Ruminant Nutrition Symposium: Role of fermentation acid absorption in the regulation of ruminal pH

Long-term high-grain diet alters ruminal pH, fermentation, and epithelial transcriptomes, leading to restored mitochondrial oxidative phosphorylation in Japanese Black cattle

To increase intramuscular fat accumulation, Japanese Black beef cattle are commonly fed a high-grain diet from 10 to 30 months of age. Castrated and fistulated cattle (n = 9) were fed a high-concentrate diets during the early, middle, and late stages consecutively (10-14, 15-22, 23-30 months of age, respectively). Ruminal pH was measured continuously, and rumen epithelium and fluid samples were collected on each stage. The 24-h mean ruminal pH during the late stage was significantly lower than that during the early stage. Total volatile fatty acid (VFA) and lactic acid levels during the late stage were significantly lower and higher, respectively, than those during the early and middle stages. In silico analysis of differentially expressed genes showed that "Oxidative Phosphorylation" was the pathway inhibited most between the middle and early stages in tandem with an inhibited upstream regulator (PPARGC1A, also called PGC-1α) but the most activated pathway between the late and middle stages. These results suggest that mitochondrial dysfunction and thereby impaired cell viability due to acidic irritation under the higher VFA concentration restored stable mitochondrial oxidative phosphorylation and cell viability by higher lactic acid levels used as cellular oxidative fuel under a different underlying mechanism in subacute ruminal acidosis.

Propionate enhances the expression of key genes involved in the gluconeogenic pathway in bovine intestinal epithelial cells

Approximately 15 to 50% of short-chain fatty acids (SCFA) reach the ruminant small intestine. Previous research suggests that activation of small intestinal gluconeogenesis induced by propionate has beneficial effects on energy homeostasis. However, the regulatory effect of propionate on key gluconeogenic genes in enterocytes of the bovine small intestine remains less known. Therefore, the purpose of this study was to establish the long-term cultures of bovine intestinal epithelial cells (BIEC) from bovine jejunum tissue using SV40T (1:200; Santa Cruz, Shanghai, China) and investigate the regulatory effect of propionate on the key gluconeogenic genes in BIEC. Our study showed that long-term BIEC cultures were established by SV40T-induced immortalization. Immortal BIEC were distinguished by the expression of cytokeratin 18, villin, fatty acid binding protein 2, and small intestine peptidase. The mRNA expression of genes involved in the SCFA transporters, monocarboxylate transporter 4, and Na⁺/H⁺ exchanger isoforms 1 were significantly elevated with 20 mM SCFA compared with untreated controls. In addition, BIEC exhibited significant uptake of propionate and butyrate from the culture medium. Remarkably, 3 mM propionate induced profound changes in mRNA level of key genes involved in gluconeogenesis, including phosphoenolpyruvate carboxykinase 2, pyruvate carboxylase, fructose-1,6-bisphosphatase 1, and peroxisome proliferator-activated receptor-γ coactivator 1α. Additionally, 3 mM propionate enhanced the expression of PGC1A mRNA at 3, 6, 12, and 24 h of incubation. These findings suggest that propionate controls the mRNA expression of genes involved in key enzymes for gluconeogenesis in the enterocytes of bovines.

Notice of RETRACTION: Changes in rumen fermentation, bacterial community, and predicted functional pathway in Holstein cows with and without subacute ruminal acidosis during the periparturient period

The authors have elected to retract this paper in accordance with the following points. The article as written contains misleading information and omits important details. Cows in this study were assigned to groups based on the current definition of subacute ruminal acidosis; they were housed on two different farms and fed two different sets of rations in this study. However, multiple farms were not described in the materials and methods and this was not accounted for in the statistical analysis as published. The diets shown in Table 1 were not actually fed to animals; rather, the proportions of ingredients listed represent an average of the two farms housing the cows. The authors regret the errors.

Effects of replacing starch with three sugars in a concentrate and forage diet on in vitro rumen fermentation, fatty acid composition and related bacteria

Context Replacing starch with sugar could maintain dietary energy density with reduced risks of rumen acidosis and milk fat depression, but the underlying mechanism is not well understood, and the effects of sugar feeding might vary among sugars. Aims Objectives of the present study were to evaluate the effects of replacing corn starch in a diet containing 40:60 forage-to-concentrate ratio (control) with 3%, 6% and 9% of sucrose, fructose and lactose on in vitro rumen fermentation, fatty acid (FA) composition and populations of bacteria involved in the production of trans-11 and trans-10 FA. Methods A 3 × 3 + 1 (control) factorial experimental design was used, and the pH, concentrations of volatile fatty acids (VFA) and ammonia-N, profiles of FA and the relative abundance of four trans-11-producing bacteria and two trans-10 FA-producing bacteria were measured after a 6-h incubation. Key results Replacing dietary corn starch with sucrose, fructose and lactose neither altered the concentration of total VFA after 6-h fermentation, nor decreased the pH, except for substitution with 9% sucrose. Increased butyrate proportions and decreased branched-chain VFA proportions were the common effects in sugar treatments, but the proportions of acetate and propionate varied among sugars. Lactose inclusion in the diet led to a higher pH, greater acetate and butyrate concentrations, and lower propionate concentrations than did sucrose inclusion. Sugar substitution decreased the concentrations of C18:1 trans-4 and most C18:2 isomers, but did not influence the major isomers related to trans-11 and trans-10 biohydrogenation pathways. Abundance of the four measured trans-11 FA-producing bacteria was increased by sugars, with sucrose showing a greater influence than did fructose and lactose. As to trans-10 FA-producing bacteria, only Megasphaera elsdenii populations were decreased by 3% and 6% fructose inclusion compared with the control. Dose-effect varied among sugars and the parameters measured, with sucrose having the most obvious dose effect among the three sugars; however, fructose affected mainly fermentation parameters, while lactose affected mainly C18 FA profiles. Conclusions Replacing corn starch in a high-concentrate diet with up to 9% of sucrose, fructose and lactose differentially affected rumen fermentation and rumen FA metabolism, by influencing the abundance of rumen bacteria involved in rumen FA biohydrogenation. Implications Lactose may be more efficient in increasing milk fat than are sucrose and fructose, and dose effect should be considered in the utilisation of sucrose.

Effect of feeding barley or corn silage with dry-rolled barley, corn, or a blend of barley and corn grain on rumen fermentation, total tract digestibility, and nitrogen balance for finishing beef heifers

Five ruminally cannulated heifers were used in an incomplete 6 × 6 Latin square design to determine the effects of cereal silage (barley vs. corn), cereal grain (barley vs. corn vs. a 50:50 blend of barley and corn), and their interaction (S × G) on dry matter intake, ruminal fermentation, total tract digestibility, nitrogen balance, and in situ degradation. Corn silage (CS) or barley silage (BS) was included at 8% of dietary dry matter (DM). Within each silage source, diets contained (DM basis) either dry-rolled barley (BG; 86%), dry-rolled corn (CG; 85%), or an equal blend of barley and corn (BLEND; 85%). Periods were 25 d, with 5 d of dietary transition, 13 d of dietary adaptation, and 7 d of data and sample collection. Samples collected included feed and refusals, total urine and feces, and ruminal fluid. All data were analyzed using the Mixed model of SAS with the fixed effects of silage, grain, and the S × G. Dry matter intake (P ≥ 0.19) and mean ruminal pH (P ≥ 0.096) were not affected by the silage, grain, or S × G. Total short-chain fatty acid concentrations were greater for BLEND than BG or CG (grain, P = 0.003) and for CS (silage, P = 0.009) relative to BS. The molar proportion of acetate was greater for BS-BG and BS-CG (S × G, P < 0.001), while molar proportion of propionate was greater for CS-BG (S × G, P < 0.001) relative to other silage and grain source combinations. Rumen ammonia-N concentration was greater for CG than BG, or BLEND (grain, P < 0.001), and greater for CS compared to BS (silage, P = 0.023). Apparent total tract digestibility of DM, organic matter, neutral detergent fiber, starch, and gross energy were greatest for BG (grain, P ≤ 0.035). Digestible energy content (Mcal/kg) was greater for BG (grain, P = 0.029) than CG and BLEND. Total nitrogen retention (g/d and % of intake) was greatest for CS-BG (S × G, P ≤ 0.033) relative to all other treatments. In situ degradation rates of DM, crude protein, and starch were greater for BG than CG (P ≤ 0.004). The potentially degradable fraction of DM, crude protein, and starch was greater for CG (P ≤ 0.031), while the undegradable fraction was greater for BG (P ≤ 0.046). For silage sources, CS had greater 24 h in situ DM digestibility (P = 0.009) and starch digestibility (24, 48, and 72 h incubations, P ≤ 0.034) relative to BS. Results suggest that while feeding a combination of CS and BG promotes propionate production and greater N retention; few other additive effects were observed.

Postmortem observations on rumen wall histology and gene expression and ruminal and caecal content of beef cattle fattened on barley-based rations

Sub-acute ruminal acidosis (SARA) can reduce the production efficiency and impair the welfare of cattle, potentially in all production systems. The aim of this study was to characterise measurable postmortem observations from divergently managed intensive beef finishing farms with high rates of concentrate feeding. At the time of slaughter, we obtained samples from 19 to 20 animals on each of 6 beef finishing units (119 animals in total) with diverse feeding practices, which had been subjectively classified as being high risk (three farms) or low risk (three farms) for SARA on the basis of the proportions of barley, silage and straw in the ration. We measured the concentrations of histamine, lipopolysaccharide (LPS), lactate and other short-chain fatty acids (SCFAs) in ruminal fluid, LPS and SCFA in caecal fluid. We also took samples of the ventral blind sac of the rumen for histopathology, immunohistopathology and gene expression. Subjective assessments were made of the presence of lesions on the ruminal wall, the colour of the lining of the ruminal wall and the shape of the ruminal papillae. Almost all variables differed significantly and substantially among farms. Very few pathological changes were detected in any of the rumens examined. The animals on the high-risk diets had lower concentrations of SCFA and higher concentrations of lactate and LPS in the ruminal fluid. Higher LPS concentrations were found in the caecum than the rumen but were not related to the risk status of the farm. The diameters of the stratum granulosum, stratum corneum and of the vasculature of the papillae, and the expression of the gene TLR4 in the ruminal epithelium were all increased on the high-risk farms. The expression of IFN-γ and IL-1β and the counts of cluster of differentiation 3 positive and major histocompatibility complex class two positive cells were lower on the high-risk farms. High among-farm variation and the unbalanced design inherent in this type of study in the field prevented confident assignment of variation in the dependent variables to individual dietary components; however, the CP percentage of the total mixed ration DM was the factor that was most consistently associated with the variables of interest. Despite the strong effect of farm on the measured variables, there was wide inter-animal variation.

Tibetan sheep have a high capacity to absorb and to regulate metabolism of SCFA in the rumen epithelium to adapt to low energy intake

The nutritional intake of Tibetan sheep on the harsh Qinghai-Tibetan Plateau is often under maintenance requirements, especially during the long, cold winter. However, they have adapted well and even thrive under these conditions. The aim of the present study was to gain insight into how the rumen epithelium of Tibetan sheep has adapted to the consumption of low-energy-level diets. For this purpose, we compared Tibetan and small-tailed Han sheep (n 24 of each breed, all wethers and 1·5 years of age), which were divided randomly into one of four groups and offered ad libitum diets of different digestible energy (DE) densities: 8·21, 9·33, 10·45 and 11·57 MJ DE/kg DM. The Tibetan sheep had higher rumen concentrations of total SCFA, acetate, butyrate and iso-acids but lower concentrations of propionate than small-tailed Han sheep. The Tibetan sheep had higher absorption capability of SCFA due to the greater absorption surface area and higher mRNA expression of the SCFA absorption relative genes than small-tailed Han sheep. For the metabolism of SCFA in the rumen epithelium, the small-tailed Han sheep showed higher utilisation of the ketogenesis pathway than Tibetan sheep; however, Tibetan sheep had greater regulation capacity in SCFA metabolism pathways. These differences between breeds allowed the Tibetan sheep to have greater capability of absorbing SCFA and better capacity to regulate the metabolism of SCFA, which would allow them to cope with low energy intake better than small-tailed Han sheep.

Does pellet size affect the ability of beef heifers to consume a pelleted supplement in a simulated grazing model?

The objective was to evaluate pellet consumption and refusals as affected by pellet size. Six ruminally cannulated heifers were used in a replicated 3 × 3 Latin square. Heifers were individually housed and fed a diet of grass hay (57.5%), mineral and vitamin supplement (8.0%), and canola meal (11.9%) in a feed bunk, and their respective wheat- and wheat-middling-based treatment pellet (22.7%) on artificial turf. The artificial turf had a mean staple length of 5 cm and a blade density of 45 blades cm−2. The pellets were small (SM; 4 mm diameter), medium (MED; 11 mm diameter), or large (LG; 50 mm diameter) in size. Heifers fed LG had greater pellet intake than SM (2.24 vs. 2.06 kg; P = 0.035), with MED being intermediate (2.12 kg). Heifers fed LG tended to have less pellet waste than SM (P = 0.074). Heifers fed MED pellets had greater concentration of ruminal short-chain fatty acids than SM and LG (91.3 vs. 84.7 and 89.0 mmol L−1; P = 0.009). The results indicate that feeding a LG pellet may increase intake and reduce waste compared with SM, and that pellet size may also affect ruminal fermentation.

Effect of altering ruminal pH by dietary buffer supplementation on methane emissions from sheep fed forage rape

Low methane (CH4) emissions from sheep fed forage rape (Brassica napus) might be related to low ruminal pH value. In this study, sodium carbonate (Na2CO3: SC) was supplemented to the diet to alter ruminal pH for evaluation of its role in CH4 emissions from sheep fed forage rape. Fourteen intact and eight fistulated Romney sheep were adapted to forage rape over 32 days and then randomly allocated to one of two groups: diets supplemented with SC or not (control). Methane emissions were measured from intact sheep in seven experimental periods. In parallel, ruminal pH and fermentation characteristics were assessed using the fistulated sheep. In the first (P01) and the second (P02) periods, none of the sheep received SC to examine the baseline CH4 emissions. The P01 period was used as a covariate for analysis of gas emission measurements in subsequent measurement periods. Sodium carbonate was offered at 5% of the forage DM in P03 and P04, increased to 8% in P05 and P06 to assess the effect of pH increase on CH4 emissions and stopped in P07 to assess if the CH4 emissions reverted to values similar to those measured before the supplementation started. Methane yield (g/kg forage DM intake) was similar for the sheep in both groups during P02 and P03, but sheep supplemented with SC in the diet emitted 36%, 49% and 30% more CH4 per unit of forage DM intake than those in the control group during P04, P05 and P06, respectively. Emissions returned to similar levels when SC supplementation was ceased in P07. Ruminal pH was 0.412 to 0.565 units higher in SC supplemented sheep than for the control group during the SC treatment periods. Based on the lack of an immediate response in CH4 emissions to the supplementation of SC in P03, the positive responses in P04 to P06 and the rapid disappearance of the response after supplementation with SC stopped in P07, we propose a new hypothesis that ruminal pH effects on CH4 emissions are possibly through medium-term changes in microbial and methanogenic communities in the rumen, rather than a direct, short-term impact on methanogens per se. In conclusion, SC supplemented to the forage rape diet of sheep increased rumen pH, leading to an increase in CH4 emissions. Low ruminal pH in sheep fed forage rape explains, at least partially, the reported low CH4 emissions from sheep fed with this forage crop.

Dynamic role of single-celled fungi in ruminal microbial ecology and activities

In ruminants, high fermentation capacity is necessary to develop more efficient ruminant production systems. Greater level of production depends on the ability of the microbial ecosystem to convert organic matter into precursors of milk and meat. This has led to increased interest by animal nutritionists, biochemists and microbiologists in evaluating different strategies to manipulate the rumen biota to improve animal performance, production efficiency and animal health. One of such strategies is the use of natural feed additives such as single-celled fungi yeast. The main objectives of using yeasts as natural additives in ruminant diets include; (i) to prevent rumen microflora disorders, (ii) to improve and sustain higher production of milk and meat, (iii) to reduce rumen acidosis and bloat which adversely affect animal health and performance, (iv) to decrease the risk of ruminant-associated human pathogens and (v) to reduce the excretion of nitrogenous-based compounds, carbon dioxide and methane. Yeast, a natural feed additive, has the potential to enhance feed degradation by increasing the concentration of volatile fatty acids during fermentation processes. In addition, microbial growth in the rumen is enhanced in the presence of yeast leading to the delivery of a greater amount of microbial protein to the duodenum and high nitrogen retention. Single-celled fungi yeast has demonstrated its ability to increase fibre digestibility and lower faecal output of organic matter due to improved digestion of organic matter, which subsequently improves animal productivity. Yeast also has the ability to alter the fermentation process in the rumen in a way that reduces methane formation. Furthermore, yeast inclusion in ruminant diets has been reported to decrease toxins absorption such as mycotoxins and promote epithelial cell integrity. This review article provides information on the impact of single-celled fungi yeast as a feed supplement on ruminal microbiota and its function to improve the health and productive longevity of ruminants.

Efficacy of sodium butyrate in alleviating mammary oxidative stress induced by sub-acute ruminal acidosis in lactating goats

Sub-acute ruminal acidosis (SARA) [1] is one of the most common problems of dairy animals causing great economical loss due to decreased milk production. Here we determined the antioxidant effect of sodium butyrate (NaB) [2] in experimentally induced SARA and its effects on mammary epithelial tissues of goat. Goats (n = 12) were equally divided into two groups: high-concentrate (HC) as control group fed with HC diet (concentrate: forage = 6:4) whereas HC + NaB as treatment group fed HC diet with NaB at 1% by weight for 24 weeks. Mammary epithelial tissue samples were analyzed for the expression of genes and proteins responsible for oxidative stress as well as biochemical markers of antioxidant activity in the form of Reactive Oxygen Species (ROS). The total antioxidant capacity (T-AOC) of antioxidant enzymes was also calculated. Butyrate induced antioxidant effect by increasing mRNA and protein abundance of antioxidants in mammary gland of HC + NaB group compared to HC group. Likewise, the total antioxidant capacity (T-AOC) was significantly increased and Malondialdehyde (MDA) concentration was decreased in HC + NaB group compared to HC group. It is concluded that oxidative stress in mammary gland of goats induced by high concentrate diet was alleviated by NaB supplementation.

Invited Review: Nutritional regulation of gut function in dairy calves: From colostrum to weaning

Purpose

Published literature regarding calf nutrition was reviewed to create an information base for the implementation of proper nutritional management to maximize health and productivity.

Sources

The main source of data and information for this review was peer-reviewed literature.

Synthesis

Feeding a sufficient volume of colostrum during the first hours of life is crucial to calf health and survival; however, less is known about transition milk feeding and the potential benefits of the myriad of bioactive compounds it contains. After feeding colostrum and transition milk, calves are susceptible to diarrhea when moved onto high amounts of milk, and antibiotic use is often necessary to decrease disease. Feeding an elevated plane of milk nutrition results in increased ADG and, in some studies, increased future milk production. Thus, this nutritional strategy is recommended; however, weaning calves from high volumes of milk represents massive changes in the structure and microbiology of the gastrointestinal tract.

Conclusions and Applications

Colostrum and transition milk contain an abundance of bioactive molecules that can positively affect gut development and microbiota. There is significant potential for the use of novel feeding strategies and microbial-based products as alternatives to antibiotics. Calves fed an elevated plane of nutrition in the first month of life have greater productivity and growth. However, weaning should take place later in life. Moreover, applying a proper step-down feeding protocol is recommended, as it allows calves to intake and digest sufficient solid feed for growth and minimize distress at weaning.

Effects of Mannan Oligosaccharides on Gas Emission, Protein and Energy Utilization, and Fasting Metabolism in Sheep

Simple Summary

Mannan oligosaccharides (MOS) are a promising feed additive to improve animal health, immune capacity, and antioxidation. Based on the previous studies, we carried out three experiments to investigate the effects of MOS on the gas emission, protein and energy utilization, and fasting metabolism of sheep. The results showed that 2.0% MOS supplementation led to the lowest in vitro CO₂ production and lower CH₄ production and decreased in vivo intake. However, it also decreased urine nitrogen excretion and energy released as CH₄, and then improved the utilization of crude protein and energy of sheep. There were no differences in the parameters of respiration and energy metabolism of sheep under the fasting condition. The findings indicated that MOS slightly affected the gas emission and nutrients and energy utilization of sheep.

Abstract

This study investigated the effects of mannan oligosaccharides (MOS) on in vitro and in vivo gas emission, utilization of crude protein (CP) and energy, and relative parameters of sheep under fasting metabolism conditions. In vitro gas productions were evaluated over 12 h in sheep diets containing different amounts of MOS (from 0% to 6.0%/kg, the increment was 0.5%). A control experiment was used to assess the gas emission, utilization of CP and energy, and fasting metabolism in control sheep and sheep treated with 2.0% MOS over 24 days (d). The results showed that 2.0% MOS supplementation led to the lowest in vitro CO₂ production and less CH₄ production, while also leading to decrease in vivo nutrients intake, CP and energy excretion, digested and retained CP, and energy released as CH₄ (p < 0.05). Furthermore, 2.0% MOS supplementation appeared to decrease in vivo O₂ consumption and CH₄ production per metabolic body weight (BW^0.75), and increase the CP retention rate of sheep (p < 0.074). MOS did not affect other parameters, along with the same parameters of sheep under fasting metabolism conditions (p > 0.05). The findings indicate MOS has only slight effects on the gas emission and nutrients and energy metabolism of sheep.

Evaluation of some blood liver parameters in cows with subclinical and clinical ketosis

The purpose of the present study was to establish the changes in some blood liver parameters in cows in different physiological conditions with subclinical (SCK) and clinical ketosis (CK). The study was performed on 157 Holstein cows with annual milk yield of 9,000–11,000 L. The animals were divided into 3 groups: I group – pregnant cows (from day 15 to day 0 pre-calving); II group – recently calved (from day 0 to day 15 postpartum) and III group – lactating (from day 30 to 45 postpartum). Blood concentrations of β-hydroxybutyric acid (ВНВА) (mmol/L), glucose (mmol/L), total protein (g/L), albumin (g/L) and total bilirubin (μmol/L) were assayed in all cows. The animals were divided in groups with SCK and CK according to their blood BHBA levels. It was established, that the con-centrations of total bilirubin were statistically significantly elevated vs control groups, while blood glucose, total protein and albumin values decreased, reflecting the impaired liver function in cows with SCK and CK.

Short-Chain Fatty Acids Regulate the Immune Responses via G Protein-Coupled Receptor 41 in Bovine Rumen Epithelial Cells

The rumen immune system often suffers when challenging antigens from lysis of dead microbiota cells in the rumen. However, the rumen epithelium innate immune system can actively respond to the infection. Previous studies have demonstrated G protein-coupled receptors 41 (GPR41) as receptors for short chain fatty acids (SCFAs) in human. We hypothesized that SCFAs, the most abundant microbial metabolites in rumen, may regulate the immune responses by GPR41 in bovine rumen epithelial cells (BRECs). Therefore, the objective of study was to firstly establish an immortal BRECs line and investigate the regulatory effects of SCFAs and GPR41 on innate immunity responses in BRECs. These results showed that long-term BRECs cultures were established by SV40T-induced immortalization. The concentrations of 20 mM SCFAs significantly enhanced the levels of GPR41, IL1β, TNFα, chemokines, and immune barrier genes by transcriptome analysis. Consistent with transcriptome results, the expression of GPR41, IL1β, TNFα, and chemokines were markedly upregulated in BRECs treated with 20 mM SCFAs by qRT-PCR compared with control BRECs. Remarkably, the GPR41 knockdown (GPR41KD) BRECs treated with 20 mM SCFAs significantly enhanced the proinflammatory cytokines IL1β and TNFα expression compared with wild type BRECs treated with 20 mM SCFAs, but reduced the expression of CCL20, CXCL2, CXCL3, CXCL5, CXCL8, CXCL14, Occludin, and ZO-1. Moreover, GPR41 mRNA expression is positively correlated with CCL20, CXCL2, CXCL3, CXCL8, CXCL14, and ZO-1. These findings revealed that SCFAs regulate GPR41-mediated levels of genes involved in immune cell recruitment and epithelial immune barrier and thereby mediate protective innate immunity in BRECs.

Effects of Dietary-SCFA on Microbial Protein Synthesis and Urinal Urea-N Excretion Are Related to Microbiota Diversity in Rumen

Two experiments were performed in this study. In Experiment 1, twenty goats were fed with an isonitrogenous diet, containing 28% Non-Fiber Carbohydrate (MNFC group, n = 10) or 14% NFC (LNFC group, n = 10). In the MNFC group, the ruminal concentration of Short Chain Fatty Acids (SCFA) increased, and pH declined. Compared with those in the LNFC group, the microbial protein synthesis in rumen and mRNA abundance of urea transporter B (UT-B) in rumen epithelium increased in the MNFC group, although serum urea-N (SUN) did not differ significantly between groups. Simultaneously, urinal urea-N excretion was reduced in the MNFC group. Significant correlations were found between rumen SCFA and UT-B and between UT-B and urinal urea-N excretion. Furthermore, the abundances of SCFA receptor of GPR41 and GPR43 increased in the rumen epithelium of the MNFC group. These results suggest that increases of SUN transported into the rumen and incorporated into microbial protein and decreases of urinal urea-N excretion are related to ruminal SCFA. This is supported by data from our previous study in which added SCFA on the mucosal side caused increases of urea transport rate (flux J_sm urea) from the blood to the ruminal lumen side. In Experiment 2, we used 16S rRNA Amplicon Sequencing to analyze the structure of the ruminal microbiota community in relation to SCFA. An additional eight goats were assigned into the MNFC (n = 4) and LNFC (n = 4) groups. The dietary ingredients, chemical composition, and feeding regimes were the same as those in Experiment 1. Constrained correspondence analysis (CCA analysis) revealed NFC promoted the expansion of microbiota diversity, particularly of SCFA-producing microbes. The function prediction of 19 upregulated Kyoto Encyclopedia of Genes and Genomes (KEGG) ortholog groups showed an NFC-induced increase of the types and abundances of genes coding for enzymes catalyzing N and fatty acid metabolism. Based on our present and previous investigations, our results indicate that, in goats consuming a MNFC diet, the facilitated urea transport in the rumen and improved urea N salvage are triggered by an expansion of ruminal microbiota diversity and are signaled by ruminal SCFA. This study thus provides new insights into the microbiota involved in the dietary modulation of urea-N salvage in ruminant animals.

Effects of supplemental butyrate and weaning on rumen fermentation in Holstein calves

The objectives of this study were to determine the effects of the weaning transition and supplemental rumen-protected butyrate on subacute ruminal acidosis, feed intake, and growth parameters. Holstein bull calves (n = 36; age = 10.7 ± 4.1 d; ± standard deviation) were assigned to 1 of 4 treatment groups: 2 preweaning groups, animals fed milk replacer only (PRE-M) and those fed milk replacer, calf starter, and hay (PRE-S); and 2 postweaning groups, animals fed milk replacer, calf starter, and hay without supplemental rumen-protected butyrate (POST-S) or with supplemental rumen-protected butyrate at a rate of 1% wt/wt during the 2-wk weaning transition (POST-B). Milk replacer was provided at 1,200 g/d; starter, water, and hay were provided ad libitum. Weaning took place over 14 d by reducing milk replacer provision to 900 g/d in wk 7, 600 g/d in wk 8, and 0 g/d in wk 9. Rumen pH was measured continuously for 7 d during wk 6 for PRE-S and PRE-M and during wk 9 for POST-S and POST-B. After rumen pH was measured for 7 d, calves were euthanized, and rumen fluid was sampled and analyzed for volatile fatty acid (VFA) profile. Individual feed intake was recorded daily, whereas, weekly, body weights were recorded, and blood samples were collected. Compared with PRE-M, PRE-S calves tended to have a greater total VFA concentration (35.60 ± 11.4 vs. 11.90 ± 11.8 mM) but mean rumen pH was unaffected (6.25 ± 0.22 vs. 6.17 ± 0.21, respectively). Between PRE-S (wk 6) and POST-S (wk 9), calf starter intake increased (250 ± 219 vs. 2,239 ± 219 g/d), total VFA concentrations increased (35.6 ± 11.4 vs. 154.4 ± 11.8 mM), but mean rumen pH was unaffected (6.25 ± 0.22 vs. 6.40 ± 0.22, respectively). Compared with POST-S, POST-B calves had greater starter intake in wk 7, 8, and 9, but POST-B tended to have lower total VFA concentration (131.0 ± 11.8 vs. 154.4 ± 11.8 mM) and lower mean ruminal pH (5.83 ± 0.21 vs. 6.40 ± 0.22). In conclusion, the weaning transition does not appear to affect rumen pH and VFA profile, but supplementing rumen-protected butyrate during the weaning transition increased starter intake and average daily gain. Further, these data suggest that the ability of the rumen to manage rumen pH changes fundamentally postweaning. Why weaned calves with lower rumen pH can achieve higher calf starter intakes is unclear; these data suggest the effect of rumen pH on feed intake differs between calves and cows.

Comparing the Microbial Community in Four Stomach of Dairy Cattle, Yellow Cattle and Three Yak Herds in Qinghai-Tibetan Plateau

Yak (Bos grunniens) is an unique ruminant species in the Qinghai-Tibetan Plateau (QTP). The ruminant gastrointestinal tract (GIT) microbiota is not only associated with the nutrients metabolism, but also contributes to the host’s local adaptation. Examining the microbiota between cattle and yak in different geography could improve our understanding about the role of microbiota in metabolism and adaptation. To this end, we compared the microbiota in rumen, reticulum, omasum, and abomasum of dairy cattle, yellow cattle, and three yak herds (WQ yak, SZ yak, and ZB yak) lived in different altitude, based on sequencing the bacterial 16S rRNA gene on Illumina Miseq. The bacterial diversity was significantly different among five breeds, whereas the difference among four stomach regions is limited. The phyla Bacteroidetes and Firmicutes were the dominated bacteria regardless of breeds and regions. The nonmetric multidimensional scaling (NMDS) results showed that the microbiota in dairy cattle, yellow cattle and WQ yak significantly differed from that in SZ yak and ZB yak for all four stomach compartments. Canonical correlation analysis revealed that Prevotella and Succiniclasticum spp. were abundant in dairy cattle, yellow cattle and WQ yak, whereas the Christensenellaceae R7 group and the Lachnospiraceae UCG 008 group were prevalent in SZ yak and ZB yak. Moreover, the microbiota in WQ yak was significantly different from that in SZ yak and ZB yak, which were characterized by the higher relative abundance Romboutsia spp., Eubacterium coprostanoligenes, Acetobacter spp., Mycoplasma spp., and Rikenellaceae RC9 group. Overall, these results improves our knowledge about the GIT microbiota composition of QTP ruminant.

Unveiling the relationships between diet composition and fermentation parameters response in dual-flow continuous culture system: a meta-analytical approach

The objective of this study was to investigate the functional form of the relationship between diet composition (dietary crude protein [CP] and neutral detergent fiber [NDF]) and amount of substrate (fermenter dry matter intake [DMI]) with microbial fermentation end products in a dual-flow continuous culture system. A meta-analysis was performed using data from 75 studies. To derive the linear models, the MIXED procedure was used, and for nonlinear models, the NLMIXED procedure was used. Significance levels to fit the model assumed for fixed and random effects were P ≤ 0.05. Independent variables were dietary NDF, CP, and fermenter DMI, whereas dependent variables were total volatile fatty acids (VFA) concentration; molar proportions of acetate, propionate, and butyrate; true ruminal digestibilities of organic matter (OM), CP, and NDF; ammonia nitrogen (NH₃-N) concentration and flows of NH₃-N; non-ammonia nitrogen; bacterial-N; dietary-N; and efficiency of microbial protein synthesis (EMPS). Ruminal digestibilities of OM, NDF, and CP decreased as fermenter DMI increased (P < 0.04). Dietary NDF and CP digestibilities were quadratically associated (P < 0.01). Total VFA linearly increased as DMI increased (P < 0.01), exponentially decreased as dietary NDF increased (P < 0.01), and was quadratically associated with dietary CP (P < 0.01), in which total VFA concentration was maximized at 18% dietary CP. Molar proportion of acetate exponentially increased (P < 0.01) as dietary NDF increased. Molar proportion of propionate linearly increased and exponentially decreased as DMI and dietary NDF increased, respectively (P < 0.01). Bacterial-N quadratically increased and dietary-N exponentially increased as DMI increased (P < 0.01). Flows of bacterial-N and dietary-N linearly decreased as dietary NDF increased (P < 0.02), and dietary-N flow was maximized at 18% CP. The EMPS linearly increased as dietary CP increased (P < 0.02) and was not affected by DMI or dietary NDF (P > 0.05). In summary, increasing fermenter DMI increased total VFA concentration and molar proportion of propionate, whereas, dietary NDF increased the molar proportion of acetate. Dietary CP increased bacterial-N flow and was positively associated with NH₃-N concentration. Overall, the analysis of this dataset demonstrates evidences that the dual-flow continuous culture system provides valuable estimates of ruminal digestibility, VFA concentration, and nitrogen metabolism.

Host genetics influence the rumen microbiota and heritable rumen microbial features associate with feed efficiency in cattle

BACKGROUND

The symbiotic rumen microbiota is essential for the digestion of plant fibers and contributes to the variation of production and health traits in ruminants. However, to date, the heritability of rumen microbial features and host genetic components associated with the rumen microbiota, as well as whether such genetic components are animal performance relevant, are largely unknown.

RESULTS

In the present study, we assessed rumen microbiota from a cohort of 709 beef cattle and showed that multiple factors including breed, sex, and diet drove the variation of rumen microbiota among animals. The diversity indices, the relative abundance of ~ 34% of microbial taxa (59 out of 174), and the copy number of total bacteria had a heritability estimate (h²) ≥ 0.15, suggesting that they are heritable elements affected by host additive genetics. These moderately heritable rumen microbial features were also found to be associated with host feed efficiency traits and rumen metabolic measures (volatile fatty acids). Moreover, 19 single nucleotide polymorphisms (SNPs) located on 12 bovine chromosomes were found to be associated with 14 (12 of them had h² ≥ 0.15) rumen microbial taxa, and five of these SNPs were known quantitative trait loci for feed efficiency in cattle.

CONCLUSIONS

These findings suggest that some rumen microbial features are heritable and could be influenced by host genetics, highlighting a potential to manipulate and obtain a desirable and efficient rumen microbiota using genetic selection and breeding. It could be a useful strategy to further improve feed efficiency and optimize rumen fermentation through targeting both cattle and their rumen microbiota.

Ruminal microbiome-host crosstalk stimulates the development of the ruminal epithelium in a lamb model

BACKGROUND

The development of the rumen is an important physiological challenge for young ruminants. Previous studies have shown that starter feeding can effectively facilitate the growth and development of the rumen in ruminants. However, the mechanism through which starter feeding stimulates the development of the rumen is not clear. Here, we performed an integrated analysis in ruminal microbiota and a host transcriptomic profile in a lamb model with the intervention of starter feed to understand the ruminal microbiome-host crosstalk in stimulating the development of the ruminal epithelium.

RESULTS

Decreased ruminal pH and increased acetate and butyrate concentrations in the rumen, followed by increasing rumen organ index, were observed in lambs supplemented with starter. Using metagenome sequencing in combination with 16S rRNA and 18S rRNA gene amplicon sequencing, the results showed the abundance of acetate-producing Mitsuokella spp., lactate-producing Sharpea spp., lactate-utilizing Megasphaera spp., and Entodinium spp. was enriched in rumen microbial communities in the starter-feed group. The abundances of genes involved in sugar degradation were decreased in starter-feed lambs, but the GH13 encoding α-amylase was obviously increased. Rumen epithelial transcriptome analysis revealed that seven differentially expressed genes, including MAPK1, PIK3CB, TNFSF10, ITGA6, SNAI2, SAV1, and DLG, related to the cell growth module were upregulated, and BAD's promotion of cell death was downregulated. Correlation analysis revealed that the increase in the concentrations of acetate and butyrate significantly correlated with the expression of these genes, which indicates acetate and butyrate likely acted as important drivers in the ruminal microbiome-host crosstalk.

CONCLUSIONS

The present study comprehensively describes the symbiotic relationship between the rumen microbiota and the host in lambs after starter feeding. Our data demonstrates that the microbiome-driven generation of acetate and butyrate mediated the growth-related genes' regulation of the growth-associated signalling pathway in the ruminal epithelium. These co-development networks regulated many physiological processes in the epithelium, including papillae morphology and rumen epithelial growth.

Effects of clay mineral supplementation on particle-associated and epimural microbiota, and gene expression in the rumen of cows fed high-concentrate diet

The increased concentrate amounts in cow diets may initiate changes in both particle-associated (PaM) and epimural microbiota (EpM) with the potential for promoting the establishment of pathogens. Clay minerals have shown promising potentials in binding harmful microorganisms and metabolites due to their high adsorption capacity. This study evaluated the effects of a clay-mineral based product (CM) on PaM, EpM, fermentation parameters, and epithelial gene expression in cows fed a high-concentrate diet. Eight rumen-cannulated non-lactating Holstein cows received a concentrate mix supplemented with CM or not (CON) in a change-over design with an initial 100% roughage diet phase (RD, 1 week), followed by intermittent 65%-high-concentrate-diet phases (HC1, HC2; 1 and 2 week duration, respectively), interrupted by 1 week roughage only. Rumen samples for short-chain fatty acids, ammonia, and lactate quantification, as well as PaM, and epithelial biopsies for EpM examination and epithelial gene expression were collected via the cannula once during each feeding phase. Phylogenetic distance analysis of Illumina MiSeq sequencing of the 16S rRNA gene region V345 showed a clear clustering of RD microbiota compared to HC in PaM, showing the impact of the high-concentrate diet on the bacterial community. In the EpM this effect was less pronounced, due to higher variability in RD. In the PaM, a decrease (P < 0.01) of community diversity occurred with the onset of HC feeding, while in the EpM there was an increase in diversity (P < 0.05). In the PaM, CM increased the relative abundance of genus Butyrivibrio (P < 0.01), a commensal bacterium of the rumen, which was, with 6.4%, the second most abundant genus. There, the CM supplementation decreased the genera Lactobacillus, Fusobacterium, and Treponema (P = 0.05), which are potentially either lactate producing or opportunistic pathogens. In the EpM, CM decreased the relative abundance of Succiniclasticum genus (P < 0.01), a possible endotoxin producer, and increased bacteria that are associated with a normobiotic rumen, such as Campylobacter (P = 0.06). Barrier function genes were upregulated in HC2 and nutrient transport genes downregulated in HC1 (P < 0.05); however, there was little effect on pro-inflammatory genes at the epithelium. The CM showed a significant decreasing effect on the cellular metabolism genes HMGCS1 (P = 0.04). Our results suggest that CM supplementation can increase the relative abundance of commensal microbiota and decrease bacteria that could negatively impact the rumen milieu and health during high-concentrate feeding.

Days-in-Milk and Parity Affected Serum Biochemical Parameters and Hormone Profiles in Mid-Lactation Holstein Cows

It is well known that serum biochemical parameters and hormones contribute greatly to the physiological and metabolic status of dairy cows. However, few studies have focused on the variation of these serum parameters in multiparous mid-lactation cows without the interference of diet and management. A total of 287 Holstein dairy cows fed the same diet and maintained under the same management regime were selected from a commercial dairy farm to evaluate the effects of days-in-milk (DIM) and parity on serum biochemical parameters and hormone profiles. Milk yield and milk protein content were affected by DIM and parity (p < 0.05). Milk protein yield showed a numerically decreasing trend with parity, and it was relatively constant in cows with parities between 2 and 4 but lower in cows with parity 6 (p = 0.020). Ten and five serum biochemical parameters related to protein status, energy metabolism, liver and kidney function, and oxidative stress were affected by DIM and parity, respectively (p < 0.05). Glucagon, insulin-like growth factor 1 concentration, and the revised quantitative insulin sensitivity check index were significantly different (p < 0.05) among cows with different DIM. Parity had no effect on hormone concentrations. An interaction between DIM and parity effect was only detected for glucagon concentration (p = 0.015), which showed a significantly increasing trend with DIM and overall decreasing trend with parity. In summary, DIM and parity played an important role in affecting the serum biochemical parameters and/or hormones of dairy cows, with serum parameters affected more by DIM than parity.

Effect of dietary energy on digestibilities, rumen fermentation, urinary purine derivatives and serum metabolites in Tibetan and small-tailed Han sheep

Tibetan sheep are indigenous to the Qinghai-Tibetan Plateau, graze the grassland all year round without supplementation and are well-adapted to the harsh conditions. Small-tailed Han sheep were introduced to the plateau and are raised mainly in feedlots. Based on their different backgrounds, we hypothesized that the ability to cope with poor diets would be better in Tibetan than in Han sheep. To test our prediction, we examined the effect of dietary energy on apparent digestibilities, rumen fermentation, urinary purine derivatives and serum metabolites by using a 4 × 4 Latin square design in each sheep breed. Four diets were formulated to be low in crude protein (~7%) but to differ in metabolizable energy concentration. Average daily gain was greater in Tibetan than in Han sheep (p < 0.01) and increased linearly with an increase in energy intake (p < 0.001). The digestibilities of dry matter, organic matter, gross energy, and neutral and acid detergent fibres were greater in Tibetan than in Han sheep (p < 0.05). Ruminal pH was lower (p < 0.05), while volatile fatty acids (VFAs), urea-N, ammonia-N and soluble protein-N concentrations were higher (p < 0.05) in Tibetan than in Han sheep. As a molar proportion of total VFA, acetate decreased (p < 0.001) with an increase in dietary energy whereas propionate and butyrate increased (p < 0.05). Urinary purine derivative excretion was greater in Tibetan than in Han sheep (p < 0.01), as was microbial nitrogen production; both parameters increased with dietary energy (p < 0.01). Serum concentrations of glucose, insulin and insulin-like growth factor-1 increased (p < 0.05) as energy level increased, while non-esterified fatty acids and growth hormone decreased (p < 0.05). It was concluded that Tibetan sheep were better able to cope with low-protein, low-energy diets and, consequently, our prediction was supported.

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.

Graded replacement of corn grain with molassed sugar beet pulp modulates the fecal microbial community and hindgut fermentation profile in lactating dairy cows

High starch lactation diets not only enhance the risk of subacute ruminal acidosis but also of hindgut acidosis, which increases the risk of dysbiosis and the depression of fiber degradation. We recently showed that replacing corn with molassed sugar beet pulp (Bp) improved fiber degradation in high-producing dairy cattle, possibly because of an improvement of rumen and hindgut conditions for microbes by Bp feeding. However, little is known about the effects of high inclusion rates of Bp on hindgut microbes and fermentation. Thus fecal grab samples were taken from 18 high-yielding Simmental cows after 28 d of feeding 3 different levels of Bp (n = 6) for bacterial 16S rRNA amplicon sequencing. In addition, the reticular pH was continuously monitored with indwelling sensors and eating and ruminating behavior was evaluated with noseband sensors. The Bp inclusion rates were 0 g/kg (i.e., no Bp inclusion as control, CON), 120 g/kg (12Bp), or 240 g/kg (24Bp) replacing corn grain and limestone on a dry matter basis. The amount of time spent eating and ruminating was unaffected by Bp level, and the daily fluctuation in the reticular pH was reduced by 25% with Bp inclusion from 0.8 in the CON diet to 0.6 in 24Bp fed animals. Also, the fecal pH tended to increase with dietary Bp inclusion. Fecal acetate production showed a quadratic tendency with the lowest concentration (58.9%) of the total short-chain fatty acid in the 12Bp treatment. Inclusion of Bp up to 24% of the diet decreased the fecal butyrate proportion by 27%. The Shannon diversity index was increased from 5.50 to 8.09 with dietary Bp inclusion indicating increased species diversity. Of the 200 most abundant operational taxonomic units, 25 were increased by dietary Bp inclusion, whereas 15 were decreased and 7 were quadratically affected. The second most abundant group was proposed taxon "CF231" of the family Paraprevotellaceae. Although it accounted for only 2.52% of the operational taxonomic units in the CON diet, it was increased by 64% with dietary Bp inclusion. The largest relative change in the abundance was found for the genus Fibrobacter that increased more than 14-fold from 0.04% (CON) to 0.66% (24Bp). In conclusion, feeding molassed sugar beet pulp as partial substitution of corn up to 240 g/kg is a viable alternative that promotes ruminal and hindgut fermentation by supporting physiological pH and bacterial diversity.

Transcriptome analysis of rumen epithelium and meta-transcriptome analysis of rumen epimural microbial community in young calves with feed induced acidosis

Many common management practices used to raise dairy calves while on milk and during weaning can cause rumen acidosis. Ruminal pH has long been used to identify ruminal acidosis. However, few attempts were undertaken to understand the role of prolonged ruminal acidosis on rumen microbial community or host health in young calves long after weaning. Thus, the molecular changes associated with prolonged rumen acidosis in post weaning young calves are largely unknown. In this study, we induced ruminal acidosis by feeding a highly processed, starch-rich diet to calves starting from one week of age through 16 weeks. Rumen epithelial tissues were collected at necropsy at 17 weeks of age. Transcriptome analyses on the rumen epithelium and meta-transcriptome analysis of rumen epimural microbial communities were carried out. Calves with induced ruminal acidosis showed significantly less weight gain over the course of the experiment, in addition to substantially lower ruminal pH in comparison to the control group. For rumen epithelial transcriptome, a total of 672 genes (fold-change, FC ≥ 1.5; adjusted-p ≤ 0.05) showed significant differential expression in comparison to control. Biological pathways impacted by these differentially expressed genes included cell signaling and morphogenesis, indicating the impact of ruminal acidosis on rumen epithelium development. rRNA read-based microbial classification indicated significant increase in abundance of several genera in calves with induced acidosis. Our study provides insight into host rumen transcriptome changes associated with prolonged acidosis in post weaning calves. Shifts in microbial species abundance are promising for microbial species-based biomarker development and artificial manipulation. Such knowledge provides a foundation for future more precise diagnosis and preventative management of rumen acidosis in dairy calves.

Nutritional Interventions Improved Rumen Functions and Promoted Compensatory Growth of Growth-Retarded Yaks as Revealed by Integrated Transcripts and Microbiome Analyses

Growth retardation reduces the incomes of livestock farming. However, effective nutritional interventions to promote compensatory growth and the mechanisms involving digestive tract microbiomes and transcripts have yet to be elucidated. In this study, Qinghai plateau yaks, which frequently suffer from growth retardation due to malnutrition, were used as an experimental model. Young growth-retarded yaks were pastured (GRP), fed basal ration (GRB), fed basal ration addition cysteamine hydrochloride (CSH; GRBC) or active dry yeast (ADY; GRBY). Another group of growth normal yak was pastured as a positive control (GNP). After 60-day nutritional interventions, the results showed that the average daily gain (ADG) of GRB was similar to the level of GNP, and the growth rates of GRBC and GRBY were significantly higher than the level of GNP (P < 0.05). Basal rations addition of CSH or ADY either improved the serum biochemical indexes, decreased serum LPS concentration, facilitated ruminal epithelium development and volatile fatty acids (VFA) fermentation of growth-retarded yaks. Comparative transcriptome in rumen epithelium between growth-retarded and normal yaks identified the differentially expressed genes mainly enriched in immune system, digestive system, extracellular matrix and cell adhesion pathways. CSH addition and ADY addition in basal rations upregulated ruminal VFA absorption (SLC26A3, PAT1, MCT1) and cell junction (CLDN1, CDH1, OCLN) gene expression, and downregulated complement system (C2, C7) gene expression in the growth-retarded yaks. 16S rDNA results showed that CSH addition and ADY addition in basal rations increased the rumen beneficial bacterial populations (Prevotella_1, Butyrivibrio_2, Fibrobacter) of growth-retarded yaks. The correlation analysis identified that ruminal VFAs and beneficial bacteria abundance were significantly positively correlated with cell junction and VFA absorption gene expressions and negatively correlated with complement system gene expressions on the ruminal epithelium. Therefore, CSH addition and ADY addition in basal rations promoted rumen health and body growth of growth-retarded yaks, of which basal ration addition of ADY had the optimal growth-promoting effects. These results suggested that improving nutrition and probiotics addition is a more effective method to improve growth retardation caused by gastrointestinal function deficiencies.

Propionate and butyrate induce gene expression of monocarboxylate transporter 4 and cluster of differentiation 147 in cultured rumen epithelial cells derived from preweaning dairy calves

Short-chain fatty acids (SCFAs) are the main source of energy for postweaning ruminants. The monocarboxylic acid transporters, MCT1 and MCT4, are thought to contribute to the absorption of SCFAs from the surface of the rumen following weaning. The present study measured changes in MCT1 and MCT4 expression in ruminal epithelial cells isolated from male preweaning (22 to 34 d old, n = 6) and postweaning (55 to 58 d old, n = 8) calves after euthanasia and sought to examine whether SCFAs stimulate the expression of these transporters. In the current study, cluster of differentiation 147 (CD147) gene expression in the rumen was also investigated since CD147 has been considered to act as ancillary protein for MCT1 and MCT4 to express their correct function. The gene expression levels of MCT1, MCT4, and CD147 in the rumen were found to be significantly higher in postweaning calves than in preweaning calves. Strong MCT1 immunoreactivity was detected in both the stratum basale (SB) and the stratum spinosum (SS) in postweaning ruminal epithelium. Expression of MCT1 in preweaning calves was localized to a specific region of the SB and of the SS. MCT4-immunopositive cells were detected in the stratum corneum (SC) of the ruminal epithelium in postweaning calves. However, only a low level of signal was detected in the SC of preweaning animals. Furthermore, in vitro experiments, ruminal epithelial cells were incubated for 24 h with acetate (0.04, 0.4, and 4 mM), propionate (0.2, 2, and 20 mM), butyrate (0.1, 1, and 10 mM), or β-hydroxybutyrate (BHBA; 0.1, 1, and 10 mM), respectively. Both propionate and butyrate induced an increase in the gene expression levels of MCT4 and CD147, but did not affect MCT1 gene expression. There are no significant effects of acetate and BHBA treatment on these gene expressions. Taken together, these results suggest that an increase in MCT4 and CD147 gene expression in the ruminal epithelium of postweaning calves is likely to be due to the effects of propionate and butyrate derived from a solid-based diet, which may contribute to ruminal development following weaning.

Effects and immune responses of probiotic treatment in ruminants

Gut microbial colonization and establishment are vital to ruminant health and production. This review article focuses on current knowledge and methods used to understand and manipulate the gut microbial community in ruminant animals, with a special focus on probiotics treatment. This review highlights the most promising of studies in this area, including gut microbial colonization and establishment, effect of gastrointestinal tract microbial community on host mucosal innate immune function, impact of feeding strategies on gut microbial community, current probiotic treatments in ruminants, methods to manipulate the gut microbiota and associated antimicrobial compounds, and models and cell lines used in understanding the host immune response to probiotic treatments. As a lot of work in this area was done in humans and mice, this review article also includes up-to-date knowledge from relevant studies in human and mouse models. This review is a useful resource for scientists working in the areas of ruminant nutrition and health, and to researchers investigating the microbial ecology and its relation to animal health.

Postpartum supplementation of fermented ammoniated condensed whey improved feed efficiency and plasma metabolite profile

Postpartum dietary supplementation of gluconeogenic precursors may improve the plasma metabolite profile of dairy cows, reducing metabolic disorders and improving lactation performance. The objective of this trial was to examine the effects of supplementation with fermented ammoniated condensed whey (FACW) postpartum on lactation performance and on profile of plasma metabolites and hormones in transition dairy cows. Individually fed multiparous Holstein cows were blocked by calving date and randomly assigned to control (2.9% dry matter of diet as soybean meal; n = 20) or FACW (2.9% dry matter of diet as liquid GlucoBoost, Fermented Nutrition, Luxemburg, WI; n = 19) dietary treatments. Treatments were offered from 1 to 45 d in milk (DIM). Cows were milked twice a day. Dry matter intake and milk yield were recorded daily and averaged weekly. Individual milk samples from 2 consecutive milkings were obtained once a week for component analysis. Rumen fluid was collected (n = 3 cows/treatment) at 4 time points per day at 7 and 21 DIM. Blood samples were collected within 1 h before feeding time for metabolite analysis and hyperketonemia diagnosis. Supplementation of FACW improved feed efficiency relative to control; this effect may be partially explained by a marginally significant reduction in dry matter intake from wk 3 to 7 for FACW-supplemented cows with no detected FACW-driven changes in milk yield, milk protein yield, and milk energy output compared with control. Also, there was no evidence for differences in intake of net energy for lactation, efficiency of energy use, energy balance, or body weight or body condition score change from calving to 45 DIM between treatments. Supplementation of FACW shifted rumen measures toward greater molar proportions of propionate and butyrate, and lesser molar proportions of acetate and valerate. Cows supplemented with FACW had greater plasma glucose concentrations in the period from 3 to 7 DIM and greater plasma insulin concentrations compared with control. Plasma nonesterified fatty acid and β-hydroxybutyrate concentrations were decreased in cows supplemented with FACW compared with control cows in the period from 3 to 7 DIM. These findings indicate that FACW may have improved the plasma metabolite profile immediately postpartum in dairy cows. Additionally, supplementation of FACW resulted in improved feed efficiency as accessed by measures of milk output relative to feed intake.

Monensin Alters the Functional and Metabolomic Profile of Rumen Microbiota in Beef Cattle

Simple Summary

Monensin can enhance the efficiency of feed utilization by modulating rumen fermentation; however, its effects on rumen function has not been fully described. Thus, this study integrated metagenomics and metabolomics analysis to identify differences in functional attributes and metabolites of rumen microbiota in beef steers fed no or 200 mg/d of monensin. Our results showed differences in relative abundance of functional genes involved in lipid metabolism and amino acid metabolism as well as changes in rumen fluid metabolites and their metabolic pathways. This study revealed a better understanding of the effects of monensin, which may enable more effective use of this additive for beef cattle production.

Abstract

To identify differences in rumen function as a result of feeding monensin to beef cattle, rumen fluid metagenomics and metabolomics analyses were used to evaluate the functional attributes and metabolites of rumen microbiota in beef steers fed no or 200 mg/d of monensin. Eight rumen-fistulated steers were used in the study for a period of 53 days. Rumen fluid samples were collected on the last day of the experiment. Monensin increased the relative abundance of Selenomonas sp. ND2010, Prevotella dentalis, Hallella seregens, Parabacteroides distasonis, Propionispira raffinosivorans, and Prevotella brevis, but reduced the relative abundance of Robinsoniella sp. KNHs210, Butyrivibrio proteoclasticus, Clostridium botulinum, Clostridium symbiosum, Burkholderia sp. LMG29324, and Clostridium butyricum. Monensin increased the relative abundance of functional genes involved in amino acid metabolism and lipid metabolism. A total of 245 metabolites were identified. Thirty-one metabolites were found to be differentially expressed. Pathway analysis of the differentially expressed metabolites revealed upregulated metabolic pathways associated with metabolism of linoleic acid and some amino acids. These findings confirm that monensin affects rumen fermentation of forage-fed beef cattle by modulating the rumen microbiome, and by reducing amino acid degradation and biohydrogenation of linoleic acid in the rumen.

Evaluation of reticuloruminal pH measurements from individual cattle: Sampling strategies for the assessment of herd status

The application of pH observations to clinical practice in dairy cattle is based on criteria derived primarily from single time-point observations more than 20 years ago. The aims of this study were to evaluate these criteria using data collected using continuous recording methods; to make recommendations that might improve their interpretation; and to determine the relationship between the number of devices deployed in a herd and the accuracy of the resulting estimate of the herd-mean reticuloruminal pH. The study made use of 815,475 observations of reticuloruminal pH values obtained from 75 cattle in three herds (one beef and two twice-daily milking herds) to assess sampling strategies for the diagnosis of sub-acute rumen acidosis (SARA), and to evaluate the ability of different numbers of bolus devices to accurately estimate the true herd-mean reticuloruminal pH value at any time. The traditional criteria for SARA provide low diagnostic utility, the probability of detection of animals with pH values below specified thresholds being affected by a strong effect of time of day and herd. The analysis suggests that regardless of time of feeding, sampling should be carried out in the late afternoon or evening to obtain a reasonable probability of detection of animals with pH values below the threshold level. The among-cow variation varied strongly between herds, but for a typical herd, if using reticuloruminal pH boluses to detect a predisposition to fermentation disorders while feeding a diet that is high in rapidly fermentable carbohydrates, it is recommended to use a minimum of nine boluses.

Dietary Addition of Sodium Butyrate Contributes to Attenuated Feeding-Induced Hepatocyte Apoptosis in Dairy Goats

The present study aims to reveal the mechanisms of hepatocyte apoptosis induced by dietary feeding. Eighteen midlactating goats were randomly divided into three groups: the low concentrate group (LC), the high concentrate group (HC), and the sodium butyrate (SB)-supplemented group (SHC). After 10 weeks, the HC diet successfully induced subacute ruminal acidosis (SARA), which increased the lipopolysaccharide (LPS) and cytokine concentrations and the expression of genes and proteins related to inflammation and apoptosis. The addition of SB to the HC diet notably decreased the levels of those parameters. Additionally, Bcl2 mRNA and protein expression was lower in the HC group than those in the LC and SHC groups. Furthermore, the HC diet reduced the percentages of caspase 3 and 8 promoter methylation compared to those of goats fed the LC diet, whereas the SHC diet partially recovered the methylation ratio to reduce caspase 3 and 8 expression. Collectively, HC diet-induced SARA caused hepatocyte apoptosis via activating the extrinsic apoptosis pathway, whereas dietary addition of SB depressed the inflammatory response and attenuated hepatocyte apoptosis. DNA methylation contributed to regulation of the expression of key apoptotic genes in the livers of lactating goats.

Method development to reduce the fiber content of wheat bran and rice bran through anaerobic fermentation with rumen liquor for use in poultry feed

Objective

Wheat bran (WB) and rice bran (RB) are the agricultural by-products used as poultry feed in many developing countries. However, their use for poultry feed is limited due to high fiber and the presence of anti-nutritional substances (e.g. β-glucans). The objective of this study was to develop a method to improve the quality of those brans by reducing the fiber content.

Methods

A two-step fermentation method was developed where the second fermentation of first fermented dry bran was carried out. Fermentation was performed at a controlled environment for 3 h and 6 h (n = 6). The composition of brans, buffer solution and rumen liquor was maintained in a ratio of 1:2:3, respectively. Brans were analyzed for dry matter, crude fiber (CF), acid detergent fiber (ADF), neutral detergent fiber (NDF), and acid detergent lignin (ADL) content. Celluloses and hemicelluloses were calculated from the difference of ADF-ADL and NDF-ADF, respectively. Samples were compared by two-factor analysis of variance followed by Tukey’s multiple comparison tests (p<0.05).

Results

CF %, ADF % and cellulose tended to decrease and NDF % and hemicellulose content was reduced significantly (p<0.05). After the 1st fermentation step, NDF decreased 10.7%± 0.55% after 3 h vs 17.0%±0.78% after 6 h in case of WB. Whereas, these values were 2.3%± 0.30% (3 h) and 7.5%±0.69% (6 h) in case of RB. However, after the 2nd fermentation step, the decrease in the NDF content amounted to 9.1%±0.72% (3 h), 17.4%±1.13% (6 h) and 9.3%±0.46% (3 h), 10.0%±0.68% (6 h) in WB and RB, respectively. Cellulose and hemicellulose content was reduced up to 15.6%±0.85% (WB), 15.8%±2.20% (RB) and 36.6%±2.42% (WB), 15.9%±3.53% (RB), respectively after 2nd fermentation of 6 h.

Conclusion

Two-step fermentation process improved the quality of the brans for their use in poultry feed.

Review: Enhancing gastrointestinal health in dairy cows

Due to their high energy requirements, high-yielding dairy cows receive high-grain diets. This commonly jeopardises their gastrointestinal health by causing subacute ruminal acidosis (SARA) and hindgut acidosis. These disorders can disrupt nutrient utilisations, impair the functionalities of gastrointestinal microbiota, and reduce the absorptive and barrier capacities of gastrointestinal epithelia. They can also trigger inflammatory responses. The symptoms of SARA are not only due to a depressed rumen pH. Hence, the diagnosis of this disorder based solely on reticulo-rumen pH values is inaccurate. An accurate diagnosis requires a combination of clinical examinations of cows, including blood, milk, urine and faeces parameters, as well as analyses of herd management and feed quality, including the dietary contents of NDF, starch and physical effective NDF. Grain-induced SARA increases acidity and shifts availabilities of substrates for microorganisms in the reticulo-rumen and hindgut and can result in a dysbiotic microbiota that are characterised by low richness, diversity and functionality. Also, amylolytic microorganisms become more dominant at the expense of proteolytic and fibrolytic ones. Opportunistic microorganisms can take advantage of newly available niches, which, combined with reduced functionalities of epithelia, can contribute to an overall reduction in nutrient utilisation and increasing endotoxins and pathogens in digesta and faeces. The reduced barrier function of epithelia increases translocation of these endotoxins and other immunogenic compounds out of the digestive tract, which may be the cause of inflammations. This needs to be confirmed by determining the toxicity of these compounds. Cows differ in their susceptibility to poor gastrointestinal health, due to variations in genetics, feeding history, diet adaptation, gastrointestinal microbiota, metabolic adaptation, stress and infections. These differences may also offer opportunities for the management of gastrointestinal health. Strategies to prevent SARA include balancing the diet for physical effective fibre, non-fibre carbohydrates and starch, managing the different fractions of non-fibre carbohydrates, and consideration of the type and processing of grain and forage digestibility. Gastrointestinal health disorders due to high grain feeding may be attenuated by a variety of feed supplements and additives, including buffers, antibiotics, probiotics/direct fed microbials and yeast products. However, the efficacy of strategies to prevent these disorders must be improved. This requires a better understanding of the mechanisms through which these strategies affect the functionality of gastrointestinal microbiota and epithelia, and the immunity, inflammation and 'gastrointestinal-health robustness' of cows. More representative models to induce SARA are also needed.

Microbial diversity in the rumen, reticulum, omasum, and abomasum of yak on a rapid fattening regime in an agro-pastoral transition zone

The ruminant digestive system harbors a complex gut microbiome, which is poorly understood in the case of the four stomach compartments of yak. High-throughput sequencing and quantitative PCR were used to analyse microbial communities in the rumen, reticulum, omasum, and abomasum of six domesticated yak. The diversity of prokaryotes was higher in reticulum and omasum than in rumen and abomasum. Bacteroidetes predominated in the four stomach compartments, with abundance gradually decreasing in the trend rumen > reticulum > omasum > abomasum. Microorganism composition was different among the four compartments, all of which contained high levels of bacteria, methanogens, protozoa and anaerobic fungi. Some prokaryotic genera were associated with volatile fatty acids and pH. This study provides the first insights into the microorganism composition of four stomach compartments in yak, and may provide a foundation for future studies in this area.

Effect of individual SCFA on the epithelial barrier of sheep rumen under physiological and acidotic luminal pH conditions

The objective of this study was to investigate whether individual short-chain fatty acids (SCFA) have a different potential to either regulate the formation of the ruminal epithelial barrier (REB) at physiological pH or to damage the REB at acidotic ruminal pH. Ruminal epithelia of sheep were incubated in Ussing chambers on their mucosal side in buffered solutions (pH 6.1 or 5.1) containing no SCFA (control), 30 mM of either acetate, propionate or butyrate, or 100 mM acetate. Epithelial conductance (Gt), short-circuit current (Isc), and fluorescein flux rates were measured over 7 h. Thereafter, mRNA and protein abundance, as well as localization of the tight junction proteins claudin (Cldn)-1, -4, -7, and occludin were analyzed. At pH 6.1, butyrate increased Gt and decreased Isc, with additional decreases in claudin-7 mRNA and protein abundance (each P < 0.05) and disappearance of Cldn-7 immunosignals from the stratum corneum. By contrast, the mRNA abundance of Cldn-1 and/or Cldn-4 were upregulated by 30 mM propionate, 30 mM butyrate, or 100 mM acetate (P < 0.05), however, without coordinated changes in protein abundance. At luminal pH 5.1, neither Gt, Isc, nor TJ protein abundance was altered in the absence of SCFA; only fluorescein flux rates were slightly increased (P < 0.05) and fluorescein signals were no longer restricted to the stratum corneum. The presence of acetate, propionate, or butyrate at pH 5.1 increased fluorescein flux rates and Gt, and decreased Isc (each P < 0.05). Protein abundance of Cldn-1 was decreased in all SCFA treatments but 30 mM butyrate; abundance of Cldn -4 and -7 was decreased in all SCFA treatments but 30 mM acetate; and abundance of occludin was decreased in all SCFA treatments but 30 mM propionate (each P < 0.05). Immunofluorescence staining of SCFA-treated tissues at pH 5.1 showed disappearance of Cldn-7, discontinuous pattern for Cldn-4 and blurring of occludin and Cldn-1 signals in tight junction complexes. The fluorescein dye appeared to freely diffuse into deeper cell layers. The strongest increase in Gt and consistent decreases in the abundance and immunosignals of tight junction proteins were observed with 100 mM acetate at pH 5.1. We conclude that SCFA may contribute differently to the REB formation at luminal pH 6.1 with possible detrimental effects of butyrate at 30 mM concentration. At luminal pH 5.1, all SCFA elicited REB damage with concentration appearing more critical than SCFA species.