A fully automated incubation system for the measurement of gas production and gas composition

Assessing the efficacy of date-pits holocellulose as a novel additive candidate for ruminant feeding

Holocellulose (HC) fraction extracted from date-pits was evaluated as a novel feed additive for ruminant feeding. This study was performed to investigate the effectiveness of the HC additive on rumen fermentation, methane (CH4) production, and diet degradability over 24 h of in vitro incubation. Three independent incubation trials were conducted over three consecutive weeks, employing the same in vitro methodology to assess four treatment doses in a completely randomized design. The experimental diet incorporated four increasing doses of HC, containing HC at 0 (HC0), 10 (HC10), 20 (HC20), and 30 (HC30) g/kg dry matter (DM). In vitro gas production (GP) and CH4 production, volatile fatty acids (VFAs) concentration, protozoa accounts, degraded organic matter (DOM), metabolizable and net energy (ME and NE), and hydrogen (H2) estimates were measured. No significant differences in ruminal pH were observed as the HC doses gradually increased. All incremental doses of HC additive over 24 h resulted in a linear increase in GP (P < 0.001), DOM (P < 0.001), total VFAs (P = 0.011), and propionate (P < 0.001) concentrations, as well as estimated energy (ME and NE) (P < 0.05) and microbial protein (P = 0.017) values. However, the inclusion of increasing doses of HC in the diet displayed linear reductions in the net CH4 production (ml/kg DOM; P = 0.002), protozoa abundance (P = 0.027); acetate (P = 0.029), and butyrate (P < 0.001) concentrations, the acetate-to-propionate ratio (P < 0.001), and the estimated net H2 production concentration (P = 0.049). Thus, the use of date-pits HC additive generated positive ruminal fermentability, including increased total VFAs and a reduction in the acetate-to-propionate ratio, leading to decreased CH4 output over 24 h of in vitro incubation. Hence, HC could be considered a potent feed additive (at up to 30 g/kg DM), demonstrating promising CH4-mitigating competency and thereby enhancing energy-use efficiency in ruminants.

Effect of buffer pH on methane production and fermentation characteristics of three forages tested in vitro

BACKGROUND

Low rumen pH is proposed to be a major mechanism for low methane (CH4) emissions from sheep fed forage rape. However, it is difficult to separate this from other in vivo factors, such as rumen passage rate. The objective of this study was to determine the effect of pH alone on CH4 production in vitro using different pH buffers. Ryegrass, white clover and forage rape were incubated in vitro using three different incubation buffers with starting pH values of 5.5, 6.2 and 6.8.

RESULTS

Decreasing pH reduced overall in vitro CH4 emission relative to fermented hexoses (CH4/FHex) by up to 54% and overall fermentation by 40%. pH also changed fermentation profiles where the acetate + butyrate to propionate + valerate ratio decreased when pH decreased. Within the three forages, forage rape led to the lowest CH4/FHex, but only in pH 5.5 and 6.2 buffer, and this was enhanced when the pH fell below 6.

CONCLUSION

Reducing pH in vitro decreased CH4 production and overall fermentation across all forages. The lower pH reached by forage rape compared to ryegrass and white clover appears to drive the lower CH4 production relative to the extent of fermentation from forage rape compared to the other forages. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Differences in Donor Animal Production Stage Affect Repeatability of In Vitro Rumen Fermentation Kinetics

In vitro gas production techniques (IVGPT) are widely used to screen feeds and feed additives to reduce the number of animals needed for experiments, which in turn, reduces costs and increases animal welfare. However, information about repeatability is scarce. The objective of this study was to evaluate the variation from in vitro gas production fermentations in the same laboratory using the same feed substrate. The source of rumen fluid used in the fermentations was from two different farms with either cannulated lactating dairy cows or cannulated fasting heifers, representing two distinct stages of production (donor types). Seventeen 24 h fermentations, undertaken during a year, were used to evaluate the variation between the following parameters: gas curve parameters, baseline-corrected total gas production (TGP (mL at Standard Temperature and Pressure (STP))/g incubated dry matter (DM)), methane concentration (%) and yield (mL gas at STP/g DM), pH and degraded dry matter (dDM). Significant differences between donor types were found for the pH of the rumen fluid from individual animals and pH of fermented fluid. However, no significant differences were observed within donor type. The means for methane concentration and yield, after 24 h of fermentation, were not significantly different between or within donor types. Rate of early gas production was significantly different between donor types, but baseline-corrected TGP was not significantly different at 24 h. No dDM differences after 24 h of fermentation between or within donor types were detected. Gas production curves were different between donor types, being either a monophasic version of the sigmoidal model or an exponential curve for the heifers and the production animals, respectively. No differences were observed within type. Repeatability of rumen fluid (CVRF), calculated as the coefficient of variation, and the associated parameters, which were investigated, was best for methane yield (CVRFALL = 0.3%) and least for TGP at 3 h (CVRFALL = 3%). Repeatability was dependent on donor type.

In vitro rumen fermentation pattern: insights from concentrate level and plant oil supplement

The addition of oil to ruminant diets and oil fatty acid profiles are major factors that negatively affect ruminal fermentation, while increased forage level attenuates the adverse effects. The aim of this study was to determine the effects of oil source supplementation and concentrate level in the diet on in vitro ruminal fermentation kinetics. Pomegranate, garlic or sunflower oils were added (2 % dry matter (DM) basis) to the diets containing 40 % or 60 % (DM basis) concentrates. In vitro gas production parameters, pH, ammonia nitrogen concentration and total protozoa count were measured. Additionally, metabolizable energy (ME), short-chain fatty acid (SCFA) production and organic matter digestibility (OMD) were determined. Rumen fermentation parameters and protozoal population counts were analyzed as a completely randomized design with a 2  ×  3 factorial arrangement of treatments, and gas production parameters were analyzed as a 2  ×  3 factorial arrangement in a randomized block design. The results showed that the HCPO (high (60 %) concentrate diet containing pomegranate oil) and HCSO (high (60 %) concentrate diet containing sunflower oil) diets produced the highest (5.40 mg dL - 1 ) and lowest (2.61 mg dL - 1 ) concentrations of NH 3 -N ( p > 0.01 ), respectively. Total protozoa count tended ( p = 0.07 ) to be highest in HCPO and lowest in HCSO diets (5.10 vs. 4.81 Log 10 g - 1 digesta). No interaction effects between the concentrate level and oil source were found on in vitro gas production parameters, pH, estimated ME, SCFA and OMD, and Entodinium and Diplodinium populations ( p > 0.05 ). It is concluded that dietary supplementation with highly unsaturated oil from three different sources at 2 % level (DM basis) had no apparent effects on in vitro ruminal fermentation patterns.

A new equipment for continuous measurement of methane production in a batch in vitro rumen system

A new rumen batch fermentation system that allows continuous measures of total gas (GP) and methane production (MP) was tested. The fermentation system is composed of glass bottles connected to gas counters (Ritter Apparatebau GmbH & Co. KG) and an infrared gas analyser that measures the methane concentration. The system allows direct and continuous measurement of GP and MP for accurate kinetic studies. The aim of the work was to test the rumen fermentation system and compare the GP and MP kinetics obtained. Barley meal (BM), alfalfa hay (AH), corn silage (CS), and soya bean hulls (SH) were used as substrates in four consecutive fermentation runs. Cumulative volumes of GP and MP and the percentage of methane on total GP were recorded continuously until 48 h and average values at 1 h intervals were fitted with an exponential model with a lag phase reaching a good fit (R²  > 0.992). GP and MP reached the highest plateau levels for SH (1836 and 370 ml, respectively; p < 0.01) and the lowest for AH (1000 and 233 ml, respectively). The remaining substrates showed intermediate values. MP kinetics showed a discrete lag phase (from 0.09 to 1.12 h), whereas it was equal to zero for the total GP (except for SH). The methane concentration in gas flowing increased rapidly at the beginning of fermentation (from 0.35 to 0.95 h^-1 ) and reached a plateau after approximately 8-12 h. In conclusion, the rumen fermentation system evaluated generates methane data comparable to those reported in the literature and allows simple continuous measurement of methane release throughout fermentation.

Effect of feeding fresh forage plantain (Plantago lanceolata) or ryegrass-based pasture on methane emissions, total-tract digestibility, and rumen fermentation of nonlactating dairy cows

Plantain (Plantago lanceolata) is an herb used to reduce the forage deficit of ryegrass-based pastures during the summer. This herb is being promoted for its reduced environmental impact in terms of nitrogen emissions, particularly reducing urinary nitrogen. However, the effect of plantain on emissions of enteric CH₄, the main greenhouse gas produced from ruminant-based production systems, is not known. The aim of the present trial was to determine CH₄ emissions and rumen fermentation characteristics of nonlactating dairy cows fed 100% plantain (PLT) or 100% perennial ryegrass (RG; Lolium perenne) in 2 experiments (E1 and E2). The forages were in a vegetative growth stage in E1 and were in a reproductive growth stage in E2. Methane emissions from 16 cows in each experiment were measured in respiration chambers for 2 d. Methane emissions per unit of dry matter intake (CH₄ yield) were 15 and 28% less for cows fed PLT than those fed RG in E1 and E2, respectively. Dry matter digestibility of PLT was 7 and 27% less than that of RG in E1 and E2, respectively, and CH₄ per unit of dry matter digested was similar for PLT and RG in both experiments. There were only minor (but some significant) differences in rumen fermentation characteristics between cows fed PLT and RG in both experiments. In conclusion, CH₄ yield was lower for cows fed PLT compared with those fed RG in both experiments and this reduction was largely explained by the lesser dry matter digestibility of PLT.

Tailored Nanoparticles With the Potential to Reduce Ruminant Methane Emissions

Agricultural methane produced by archaea in the forestomach of ruminants is a key contributor to rising levels of greenhouse gases leading to climate change. Functionalized biological polyhydroxybutyrate (PHB) nanoparticles offer a new concept for the reduction of enteric methane emissions by inhibiting rumen methanogens. Nanoparticles were functionalized in vivo with an archaeal virus lytic enzyme, PeiR, active against a range of rumen Methanobrevibacter species. The impact of functionalized nanoparticles against rumen methanogens was demonstrated in pure cultures, in rumen batch and continuous flow rumen models yielding methane reduction of up to 15% over 11 days in the most complex system. We further present evidence of biological nanoparticle fermentation in a rumen environment. Elevated levels of short-chain fatty acids essential to ruminant nutrition were recorded, giving rise to a promising new strategy combining methane mitigation with a possible increase in animal productivity.

Technical note: design, development and validation of an automated gas monitoring equipment for measurement of the dynamics of microbial fermentation

The present technical note describes design, development and validation of an automated equipment for measurement of kinetics of gas production during fermentation in glass bottles. The overall repeatability and precision of the developed system was evaluated and compared with the manual gas measurement technique in respect to characterization of the fermentation kinetics of ruminant livestock feeds. Two incubations were carried out, during which the GP of six different feeds was measured with the automated system or manual technique. During a 48-hour incubation period, pressure data were collected at 15-minute intervals using automated equipment, yielding 192 head-space pressure measurements for each bottle. In manual measurement, incubations were performed with the nominal 60-mL serum bottle, and headspace pressure was read using a digital pressure gauge and then released at 2, 4, 6, 8, 12, 16, 24, 36, and 48 hours of incubation. The automated equipment recorded greater GP (+11.5%, over the 48-h incubation) than the manual measurement, and the repeatability and coefficient of repeatability values indicated that the GP data obtained with manual equipment were less repeatable. The automated equipment measures the fermentative GP kinetics with greater precision and repeatability than manual technique.•

An automated batch GP equipment was designed, developed and validated, and a comparison was made with GP data obtained manually using a digital pressure gauge.

•

The automated equipment provided more reliable and repeatable data compared with manual measurement.

•

The automated equipment is available with lower cost and more functionality.

Condensed Tannins in White Clover (Trifolium repens) Foliar Tissues Expressing the Transcription Factor TaMYB14-1 Bind to Forage Protein and Reduce Ammonia and Methane Emissions in vitro

Grazing ruminants contribute to global climate change through enteric methane and nitrous oxide emissions. However, animal consumption of the plant polyphenolics, proanthocyanidins, or condensed tannins (CTs) can decrease both methane emissions and urine nitrogen levels, leading to reduced nitrous oxide emissions, and concomitantly increase animal health and production. CTs are largely absent in the foliage of important temperate pasture legumes, such as white clover (Trifolium repens), but found in flowers and seed coats. Attempts at enhancing levels of CT expression in white clover leaves by mutagenesis and breeding have not been successful. However, the transformation of white clover with the TaMYB14-1 transcription factor from Trifolium arvense has resulted in the production of CTs in leaves up to 1.2% of dry matter (DM). In this study, two generations of breeding elevated foliar CTs to >2% of DM. The CTs consisted predominantly of prodelphinidins (PD, 75-93%) and procyanidins (PC, 17-25%) and had a mean degree of polymerization (mDP) of approximately 10 flavan-3-ol subunits. In vitro studies showed that foliar CTs were bound to bovine serum albumin and white clover proteins at pH 6.5 and were released at pH 2.-2.5. Using rumen in vitro assays, white clover leaves containing soluble CTs of 1.6-2.4% of DM significantly reduced methane production by 19% (p ≤0.01) and ammonia production by 60% (p ≤ 0.01) relative to non-transformed wild type (WT) controls after 6 h of incubation. These results provide valuable information for further studies using CT expressing white clover leaves for bloat prevention and reduced greenhouse gas emissions in vivo.

Milk production responses and rumen fermentation of dairy cows supplemented with summer brassicas

Forage brassicas, such as summer turnip (ST; Brassica rapa) and forage rape (FR; Brassica napus), are used as supplementary crops during summer. However, studies with lactating dairy cows fed these forages are limited and report inconsistent productive responses. The aim of this study was to determine dry matter intake, rumen fermentation and milk production responses of dairy cows in mid-lactation supplemented with and without summer ('ST' or 'FR') brassicas. Twelve multiparous lactating dairy cows were randomly allocated to three dietary treatments in a replicated 3 × 3 Latin square design balanced for residual effects over three 21-day periods. The control diet consisted of 16.2 kg DM of grass silage, 2.25 kg DM of commercial concentrate and 2.25 kg DM solvent-extracted soybean meal. For the other two dietary treatments, 25% of the amounts of silage and concentrates were replaced with FR or ST. The inclusion of forage brassicas had no effects on milk production (24.2 kg cow/day average) and composition (average milk fat and protein 43.2 and 33.6 g/l, respectively). Dry matter intake was 0.98 kg and 1.12 kg lower for cows supplemented with FR and ST, respectively, resulting in a greater feed conversion efficiency (1.35 kg milk/kg DM for ST and FR v. 1.27 kg milk/kg DM for the control diet). Intraruminal pH was lower for cows supplemented with ST compared to the control diet; however, it did not decrease below pH 5.8 at any time of the day. After feeding, the concentrations of total short-chain fatty acids (SCFAs) in rumen contents increased with ST supplementation compared to the control diet. Inclusion of FR in the diet increased the molar proportion of acetate (68.5 mmol/100 mmol) in total SCFA at the expense of propionate, measured 6 h after feeding of the forage. The molar proportion of butyric acid was greater with ST and FR supplementation (13.1 and 12 mmol/100 mmol, respectively) than in control cows. The estimated microbial nitrogen (N) flow was 89.1 g/day greater when supplementing FR compared to the control diet. Based on the haematological measures, the inclusion of summer brassica forages did not affect the health status of the animals. These results indicate that mid-lactation dairy cows fed brassicas are able to maintain production despite the reduced intake, probably due to improved rumen fermentation and therefore nutrient utilization.

Effects of nitrogen gas flushing in comparison with argon on rumen fermentation characteristics in in vitro studies

In rumen in vitro experiments, although nitrogen gas (N2) flushing has been widely used, its effects on rumen fermentation characteristics are not clearly determined. The present study is the first to evaluate the effects of N2 flushing on rumen fermentation characteristics in in vitro batch culture system by comparing with new applicable non-metabolizable gas: argon (Ar). The rumen fluid was taken from two Korean native heifers followed by incubation for 3, 9, 12, and 24 h with N2 or Ar flushing. As a result, in all incubation time, N2 flushing resulted in higher total gas production than Ar flushing (p < 0.01). Additionally, in N2 flushing group, ammonia nitrogen was increased (p < 0.01). However, volatile fatty acids profiles and pH were not affected by the flushing gases (p > 0.05). In conclusion, the present study demonstrated that N2 flushing can influence the rumen nitrogen metabolism via increased ammonia nitrogen concentration and Ar flushing can be used as a new alternative flushing gas.

The effect of diet of the donor cows on in vitro measurements of methane production from wheat and corn incubated in various forage-to-grain ratios

BACKGROUND

Supplementation of ruminant diets with wheat and corn grains influences ruminal fermentation. In vitro fermentation is a methodology that can be used to screen feeds for their potential to produce enteric methane. However, there is evidence that the diet of the donor cows could impact the results of in vitro analysis. This research investigated the in vitro fermentation of wheat and corn grain when incubated in ruminal fluid from cows fed different grain types and different forage-to-grain ratios.

RESULTS

The type of grain fed to the donor cows, as well as forage-to-grain ratio, affected the outcome of fermentation of wheat and corn grain. Differences in methane production (MP) between grains were only observed when incubated with ruminal fluid adapted to each specific grain type. Increasing proportions of wheat but not of corn decreased in vitro MP in a linear manner compared with MP produced from forage only.

CONCLUSIONS

Wheat grain has a greater in vitro antimethanogenic effect than corn. However, to detect the different fermentations between wheat and corn, grains should be incubated in ruminal fluid from cows adapted to that specific grain type. © 2019 Society of Chemical Industry.

Comparison of five methods for the estimation of methane production from vented in vitro systems

BACKGROUND

There are several methods for estimating methane production (MP) from feedstuffs in vented in vitro systems. One method (A; 'gold standard') measures methane proportions in the incubation bottle's headspace (HS) and in the vented gas collected in gas bags. Four other methods (B, C, D and E) measure methane proportion in a single gas sample from the HS. Method B assumes the same methane proportion in the vented gas as in the HS, method C assumes constant methane to carbon dioxide ratio, method D has been developed based on empirical data, and method E assumes constant individual venting volumes. This study aimed to compare the MP predictions from these methods to that of the gold standard method under different incubation scenarios, to validate these methods based on their concordance with a gold-standard method.

RESULTS

Methods C, D and E had greater concordance (0.85, 0.88 and 0.81), lower root-mean-square error (RMSE; 0.80, 0.72 and 0.85) and lower mean bias (0.20, 0.35, -0.35) with the gold standard than did method B (concordance 0.67, RMSE 1.49 and mean bias 1.26). Methods D and E were simpler to perform than method C, and method D was slightly more accurate than method E.

CONCLUSION

Based on precision, accuracy and simplicity of implementation, it is recommended that, when method A cannot be used, methods D and E are preferred to estimate MP from vented in vitro systems. © 2018 Society of Chemical Industry.

In vitro fermentation and in situ rumen degradation kinetics of summer forage brassica plants

The aim of the present study was to assess and compare the nutrient concentration, the in vitro fermentation and the in situ rumen degradation characteristics of Brassica rapa ssp. rapa L. (turnips) and Brassica napus ssp. biennis L. (forage rape). Five varieties of each species were established in three field replicates and were organised in a randomised complete-block nested design. All varieties were harvested and further analysed for chemical composition, in vitro gas-production kinetics, volatile fatty acid (VFA) production and in situ degradation kinetics of dry matter (DM) and crude protein. Turnips showed higher ash, total sugars, raffinose, sucrose, glucose and fructose concentrations (P &lt; 0.001) than did forage rape. Turnip varieties differed in their sucrose, glucose, fructose and total soluble sugar concentration (P &lt; 0.001), whereas rape varieties differed in their neutral detergent fibre concentration (P = 0.004) and digestible organic matter on a DM basis (P &lt; 0.01). Regarding DM-degradation parameters, turnips had a higher soluble fraction ‘a’ (P &lt; 0.01) and a lower insoluble, but potentially degradable fraction ‘b’ (P &lt; 0.01) than did rape, but the fractional degradation rate ‘c’ (0.18/h) was similar to that of rape. Rates of gas production were slightly higher (P = 0.018) for turnip than for rape. No effects for brassica species nor for varieties within species were detected (P &gt; 0.05) for total in vitro VFA production, as well as for the relative proportions of acetate, propionate, butyrate, branch chained VFA and the actetate:propionate ratio. Our study showed that most of the differences that were observed in terms of chemical composition and degradation kinetics did not result in differences in in vitro fermentation products.

Evaluation of sources of variation on in vitro fermentation kinetics of feedstuffs in a gas production system

The aim of this study was to evaluate the effect of different sources of variation in gas production technique on the in vitro gas production kinetics of feedstuffs. Triplicates of commercial concentrate, grass silage, grass hay and grass pasture were incubated in three experiments: experiment 1 assessed two agitation methods; experiment 2 evaluated different rumen inocula (pooled or different donor cows for each incubation run); and experiment 3 used Goering-Van Soest or Mould buffers for media preparation. Gas production data were fitted into the Michaelis-Menten model and then subjected to analysis of variance. Gas production (GP) at 48 h and asymptote gas production (A) were lower when bottles were continuously under horizontal movement. Time to produce half and 75% of A, and A were affected by rumen inocula, while buffer type affected time to produce half and 25% of A and GP. No interactions between substrates and sources of variation were observed, suggesting that the effects of substrates on GP parameters were not modified. It is concluded that comparison of numerical data from in vitro experiments that follow different protocols must be done carefully. However, the ranking of different substrates is more robust and less affected by the sources of variation.

Comparison of rumen in vitro fermentation of temperate pastures using different batch culture systems

In vitro batch culture systems are popular because they are relatively inexpensive and allow the screening and testing of large amounts of samples in a short time. Most of the batch culture systems have been designed for the evaluation of gas produced during fermentation of substrates and different designs have been compared between laboratories, but very little work is published where methane production or volatile fatty acid production is compared. The aim of this study was to determine the degree of agreement between two different in vitro batch culture systems, from different laboratories when measuring in vitro fermentation kinetics and end products using pasture samples as substrates. The two systems were a manual and a fully automated pressure-based system. Duplicates of pasture samples were incubated in three consecutive runs. Concordance correlation coefficients between systems and estimates of variance components (pasture, incubation run and random error) for each system were determined for all measured variables. There were poor correlations between systems for most of the variables except for time to produce half of the asymptotic gas production and acetate molar proportion of volatile fatty acids. However, for both systems most of variance was due to pasture sample and then incubation run. The poor agreement between systems might be explained by the different laboratory protocols. Therefore, comparisons of absolute values from different batch culture systems or experiments must be done carefully. Alternatively, more standardisation in terms of sample preparation and incubation procedure may be needed to compare in vitro fermentation products among systems.

Dose-response effect of nitrate on hydrogen distribution between rumen fermentation end products: an in vitro approach

The objective of this work was to study the in vitro dose-response effect of nitrate (0, 1, 2, 4 and 6 mM) on metabolic hydrogen distribution between rumen fermentation end products. Three 48-h incubations were conducted using bovine rumen contents as an inoculum, and a mixture of hay and concentrate (50 : 50) as a substrate. Total gas production and composition (methane and hydrogen) were automatically analysed throughout the incubations. Volatile fatty acid and ammonium concentrations were analysed from samples taken after 48 h of incubation. Total gas production was decreased with the highest dose of nitrate (P = 0.002). Methane emissions linearly decreased as the nitrate dose increased (P = 0.005). Kinetics of methane emissions showed that metabolic hydrogen removal via nitrate reduction occurred mainly during the first 10 h of incubation. Gaseous hydrogen production was similar among treatments, despite higher hydrogen emissions for nitrate concentrations >4 mM. Concentrations and proportions of volatile fatty acids were not affected by treatments. The proportion of unaccounted metabolic hydrogen was positive for all treatments, and tended to linearly increase as the nitrate dose increased. In this in vitro work, we confirmed that nitrate is an efficient methane-mitigating compound in the rumen. We also suggest that nitrate or its reduced forms have a direct inhibiting effect towards methanogens, as indicated by the release of gaseous hydrogen and the high efficiency of methane mitigation. However, high nitrate concentrations also decrease overall fermentation.