Yeast β-glucan alleviates the subacute rumen acidosis-induced mitochondrial dysfunction and cell structure integrity injury in yak rumen epithelial cells via the TLR2/PI3K/mTOR signaling pathway

Subacute rumen acidosis (SARA) is characterized by decreased rumen fluid pH and impaired rumen epithelial function. In this study, the underlying molecular mechanisms of β-glucan can alleviate SARA induced damage to yak rumen epithelial cells (YRECs), and its potential protective effects were investigated. The results demonstrated that β-glucan alleviated the decrease in cell viability and LDH release induced by SARA. Furthermore, SARA led to mitochondrial dysfunction, including disrupted mitochondrial morphology observed through fluorescence and transmission electron microscopy, decreased mitochondrial membrane potential and ATP levels, increased intracellular Ca2+ and reactive oxygen species levels, reduced activity of glutathione metabolism-related enzymes in the antioxidant system, and inhibited expression of oxidative phosphorylation-related genes and proteins. Additionally, SARA disrupted the expression of cell cytoskeleton and cell junction genes and proteins. Meanwhile, SARA induced a cellular inflammatory response, inhibited ion channel transport, activated acid-sensitive receptors, and disrupted intracellular acid-base balance. The cells were pre-treatment with β-glucan significantly mitigated these adverse effects, maintaining normal cellular functions. The specific inhibitors Dactolisib and rapamycin, which target and inhibit the PI3K/mTOR signaling pathway, reversed the effects of β-glucan in regulating the impact of SARA on the signaling pathway. The downstream mTOR signaling pathway inhibitor rapamycin reversed the effects of β-glucan in mitigating SARA-induced disruptions in mitochondrial and cell cytoskeleton functions. In conclusion, in vitro findings suggest that yeast β-glucan potentially regulates SARA-induced effects on mitochondrial function, cell cytoskeleton, and cell junctions by inhibiting acid-sensitive receptors and activating TLR2/PI3K/mTOR signaling pathway.

Transcriptomic profiling of gastrointestinal tracts in dairy cattle during lactation reveals molecular adaptations for milk synthesis

During lactation, dairy cattle's digestive tract requires significant adaptations to meet the increased nutrient demands for milk production. As we attempt to improve milk-related traits through selective pressure, it is crucial to understand the biological functions of the epithelia of the rumen, small intestine, and colonic tissues in response to changes in physiological state driven by changes in nutrient demands for milk synthesis. In this study, we obtained a total of 108 transcriptome profiles from three tissues (epithelia of the colon, duodenum, and rumen) of five Holstein cows, spanning eight time points from the early, mid, late lactation periods to the dry period. On average 97.06% of reads were successfully mapped to the reference genome assembly ARS-UCD1.2. We analyzed 27,607 gene expression patterns at multiple periods, enabling direct comparisons within and among tissues during different lactation stages, including early and peak lactation. We identified 1645, 813, and 2187 stage-specific genes in the colon, duodenum, and rumen, respectively, which were enriched for common or specific biological functions among different tissues. Time series analysis categorized the expressed genes within each tissue into four clusters. Furthermore, when the three tissues were analyzed collectively, 36 clusters of similarly expressed genes were identified. By integrating other comprehensive approaches such as gene co-expression analyses, functional enrichment, and cell type deconvolution, we gained profound insights into cattle lactation, revealing tissue-specific characteristics of the gastrointestinal tract and shedding light on the intricate molecular adaptations involved in nutrient absorption, immune regulation, and cellular processes for milk synthesis during lactation.

Associations of rumen and rectum bacteria with the sustained productive performance of dairy cows

The gut bacterial community is essential for maintaining lifelong health and productivity in ruminants, but the relationship between the gut microbiota and the sustained productivity of ruminants remains inadequately understood. In this study, we selected long-lived dairy cows in mid-lactation (≥5 parities) with different levels of milk production (n = 10). Significant differences were observed in the rumen bacterial structures between the two groups of dairy cows, whereas no significant differences were detected in the rectum bacterial communities. Additionally, there were no significant differences in serum oxidative stress biomarkers, inflammatory markers, or immunological markers between the long-lived high-yield (LH) and long-lived low-yield (LL) dairy cows. Furthermore, the concentrations of propionate (Pr) in the rumen and butyrate (Bu) in the rectum were elevated in the high-yield group. Spearman correlation and microbial co-occurrence network analyses revealed that several rumen-enriched bacteria, such as Syntrophococcus, Lachnospira, Shuttleworthia, Erysipelotrichaceae_UCG-2, and Roseburiaare associated with rumen propionate (Pr) production. In the rectum, the reduced abundance of Christensenellaceae_R-7_group and Moryella favors butyrate production. Furthermore, Random Forest machine learning analysis demonstrated that six bacterial taxa in the rumen combined with one serum biomarker, as well as three bacterial taxa in the rectum combined with three serum biomarkers, can serve as potential biomarkers for distinguishing between LH and long- LL dairy cows, achieving prediction accuracies of 92 and 99%, respectively. The findings of this study indicate that rumen and rectum bacteria are associated with the milk production phenotypes of dairy cows with sustained productivity. The rumen microbes are closely linked to the long-term productive capacity of dairy cows and represent a key target for the development of gut microbiota-based interventions. The unique bacterial communities of the rumen and rectum of long-lived high-yielding dairy cows contribute to maintaining their productive capacity.

Short-term effects of subacute ruminal acidosis on ferroptosis and iron metabolism in the livers of lactating sheep fed a high-grain diet

Subacute ruminal acidosis can cause liver injury in ruminants. Ferroptosis, an iron-dependent cell death, is involved in many liver diseases. This study aimed to investigate ferroptosis in SARA-induced liver injury and explore the changes in hepatic iron metabolism. Twelve ruminally cannulated, lactating Hu sheep (parity: 2 or 3; BW: 50.6 ± 4.0 kg; 18.8 ± 3.6 DIM; MY: 0.52 ± 0.08 kg/d; mean ± SD) were divided into 2 groups (n = 6/group) and fed a low-grain diet (LG; grain/forage ratio = 3:7, 24.89% starch and 40.66% NDF) or a high-grain diet (HG; grain/forage ratio = 7:3, 38.64% starch and 24.41% NDF) for 8 wk. Rumen pH was measured weekly 10 min before feeding and 1, 2, 3, 4, 5, 6, and 8 h after feeding. On d 57, all sheep were slaughtered after collecting hepatic vein blood, and liver tissue was collected. The HG diet significantly decreased rumen pH compared with the LG diet; the rumen pH on d 56 in the HG group was <5.6 at 1, 2, 3, and 4 h after feeding. Plasma concentrations of LPS, malondialdehyde (MDA), IL-1β, and IL-6 at 4 h after feeding increased, whereas glutathione (GSH) and glutathione peroxidase 4 (GPX4) decreased. Moreover, lipid reactive oxygen species, ferrous ion, and MDA were elevated, whereas GSH was decreased in the liver of the HG group. For ferroptosis-related proteins, feeding a high-grain diet led to increased acyl-CoA synthetase long chain family member 4 (ACSL4) and arachidonate 15-lipoxygenase (ALOX15) and decreased GPX4 and solute carrier family 7 member 11 (SLC7A11). For ferritinophagy-related proteins, feeding a high-grain diet decreased ferritin heavy chain 1 (FTH1) and increased nuclear receptor coactivator 4 (NCOA4) and microtubule-associated protein 1 light chain 3 II (MAP1LC3-II). Regarding iron metabolism, increased protein expression of nuclear mothers against decapentaplegic homolog1/5/8 (SMAD1/5/8) and hepcidin, decreased protein expression of ferroportin, and iron deposits were observed in the liver of the HG group. Furthermore, feeding high-grain diets also increased inflammatory signaling-related proteins IL-6 and phospho-signal transducer and activator of transcription 3 (p-STAT3). Taken together, this study suggests that SARA induced liver injury and ferroptosis. Enhanced ferritinophagy, disordered iron metabolism, and elevated inflammatory response may mediate ferroptosis in the livers of sheep fed a high-grain diet.

Quercetin alleviates LPS/iE-DAP-induced liver injury by suppressing ferroptosis via regulating ferritinophagy and intracellular iron efflux

Ruminal dysbiosis-induced liver injury is prevalent in dairy cows, yet its underlying mechanisms remain incompletely understood. Ferroptosis, a newly identified form of programmed cell death distinct from apoptosis and necrosis, has been implicated in various liver diseases by emerging studies. In the present study, lipopolysaccharide (LPS) and γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP) were employed to establish in vitro and in vivo models of liver injury using bovine hepatocytes and mice, respectively. It was observed that noncytotoxic iE-DAP alone did not influence lipid peroxidation or GPX4, but exacerbated LPS-induced ferroptosis and hepatocyte injury. Notably, co-treatment with LPS and iE-DAP (LPS/iE-DAP)-induced hepatocyte injury was mitigated by intervention with the ferroptosis inhibitor ferrostatin-1 (Fer-1). Mechanistically, the activated IL-6/STAT3 signaling pathway was found to mediate LPS/iE-DAP-induced ferroptosis. Suppression of IL-6/STAT3, either through IL6 and STAT3 knockdown or pharmacological intervention, reduced Fe2+ accumulation and alleviated ferroptotic cell death. Further investigations identified that IL-6/STAT3 signaling enhanced ferritinophagy and impaired iron export. Either disrupting ferritinophagy by knocking down NCOA4 or restoring iron export via HAMP knockdown relieved intracellular iron overload and inhibited ferroptosis. Specifically, LPS/iE-DAP treatment increased the interaction between hepcidin and ferroportin, promoting ferroportin ubiquitination and degradation, thereby blocking iron efflux. Furthermore, we provided several evidence to prove that quercetin pretreatment alleviated LPS/iE-DAP-induced ferroptosis and liver injury by decreasing hepatic iron accumulation via targeting the IL-6/STAT3 signaling in vitro and in vivo, effects reversed by the addition of recombinant bovine IL-6. Based on these findings, we concluded that LPS/iE-DAP-induced liver injury by triggering ferroptosis through regulating IL-6/STAT3/ferritinophagy-dependent iron release and IL-6/STAT3/hepcidin/ferroportin-dependent iron export, while quercetin could alleviate this liver injury by inhibiting ferroptosis via IL-6/STAT3 signaling pathway. This study provides novel insights into the mechanisms whereby ruminal dysbiosis induces liver injury and presents a prospective solution for ruminal dysbiosis-induced liver injury.

Multi-omics analysis of the mechanism of alfalfa and wheat-induced rumen flatulence in Xizang sheep

Rumen flatulence is a diet-related rumen disease in ruminants. This study induced a rumen flatulence model in Xizang sheep using alfalfa (HRF) and wheatgrass (MRF). The aim was to understand the rumen microbiota diversity in healthy and pathological states, host-microbiota interactions, and the molecular mechanisms of rumen flatulence. Results showed that the pH in the HRF and MRF groups was lower than that in the natural grass group (LRF). SCFA concentrations varied between groups: in HRF, 2-BA and CA increased; in MRF, 4-MVA and 5-MCA rose. Microbial analysis indicated that the alpha- and beta-diversity of HRF and MRF groups were lower than LRF's, with different microbial compositions. Transcriptome analysis revealed many differentially expressed genes (DEGs). Compared to MRF, HRF had 348 upregulated and 511 downregulated DEGs. Versus LRF, MRF had 201 upregulated and 185 downregulated DEGs, while HRF had 128 upregulated and 238 downregulated DEGs. Spearman's correlation analysis showed that there was a positive correlation between Butyrivibrio, Quinella, and specific genes. These findings reveal the potential mechanism of rumen flatulence in Xizang sheep and provide new insights into the prevention and treatment of the disease.IMPORTANCEThe research used a high-protein diet to induce a model to understand the diversity of rumen microbiota and its interaction with the host, as well as exploring the molecular mechanisms of rumen flatulence.

Recent nutritional strategies and feed additives to stimulate proper rumen development in young goats

Domestic goats (Capra aegagrus hircus) are important producers of milk, meat, and hair. The early weaned goats may face fundamental issues related to the incomplete rumen development to deal with the transition from liquid feeds into solid feeds. Therefore, the present review focuses on the nutritional strategies and feeding methods to enhance the proper rumen morphological development, fermentation efficiency and microbiota structure in young goats. The enhanced rumen development caused by these nutritional strategies can have lasting positive effects on their overall growth performance and health status, leading to decreasing mortality rates and susceptibility to disease after weaning. A wide range of areas was summarized including liquid feed management in preweaning goats (colostrum, milk, and milk replacer), solid feed management (concentrate and roughages), endogenous and exogenous volatile fatty acids and ketones, plant extracts, prebiotics and probiotics as well as rumen microbial contents that can be incorporated into the kids as an alternative to antibiotics to avoid pathogens and enhance the proper establishment of microbial community. Such nutritional strategies and current breeding recommendations can be used for the development of young goats' production systems to enhance the long-term digestive function efficiency in goats.

Ruminal-buccal microbiota transmission and their diagnostic roles in subacute rumen acidosis in dairy goats

BACKGROUND

Subacute rumen acidosis (SARA) is a common metabolic disorder in ruminants that disrupts the rumen microbiome and animal health, but diagnosis is challenging due to subtle symptoms and invasive testing requirements. This study explores the potential of the buccal (oral) microbiome as a diagnostic indicator for SARA, hypothesizing an interaction with the rumen microbiome.

RESULTS

The study involved 47 dairy goats, including 11 on a control diet and 36 on high-concentrate diets with increasing rumen-degradable starch. Animals were grouped based on dietary exposure and ruminal pH: Control, Low-RDS Tolerance/SARA (LRDST/LRDSS), and High-RDS Tolerance/SARA (HRDST/HRDSS). Transcriptomics of rumen epithelium showed heightened inflammatory pathway gene expression in SARA-susceptible goats compared to controls and tolerant groups. Alpha diversity of ruminal bacteria showed lower Shannon diversity in HRDSS goats compared to HRDST whereas buccal bacteria displayed significantly lower Chao1 diversity in LRDSS goats compared to HRDST. Beta diversity analyses revealed distinct patterns between SARA-affected goats and healthy controls in both ruminal and buccal microbiomes. Prevotellaceae_UCG-003 emerged as a candidate biomarker, with reduced abundance in SARA-susceptible goats in both rumen and buccal samples. Machine learning classifiers achieved high accuracy in distinguishing SARA-susceptible goats using this genus (rumen AUC = 0.807; buccal AUC = 0.779). Source tracking analysis illustrated diminished cross-population of bacteria from the buccal to rumen (2.86% to 0.25%) and vice versa (8.59% to 1.17%), signifying compromised microbial interchange in SARA-affected goats. A microbiota transplant experiment verified SARA microbiota's ability to induce pH decline, escalate inflammation-related gene expression (MAPK10, IL17B, FOSB, SPP1), disrupt microbial transfer, and reduce Prevotellaceae_UCG-003 in recipients.

CONCLUSION

Our findings highlight SARA's dual impact on ruminal and buccal microbiota, exacerbating epithelial inflammation gene expression. Shifts in the buccal microbiome, specifically reductions in Prevotellaceae_UCG-003, mirror ruminal changes and can be influenced by inter-compartmental bacterial transmission, thereby offering a non-invasive diagnostic approach for SARA.

Transcriptomics insights into glutamine on repairing of histamine-induced Yak rumen epithelial cells barrier damage in vitro

BACKGROUND

Glutamine (Gln) plays a pivotal role in maintaining the integrity of the rumen epithelial barrier in mammals. This study aimed to investigate the effects of Gln on histamine-induced barrier damage in yak rumen epithelial cells (YRECs).

RESULTS

RT-qPCR analysis revealed a significant decrease in the mRNA expression of tight junction proteins (ZO-1, JAM-A, Claudin-1, and Claudin-4) following 24-hour exposure to 20 µM histamine (HIS group) (P < 0.05). In the subsequent experiment, YRECs were first treated with 20 µM histamine for 24 h, followed by 8 mM glutamine for 12 h (HG group). Gln treatment reversed the histamine-induced downregulation of both mRNA and protein levels of tight junction proteins and restored the distribution of ZO-1 at the cell membrane. Transcriptome analysis revealed that co-regulated differentially expressed genes were primarily involved in the mitogen-activated protein kinase (MAPK) signaling pathway and apoptosis. These findings were further corroborated by RT-qPCR, Western blot, and flow cytometry analyses. To determine whether glutamine regulates cell barrier function through the p38 MAPK signaling pathway, 20 µM Skatole, a p38 MAPK agonist, was introduced (SK group). The results showed a significant increase in the p-p38/p38 ratio and a marked decrease in the mRNA and protein expression of tight junction proteins in the SK group compared to the HG group (P < 0.05).

CONCLUSIONS

Glutamine mitigates histamine-induced barrier damage in YRECs through the p38 MAPK signaling pathway and apoptosis regulation.

Invited Review: Inflammation and Health in the Transition Period Influence Reproductive Function in Dairy Cows

In the early postpartum period, dairy cows undergo significant adaptations in Ca and lipid metabolism, immune function, and inflammatory processes. Concurrent exposure to endotoxins from the uterus, gastrointestinal tract, or mammary gland increases the risk of disease and reproductive problems. Metabolic and inflammatory imbalances during this phase can have both immediate and long-term effects on reproductive health. Associations between metabolic disorders and reproductive outcomes are often confounded by immune activation and systemic inflammation. However, optimal markers, thresholds, and durations for identifying maladaptation and predicting adverse health or reproductive outcomes remain unclear. This narrative review examines key physiological changes during the transition period, including hypocalcemia, lipid mobilization, immune activation, systemic inflammation, and uterine disease. We discuss how these events may affect the dominant follicle, corpus luteum, oocyte, and uterus, potentially leading to prolonged anovulation, reduced estrus expression, impaired response to synchronization protocols, lower progesterone concentrations, and compromised fertility. Understanding these mechanisms will support the development of strategies to monitor, prevent, and mitigate the impacts of transition-related maladaptation on reproductive performance. Such advancements can enhance the health and fertility of high-producing dairy cows.

A resource of longitudinal RNA-seq data of Holstein cow rumen, duodenum, and colon epithelial cells during the lactation cycle

OBJECTIVE

As one of the most important ruminant breeds, Holstein cattle supply a significant portion of milk and dairy for human consumption, playing a crucial role in agribusiness. The goal of our study was to examine the molecular adaptation of gastrointestinal tissues that facilitate milk synthesis in dairy cattle. DATA DESCRIPTION: We performed RNA-seq analysis on epithelial cells from the rumen, duodenum, and colon at eight different time points: Days 3, 14, 28, 45, 120, 220, and 305 in milk, as well as the dry period. Samples were taken from five multiparous dairy cows as biological replicates per tissue per stage, except for Days 14 and 28, for which the sample size was three. These tissues each serve critical and distinct roles in the digestion and absorption of nutrients and are all vital for providing the necessary substrates required for milk production. Understanding the intricate connections between the tissues involved in providing nutrients necessary to support milk synthesis and their role in digestion can deepen the understanding of lactation physiology. This resource aims to deliver in-depth insights into cattle lactation, highlighting the distinct traits of gastrointestinal tissues and illuminating the intricate transcriptomic dynamics throughout the lactation period.

Identification of transcriptional regulators and signaling pathways mediating postnatal rumen growth and functional maturation in cattle

The rumen plays an essential role in the physiology and health of ruminants. The rumen undergoes substantial changes in size and function from birth to adulthood. The cellular and molecular mechanisms underlying these changes are not clear. This study aimed to identify the transcription factors (TFs) and signaling pathways mediating these changes in cattle. We found that the ratios of the emptied rumen, reticulum, omasum, and abomasum to body weight in adult steers were 4.8 (P < 0.01), 3.1 (P < 0.01), 6.0 (P < 0.01), and 0.8 (P = 0.9) times those in neonatal calves, respectively. The length of rumen papillae and the thickness of rumen epithelium, tunica mucosa and submucosa, tunica muscularis, and tunica serosa increased 7.4-, 2.0-, 3.0-, 2.9-, and 4.6-fold (P < 0.01 for all), respectively, from neonatal calves to adult steers. However, the density of rumen papillae was lower in adult steers than in neonatal calves (P < 0.05). The size of rumen epithelial cells was not different between neonatal calves and adult steers (P = 0.57). RNA sequencing identified 2,922 genes differentially expressed in the rumen between neonatal calves and adult steers. Functional enrichment analyses revealed that organ development, blood vessel development, Ras signaling, and Wnt signaling were among the functional terms enriched in genes downregulated in adult steers vs. neonatal calves and that fatty acid metabolism, immune responses, PPAR signaling, and Rap1 signaling were among those enriched in genes upregulated in adult steers vs. neonatal calves. Serum response factor (SRF), interferon regulatory factor 4, and purine-rich single-stranded DNA-binding protein alpha were among the major candidate TFs controlling the expression of genes upregulated, while TCF4, inhibitor of DNA binding 4, and snail family transcriptional repressor 2 were among those controlling the expression of genes downregulated in adult steers vs. neonatal calves. Taken together, these results suggest that the rumen grows by increasing the number, not the size, of cells from birth to adulthood, that the absorptive, metabolic, immune, and motility functions of the rumen are acquired or significantly enhanced during the postnatal life, and that the changes in rumen size and function from birth to adulthood are mediated by many candidate TFs, including SRF and TCF4, and many candidate signaling pathways, including the PPAR and Wnt signaling pathways.

Invited review: Ruminal acidosis and its definition-A critical review

Ruminal acidosis occurs as a continuum of disorders, stemming from ruminal dysbiosis and disorders of metabolism, of varying severity. The condition has a marked temporal dynamic expression, resulting in cases expressing quite different rumen concentrations of VFA, lactic acid, ammonia, and rumen pH over time. Clinical ruminal acidosis is an important condition of cattle and subclinical ruminal acidosis (SRA) is very prevalent in many dairy populations, with estimates between 10% and 26% of cows in early lactation. Estimates of the duration of a case suggest that the lactational incidence of the condition may be as high as 500 cases per 100 cows in the first 100 d of lactation. Historical confusion about the etiology and pathogenesis of ruminal acidosis led to definitions that are not fit for purpose, as acidic ruminal conditions solely characterized by ruminal pH determination at a single point fail to reflect the complexity of the condition. Use of a model based on integrated ruminal measures, including VFA, ammonia, lactic acid, and pH, for evaluating ruminal acidosis is fit for purpose, as indicated by meeting postulates for assessing metabolic disease, but requires a method to simplify application in the field. Although it is likely that this model, which we have termed the Bramley acidosis model (BAM), will be refined, the critical value in the model is that it demonstrates that ruminal acidosis is much more than ruminal pH. Disease, milk yield, and milk composition are more associated with the BAM than rumen pH alone. Two single VFA, propionate and valerate, are sensitive and specific for SRA, especially when compared with rumen pH. Even with the use of such a model, astute evaluations of the condition, whether in experimental or field circumstances, will be aided by ancillary measures that can be used in parallel or in series to enhance diagnosis and interpretation. Sensing methods, including rumination detection, behavior, milk analysis, and passive analysis of rumen function, have the potential to improve the detection of SRA; however, these may advance more rapidly if SRA is defined more broadly than by ruminal pH alone.

Microbial dysbiosis in the gut–mammary axis as a mechanism for mastitis in dairy cows

Mastitis is a significant and costly disease in dairy cows, reducing milk production and affecting herd health. Recent research highlights the role of gastrointestinal microbial dysbiosis in the development of mastitis. This review focuses on how microbial imbalances in the rumen and intestines can compromise the integrity of the gastrointestinal barriers, allowing harmful bacteria and endotoxins, such as lipopolysaccharide, to enter the bloodstream and reach the mammary gland, triggering inflammation. This process links gastrointestinal health to mammary gland inflammation through the gut–mammary axis. Furthermore, disruptions in glucose metabolism and immune responses are implicated in the progression of mastitis. This review underscores the potential for non‐antibiotic interventions aimed at restoring microbial balance to reduce mastitis incidence, providing new insights into improving dairy cow health and farm productivity. Our findings emphasise the critical need to explore preventive measures targeting the rumen and intestinal microbiota for effective mastitis control.

Multi-omics analysis reveals the effects of host-rumen microbiota interactions on growth performance in a goat model

The growth rate of young ruminants has been associated with production performance in later life, with recent studies highlighting the importance of rumen microbes in supporting the health and growth of ruminants. However, the specific role of rumen epithelium bacteria and microbiota-host interactions in influencing the early life growth rate of ruminants remains poorly understood. In this study, we investigated the rumen fermentation pattern, microbiota characteristics, and global gene expression profiles of the rumen epithelium in 6-month-old goats with varying growth rates. Our results showed that goats with high average daily gain (HADG) exhibited higher rumen propionate concentrations. Goats with low average daily gain (LADG) had the higher relative abundances of rumen epithelium bacteria genera U29-B03 and Quinella, while exhibiting a lower relative abundance of Lachnospiraceae UCG-009. In the rumen fluid, the relative abundances of bacteria genus Alloprevotella were lower and Desulfovibrio were higher in LADG goats compared to HADG goats. Additionally, the relative abundance of fungal genus Symmetrospora was lower in LADG goats compared to HADG goats. Transcriptome analysis showed that 415 genes were differentially expressed between LADG and HADG goats, which were enriched in functions related to cell junction and cell adhesion, etc. Correlation analysis revealed that rumen epithelium bacteria genera UCG-005 and Candidatus Saccharimonas were negatively associated, while Lachnospiraceae NK3A20 group and Oscillospiraceae NK4A214 group were positively associated with average daily gain (ADG) and genes related to barrier function. The rumen fluid bacteria genus Alloprevotella was positively correlated, while Desulfovibrio was negatively correlated with rumen propionate and ammoniacal nitrogen (NH3-N) concentrations, as well as genes related to barrier function and short chain fatty acids (SCFAs) transport. In summary, our study reveals that the higher ruminal fermentation efficiency, improved rumen epithelial barrier functions, and enhanced SCFAs transport in HADG goats could be attributed to the rumen microbiota, particularly the rumen epithelium bacteria, such as Lachnospiraceae and Oscillospiraceae NK4A214 group.

Pogostemon cablin essential oil as feed additive promotes the repair of the rumen epithelial barrier in heat-stressed beef cattle

Pogostemon cablin essential oil (PEO), extracted from P. cablin, has anti-oxidant, anti-inflammatory, and anti-stress properties, as well as the ability to improve gastrointestinal digestion. This study aims to evaluate the effects of PEO on the performance, rumen epithelial morphology, and barrier function in heat-stressed beef cattle. Thirty-six male Jingjiang cattle at 18 months old were randomly assigned into four groups and fed a diet containing PEO at 0 (control), 50, 100, or 150 mg/kg in the feed concentrate (n = 9). All experimental cattle were fed under high temperature and humidity in summer for 60 days. The results indicated that 50 mg/kg of PEO treatment enhanced the average daily gain of beef cattle compared with the control group (P = 0.032). All PEO treatments reduced the diamine oxidase activity (P = 0.004) and malondialdehyde content (P = 0.008) in serum. In addition, the content of 70 kDa heat shock protein in the 100 mg/kg group was increased, and the activity of glutathione peroxidase and total antioxidant capacity in both 100 mg/kg and 150 mg/kg groups were enhanced compared to the control group (P < 0.05). More importantly, PEO treatment with 50 mg/kg enhanced the mRNA relative expressions of occludin in ruminal epithelia but decreased the mRNA relative expressions of c-Jun N-terminal kinase, P38 mitogen-activated protein kinases, caspase-3, Beclin1 (P < 0.05), and extremely significant declined the mRNA relative expressions of extracellular regulated protein kinases and ubiquitin-binding protein in contrast to the control group (P < 0.01). These findings indicated that dietary PEO supplementation might be favorable to improve growth performance and repairing damaged rumen epithelium of heat-stressed cattle by down-regulating the mitogen-activated protein kinase signaling pathway.

Validation of an in vivo dual permeability marker technique to characterize regional gastrointestinal tract permeability in mid lactation Holstein cows during short-term feed restriction

This study evaluated the impact of short-term feed restriction in lactating dairy cows on regional permeability of the gastrointestinal tract (GIT), and the recovery of DMI, ruminal pH, and milk yield. In addition, sampling methods for a novel dual marker technique to characterize total GIT and post ruminal permeability were validated. Six ruminally cannulated lactating Holstein cows were blocked by parity (3 primiparous, 3 multiparous; 189 DIM ± 25.2) and enrolled in a crossover design. Experimental periods included a 5-d baseline phase (BASE), 5-d challenge phase (CHAL), and 2 weeks of recovery (REC1 and REC2). During CHAL cows received either 100% ad libitum feed intake (AL) or 40% of ad libitum feed intake (FR). To assess, total-tract and post-ruminal permeability, equimolar doses of Cr-EDTA and Co-EDTA were infused on d 3 of CHAL into the rumen and abomasum (0.369 mmol/kg BW). Following infusions, total urine and feces were collected every 8 h over 96 h, and blood samples were collected at h 0, 1, 2, 3, 4, 6, 8, 12, 16, 20, 24, 32, 40, 48, and 64. The plasma area under the curve (AUC) for Cr and Co were calculated. By design, DMI for FR was reduced by 60% during CHAL and remained 19% lower than AL during REC1 but was not different from AL in REC2. Mean ruminal pH for FR was greatest during CHAL and the least during REC1, with no differences detected between AL and FR in REC2. The duration that pH was < 5.8 was the least for FR during CHAL and greatest during REC1 which were different from AL and were no longer different between treatments in REC2. Milk yield was the least for FR during CHAL and REC1 and no longer different from AL in REC2. Feed restriction reduced milk fat, protein, and lactose yields by 26, 31% and 31%, respectively. Plasma Cr AUC was 34% greater and Co AUC tended to be 35% greater for FR than AL on d 3 of CHAL. Urinary Cr recovery after 48-h was not affected by treatment; however, urinary Co recovery was 36% greater for FR than AL. Positive correlations between plasma AUC and urinary recovery for Cr and Co were detected. It was determined that blood samples collected at h 2, 8, 20, 40, and 48 could predict the total plasma Cr and Co AUC within 1.9% and 6.2%, respectively. In summary, short-term FR in lactating dairy cows increases permeability of the total GIT and may increase permeability of the post-ruminal regions with more than 60% of the permeability occurring post-ruminally. After FR, cows experienced low ruminal pH and a sustained reduction in milk yield. When utilizing Cr- and Co-EDTA to evaluate regional GIT permeability, plasma AUC can be used as an alternate to urinary Cr and Co excretion. In addition, blood samples collected at h 2, 8, 20, 40, and 48 result in adequate prediction accuracy, at least when comparing GIT permeability for lactating dairy cows exposed to AL and FR.

Epigallocatechin-3-gallate protects bovine ruminal epithelial cells against lipopolysaccharide-induced inflammatory damage by activating autophagy

BACKGROUND

Subacute ruminal acidosis (SARA) causes an increase in endotoxin, which can induce immune and inflammatory responses in the ruminal epithelium of dairy cows. In non-ruminants, epigallocatechin-3-gallate (EGCG), a major bioactive ingredient of green tea, is well-known to alleviate inflammation. Whether EGCG confers protection against SARA-induced inflammation and the underlying mechanisms are unknown.

RESULTS

In vivo, eight ruminally cannulated Holstein cows in mid-lactation were randomly assigned to either a low-concentrate (40%) diet (CON) or a high-concentrate (60%) diet (HC) for 3 weeks to induce SARA (n = 4). Cows with SARA had greater serum concentrations of tumor necrosis factor (TNF)-α and interleukin-6, and epithelium had histological signs of damage. In vitro, immortalized bovine ruminal epithelial cells (BREC) were treated with lipopolysaccharide (LPS) to imitate the inflammatory damage caused by SARA. Our data revealed that BREC treated with 10 µg/mL LPS for 6 h successfully induce a robust inflammatory response as indicated by increased phosphorylation of IκBα and nuclear factor kappa-B (NF-κB) p65. Pre-treatment of BREC with 50 µmol/L EGCG for 6 h before LPS challenge promoted the degradation of NLR family pyrin domain containing 3 (NLRP3) inflammasome through activation of autophagy, which further repressed activation of NF-κB pathway targeting Toll-like receptor 4 (TLR4). Analyses also revealed that the ECGG upregulated tight junction (TJ) protein expression upon incubation with LPS.

CONCLUSIONS

Subacute ruminal acidosis causes ruminal epithelium injury and systemic inflammation in dairy cows. However, the anti-inflammatory effects of EGCG help preserve the integrity of the epithelial barrier through activating autophagy when BREC are exposed to LPS. Thus, EGCG could potentially serve as an effective therapeutic agent for SARA-associated inflammation.

Subacute ruminal acidosis induces pyroptosis via the mitophagy-mediated NLRP3 inflammasome activation in the livers of dairy cows fed a high-grain diet

High-grain (HG) feeding can trigger subacute ruminal acidosis (SARA) and subsequent liver tissue injury. This study investigated pyroptosis and NLRP3 inflammasome activation in SARA-induced liver injury, and the role of mitophagy during this process. Twelve mid-lactating Holstein cows equipped with rumen fistulas were randomly divided into 2 groups: a low-grain (LG) diet group (grain:forage = 4:6) and a HG diet group (grain:forage = 6:4). Each group had 6 cows. The experiment lasted for 3 wk. The ruminal fluid was collected through the rumen fistula on experimental d 20 and 21, and the pH immediately measured. At the end of the experiment, all animals were slaughtered, and peripheral blood and liver tissue were collected. The ruminal pH was lower in the HG group than that in the LG group at all time points. In addition, the ruminal pH in the HG group was lower than 5.6 at 3 consecutive time points after feeding (4, 6, and 8 h on d 20; 2, 4, and 6 h on d 21), indicating that HG feeding induced SARA. The content of lipopolysaccharide, IL-1β, and apoptosis-related cysteine protease 1 (caspase-1) and the activity of alanine aminotransferase and aspartate aminotransferase in the blood plasma of the HG group were all significantly increased. Hepatic caspase-1 activity was increased in the livers of the HG group. The increased expression levels of pyroptosis- and NLRP3 inflammasome-related genes IL1B, IL18, gasdermin D (GSDMD), apoptosis-associated speck-like protein containing a card (ASC), NLR family pyrin domain-containing 3 (NLRP3), and caspase-1 (CASP1) in liver tissue of the HG group were detected. Furthermore, western blot analysis showed that HG feeding led to increased expression of pyroptosis- and NLRP3 inflammasome-related proteins GSDMD N-terminal (GSDMD-NT), IL-1β, IL-18, cleaved-caspase-1, ASC, NLRP3, and cleaved-caspase-11 and upregulated expression of mitophagy-related proteins microtubule-associated protein 1 light chain 3 II (MAP1LC3-II), beclin 1 (BECN1), Parkin, and PTEN-induced kinase 1 (PINK1) in liver tissue. Collectively, our results revealed that SARA caused increased mitophagy and activated the NLRP3 inflammasome, causing pyroptosis and subsequent liver injury in dairy cows fed a HG diet.

Effects of prepartum concentrate feeding on reticular pH, plasma energy metabolites, acute phase proteins, and milk performance in grass silage-fed dairy cows

We investigated how concentrate feeding during the last 21 d of pregnancy affects reticular pH, inflammatory response, dry matter (DM) intake, and production performance of dairy cows. We hypothesized that adding concentrates to dairy cows' diet before calving reduces the decrease in reticular pH postpartum and thus alleviates inflammatory response. We also hypothesized that prepartum concentrate feeding increases DM intake postpartum and consequently improves milk performance. Two feeding experiments were conducted using a randomized complete block design. In each experiment, 16 multiparous Finnish Ayrshire cows were paired based on parity, expected calving date, body weight, and milk yield of the previous lactation. Within the pairs, cows were randomly allocated on one of the 2 dietary treatments 21 d before expected calving. In experiment 1 (Exp1), diets were ad libitum feeding of grass silage as a sole feed or supplemented with increasing amounts of concentrate offered separately (increased to 4 kg/d by d -7). In experiment 2 (Exp2), diets were ad libitum feeding of a total mixed ration containing either grass silage, barley straw, and rapeseed meal (64%, 28%, and 8% on DM basis, respectively) or grass silage, barley straw, and cereal-based concentrate mixture (49%, 29%, and 30% on DM basis, respectively). Following calving, all the cows were fed similarly and observed until d 56 postpartum. Feed intake and milk yield were recorded daily, and reticular pH was monitored continuously by reticular pH bolus. Blood samples were collected at the beginning of the experiments, 7 d before the expected calving date, 1 d (in Exp1) or 5 d (in Exp2), 10 d, and 21 d postpartum. In Exp1, concentrate feeding increased metabolizable energy intake and tended to increase DM and crude protein intake prepartum. Moreover, prepartum concentrate feeding increased the concentrations of plasma β-hydroxybutyrate and insulin, but differences in nonesterified fatty acids, glucose, or acute phase proteins were not observed. After calving, prepartum diet did not affect DM or nutrient intake, plasma energy metabolites, or milk production in Exp1. Although prepartum concentrate feeding increased reticular pH on the first day of lactation, it elevated plasma concentrations of serum amyloid-A and haptoglobin postpartum in the grass silage-based diet. In Exp2, adding concentrates to the diet based on a mixture of grass silage and straw did not affect prepartum DM intake or plasma concentrations of nonesterified fatty acids, glucose, or insulin. Adding concentrates to prepartum diet increased plasma concentration of β-hydroxybutyrate before calving as in Exp1. After calving, prepartum concentrate feeding increased DM and nutrient intake during the second week of lactation in Exp2, but no effects were observed thereafter. In contrast to our hypothesis, prepartum concentrate feeding decreased reticular pH after calving in Exp2, but no differences in inflammatory markers were observed. Based on this study, close-up concentrate feeding in diets based on grass silage with or without straw does not alleviate the decrease in reticular pH or mitigate inflammatory response postpartum.

Alginate Oligosaccharide Alleviates Lipopolysaccharide-Induced Apoptosis and Inflammatory Response of Rumen Epithelial Cells through NF-κB Signaling Pathway

AOS alleviates inflammatory responses; however, whether it exerts an effect on the rumen or regulates rumen inflammatory reaction remains unknown. In this study, firstly, the ovine ruminal epithelial cells (ORECs) were treated with 0, 200, 400, 600, and 800 µg/mL AOS, hoping to explore whether AOS hurt cell health. The results showed that compared with the AOS-0 group, the AOS-400 group could significantly increase (p < 0.05) cell viability, reduce (p < 0.05) reactive oxygen species (ROS) and interleukin (IL)-6 content, and have no adverse effect on cells. Secondly, we used LPS to construct an in vitro inflammatory model of rumen epithelial cells and then explored the protective role of AOS on rumen epithelial cells. The study was divided into three groups: the control group (CON), LPS, and LPS + AOS. The results demonstrated that the LPS + AOS group significantly increased the cell viability and reduced the ROS level in comparison with the LPS group (p < 0.05). Pretreatment with AOS also repressed (p < 0.05) the secretion of IL-1β, IL-6, IL-8, and immunoglobulin (Ig)A from ORECs in the culture medium following LPS. In terms of tight junction (TJ) proteins, AOS treatment also significantly increased (p < 0.05) the zonula occludens 1 (ZO-1) and Occludin expression. The apoptosis rate, Caspase3, Caspase9, BAD, and BCL-2/BAX were decreased (p < 0.05) after AOS treatment, and the expression of BCL-2 was increased (p < 0.05). In addition, the expressions of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor-κB (NF-κB) were inhibited (p < 0.05) with the addition of AOS. At the protein level, pretreatment of AOS decreased (p < 0.05) the expression of MyD88 and the phosphorylation level of inhibitor κB α (IκBα) after the LPS challenge. Taken together, our results indicated that AOS could alleviate the LPS-induced apoptosis and inflammatory response of rumen epithelial cells through the NF-κB signaling pathway, which may be a promising strategy for treating apoptosis and inflammation in sheep breeding.

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.

Acid-base properties of non-protein nitrogen affect nutrients intake, rumen fermentation and antioxidant capacity of fattening Hu sheep

This study conducted a comparison of the effects of non-protein nitrogen with different acid-base properties on feed intake, rumen fermentation, nutrient digestion and antioxidant capacity in fattening Hu sheep. Sixteen fattening male sheep (31.43 ± 2.41 kg) with permanent rumen cannulas were randomly assigned to two dietary treatments: 1% urea and 1.78% ammonium chloride (NH4Cl, AC). A 42 days experimental period was conducted, with 14 days for adaptation and 28 days for treatment. Daily feed intake was recorded and various samples including feed, feces, rumen fluid, and blood were collected at different time points during the final week. The results indicated that the urea group had significantly higher dry matter intake, average daily gain, and gain efficiency in comparison to the AC group (p < 0.01). There was no difference in rumen pH and concentration of ammonia nitrogen between different groups (p > 0.05), but the rumen pH of urea group was higher than that of the AC group at 1 and 3 h after feeding (p < 0.05). The urea group exhibited higher concentrations of total volatile fatty acids (VFA) and individual VFAs compared to the AC group at all-time points (p < 0.01). Compared to the urea group, the intake of all nutrients decreased in the AC group (p < 0.01), but the digestibility of dry matter and organic matter increased significantly (p < 0.01), and the digestibility of CP had an increasing trend (p = 0.06) in the AC group. Additionally, the urea group had lower levels of serum glucagon-like peptide-1, peptide YY, Cl, total protein and globulin than the AC group (p < 0.05). The overall levels of HCO3-, superoxide dismutase, glutathione peroxidase, catalase, albumin/globulin, blood urea nitrogen and total cholesterol in the urea group increased significantly compared to the AC group (p < 0.05). It was concluded that adding urea to the high-concentrate diet resulted in increased rumen pH and improved rumen fermentation and growth performance in fattening sheep compared to NH4Cl addition. Furthermore, urea addition improved sheep's antioxidant capacity and maintained their acid-base balance more effectively as compared to NH4Cl.

Effects of ruminal lipopolysaccharide exposure on primary bovine ruminal epithelial cells

The objective of this study was to investigate the immunopotential of ruminal lipopolysaccharides (LPS) on cultured primary bovine rumen epithelial cells (REC). Primary bovine REC were isolated from 6 yearling steers and grown in culture for 3 experiments. Experiment 1 aimed to determine the immunopotential of ruminal LPS, experiment 2 aimed to assess tolerance to chronic LPS exposure, and experiment 3 aimed to evaluate antagonistic interactions between ruminal and Escherichia coli LPS. In experiments 1 and 2, REC were exposed to nonpyrogenic water, 20 μg/mL E. coli LPS (EC20), 10 μg/mL ruminal LPS, 20 μg/mL ruminal LPS, and 40 μg/mL ruminal LPS, either continuously or intermittently. For the continuous exposure, REC underwent a 6 h exposure, whereas for the intermittent exposure, the procedure was: (1) a 12 h continuous exposure to treatments followed by LPS removal for 24 h and then another 12 h of exposure (RPT), and (2) a 12 h continuous exposure to treatments followed by LPS removal and a recovery period of 36 h (RCV). In experiment 3, REC were exposed to nonpyrogenic water, 1 μg/mL E. coli LPS, 1 μg/mL ruminal LPS to 1 μg/mL E. coli LPS, 10 μg/mL ruminal LPS to 1 μg/mL E. coli LPS, and 50 μg/mL ruminal LPS to 1 μg/mL E. coli LPS. Each experiment was done as a complete randomized block design with 6 REC donors. The REC-donor was used as blocking factor. Each treatment had 2 technical replicates, and treatment responses for all data were analyzed with the MIXED procedure of SAS. For all experiments, total RNA was extracted from REC and real-time quantitative PCR was performed to determine the relative expression of genes for toll-like receptors (TLR2 and TLR4), proinflammatory cytokines (TNF, IL1B, and IL6), chemokines (CXCL2 and CXCL8), growth factor-like cytokines (CSF2 and TGFB1), and a lipid mediator (PTGS2). In experiment 1, the targeted genes were upregulated by EC20, whereas all ruminal LPS treatments resulted in a lower transcript abundance. Regarding RPT, and RCV condition, in experiment 2, the expression of targeted genes was not affected or was at a lower abundance to EC20 when compared with ruminal LPS treatments. Lastly, in experiment 3, all targeted genes resulted in lower or similar transcript abundance on all ruminal LPS ratios. Overall, our results indicate that ruminal LPS have a limited capacity to activate the TLR4/NF-kB pathway and to induce the expression of inflammatory genes.

Characterization of a model of hindgut acidosis in mid-lactation cows: A pilot study

The objective of this pilot study was to generate data to support the development of an experimental model of hindgut acidosis to further understand its systemic consequences independently of rumen acidosis. Four ruminally fistulated multiparous Holstein cows (213 ± 11 d in milk) were subjected to 2 consecutive experimental periods (P1 and P2), separated by a 3-d washout. Experimental periods were 96 h long from the baseline to the final measurements but expanded over 5 calendar days (d 0-4). Abomasal infusions of saline and corn starch (2.8 kg/d) were performed for the first 72 h (d 0-3) of P1 and P2, respectively. Final measurements were performed 24 h after the end of the infusions (d 4). Each cow was used as its own control by comparing P2 to P1. Postruminal-intestinal permeability was assessed by Cr appearance in blood after a pulse dose administration of Cr-EDTA into the abomasum on d 2 (48 h after infusion initiation) of each period. Starch infusion during P2 was associated with a milk protein yield increase (3.3%) and a decrease in milk urea nitrogen (11%). Fecal dry matter increased (8.8%), and starch content tended to increase (∼2 fold) during P2. There was a period-by-day interaction for fecal pH as it decreased during starch infusion (1.3 pH points) but remained constant during P1. Although fecal lactate was not detectable during P1, it consistently increased during starch infusion. Fecal alkaline phosphatase activity also increased (∼17 fold) in association with starch infusion. Two hours after Cr-EDTA administration, blood Cr concentration was higher during starch infusion, resulting in a tendency for a treatment-by-hour interaction. Furthermore, blood d-lactate increased (∼2.5 fold), serum Cu decreased (18%), and blood urea nitrogen, cholesterol, and Ca tended to decrease (9.4%, 1.2%, and 2.4%, respectively), relative to P1. The current results suggest that hindgut acidosis was successfully induced by postruminal starch infusion, leading to gut damage and increased intestinal permeability. However, indications of systemic inflammation were not observed. The herein described preliminary results will require confirmation in a properly powered study.

Protective Effects of Niacin on Rumen Epithelial Cell Barrier Integrity in Heat-Stressed Beef Cattle

The present study investigates the theoretical basis for maintaining normal physiological functions in heat-stressed beef cattle by exploring the effects of niacin supplementation on the permeability of the rumen epithelial cell barrier. Herein, 12 Jinjiang bulls with an average weight of approximately 400 ± 20.0 kg were randomly divided into three groups, thermoneutral (TN), heat-stressed (HS), and heat-stressed niacin-supplemented (HN) groups, with 4 bulls in each group. The experiment spanned 70 days, and the plasma concentrations of D-lactic acid, diamine oxidase (DAO), lipopolysaccharides (LPSs), and inflammatory cytokines were analyzed. Additionally, we assessed the gene expression of tight junction proteins to understand the effect of niacin supplementation on heat-stressed beef cattle. Our results revealed that heat stress significantly increased the D-lactic acid and LPS levels in beef cattle plasma on days 30 and 45 of the experiment (p < 0.05). Moreover, it led to a significant rise in DAO levels on day 30 (p < 0.05). Niacin supplementation significantly reduced the LPS levels on day 30 (p < 0.05). Heat stress significantly elevated the plasma concentrations of inflammatory cytokines interleukin-1β (IL-1β), IL-2, IL-6, and tumor necrosis factor-α (TNF-α) (p < 0.05), while reducing the IL-4 concentration (p < 0.05). However, niacin supplementation effectively mitigated the concentrations of these inflammatory factors by reducing IL-1β, IL-2, IL-6, and TNF-α concentrations and increasing IL-4 concentrations. The mRNA expressions of tight junction proteins zonula occluden-1 (ZO-1), claudin-1, claudin-4, and claudin-7 were significantly downregulated (p < 0.05) in the HS group compared to those in the TN group, and those of ZO-1 and occludin were significantly upregulated (p < 0.05) in the HN group compared to those in the HS group. Notably, no significant differences were observed in ruminal papillae length and width among the studied groups (p > 0.05). Our findings indicate that heat stress adversely impacted the tight junction structure of the rumen epithelium, leading to a significant reduction in the expression of tight junction protein mRNA. Consequently, heat stress impaired the rumen mucosal barrier function, resulting in increased intestinal permeability. The mechanism underlying this effect may be associated with the decreased expression of tight junction protein genes in the rumen epithelial cells. However, niacin supplementation mitigated the detrimental effects of heat stress on intestinal permeability in beef cattle and increased the expression of tight junction protein genes in the rumen epithelium, thereby effectively protecting the rumen barrier in heat-stressed beef cattle. These results highlight the potential of nicotinic acid as a protective agent against the negative impacts of heat stress on intestinal integrity in beef cattle.

Elucidating the factors and consequences of the severity of rumen acidosis in first-lactation Holstein cows during transition and early lactation

First-lactation cows are particularly prone to subacute ruminal acidosis (SARA) during transition. Besides common risk factors of SARA, such as feeding of starch-rich diets, an individual severity of SARA in cows has been recently evidenced. Yet, the factors that play a role in SARA severity have not been elucidated. The main goal of this research was to evaluate the factors of SARA severity in first-lactation cows during transition and early lactation, which go beyond high-grain feeding, and to explore their impact on behavior, health, and fermentation in the rumen and hindgut. Twenty-four first-lactation Holstein cows with the same feeding regime were used starting from 3 wk before the expected calving day until 10 wk postpartum. Cows received a close-up diet (32% concentrate) until calving and were then transitioned to a lactation diet (60% concentrate) within 1 week. The SARA severity was assessed by cluster analysis of several rumen pH metrics, which revealed exceptionally longer and more severe SARA in cows denominated as high (n = 9), as compared to moderate (n = 9) and low (n = 6) SARA severity cows (P < 0.01). The logistic analysis showed that the length of close-up feeding, age at parturition, and the level of dry matter intake (DMI) were the main factors that influenced the cows' odds for high SARA severity (each P ≤ 0.01). Moreover, the ANOVA hinted differences in the metabolic activity of the ruminal microbiome to promote SARA severity, as indicated by highest ruminal propionate proportions (P = 0.05) in high SARA severity cows, also with similar DMI. The distinct SARA severity was marginally reflected in behavior and there were no effects of SARA severity or high-grain feeding on blood inflammation markers, which peaked at parturition regardless of SARA severity (P < 0.01). Still, ongoing high-grain feeding increased liver enzyme concentrations from 6 wk postpartum on, compared to weeks before (P < 0.01), yet irrespectively of SARA severity. In conclusion, first-lactation cows differed in SARA severity under the same feeding regime, which was ascribed to management factors and differences in ruminal fermentation. Further research is warranted to validate these findings and to understand the mechanisms behind differences in the metabolic function of rumen microbiome, in particular in terms of evaluating markers for various SARA severity, as well as to evaluate potential long-term effects on health, performance, fertility, and longevity of dairy cows.

Effects of a Bacillus-based direct-fed microbial on performance, blood parameters, fecal characteristics, rumen morphometrics, and intestinal gene expression in finishing beef bulls

We evaluated the effects of supplementing direct-fed microbials (DFM), containing Bacillus licheniformis and Bacillus subtilis, on performance, rumen morphometrics, intestinal gene expression, and blood and fecal parameters in finishing bulls. Nellore × Angus bulls (n = 144; initial BW = 401 ± 45.5 kg) were distributed at random in 36 pens (4 bulls/pen and 18 pens/treatment), following a completely randomized design. A ground corn-based finishing diet was offered for ad libitum intake twice a day for 84 d, containing the following treatments: 1) control (without DFM); 2) DFM (B. licheniformis and B. subtilis) at 6.4 × 109 CFU (2 g) per animal. The data were analyzed using the MIXED procedure of SAS, with a pen representing an experimental unit, the fixed effect of the treatment, and the random effect of pen nested within the treatment. For fecal parameters (two collections made), the collection effect and its interaction with the treatment were included in the model. Bulls that received the DFM had a decreased dry matter intake (P ≤ 0.01), did not differ in average daily gain (2.05 kg; P = 0.39), and had a 6% improvement in gain:feed (P = 0.05). The other performance variables, final BW, hot carcass weight, and hot carcass yield, did not differ (P > 0.10). Plasma urea-N concentration decreased by 6.2% (P = 0.02) in the bulls that received DFM. Glucose, haptoglobin, and lipopolysaccharides were not different between treatments (P > 0.10). Ruminal morphometrics were not affected by the treatment (P > 0.10). The use of DFM tended to reduce fecal starch (P = 0.10). At slaughter, bulls fed DFM had an increased duodenal gene expression of tryptophan hydroxylase-1 (P = 0.02) and of superoxide dismutase-1 (P = 0.03). Overall, supplementation with DFM based on B. licheniformis and B. subtilis to Nellore × Angus bulls in the finishing phase decreased dry matter intake, did not influence ADG, improved gain:feed, and increased the expression of genes important for duodenal function.

Impact of maternal live yeast supplementation to sows on intestinal inflammatory cytokine expression and tight junction proteins in suckling and weanling piglets

Recent studies have highlighted the importance of maternal nutrition during gestation and lactation in modulating the gastrointestinal development and health of offspring. Therefore, the objective of this study was to determine the effects of live yeast (LY) supplementation to sows during late gestation and throughout lactation on markers of gut health of piglets prior to weaning and immediately postweaning. On day 77 of gestation, forty sows were allotted based on parity and expected farrowing dates to two dietary treatments: without (CON) or with (LY) supplementation at 0.05% and 0.1% of diet during gestation and lactation, respectively. On postnatal days (PND) 0, 10, 18, and postweaning days (PWD) 7 and 14, one piglet from each of 10 sows per treatment were selected for intestinal tissue collection (n = 10). Real-time PCR and western blotting analyses were used to determine the mucosal expression of immune and antioxidant-regulatory genes and tight junction markers of gut health in the duodenum, jejunum, and ileum. Inflammatory and tight junction markers on PND 0 were not affected by maternal dietary treatment. On PND 18, maternal LY supplementation increased (P < 0.05) mRNA expression of interleukin (IL)-6 and tended (P = 0.08) to increase expression of IL-10 in the ileal muocsa. Maternal LY supplementation also increased (P < 0.05) expression of IL-1β in the ileal mucosa on PWD 14. Likewise, expression of superoxide dismutase (SOD) 1 was increased (P < 0.05) by LY on PND 10, 18, and PWD 14, with a tendency (P = 0.09) for a greater mRNA abundance of catalase on PND 14 in the ileal mucosa. Compared to CON piglets, LY piglets had a higher (P < 0.05) protein abundance of E-cadherin in the jejunal mucosa on PND 0, PWD 7, and PWD 14. Levels of occludin and claudin-4 were also higher (P < 0.05) in the jejunum of LY piglets on PWD 14. No differences were found in jejunal histomorphological measurements between treatments. In conclusion, this study shows that maternal LY supplementation affects key markers of gut health and development in the offspring that may impact the future growth potential and health of newborn piglets.

The roles of short-chain fatty acids derived from colonic bacteria fermentation of non-digestible carbohydrates and exogenous forms in ameliorating intestinal mucosal immunity of young ruminants

Short-chain fatty acids (SCFA) are a class of organic fatty acids that consist of 1 to 6 carbons in length. They are primary end-products which arise from non-digestible carbohydrates (NDC) fermentation of colonic bacteria. They are the fundamental energy sources for post-weaning ruminants. SCFA represent the major carbon flux of diet through the gut microbiota to the host. They also play a vital role in regulating cell expansion and gene expression of the gastrointestinal tract (GIT). Recently, remarkable progresses have been made in understanding the immunomodulatory effects of SCFA and their interactions with the host. The processes involved in this study encompassed inflammasome activation, proliferation of lymphocytes, and maturation of intestinal mucosal immunity maturation. It is important to note that the establishment and maturation of intestinal mucosal immune system are intricately connected to the barrier function of intestinal epithelial cells (IEC) and the homeostasis of gut microbiota. Thus, insights into the role of SCFA in enteric mucosal immunoreaction of calves will enhance our understanding of their various regulatory functions. This review aims to analyze recent evidence on the role of SCFA as essential signaling molecules between gut microbiota and animal health. Additionally, we provide a summary of current literature on SCFA in intestinal mucosal immune responses of dairy calves.

A high-concentrate diet induces colonic inflammation and barrier damage in Hu sheep

Long-term feeding of a high-concentrate diet can induce subacute ruminal acidosis (SARA) in ruminants, which further leads to systemic inflammatory response. However, few studies have examined the effects of feeding a high-concentrate diet on the hindgut of ruminants. The purpose of this study was to investigate the effects of a high-concentrate diet on the composition of gut microbiota in colonic contents, inflammatory response, and barrier damage in the colon tissue of ruminants. A total of 12 healthy multiparous lactating Hu sheep were randomly allotted into the following 2 groups: a high-concentrate (HC) group (concentrate:forage = 7:3) and a low-concentrate (LC) group (concentrate:forage = 3:7). All sheep were fitted with ruminal fistulas. The formal feeding experiment lasted for 8 wk. After the feeding experiment, rumen fluid, portal vein blood, hepatic vein blood, colonic contents, and colon tissue samples were collected. The results showed that feeding the HC diet induced SARA in Hu sheep and significantly reduced pH in the colonic contents. The abundances of Firmicutes, Verrucomicrobiota, and Actinobacteriota decreased significantly, whereas those of Bacteroidota, Spirochaetota, and Fibrobacterota significantly increased in colonic contents. At the genus level, the relative abundances of 29 genera were significantly altered depending on the different type of diets. Analysis of the 10 bacterial genera with high relative abundance revealed that feeding the HC diet significantly reduced the abundance of UCG-005, Christensenellaceae R-7 group, UCG-010-norank, Monoglobus, [Eubacterium] coprostanoligenes group_norank, and Alistipes, whereas the abundances of Rikenellaceae RC9 gut group, Treponema, Bacteroides, and Prevotella increased. Compared with the LC group, feeding the HC diet significantly increased the concentration of LPS in rumen fluid, portal vein blood, hepatic vein blood, and colonic contents, and significantly upregulated the mRNA expression levels of proinflammatory cytokines in colon tissue, including TNF-α, IL-1β, IL-6, and IL-8, indicating the occurrence of inflammatory response in the colon tissue. In addition, the structure of colonic epithelial cells was loose, the intercellular space became larger, epithelial cells were exfoliated, and the mRNA and protein abundances of ZO-1, occludin, claudin-1, claudin-3, and claudin-4 were significantly decreased in the HC group, which was consistent with the results of immunohistochemistry. Furthermore, feeding the HC diet increased the ratios of DNA methylation and chromatin compaction in the promoter regions of occludin and claudin-1, which in turn inhibited their transcriptional expression. Therefore, the present study demonstrated that feeding an HC diet induced SARA in Hu sheep, altered the composition and structure of the microbial community in the colonic contents, induced an inflammatory response, and disrupted the intestinal mucosal barrier in the colonic tissue.

Retinoic acid ameliorates low-grade endotoxemia-induced mastitis by limiting inflammatory responses in mice

Mastitis is a serious disease for humans and animals, which causes huge economic losses in the dairy industry and is hard to prevent due to the complex and unclear pathogenesis. Subacute ruminal acidosis (SARA) has contributed to the development of mastitis by inducing ruminal dysbiosis and subsequent low-grade endotoxemia (LGE), however, how ruminal metabolic changes regulate this progress is still unclear. Our previous study revealed that cows with SARA had increased ruminal retinoic acid (RA) levels, a metabolic intermediate of vitamin A that plays an essential role in mucosal immune responses. Hence, the aim of this study was to investigate the protective effect of RA on LGE-induced mastitis and the underlying mechanisms in mice. The results showed that RA alleviated LGE-induced mastitis, as evidenced by RA significantly reduced the increase in mammary proinflammatory cytokines and improved blood-milk barrier injury caused by LGE. In addition, RA increased the expression of tight junction proteins, including ZO-1, occludin and claudin-3. Furthermore, we found that RA limited the mammary inflammatory responses by inhibiting the activation of NF-κB and NLRP3 signaling pathways. These findings suggest that RA effectively alleviates LGE-induced mastitis and implies a potential strategy for the treatment and prevention of mastitis and other diseases.

Use of milk proteins as biomarkers of changes in the rumen metaproteome of Holstein cows fed low-fiber, high-starch diets

Dietary levels of undegraded neutral detergent fiber (uNDF240) and rumen-fermentable starch (RFS) can affect the rumen microbiome and milk composition. The objective of the study is to investigate the use of milk proteins as biomarkers of rumen microbial activity through a comparative evaluation of the rumen microbial and milk protein profiles produced by Holstein cows fed diets with varying contents of physically effective uNDF240 (peuNDF240) and RFS. Eight ruminally cannulated lactating Holstein cows were included in a larger study as part of a 4 × 4 Latin square design with 4 28-d periods to assess 4 diets varying in peuNDF240 and RFS content. For this experiment, cows received one of 2 dietary treatments: (1) low-peuNDF240, high-RFS (LNHR) diet or (2) high-peuNDF240, low-RFS (HNLR) diet. Within each period, rumen fluid samples were collected from each cow on d 26 (1400 h) and d 27 (0600 h and 1000 h), and milk samples were collected from each cow on d 25 (2030 h), d 26 (0430 h, 1230 h, and 2030 h), and d 27 (0430 h and 1230 h). Microbial proteins were isolated from each rumen fluid sample. For milk samples, milk proteins were fractionated, and the whey fraction was subsequently isolated. Isolated proteins within each rumen fluid or milk sample were isobarically labeled and analyzed by liquid chromatography-tandem mass spectrometry. Product ion spectra acquired from rumen fluid samples were searched using SEQUEST against 71 composite databases. In contrast, product ion spectra acquired from milk samples were searched against the Bos taurus database. Data were analyzed using the PROC MIXED procedure in SAS 9.4 to assess the effect of diet and time of sampling. To increase stringency, the false discovery rate-adjusted P-value (PFDR) was also calculated to account for multiple comparisons. Using the mixed procedure, a total of 129 rumen microbial proteins were quantified across 24 searched microbial species. Of these, the abundance of 14 proteins across 9 microbial species was affected due to diet and diet × time interaction, including 7 proteins associated with energetics pathways. Among the 159 quantified milk proteins, the abundance of 21 proteins was affected due to the diet and diet × time interaction. The abundance of 19 of these milk proteins was affected due to diet × time interactions. Of these, 16 proteins had the disparity across diets at the 0430 h sampling time, including proteins involved in host defense, nutrient synthesis, and transportation, suggesting that biological shifts resulting from diet-induced rumen changes are not diurnally uniform across milkings. The concentration of lipoprotein lipase (LPL) was statistically higher in the milk from the cows fed with the LNHR diet, which was numerically confirmed with an ELISA. Further, as determined by ELISA, the LPL concentration was significantly higher in the milk from the cows fed with the LNHR diet at 0430 h sampling point, suggesting that LPL concentration may indicate dietary carbohydrate-induced ruminal changes. The results of this study suggest that diet-induced rumen changes can be reflected in milk in a diurnal pattern, further highlighting the need to consider sampling time points for using milk proteins as a representative biomarker of rumen microbial activity.

Unraveling the Genetic Basis of Feed Efficiency in Cattle through Integrated DNA Methylation and CattleGTEx Analysis

Feed costs can amount to 75 percent of the total overhead cost of raising cows for milk production. Meanwhile, the livestock industry is considered a significant contributor to global climate change due to the production of greenhouse gas emissions, such as methane. Indeed, the genetic basis of feed efficiency (FE) is of great interest to the animal research community. Here, we explore the epigenetic basis of FE to provide base knowledge for the development of genomic tools to improve FE in cattle. The methylation level of 37,554 CpG sites was quantified using a mammalian methylation array (HorvathMammalMethylChip40) for 48 Holstein cows with extreme residual feed intake (RFI). We identified 421 CpG sites related to 287 genes that were associated with RFI, several of which were previously associated with feeding or digestion issues. Activator of transcription and developmental regulation (AUTS2) is associated with digestive disorders in humans, while glycerol-3-phosphate dehydrogenase 2 (GPD2) encodes a protein on the inner mitochondrial membrane, which can regulate glucose utilization and fatty acid and triglyceride synthesis. The extensive expression and co-expression of these genes across diverse tissues indicate the complex regulation of FE in cattle. Our study provides insight into the epigenetic basis of RFI and gene targets to improve FE in dairy cattle.

Astragalus additive in feed improved serum immune function, rumen fermentation and the microbiota structure of early-weaned lambs

AIM

The purpose of this study was to determine the mechanism of Astragalus activity on the immune function, rumen microbiota structure, and rumen fermentation of early-weaned lambs.

METHODS AND RESULTS

Thirty healthy early-weaned lambs with similar body weights (17.42 ± 2.02 kg) were selected for the feeding experiment. The control group (KB) was fed a basal diet, and the Astragalus group (HQ) was fed 0.3% Astragalus additive on the basis of a basic diet. The formal trial period was 60 days. The results showed that the concentrations of blood immunoglobulin A (IgA) and immunoglobulin M (IgM) in the HQ group were significantly higher than those in the KB group (P < 0.05). Compared with the KB group, the concentrations of acetic acid, butyric acid, and total volatile fatty acids (VFAs) in the HQ group were higher (P < 0.01). The expression levels of the rumen epithelial-related genes MCT1, MCT4, NHE2, and ZO1 in the Astragalus group were significantly higher than those in the KB group (P < 0.05). 16S rRNA analysis showed that at the phylum level, Bacteroidetes in the HQ group significantly increased (P < 0.01); at the genus level, Prevotella (P < 0.01) and Succiniclasticum (P < 0.01) in the HQ group were found at significantly higher abundances than those in the KB group, and the results of microbiota gene and function prediction showed that "energy metabolism," "glycan biosynthesis and metabolic" pathways were significantly enriched in the HQ group (P < 0.05).

CONCLUSION

As a feed additive, Astragalus can improve the immunity of early-weaned lambs, the structure of the rumen microbiota of lambs, and the fermentation capacity of the rumen.

Immunomodulation by cannabidiol in bovine primary ruminal epithelial cells

BACKGROUND

Ruminant livestock experience a number of challenges, including high concentrate diets, weaning and transport, which can increase their risk of disorders such as ruminal acidosis, and the associated inflammation of the ruminal epithelium. Cannabidiol (CBD), a phytochemical from hemp (Cannabis sativa), is a promising target as a therapy for gastrointestinal inflammation, and may be extremely valuable as either a treatment or prophylactic. However, the effects of CBD in the the ruminant gastrointestinal tract have not been explored, in part due to the restrictions on feeding hemp to livestock. Therefore, the objective of this study was to investigate the immunomodulatory properties of CBD using a model of inflammation in primary ruminal epithelial cells (REC). In addition, CBD dose was evaluated for possible cytotoxic effects.

RESULTS

Negative effects on cell viability were not observed when REC were exposed to 10 μM CBD. However, when the dose was increased to 50 μM for 24 h, there was a significant cytotoxic effect. When 10 μM CBD was added to culture media as treatment for inflammation induced with lipopolysaccharide (LPS), expression of genes encoding for pro-inflammatory cytokine IL1B was less compared to LPS exposure alone, and CBD resulted in a down-regulation of IL6. As a pre-treatment, prior to LPS exposure, REC had decreased expression of IL6 and CXCL10 while CBD was present in the media, but not when it was removed prior to addition of LPS.

CONCLUSIONS

Results suggest that CBD may reduce cytokine transcription both during LPS-induced inflammation and when used preventatively, although these effects were dependent on its continued presence in the culture media. Overall, these experiments provide evidence of an immunomodulatory effect by CBD during a pro-inflammatory response in primary REC in culture.

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.

Effect of sodium concentration and mucosal pH on apical uptake of acetate and butyrate, and barrier function of the isolated bovine ruminal epithelium

This study was conducted to investigate the role of Na+ on ruminal short-chain fatty acid (SCFA) absorption and barrier function when isolated ruminal epithelium was exposed to high and low pH ex vivo. Nine Holstein steer calves (322 ± 50.9 kg of body weight) consuming 7.05 ± 1.5 kg dry matter of a total mixed ration were euthanized and ruminal tissue was collected from the caudal-dorsal blind sac. Tissues were mounted between 2 halves of Ussing chambers (3.14 cm2) and exposed to buffers that contained low (10 mM) or high (140 mM) Na+ with low (6.2) or high (7.4) mucosal pH. The same buffer solutions were used on the serosal side except that pH was maintained at 7.4. Buffers used to evaluate SCFA uptake contained bicarbonate to determine total uptake or excluded bicarbonate and included nitrate to determine noninhibitable uptake. Bicarbonate-dependent uptake was calculated as the difference between the total and noninhibitable uptake. Acetate (25 mM) and butyrate (25 mM) were spiked with 2-3H-acetate and 1-14C-butyrate, respectively, and were then added to the mucosal side, incubated for 1 min, and tissues were analyzed to evaluate rates of SCFA uptake. Tissue conductance (Gt) and the mucosal-to-serosal flux of 1-3H-mannitol were used to assess barrier function. There were no Na+ × pH interactions for butyrate or acetate uptake. Decreasing mucosal pH from 7.4 to 6.2 increased total acetate and butyrate uptake, and bicarbonate-dependent acetate uptake. Flux of 1-3H-mannitol was not affected by treatment. However, high Na+ concentration reduced Gt and prevented an increase in Gt from flux period 1 to flux period 2. The results of this study indicate that although providing more Na+ to the ruminal epithelium does not affect SCFA uptake or mannitol flux, it may help stabilize tissue integrity.

Multi-Omics Reveals the Impact of Exogenous Short-Chain Fatty Acid Infusion on Rumen Homeostasis: Insights into Crosstalk between the Microbiome and the Epithelium in a Goat Model

Emerging data have underscored the significance of exogenous supplementation of butyrate in the regulation of rumen development and homeostasis. However, the effects of other short-chain fatty acids (SCFAs), such as acetate or propionate, has received comparatively less attention, and the consequences of extensive exogenous SCFA infusion remain largely unknown. In our study, we conducted a comprehensive investigation by infusion of three SCFAs to examine their respective roles in regulating the rumen microbiome, metabolism, and epithelium homeostasis. Data demonstrated that the infusion of sodium acetate (SA) increased rumen index while also promoting SCFA production and absorption through the upregulation of SCFA synthetic enzymes and the mRNA expression of SLC9A1 gene. Moreover, both SA and sodium propionate infusion resulted in an enhanced total antioxidant capacity, an increased concentration of occludin, and higher abundances of specific rumen bacteria, such as "Candidatus Saccharimonas," Christensenellaceae R-7, Butyrivibrio, Rikenellaceae RC9 gut, and Alloprevotella. In addition, sodium butyrate (SB) infusion exhibited positive effects by increasing the width of rumen papilla and the thickness of the stratum basale. SB infusion further enhanced antioxidant capacity and barrier function facilitated by cross talk with Monoglobus and Incertae Sedis. Furthermore, metabolome and transcriptome data revealed distinct metabolic patterns in rumen contents and epithelium, with a particular impact on amino acid and fatty acid metabolism processes. In conclusion, our data provided novel insights into the regulator effects of extensive infusion of the three major SCFAs on rumen fermentation patterns, antioxidant capacity, rumen barrier function, and rumen papilla development, all achieved without inducing rumen epithelial inflammation. IMPORTANCE The consequences of massive exogenous supplementation of SCFAs on rumen microbial fermentation and rumen epithelium health remain an area that requires further exploration. In our study, we sought to investigate the specific impact of administering high doses of exogenous acetate, propionate, and butyrate on rumen homeostasis, with a particular focus on understanding the interaction between the rumen microbiome and epithelium. Importantly, our findings indicated that the massive infusion of these SCFAs did not induce rumen inflammation. Instead, we observed enhancements in antioxidant capacity, strengthening of rumen barrier function, and promotion of rumen papilla development, which were facilitated through interactions with specific rumen bacteria. By addressing existing knowledge gaps and offering critical insights into the regulation of rumen health through SCFA supplementation, our study holds significant implications for enhancing the well-being and productivity of ruminant animals.

Heating Drinking Water in Cold Season Improves Growth Performance via Enhancing Antioxidant Capacity and Rumen Fermentation Function of Beef Cattle

The research aimed to investigate the suitable drinking water temperature in winter and its effect on the growth performance, antioxidant capacity, and rumen fermentation function of beef cattle. A total of 40 beef cattle (640 ± 19.2 kg) were randomly divided into five treatments with eight cattle in each treatment raised in one pen according to initial body weight. Each treatment differed only in the temperature of drinking water, including the room-temperature water and four different heat water groups named RTW, HW_1, HW_2, HW_3, and HW_4. The measured water temperatures were 4.39 ± 2.546 °C, 10.6 ± 1.29 °C, 18.6 ± 1.52 °C, 26.3 ± 1.70 °C, and 32.5 ± 2.62 °C, respectively. The average daily gain (ADG) showed a significant linear increase during d 0 to 60 and a quadratic increase during d 31 to 60 with rising water temperature (p < 0.05), and the highest ADG of 1.1911 kg/d was calculated at a water temperature of 23.98 °C (R2 = 0.898). The average rectal temperature on d 30 (p = 0.01) and neutral detergent fiber digestibility (p < 0.01) increased linearly with increasing water temperature. Additionally, HW_2 reduced serum triiodothyronine, thyroxine, and malondialdehyde (p < 0.05), and increased serum total antioxidant capacity (p < 0.05) compared with RTW. Compared with HW_2, RTW had unfavorable effects on ruminal propionate, total volatile fatty acids, and cellulase concentrations (p < 0.05), and lower relative mRNA expression levels of claudin-4 (p < 0.01), occludin (p = 0.02), and zonula occludens-1 (p = 0.01) in the ruminal epithelium. Furthermore, RTW had a higher abundance of Prevotella (p = 0.04), Succinivibrionaceae_UCG-002 (p = 0.03), and Lachnospiraceae_UCG-004 (p = 0.03), and a lower abundance of Bifidobacteriaceae (p < 0.01) and Marinilabiliaceae (p = 0.05) in rumen compared to HW_2. Taken together, heated drinking water in cold climates could positively impact the growth performance, nutrient digestibility, antioxidant capacity, and rumen fermentation function of beef cattle. The optimal water temperature for maximizing ADG was calculated to be 23.98 °C under our conditions. Ruminal propionate and its producing bacteria including Prevotella, Succinivibrionaceae, and Lachnospiraceae might be important regulators of rumen fermentation of beef cattle drinking RTW under cold conditions.

Sodium Propionate Relieves LPS-Induced Inflammation by Suppressing the NF-ĸB and MAPK Signaling Pathways in Rumen Epithelial Cells of Holstein Cows

Subacute ruminal acidosis (SARA) is a prevalent disease in intensive dairy farming, and the rumen environment of diseased cows acidifies, leading to the rupture of gram-negative bacteria to release lipopolysaccharide (LPS). LPS can cause rumentitis and other complications, such as liver abscess, mastitis and laminitis. Propionate, commonly used in the dairy industry as a feed additive, has anti-inflammatory effects, but its mechanism is unclear. This study aims to investigate whether sodium propionate (SP) reduces LPS-induced inflammation in rumen epithelial cells (RECs) and the underlying mechanism. RECs were stimulated with different time (0, 1, 3, 6, 9, 18 h) and different concentrations of LPS (0, 1, 5, 10 μg/mL) to establish an inflammation model. Then, RECs were treated with SP (15, 25, 35 mM) or 10 μM PDTC in advance and stimulated by LPS for the assessment. The results showed that LPS (6h and 10 μg/mL) could stimulate the phosphorylation of NF-κB p65, IκB, JNK, ERK and p38 MAPK through TLR4, and increase the release of TNF-α, IL-1β and IL-6. SP (35 mM) can reduce the expression of cytokines by effectively inhibiting the NF-κB and MAPK inflammatory pathways. This study confirmed that SP inhibited LPS-induced inflammatory responses through NF-κB and MAPK in RECs, providing potential therapeutic targets and drugs for the prevention and treatment of SARA.

Dietary disodium fumarate supplementation alleviates subacute ruminal acidosis (SARA)-induced liver damage by inhibiting pyroptosis via mitophagy-NLRP3 inflammasome pathway in lactating Hu sheep

Liver damage is common in ruminants with subacute ruminal acidosis (SARA). Disodium fumarate (DF) could regulate rumen microbial community and neutralize ruminal organic acids. This study aimed to evaluate the effect of dietary DF supplementation on SARA-induced liver damage and investigate the underlying mechanism. The results showed that feeding a high-concentrate diet induced decreased rumen fluid pH and increased ruminal LPS. The rumen fluid pH in the HC group was less than 5.6 at 4 time points, indicating that SARA was successfully induced. The histopathological analysis showed that in the HC group, hemorrhage and inflammatory cell infiltration were observed in liver tissue. Using ELISA kits and biochemical analyzer, we identified that the contents of interleukin 1beta (IL-1β), interleukin 18 (IL-18), caspase-1, and the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in hepatic vein were elevated in the HC group. However, DF supplementation increased rumen fluid pH value, decreased ruminal LPS, attenuated hemorrhage and inflammatory cell infiltration in the liver tissue, and decreased contents of IL-1β, IL-18, caspase-1, AST, and ALT in the hepatic vein. Real-time PCR and western blot analysis displayed that SARA-induced increased expression of pyroptosis-related proteins (GSDMD-NT) was attenuated in the HCDF group. Meanwhile, SARA induced increased expression of mitophagy and inflammasome-related proteins (MAP1LC3-II, PINK1, Parkin, cleaved-caspase-11, cleaved-caspase-1, NLRP3, and ASC) and elevated expression of inflammasome-related genes (NLRP3, CASP1, and ASC), which was reversed by DF supplementation. Moreover, SARA activated toll-like receptor 4 (TLR4)-nuclear factor kappa B (NF-κB) signaling pathway and inhibited the entry of forkhead box A2 (FOXA2) into the nucleus, which was reversed by DF supplementation. Collectively, our data suggest that dietary DF supplementation inhibited hepatocyte pyroptosis by regulating the mitophagy-NLRP3 inflammasome pathway and the NF-κB signaling pathway, thus alleviating SARA-induced liver damage in Hu sheep.

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.

Comparison of the effect of Saccharomyces cerevisiae-Megasphaera elsdenii and buffer on growth performance, digestibility, ruminal histomorphometry, and carcass characteristics of fattening lambs in high concentrate diet

This study aimed to investigate the effect of rumen pH-adjusting additives in the high-concentrated diet on functional traits, nutrient digestion, some meat parameters, and histomorphometry, and rumen histopathology. Twenty-four Arabia male lambs with 3 to 4 months old and initial body weight of 23.9 ± 3.15 kg were used in a completely randomized design with three treatments and eight replicates. The study was 77 days, including 14 days of the adaptation period and 63 days of the record taking and sampling period. The experimental treatments consisted of a control diet, control diet + sodium bicarbonate buffer, control diet + Megasphaera elsdenii, and Saccharomyces cerevisiae (bacterial-yeast). Rumen fluid was taken by stomach tube at 3 h after morning feeding to measure pH. The lambs were weighed every 3 weeks during the period, and the body weight changes, average daily gain, and total weight gain were measured, and the feed conversion ratio was calculated. At the end of the experiment, the lambs were slaughtered, and the longissimus dorsi muscle was prepared to determine the meat parameters. For histological studies, the abdominal rumen sac was sampled. There were no differences among treatments in dry matter intake (DMI), daily weight gain (ADG), and feed conversion ratio (P > 0.05). Propionate concentration was higher in the bacteria-yeast treatment than other treatments (P < 0.05). Protein digestibility was higher in control and bacteria-yeast treatments than buffer treatment (P < 0.05). The percentage of meat protein, carcass weight, and dressing percentage in bacterial-yeast treatment was higher than other treatments (P < 0.05). Rumen wall thickness in the buffer and bacterial-yeast receiving treatments was greater than the control treatment and was significant in the buffer treatment compared to the control treatment (P < 0.05). The thickness of rumen epithelial tissue in the buffer and bacterial-yeast recipient treatments was less than the control treatment (P < 0.05). Rumen papillae thickness was higher in the control treatment than other treatments (P < 0.05). Hydropic degeneration and parakeratosis were less in pH-regulating treatments than in control. The results showed that the use of Megasphaera elsdenii could be an effective way to modulate the ruminal fermentation conditions of lambs fed with high concentrate diets. In addition, to increaseing dressing percentage and meat protein, it can also reduce tissue damage and improve ruminal tissue structure.

Transcriptomic profiles of the ruminal wall in Italian Mediterranean dairy buffaloes fed green forage

BACKGROUND

Green feed diet in ruminants exerts a beneficial effect on rumen metabolism and enhances the content of milk nutraceutical quality. At present, a comprehensive analysis focused on the identification of genes, and therefore, biological processes modulated by the green feed in buffalo rumen has never been reported. We performed RNA-sequencing in the rumen of buffaloes fed a total mixed ration (TMR) + the inclusion of 30% of ryegrass green feed (treated) or TMR (control), and identified differentially expressed genes (DEGs) using EdgeR and NOISeq tools.

RESULTS

We found 155 DEGs using EdgeR (p-values < 0.05) and 61 DEGs using NOISeq (prob ≥0.8), 30 of which are shared. The rt-qPCR validation suggested a higher reliability of EdgeR results as compared with NOISeq data, in our biological context. Gene Ontology analysis of DEGs identified using EdgeR revealed that green feed modulates biological processes relevant for the rumen physiology and, then, health and well-being of buffaloes, such as lipid metabolism, response to the oxidative stress, immune response, and muscle structure and function. Accordingly, we found: (i) up-regulation of HSD17B13, LOC102410803 (or PSAT1) and HYKK, and down-regulation of CDO1, SELENBP1 and PEMT, encoding factors involved in energy, lipid and amino acid metabolism; (ii) enhanced expression of SIM2 and TRIM14, whose products are implicated in the immune response and defense against infections, and reduced expression of LOC112585166 (or SAAL1), ROR2, SMOC2, and S100A11, encoding pro-inflammatory factors; (iii) up-regulation of NUDT18, DNAJA4 and HSF4, whose products counteract stressful conditions, and down-regulation of LOC102396388 (or UGT1A9) and LOC102413340 (or MRP4/ABCC4), encoding detoxifying factors; (iv) increased expression of KCNK10, CACNG4, and ATP2B4, encoding proteins modulating Ca²⁺ homeostasis, and reduced expression of the cytoskeleton-related MYH11 and DES.

CONCLUSION

Although statistically unpowered, this study suggests that green feed modulates the expression of genes involved in biological processes relevant for rumen functionality and physiology, and thus, for welfare and quality production in Italian Mediterranean dairy buffaloes. These findings, that need to be further confirmed through the validation of additional DEGs, allow to speculate a role of green feed in the production of nutraceutical molecules, whose levels might be enhanced also in milk.

Invited review: Rumen modifiers in today's dairy rations

Our aim was to review feed additives that have a potential ruminal mechanism of action when fed to dairy cattle. We discuss how additives can influence ruminal fermentation stoichiometry through electron transfer mechanisms, particularly the production and usage of dihydrogen. Lactate accumulation should be avoided, especially when acidogenic conditions suppress ruminal neutral detergent fiber digestibility or lead to subclinical acidosis. Yeast products and other probiotics are purported to influence lactate uptake, but growing evidence also supports that yeast products influence expression of gut epithelial genes promoting barrier function and resulting inflammatory responses by the host to various stresses. We also have summarized methane-suppressing additives for potential usage in dairy rations. We focused on those with potential to decrease methane production without decreasing fiber digestibility or milk production. We identified some mitigating factors that need to be addressed more fully in future research. Growth factors such as branched-chain volatile fatty acids also are part of crucial cross-feeding among groups of microbes, particularly to optimize fiber digestibility in the rumen. Our developments of mechanisms of action for various rumen-active modifiers should help nutrition advisors anticipate when a benefit in field conditions is more likely.

High concentrate diet induced inflammatory response and tight junction disruption in the mammary gland of dairy cows

This study aimed to investigate the effect and mechanism of a high concentrate (HC) diet on the inflammatory response and cellular tight junctions (TJs) in the mammary gland of dairy cows. Twelve lactating Holstein dairy cows were randomly assigned into low concentrate (LC) and HC groups (n = 6), which were fed with LC diet and HC diet respectively for 3 weeks. The HC diet lead to subacute ruminant acidosis with a rumen pH < 5.6 more than 3 h daily. The HC diet triggered an inflammatory response with increased levels of inflammatory cytokines in the lacteal vein, upregulated expression of inflammation-related genes, elevated activity of myeloperoxidase, and inflammatory cells infiltration in the mammary gland. Furthermore, the HC diet induced the activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways with enhanced phosphorylation ratios of NF-κB P65, inhibitor of NF-κB (IκB), P38 and extracellular signal-regulated kinase 1/2 (ERK1/2) as well as decreased ratios of DNA methylation and chromatin compaction of genes coding for proinflammatory cytokines, which contributed to the upregulation of proinflammatory cytokine expression. The HC diet also destroyed the integrity of TJ with discontinuous and decreased expression levels of zonula occludens-1, Occludin, Claudin-4 and increased expression level of Claudin-1 in the mammary epithelial cells compared with LC group. Conclusively, the HC diet induced the activation of NF-κB and MAPK signaling pathways and epigenetic modifications, promoted the transcription of proinflammatory cytokines, and finally caused inflammatory response and TJ disruption in the mammary gland of dairy cows.

Subacute ruminal acidosis downregulates FOXA2, changes oxidative status, and induces autophagy in the livers of dairy cows fed a high-concentrate diet

The purpose of this experiment was to investigate high-concentrate feeding-induced changed status of oxidative and autophagy in the livers of dairy cows. Hepatocyte nuclear factor 3β (FOXA2) was reported in cases of liver fibrosis, glucolipid metabolism, and hepatocyte differentiation, but not in cases liver damage in cows fed a high-concentrate diet. Therefore, we also aimed to explore the potential role of FOXA2 in SARA-induced liver damage. We divided 12 mid-lactating Holstein cows into 2 groups and fed them a high-concentrate (HC group, forage:concentrate = 4:6) and a low-concentrate (forage:concentrate = 6:4) diet. After a 2-wk adaptation period and a 3-wk experimental period, peripheral blood was collected for determination of antioxidant enzyme activity, and liver tissue was collected to examine genes and proteins. On d 20 and 21 of the experiment, rumen fluid was collected, and the pH was measured. A significant difference in rumen fluid pH was found between the 2 groups (low-concentrate: 6.10 ± 0.07 vs. HC: 5.59 ± 0.09). The rumen fluid pH in the HC group was less than 5.6 at 2 time points, indicating that SARA was successfully induced. Lipopolysaccharide (0.24 ± 0.10 vs. 0.42 ± 0.12) and malondialdehyde (1.46 ± 0.25 vs. 2.94 ± 0.65) increased, whereas superoxide dismutase (14.06 ± 0.63 vs. 11.71 ± 0.64), reduced glutathione (14.48 ± 2.25 vs. 6.82 ± 0.67), and the total antioxidant capacity (0.43 ± 0.03 vs. 0.30 ± 0.03) decreased in the peripheral blood of the HC group. Moreover, in liver tissue from the HC group, catalase (0.71 ± 0.03 vs. 0.49 ± 0.03) and superoxide dismutase (27.46 ± 1.90 vs. 20.32 ± 1.54) were decreased, whereas malondialdehyde (0.21 ± 0.03 vs. 0.28 ± 0.03) was elevated. Meanwhile, we observed lower gene expression of CAT (1.00 ± 0.15 vs. 0.64 ± 0.17), NAD(P)H quinone dehydrogenase 1 (NQO1; 1.00 ± 0.09 vs. 0.47 ± 0.14), glutathione peroxidase 1 (GPX1; 1.03 ± 0.27 vs. 0.55 ± 0.09), SOD1 (1.01 ± 0.17 vs. 0.76 ± 0.17), and SOD3 (1.02 ± 0.21 vs. 0.55 ± 0.16) in the liver tissue of the HC group. Furthermore, western blot analysis showed that high-concentrate feeding led to decreased sirtuin-1 (SIRT1) (1.00 ± 0.10 vs. 0.62 ± 0.15) and FOXA2 (1.02 ± 0.19 vs. 0.68 ± 0.18), elevated autophagy-related protein microtubule associated protein 1 light chain 3 II (MAP1LC3-II; 1.00 ± 0.32 vs. 1.98 ± 0.83) and autophagy related 5 (ATG5; 1.00 ± 0.30 vs. 1.80 ± 0.27), and suppressed antioxidant signaling pathway-related protein nuclear factor erythroid 2-like 2 (NFE2L2; 1.00 ± 0.18 vs. 0.61 ± 0.30) and heme oxygenase 1 (HMOX1; 1.00 ± 0.48 vs. 0.38 ± 0.25) in liver tissue. Overall, these data indicated that SARA elevated systematic oxidative status and enhanced autophagy in the liver, and suppressed SIRT1 and FOXA2 may mediate enhanced oxidative damage and autophagy in the livers of dairy cows fed a high-concentrate diet.

GPR41 Regulates the Proliferation of BRECs via the PIK3-AKT-mTOR Pathway

Short-chain fatty acids (SCFAs) play a pivotal role in regulating the proliferation and development of bovine rumen epithelial cells (BRECs). G protein-coupled receptor 41 (GPR41) is involved in the signal transduction in BRECs as a receptor for SCFAs. Nevertheless, the impact of GPR41 on the proliferation of BRECs has not been reported. The results of this research showed that the knockdown of GPR41 (GRP41KD) decreased BRECs proliferation compared with the wild-type BRECs (WT) (p < 0.001). The RNA sequencing (RNA-seq) analysis showed that the gene expression profiles differed between WT and GPR41KD BRECs, with the major differential genes enriched in phosphatidylinositol 3-kinase (PIK3) signaling, cell cycle, and amino acid transport pathways (p < 0.05). The transcriptome data were further validated by Western blot and qRT-PCR. It was evident that the GPR41KD BRECs downregulated the level of the PIK3-Protein kinase B (AKT)-mammalian target of the rapamycin (mTOR) signaling pathway core genes, such as PIK3, AKT, eukaryotic translation initiation factor 4E binding protein 1 (4EBP1) and mTOR contrasted with the WT cells (p < 0.01). Furthermore, the GPR41KD BRECs downregulated the level of Cyclin D2 p < 0.001) and Cyclin E2 (p < 0.05) compared with the WT cells. Therefore, it was proposed that GPR41 may affect the proliferation of BRECs by mediating the PIK3-AKT-mTOR signaling pathway.