Formation of ethane and propane via abiotic reductive conversion of acetic acid in hydrothermal sediments.

A mechanistic understanding of formation pathways of low-molecular-weight hydrocarbons is relevant for disciplines such as atmospheric chemistry, geology, and astrobiology. The patterns of stable carbon isotopic compositions (δ13C) of hydrocarbons are commonly used to distinguish biological, thermogenic, and abiotic sources. Here, we report unusual isotope patterns of nonmethane hydrocarbons in hydrothermally heated sediments of the Guaymas Basin; these nonmethane hydrocarbons are notably 13C-enriched relative to sedimentary organic matter and display an isotope pattern that is reversed relative to thermogenic hydrocarbons (i.e., δ13C ethane > δ13C propane > δ13C n-butane > δ13C n-pentane). We hypothesized that this pattern results from abiotic reductive conversion of volatile fatty acids, which were isotopically enriched due to prior equilibration of their carboxyl carbon with dissolved inorganic carbon. This hypothesis was tested by hydrous pyrolysis experiments with isotopically labeled substrates at 350 °C and 400 bar that demonstrated 1) the exchange of carboxyl carbon of C2 to C5 volatile fatty acids with 13C-bicarbonate and 2) the incorporation of 13C from 13C-2-acetic acid into ethane and propane. Collectively, our results reveal an abiotic formation pathway for nonmethane hydrocarbons, which may be sufficiently active in organic-rich, geothermally heated sediments and petroleum systems to affect isotopic compositions of nonmethane hydrocarbons.

Investigating the chemical composition, digestion and fermentation of Alternanthera sessilis red plant and its effect on the performance of fattening lambs.

The present experiment was conducted to evaluate the nutritional value of red Alternanthera sessilis for fattening lambs when they were replaced with alfalfa forage. Forty growing lambs with an average weight of 21.12 kg and an age of 5 months were randomly assigned to four experimental treatments. Growth performance, nutrient digestibility, rumen fermentation parameters, protozoa population, blood parameters, and composition of carcass components were evaluated. The results of this experiment showed that the use of Alternanthera sessilis in the diet significantly reduced feed intake, increased the average daily weight gain, and improved the feed conversion ratio compared to the control treatment (P < 0.05). The digestibility of dry matter and protein was significantly increased (P < 0.05), while the digestibility of neutral detergent fiber, acid detergent fiber, and organic matter showed a numerical increase. Diets containing different levels of the Alternanthera sessilis plant did not affect pH, but the increase in the amount of this plant in the diet led to an increase ammonia nitrogen concentration and rumen protozoa population (P < 0.05). The addition of Alternanthera sessilis to the diet significantly reduced the concentration of blood glucose and cholesterol and increased the concentration of blood urea nitrogen (P < 0.05). Except for the weight of the thigh and neck, the effect of experimental treatments on other carcass components was not significant. Overall, the results of this experiment showed that using the Alternanthera sessilis plant in the rations of fattened lambs as a substitute for alfalfa forage not only had no negative effect on the studied parameters but also improved them in some cases. Therefore, Alternanthera sessilis can be used in rations of fattened lambs as a substitute for part of alfalfa forage.

High-Efficiency Recovery of Acetic Acid from Water Using Electroactive Gas-Stripping Membranes.

Recovery of carbon-based resources from waste is a critical need for achieving carbon neutrality and reducing fossil carbon extraction. We demonstrate a new approach for extracting volatile fatty acids (VFAs) using a multifunctional direct heated and pH swing membrane contactor. The membrane is a multilayer laminate composed of a carbon fiber (CF) bound to a hydrophobic membrane and sealed with a layer of polydimethylsiloxane (PDMS); this CF is used as a resistive heater to provide a thermal driving force for PDMS that, while a highly hydrophobic material, is known for its ability to rapidly pass gases, including water vapor. The transport mechanism for gas transport involves the diffusion of molecules through the free volume of the polymer matrix. CF coated with polyaniline (PANI) is used as an anode to induce an acidic pH swing at the interface between the membrane and water, which can protonate the VFA molecule. The innovative multilayer membrane used in this study has successfully demonstrated a highly efficient recovery of VFAs by simultaneously combining pH swing and joule heating. This novel technique has revealed a new concept in the field of VFA recovery, offering promising prospects for further advancements in this area. The energy consumption was 3.37 kWh/kg for acetic acid (AA), and an excellent separation factor of AA/water of 51.55 ± 2.11 was obtained with high AA fluxes of 51.00 ± 0.82 g.m-2hr-1. The interfacial electrochemical reactions enable the extraction of VFAs without the need for bulk temperature and pH modification.

Responses of CH4, N2O, and NH3 emissions to different slurry pH values of 5.5-10.0: Characteristics and mechanisms.

Animal slurry storage is a significant source of greenhouse gas (GHG) and ammonia (NH3) emissions. pH is a basic but key factor that could pose great influence on gas emissions, but the simultaneous evaluation of its influence on GHG and NH3 emissions and the understanding of its underlying mechanism are not enough. In this work, pH was adjusted between 5.5 and 10.0 by a step of 0.5 unit by adding lactic acid and sodium hydroxide (NaOH) properly and frequently to the stored slurry during a 43-day storage period. The cumulative NH3 emissions were linearly correlated with the slurry pH, with R2 being 0.982. Maintaining the slurry pH at 5.5-6.0 could reduce NH3 emissions by 69.4%-85.1% compared with the non-treated group (CK). The pH ranges for maximum methane (CH4) and nitrous oxide (N2O) emissions were 7.5-8.5 and 6.5-8.5, respectively, and the slurry under pH 7.5-8.5 showed the highest GHG emissions. Acidification to pH 5.5 helped reduce the CH4, N2O, and total GHG emissions by 98.0%, 29.3%, and 81.7%, respectively; while alkalinization to pH 10.0 helped achieve the mitigation effects of 74.1%, 24.9%, and 30.6%, respectively. The Pearson's correlation factor between CH4 and the gene copy of mcrA under different pH values was 0.744 (p < 0.05). Meanwhile, the correlation factors between N2O and the gene copies of amoA, narG, and nirS were 0.644 (p < 0.05), 0.719 (p < 0.05), and 0.576 (p = 0.081), respectively. The gene copies of mcrA, amoA, narG, and nirS were maintained at the lowest level under pH 5.5. These results recommended keeping slurry pH lower than 5.5 with lactic acid can help control GHG and NH3 emissions simultaneously and effectively.

The impact of lactating Hu sheep's dietary protein levels on lactation performance, progeny growth and rumen development.

This study aimed to investigate whether lactating Hu sheep's dietary protein levels could generate dynamic effects on the performance of their offspring. Twelve ewes with similar parity were fed iso-energy diets which contained different protein levels (P1: 9.82%, P2: 10.99%) (n = 6), and the corresponding offspring were divided into SP1 and SP2 (n = 12). At 60 days, half of the lambs were harvested for further study: the carcass weight (p = 0.043) and dressing percentage (p = 0.004) in the SP2 group were significantly higher than SP1. The acetic acid (p = 0.007), propionic acid (p = 0.003), butyric acid (p < 0.001) and volatile fatty acids (p < 0.001) in rumen fluid of SP2 were significantly lower than SP1. The expression of MCT2 (p = 0.024), ACSS1 (p = 0.039) and NHE3 (p = 0.006) in the rumen of SP2 was lower than SP1, while the HMGCS1 (p = 0.026), HMGCR (p = 0.024) and Na+/K+-ATPase (p = 0.020) was higher than SP1. The three dominant phyla in the rumen are Bacteroidetes, Proteobacteria and Firmicutes. The membrane transport, amino acid metabolism and carbohydrate metabolism of SP1 were relatively enhanced, the replication and repair function of SP2 was relatively enhanced. To sum up, the increase of dietary protein level significantly increased the carcass weight and dressing percentage of offspring and had significant effects on rumen volatile fatty acids, acetic acid activation and cholesterol synthesis related genes. HIGHLIGHTSIn the early feeding period, the difference in ADG of lambs was mainly caused by the sucking effect.The increase in dietary protein level of ewes significantly increased the carcass weight and dressing percentage of offspring.The dietary protein level of ewes significantly affected the volatile fatty acids (VFAs) and genes related to acetic acid activation and cholesterol synthesis in the rumen of their offspring.The membrane transport, amino acid metabolism and carbohydrate metabolism of the offspring of ewes fed with a low protein diet were relatively enhanced.The replication and repair function of the offspring of ewes fed with a high protein diet was relatively strengthened.

Deciphering different effects of ZVI and NaOH on metabolic characteristics in the process of methanogenesis recovery from VFA suppression.

Dosing zero valent iron (ZVI) or sodium hydroxide (NaOH) is the common method of addressing acidification in anaerobic digestion (AD) systems; however, few studies have discussed and compared their effects on microbial metabolism. In the present study, microbial syntrophy and metabolic pathways under ZVI and NaOH regulation are comparatively analyzed through microbial network analysis and metagenomic/metaproteomic analyses. CH4 yield in the ZVI reactor was 414 mL/gVS, an increase of 23% when compared with that in the reactor with NaOH dosing (336 mL/gVS). The methanogenesis recovery period in the ZVI reactor (37 days) was shorter than that in the NaOH reactor (48 days). Co-occurrence networks indicated that ZVI promoted Methanoculleus and Methanosarcina to establish a complex syntrophic association with SAO bacteria (Syntrophaceticus and Aminobacterium) and syntrophic acetogens (Syntrophomonas), strengthening SAO-hydrogenotrophic methanogenesis (HM) and acetoclastic methanogenesis (AM) pathways simultaneously. Metagenomic analysis showed that the relative abundance of mcrA and fwdB in the ZVI reactor was higher 27% than that in the NaOH reactor. Furthermore, through metaproteomics analysis, much more enzymes related to glucose degradation, bioconversion of butyric acid and pyruvate, conversion of formate and acetate to CO2, and production of CH4 from acetate and CO2 were significantly upregulated under ZVI regulation than under NaOH regulation (fold change relative to control [FC] > 1.5, p < 0.05). The results of the present study enhance our understanding of methanogenic mechanisms under the regulation of ZVI, providing a theoretical basis for its practical application in AD systems experiencing VFA suppression.

Effect of Brazilian spinach (Alternanthera sissoo) pellet supplementation and dietary ratios on rumen characteristics, microorganisms, methane production, milk yield, and milk composition in dairy cows.

The aim of the previous research was to evaluate the effects of Brazilian spinach pellet (BSP) supplementation and dietary ratios on rumen characteristics, methane estimation, and milk production in dairy cows. Four crossbred Thai dairy cattle, with Holstein Friesian (HF) cows with a body weight of 442 ± 50 kg were assessed in a 2 × 2 factorial in a 4 × 4 Latin square design to obtain diets; factor A was the roughage (R) to concentrate (C) ratio at 40:60 and 30:70, and factor B was level of BSP supplantation at 2% and 6% of dry matter (basis) intake (DMI). R:C ratio and supplementation of BSP had no interaction effect on DMI and nutrient digestibility. On DM, organic matter (OM), crude protein (CP), and acid detergent fiber (ADF) intake, the R:C ratio increased (p < 0.05). The digestibility of OM improved (p < 0.05) when cows were fed a R:C ratio of 30:70. On pH, ammonia-nitrogen, protozoal population, and blood urea-nitrogen, there were no interactions between the R:C ratio and BSP supplementation. Increasing the BSP supplementation to 6% (p < 0.01) decreased the protozoal population. The R:C ratio of 30:70 increased total volatile fatty acid (VFA) and propionate (C3) concentrations while decreasing the acetate (C2) to C3 ratio and methane (CH4 ) estimation (p < 0.01). The average concentration of total VFA has increased by 114.46 mmol/L for 6% of BSP supplementation. Increased BSP supplementation increased the C3 concentration while decreasing the C2:C3 ratio and CH4 emissions (p < 0.05). The R:C ratio and BSP supplementation had no interaction effect on milk yield, 3.5% fat-corrected milk (FCM), or milk composition. The R:C ratio of 30:70 increased milk yield (p < 0.05) to the highest level of 12.18 kg/day. In conclusion, the diet containing a R:C ratio of 30:70 increased feed intake, milk yield, BUN, total VFA, and C3 concentration, and decreased the C2:C3 ratio and CH4 emission. BSP supplementation at 6% could increase TVFA and C3 concentrations while decreasing the protozoal population and CH4 estimation.

Age-dependent variations in rumen bacterial community of Mongolian cattle from weaning to adulthood.

BACKGROUND: Rumen microbes play an important role in ruminant energy supply and animal performance. Previous studies showed that the rumen microbiome of Mongolian cattle has adapted to degrade the rough forage to provide sufficient energy to tolerate the harsh desert ecological conditions. However, little is known about the succession of rumen microbes in different developmental stages of post-weaning Mongolian cattle. METHODS: Here, we examined the succession of the rumen microbial composition and structure of 15 post-weaning Mongolian cattle at three developmental stages i.e., 5 months (RM05), 18 months (RM18) and, 36 months (RM36) by using the 16S rRNA gene sequencing method. RESULTS: We did not find any age-dependent variations in the ruminal concentrations of any volatile fatty acid (VFA) of Mongolian cattle. The diversity of the rumen bacterial community was significantly lower in RM05 group, which reached to stability with age. Bacteroidetes and Firmicutes were the two dominant phyla among all age groups. Phylum Actinobacteria was significantly higher in RM05 group, phyla Spirochaetes, and Tenericutes were highly abundant in RM18 group, and phyla Proteobacteria and Epsilonbacteraeota were enriched in RM36 group. Genera Prevotella_1, Bacteroides, and Bifidobacterium were abundant in RM05 group. The short chain fatty acid (SCFA) producing bacteria Rikenellaceae_RC9_gut_group showed high abundance in RM18 group and fiber degrading genus Alloprevotella was highly abundant in RM36 group. Random forest analysis identified Alloprevotella, Ileibacterium, and Helicobacter as important age discriminatory genera. In particular, the genera Ruminococcaceae_UCG-005, Bacteroides, Saccharofermentans, and Fibrobacter in RM05, genera [Eubacterium] coprostanoligenes_group, Erysipelotrichaceae_UCG-004, Helicobacter, Saccharofermentans, Papillibacter, and Turicibacter in RM18, and genera Rikenellaceae_RC9_gut_group, Lachnospiraceae_AC2044_group, and Papillibacter in RM36 showed the top interactions values in the intra-group interaction network. CONCLUSIONS: The results showed that rumen microbiota of Mongolian cattle reached to stability and maturity with age after weaning. This study provides some theoretical evidence about the importance of functional specific rumen bacteria in different age groups. Further studies are needed to determine their actual roles and interactions with the host.

Changes in rumen microbial community composition in yak in response to seasonal variations.

AIMS: Yak is a dominant ruminant, well adapted to grazing on pasture year around in the harsh climate of the 3000-meter-high Qinghai-Tibetan Plateau. The complex microbial community that resides within the yak rumen is responsible for fermentation and contributes to its climatic adaptation. This study aimed to characterize the rumen microbiota responses to wide seasonal variations, especially those necessary for survival in the cold seasons. METHODS AND RESULTS: In the present study, we performed 16s rRNA gene sequencing to investigate the seasonal variations in microbiota composition, diversity and associated volatile fatty acids (VFAs) in yak rumen. The results showed that rumen microbiota were dominated by Bacteroides (72.13%-78.54%) and Firmicutes; the relative abundance of Firmicutes was higher in summer (17.44%) than in winter (10.67%; p < 0.05). The distribution of taxa differed among spring, summer and winter rumen communities (PERMANOVA, p = 0.001), whereas other taxa (e.g., Fibrobacter, Verrucomicrobia, Anaerostipes and Paludibacter), which could potentially help overcome harsh climate conditions were observed in higher abundance during the cold spring and winter seasons. The highest total VFA concentration in the yak rumen was obtained in summer (p < 0.05), followed by spring and winter, and both positive and negative correlations between VFAs and specific genera were revealed. CONCLUSIONS: Microbiota in yak rumen appear to be highly responsive to seasonal variations. Considering environmental factors, we suggest that seasonal adaptation by microbial communities in rumen enables their hosts to survive seasonal scarcity and cold stress in the spring and winter. SIGNIFICANCE AND IMPACT OF STUDY: The present study furthers our understanding of how microbial adaptation to seasonal variations in nutrient availability and climate may function in high plateau ruminants, providing insights into the tripartite relationship between the environment, host and microbiota.

Effect of microwave/hydrothermal combined ionic liquid pretreatment on straw: Rumen anaerobic fermentation and enzyme hydrolysis.

To explore green technology for wheat straw pretreatment, this study combined the microwave or hydrothermal with ionic liquid ([Bmim][OAc]) on wheat straw followed by rumen fermentation. The optimal conditions of microwave assisted ionic liquids pretreatment (M-I) and hydrothermal assisted ionic liquids pretreatment (H-I) treatment were 360 W and 200 °C, and the corresponding lignin removal rates reached 35.3% and 25.4%, respectively. Rumen fermentation showed that the highest volatile fatty acid (VFA) yield was found in M-I group, followed by H-I group at 234 and 180 mg/g, respectively. As for enzymatic hydrolysis, the saccharification rates at 3 days of M-I (360 W) and H-I (200 °C) were determined to be 393 and 320 mg/g. The optimal ionic liquid dosage was determined to be 30% in consideration of cost and VFA conversion rate. M-I pretreatment plus the rumen fermentation enjoyed the benefit of no enzyme addition and high product recovery, which was worth further investigating.

Effects of acetate, propionate, and pH on volatile fatty acid thermodynamics in continuous cultures of ruminal contents.

To investigate the effects of acetate, propionate, and pH on thermodynamics of volatile fatty acids (VFA) in the rumen, a dual-flow continuous culture study was conducted to quantify production of major VFA, interconversions among the VFA, and H2 and CH4 emissions in a 4 × 4 Latin square design. The 4 treatments were (1) control: pH buffered to an average of 6.75; (2) control plus 20 mmol/d of infused acetate (InfAc); (3) control plus 7 mmol/d of infused propionate (InfPr); and (4) a 0.5-unit decline in pH elicited by adjustment of the buffer (LowpH). All fermentors were fed 40 g of a pelleted diet containing whole alfalfa pellets and concentrate mix pellets (50:50) once daily. After 7 d of treatment, sequential, continuous infusions of [2-13C] sodium acetate (3.5 mmol/d), [U-13C] sodium propionate (2.9 mmol/d), and [1-13C] sodium butyrate (0.22 mmol/d) were carried out from 12 h before feeding for 36 h. Filtered liquid effluent (4 mL) was sampled at 0, 2, 4, 6, 8, 12, 16, and 22 h after feeding, and assessed for VFA concentrations, with another filtered sample (20 mL) used to quantify aqueous concentrations of CH4 and H2. Headspace CH4 and H2 gases were monitored continuously. Ruminal microbes were isolated from the mixed effluent samples, and the microbial community structure was analyzed using the 16S rRNA amplicon sequencing technique. The digestibility of neutral detergent fiber, acid detergent fiber, and starch and microbial C sequestrated from VFA were not affected by treatments. The LowpH treatment increased net propionate production and decreased H2 and CH4 headspace emissions, primarily due to shifts in metabolic pathways of VFA formation, likely due to the observed changes in bacterial community structure. Significant interconversions occurred between acetate and butyrate, whereas interconversions of other VFA with propionate were relatively small. The InfAc and InfPr treatments increased net acetate and propionate production, respectively; however, interconversions among VFA were not affected by pH, acetate, or propionate treatments, suggesting that thermodynamics might not be a primary influencer of metabolic pathways used for VFA formation.

Enhanced degradation of glucocorticoids, a potential COVID-19 remedy, by co-fermentation of waste activated sludge and animal manure: The role of manure type and degradation mechanism.

Waste activated sludge (WAS) and animal manure are two significant reservoirs of glucocorticoids (GCs) in the environment. However, GC degradation during anaerobic digestion (AD) of WAS or animal manure has rarely been investigated. In this study, co-fermentation of WAS and animal manure was conducted to investigate the performance of AD in controlling GC dissemination. Effects of manure type on GC degradation and sludge acidification were investigated. The results showed that co-fermentation of WAS and chicken manure (CM) significantly enhanced the degradation of hydrocortisone (HC) to 99%, betamethasone (BT) to 99%, fluocinolone acetonide (FA) to 98%, and clobetasol propionate (CP) to 82% in 5 days with a mixing ratio of 1:1 (g TS sludge/g dw manure) at 55 °C and initial pH of 7. Simultaneously, sludge reduction was increased by 30% and value-added volatile fatty acid (VFA) production was improved by 40%. Even a high GC content of biomass (3.6 mg/g TS) did not impact both sludge hydrolysis and acidification. The amendment of WAS with CM increased soluble organic carbon, Ca2+, and relative abundance of anaerobes (Eubacterium) associated with organic compound degradation. Furthermore, 44 transformation products of HC, BT, FA, and CP with lower lipophilicity and toxicity were identified, indicating possible degradation pathways including hydroxylation, ketonization, ring cleavage, defluorination, hydrogenation, methylation, and de-esterification. Overall, this study provides a practical way to control GC pollution and simultaneously promote waste reduction and VFA production. Animal manure type as an overlooked factor for influencing co-fermentation performance and pollutant degradation was also highlighted.

Rumen volatile fatty acid molar proportions, rumen epithelial gene expression, and blood metabolite concentration responses to ruminally degradable starch and fiber supplies.

The objective of this work was to characterize rumen volatile fatty acid (VFA) concentrations, rumen epithelial gene expression, and blood metabolite responses to diets with different starch and fiber sources. Six ruminally cannulated yearling Holstein heifers (body weight = 330 ± 11.3 kg) were arranged in a partially replicated Latin square experiment with 4 treatments consisting of different starch [barley (BAR) or corn (CRN)] and fiber [timothy hay (TH) or beet pulp (BP)] sources. Treatments were arranged as a 2 × 2 factorial. Beet pulp and TH were used to create relative changes in apparent ruminal fiber disappearance, whereas CRN and BAR were used to create relative changes in apparent ruminal starch disappearance. Each period consisted of 3 d of diet adaptation and 15 d of dietary treatment. In situ disappearance of fiber and starch were estimated from bags incubated in the rumen from d 10 to 14. From d 15 to 17, rumen fluid was collected every hour from 0500 to 2300 h. Rumen fluid samples were pooled by animal/period and analyzed for pH and VFA concentrations. On d 18, 60 to 80 papillae were biopsied from the epithelium and preserved for gene expression analysis. On d 18, one blood sample per heifer was collected from the coccygeal vessel. In situ ruminal starch disappearance rate (7.30 to 8.72%/h for BAR vs. 7.61 to 10.5%/h for CRN) and the extent of fiber disappearance (22.2 to 33.4% of DM for TH vs. 34.4 to 38.7% of DM for BP) were affected by starch and fiber source, respectively. Analysis of VFA molar proportions showed a shift from propionate to acetate, and valerate to isovalerate on TH diets compared with BP. Corn diets favored propionate over butyrate in comparison to BAR diets. Corn diets also had higher molar proportions of valerate. Expression of 1 gene (SLC9A3) were increased in BP diets and 2 genes (BDH1 and SLC16A4) tended to be increased in TH diets. Plasma acetate demonstrated a tendency for a starch by fiber interaction with BAR-BP diets having the highest plasma acetate, but other metabolites measured were not significant. These results suggest that TH has the greatest effect on shifts in VFA molar proportions and epithelial transporters, but does not demonstrate shifts in blood metabolite concentrations.

Conditions stimulating neutral detergent fiber degradation by dosing branched-chain volatile fatty acids. I: Comparison with branched-chain amino acids and forage source in ruminal batch cultures.

Three experiments assessed branched-chain volatile fatty acid (BCVFA) stimulation of neutral detergent fiber (NDF) disappearance after 24 h of incubation in batch cultures derived from ruminal fluid inocula that were enriched with particulate-phase bacteria. In experiment 1, a control was compared with 3 treatments with isomolar doses of all 3 BCVFA (plus valerate), all 3 branched-chain AA (BCAA), or half of each BCVFA and BCAA mix with either alfalfa or grass hays (50%) and ground corn grain (50%). A portion of the BCAA and BCVFA doses were enriched with 13C, and valerate (also enriched with 13C) was added with BCVFA. Although BCAA yielded a similar production of BCVFA compared with dosing BCVFA, equimolar substitution of BCVFA for BCAA decreased the percentage of N in bacterial pellets when alfalfa hay was fed but increased N when grass hay was fed. Substituting BCVFA for BCAA increased total fatty acid (FA) concentration with alfalfa hay. Dosing of BCAA or BCVFA did not affect total branched-chain FA, iso-FA, or anteiso-FA percentages in bacterial total FA, whereas numerous individual FA isomers and their 13C enrichments were affected by these treatments. Increasing recovery of the 13C dose from respective labeled BCVFA primers indicated facilitated BCVFA uptake and incorporation into FA compared with BCAA, whereas increased recovery of 13C from labeled BCAA in the bacteria pellet but not in the FA fraction suggested direct assimilation into bacterial protein. The BCVFA and valerate were dosed in varying combinations that either summed to 4 mM (experiment 2) or had only 1 mM no matter what combination (experiment 3). In general, grass hay was more responsive to stimulation in NDF digestibility by BCVFA than was alfalfa hay, which was attributed to the higher degradable protein in the latter. The net production of the BCVFA (after subtracting dose) was affected by source and combination of BCVFA. Isovalerate dosing tended to increase its own net production; in contrast, isobutyrate seemed to be used more when it was added alone, but 2-methylbutyrate seemed to be preferred over isobutyrate when 2-methylbutyrate was added. Results supported potential interactions, including potential feedback in production from feed BCAA or increased concentration-dependent competition for dosed BCVFA into cellular products. Under our conditions, the BCVFA appear to be more readily available than BCAA, probably because of regulated BCAA transport and metabolism. Valerate consistently provided no benefit. Using nonparametric ranking, all 3 BCVFA or either isovalerate or isobutyrate (both yielding iso-FA) should be combined with 2-methylbutyrate (yielding anteiso-FA) as a potential opportunity to improve NDF digestibility when rumen-degraded BCAA are limited in diets to decrease environmental impact from N in waste.

Conditions stimulating neutral detergent fiber degradation by dosing branched-chain volatile fatty acids. II: Relation with solid passage rate and pH on neutral detergent fiber degradation and microbial function in continuous culture.

To support improving genetic potential for increased milk production, intake of digestible carbohydrate must also increase to provide digestible energy and microbial protein synthesis. We hypothesized that the provision of exogenous branched-chain volatile fatty acids (BCVFA) would improve both neutral detergent fiber (NDF) degradability and efficiency of microbial protein synthesis. However, BCVFA should be more beneficial with increasing efficiency of bacterial protein synthesis associated with increasing passage rate (kp). We also hypothesized that decreasing pH would increase the need for isobutyrate over 2-methylbutyrate. To study these effects independent from other sources of variation in vivo, we evaluated continuous cultures without (control) versus with BCVFA (0 vs. 2 mmol/d each of isobutyrate, isovalerate, and 2-methylbutyrate), low versus high kp of the particulate phase (2.5 vs. 5.0%/h), and high versus low pH (ranging from 6.3 to 6.8 diurnally vs. 5.7 to 6.2) in a 2 × 2 × 2 factorial arrangement of treatments. Diets were 50% forage pellets and 50% grain pellets administered twice daily. Without an interaction, NDF degradability tended to increase from 29.7 to 35.0% for main effects of control compared with BCVFA treatments. Provision of BCVFA increased methanogenesis, presumably resulting from improved NDF degradability. Decreasing pH decreased methane production. Total volatile fatty acid (VFA) and acetate production were decreased with increasing kp, even though true organic matter degradability and bacterial nitrogen flow were not affected by treatments. Decreasing pH decreased acetate but increased propionate and valerate production, probably resulting from a shift in bacterial taxa and associated VFA stoichiometry. Decreasing pH decreased isobutyrate and isovalerate production while increasing 2-methylbutyrate production on a net basis (subtracting doses). Supplementing BCVFA improved NDF degradability in continuous cultures administered moderate (15.4%) crude protein diets (excluding urea in buffer) without major interactions with culture pH and kp.

Influence of volatile fatty acids in anaerobic bioleaching of potentially toxic metals.

Potentially toxic metals are common contaminants associated with sewage sludge, and limited information is available on migration and transformation behavior of potentially toxic metals during anaerobic digestion (AD) process. The aim of this study was to reveal the influence of volatile fatty acids (VFAs) on the solubilization of metals through VFAs-metal complexation. Addition of readily biodegradable extra carbon source at organic loading rate (OLR) of 17.65 gVS/L.d resulted in accumulation of 67,255 mg chemical oxygen demand (COD)/L as VFAs. Low pH values due to VFAs accumulation enhanced the solubilization of Ni and more than 22% of its total concentration became soluble. Subsequent to consumption of VFAs and increase of pH to neutral levels (~7.5), solubility of Ni decreased below 10% of its total concentration. Contrarily, the solubility of Cr reached to 25% of its total concentration at neutral pH values. Presumably the complexation of Cr with dissolved organic matter (DOM) have increased its concentration in the liquid fraction at neutral pH values. Fractionation analysis of metals revealed that AD process altered Cu and Zn speciation between organically-bound and residual fractions, and hence solubility of Zn and Cu remained consistently low over the entire period of the AD process.

Effect of sugarcane bagasse as industrial by-products treated with Lactobacillus casei TH14, cellulase and molasses on feed utilization, ruminal ecology and milk production of mid-lactating Holstein Friesian cows.

BACKGROUND: The study aimed to evaluate the effect of Lactobacillus casei TH14, cellulase, and molasses combination fermented sugarcane bagasse (SB) as an exclusive roughage source in the total mixed ration (TMR) for mid-lactation 75% crossbred Holstein cows on feed intake, digestibility, ruminal ecology, milk yield and milk composition. Four multiparous mid-lactation crossbred (75% Holstein Friesian and 25% Thai native breed) dairy cows of 439 ± 16 kg body weight, 215 ± 5 days in milk and average milk yield 10 ± 2 kg d-1 were assigned to a 4 × 4 Latin square design. The unfermented SB (SB-TMR), SB fermented with cellulase and molasses (CM-TMR), SB fermented with L. casei TH14 and molasses (LM-TMR), and SB fermented with L. casei TH14, cellulase and molasses (LCM-TMR) were used as dietary treatments. RESULTS: CM-TMR, LM-TMR and LCM-TMR significantly (P < 0.01) increased dry matter and fiber digestibility, gross energy and metabolizable energy intake (P < 0.05), blood glucose, total volatile fatty acids (P < 0.05), propionic acid and milk yield, but decreased ammonia, acetic acid, acetic:propionic ratio and methane production (P < 0.05) when compared with the SB-TMR. Compared with fermented SB treatments, LCM-TMR had lower (P < 0.05) ruminal ammonia and greater blood glucose (P < 0.01); LCM-TMR showed (P < 0.05) greater volatile fatty acids, propionic acid, milk yield and total solids, and lower acetic:propionic ratio (P < 0.01); methane, protozoa and somatic cell count were found to be lowest in LCM-TMR. CONCLUSION: Combination of L. casei TH14 and additives (LCM-TMR) effectively enhanced feed use, rumen ecology and milk production of Holstein Friesian cows. © 2021 Society of Chemical Industry.

Natural intoxication caused by protodioscin in lambs kept in Brachiaria pastures.

Protodioscin poisoning of Brachiaria spp. has been a serious problem for lambs in grazing systems. The defoliation process can stimulate the appearance of new leaves and, the younger leaves have a lower concentration of protodioscin. Thus, it was aimed to assess the effect of different leaf offerings on the protodioscin content in forage and if protodioscin can interfere with the dry matter intake (DMI) and on metabolic and productive parameters of lambs. Twelve tester lambs (average weight 17.5 ± 3.48 kg) were divided into four groups of different levels of dry leafy matter (60, 75, 90, or 105 g/kg body weight). In addition to these, 33 regulator lambs were used as needed to adjust the leaf offerings of pasture. The animals were divided and kept in 12 paddocks, each with a tester lamb. The DMI was estimated using chromic oxide as an external marker. In vitro digestibility and degradation kinetics and ruminal, blood, and urinary parameters were measured in the forage sampled by the hand plucking method. The protodioscin concentration in forage was determined by high-performance liquid chromatography. The DMI increased linearly as a result of the supply of leaves. However, the protodioscin content and its consumption showed a quadratic behavior. There was no effect of leaf supply on in vitro digestibility, in vitro degradation kinetics of forage, and on ruminal, blood, and urinary parameters of lambs. However, a negative correlation was observed between the DMI and the concentration of protodioscin at the highest level of leaf supply. This is due to the fact that in the most intense grazing, there is a stimulus for greater regrowth; therefore, there was an increase in the concentration of protodioscin in forages in older forages. Protodioscin poisoning was confirmed by urinary and blood parameters.

Optimizing food waste hydrothermal parameters to reduce Maillard reaction and increase volatile fatty acid production.

The occurrence of the Maillard reaction and melanoidins formation during the hydrothermal treatment of food waste can reduce the yield of volatile fatty acids (VFA); however, few studies have investigated the adverse effects of the Maillard reaction. This study identified the impact of hydrothermal treatment parameters on hydrolysis and melanoidins formation and optimized the hydrothermal treatment conditions to enhance VFA production by minimizing the impact of the Maillard reaction. A response surface methodology was employed to optimize the hydrothermal treatment parameters and VFA production was evaluated. Results showed that temperature, reaction time, and pH were significant interacting factors with respect to hydrolysis and melanoidins formation while the C/N ratio and moisture content of food waste had little impact. The optimal conditions for hydrothermal treatment (temperature of 132 °C, reaction time of 27 min, and a pH of 5.6) enhanced VFA production by 22.1%. Under optimal hydrothermal treatment conditions, a higher initial C/N ratio further increased VFA production.

Undernutrition shifted colonic fermentation and digest-associated bacterial communities in pregnant ewes.

The objective of this study was to evaluate the effect of undernutrition on colonic microbiota and fermentation in pregnant ewes. Sixteen ewes bearing multiple fetuses for 115 days in the control (CON) and severe feed restriction (SFR) groups were fed 100% and 30% level of ad libitum feed intake, respectively. After 15-day treatment, all ewes were sacrificed to collect colonic digesta samples to extract DNA for 16S rRNA sequencing and to detect fermentation parameters. Our data showed that SFR increased (P < 0.05) the levels of colonic propionate, isobutyrate, butyrate, isovalerate, and valerate, and slightly decreased (P < 0.1) colonic pH. The mole proportions of isobutyrate, butyrate, and isovalerate were increased (P < 0.05) upon SFR while that of acetate was decreased (P < 0.05). Hematoxylin-eosin staining sections exhibited the disorderly, irregular, and loose arrangement and part sloughing of colonic epithelial cells. Furthermore, SFR decreased (P < 0.05) the diversity of colonic microbiota and changed the microbial communities. At the genus level, SFR increased (P < 0.05) the abundance of unclassified Peptococcaceae and decreased (P < 0.05) the abundances of Ruminococcus, unclassified Ruminococcaceae, and unclassified VadinBB60. Additionally, the abundances of Ruminococcus and unclassified Ruminococcaceae were positively correlated (P < 0.05) with the acetate proportion while the abundance of unclassified Peptococcaceae was negatively correlated (P < 0.05) with the percentages of isobutyrate, butyrate, and isovalerate. In summary, SFR diminished the diversity of bacteria, affected the composition of bacterial communities, and finally changed the colonic fermentation pattern and epithelial histomorphology in pregnant ewes. KEY POINTS: • Undernutrition changed colonic bacterial diversity and composition in pregnant ewes. • Microbial alteration affected colonic fermentation pattern and parameters. • Alteration of colonic microbiota and fermentation damaged epithelium histomorphology. Graphical abstract.