Lactate uptake in the rumen and its contributions to subacute rumen acidosis of goats induced by high-grain diets

Associations of Ruminal Microbiota with Susceptibility to subacute Ruminal Acidosis in Dairy Goats

Long-term feeding of high-concentrate diets (HCD) to ruminants often leads to subacute ruminal acidosis (SARA). The fact that some ruminants adapt to HCD without developing SARA suggests that the ruminal microbiota communities may play a role in the susceptibility to this disorder. To address this hypothesis, 20 dairy goats were fed an HCD consisting of 30% forage and 70% concentrate for 10 weeks. The dairy goats were divided into a SARA susceptible group (SS, pH < 5.8 for more than 3 hours within 12 hours) and a SARA tolerant group (ST, pH < 5.8 for not more than 3 hours within 12 hours) according to ruminal fluid pH. At 0 and 10 weeks after feeding with HCD, blood samples were collected via the jugular vein using a vacutainer to assess the levels of white blood cells, neutrophils, and lymphocytes. Meanwhile, milk samples were collected to measure milk composition. In addition, ruminal fluid was collected via a gastric tube at 0 and 10 weeks of feeding the experimental diets via gastric tube and the ruminal microbiota of SS and ST dairy goats were analyzed. The results indicated that feeding with HCD led to greater levels of white blood cells, neutrophils, creatinine, and urea nitrogen, and lower concentrations of milk fat. Further, levels of white blood cells and neutrophils were greater in SS compared with ST goats. The 16S rRNA sequencing analysis revealed that the diversity and abundance of the ruminal bacterial community was lower in SS compared to ST goats. Furthermore, the relative abundance of norank_f_F082, norank_f_Bifidobacteriaceae, and the genus Ruminococcus was higher in the SS group. These microorganisms are important for the digestion of non-structural carbohydrates and the production of volatile fatty acids (VFA). The initial ruminal microbiota composition analysis revealed that Rikenellaceae_RC9_gut_group was greater in ST goats, both before and after feeding HCD. By promoting carbohydrate metabolism in the rumen, the data suggest that the increased abundance of norank_f_F082, Ruminococcus and UCG-004 may lead to the production of metabolites that increase susceptibility to SARA when fed HCD. Enrichment of ruminal bacteria such as Rikenellaceae_RC9_gut_group may reduce susceptibility to SARA in HCD diets. Overall, manipulation of the ruminal microbiota may be a novel approach to prevent the development of SARA in ruminants.

In vitro evaluation of slow-release urea compounds

The objective of this study was to evaluate the effects of different slow-release urea (SRU) compounds on ruminal fermentation, nutrient degradation, and nitrogen (N) utilization in a dual-flow continuous-culture system (experiment 1), as well as ammonia-N (NH3-N) release rate in a batch culture system (experiment 2). In experiment 1, 8 fermenters were used in a replicated 4 × 4 Latin square design with 4 treatments and 4 experimental periods. The treatments were formulated to contain the same amount of N, differing in the source of nonprotein N, such as control (CON), with noncoated urea at 0.62% DM; partial inclusion of SRU compound 1 (SRU1) at 0.51% DM; partial inclusion of SRU compound 2 (SRU2) at 0.51% DM; and partial inclusion of SRU compound 3 (SRU3) at 0.51% DM. Each period lasted 10 d. The last 3 d of each period were used for sample collection. Samples were collected for pH, lactate, VFA, NH3-N kinetics, nutrient degradability, and N metabolism. In experiment 2, a batch culture incubation was conducted as a complete randomized block design, using 3 Erlenmeyer flasks per treatment in 3 runs. Each treatment contained 1 of the 4 NPN sources used in experiment 1, (CON, SRU1, SRU2, SRU3) or without any NPN (blank, BK), and samples were collected at different time points for NH3 analysis. All flasks, except for BK, contained equal amounts of 21.56 mg N, and all flasks were inoculated with 260 mL of a 1:2 mixture of ruminal fluid and nutritive solution. Data of both experiments 1 and 2 were analyzed using the MIXED procedure of SAS. In experiment 1, there were no effects of treatment on pH or NH3-N kinetics. There were no effects of treatments on lactate kinetics; however, there was an interaction between treatment and time. For 24-h VFA pool, there were treatment effects on acetate, propionate, acetate:propionate ratio (A:P), and branched-chain (BC)VFA proportion. Compared with CON, SRU1 had lower A:P ratio and acetate proportion, with greater proportion of propionate, which could represent a favorable fermentation partner compared with CON. Treatment SRU1 had lower BCVFA proportion than the other treatments, which indicates less protein degradation. There were no treatment effects for nutrient degradability and N flow. Based on observations in experiment 1, SRU1 could have the potential of improving ruminal fermentation and N utilization. Moreover, the different SRU compounds had different fermentation patterns according to their VFA profiles. In experiment 2, there were significant effects for treatment and time, and a tendency for treatment by time interaction effect. The N release rate of SRU1 was similar to CON and faster than SRU2 and 3, and the differences in N release rates could be detected as early as at 0.75 h of incubation. Thus, SRU1 may not be as slow degrading when compared with SRU2 and 3. In conclusion, no effects were found on nutrient degradability and N utilization. However, the different SRU compounds had different N release rates, which could affect ruminal fermentation pattern in different diets.

Carbonate Buffer Mixture Alleviates Subacute Rumen Acidosis Induced by Long-Term High-Concentrate Feeding in Dairy Goats by Regulating Rumen Microbiota

This study aimed to elucidate the therapeutic mechanisms of carbonate buffer mixture (CBM) in mitigating subacute rumen acidosis (SARA) by examining its effects on rumen pH, systemic inflammation, and rumen microbiota in a dairy goat model. Using a controlled experimental design, SARA was induced through 8-week high-concentrate diet feeding (70% concentrate, 30% forage), followed by 2-day CBM treatment. Comprehensive analyses included rumen pH monitoring, serum inflammatory marker quantification (IL-1β, TNF-α) by ELISA, rumen barrier integrity assessment through tight junction proteins (TJs) ZO-1, Occludin, and Claudin-3 by western blot analysis, and 16S rRNA sequencing of rumen microbiota. The results demonstrated that CBM administration rapidly elevated depressed rumen pH within 6 h post-treatment while concurrently reducing circulating LPS levels. The analysis of rumen 16S rRNA showed that CBM significantly increased the rumen microbial diversity and abundance of SARA dairy goats. Butyric acid generation groups such as Rikenellaceae_RC9_gut_group, NK4A214_group, and Prevotellaceae UCG-001 were selectively enriched, and corresponding functional predictions showed that the butyric acid synthesis pathway (PICRUSt2) was enhanced. These findings suggest that CBM has a multidimensional therapeutic effect by simultaneously correcting rumen acidosis, alleviating systemic inflammation, and restoring microbial balance through pH-dependent and pH-independent mechanisms, providing a scientifically validated nutritional strategy for SARA management in intensive ruminant production systems.

Integrating Subacute Ruminal Acidosis, Lipopolysaccharide, and Trained Immunity: A Comprehensive Review

Subacute ruminal acidosis (SARA) has emerged as a prevalent digestive disorder that significantly affects the overall health of ruminants, with notable links to various inflammatory diseases. Throughout the progression of SARA, elevated lipopolysaccharide (LPS) levels in the rumen play a crucial role in initiating the innate immune response. In this review, we evaluate the recent insights into the pathways associated with SARA-induced inflammatory responses, with a specific focus on LPS. It is important to recognize the variation in the immune response activation potential of LPS derived from different bacterial sources. This variability aligns with the widespread detection of LPS in the rumens of ruminants with SARA. Nonetheless, trained immunity is expected to become a novel strategy for the prevention and control of SARA. This mechanism offers a rapid response to secondary stimuli, including LPS, effectively preventing inflammation. Ultimately, this review establishes a comprehensive system integrating SARA, LPS, and trained immunity. Through this integrated approach, we aim to provide innovative solutions to the challenges associated with SARA.

Polymeric rumen-stable delivery systems for delivering nutricines

Ruminants face unique drug and nutrient delivery challenges because of their symbiotic rumen microorganisms. Polymeric rumen-stable delivery systems (RDSs) have emerged as a promising solution for efficiently delivering nutrition and enhancing animal health and productivity. Traditional methods such as heat and chemical treatment have been improved with polymeric coatings that facilitate the slow postruminal release of bioactive substances. Polymeric coatings of nutrients offer significant potential for improving ruminant health, reducing farmer costs, and promoting sustainability in livestock. This paper explores the mechanisms of rumen protection and abomasal release provided by polymeric coatings, discusses other RSDs, and reviews methods for evaluating their performance in vitro and in vivo. Further research in this area could advance novel nutricine delivery solutions for ruminants.

Performance improvements and increased ruminal microbial interactions in Angus heifers via supplementation with native rumen bacteria during high-grain challenge

Feedlot cattle may be subjected to digestive disorders, including ruminal acidosis, due to high concentration of grain in their diet. Therefore, novel feeding strategies are required to maximize animal performance and mitigate economic losses in the operation. This study employed a two-period crossover design to assess the effect of direct ruminal administration of native rumen microorganisms (NRM) inoculation on cattle that underwent a high-grain challenge. The NRM inoculation consisted of six microorganisms (1.70 M CFU /day/animal) isolated from the rumen of healthy feedlot cattle: Succinivibrio dextrinosolvens ASCUSBF53, Prevotella albensis ASCUSBF41, Chordicoccus furentiruminis ASCUSBF65, Bacteroides xylanisolvens ASCUSBF52, Clostridium beijerinckii ASCUSBF26, and Syntrophococcus sp. ASCUSBF60. The trial consisted of 16 Angus heifers receiving NRM (n = 8) or a CON (CON = Carrier Buffer; n = 8) inoculation daily for 14-days as pre-challenge while on a high-grain diet and continued daily for a 21-day treatment period. The combined 35 days of microbial supplementation resulted in an improved average daily gain (ADG) of 29% (P = 0.037) and a tendency toward a 19% decrease in the feed efficiency metric, gain to feed ratio (G: F) (P = 0.055). Additionally, administration of NRM to animals on a high-grain diet, improved ruminal microbiome stability (P < 0.001), potentially encouraging the conversion of rumen lactate to propionate over time via the succinate pathway and alleviating metabolic stress.

Can the supplementation of autolyzed yeast (Saccharomyces cerevisiae) affect the diet digestibility, feeding behavior, levels of blood metabolites, and performance of Dorper × Santa Ines lambs finished in feedlot?

This study aimed to evaluate the effect of autolyzed yeast (obtained from culture of Saccharomyces cerevisiae in sugarcane derivatives) supplementation on diet digestibility, feeding behavior, levels of blood metabolites associated with protein and energy metabolism, and performance of Dorper × Santa Ines lambs finished in feedlot. Twenty-four non-castrated male lambs with an average age of 4 months and a body weight (BW) of 19.49 ± 3.08 kg were allocated to individual pens within a covered and elevated shed. The pens had a slatted floor without bedding suspended 1.8 m above the ground, and an area of 1.5 m2. The trial was set out in a completely randomized design with two treatments and twelve replicates each. The treatments consisted of a basal diet without yeast products (Control) or with yeast culture (Yeast, RumenYeast® at 5 g/animal/day). Lambs were fed ad libitum with a total mixed ration (TMR) composed of 400 g/kg of dry matter (DM) of Tifton 85 hay (Cynodon spp.) and 600 g/kg DM of concentrate feed, and contained 146 g/kg DM of crude protein and 2.30 Mcal/kg DM of metabolizable energy. The experiment was conducted over 84 days, with the first 14 days serving as an adaptation period. The subsequent experimental period was divided into two phases to evaluate animal performance (Days 1-63) and DM digestibility (Days 64-70). The supplementation with autolyzed yeast did not affect rumen or fecal pH, the DM digestibility, as well as the feeding behavior of lambs (the time spent on feeding, rumination, water intake, and idleness activities). In addition, yeast supplementation did not alter the serum levels of albumin, creatinine, urea, or level of plasma glucose, resulting in similar animal performance compared to the Control group. The mean values for final BW, DM intake, average daily gain, and feed conversion ratio were 37.52 kg, 1.051 kg/day, 0.286 kg/day, and 3.74 kg DM/kg gain, respectively. In the conditions of this study, the supplementation of autolyzed yeast in TMR (5 g/animal/day) does not affect diet digestibility, feeding behavior, blood metabolites, or performance of lambs finished in feedlot. Regarding that metabolic and performance lamb responses were not improved, the supplementation of autolyzed yeast at the tested dose is not recommended. However, it is important to note that markers related to immunity and inflammation were not evaluated in our work, and these should be considered in future studies.

The ruminant gut microbiome vs enteric methane emission: The essential microbes may help to mitigate the global methane crisis

Ruminants release enteric methane into the atmosphere, significantly increasing greenhouse gas emissions and degrading the environment. A common focus of traditional mitigation efforts is on dietary management and manipulation, which may have limits in sustainability and efficacy, exploring the potential of essential microorganisms as a novel way to reduce intestinal methane emissions in ruminants; a topic that has garnered increased attention in recent years. Fermentation and feed digestion are significantly aided by essential microbes found in the rumen, such as bacteria, fungi, and archaea. The practical implications of the findings reported in various studies conducted on rumen gut concerning methane emissions may pave the way to understanding the mechanisms of CH4 production in the rumen to enhance cattle feed efficiency and mitigate CH4 emissions from livestock. This review discussed using essential bacteria to reduce intestinal methane emissions in ruminants. It investigates how particular microbial strains or consortia can alter rumen fermentation pathways to lower methane output while preserving the health and productivity of animals. We also describe the role of probiotics and prebiotics in managing methane emissions using microbial feed additives. Further, recent studies involving microbial interventions have been discussed. The use of new methods involving functional metagenomics and meta-transcriptomics for exploring the rumen microbiome structure has been highlighted. This review also emphasizes the challenges faced in altering the gut microbiome and future directions in this area.

Disorders of acid-base balance promote rumen lipopolysaccharide biosynthesis in dairy cows by modulating the microbiome

Introduction

Disorders of acid-base balance in the rumen of dairy cows have a significant impact on their health and performance. However, the effect of transient differences in pH on susceptibility to subacute ruminal acidosis (SARA) and lipopolysaccharide (LPS) biosynthesis in dairy cows remains unclear.

Methods

In this study, milk, serum, and rumen fluid samples from 40 Holstein dairy cows (on d 56 postpartum) with different rumen pH (2-4 h after morning feeding) were explored to investigate the difference of susceptibility to SARA and the correlation between microbiome, LPS and inflammation. These cows were categorized into low pH (LPH, pH ≤ 6.0, n = 20) and high pH (HPH, pH ≥ 6.5, n = 20) groups.

Results

The results showed that LPH group increased the concentrations of total volatile fatty acids, acetate, propionate, butyrate and valerate. However, milk yield and milk compositions were unaffected. Compared to the HPH group, the LPH group increased the concentrations of serum BHBA, NEFA, LPS, HIS, IL-2, IL-6, TNF-α, and MDA, and decreased the concentrations of serum IgA, IgM, IgG, SOD, T-AOC, and mTOR. In addition, the LPH group decreased the copies of Ruminococcus flavefaciens and increased the copies of Fibrobacter succinogenes. Microbial community analysis isupplendicated a significant difference in bacterial composition between the two groups. At the phylum level, Bacteroidota and Firmicutes were enriched in the LPH and HPH groups, respectively. At the genus level, the dominant bacteria in the LPH group were Prevotella. Additionally, the LPH group increased the proportions of Gram-negative phenotypes, potentially pathogenic phenotypes and LPS biosynthesis. The close correlation between two key enzymes for LPS synthesis LpxL and LpxM with rumen pH, inflammatory markers, and microorganisms indicates that low pH may increase the risk of inflammation by facilitating the lysis of Gram-negative bacteria and the release of penta-acylated LPS. Penta-acylated and hexa-acylated LPS may be mainly derived from Prevotella and Succinivibrionaceae_UCG-001, respectively.

Discussion

Overall, these results support the notion that transient low pH could reflect the risk of cows suffering from SARA and associated inflammation and is strongly associated with penta-acylated LPS. Our findings provide new insights into ruminant health improvement and disease prevention strategies.

Effects of Dietary Energy Levels on Growth Performance, Nutrient Digestibility, Rumen Barrier and Microflora in Sheep

Dietary energy is crucial for ruminants' performance and health. To determine optimal dietary energy levels for growing sheep, we evaluated their growth performance, nutrient digestibility, rumen fermentation, barrier function, and microbiota under varying metabolic energy (ME) diets. Forty-five growing Yunnan semi-fine wool sheep, aged 10 months and weighing 30.8 ± 1.9 kg, were randomly allocated to five treatments, each receiving diets with ME levels of 8.0, 8.6, 9.2, 9.8 or 10.4 MJ/kg. The results showed that with increasing dietary energy, the average daily gain (ADG) as well as the digestibility of dry matter (DM) and organic matter (OM) increased (p < 0.05), while the feed conversion ratio (FCR) decreased linearly (p = 0.01). The concentration of total VFA (p = 0.03) and propionate (p = 0.01) in the rumen increased linearly, while rumen pH (p < 0.01) and the acetate-propionate ratio (p = 0.01) decreased linearly. Meanwhile, the protein contents of Claudin-4, Claudin-7, Occludin and ZO-1 as well as the relative mRNA expression of Claudin-4 and Occludin also increased (p < 0.05). In addition, rumen bacterial diversity decreased with the increase of dietary energy, and the relative abundance of some bacteria (like Saccharofermentans, Prevotella and Succiniclasticum) changed. In conclusion, increasing dietary energy levels enhanced growth performance, nutrient digestibility, rumen fermentation, and barrier function, and altered the rumen bacterial community distribution. The optimal dietary ME for these parameters in sheep at this growth stage was between 9.8 and 10.4 MJ/kg.

Organic Trace Elements Improve the Eggshell Quality via Eggshell Formation Regulation during the Late Phase of the Laying Cycle

The quality of eggshells is critical to the egg production industry. The addition of trace elements has been shown to be involved in eggshell formation. Organic trace elements have been found to have higher biological availability than inorganic trace elements. However, the effects of organic trace elements additive doses on eggshell quality during the laying period of commercial laying hens required further investigation. This experiment aims to explore the potential mechanisms of different doses of organic trace elements replacing inorganic elements to remodel the eggshell quality of egg-laying hens during the laying period. A total of 360 healthy hens (Lohmann Pink, 45-week-old) were randomly divided into four treatments, with six replications per treatment and 15 birds per replication. The dietary treatments included a basal diet supplemented with inorganic iron, copper, zinc and manganese at commercial levels (CON), a basal diet supplemented with organic iron, copper, zinc and manganese at 20% commercial levels (LOT), a basal diet supplemented with organic iron, copper, zinc and manganese at 30% commercial levels (MOT), and a basal diet supplemented with organic iron, copper, zinc and manganese at 40% commercial levels (HOT). The trial lasted for 8 weeks. The results of the experiment showed that the replacement of organic trace elements did not significantly affect the production performance of laying hens (p > 0.05). Compared with inorganic trace elements, the MOT and HOT groups improved the structure of the eggshells, enhanced the hardness and thickness of the eggshells, increased the Haugh unit of the eggs, reduced the proportion of the mammillary layer in the eggshell, and increased the proportion of the palisade layer (p < 0.05). In addition, the MOT and HOT groups also increased the enzyme activity related to carbonate transport in the blood, the expression of uterine shell gland-related genes (CA2, OC116, and OCX32), and the calcium and phosphorus content in the eggshells (p < 0.05). We also found that the MOT group effectively reduced element discharge in the feces and enhanced the transportation of iron (p < 0.05). In conclusion, dietary supplementation with 30-40% organic micronutrients were able to improve eggshell quality in aged laying hens by modulating the activity of serum carbonate transport-related enzymes and the expression of eggshell deposition-related genes.

Megasphaera elsdenii: Its Role in Ruminant Nutrition and Its Potential Industrial Application for Organic Acid Biosynthesis

The Gram-negative, strictly anaerobic bacterium Megasphaera elsdenii was first isolated from the rumen in 1953 and is common in the mammalian gastrointestinal tract. Its ability to use either lactate or glucose as its major energy sources for growth has been well documented, although it can also ferment amino acids into ammonia and branched-chain fatty acids, which are growth factors for other bacteria. The ruminal abundance of M. elsdenii usually increases in animals fed grain-based diets due to its ability to use lactate (the product of rapid ruminal sugar fermentation), especially at a low ruminal pH (<5.5). M. elsdenii has been proposed as a potential dietary probiotic to prevent ruminal acidosis in feedlot cattle and high-producing dairy cows. However, this bacterium has also been associated with milk fat depression (MFD) in dairy cows, although proving a causative role has remained elusive. This review summarizes the unique physiology of this intriguing bacterium and its functional role in the ruminal community as well as its role in the health and productivity of the host animal. In addition to its effects in the rumen, the ability of M. elsdenii to produce C2-C7 carboxylic acids-potential precursors for industrial fuel and chemical production-is examined.

Integrating Omics Technologies for a Comprehensive Understanding of the Microbiome and Its Impact on Cattle Production

Ruminant production holds a pivotal position within the global animal production and agricultural sectors. As population growth escalates, posing environmental challenges, a heightened emphasis is directed toward refining ruminant production systems. Recent investigations underscore the connection between the composition and functionality of the rumen microbiome and economically advantageous traits in cattle. Consequently, the development of innovative strategies to enhance cattle feed efficiency, while curbing environmental and financial burdens, becomes imperative. The advent of omics technologies has yielded fresh insights into metabolic health fluctuations in dairy cattle, consequently enhancing nutritional management practices. The pivotal role of the rumen microbiome in augmenting feeding efficiency by transforming low-quality feedstuffs into energy substrates for the host is underscored. This microbial community assumes focal importance within gut microbiome studies, contributing indispensably to plant fiber digestion, as well as influencing production and health variability in ruminants. Instances of compromised animal welfare can substantially modulate the microbiological composition of the rumen, thereby influencing production rates. A comprehensive global approach that targets both cattle and their rumen microbiota is paramount for enhancing feed efficiency and optimizing rumen fermentation processes. This review article underscores the factors that contribute to the establishment or restoration of the rumen microbiome post perturbations and the intricacies of host-microbiome interactions. We accentuate the elements responsible for responsible host-microbiome interactions and practical applications in the domains of animal health and production. Moreover, meticulous scrutiny of the microbiome and its consequential effects on cattle production systems greatly contributes to forging more sustainable and resilient food production systems, thereby mitigating the adverse environmental impact.