Total Volatile Fatty Acid Production Research Articles

The sustainable mitigation of in vitro ruminal biogas emissions by ensiling date palm leaves and rice straw with lactic acid bacteria and Pleurotus ostreatus for cleaner livestock production.

The sustainable utilization of date palm leaves (DPL) and rice straw (RS) as feed materials for ruminant was evaluated using an in vitro wireless gas production (GP) technique. DPL and RS were individually ensiled with lactic acid bacteria (LAB) for 45days or used as substrates for the cultivation of Pleurotus ostreatus (PO) mushroom for 35days. A total mixed ration was formulated as a control ration. In the other rations, berseem hay replaced DPL (ensiled without additives or ensiled with LAB or PO) at 25%, 50%, 75% and 100%. Ensiling with LAB did not affect the chemical composition of DPL or RS, while PO treatment reduced their fibre fraction contents. Ensiling without additives lowered (p<0.05) the asymptotic production of total gas, methane (CH4 ) and carbon dioxide (CO2 ), and the rate of CH4 and CO2 while increasing (p<0.05) the lag time of CH4 and CO2 production. Ensiling of materials with LAB and treatment with PO decreased (p<0.05) the asymptotic production of total gas, CH4 and CO2 production and decreased the rate of CH4 and CO2 production. Ensiling without additives decreased (p<0.05) total bacterial count, and increased (p<0.05) fermentation pH and total volatile fatty acids (VFA), while LAB-ensiled DPL increased (p<0.05) total VFA and propionate concentrations and decreased total protozoal count. The PO-treated DPL decreased (p<0.05) bacterial count, protozoal count and fermentation pH and increased total VFA production. Replacing berseem hay with LAB or PO-treated DPL at 25% increased GP; however, increased CH4 and CO2 production, whereas the other replacement levels decreased total gas, CH4 and CO2 production. The treatment with LAB is more recommended than the PO treatment.

Evaluation of in vitro energy distribution and methanogenic potential of two forages with the addition of condensed tannins

The objective of this work was to analyze the effect of the addition of condensed tannins (CT) in the efficiency of digestion, methanogenic potential and energy distribution between the fermentation products of two forages. An assay was carried out using the in vitro gas production technique in which extracts of Quebracho (Schinopsis balansae) and Lotus corniculatus were evaluated with fermentation patterns of derived products from Ryegrass (RG, Lolium perenne) and a tropical forage, Megathyrsus maximus (MM). Tannins were added to the substrate at a concentration of 30 mg g-1. MM presented higher and delayed gas production (GP), and in vitro dry matter, organic matter and fiber digestibilities (ivDMD, ivOMD and NDFD, respectively) were relatively high but lower than RG. In addition, MM presented higher CH4 production (CH4p) than RG in 24 and 48h. Even though CT of Quebracho induced a decrease in the NDFD, contrary to what was expected, CH4p was greater, although this effect could not be attributed to the presence of CT. The stoichiometric evaluation indicated that while the highest CH4p in Quebracho treatments were associated with acetogenic profiles, CH4p with Lotus did not show any relationship with the volatile fatty acids (VFA) profile, but it did show a relationship with the highest total VFA production and the highest GP.

High-Gossypol Whole Cottonseed Exhibited Mediocre Rumen Degradability and Less Microbial Fermentation Efficiency than Cottonseed Hull and Cottonseed Meal with an In Vitro Gas Production Technique

To explore whether or not the gossypol varied in cottonseed by-products affect rumen degradability and fermentation efficiency, an in vitro cumulative gas production experiment was applied with mixed rumen microorganism to compare rumen fermentation characteristics of whole cottonseed (WCS, n = 3 samples), cottonseed meal (CSM, n = 3 samples), and cottonseed hull (CSH, n = 2 samples). The five-replicate fermentation per sample per incubation time continuously lasted for 0.5, 1.5, 3, 6, 12, 24, 36, and 48 h with an automated gas production recording system. Regardless of distinct nutrient differences, the free gossypol level in these cottonseed by-products ranked: WCS &gt; CSH &gt; CSM. After 48 h of incubation, the in vitro dry matter degradability and ammonia N concentration ranked as: CSM &gt; WCS &gt; CSH. The cumulative gas production and total volatile fatty acid (VFA) levels in the culture fluids ranked: CSM &gt; CSH &gt; WCS, in which the average production rate ranked: CSM &gt; WCS &gt; CSH. Regarding the molar VFA pattern, WCS in comparison with CSH and CSM presented the lowest production of non-glucogenic acids (e.g., acetate) and exhibited the highest fermentation efficiency of energy from carbohydrates to VFAs. There was a significant negative correlation between the gossypol content and cumulative gas and total VFA production, suggesting that the greater gossypol in cottonseed by-products, the more detrimental effect occurred for rumen fermentation. In a brief, WCS exhibited mediocre rumen degradability and less microbial fermentation efficiency than CSH and CSM, depending on their gossypol levels.

Ruminal bacterial community is associated with the variations of total milk solid content in Holstein lactating cows.

Total milk solid (TMS) content directly reflects the quality of milk. Rumen bacteria ferment dietary components, the process of which generates the precursors for the synthesis of milk solid, therefore, the variation in rumen bacterial community could be associated with milk solid in dairy cows. In this study, 45 healthy mid-lactation Holstein dairy cows with the similar body weight, lactation stage, and milk yield were initially used for the selection of 10 cows with high TMS (HS) and 10 cows with low TMS (LS). All those animals were under the same feeding management, and the individual milk yield was recorded for 14 consecutive days before milk and rumen fluid were sampled. Rumen fluid was used to determine bacterial community by 16S rRNA gene sequencing technique. The HS cows had significantly greater feed intake and milk TMS, fat, protein content than LS cows (P < 0.05). Among the volatile fatty acids (VFA), propionic acid and valeric acid concentrations were significantly greater in HS cows than those in LS cows (P < 0.05). There was no significant difference in the concentrations of acetate, butyrate, isobutyrate, valerate, and the total VFA (P > 0.05), nor was the acetate-to-propionate ratio, pH value, ammonia nitrogen and microbial crude protein concentrations (P > 0.05). Significant differences in the relative abundances of some bacterial genera were found between HS and LS cows. Spearman’s rank correlation analysis revealed that TMS content was correlated positively with the abundances of Ruminococcaceae UCG-014, Ruminococcaceae NK4A214 group, Prevotellaceae UCG-001, Butyrivibrio 2, Prevotellaceae UCG-003, Candidatus Saccharimonas, Ruminococcus 2, Lachnospiraceae XPB1014 group, probable genus 10, Eubacterium ventriosum group, but negatively correlated with Pyramidobacte. In addition, Ruminococcaceae UCG-014, Ruminococcus 2, Ruminococcaceae UCG001, probable genus 10 and Eubacterium ventriosum group might boost the total VFA production in the rumen. In conclusion, the dry matter intake of dairy cows and some special bacteria in rumen were significantly associated with TMS content, which suggests the potential function of rumen bacteria contributing to TMS content in dairy cows.

Can flushing gas distort the rumen in vitro experiment results?

To test whether the type of flushing gas could alter rumen in vitro experimental results, effects of three flushing gases (Ar, CO2, and N2) were compared with or without hypothetic experimental treatment (monensin supplementation) in a batch culture system. Rumen fluids obtained from three cannulated Holstein heifers were incubated for 3, 6, 12, 24, and 48 h according to 3 × 2 factorial arrangements. Total gas production was decreased, and CH4 proportion was increased by CO2 flushing regardless of incubation time. The effects of monensin on CH4 proportion were not shown in CO2 flushed group. After 3 h incubation, ammonia nitrogen was increased by N2 flushing, and interaction between flushing gas and monensin was observed in iso-butyrate. Total volatile fatty acids production was not influenced by the type of flushing gases regardless of incubation time. However, after 48 h incubation, by CO2 flushing, the valerate without monensin decreased while it increased with monensin, implying the interaction effect between flushing gas and monensin. The pH elevation effect of monensin was delayed by CO2 flushing compared to Ar and N2 flushing. This study demonstrated whether the type of flushing gas can confound experimental results. Since N2 flushing can influence rumen nitrogen parameters in early incubation and CO2 flushing affected pH results while Ar flushing did not show noticeable results, we suggest that Ar could be used as a new alternative flushing gas for rumen in vitro studies.

Exploration of Methane Mitigation Efficacy Using &amp;lt;i&amp;gt;Asparagopsis&amp;lt;/i&amp;gt;-Derived Bioactives Stabilized in Edible Oil Compared to Freeze-Dried &amp;lt;i&amp;gt;Asparagopsis in Vitro&amp;lt;/i&amp;gt;

Asparagopsis oil products are of interest due to the stabilizing effects of the Asparagopsis-derived antimethanogenic bioactive compound bromoform (CHBr3). The objective of this in vitro series is to characterize antimethanogenic efficacy of freeze-dried Asparagopsis (FD-Asp) and Asparagopsis oil (Asp-Oil) and compare relative antimethanogenic response over time at multiple levels of CHBr3 delivery. Relative methane (CH4) emissions (mL/g) are based on in vitro apparent feed digested dry matter (IVDDM) after 24, 48, and 72 h of fermentation. CHBr3 contained in FD-Asp was included at 95, 191, and 286 mg/kg, and CHBr3 contained in Asp-Oil was included at 78, 117, and 175 mg/kg, to produce the Low, Mid, and High inclusions, respectively. Low FD-Asp had no significant impact on CH4 emissions, Mid FD-Asp demonstrated 91%, 44%, and 37% reductions, and the High FD-Asp demonstrated complete inhibition of CH4, after 24, 48, and 72 h of fermentation, respectively. Comparatively, Low Asp-Oil demonstrated a 46%, 28%, and 18% CH4 reduction, Mid Asp-Oil resulted in 99%, 92%, and 73% reductions, and the High Asp-Oil demonstrated complete inhibition of CH4 after 24, 48, and 72 h of fermentation, respectively. IVDDM and total volatile fatty acid (tVFA) production were not changed by the inclusion of FD-Asp and Asp-Oil. The results from this study show that Asparagopsis is not only a compelling CH4 mitigating feed supplement but is also able to be delivered in edible oil forms which will strengthen its applicability to on-farm use. This study is promising for the utility of Asp-Oil, and in vivo trials are essential to demonstrate the extent of efficacy of Asp-Oil in ruminant animals because FD-Asp has consistently demonstrated greater antimethanogenic efficacy in vivo compared to in vitro.

Porcine in vitro fermentation characteristics of canola co-products in neutral and acidic fermentation medium pH

An in vitro study was conducted to determine effects of reducing pH of porcine in vitro fermentation medium on compositions of glucosinolate degradation products and porcine in vitro fermentation characteristics for solvent-extracted canola meal (SECM) and cold-pressed canola cake (CPCC). Two canola co-products were subjected to porcine in vitro fermentation for 72 h. Accumulated gas production during microbial fermentation was recorded and modeled to estimate kinetics of gas production. Glucosinolate degradation products after microbial fermentation were determined and fermentation medium pH after incubation was recorded. Total and individual volatile fatty acids (VFA) concentrations per unit weight of dry matter (DM) of feedstuffs were determined. On DM basis, SECM and CPCC contained 6.15 and 11.1 µmol/g of glucosinolates, respectively. Goitrin concentration for CPCC was lower (P < 0.05) than that for SECM. Isothiocyanate and indole-3-acetonitrile concentrations for CPCC were lower (P < 0.05) than those for SECM, whereas thiocyanate concentration for CPCC was greater (P < 0.05) than that for SECM. A reduction in fermentation medium pH from 6.2 to 5.2 increased (P < 0.05) goitrin and indole-3-acetonitrile concentrations and decreased (P < 0.05) isothiocyanates concentration for SECM, but did not affect concentration of these 2 glucosinolate degradation products for CPCC. Fermentation medium pH after in vitro fermentation for SECM tended to be greater (P = 0.081) than that for CPCC. Canola co-product type and fermentation medium pH did not interact on gas production parameters. However, a reduction in fermentation medium pH from 6.2 to 5.2 resulted in increased (P < 0.05) lag time and reduced (P < 0.05) fractional rate of degradation and total gas production. Canola co-product type and fermentation medium pH did not interact on total or individual VFA production per gram of DM of feedstuff fermented. However, reducing fermentation medium pH from 6.2 to 5.2 increased (P < 0.05) total VFA and acetate productions, and tended to reduce (P = 0.083) branched-chain VFA production SECM and CPCC. In conclusion, a reduction in fermentation medium pH from 6.2 to 5.2 resulted in increased production of goitrin and indole-3-acetonitriles from SECM-derived glucosinolates, but did not affect production of thiocyanate from SECM-derived glucosinolates. Glucosinolates in CPCC were less affected by the fermentation medium pH used in the current study. It appears that there are other factors other than pH that affect the degradation of canola-derived glucosinolates by microorganisms from hindgut of pigs.

Effects of the higher concentrate ratio on the production performance, ruminal fermentation, and morphological structure in male cattle-yaks.

BackgroundThe present study evaluated the effects of the different concentrate‐to‐forage ratio on the parameters of production, ruminal fermentation, blood biochemical indices, and ruminal epithelial morphological structure of the male cattle‐yaks.MethodsEight male cattle‐yaks (280 ± 10 kg of body weight) were randomly divided into the high concentrate (HighC, 70% concentrate feeds on a dry matter basis) and low concentrate (LowC, 50% concentrate feeds on a dry matter basis) groups. All the animals were regularly provided rations twice a day at 08:00 and 16:00 h and had free access to water. The experiment lasted for 37 days.ResultsThe dry matter intake and average daily gain of the HighC group were higher (p < 0.05) than those of LowC group. Moreover, a high concentrate diet was found to significantly increase (p < 0.05) the total volatile fatty acid (TVFA) production, and the ratio of propionate and butyrate in TVFA. On the contrary, the ruminal pH, the ratio of isobutyrate and isovalerate, and the acetate‐to‐propionate were significantly decreased (p < 0.05) after high concentrate feeding. The lipopolysaccharide concentrations of the ruminal fluid and plasma in the HighC group were higher (p < 0.05) than those of the LowC group. The results of the ruminal histomorphology showed the rumen to possess an inflammatory reaction.ConclusionThese findings revealed that upon higher dry matter intake and average daily gain, high concentrate feeding altered the rumen fermentation and morphology, inducing the ruminal inflammation of the cattle‐yak.

Rumen Fermentative Properties of Pregnant West African Dwarf Does Fed Diets Containing Algae Biomass

The study was conducted to investigate the effect of feeding algae biomass rich in polyunsaturated fatty acids at 0%, 1.5%, 3.0% and 4.5%, respectively, using Panicum maximum as basal feed, on rumen fermentative properties of pregnant West African Dwarf (WAD) does. A total of twenty (20) pregnant WAD does were grouped into four treatments containing five (5) animals per treatment and randomly allotted to the experimental diets. Rumen fluid were collected prior to mating and at the last trimester of pregnancy for determination of rumen fermentative properties. Data obtained were subjected to one way Analysis of Variance in a Completely Randomized Design. Inclusion of algae biomass up to 4.5% had no significant (p&gt;0.05) effect on bacteria population in the rumen of the experimental does. The inclusion levels of algae biomass gave rise to the predominance of Eischeria coli (a gram negative bacterium) in the rumen of pregnant does fed the algae biomass diet. Results obtained showed a significant (p&lt;0.05) decrease in the values obtained for ammonia nitrogen concentration in the rumen of the pregnant does when compared to the values recorded prior to mating. The total volatile fatty acid production and its molar proportion in the rumen fluid were not significantly (p&gt;0.05) influenced by the inclusion of algae biomass.

Plug-flow reactor for volatile fatty acid production from the organic fraction of municipal solid waste: Influence of organic loading rate

This work experimentally assessed the production of total and specific volatile fatty acids (VFAs) by dry thermophilic anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) in a semi-continuous pilot-scale plug-flow reactor (PFR). The experimental test compared the two organic loading rates (OLR) of 7.5 and 14 gVS/(L d) for an overall duration of 150 days. The results revealed that OLR positively affects the production of total VFAs, since their overall concentration reached a maximum of 12136 mg/L with OLR of 14 gVS/(L d). In addition, the productivity increased by 150.9% and the yield increased by 49.2% compared to the lowest OLR tested. Propionate dominated during the whole experimental period ranging between 86.2% and 64.4% of total VFAs. As the OLR increased, the concentration of iso-valeric and butyric acids increased as well, accounting for 15.7% and 9.6% of total VFAs, respectively. Meanwhile, the specific biogas production (SGP) decreased from 280.8 ± 72.8–196.3 ± 24.4 NLbiogas/kgVS diminishing by 30.6%, and the oxygen uptake rate (OUR) raised from 46.4 ± 0.6–124.8 ± 10.9 mmolO2/(kgVS h) increasing by 169.1%.

PH and hydraulic retention time regulation for anaerobic fermentation: Focus on volatile fatty acids production/distribution, microbial community succession and interactive correlation

Enriching suitable fermentative products by optimizing operation conditions could effectively improve the efficiency of anaerobic digestion. In the present study, pH (5.0–6.0) and hydraulic retention time (HRT) (2 h-12 h) were regulated for volatile fatty acids (VFAs) production during glucose fermentation in acidogenic continuous stirred tank reactor (CSTR). Results showed that acetate and butyrate dominated during pH regulation. HRT reduction favored butyrate production and formate retainment. Maximum total VFAs production with highest acetate content was achieved at pH of 6.0 and HRT of 6 h. Microbial analysis revealed that Clostridium_sensu_stricto_1 was predominant butyrate producer during pH regulation, and Bacteroides was main contributor when HRT shorter than 6 h. In addition to acetyl-CoA pathway, acetate could also be produced via homoacetogenesis by Parabacteroides, UCG-004 and norank_f__Acidaminococcaceae. These results would give guidance for enhancing targeted VFAs products by optimizing operational parameters or bio-augmentation with specific bacteria.

PSXIII-2 Effect of varying proportions of cereal rye and turnip on ruminal fermentation and methane output through in vitro batch culture

Abstract Ruminant animal performance has been variable in studies grazing annual cool-season grass and brassica monocultures and mixtures. There is little understanding of the fermentation mechanisms causing variation. The aim of this study was to determine apparent dry matter (DM) digestibility, methane, and volatile fatty acid (VFA) concentration from different proportions of cereal rye (Secale cereal; R) and turnip (Brassica rapa L.; T) (0R:100T, 40R:60T, 60R:40T, and 100R:0T) via in vitro batch fermentation. Freeze-dried forage samples from an integrated crop-livestock study was assembled into the four treatments with a 50:50 leaf to root ratio for turnip. Measurements were made following a 48 hr fermentation with 2:1 buffer and ruminal fluid inoculum. Data were analyzed using Mixed Procedure of SAS with batch (replicate) and treatment (main effect) in the model; differences were declared at P ≤ 0.05, with tendencies declared at &amp;gt; 0.05 but &amp;lt; 0.10. Rumen apparent DM digestibility (26.8%; overall mean) was not different among treatments. Methane production was less (P &amp;lt; 0.01) with inclusion of turnip ranging from 774 nmol/ml for 0R:100T to 1416 nmol/ml for 100R:0T. Total VFA production, acetate to propionate ratio, acetate, and valerate were not affected by forage treatments (117 mM, 1.45, 39.84 mol/100 mol, and 7.86 mol/100 mol, respectively; overall mean). Propionate, isobutyrate, and isovalerate concentrations were greater and butyrate concentration less with greater (P &amp;lt; 0.01) proportions of rye in the mixture. No effect of R:T ratio on digestibility or total VFA production along with the observed differences in individual VFA concentration do not explain variable response in grazing animals. Additionally, methane production results indicate that grazing turnips could potentially reduce methane production and thus reduce ruminant livestock’s contribution to greenhouse gas emissions.

PSX-B-6 Effect of slow-release urea on gas production, fermentation characteristics, nutrient digestibility and microbial protein synthesis in an artificial rumen system

Abstract The objective of this study was to evaluate the effects of slow-release urea (SRU) on gas production, fermentation parameters, nutrient digestibility, and microbial protein synthesis using artificial rumen system. The experiment was a completely randomized design with four treatments and four replications of each treatment. The treatments were control diet (no SRU), control diet supplemented with 0.28% (U28), 0.56% SRU (U56) or control diet that was added by 1.5% more corn grain and substituted with 0.35% SRU for 1.85% soybean meal (U35-SBM). The diets were formulated to be isoenergetic (1.71 NEL Mcal/kg), but protein concentration was lower (15.48 vs. 16.24%) and starch concentration was higher (28.2 vs. 27.1%) with U35-SBM than other three treatments. Experimental period consisted of 8 d of adaptation and 7 d of sampling. Rumen inoculum was obtained from three ruminally fistulated Angus cows fed the same diet to the substrate incubated. Gas production (L/d) was lower (P = 0.02) with U35-SBM (1.51) than control (1.79) or U28 (1.92); however, methane production was not affected by treatments (average, 47 mg/d). Dry matter digestibility was greater (P &amp;lt; 0.01) with U35-SBM (78.5%) than other treatments (74.6%), which had no differences in DM digestibility. Total volatile fatty acid (VFA) production did not differ among treatments (average, 53.1 mmol/d), but increasing SRU supplementation linearly (P &amp;lt; 0.01) decreased molar proportion of propionate from 27.0 to 25.7% and linearly (P &amp;lt; 0.01) increased acetate to propionate ratio from 1.69 to 1.78. The ammonia nitrogen (N) linearly (P &amp;lt; 0.01) increased from 7.70 to 10.25 mmol/L with increasing SRU addition. Microbial protein synthesis was greater (P = 0.03) with SRU treatments (average, 83.9 mg N/d) than control (78.9 mg N/d). The present results demonstrated the benefits to add the SRU in dairy cow diet for improving ruminal digestibility and microbial protein synthesis.

Effects of Betaine-Biotin-Chromium Supplementation and Concentrate to Roughage Ratio on Nutrient Utilization Efficiency in Thai Native Cattle

Simple SummaryFeed additives are attracting considerable interest due to the need to effectively improve the level of production, efficiency, and health of animals. A combination of betaine, biotin, and chromium has been developed to enhance nutrient utilization efficiency. Ideally, the addition of a combination of supplements to livestock feed could improve ruminal fermentation, digestibility and nutrient utilization, nitrogen and energy balance, and metabolism.The objective of this study was to evaluate the effects of supplementation with a feed additive containing a combination of betaine, biotin, and chromium (BBC) and concentrate-to-roughage ratio (C:R ratio) on nutrient digestibility, blood metabolites, ruminal fermentation, nitrogen balance, and energy utilization in Thai native beef cattle. Five Thai feedlot native beef bulls at one year old of age and 87.6 ± 15.7 kg of body weight were assigned in a (2 × 2) + 1 augmented factorial experiment according to a 5 × 5 Latin square design with five periods of 21 days. The two levels of BBC were 3 g/kg DM and 6 g/kg DM, and the two ratios of C:R were 60C:40R and 70C:30R. A C:R ratio of 70C:30R without BBC supplementation was used as a negative control. The cattle were offered feed at 3% BW, which provides sufficient energy and protein to support a weight gain of 500 g/day. The results showed that dry matter intake (DMI) and organic matter intake (OMI) were not different (p > 0.05), but the intake of crude protein (CP) and ether extract (EE) was higher (p < 0.05), whereas neutral detergent fiber (NDF) and acid detergent fiber (ADF) were lower (p < 0.05) in the 70C:30R ratio diets compared to the 60:40R ratio diets. Energy balance and nitrogen balance were not influenced (p > 0.05) by the C:R ratio or the addition of BBC. Rumen pH and ammonia-nitrogen (NH3-N) did not differ (p > 0.05) among treatments groups. Total volatile fatty acid (VFA) production was higher (p < 0.05) in bulls fed with the 70C:30R ratio diet. The addition of BBC resulted in a lower (p < 0.01) glucose-to-insulin ratio compared to cattle fed with the control diet. Energy and protein utilization efficiency did not differ (p > 0.05) among the experimental treatment groups, which were higher (p > 0.05) than the control group. In conclusion, BBC supplementation showed greater growth performance of cattle compared to the control. BBC supplementation appeared to improve glucose uptake and insulin sensitivity and energy and protein utilization efficiency. Whether BBC supplementation increases glucose production in the liver remains to be determined in future studies.

Bioaugmented Mixed Culture by Clostridium aceticum to Manipulate Volatile Fatty Acids Composition From the Fermentation of Cheese Production Wastewater.

Production of targeted volatile fatty acid (VFA) composition by fermentation is a promising approach for upstream and post-stream VFA applications. In the current study, the bioaugmented mixed microbial culture by Clostridium aceticum was used to produce an acetic acid dominant VFA mixture. For this purpose, anaerobic sequencing batch reactors (bioaugmented and control) were operated under pH 10 and fed by cheese processing wastewater. The efficiency and stability of the bioaugmentation strategy were monitored using the production and composition of VFA, the quantity of C. aceticum (by qPCR), and bacterial community profile (16S rRNA Illumina Sequencing). The bioaugmented mixed culture significantly increased acetic acid concentration in the VFA mixture (from 1170 ± 18 to 122 ± 9 mgCOD/L) compared to the control reactor. Furthermore, the total VFA production (from 1254 ± 11 to 5493 ± 36 mgCOD/L) was also enhanced. Nevertheless, the bioaugmentation could not shift the propionic acid dominancy in the VFA mixture. The most significant effect of bioaugmentation on the bacterial community profile was seen in the relative abundance of the Thermoanaerobacterales Family III. Incertae sedis, its relative abundance increased simultaneously with the gene copy number of C. aceticum during bioaugmentation. These results suggest that there might be a syntropy between species of Thermoanaerobacterales Family III. Incertae sedis and C. aceticum. The cycle analysis showed that 6 h (instead of 24 h) was adequate retention time to achieve the same acetic acid and total VFA production efficiency. Biobased acetic acid production is widely applicable and economically competitive with petroleum-based production, and this study has the potential to enable a new approach as produced acetic acid dominant VFA can replace external carbon sources for different processes (such as denitrification) in WWTPs. In this way, the higher treatment efficiency for WWTPs can be obtained by recovered substrate from the waste streams that promote a circular economy approach.

Acidogenic biorefinery of rice straw for volatile fatty acids production via sequential two-stage fermentation: Effects of pre-treatments

The physical and chemical effects of the hydrothermal, acid and alkali pretreatment methods of rice straw were investigated to be used in volatile fatty acids (VFAs) production through two-stage anaerobic fermentation. The effects of two-stage acid production and fermentation process parameters of different pretreated straws under the fermentation temperature conditions of 35°C, 55°C, and 70°C were analyzed. The results showed that The hydrothermal, 2% HCl, and 1% Ca(OH)2 increased the specific surface area of the rice straw by 12.20%, 52.62% and 37.81%, respectively. The alkali pretreatment increased the macro and mesopores of the rice straw while the hydrothermal and acid pretreatments increased the small and micropores. The primary fermentation did not affect significantly the infrared spectrum peaks of pretreated rice straw. The rate and total VFAs production was enhanced significantly after the 1% Ca(OH)2 pretreatment compared with 2%HCl and hydrothermal pretreatments respectively. Based on the initial mass of 100 g raw straw, when pretreated with 1% Ca(OH)2 and fermented at 35°C, the primary and the secondary acid production were 12.23 g and 16.54 g, respectively, and the total acid production was 28.77 g. This study provides an optimum condition for the best pretreatment and process parameters for acidogenic biorefinery of rice straw for enhanced VFAs production.

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.

Dose-Response Effects of 3-Nitrooxypropanol Combined with Low- and High-Concentrate Feed Proportions in the Dairy Cow Ration on Fermentation Parameters in a Rumen Simulation Technique.

Simple SummaryFeeding strategies which aim at mitigating ruminal methane formation, a significant contributor to total greenhouse gas emissions, are being continuously developed, yet they need to be investigated in relation to their effectiveness and the mechanisms behind their effects in vitro before they undergo further assessment in vivo. In this context, the present study investigated the dose–response relationships of the methane inhibitor 3-nitrooxypropanol supplemented to varying concentrate feed proportions in a rumen simulation technique. Methane production was effectively reduced with an increasing dose of 3-nitrooxypropanol, which was, however, independent of concentrate feed proportion. Total gas production and fibre degradability were not affected by 3-nitrooxypropanol, indicating no negative side effects on fermentative capability. However, the hydrogen-liberating acetate production was reduced, whilst hydrogen gas was notably increased in a dose-dependent manner. The present in vitro study provides a deeper insight into a combined (3-nitrooxypropanol and high-concentrate feed proportions) methane abatement strategy under controlled conditions. The present combined approach reveals neither negative side effects nor additive effects between 3-nitrooxypropanol and varying concentrate feed proportions, which should be further investigated in future experiments in vivo.Methane (CH4) from ruminal feed degradation is a major pollutant from ruminant livestock, which calls for mitigation strategies. The purpose of the present 4 × 2 factorial arrangement was to investigate the dose–response relationships between four doses of the CH4 inhibitor 3-nitrooxypropanol (3-NOP) and potential synergistic effects with low (LC) or high (HC) concentrate feed proportions (CFP) on CH4 reduction as both mitigation approaches differ in their mode of action (direct 3-NOP vs. indirect CFP effects). Diet substrates and 3-NOP were incubated in a rumen simulation technique to measure the concentration and production of volatile fatty acids (VFA), fermentation gases as well as substrate disappearance. Negative side effects on fermentation regarding total VFA and gas production as well as nutrient degradability were observed for neither CFP nor 3-NOP. CH4 production decreased from 10% up to 97% in a dose-dependent manner with increasing 3-NOP inclusion rate (dose: p < 0.001) but irrespective of CFP (CFP × dose: p = 0.094). Hydrogen gas accumulated correspondingly with increased 3-NOP dose (dose: p < 0.001). In vitro pH (p = 0.019) and redox potential (p = 0.066) varied by CFP, whereas the latter fluctuated with 3-NOP dose (p = 0.01). Acetate and iso-butyrate (mol %) decreased with 3-NOP dose, whereas iso-valerate increased (dose: p < 0.001). Propionate and valerate varied inconsistently due to 3-NOP supplementation. The feed additive 3-NOP was proven to be a dose-dependent yet effective CH4 inhibitor under conditions in vitro. The observed lack of additivity of increased CFP on the CH4 inhibition potential of 3-NOP needs to be verified in future research testing further diet types both in vitro and in vivo.

Urea treatment of rice straw: A modelling approach of its degradation kinetics in the rumen

This study aimed to compare between rice straw and urea-treated rice straw with regard to their chemical composition and degradation kinetics in the rumen by employing a modelling approach. Data were collected from various journal articles that comprised of chemical composition (crude protein [CP], neutral detergent fiber [NDF], acid detergent fiber [ADF] and lignin) and degradation kinetic parameters of organic matter (soluble fraction, degradable, undegradable, degradation rate and lag time). Comparison was performed by using a statistical mixed model methodology in which treatments (control vs urea-treated rice traw) were considered as fixed effects whereas different studies were considered as random effects. These data were then used as parameters to build a dynamic model of rice straw degradation in the rumen. Results showed that urea treatment increased CP (P<0.001) while decreased NDF (P<0.01) contents of rice straw. The ADF and lignin contents were similar between the control and urea-treated rice straw. Proportion of degradable fraction and degradation rate of rice straw were enhanced due to urea treatment (P<0.001). However, the treatment did not influence soluble fraction and lag time of the material. Microbial biomass and total volatile fatty acid production in the rumen changed dynamically over time and the values were higher for the urea-treated rice straw.

Aspergillus oryzae and Aspergillus niger Co-Cultivation Extract Affects In Vitro Degradation, Fermentation Characteristics, and Bacterial Composition in a Diet-Specific Manner.

Simple SummaryThe rumen is a large fermentation chamber that enables dairy cows to utilize otherwise indigestible plant polymers and compounds for their nutrition, highlighting a crucial difference between ruminants and monogastrics. The key point in this process is the pool of enzymes secreted by microorganisms. Hence, exogenous enzymes from additives are important for high-production dairy cows to improve the utilization of feeds. In this study, we used the Aspergillus oryzae and Aspergillus niger co-cultivation extract (AOAN) to improve the digestibility of roughage and total mixed ration in vitro. Our results indicated that the digestibility of nutrients in feeds was significantly increased by AOAN supplementation, except for the digestibility of crude protein in the total mixed ratio (TMR). Furthermore, the diversity of the bacteria in TMR and oat hay was increased with AOAN supplementation. Although broad effectiveness of AOAN was established, regardless of roughage types, the mechanism may be different according to roughage types.AOAN may provide enzymes to improve the digestibility of feeds and enhance rumen fermentation. This study determined the effects of AOAN on digestibility, fermentation characteristics, and bacterial composition using in vitro gas recording fermentation system. A total of 30 mg of AOAN was supplemented into 500 mg of TMR, corn silage, oat hay, and alfalfa hay. Fermentation parameters and bacterial communities were determined after 48 h fermentation, and digestibility was determined after 7, 24, 30, and 48 h fermentation. Gas production and dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) digestibility were significantly increased by AOAN supplementation at 48 h (p < 0.05), except for digestibility of CP of the TMR (p > 0.05). AOAN increased starch digestibility in corn silage (p < 0.05) and tended to increase that in TMR (0.05 < p < 0.10). AOAN supplementation increased total volatile fatty acid production (p < 0.05). The molar proportions of acetate and acetate to propionate ratio of oat hay and alfalfa hay were increased (p < 0.05). The 16S rRNA analysis revealed that the microbial richness of TMR and oat hay, and microbial evenness of TMR were increased (p < 0.05). AOAN did not affect the α diversity, β diversity, and bacterial composition of the corn silage. The relative abundance of Prevotella was increased and Ruminococcus was decreased in TMR, oat hay, and alfalfa hay. In conclusion, results suggest that AOAN has the potential to improve the utilization of diets differently, including providing enzymes with changing microbiota (TMR, oat hay, and alfalfa hay) or providing enzymes alone (corn silage).