Epimural Indicator Phylotypes of Transiently-Induced Subacute Ruminal Acidosis in Dairy Cattle

Postbiotics from Saccharomyces cerevisiae fermentation stabilize microbiota in rumen liquid digesta during grain-based subacute ruminal acidosis (SARA) in lactating dairy cows

BACKGROUND

Subacute ruminal acidosis (SARA) is a common metabolic disorder of high yielding dairy cows, and it is associated with dysbiosis of the rumen and gut microbiome and host inflammation. This study evaluated the impact of two postbiotics from Saccharomyces cerevisiae fermentation products (SCFP) on rumen liquid associated microbiota of lactating dairy cows subjected to repeated grain-based SARA challenges. A total of 32 rumen cannulated cows were randomly assigned to 4 treatments from 4 weeks before until 12 weeks after parturition. Treatment groups included a Control diet or diets supplemented with postbiotics (SCFPa, 14 g/d Original XPC; SCFPb-1X, 19 g/d NutriTek; SCFPb-2X, 38 g/d NutriTek, Diamond V, Cedar Rapids, IA, USA). Grain-based SARA challenges were conducted during week 5 (SARA1) and week 8 (SARA2) after parturition by replacing 20% DM of the base total mixed ration (TMR) with pellets containing 50% ground barley and 50% ground wheat. Total DNA from rumen liquid samples was subjected to V3-V4 16S rRNA gene amplicon sequencing. Characteristics of rumen microbiota were compared among treatments and SARA stages.

RESULTS

Both SARA challenges reduced the diversity and richness of rumen liquid microbiota, altered the overall composition (β-diversity), and its predicted functionality including carbohydrates and amino acids metabolic pathways. The SARA challenges also reduced the number of significant associations among different taxa, number of hub taxa and their composition in the microbial co-occurrence networks. Supplementation with SCFP postbiotics, in particular SCFPb-2X, enhanced the robustness of the rumen microbiota. The SCFP supplemented cows had less fluctuation in relative abundances of community members when exposed to SARA challenges. The SCFP supplementation promoted the populations of lactate utilizing and fibrolytic bacteria, including members of Ruminococcaceae and Lachnospiraceae, and also increased the numbers of hub taxa during non-SARA and SARA stages. Supplementation with SCFPb-2X prevented the fluctuations in the abundances of hub taxa that were positively correlated with the acetate concentration, and α- and β-diversity metrics in rumen liquid digesta.

CONCLUSIONS

Induction of SARA challenges reduced microbiota richness and diversity and caused fluctuations in major bacterial phyla in rumen liquid microbiota in lactating dairy cows. Supplementation of SCFP postbiotics could attenuate adverse effects of SARA on rumen liquid microbiota.

Effects of dietary supplementation with alkaline mineral complex on in vitro ruminal fermentation and bacterial composition

Introduction

Dairy industry growth faces challenges in China due to inadequate forage, leading to high-concentrate diets and potential rumen issues. Buffering agents, like sodium bicarbonate, play a crucial role in stabilizing rumen pH. Alkaline Mineral Complex (AMC), a liquid additive with a pH of 14, shows promise in supporting dairy cow health and mitigating heat stress through ionization.

Methods

This experiment was aimed to study the effect of adding AMC to total mixed ration (TMR) on in vitro ruminal fermentation and bacterial composition. AMCat 1, 2, 4, and 8 mL/kg was added to the substrate (0.5 g TMR). Nutrient digestibility was measured after 48 h fermentation, and fermentation parameters and microbial composition were measured after 48 h fermentation.

Results and discussion

The results of the experiment indicated that: The different concentrations of AMC showed a significant impact on time taken for gas production to reach 1/2 of the total gas production (HT) parameters (p < 0.05). Linear pH increase occurs at 6 and 24 h with rising AMC concentration (p < 0.05), showing a quadratic trend at 12 h (p < 0.05). The optimal buffering effect on rumen acid-base balance was observed at a 2 mL/kg concentration of AMC. Microbial diversity analysis indicated that there was no significant change in α-diversity with different AMC concentrations (p > 0.05). The microbial level demonstrated no significant difference in species diversity of rumen fluid bacteria among the various AMC concentration treatment groups compared to the control group, further supporting that the advantage of adding AMC in stabilizing the rumen environment without altering the structure of the rumen microbiota. Besides, the addition of AMC significantly increased the concentrations of acetate, propionate, total fatty acids (TVFA), and NH3-N, suggesting that AMC contributed to enhancing the energy and nitrogen utilization efficiency in ruminants. Based on the above detection indicators, we recommend that the most favorable concentration is 2 mL/kg.

Integrated microbiota-host-metabolome approaches reveal adaptive ruminal changes to prolonged high-grain feeding and phytogenic supplementation in cattle

Diets rich in readily fermentable carbohydrates primarily impact microbial composition and activity, but can also impair the ruminal epithelium barrier function. By combining microbiota, metabolome, and gene expression analysis, we evaluated the impact of feeding a 65% concentrate diet for 4 weeks, with or without a phytogenic feed additive (PFA), on the rumen ecosystem of cattle. The breaking point for rumen health seemed to be the second week of high grain (HG) diet, with a dysbiosis characterized by reduced alpha diversity. While we did not find changes in histological evaluations, genes related with epithelial proliferation (IGF-1, IGF-1R, EGFR, and TBP) and ZO-1 were affected by the HG feeding. Integrative analyses allowed us to define the main drivers of difference for the rumen ecosystem in response to a HG diet, identified as ZO-1, MyD88, and genus Prevotella 1. PFA supplementation reduced the concentration of potentially harmful compounds in the rumen (e.g. dopamine and 5-aminovaleric acid) and increased the tolerance of the epithelium toward the microbiota by altering the expression of TLR-2, IL-6, and IL-10. The particle-associated rumen liquid microbiota showed a quicker adaptation potential to prolonged HG feeding compared to the other microenvironments investigated, especially by the end of the experiment.

Progressive microbial adaptation of the bovine rumen and hindgut in response to a step-wise increase in dietary starch and the influence of phytogenic supplementation

Microbial composition and activity in the gastrointestinal tract (GIT) of cattle has important implications for animal health and welfare, driving the focus of research toward ways to modify their function and abundance. However, our understanding of microbial adaption to nutritional changes remains limited. The aim of this study was to examine the progressive mechanisms of adaptation in the rumen and hindgut of cattle receiving increasing amounts of starch with or without dietary supplementation of a blended phytogenic feed additive (PFA; containing menthol, thymol and eugenol). We used 16S rRNA gene amplicon sequencing to assess the microbial composition and predicted metabolic pathways in ruminal solid and liquid digesta, and feces. Furthermore, we employed targeted liquid chromatography-mass spectrometry methods to evaluate rumen fluid metabolites. Results indicated a rapid microbial adaptation to diet change, starting on the second day of starch feeding for the particle associated rumen liquid (PARL) microbes. Solid rumen digesta- and feces-associated microbes started changing from the following day. The PARL niche was the most responsive to dietary changes, with the highest number of taxa and predicted pathways affected by the increase in starch intake, as well as by the phytogenic supplementation. Despite the differences in the microbial composition and metabolic potential of the different GIT niches, all showed similar changes toward carbohydrate metabolism. Metabolite measurement confirmed the high prevalence of glucose and volatile fatty acids (VFAs) in the rumen due to the increased substrate availability and metabolic activity of the microbiota. Families Prevotellaceae, Ruminococcaceae and Lachnospiraceae were found to be positively correlated with carbohydrate metabolism, with the latter two showing wide-ranging predicted metabolic capabilities. Phytogenic supplementation affected low abundant taxa and demonstrated the potential to prevent unwanted implications of feeding high-concentrate diet, such as reduction of microbial diversity. The inclusion of 50% concentrate in the diet caused a major shift in microbial composition and activity in the GIT of cattle. This study demonstrated the ability of microorganisms in various GIT niches to adjust differentially, yet rapidly, to changing dietary conditions, and revealed the potential beneficial effects of supplementation with a PFA during dietary adaptation.

Replacing concentrates with a high-quality hay in the starter feed in dairy calves: I. Effects on nutrient intake, growth performance, and blood metabolic profile

Concentrate-rich starter feeds are commonly fed to dairy calves to stimulate early solid feed intake and growth performance; yet, starter feeds lacking in forage fiber may jeopardize gut development. This research primarily aimed to test a complete or partial replacement of concentrates with hay of different qualities in the starter feed on nutrient intake, growth performance, apparent total-tract digestibility (ATTD) of nutrients, and blood metabolites in dairy calves. Immediately after birth, 40 Holstein Friesian calves were randomly allocated to 1 of 4 starter diets, which differed in hay quality and concentrate inclusion [MQH = 100% medium-quality hay, 9.4 MJ of metabolizable energy (ME), 149 g of crude protein (CP), 522 g of neutral detergent fiber (NDF)/kg of dry matter (DM); HQH = 100% high-quality hay, 11.2 MJ of ME, 210 g of CP, 455 g of NDF/kg of DM; MQH⁺C = 30% medium-quality hay + 70% starter concentrate; HQH⁺C = 30% high-quality hay + 70% starter concentrate]. The concentrate consisted mainly of grains, oilseeds, and mineral supplements (13.5 MJ of ME, 193 g of CP, 204 g of NDF/kg of DM). Calves were used in the experiment from d 1 to 99 of life. During the first 4 wk, all calves were fed acidified whole milk ad libitum, and afterward they were gradually weaned from wk 5 to 12. Calves had ad libitum access to their starter diets and water throughout the experiment. Milk, water, and solid feed intake was recorded daily, live weight was measured once a week, and blood samples were collected on d 1, 3, 7, 21, 49, 77, and 91 and analyzed for selected metabolites. The ATTD was measured in wk 14 of life. Total DM intake and daily weight gain of calves were not affected by the starter feed during the first 8 wk of life. However, from wk 9 to 14, calves fed the MQH diet had lower DM, ME, and CP intake and gained less weight than calves from the other experimental groups. Feeding the HQH diet resulted in similar CP and ME intake and growth performance compared with calves receiving diets containing concentrates. Furthermore, feeding the HQH diet improved the ATTD of NDF, resulting in similar ATTD of organic matter with the HQH⁺C and MQH⁺C groups. Interestingly, calves fed the HQH⁺C diet showed less sorting for concentrate, compared with the MQH⁺C group. Concentration of blood metabolites, including glucose, lactate, insulin, nonesterified fatty acids, triglycerides, and total protein, did not differ after the first week of life. However, serum β-hydroxybutyrate was higher in calves fed the HQH diet starting from wk 11. Both groups fed the hay-only diets maintained higher cholesterol levels after weaning compared with the groups fed hay-concentrate mixtures. In conclusion, feeding high-quality hay can fully replace starter concentrates in the feeding of dairy calves without adverse effects on performance during the rearing period, while increasing forage fiber intake and utilization, which enhanced ruminal ketogenesis and cholesterogenesis around weaning. Further research is needed to evaluate long-term effects of feeding high-quality hay on health and development of dairy calves, especially in terms of the observed improvements in ruminal ketogenesis and cholesterogenesis around weaning.

Dietary supplementation of thiamine enhances colonic integrity and modulates mucosal inflammation injury in goats challenged by lipopolysaccharide and low pH

The current study aimed to investigate the protective effects of dietary thiamine supplementation on the regulation of colonic integrity and mucosal inflammation in goats fed a high-concentrate (HC) diet. Twenty-four Boer goats (live weight of 35·62 (sem 2·4) kg) were allocated to three groups (CON: concentrate/forage = 30:70; HC; concentrate/forage = 70:30 and HCT: concentrate/forage = 70:30 with 200 mg thiamine/kg DMI) for 12 weeks. Results showed that compared with the HC treatment, the HCT group had a significantly higher ruminal pH value from 0 to 12 h after the feeding. The haematoxylin-eosin staining showed that desquamation and severe cellular damage were observed in the colon epithelium of the HC group, whereas the HCT group exhibited more structural integrity of the epithelial cell morphology. Compared with the HC treatment, the HCT group showed a markedly increase in pyruvate dehydrogenase and α-ketoglutarate dehydrogenase enzymes activity. The mRNA expressions in the colonic epithelium of SLC19A2, SLC19A3, SLC25A19, Bcl-2, occludin, claudin-1, claudin-4 and ZO-1 in the HCT group were significantly increased in comparison with the HC diet treatment. Compared with the HC treatment, the HCT diet significantly increased the protein expression of claudin-1 and significantly decreased the protein expression of NF-κB-related proteins p65. The results show that dietary thiamine supplementation could improve the colon epithelial barrier function and alleviate mucosal inflammation injury in goats after lipopolysaccharide and low pH challenge.

A Grain-Based SARA Challenge Affects the Composition of Epimural and Mucosa-Associated Bacterial Communities throughout the Digestive Tract of Dairy Cows

The effects of a subacute ruminal acidosis (SARA) challenge on the composition of epimural and mucosa-associated bacterial communities throughout the digestive tract were determined in eight non-lactating Holstein cows. Treatments included feeding a control diet containing 19.6% dry matter (DM) starch and a SARA-challenge diet containing 33.3% DM starch for two days after a 4-day grain step-up. Subsequently, epithelial samples from the rumen and mucosa samples from the duodenum, proximal, middle and distal jejunum, ileum, cecum and colon were collected. Extracted DNA from these samples were analyzed using MiSeq Illumina sequencing of the V4 region of the 16S rRNA gene. Distinct clustering patterns for each diet existed for all sites. The SARA challenge decreased microbial diversity at all sites, with the exception of the middle jejunum. The SARA challenge also affected the relative abundances of several major phyla and genera at all sites but the magnitude of these effects differed among sites. In the rumen and colon, the largest effects were an increase in the relative abundance of Firmicutes and a reduction of Bacteroidetes. In the small intestine, the largest effect was an increase in the relative abundance of Actinobacteria. The grain-based SARA challenge conducted in this study did not only affect the composition and cause dysbiosis of epimural microbiota in the rumen, it also affected the mucosa-associated microbiota in the intestines. To assess the extent of this dysbiosis, its effects on the functionality of these microbiota must be determined in future.

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

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

The Rumen Epithelial Microbiota: Possible Gatekeepers of the Rumen Epithelium and Its Potential Contributions to Epithelial Barrier Function and Animal Health and Performance

Ruminants are characterized by their unique mode of digesting cellulose-rich plant material in their forestomach, the rumen, which is densely populated by diverse microorganisms that are crucial for the breakdown of plant material. Among ruminal microbial communities, the microorganisms in the rumen fluid or attached to feed particles have attracted considerable research interest. However, comparatively less is known about the microorganisms attached to the rumen epithelium. Generally, the tissue lining the gastrointestinal tract serves the dual role of absorbing nutrients while preventing the infiltration of unwanted compounds and molecules as well as microorganisms. The rumen epithelium fulfills critical physiological functions for the ruminant host in energy absorption, metabolism, and nutrient transport. Essential host metabolites, such as short-chain fatty acids, ammonia, urea, and minerals, are exchanged across the rumen wall, thereby exposing the rumen epithelial microbiota to these nutrients. The integrity of the gastrointestinal barrier is central to animal health and productivity. The integrity of the rumen epithelium can be compromised by high ruminal microbial fermentation activity resulting in decreased rumen pH or by stress conditions such as heat stress or feed restriction. It is important to keep in mind that feeding strategies in cattle have changed over the last decades in favor of energy- and nutrient-rich concentrates instead of fiber-rich forages. These dietary shifts support high milk yields and growth rates but raised concerns regarding a possibly compromised rumen function. This paper will provide an overview of the composition of rumen epithelial microbial communities under physiological and disease conditions and will provide insights into the knowledge about the function and in situ activity of rumen epithelial microorganisms and their relevance for animal health and production. Given that an impaired intestinal barrier will negatively affect economically significant phenotypes, a better understanding of rumen wall microbiota is urgently needed.

Metatranscriptomic analyses reveal ruminal pH regulates fiber degradation and fermentation by shifting the microbial community and gene expression of carbohydrate-active enzymes

Background

Volatile fatty acids (VFA) generated from ruminal fermentation by microorganisms provide up to 75% of total metabolizable energy in ruminants. Ruminal pH is an important factor affecting the profile and production of VFA by shifting the microbial community. However, how ruminal pH affects the microbial community and its relationship with expression of genes encoding carbohydrate-active enzyme (CAZyme) for fiber degradation and fermentation are not well investigated. To fill in this knowledge gap, six cannulated Holstein heifers were subjected to a continuous 10-day intraruminal infusion of distilled water or a dilute blend of hydrochloric and phosphoric acids to achieve a pH reduction of 0.5 units in a cross-over design. RNA-seq based transcriptome profiling was performed using total RNA extracted from ruminal liquid and solid fractions collected on day 9 of each period, respectively.

Results

Metatranscriptomic analyses identified 19 bacterial phyla with 156 genera, 3 archaeal genera, 11 protozoal genera, and 97 CAZyme transcripts in sampled ruminal contents. Within these, 4 bacteria phyla (Proteobacteria, Firmicutes, Bacteroidetes, and Spirochaetes), 2 archaeal genera (Candidatus methanomethylophilus and Methanobrevibacter), and 5 protozoal genera (Entodinium, Polyplastron, Isotricha, Eudiplodinium, and Eremoplastron) were considered as the core active microbes, and genes encoding for cellulase, endo-1,4-beta- xylanase, amylase, and alpha-N-arabinofuranosidase were the most abundant CAZyme transcripts distributed in the rumen. Rumen microbiota is not equally distributed throughout the liquid and solid phases of rumen contents, and ruminal pH significantly affect microbial ecosystem, especially for the liquid fraction. In total, 21 bacterial genera, 4 protozoal genera, and 6 genes encoding CAZyme were regulated by ruminal pH. Metabolic pathways participated in glycolysis, pyruvate fermentation to acetate, lactate, and propanoate were downregulated by low pH in the liquid fraction.

Conclusions

The ruminal microbiome changed the expression of transcripts for biochemical pathways of fiber degradation and VFA production in response to reduced pH, and at least a portion of the shifts in transcripts was associated with altered microbial community structure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-021-00092-6.

Effect of an intramammary lipopolysaccharide challenge on the hindgut microbial composition and fermentation of dairy cattle experiencing intermittent subacute ruminal acidosis

Feeding grain-rich diets often results in subacute ruminal acidosis (SARA), a condition associated with ruminal dysbiosis and systemic inflammation. Yet, the effect of SARA on hindgut microbiota, and whether this condition is aggravated by exogenous immune stimuli, is less understood. Therefore, the aims of this study were to determine the effects of an intermittent high-grain SARA model on the hindgut microbial community, and to evaluate whether the effects of SARA on the fecal microbiome and fermentation were further affected by an intramammary lipopolysaccharide (LPS) challenge. A total of 18 early-lactating Simmental cows were divided into 3 groups (n = 6); 2 were fed a SARA-inducing feeding regimen (60% concentrate), 1 was fed a control (CON) diet (40% concentrate). On d 30, 1 SARA group (SARA-LPS) and the CON group (CON-LPS) were intramammarily challenged with a single dose of 50 µg of LPS from Escherichia coli O26:B6, whereas the remaining 6 SARA cows (SARA-PLA) received a placebo. Using a longitudinal randomized controlled design, with grouping according to parity and days in milk), statistical analysis was performed with baseline measurements used as a covariate in a mixed model procedure. The SARA-inducing feeding challenge resulted in decreased fecal pH and increased butyrate as a proportion of total short-chain fatty acids in the feces. On d 30, SARA-challenged cows had decreased fecal diversity as shown by the Shannon and Chao1 indices and a decrease in the relative abundance of Euryarchaeota and cellulolytic genera, and numerical increases in the relative abundance of several Firmicutes associated with starch and secondary fermentation. The LPS challenge did not affect the fecal pH and short-chain fatty acids, but increased the Chao1 richness index in an interaction with the SARA challenge, and affected the relative abundance of Verrucomicrobia (1.13%), Actinobacteria (0.19%), and Spirochaetes (0.002%), suggesting an effect on the microbial ecology of the hindgut during SARA conditions. In conclusion, the SARA-inducing feeding regimen promoted important microbial changes at d 30, including reduced diversity and evenness compared with CON, whereas the external LPS challenge led to changes in the microbial community without affecting fecal fermentation properties.

Longitudinal assessment revealed the shifts in rumen and colon mucosal-attached microbiota of dairy calves during weaning transition

The objectives of this study were to investigate the shifts in rumen and colon mucosa-associated microbiota in dairy calves fed a high milk replacer feeding rate before and after weaning and to determine whether such shifts are associated with tissue physiological measures. Longitudinal biopsy was performed to collect rumen and colon mucosal tissues of 4 ruminally cannulated Holstein dairy bull calves (weaned at 6 wk of age) at the end of wk 5 (before weaning), 7 (weaning adaptation) and 12 (after weaning), and were used to assess mucosa-associated microbiota and their changes using amplicon sequencing. Both rumen and colon mucosa-associated bacterial communities shifted during the weaning process, as evidenced by their clear separation among 3 different weaning periods and increased α diversity (Shannon and Chao1 indices) during weaning transition. Among the 3 dominant bacterial phyla identified (relative abundance >1.0%), the relative abundance of Proteobacteria and Bacteroidetes decreased in the rumen mucosa, whereas the relative abundance of Firmicutes increased in both rumen and colon mucosa during weaning transition. In the rumen mucosa, Campylobacter (0.6-22.1%) gradually became prevalent during weaning transition, whereas Succinivibrio (6.2-10.3%) and Prevotella 1 (4.7-10.5%) were dominant regardless of weaning transition. In the colon mucosa, Bacteroides (12.8-25.4%) was dominant during weaning transition, although its relative abundance decreased after weaning. In the meantime, relative abundance of uncultured Lachnospiraceae increased from 2.2% to 25.7% during this period. In addition, genera Pyramidobacter (in the rumen mucosa) and Lachnoclostridium (in the colon mucosa) were positively correlated with rumen papilla surface area and colon mucosal thickness, respectively. Moreover, genera Ruminococcaceae UCG-005 and Sharpea in the rumen mucosa were positively correlated with the molar proportion of propionate and butyrate, respectively. Overall, our findings revealed that rumen and colon mucosa-associated bacterial communities altered in response to the weaning transition, and some bacterial taxa in these communities may have positive effects on rumen and colon mucosa development during this period.

Rumen epithelial transcriptome and microbiome profiles of rumen epithelium and contents of beef cattle with and without liver abscesses

Abscess is the highest cause of liver condemnation and is estimated to cost the beef industry US$64 million annually. Fusobacterium necrophorum, commonly found in the bovine rumen, is the primary bacteria associated with liver abscess in cattle. Theoretically, damage to the rumen wall allows F. necrophorum to invade the bloodstream and colonize the liver. The objective of this study was to determine the changes in gene expression in the rumen epithelium and microbial populations adherent to the rumen epithelium and in the rumen contents of beef cattle with liver abscesses compared with those with no liver abscesses. Rumen epithelial tissue and rumen content were collected from 31 steers and heifers with liver abscesses and 30 animals with no liver abscesses. Ribonucleic acid (RNA) sequencing was performed on the rumen epithelium, and a total of 221 genes were identified as differentially expressed in the animals with liver abscesses compared with animals with no abscesses, after removal of genes that were identified as a result of interaction with sex. The nuclear factor kappa-light-chain enhancer of activated B cells signaling and interferon signaling pathways were significantly enriched in the differentially expressed gene (DEG) set. The majority of the genes in these pathways were downregulated in animals with liver abscesses. In addition, RNA translation and protein processing genes were also downregulated, suggesting that protein synthesis may be compromised in animals with liver abscesses. The rumen content bacterial communities were significantly different from the rumen wall epimural bacterial communities. Permutational multivariate analysis of variance (PERMANOVA) analysis did not identify global differences in the microbiome of the rumen contents but did identify differences in the epimural bacterial communities on the rumen wall of animals without and with liver abscesses. In addition, associations between DEG and specific bacterial amplicon sequence variants of epimural bacteria were observed. The DEG and bacterial profile on the rumen papillae identified in this study may serve as a method to monitor animals with existing liver abscesses or to predict those that are more likely to develop liver abscesses.

Unveiling the Bovine Epimural Microbiota Composition and Putative Function

Numerous studies have used the 16S rRNA gene target in an attempt to characterize the structure and composition of the epimural microbiota in cattle. However, comparisons between studies are challenging, as the results show large variations associated with experimental protocols and bioinformatics methodologies. Here, we present a meta-analysis of the rumen epimural microbiota from 11 publicly available amplicon studies to assess key technical and biological sources of variation between experiments. Using the QIIME2 pipeline, 332 rumen epithelial microbiota samples were analyzed to investigate community structure, composition, and functional potential. Despite having a significant impact on microbial abundance, country of origin, farm, hypervariable region, primer set, animal variability, and biopsy location did not obscure the identification of a core microbiota. The bacterial genera Campylobacter, Christensenellaceae R-7 group, Defluviitaleaceae UCG-011, Lachnospiraceae UCG-010, Ruminococcaceae NK4A214 group, Ruminococcaceae UCG-010, Ruminococcaceae UCG-014, Succiniclasticum, Desulfobulbus, and Comamonas spp. were found in nearly all epithelium samples (>90%). Predictive analysis (PICRUSt) was used to assess the potential functions of the epithelial microbiota. Regularized canonical correlation analysis identified several pathways associated with the biosynthesis of precursor metabolites in Campylobacter, Comamonas, Desulfobulbus, and Ruminococcaceae NK4A214, highlighting key metabolic functions of these microbes within the epithelium.

Effects of brewers' spent grain protein hydrolysates on gas production, ruminal fermentation characteristics, microbial protein synthesis and microbial community in an artificial rumen fed a high grain diet

BACKGROUND

Brewers' spent grain (BSG) typically contains 20% - 29% crude protein (CP) with high concentrations of glutamine, proline and hydrophobic and non-polar amino acid, making it an ideal material for producing value-added products like bioactive peptides which have antioxidant properties. For this study, protein was extracted from BSG, hydrolyzed with 1% alcalase and flavourzyme, with the generated protein hydrolysates (AlcH and FlaH) showing antioxidant activities. This study evaluated the effects of AlcH and FlaH on gas production, ruminal fermentation characteristics, nutrient disappearance, microbial protein synthesis and microbial community using an artificial rumen system (RUSITEC) fed a high-grain diet.

RESULTS

As compared to the control of grain only, supplementation of FlaH decreased (P < 0.01) disappearances of dry matter (DM), organic matter (OM), CP and starch, without affecting fibre disappearances; while AlcH had no effect on nutrient disappearance. Neither AlcH nor FlaH affected gas production or VFA profiles, however they increased (P < 0.01) NH3-N and decreased (P < 0.01) H2 production. Supplementation of FlaH decreased (P < 0.01) the percentage of CH4 in total gas and dissolved-CH4 (dCH4) in dissolved gas. Addition of monensin reduced (P < 0.01) disappearance of nutrients, improved fermentation efficiency and reduced CH4 and H2 emissions. Total microbial nitrogen production was decreased (P < 0.05) but the proportion of feed particle associated (FPA) bacteria was increased with FlaH and monensin supplementation. Numbers of OTUs and Shannon diversity indices of FPA microbial community were unaffected by AlcH and FlaH; whereas both indices were reduced (P < 0.05) by monensin. Taxonomic analysis revealed no effect of AlcH and FlaH on the relative abundance (RA) of bacteria at phylum level, whereas monensin reduced (P < 0.05) the RA of Firmicutes and Bacteroidetes and enhanced Proteobacteria. Supplementation of FlaH enhanced (P < 0.05) the RA of genus Prevotella, reduced Selenomonas, Shuttleworthia, Bifidobacterium and Dialister as compared to control; monensin reduced (P < 0.05) RA of genus Prevotella but enhaced Succinivibrio.

CONCLUSIONS

The supplementation of FlaH in high-grain diets may potentially protect CP and starch from ruminal degradation, without adversely affecting fibre degradation and VFA profiles. It also showed promising effects on reducing CH4 production by suppressing H2 production. Protein enzymatic hydrolysates from BSG using flavourzyme showed potential application to high value-added bio-products.

Adaptive responses in short-chain fatty acid absorption, gene expression, and bacterial community of the bovine rumen epithelium recovered from a continuous or transient high-grain feeding

The feeding of high-grain diets to dairy cows commonly results in lowered pH and ruminal dysbiosis, characterized by changes in absorption dynamics of short-chain fatty acids (SCFA) across the reticuloruminal wall, epithelial function, and the epithelial bacteria community structure. Therefore, the present study evaluated the effect of high-grain feeding persistence on the absorption kinetics of reticuloruminal SCFA, gene expression in the rumen epithelium, and the associated shifts in the epithelial bacteria in cows recovering from either a long-term continuous high-grain feeding model or a long-term transient high-grain feeding model. In a crossover study design, 8 nonlactating Holstein cows were fed 60% concentrate either continuously for 4 wk (continuous) or with a 1-wk break in the second week of the high-grain feeding (transient). After the high-grain feeding, all animals were fed a diet of 100% forage (recovery) for an additional 8 wk. Rumen papilla biopsies and SCFA absorption measurements were taken at the start of the trial (baseline), after the 4-wk high-grain feeding (49 d), after 2-wk recovery forage feeding (63 d), and after 8-wk recovery forage (105 d). Absorption of SCFA was determined in vivo using the washed and isolated reticulorumen technique. Rumen papillae biopsies were used for adherent bacterial DNA and host RNA extraction. The epithelial bacteria were determined using Illumina MiSeq (Microsynth AG, Balgach, Switzerland) sequencing of the 16S rRNA gene. No significant effects of the high-grain feeding model were seen for bacterial diversity. However, bacterial diversity increased with time spent in the recovery forage feeding period regardless of feeding model. The relative abundance of Acidobacteria phyla and Acetivibrio spp. increased when animals were fed a transient high-grain feeding model. A trend toward increased CLDN4 expression was observed in the continuous model. Furthermore, there were interactions between feeding model and sampling day for gene targets CD14, DRA, NHE2, NHE3, and MCT2. When comparing length of recovery, in the continuous model increased relative absorption of SCFA was sustained at 63 d but dropped to baseline measurements at 105 d. A similar pattern was found with the transient model but it did not reach significance. The only gene target that was found to significantly correlate to relative absorption of SCFA was DRA (correlation coefficient ≤ -0.41). Whereas, genera Alkalibaculum, Anaerorhabdus, Coprococcus, and Dethiobacter all showed positive correlations to gene targets for pH regulation (NHE2 and NHE3) and SCFA uptake (MCT1) but negative correlations to SCFA absorption. We conclude that while the rumen absorption and epithelial bacteria were able to recover to baseline levels after 8 wk of forage feeding, the time needed for re-establishment of homeostasis in host gene expression is longer, especially when high-grain feeding is interrupted.

A rapid shift to high-grain diet results in dynamic changes in rumen epimural microbiome in sheep

The rapid shift to high-grain (HG) diets in ruminants can affect the function of the rumen epithelium, but the dynamic changes in the composition of the epithelium-associated (epimural) bacterial community in sheep still needs further investigation. Twenty male lambs were randomly allocated to four groups (n = 5). Animals of the first group received hay diet and represented a control group (CON). Simultaneously, animals in the other three groups (HG groups) were rapidly shifted to an HG diet (60% concentrate)which continued for 7 (HG7), 14 (HG14) and 28 (HG28) days, correspondingly. Results showed that ruminal pH dramatically decreased due to the rapid shift to the HG diet (P <0.001), while, the concentrations of butyrate (P <0.001), lactate (P = 0.001), valerate (P = 0.008) and total volatile fatty acids (P = 0.001) increased. Diversity estimators showed a dramatic decrease after the shift without recovering as the HG feeding continued. The principal coordinates analysis showed that CON group clustered separately from all HG groups with the presence of significant difference only between HG7 and HG28 (P = 0.034). The non-parametric multivariate analysis (npmv R-package) deduced that the primary significant differences in phyla and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt)-predicted Kyoto Encyclopedia of Genes and Genomes (KEGGs) was attributed mainly to the diet composition (P <0.001, P = 0.001) compared to its application period (P = 0.140, 0.545) which showed a significant effect only on the genus (P = 0.001) and the operational taxonomic units (OTUs) level (P = 0.011). The Kruskal-Wallis test deduced that six phyla showed a significant effect due to the shift in diet composition. At the genus level, HG feeding altered the abundance of 12 taxa, four of which showed a significant variation due to the duration of the HG diet application. Similarly, we found that 21 OTUs showed significant variations due to the duration of the HG diet application. Furthermore, the genes abundance predicted by PICRUSt revealed that the HG feeding significantly affected seven metabolic pathways identified in the KEGG. Particularly, the abundance of gene families associated with carbohydrates metabolism were significantly higher in HG feeding groups (P = 0.027). Collectively, these results revealed that the rapid transition to an HG diet causes dramatic alterations in ruminal fermentation and the composition and function of ruminal epithelium-associated microbiome in sheep, while, the duration of the HG diet application causes drastic alterations to the abundance of some species.

Symposium review: Microbial endocrinology-Why the integration of microbes, epithelial cells, and neurochemical signals in the digestive tract matters to ruminant health

The union of microbiology and neurobiology, which has been termed microbial endocrinology, is defined as the study of the ability of microorganisms to produce and respond to neurochemicals that originate either within the microorganisms themselves or within the host they inhabit. It serves as the basis for an evolutionarily derived method of communication between a host and its microbiota. Mechanisms elucidated by microbial endocrinology give new insight into the ways the microbiota can affect host stress, metabolic efficiency, resistance to disease, and other factors that may prove relevant to the dairy industry.

Metatranscriptome Sequencing Reveals Insights into the Gene Expression and Functional Potential of Rumen Wall Bacteria

Microbiota of the rumen wall constitute an important niche of rumen microbial ecology and their composition has been elucidated in different ruminants during the last years. However, the knowledge about the function of rumen wall microbes is still limited. Rumen wall biopsies were taken from three fistulated dairy cows under a standard forage-based diet and after 4 weeks of high concentrate feeding inducing a subacute rumen acidosis (SARA). Extracted RNA was used for metatranscriptome sequencing using Illumina HiSeq sequencing technology. The gene expression of the rumen wall microbial community was analyzed by mapping 35 million sequences against the Kyoto Encyclopedia for Genes and Genomes (KEGG) database and determining differentially expressed genes. A total of 1,607 functional features were assigned with high expression of genes involved in central metabolism, galactose, starch and sucrose metabolism. The glycogen phosphorylase (EC:2.4.1.1) which degrades (1->4)-alpha-D-glucans was among the highest expressed genes being transcribed by 115 bacterial genera. Energy metabolism genes were also highly expressed, including the pyruvate orthophosphate dikinase (EC:2.7.9.1) involved in pyruvate metabolism, which was covered by 177 genera. Nitrogen metabolism genes, in particular glutamate dehydrogenase (EC:1.4.1.4), glutamine synthetase (EC:6.3.1.2) and glutamate synthase (EC:1.4.1.13, EC:1.4.1.14) were also found to be highly expressed and prove rumen wall microbiota to be actively involved in providing host-relevant metabolites for exchange across the rumen wall. In addition, we found all four urease subunits (EC:3.5.1.5) transcribed by members of the genera Flavobacterium, Corynebacterium, Helicobacter, Clostridium, and Bacillus, and the dissimilatory sulfate reductase (EC 1.8.99.5) dsrABC, which is responsible for the reduction of sulfite to sulfide. We also provide in situ evidence for cellulose and cellobiose degradation, a key step in fiber-rich feed digestion, as well as oxidative stress response and oxygen scavenging at the rumen wall. Archaea, mainly Methanocaldococcus and Methanobrevibacter, were found to be metabolically active with a high number of transcripts matching to methane and carbohydrate metabolism. These findings enhance our understanding of the metabolic function of the bovine rumen wall microbiota.

Illumina Sequencing Approach to Characterize Thiamine Metabolism Related Bacteria and the Impacts of Thiamine Supplementation on Ruminal Microbiota in Dairy Cows Fed High-Grain Diets

The requirements of thiamine in adult ruminants are mainly met by ruminal bacterial synthesis, and thiamine deficiencies will occur when dairy cows overfed with high grain diet. However, there is limited knowledge with regard to the ruminal thiamine synthesis bacteria, and whether thiamine deficiency is related to the altered bacterial community by high grain diet is still unclear. To explore thiamine synthesis bacteria and the response of ruminal microbiota to high grain feeding and thiamine supplementation, six rumen-cannulated Holstein cows were randomly assigned into a replicated 3 × 3 Latin square design trial. Three treatments were control diet (CON, 20% dietary starch, DM basis), high grain diet (HG, 33.2% dietary starch, DM basis) and high grain diet supplemented with 180 mg thiamine/kg DMI (HG+T). On day 21 of each period, rumen content samples were collected at 3 h postfeeding. Ruminal thiamine concentration was detected by high performance liquid chromatography. The microbiota composition was determined using Illumina MiSeq sequencing of 16S rRNA gene. Cows receiving thiamine supplementation had greater ruminal pH value, acetate and thiamine content in the rumen. Principal coordinate analysis and similarity analysis indicated that HG feeding and thiamine supplementation caused a strong shift in bacterial composition and structure in the rumen. At the genus level, compared with CON group, the relative abundances of 19 genera were significantly changed by HG feeding. Thiamine supplementation increased the abundance of cellulolytic bacteria including Bacteroides, Ruminococcus 1, Pyramidobacter, Succinivibrio, and Ruminobacter, and their increases enhanced the fiber degradation and ruminal acetate production in HG+T group. Christensenellaceae R7, Lachnospira, Succiniclasticum, and Ruminococcaceae NK4A214 exhibited a negative response to thiamine supplementation. Moreover, correlation analysis revealed that ruminal thiamine concentration was positively correlated with Bacteroides, Ruminococcus 1, Ruminobacter, Pyramidobacter, and Fibrobacter. Taken together, we concluded that Bacteroides, Ruminococcus 1, Ruminobacter, Pyramidobacter, and Fibrobacter in rumen content may be associated with thiamine synthesis or thiamine is required for their growth and metabolism. In addition, thiamine supplementation can potentially improve rumen function, as indicated by greater numbers of cellulolytic bacteria within the rumen. These findings facilitate understanding of bacterial thiamine synthesis within rumen and thiamine's function in dairy cows.

Metagenomic investigation of gastrointestinal microbiome in cattle

The gastrointestinal (GI) tract, including the rumen and the other intestinal segments of cattle, harbors a diverse, complex, and dynamic microbiome that drives feed digestion and fermentation in cattle, determining feed efficiency and output of pollutants. This microbiome also plays an important role in affecting host health. Research has been conducted for more than a century to understand the microbiome and its relationship to feed efficiency and host health. The traditional cultivation-based research elucidated some of the major metabolism, but studies using molecular biology techniques conducted from late 1980’s to the late early 2000’s greatly expanded our view of the diversity of the rumen and intestinal microbiome of cattle. Recently, metagenomics has been the primary technology to characterize the GI microbiome and its relationship with host nutrition and health. This review addresses the main methods/techniques in current use, the knowledge gained, and some of the challenges that remain. Most of the primers used in quantitative real-time polymerase chain reaction quantification and diversity analysis using metagenomics of ruminal bacteria, archaea, fungi, and protozoa were also compiled.

Changes in the rumen bacterial microbiome of cattle exposed to ponderosa pine needles

Consumption of ponderosa pine needles, as well as needles and bark from a number of other trees, can cause abortions in cattle. The abortifacient compounds in these trees are labdane resin acids, including isocupressic acid and agathic acid. Previous research has demonstrated that cattle conditioned to pine needles metabolize the labdane resin acids more quickly than naïve cattle. The results from that study indicated that changes had occurred in the rumen of conditioned cattle. Therefore, in this study, the changes that occurred in the rumen bacterial microflora of cattle during exposure to ponderosa pine needles were evaluated. Cattle were dosed with ground pine needles twice daily for 7 d. Rumen samples were collected on d 0, 3, 7, and 14 (7 d after treatment stopped) and ruminal bacterial microbiome analyses were performed. There were 372 different genera of bacteria identified in the rumen samples. Principal coordinate analysis indicated that there was a significant difference in the rumen bacterial composition between the time points. There were 18 genera that increased in abundance from d 0 to d 7. Twenty three genera decreased in abundance from d 0 to d 7. The results from this study demonstrated that exposure of cattle to pine needles caused a clear shift in the rumen microbiome composition. In general, this shift lasted less than 1 wk post exposure, which indicates that any prophylactic treatment to manipulate the ruminal metabolism of the abortifacient compounds in pine needles would need to be continuously administered to maintain the necessary microbial composition in the rumen.

Induction of a transient acidosis in the rumen simulation technique

Feeding high concentrate diets to cattle results in an enhanced production of short-chain fatty acids by the micro-organisms in the rumen. Excessive fermentation might result in subclinical or clinical rumen acidosis, characterized by low pH, alterations in the microbial community and lactate production. Here, we provide an in vitro model of a severe rumen acidosis. A transient acidosis was induced in the rumen simulation technique by lowering bicarbonate, dihydrogen phosphate and hydrogen phosphate concentrations in the artificial saliva while providing a concentrate-to-forage ratio of 70:30. The experiment consisted of an equilibration period of 7 days, a first control period of 5 days, the acidosis period of 5 days and a second control period of 5 days. During acidosis induction, pH decreased stepwise until it ranged below 5.0 at the last day of acidosis (day 17). This was accompanied by an increase in lactate production reaching 11.3 mm at day 17. The daily production of acetate, propionate and butyrate was reduced at the end of the acidosis period. Gas production (methane and carbon dioxide) and NH₃ -N concentration reached a minimum 2 days after terminating the acidosis challenge. While the initial pH was already restored 1 day after acidosis, alterations in the mentioned fermentation parameters lasted longer. However, by the end of the experiment, all parameters had recovered. An acidosis-induced alteration in the microbial community of bacteria and archaea was revealed by single-strand conformation polymorphism. For bacteria, the pre-acidotic community could be re-established within 5 days, however, not for archaea. This study provides an in vitro model for a transient rumen acidosis including biochemical and microbial changes, which might be used for testing feeding strategies or feed additives influencing rumen acidosis.

Epimural bacterial community structure in the rumen of Holstein cows with different responses to a long-term subacute ruminal acidosis diet challenge

Subacute ruminal acidosis (SARA) is a prevalent metabolic disorder in cattle, characterized by intermittent drops in ruminal pH. This study investigated the effect of a gradual adaptation and continuously induced long-term SARA challenge diet on the epimural bacterial community structure in the rumen of cows. Eight rumen-cannulated nonlactating Holstein cows were transitioned over 1 wk from a forage-based baseline feeding diet (grass silage-hay mix) to a SARA challenge diet, which they were fed for 4 wk. The SARA challenge diet consisted of 60% concentrates (dry matter basis) and 40% grass silage-hay mix. Rumen papillae biopsies were taken at the baseline, on the last day of the 1-wk adaptation, and on the last day of the 4-wk SARA challenge period; ruminal pH was measured using wireless sensors. We isolated DNA from papillae samples for 16S rRNA gene amplicon sequencing using Illumina MiSeq. Sequencing results of most abundant key phylotypes were confirmed by quantitative PCR. Although they were fed similar amounts of concentrate, cows responded differently in terms of ruminal pH during the SARA feeding challenge. Cows were therefore classified as responders (n = 4) and nonresponders (n = 4): only responders met the SARA criterion of a ruminal pH drop below 5.8 for longer than 330 min/d. Data showed that Proteobacteria, Firmicutes, and Bacteroidetes were the most abundant phyla, and at genus level, Campylobacter and Kingella showed highest relative abundance, at 15.5 and 7.8%, respectively. Diversity analyses revealed a significant increase of diversity after the 1-wk adaptation but a decrease of diversity and species richness after the 4-wk SARA feeding challenge, although without distinction between responders and nonresponders. At the level of the operational taxonomic unit, we detected diet-specific shifts in epimural community structure, but in the overall epimural bacterial community structure, we found no differences between responders and nonresponders. Correlation analysis revealed significant associations between grain intake and operational taxonomic unit abundance. The study revealed major shifts in the 3 dominating phyla and, most importantly, a loss of diversity in the epimural bacterial communities during a long-term SARA diet challenge, in which 60% concentrate supply for 4 wk was instrumental rather than the magnitude of the drop of ruminal pH below 5.8.

Intramammary infusion of Escherichia coli lipopolysaccharide negatively affects feed intake, chewing, and clinical variables, but some effects are stronger in cows experiencing subacute rumen acidosis

Feeding high-grain diets increases the risk of subacute rumen acidosis (SARA) and adversely affects rumen health. This condition might impair the responsiveness of cows when they are exposed to external infectious stimuli such as lipopolysaccharide (LPS). The main objective of this study was to evaluate various responses to intramammary LPS infusion in healthy dairy cows and those experimentally subjected to SARA. Eighteen early-lactating Simmental cows were subjected to SARA (n = 12) or control (CON; n = 6) feeding conditions. Cows of the control group received a diet containing 40% concentrates (DM basis) throughout the experiment. The intermittent SARA feeding regimen consisted in feeding the cows a ration with 60% concentrate (DM basis) for 32 d, consisting of a first SARA induction for 8 d, switched to the CON diet for 7 d, and re-induction during the last 17 d. On d 30 of the experiment, 6 SARA (SARA-LPS) and 6 CON (CON-LPS) cows were intramammary challenged once with a single dose of 50 μg of LPS from Escherichia coli (O26:B6), whereas the other 6 SARA cows (SARA-PLA) received 10 mL of sterile saline solution as placebo. To confirm the induction of SARA, the reticular pH was continuously monitored via wireless pH probes. The DMI remained unchanged between SARA and CON cows during the feeding experiment, but was reduced in both treatment groups receiving the LPS infusion compared with SARA-PLA, whereby a significant decline was observed for cows of the SARA-LPS treatment (-38%) compared with CON-LPS (-19%). The LPS infusion did not affect the reticuloruminal pH dynamics, but significantly enhanced ruminal temperature and negatively affected chewing behavior. The ruminal temperature increased after the LPS infusion and peaked about 1 h earlier in SARA-LPS cows compared with the cows of the CON-LPS treatment. Moreover, a significant decline in milk yield was found in SARA-LPS compared with CON-LPS following the LPS infusion. Cows receiving LPS had elevated somatic cell counts, protein, and fat contents in milk as well as decreased lactose contents and pH following the LPS infusion, whereby the changes in milk constituents were more pronounced in SARA-LPS than CON-LPS cows. Rectal temperature and pulse rate were highest 6 h after LPS infusion, but rumen contractions were not affected by the LPS infusion. The data suggest that a single intramammary LPS infusion induced fever and negatively affected feed intake, chewing activity, rectal temperature, and milk yield and composition, whereby these effects were more pronounced in SARA cows.