithelial development.

Meta-analysis of flavonoids use into beef and dairy cattle diet: Performance, antioxidant status, ruminal fermentation, meat quality, and milk composition

The objective of this study was to evaluate the effects of dietary supplementation with flavonoids (FLAs) on animal performance, diet digestibility, antioxidant status in blood serum, rumen parameters, meat quality, and milk composition in beef and dairy cattle through a meta-analysis. Thirty-six peer-reviewed publications were included in the data set. The weighted mean differences (WMD) between the FLAs treatments and the control treatment were used to assess the effect size. Dietary supplementation with FLAs decreased feed conversion ratio (WMD = -0.340 kg/kg; p = 0.050) and increased (p < 0.05) dry matter intake (WMD = 0.191 kg/d), dry matter digestibility (WMD = 15.283 g/kg of DM), and daily weight gain (WMD = 0.061 kg/d). In blood serum, FLAs supplementation decreased the serum concentration of malondialdehyde (WMD = -0.779 nmol/mL; p < 0.001) and increased (p < 0.01) the serum concentration of superoxide dismutase (WMD = 8.516 U/mL), glutathione peroxidase (WMD = 12.400 U/mL) and total antioxidant capacity (WMD = 0.771 U/mL). A higher ruminal propionate concentration (WMD = 0.926 mol/100 mol; p = 008) was observed in response to FLAs supplementation. In meat, the dietary inclusion of FLAs decreased (p < 0.05) shear force (WMD = -1.018 kgf/cm²), malondialdehyde content (WMD = -0.080 mg/kg of meat), and yellowness (WMD = -0.460). Supplementation with FLAs decreased milk somatic cell count (WMD = -0.251 × 103 cells/mL; p < 0.001) and increased (p < 0.01) milk production (WMD = 1.348 kg/d), milk protein content (WMD = 0.080/100 g) and milk fat content (WMD = 0.142/100 g). In conclusion, dietary supplementation with FLAs improves animal performance and nutrient digestibility in cattle. In addition, FLAs improve the antioxidant status in blood serum and the quality of meat and milk.

Morphological aspects of rumen papillae of lambs fed agro-industrial wastes

Sheep meet production systems require roughage feed of good nutritional quality. However, the production of sorghum or corn silage, besides expensive, also depends on large cultivable areas and favorable weather conditions. Thus, agro-industrial residues have stood out as a feed alternative that contribute to the reduction of production costs and to the conservation of the environment. Fragments of the ruminal mucosa of 30 healthy lambs fed with agro-industrial residues and slaughtered with a final weight of 36 kg were analyzed by light and scanning electron microscopy. We observed that the coproducts grape residue and wet brewery residue affected the shape, dimensions, and cytoarchitecture of the rumen epithelium in contrast to traditional sorghum silage. The rumen papillae of lambs fed grape waste were larger, and their epithelium was thinner when compared to the papillae of lambs fed wet brewery waste and sorghum silage. It can be assumed that the increased mucosal surface area of the rumen contributed to greater weight gain and reduced time to slaughter. The use of a greater variety of agro-industrial residues as a substitute for traditional feedstuffs contributes to the increase in animal protein production in many countries, making the confinement of sheep more viable and sustainable.

Rumen Epithelial Development- and Metabolism-Related Genes Regulate Their Micromorphology and VFAs Mediating Plateau Adaptability at Different Ages in Tibetan Sheep

The rumen is an important hallmark organ of ruminants and plays an important role in the metabolism and immune barrier of Tibetan sheep on the Plateau. However, there are few studies on rumen development and metabolism regulation in Tibetan sheep at different ages. Here, we comprehensively analyzed the immune function, fermentation function, rumen epithelial micromorphology and transcriptome profile of Tibetan sheep at different ages. The results showed that the concentration of IgG decreased and the concentration of IgM increased with age (p < 0.05), and the highest concentration of IgA was observed at 1.5 and 3.5 years of age. In terms of rumen fermentation characteristics, VFAs of 4-month-old lambs were the highest, followed by VFAs and NH3-N of Tibetan sheep at 3.5 years of age. Hematoxylin-eosin staining and transmission electron microscopy section examination of rumen epithelial tissue showed that the rumen papilla width increased with age (p < 0.001), the thickness of the stratum corneum decreased, the cells in the stratum corneum showed accelerated migration and the thickness of the rumen muscle layer increased (p < 0.001). Desmosomal junctions between the layers of rumen epithelium increased at 1.5 and 3.5 years old, forming a compact barrier structure, and the basal layer had more mitochondria involved in the regulation of energy metabolism. RNA-seq analysis revealed that a total of 1006 differentially expressed genes (DEGs) were identified at four ages. The DEGs of Tibetan sheep aged 4 months and 6 years were mainly enriched in the oxidation−reduction process and ISG15-protein conjugation pathway. The 1.5 and 3.5-year-olds were mainly enriched in skeletal muscle thin filament assembly, mesenchyme migration and the tight junction pathway. WGCNA showed that DEGs related to rumen microbiota metabolite VFAs and epithelial morphology were enriched in “Metabolism of xenobiotics by cytochrome P450, PPAR signaling pathway, Butanoate metabolism pathways” and participated in the regulation of rumen epithelial immune and fermentation metabolism functions of Tibetan sheep at different ages. This study systematically revealed the regulatory mechanism of rumen epithelial development and metabolism in the plateau adaptation of Tibetan sheep, providing a new approach for the study of plateau adaptation.

Mulberry flavonoids modulate rumen bacteria to alter fermentation kinetics in water buffalo

Mulberry flavonoids can modulate the composition of rumen microbiota in ruminants to improve nutrient digestibility, owing to their strong biological activities. This study aimed to explore the effect of mulberry leaf flavonoids (MLF) on rumen bacteria, fermentation kinetics, and metagenomic functional profile in water buffalo. Forty buffaloes (4 ± 1 lactations) with almost same body weight (av. 600 ± 50 Kg) and days in milk (90 ± 20 d) were randomly allocated to four treatments having different levels of MLF: 0 g/d (control), 15 g/d (MLF15), 30 g/d (MLF30), and 45 g/d (MLF45) supplemented in a basal diet. After 35 days of supplementation, rumen contents were collected to determine rumen fermentation parameters. The 16S rRNA gene sequencing was performed to elucidate rumen bacteria composition. The obtained taxonomic data were analyzed to explore the rumen bacteriome and predict the associated gene functions and metabolic pathways. Results demonstrated a linear increase (p < 0.01) in rumen acetate, propionate, and total VFAs in the MLF45 group as compared to control. No effect of treatment was observed on rumen pH and butyrate contents. Acetate to propionate ratio in the MLF45 group linearly and quadratically decreased (p = 0.001) as compared to MLF15 and control groups. Similarly, MLF45 linearly increased (p < 0.05) the microbial protein (MCP) and NH₃-N as compared to other treatments. Treatment adversely affected (p < 0.01) almost all alpha diversity parameters of rumen bacteria except Simpson index. MLF promoted the abundance of Proteobacteria while reducing the relative abundances of Actinobacteria, Acidobacteria, Chloroflexi, and Patescibacteria. The MLF supplementation tended to substantially reduce (0.05 < p < 0.1) the abundance of Actinobacteria, and Patescibacteria while completely eliminating Acidobacteria (p = 0.029), Chloroflexi (p = 0.059), and Gemmatimonadetes (p = 0.03) indicating the negative effect of flavonoids on the growth of these bacteria. However, MLF45 tended to substantially increase (p = 0.07) the abundance (~21.5%) of Acetobacter. The MLF treatment exhibited negative effect on five genera by significantly reducing (Sphingomonas) or eliminating (Arthobactor, unclassified_c__Actinobacteria, norank_c__Subgroup_6, norank_o__Saccharimonadales, and Nocardioides) them from the rumen microbiota. Pearson correlation analysis revealed 3, 5 and 23 positive correlations of rumen bacteria with milk yield, rumen fermentation and serum antioxidant parameters, respectively. A positive correlation of MCP was observed with three bacterial genera (Acetobacter, Enterobacter, and Klebsiella). The relative abundance of Pseudobutyrivibrio and Empedobacter also showed a positive correlation with the ruminal acetate and propionate. The present study indicated 45 g/d as an appropriate dose of MLF which modulated rumen bacteria and its functional profile in water buffalo.

Microbiota-host crosstalk in the newborn and adult rumen at single-cell resolution

BACKGROUND

The rumen is the hallmark organ of ruminants, playing a vital role in their nutrition and providing products for humans. In newborn suckling ruminants milk bypasses the rumen, while in adults this first chamber of the forestomach has developed to become the principal site of microbial fermentation of plant fibers. With the advent of single-cell transcriptomics, it is now possible to study the underlying cell composition of rumen tissues and investigate how this relates the development of mutualistic symbiosis between the rumen and its epithelium-attached microbes.

RESULTS

We constructed a comprehensive cell landscape of the rumen epithelium, based on single-cell RNA sequencing of 49,689 high-quality single cells from newborn and adult rumen tissues. Our single-cell analysis identified six immune cell subtypes and seventeen non-immune cell subtypes of the rumen. On performing cross-species analysis of orthologous genes expressed in epithelial cells of cattle rumen and the human stomach and skin, we observed that the species difference overrides any cross-species cell-type similarity. Comparing adult with newborn cattle samples, we found fewer epithelial cell subtypes and more abundant immune cells, dominated by T helper type 17 cells in the rumen tissue of adult cattle. In newborns, there were more fibroblasts and myofibroblasts, an IGFBP3⁺ epithelial cell subtype not seen in adults, while dendritic cells were the most prevalent immune cell subtype. Metabolism-related functions and the oxidation-reduction process were significantly upregulated in adult rumen epithelial cells. Using 16S rDNA sequencing, fluorescence in situ hybridization, and absolute quantitative real-time PCR, we found that epithelial Desulfovibrio was significantly enriched in the adult cattle. Integrating the microbiome and metabolome analysis of rumen tissues revealed a high co-occurrence probability of Desulfovibrio with pyridoxal in the adult cattle compared with newborn ones while the scRNA-seq data indicated a stronger ability of pyroxidal binding in the adult rumen epithelial cell subtypes. These findings indicate that Desulfovibrio and pyridoxal likely play important roles in maintaining redox balance in the adult rumen.

CONCLUSIONS

Our integrated multi-omics analysis provides novel insights into rumen development and function and may facilitate the future precision improvement of rumen function and milk/meat production in cattle.

Proteome changes of sheep rumen epithelium during postnatal development

Background: The development of the rumen epithelium is a critical physiological challenge for sheep. However, the molecular mechanism underlying postnatal rumen development in sheep remains rarely understood.

Results: Here, we used a shotgun approach and bioinformatics analyses to investigate and compare proteomic profiles of sheep rumen epithelium tissue on day 0, 15, 30, 45, and 60 of age. A total of 4,523 proteins were identified, in which we found 852, 342, 164, and 95 differentially expressed proteins (DEPs) between day 0 and day 15, between day 15 and day 30, between day 30 and day 45, between day 45 and day 60, respectively. Furthermore, subcellular localization analysis showed that the DEPs were majorly localized in mitochondrion between day 0 and day 15, after which nucleus proteins were the most DEPs. Finally, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that DEPs significantly enriched in mitochondrion, ubiquitination, histone modifications, glutathione synthase activity, and wnt and nortch signaling pathways.

Conclusion: Our data indicate that the biogenesis of mitochondrion in rumen epithelial cell is essential for the initiation of rumen epithelial development. Glutathione, wnt signaling pathway and nortch signaling pathway participated in rumen epithelial growth. Ubiquitination, post-translational modifications of histone might be key molecular functions in regulating rumen epithelial development.

Thiamine Supplementation Alleviates Lipopolysaccharide-Triggered Adaptive Inflammatory Response and Modulates Energy State via Suppression of NFκB/p38 MAPK/AMPK Signaling in Rumen Epithelial Cells of Goats

Studies have shown that exogenous thiamine (THI) supplementation can alleviate inflammation and promote rumen epithelial development in goats and cows. This research aimed to evaluate the effect of THI supplementation on LPS-induced inflammation and energy metabolic dysregulation in RECs of goats. Cells were stimulated with either 5 μg/mL THI for 18 h (THI group) or with 5 μg/mL LPS for 6 h (LPS group). The CON group was stimulated with DMEM/F-12 medium without THI for 18 h. The LPTH group was pretreated with THI for 18 h, followed by LPS stimulation for 6 h. THI supplementation decreased the ROS content (p < 0.05), as well as the ratios of phosphorylated (p)-p65 to p65 (p < 0.05) and p-AMPKα to AMPKα (p < 0.05). Interestingly, when the p38 gene was overexpressed in the LPTH group, the ratio of p-p65 to p65 and p-AMPKα to AMPKα proteins significantly increased, and ATP content decreased (p < 0.05). Our results suggest that THI possesses anti-inflammatory and metabolic-modulatory effects in RECs. The mechanism is largely related to the suppression of the NF-κB/p38 MAPK/AMPK signaling pathway. Additionally, we also revealed that THI supplementation can inhibit LPS-induced oxidative damage and apoptosis to protect mitochondrial function in RECs.

Quantification of cytosol and membrane proteins in rumen epithelium of sheep with low or high CH4 emission phenotype

BACKGROUND

Ruminant livestock are a major contributor to Australian agricultural sector carbon emissions. Variation in methane (CH4) produced from enteric microbial fermentation of feed in the reticulo-rumen of sheep differs with different digestive functions.

METHOD

We isolated rumen epithelium enzymatically to extract membrane and cytosol proteins from sheep with high (H) and low (L) CH4 emission. Protein abundance was quantified using SWATH-mass spectrometry.

RESULTS

The research found differences related to the metabolism of glucose, lactate and processes of cell defence against microbes in sheep from each phenotype. Enzymes in the methylglyoxal pathway, a side path of glycolysis, resulting in D-lactate production, differed in abundance. In the H CH4 rumen epithelium the enzyme hydroxyacylglutathione hydrolase (HAGH) was 2.56 fold higher in abundance, whereas in the L CH4 epithelium lactate dehydrogenase D (LDHD) was 1.93 fold higher. Malic enzyme 1 which converts D-lactate to pyruvate via the tricarboxylic cycle was 1.57 fold higher in the L CH4 phenotype. Other proteins that are known to regulate cell defence against microbes had differential abundance in the epithelium of each phenotype.

CONCLUSION

Differences in the abundance of enzymes involved in the metabolism of glucose were associated with H and L CH4 phenotype sheep. Potentially this represents an opportunity to use protein markers in the rumen epithelium to select low CH4 emitting sheep.

Response of Ruminal Microbiota-Host Gene Interaction to High-Altitude Environments in Tibetan Sheep

Altitude is the main external environmental pressure affecting the production performance of Tibetan sheep, and the adaptive evolution of many years has formed a certain response mechanism. However, there are few reports on the response of ruminal microbiota and host genomes of Tibetan sheep to high-altitude environments. Here, we conducted an integrated analysis of volatile fatty acids (VFAs), microbial diversity (16S rRNA), epithelial morphology, and epithelial transcriptome in the rumen of Tibetan sheep at different altitudes to understand the changes in ruminal microbiota−host interaction in response to high altitude. The differences in the nutritional quality of forage at different altitudes, especially the differences in fiber content (ADF/NDF), led to changes in rumen VFAs of Tibetan sheep, in which the A/P value (acetic acid/propionic acid) was significantly decreased (p < 0.05). In addition, the concentrations of IgA and IgG in Middle-altitude (MA) and High-altitude Tibetan sheep (HA) were significantly increased (p < 0.05), while the concentrations of IgM were significantly increased in MA (p < 0.05). Morphological results showed that the width of the rumen papilla and the thickness of the basal layer increased significantly in HA Tibetan sheep (p < 0.05). The 16S rRNA analysis found that the rumen microbial diversity of Tibetan sheep gradually decreased with increasing altitude, and there were some differences in phylum- and genus-level microbes at the three altitudes. RDA analysis found that the abundance of the Rikenellaceae RC9 gut group and the Ruminococcaceae NK4A214 group increased with altitudes. Furthermore, a functional analysis of the KEGG microbial database found the “lipid metabolism” function of HA Tibetan sheep to be significantly enriched. WGCNA revealed that five gene modules were enriched in “energy production and conversion”, “lipid transport and metabolism”, and “defense mechanisms”, and cooperated with microbiota to regulate rumen fermentation and epithelial immune barrier function, so as to improve the metabolism and immune level of Tibetan sheep at high altitude.

Influence of the Gut Microbiome on Feed Intake of Farm Animals

With the advancement of microbiome research, the requirement to consider the intestinal microbiome as the “last organ” of an animal emerged. Through the production of metabolites and/or the stimulation of the host’s hormone and neurotransmitter synthesis, the gut microbiota can potentially affect the host’s eating behavior both long and short-term. Based on current evidence, the major mediators appear to be short-chain fatty acids (SCFA), peptide hormones such as peptide YY (PYY) and glucagon-like peptide-1 (GLP-1), as well as the amino acid tryptophan with the associated neurotransmitter serotonin, dopamine and γ-Aminobutyrate (GABA). The influence appears to extend into central neuronal networks and the expression of taste receptors. An interconnection of metabolic processes with mechanisms of taste sensation suggests that the gut microbiota may even influence the sensations of their host. This review provides a summary of the current status of microbiome research in farm animals with respect to general appetite regulation and microbiota-related observations made on the influence on feed intake. This is briefly contrasted with the existing findings from research with rodent models in order to identify future research needs. Increasing our understanding of appetite regulation could improve the management of feed intake, feed frustration and anorexia related to unhealthy conditions in farm animals.

Developmental Alterations of Colonic microRNA Profiles Imply Potential Biological Functions in Kid Goats

The colon is a crucial digestive organ of the hind gut in ruminants. The bacterial diversity and mucosal immune maturation in this region are related to age. However, whether the microRNA expression in the colon of goats is affected by age is still unclear. In the current study, we analyzed the transcriptomes of colon microRNAs during preweaning (Day 10 and Day 25) and postweaning (Day 31). A total of 1572 microRNAs were identified in the colon tissues. Of these, 39 differentially expressed microRNAs (DEmiRNAs) and 88 highly expressed microRNAs (HEmiRNAs) were screened. The target genes regulated by the DEmiRNAs and HEmiRNAs were commonly enriched in the MAPK signaling pathway, Wnt signaling pathway, Hippo signaling pathway, cell adhesion molecules, focal adhesion, and adherens junction. Remarkably, the targeted genes of the DEmiRNAs were highly enriched for the prevention of microbial invasion via the Erbb−MAPK network while the targeted genes of HEmiRNAs contributed to the permeable barrier maintenance and cell damage surveillance. Additionally, there were eight different expression profiles of 87 dynamic miRNAs, in which approximately half of them were affected by age. Taken together, our study reveals the different roles of DEmiRNAs, HEmiRNAs, and dynamic microRNAs in the development of the colon and gives new insights into the regulatory mechanism of colon development in goats.

Feedomics provides bidirectional omics strategies between genetics and nutrition for improved production in cattle

Increasing the efficiency and sustainability of cattle production is an effective way to produce valuable animal proteins for a growing human population. Genetics and nutrition are the 2 major research topics in selecting cattle with beneficial phenotypes and developing genetic potentials for improved performance. There is an inextricable link between genetics and nutrition, which urgently requires researchers to uncover the underlying molecular mechanisms to optimize cattle production. Feedomics integrates a range of omic techniques to reveal the mechanisms at different molecular levels related to animal production and health, which can provide novel insights into the relationships of genes and nutrition/nutrients. In this review, we summarized the applications of feedomics techniques to reveal the effect of genetic elements on the response to nutrition and investigate how nutrients affect the functional genome of cattle from the perspective of both nutrigenetics and nutrigenomics. We highlighted the roles of rumen microbiome in the interactions between host genes and nutrition. Herein, we discuss the importance of feedomics in cattle nutrition research, with a view to ensure that cattle exhibit the best production traits for human consumption from both genetic and nutritional aspects.

Multi-Omics Reveals That the Rumen Transcriptome, Microbiome, and Its Metabolome Co-regulate Cold Season Adaptability of Tibetan Sheep

Tibetan sheep can maintain a normal life and reproduce in harsh environments under extreme cold and lack of nutrition. However, the molecular and metabolic mechanisms underlying the adaptability of Tibetan sheep during the cold season are still unclear. Hence, we conducted a comprehensive analysis of rumen epithelial morphology, epithelial transcriptomics, microbiology and metabolomics in a Tibetan sheep model. The results showed that morphological structure of rumen epithelium of Tibetan sheep in cold season had adaptive changes. Transcriptomics analysis showed that the differential genes were primarily enriched in the PPAR signaling pathway (ko03320), legionellosis (ko05134), phagosome (ko04145), arginine and proline metabolism (ko00330), and metabolism of xenobiotics by cytochrome P450 (ko00980). Unique differential metabolites were identified in cold season, such as cynaroside A, sanguisorbin B and tryptophyl-valine, which were mainly enriched in arachidonic acid metabolism, arachidonic acid metabolism and linolenic acid metabolism pathways, and had certain correlation with microorganisms. Integrated transcriptome-metabolome-microbiome analysis showed that epithelial gene-GSTM3 expression was upregulated in the metabolism of xenobiotics by the cytochrome P450 pathway during the cold season, leading to the downregulation of some harmful metabolites; TLR5 gene expression was upregulated and CD14 gene expression was downregulated in the legionellosis pathway during the cold season. This study comprehensively described the interaction mechanism between the rumen host and microbes and their metabolites in grazing Tibetan sheep during the cold season. Rumen epithelial genes, microbiota and metabolites act together in some key pathways related to cold season adaptation.

Establishment of Immortalized Yak Ruminal Epithelial Cell Lines by Lentivirus-Mediated SV40T and hTERT Gene Transduction

Yak is a unique species of cattle that is adapted to the harsh natural environment of the Qinghai-Tibet Plateau. Research on the function of the yak rumen is limited to animal experiments, and the cell molecular mechanism is very limited. The high cost of isolation and culture of adult yak rumen epithelial cells (YRECs), low success rate, and limited cell life limit the scope of long-term physiological functions and nutrient absorption mechanisms of yak rumen epithelium in vitro studies. This study aimed to explore the isolation and immortal culture methods of primary YRECs and establish a new cell line model for studying cell molecular mechanisms. The human telomerase reverse transcriptase gene (hTERT) and simian virus 40 large T antigen (SV40T) were transferred into primary YDECs using mammalian gene expression lentiviral vectors. The immortalized cell line (SV40T-YREC-hTERT) retains the morphological and functional characteristics of primary cells. The epithelial cell marker protein cytokeratin 18 of the immortalized cell lines was positive, and the cell proliferation and karyotype were normal. The SV40T and hTERT genes were successfully transferred into immortalized cell lines and maintained high expression. Simultaneously, the immortalized cell lines had normal function of short-chain fatty acid (SCFA) transport and absorption, and the immortalized yak rumen epithelial cell lines were successfully established. In addition, the transepithelial electrical resistance value gradually increased with culture time, and the permeability of epithelial cells decreased by culturing epithelial cells in Transwell culture chambers. Transmission electron microscopy demonstrated the submicroscopic structure of cells in the integrity barrier model and established the YREC barrier model in vitro.

Direct effect of lipopolysaccharide and histamine on permeability of the rumen epithelium of steers ex vivo

Disruption of the ruminal epithelium barrier occurs during subacute ruminal acidosis due to low pH, hyper-osmolality, and increased concentrations of lipopolysaccharide and histamine in ruminal fluid. However, the individual roles of lipopolysaccharide and histamine in the process of ruminal epithelium barriers disruption are not clear. The objective of the present investigation was to evaluate the direct effect of lipopolysaccharide and histamine on the barrier function of the ruminal epithelium. Compared with control (CON), histamine (HIS, 20 μM) increased the short-circuit current (Isc; 88.2%, P < 0.01), transepithelial conductance (Gt; 29.7%, P = 0.056), and the permeability of fluorescein 5(6)-isothiocyanate (FITC) (1.04-fold, P < 0.01) of ruminal epithelium. The apparent permeability of LPS was 1.81-fold higher than HIS (P < 0.01). The mRNA abundance of OCLN in ruminal epithelium was decreased by HIS (1.1-fold, P = 0.047). The results of the present study suggested that mucosal histamine plays a direct role in the disruption of ruminal epithelium barrier function, whereas lipopolysaccharide (at a pH of 7.4) has no effect on the permeability of rumen tissues ex vivo.

Effects of whole corn high-grain diet feeding on ruminal bacterial community and epithelial gene expression related to VFA absorption and metabolism in fattening lambs

The objective of this study was to investigate the effects of whole corn high-grain diet feeding on growth performance, ruminal bacterial community, and epithelial morphology and gene expression related to VFA absorption and metabolism in fattening lambs. Fourteen male (castrated) lambs were randomly assigned to either a group fed a ground corn high-grain diet (50.4% grain; HGC, n = 7) or a group fed a whole corn high-grain diet (50.4% grain; HWC, n = 7). After 7 wk of feeding, HWC group increased the average daily gain (ADG) (P = 0.036) and decreased the feed: gain value (P = 0.010) significantly. HWC group had a greater crude protein apparent digestibility (P = 0.028) in the third week and dry matter and neutral detergent fiber apparent digestibility (P < 0.05) in the seventh week. Pyrosequencing of the 16S ribosomal RNA gene revealed that HWC feeding increased the relative abundance of genera Anaerovibrio, Schwartzia and Unclassified Veillonellaceae in the rumen content and Howardella, Schwartzia and Unclassified Veillonellaceae in the rumen epithelia (P<0.05), while decreased the proportion of Lachnospira and Unclassified Synergistaceae in the rumen content and Anaerovorax, Papillibacter, Ruminococcus, Fibrobacter, Unclassified Lachnospiraceae, Unclassified Bacteroidales and Unclassified Prevotellaceae in the rumen epithelia (P < 0.05). HWC group increased the rumen papilla length (P = 0.001) and surface area (P = 0.002). Furthermore, HWC diet feeding up-regulated the relative mRNA expression of putative anion transporter isoform 1 (PAT1) (P = 0.032) in the rumen epithelia. In summary, compared with ground corn high-grain diet feeding, whole corn high-grain diet feeding improved animal performance, changed ruminal bacterial composition and diversity, and increased VFA absorption of epithelial papilla in fattening lambs. These findings provided theoretical guidance for the actual application of whole corn high-grain diet in ruminants.

Sex-Related Differences in UT-B Urea Transporter Abundance in Fallow Deer Rumen

Rumen studies have focused almost exclusively on livestock species under strictly regimented diets. This means that the ruminal condition of free-living and free-feeding wildlife remains practically unstudied. Urea nitrogen salvaging, a process by which urea is passed into the rumen, to both provide a valuable source of nitrogen for bacterial growth and to buffer the potentially harmful acidic effects of bacterial short chain fatty acids, has remained unexplored in wild ruminants, such as deer. UT-B2 transporters are the key proteins reported to facilitate the transepithelial ruminal urea transport. In this study, we investigate the expression, abundance and localisation of urea transporters in the rumen of a semi-wild fallow deer (Dama dama) population. Physical measurements confirmed that males had larger rumen than females, while adults had longer papillae than juveniles. Initial RT-PCR experiments confirmed the expression of UT-B2, while immunolocalisation studies revealed that strong UT-B staining was present in the stratum basale of deer rumen. Western blotting analysis demonstrated that a 50 kDa UT-B2 protein was significantly more abundant in adult females compared to adult males. This study confirms the presence of UT-B2 urea transporters in deer rumen and suggests that sex-related differences occur, bringing new insight into our understanding of rumen physiology.

Effects of Heat Stress on the Ruminal Epithelial Barrier of Dairy Cows Revealed by Micromorphological Observation and Transcriptomic Analysis

Heat stress (HS) alters the rumen fermentation of dairy cows thereby affecting the metabolism of rumen papillae and thus the epithelial barrier function. The aim of the present study was to investigate if HS damages the barrier function of ruminal epithelia. Eight multiparous Holstein dairy cows with rumen cannula were randomly equally allocated to two replicates (n = 4), with each replicate being subjected to heat stress or thermal neutrality and pair-feeding in four environmental chambers. Micromorphological observation showed HS aggravated the shedding of the corneum and destroyed the physical barrier of the ruminal epithelium to a certain extent. Transcriptomics analysis of the rumen papillae revealed pathways associated with DNA replication and repair and amino acid metabolism were perturbated, the biological processes including sister chromatid segregation, etc. were up-regulated by HS, while the MAPK and NF-kB cell signaling pathways were downregulated. However, no heat stress-specific change in the expression of tight junction protein or TLR4 signaling was found, suggesting that HS negatively affected the physical barrier of the ruminal epithelium to some extent but did not break the ruminal epithelium. Heat stress invoked mechanisms to maintain the integrity of the rumen epithelial barrier by upregulating the expression of heat shock protein and repairments in rumen papillae. The increase in amino acid metabolism in rumen papillae might affect the nutrient utilization of the whole body. The findings of this study may inform future research to better understand how heat stress affects the physiology and productivity of lactating cows and the development of mitigation strategies.

Effects of butyrate− on ruminal Ca2+ transport: evidence for the involvement of apically expressed TRPV3 and TRPV4 channels

The ruminal epithelium absorbs large quantities of NH₄⁺ and Ca²⁺. A role for TRPV3 has emerged, but data on TRPV4 are lacking. Furthermore, short-chain fatty acids (SCFA) stimulate ruminal Ca²⁺ and NH₄⁺ uptake in vivo and in vitro, but the pathway is unclear. Sequencing of the bovine homologue (bTRPV4) revealed 96.79% homology to human TRPV4. Two commercial antibodies were tested using HEK-293 cells overexpressing bTRPV4, which in ruminal protein detected a weak band at the expected ~ 100 kDa and several bands ≤ 60 kDa. Immunofluorescence imaging revealed staining of the apical membrane of the stratum granulosum for bTRPV3 and bTRPV4, with cytosolic staining in other layers of the ruminal epithelium. A similar expression pattern was observed in a multilayered ruminal cell culture which developed resistances of > 700 Ω · cm² with expression of zonula occludens-1 and claudin-4. In Ussing chambers, 2-APB and the TRPV4 agonist GSK1016790A stimulated the short-circuit current across native bovine ruminal epithelia. In whole-cell patch-clamp recordings on HEK-293 cells, bTRPV4 was shown to be permeable to NH₄⁺, K⁺, and Na⁺ and highly sensitive to GSK1016790A, while effects of butyrate⁻ were insignificant. Conversely, bTRPV3 was strongly stimulated by 2-APB and by butyrate⁻ (pH 6.4 > pH 7.4), but not by GSK1016790A. Fluorescence calcium imaging experiments suggest that butyrate⁻ stimulates both bTRPV3 and bTRPV4. While expression of bTRPV4 appears to be weaker, both channels are candidates for the ruminal transport of NH₄⁺ and Ca²⁺. Stimulation by SCFA may involve cytosolic acidification (bTRPV3) and cell swelling (bTRPV4).

Prebiotic and synbiotic effect on rumen papilla length development and rumen pH in 12-week-old calves

BACKGROUND AND AIM

Europe and the USA have banned antibiotics use as growth promoters. There is a need for alternative products that can ensure production and health protection. Prebiotics has been proposed as alternatives because these materials have wide-ranging physiological effects on gut function, activity of the large intestinal microflora, mineral absorption, and immunity. The aim of this study was to determine the effect of three different doses of inulin, a prebiotic, in combination with probiotic Enterococcus faecium (a new synbiotic) on postnatal rumen development by comparing rumen papilla length, width, muscle layer thickness, and content pH level.

MATERIALS AND METHODS

Randomly selected 23 (±5)-days-old healthy male Holstein crossbreed calves, weighing 50 kg (±5 kg), were randomly allocated to seven groups, ten in each group. The calves were kept in a pen of 5, under the same conditions and were fed twice a day, ~3.5 liters of whole milk per feeding. Control group (C n=10) was fed with whole milk only (no additives were added). The six other groups (three prebiotics and three synbiotics) received food additives with their morning milk feeding. The source of prebiotics, Jerusalem artichoke powder concentrate (JAPC) contained 50% of inulin. JAPC in doses of 6 g, 12 g, or 24 g were added to the milk. Formed prebiotic groups were denoted as PreG6, PreG12, and PreG24. To evaluate if the addition of the probiotic E. faecium 2×109 colony forming unit g-1 to manufacturer recommended dose of 0.25 g improves inulin effect on rumen, it was added to all their JAPC doses. The new content synbiotic groups were denoted as SynG6, SynG12, and SynG24. On day 57 of the study, when all calves were approximately 12 weeks old, they were slaughtered in a certified slaughterhouse. Tissue cultures for histological analysis were obtained from Saccus dorsalis and Saccus ventralis of the rumen. Tissue culture staining for histology was carried out using hematoxylin and eosin staining method. Rumen histological samples were used to measure papilla length, width, and muscle layer thickness. Each sample was used to make five measurements on the present rumen papilla.

RESULTS

The results showed that by adding 12 g of inulin to whole milk when feeding calves improves rumen papilla development, which is seen by increased length and width of papilla, especially in the Saccus ventralis region. By combing this dose of inulin with 0.25 g of E. faecium, a significant increase of papilla is achieved. Saccus ventralis muscle layer in the rumen is thicker than it is in Saccus dorsalis regardless of addition of prebiotics or synbiotics.

CONCLUSION

The addition of inulin to whole milk can influence the pH of the rumen by making it more alkaline. The addition of prebiotic inulin and a novel synbiotic (inulin combined with E. faecium) can accelerate postnatal rumen development and improve its functionality.

Establishment of a bovine rumen epithelial cell line

Rumen epithelium plays an essential role in absorption, transport, and metabolism of short-chain fatty acids, the main products of rumen fermentation, and in preventing microbes and other potentially harmful rumen contents from entering the systemic circulation. The objective of this study was to generate an immortal rumen epithelial cell line that can be used as a convenient model of rumen epithelial cells in vitro. We isolated primary rumen epithelial cells from a steer through trypsin digestion and transduced them with lentiviruses expressing the Simian Virus (SV) 40 T antigen. We cloned the transduced cells by limiting dilution. Western blotting analysis confirmed the expression of the SV40 T antigen in two single-cell clones. Cells from one clone, named bovine rumen epithelial clone 1 (BREC1), displayed a flat and squamous morphology in culture. RNA sequencing revealed that BREC1 cells expressed many markers of epithelial cells, including keratins, the epidermal growth factor receptor, and the short-chain fatty acid transporters monocarboxylic acid transporter (MCT) 1 (MCT-1) and MCT-4. RNA sequencing revealed that BREC1 cells expressed key enzymes such as 3-hydroxymethyl-3-methylglutaryl-CoA lyase and 3-hydroxy-3-methylglutaryl-CoA synthase 1 involved in ketogenesis, a unique function of rumen epithelial cells. RNA sequencing also revealed the expression of genes encoding tight junctions, desmosomes, anchoring junctions, and polarized plasma membranes, structures typical of epithelial cells, in BREC1 cells. Cell proliferation assays indicated that BREC1 cells were similar to primary rumen epithelial cells in response to insulin-like growth factor 1, insulin, and butyrate. In conclusion, BREC1 is not only a convenient but an appropriate model for studying the factors and mechanisms that control proliferation, apoptosis, differentiation, nutrient transport, metabolism, and barrier function in rumen epithelium.

Effect of High Sulfur Diet on Rumen Fermentation, Microflora, and Epithelial Barrier Function in Steers

Simple Summary

Effect of high sulfur diet on digestion and morphology of the ruminant gastrointestinal tract was investigated both in vitro and in vivo. The results showed that, though sulfur level had little effect on rumen fermentation and most of the rumen microbials, sulfate-reducing bacteria (SRB) pop-ulation and sulfur metabolism had been changed, which led to inhibit methane emission. How-ever, high sulfur in the diet could increase risk of inflammation of rumen epithelium.

Abstract

These experiments were conducted to evaluate the effect of excessive sulfur on rumen fermentation, microflora, and epithelial barrier function in steers through in vitro gas production and animal feeding experiments. Nine and four levels of sulfur addition were evaluated in in vitro ruminal fermentation and animal feeding experiment, respectively. The results showed that increasing the level of sulfur in substrates decreased the total gas and methane production linearly, while increasing the production of hydrogen sulfide gas (p < 0.01). Volatile fatty acid concentrations, especially that of butyric acid, were increased by extra sulfur (p < 0.01). Sulfur content in the diet had no significant effect (p > 0.05) on most of the rumen microbes, except for Desulfovibrio, one of the major sulfate-reducing bacteria (SRB) in the rumen, whose population increased by adding extra sulfur (p < 0.001). The changes in the morphology of rumen epithelium and thickening of the total epithelial layer were mainly attributed to the increase in the acanthosis cell layer and stratum basale (p < 0.05). Further, the relative expressions of two tight junction protein regulating genes, CLDN-1 and TJP1, were reduced (p < 0.05). Excessive sulfur in the diet can change the type of rumen fermentation, sulfate metabolism and SRB population, and the rumen epithelial barrier function. The results of this study demonstrated that sulfur can be used as a methane inhibitor with the mechanism that SRB competitively used protons to produce hydrogen sulfide. However, a higher level of sulfur in the diet could increase the inflammatory reaction of the rumen epithelium which may affect nutrient absorption.

Effect of Tea Tree Oil on the Expression of Genes Involved in the Innate Immune System in Goat Rumen Epithelial Cells

Simple Summary

Subacute rumen acidosis (SARA) often causes significant losses on commercial farms. SARA is mainly caused by endotoxin (LPS) produced by the lysis of Gram-negative bacteria, which causes an inflammatory response. To alleviate the inflammatory response mediated by LPS, it is important to improve animal production performance. Tea tree oil (TTO) is a plant extract that possesses good bactericidal and anti-inflammatory effects. According to this study, LPS can significantly induce inflammatory responses in goat rumen epithelial cells (GRECs), while the addition of TTO could markedly mitigate inflammatory responses mediated by LPS in GRECs. Therefore, it may be useful for the treatment of SARA.

Abstract

In subacute rumen acidosis (SARA), the rumen epithelium is frequently attacked by endotoxin (LPS), which is caused by the lysis of dead Gram-negative bacteria. However, the rumen epithelium innate immune system can actively respond to the infection. Previous studies have demonstrated that tea tree oil (TTO) has good bactericidal and anti-inflammatory effects. Therefore, the aim of this study was to investigate the effect of TTO on the expression of genes involved in the inflammatory cytokines in goat rumen epithelial cells (GRECs) triggered by LPS. Our study shows that rumen epithelial cells isolated from goat rumen tissue can be cultured in vitro in 0.25% trypsin for a long time. These cells were identified as epithelial cells by the expression of cytokeratin 18, monocarboxylate transporter 4 (MCT4), Na[+]/H[+] hydrogen exchanger 1 (NHE1), putative anion transporter 1 (PAT1), vH⁺ ATPase B subunit (vH⁺ ATPase), and anion exchanger 2 (AE2). The mRNA expression of IL-1β, IL-6, TNF-α, TLR-2, NF-κB, CXCL6 and CXCL8 genes was significantly increased when LPS was used compared to untreated controls. In addition, mRNA expression of IL-1β, IL-6, TNF-α, TLR-2, NF-κB, CXCL8, CXCL6 and interferon-induced protein with tetratricopeptide repeats 3 (IFIT3) genes was also significantly higher in the LPS group compared to the 0.05% TTO group. However, the expression of IL-1β, IL-6, TNF-α, TLR-2, CXCL6 and IFIT3 genes was significantly lower in the LPS and 0.05% TTO group compared to the 1 μg/mL LPS group. These results suggest that TTO can inhibit LPS-induced inflammatory cytokines expression in GRECs.

Identification of Genomic Regions Influencing N-Metabolism and N-Excretion in Lactating Holstein- Friesians

Excreted nitrogen (N) of dairy cows contribute to environmental eutrophication. The main N-excretory metabolite of dairy cows is urea, which is synthesized as a result of N-metabolization in the liver and is excreted via milk and urine. Genetic variation in milk urea (MU) has been postulated but the complex physiology behind the trait as well as the tremendous diversity of processes regulating the N-metabolism impede the consistent determination of causal regions in the bovine genome. In order to map the genetic determinants affecting N-excretion, MU and eight other N-excretory metabolites in milk and urine were assessed in a genome-wide association study. Therefore phenotypes of 371 Holstein- Friesians were obtained in a trial on a dairy farm under near commercial conditions. Genotype data comprised SNP information of the Bovine 50K MD Genome chip (45,613 SNPs). Significantly associated genomic regions for MU concentration revealed GJA1 (BTA 9), RXFP1, and FRY1 (both BTA 12) as putative candidates. For milk urea yield (MUY) a promising QTL on BTA 17 including SH3D19 emerged, whereas RCAN2, CLIC5, ENPP4, and ENPP5 (BTA 23) are suggested to influence urinary urea concentration. Minor N-fractions in milk (MN) may be regulated by ELF2 and SLC7A11 (BTA 17), whilst ITPR2 and MYBPC1 (BTA 5), STIM2 (BTA 6), SGCD (BTA 7), SLC6A2 (BTA 18), TMCC2 and MFSD4A (BTA 16) are suggested to have an impact on various non-urea-N (NUN) fractions excreted via urine. Our results highlight genomic regions and candidate genes for N-excretory metabolites and provide a deeper insight into the predisposed component to regulate the N-metabolism in dairy cows.

Potential protective effects of thiamine supplementation on the ruminal epithelium damage during subacute ruminal acidosis

In ruminants, the ruminal epithelium not only has the function of absorbing nutrients but also is an important tissue to prevent harmful substances in the rumen from entering the blood circulation. Thus, the normal function of ruminal epithelium is critical for ruminants. However, subacute ruminal acidosis induced by high-concentrate diets often damages the barrier function of ruminal epithelium in ruminants. Recently, many studies have shown that dietary supplementation with thiamine is an effective method to alleviate subacute ruminal acidosis. In order to provide theoretical reference for the in-depth study of subacute ruminal acidosis and the application of thiamine in the future, this review introduces the effects of subacute ruminal acidosis on morphological structure, inflammatory response, and tight junction of ruminal epithelium. In addition, this paper summarizes the role of thiamine in maintaining ruminal epithelial function of ruminants during subacute ruminal acidosis challenge.

Transcriptome analysis reveals the effect of high-grain pelleted and non-pelleted diets on ruminal epithelium of Hu-lamb

High-grain non-pelleted (HG) and high-grain pelleted (HP) diets are becoming prevalent for ruminant feeding in intensive farms. However, rare information is about their effect on sheep and the comparison between these two kinds of diets. The current study investigated how HG and HP diets affected the transcriptome profiles of rumen epithelium in Hu-lamb. Fifteen male Hu-lambs were assigned randomly to three groups (n = 5 for each group). Lambs in the control (CON), HG, and HP groups were fed with low-grain non-pelleted diet (30% grain), HG diet (70% grain), and HP diet (70% grain), respectively, for 42 days. All these lambs were slaughtered to collect ruminal epithelium samples for transcriptome analysis. Results showed both HG and HP diets obviously changed the transcriptome profiles, and 192, 319, and three differentially expressed genes (DEGs) were identified for CON_HG, CON_HP, and HG_HP comparisons, respectively. Clusters of orthologous group functional classification of CON_HG and CON_HP DEG datasets both showed the enrichments of DEGs in pathways involved in protein biogenesis and modification as well as energy production and conversion. Kyoto encyclopedia of genes and genomes pathway analysis of CON_HG and CON_HP DEG datasets both displayed the enrichments of DEGs in ribosome and oxidative phosphorylation. Almost all these DEGs involved in translation and ribosomal structure and biogenesis as well as oxidative phosphorylation were downregulated in the HG and HP groups compared to the CON group. Furthermore, CON_HP comparison demonstrated more DEGs related to these two pathways than CON_HG comparison. In conclusion, both HG and HP diets inhibited energy production and conversion as well as protein synthesis and modification in ruminal epithelium. HP diet showed lower growth benefits, induced severer rumen acidosis, and more seriously inhibited energy production and protein synthesis as compared to HG diet.

Thiamine Alleviates High-Concentrate-Diet-Induced Oxidative Stress, Apoptosis, and Protects the Rumen Epithelial Barrier Function in Goats

High-concentrate diets are continually used in ruminants to meet the needs of milk yield, which can lead to the occurrence of subacute rumen acidosis in ruminants. This study investigated the protective effects of dietary thiamine supplementation on the damage of the ruminal epithelium barrier function in goats fed a high-concentrate diet. Twenty-four healthy Boer goats (live weight of 35.62 ± 2.4 kg; age, 1 year) were randomly assigned into three treatments, with eight goats in each treatment, consuming one of three diets: a low-concentrate diet (CON; concentrate/forage, 30:70), a high-concentrate diet (HC; concentrate/forage, 70:30), or a high-concentrate diet with 200 mg of thiamine/kg of dry matter intake (HCT; concentrate/forage, 70:30) for 12 weeks. The additional dose of thiamine was based on our previous study wherein thiamine ameliorates inflammation. Compared with HC treatment, the HCT treatment had markedly higher concentrations of glutathione, superoxide dismutase, and glutathione peroxidase and total antioxidant capacity (P < 0.05) in plasma and rumen epithelium. The results showed that the apoptosis index was lower (P < 0.05) in the HCT treatment than in that of the HC treatment. Compared with the HC treatment, permeability and the electrophysiology parameter short circuit current for ruminal epithelial tissue were significantly decreased (P < 0.05) in the HCT treatment. The immunohistochemical results showed that the expression distribution of tight junctions including claudin-1, claudin-4, occludin, and zonula occludin-1 (ZO-1) was greater (P < 0.05) in the HCT treatments than in the HC treatment. The mRNA expression in the rumen epithelium of ZO-1, occludin, claudin-1, B-cell lymphoma/leukemia 2, nuclear factor erythroid-2 related factor 2 (Nrf2), superoxide dismutase 2 (SOD2), glutathione peroxidase 1, and the phase II metabolizing enzymes quinone oxidoreductase and heme oxygenase in the HCT group was significantly increased in comparison with the HC diet treatment (P < 0.05), whereas the mRNA expression of caspase 3, caspase 8, caspase 9, bcl-2 associated X protein, lipopolysaccharide binding protein, toll-like receptor 4, nuclear factor kappa-B (NFκB), tumor necrosis factor alpha, interleukin-1β, interleukin, and tumor necrosis factor receptor-associated factor 6 decreased significantly in the HCT treatment (P < 0.05). Compared with the HC treatment, the HCT diet significantly increased the protein expression of ZO-1, occludin, claudin-1, NQO1, HO-1, SOD2, serine/threonine kinase, p-Akt, Nrf2, and p-Nrf2; conversely, the expression of NFκB-related proteins p65 and pp65 was significantly decreased (P < 0.05). In addition, thiamine relieved the damage on the ruminal epithelium caused by the HC diet. The results show that dietary thiamine supplementation improves the rumen epithelial barrier function by regulating Nrf2-NFκB signaling pathways during high-concentrate-diet feeding.

Milk urea nitrogen variation explained by differences in urea transport into the gastrointestinal tract in lactating dairy cows

Milk urea nitrogen (MUN) and blood urea nitrogen are correlated with nitrogen balance and nitrogen excretion; however, there is also a genetic component to MUN concentrations that could be associated with differences in urea transport. It was hypothesized that a portion of the variation in MUN concentrations among cows is caused by variation in gastrointestinal and kidney urea clearance rates. Eight lactating cows with varying MUN concentrations while fed a common diet were infused with [¹⁵N¹⁵N]urea to determine urea N entry rate (UER), gastrointestinal entry rate, returned to ornithine cycle, urea N used for anabolism, urea N excretion in feces and urine. Urea clearance rates by the kidneys and gastrointestinal tract were calculated from isotopic enrichment of urea excretion in urine and gut entry rate, respectively, and plasma urea N concentrations (PUN). Over the course of the experiment, animals weighed an average of 506 ± 62 kg and produced 26.3 ± 4.39 kg of milk/d, with MUN concentrations ranging from 11.6 to 17.3 mg/dL (average of 14.9 ± 2.1 mg/dL). Plasma urea N was positively correlated with UER, urea N excretion in urine, and urea N used for anabolism. Plasma urea N and MUN were negatively correlated with gut clearance rates and ratio of gastrointestinal entry rate to UER. This relationship supports the hypothesis that differences in gut urea transport activity among animals causes variation in PUN and MUN concentrations, and that cows with high PUN and MUN are less efficient at recycling PUN to the gastrointestinal tract and thus may be more susceptible to ruminal N deficiencies when fed low RDP diets. Such biological variation in urea metabolism necessitates an adequate safety margin when setting regulations for maximal MUN levels as an indicator of herd N efficiency.

Impact of Zinc and/or Herbal Mixture on Ruminal Fermentation, Microbiota, and Histopathology in Lambs

We investigated the effect of diets containing organic zinc and a mixture of medicinal herbs on ruminal microbial fermentation and histopathology in lambs. Twenty-eight lambs were divided into four groups: unsupplemented animals (Control), animals supplemented with organic zinc (Zn, 70 mg Zn/kg diet), animals supplemented with a mixture of dry medicinal herbs (Herbs, 100 g dry matter (DM)/d) and animals supplemented with both zinc and herbs (Zn+Herbs). Each lamb was fed a basal diet composed of meadow hay (700 g DM/d) and barley (300 g DM/d). The herbs Fumaria officinalis L. (FO), Malva sylvestris L. (MS), Artemisia absinthium L. (AA) and Matricaria chamomilla L. (MC) were mixed in equal proportions. The lambs were slaughtered after 70 d. The ruminal contents were used to determine the parameters of fermentation in vitro and in vivo and to quantify the microbes by molecular and microscopic methods. Samples of fresh ruminal tissue were used for histopathological evaluation. Quantitative analyses of the bioactive compounds in FO, MS, AA, and MC identified 3.961, 0.654, 6.482, and 12.084 g/kg DM phenolic acids and 12.211, 6.479, 0.349, and 2.442 g/kg DM flavonoids, respectively. The alkaloid content in FO was 6.015 g/kg DM. The diets affected the levels of total gas, methane and n-butyrate in vitro (P < 0.046, < 0.001, and < 0.001, respectively). Relative quantification by real-time PCR indicated a lower total ruminal bacterial population in the lambs in the Zn and Zn+Herbs groups than the Control group (P < 0.05). The relative abundances of Ruminococcus albus, R. flavefaciens, Streptococcus bovis, and Butyrivibrio proteoclasticus shifted in the Zn group. Morphological observation found a focally mixed infiltration of inflammatory cells in the lamina propria of the rumen in the Zn+Herbs group. The effect of the organic zinc and the herbal mixture on the parameters of ruminal fermentation in vitro was not confirmed in vivo, perhaps because the ruminal microbiota of the lambs adapted to the zinc-supplemented diets. Long-term supplementation of a diet combining zinc and medicinal herbs, however, may negatively affect the health of the ruminal epithelium of lambs.

Effects of subacute ruminal acidosis on colon epithelial morphological structure, permeability, and expression of key tight junction proteins in dairy goats

The hindgut epithelial barrier plays an important role in maintaining absorption and immune homeostasis in ruminants. However, little information is available on changes in colon epithelial barrier structure and function following grain-induced subacute ruminal acidosis (SARA). The objective of this study was to investigate the effects of grain-induced SARA on colon epithelial morphological structure, permeability, and gene expression involved in epithelial barrier function. Twelve mid-lactating (136 ± 2 d in milk; milk yield = 1.68 ± 0.15 kg/d) Saanen dairy goats with 62.13 ± 4.76 kg of body weight were randomly divided into either the control (CON) treatment (n = 6) or SARA treatment (n = 6). The CON goats were fed a basal diet with a nonfiber carbohydrates to neutral detergent fiber ratio of 1.15 for 60 d. The SARA goats were fed 4 diets with increasing nonfiber carbohydrates to neutral detergent fiber ratio at 1.15, 1.49, 2.12, and 2.66 to induce SARA, with each diet (referred to as period) being fed for 15 d, including 12 d for adaptation and 3 d for sampling. Continuous ruminal pH recordings were used to diagnose the severity of SARA. Additionally, colonic tissues were collected to evaluate the epithelial morphological structure, permeability, and expression of tight junction proteins using transmission electron microscopy, Ussing chamber, quantitative real-time PCR, and Western blotting. Profound disruption in the colonic epithelium was mainly manifested as the electron density of tight junctions decreased, intercellular space widened, and mitochondria swelled in SARA goats. Colon epithelial short-circuit current, tissue conductance, and the mucosal-to-serosal flux of fluorescein isothiocyanate-dextran 4 kDa were increased and potential difference was decreased in SARA goats compared with CON goats. Subacute ruminal acidosis increased mRNA and protein expression levels of CLDN1 and OCLN in the colonic epithelium. Overall, the data of the present study demonstrate that SARA can impair the barrier function of the colonic epithelium at both structural and functional levels, which is associated with severe epithelial structural damage and increased permeability and changes in the expression of tight junction proteins.

Effects of a proinflammatory response on metabolic function of cultured, primary ruminal epithelial cells

Inflammation of ruminal epithelium may occur during ruminal acidosis as a result of translocation and interaction of ruminal epithelial cells (REC) with molecules such as lipopolysaccharide (LPS). Such inflammation has been reported to alter cellular processes such as nutrient absorption, metabolic regulation, and energy substrate utilization in other cell types but has not been investigated for REC. The objectives of this study were to investigate the effects of LPS on metabolism of short-chain fatty acids by primary REC, as well as investigating the effects of media containing short-chain fatty acids on the proinflammatory response. Ruminal papillae from 9 yearling Speckle Park beef heifers were used to isolate and culture primary REC. Cells were grown in minimum essential medium (MEM) for 12 d before use and then reseeded in 24-well culture plates. The study was conducted as a 2 × 2 factorial, where cells were grown in unaltered MEM (REG) or medium containing 2 mM butyrate and 5 mM propionate (SCFA) with (50,000 EU/mL; +LPS) or without LPS (-LPS) for 24 h. Supernatant samples were collected for analysis of glucose and SCFA consumption. Cells were collected to determine the expression of mRNA for genes associated with inflammation (TNF, IL1B, CXCL2, CXCL8, PTGS2, and TLR4), purinergic signaling (P2RX7, ADORAB2, and CD73), nutrient transport [SLC16A1 (MCT1), SLC16A3 (MCT4), SLC5A8, and MCU], and cell metabolism [ACAT1, SLC2A1 (GLUT1), IGFBP3, and IGFBP5]. Protein expression of TLR4 and ketogenic enzymes (BDH1 and HMGCS1) were also analyzed using flow cytometry. Statistical analysis was conducted with the MIXED model of SAS version 9.4 (SAS Institute Inc., Cary, NC) with medium, LPS exposure, and medium × LPS interaction as fixed effects and animal within plate as a random effect. Cells tended to consume more glucose when exposed to LPS as opposed to no LPS exposure (31.8 vs. 28.7 ± 2.7), but consumption of propionate and butyrate was not influenced by LPS. Expression of TNF and IL1B was upregulated when exposed to LPS, and expression of CXCL2 and CXCL8 increased following LPS exposure with SCFA (medium × LPS). For cells exposed to LPS, we found a downregulation of ACAT1 and IGFBP5 and an upregulation of SLC2A1, SLC16A3, MCU, and IGFBP3. Medium with SCFA led to greater expression of MCU. SLC16A1 was upregulated in cells incubated with SCFA and without LPS compared with the other groups. Protein expression of ketogenic enzymes was not affected; however, BDH1 mean fluorescence intensity (MFI) expression tended to be less in cells exposed to LPS. These data are interpreted to indicate that when REC are exposed to LPS, they may increase glucose metabolism. Moreover, transport of solutes was affected by SCFA in the medium and by exposure to LPS. Overall, the results suggest that metabolic function of REC in vitro is altered by a proinflammatory response, which may lead to a greater glucose requirement.