Use of blanks to determine in vitro net gas and methane production when using rumen fermentation modifiers

Effects of a flaxseed and pea matrix on in vitro ruminal fermentation, nutrient degradability, and methane emissions

The objective of this study was to determine the impacts of feeding a rumen-protected matrix of fat and protein from flaxseed and peas (LinPRO-R [LIN]; ∼21% fat, 24% CP, and 10.07% n-3 FA; % of DM) on ruminal fermentation, nutrient degradability, and methane emissions, in vitro. Treatments were: 0% (0P), 2.5% (2.5P), 5% (5P), and 7.5% (7.5P) of DM inclusion of LIN, with LIN replacing portions of dried distillers grains and calcium salts of long-chain fatty acids in the diet to maintain similar levels of CP and ether extract (EE). In experiment 1, we used 3 independent runs with 4 replicates per treatment, and 0.5 g of each TMR (16% CP, 33% NDF, 28% starch, 4.2% EE; as % of DM) was incubated in buffered ruminal content for 24 and 48 h, for a total of 6 runs, in glass serum bottles. Gas pressure was measured at 0, 3, 6, 9, 12, 24, and 48 h to estimate total gas and methane productions in the headspace and VFA and lactate concentrations in the fermentation liquid phase. Furthermore, OM degradation was measured at 24 and 48 h after bottles were opened. For experiment 2, twice daily, 53 g of DM of the same treatments was provided to each fermentor. The treatments were arranged in a replicated 4 × 4 Latin square using 8 fermenters. Four 10-d experimental periods (7 d adaptation and 3 d sample collection) were done. Samples were collected from fermentor effluents at 3, 6, 9, and 24 h after morning feeding and composited to determine lactate and VFA concentrations and nutrient degradation. Experiment 1 data were analyzed using PROC GLIMMIX of SAS where treatment was a fixed effect and run was a random effect. Experiment 2 data were analyzed similarly, with square, fermentor within square, period, and the fermentor by treatment interaction being random effects. For experiment 1 with increasing LIN, total gas volume and methane produced per gram of OM degraded decreased linearly, whereas lactate concentration and OM degradability linearly increased. We found no effect of LIN inclusion level on any VFA proportion. For experiment 2 Butyrate and isobutyrate proportions linearly decreased, and NDF degradation quadratically increased, with increasing inclusion of LIN. We found no differences for any other VFA proportions, the total concentration of all VFA, lactate concentration, or the degradation of DM, OM, or CP. Thus, inclusion of LIN, with its higher concentration of n-3, can occur without impairing ruminal fermentation and nutrient degradation; it alters the fermentation profile to reduce total gas volume and methane produced per gram of OM degraded, favors other VFA rather than butyrate or isobutyrate, and increases fiber degradation.

Encapsulated nitrate replacing soybean meal in diets with and without monensin on in vitro ruminal fermentation

This study assessed the association between encapsulated nitrate product (ENP) and monensin (MON) to mitigate enteric methane (CH4) in vitro and possible effects on ruminal degradability, enteric fermentation characteristics, and microbial populations. Six treatments were used in randomized complete design in a 2×3 factorial arrangement with two levels of MON (0 and 2.08 mg/mL of buffered rumen fluid) and three levels of ENP (0, 1.5 and 3.0%). The substrate consisted of 50% Tifton-85 hay and 50% concentrate mixture (ground corn and soybean meal). ENP replaced soybean meal to achieve isonitrogenous diets (15% CP). No ENP×MON interaction was observed for any measured variable (P > 0.05) except for the relative abundance of F. succinogenes (P = 0.02) that linearly increased in diets with MON when ENP was added. The ENP addition decreased CH4 production (P < 0.01) without affecting (P > 0.05) truly degraded organic matter nor the relative abundance of methanogens. Hydrogen production was reduced with MON (P = 0.04) and linearly decreased with ENP inclusion (P = 0.02). We concluded that use of nitrate is a viable strategy for CH4 reduction, however, no additive effect of ENP and MON was observed for mitigating CH4 production.

Fibrolytic enzymes improving in vitro rumen degradability of tropical forages

During specific times of the year, especially dry seasons, tropical forages typically have poor nutritional value due to high contents of neutral and acid detergent fibres, and low crude protein in their composition, which may reduce productivity of ruminant livestock production and lead to increased enteric methane (CH₄ ) emissions per unit of generated product in forage-bases systems. In order to increase fibre degradability and the efficiency of energy utilisation from low-quality forages, exogenous fibrolytic enzymes have been studied. In this assay, we evaluated the effects of increasing dose levels of fibrolytic enzymes extract (FEE) produced by Trichoderma reesei on in vitro rumen organic matter degradability, fermentation parameters, total gas and CH₄ production of tropical forages. Forage samples were analysed for their bromatological composition, and enzyme activity from FEE was performed for xylanase and endoglucanase. The in vitro gas production technique was used in a 5 × 3 factorial arrangement with five FEE dose levels (0, 5, 50, 500 and 5,000 µl) and three substrates (Cynodon spp., Panicum maximum and Cenchrus ciliaris L.). The highest dose level of FEE increased degradability, total gas and CH₄ production in all substrates (p < .05). Butyrate concentration also increased while acetate:propionate ratio and pH decreased with the addition of FEE (p < .05). These results indicated that the use of fibrolytic enzymes can be a reliable strategy to improve degradability of low-quality forages, contributing to the sustainability and intensification of livestock production in tropical countries.

Effect of Hybrid Rye and Maize Grain Processing on Ruminal and Postruminal Digestibility Parameters

The aim of the study was to determine the effect of the method of fragmentation of hybrid rye and maize grain on digestibility parameters for ruminants. Varying degrees of fragmentation – none (whole grains; WG), crushed (CG) or ground to pass through a 4.0 (GG4.0) or 1.5 mm (GG1.5) screen – were estimated by the in sacco nylon bag technique, in vitro true digestibility (IVTD), and the in vitro gas production (GP) technique. WG, CG, GG4.0 and GG1.5 were categorized as none, slight, moderate and extensive fragmentation of the grain kernel, respectively. Three non-lactating cows fitted with ruminal and duodenal cannulas were used to determine the effective rumen degradability (ERD) and intestinal and total tract digestibility (ID and TTD, respectively) of dry matter (DM), crude protein (CP) and starch. IVTD was determined with an ANKOM DaisyII Incubator, and GP and in vitro organic matter digestibility were determined with an ANKOMRF Gas Production System. Dry matter, CP and starch of hybrid rye grain were rapidly degraded in the rumen, and this degradability as well as ID and TTD was only marginally affected by the method of kernel fragmentation; however, among the methods used, the ERD of GG4.0 rye was the lowest. On the other hand, the greater the degree of kernel fragmentation, the higher ERD, ID and TTD were obtained for the DM, CP and starch of maize grain. In summary, rye grain is more susceptible to fermentation in the rumen than maize grain, but the means of grain processing may alter the rate, extent and site of their digestion, particularly for maize grain.

The Reduction of Methane Production in the In Vitro Ruminal Fermentation of Different Substrates is Linked with the Chemical Composition of the Essential Oil

Simple Summary

There is growing concern about how animal-derived foods are produced. Methane production in ruminants has received much attention in relation to its contribution to greenhouse gases and its effect on global warming. Another aspect of livestock production that is questioned by consumers is related to in-feed antibiotics added to improve feed efficiency, and due to health safety issues, their use has been banned or under revision in some parts of the world. Hence, there is the need to find new solutions to mitigate methane production in the rumen in a way that is considered safe and environmental-friendly by consumers and feasible, and without a negative impact on the farmers. Among the alternatives, the use of essential oils to modify rumen fermentation has attracted attention. This paper explores the effectiveness of essential oils obtained from two plants, Lippia turbinata and Tagetes minuta, to reduce methane production during the in vitro fermentation of substrates that are representative of different livestock production systems. The main conclusion to which we arrived is that the extent of the reduction in methane production depends on the interaction between the fermentation conditions that are generated by different substrates and the chemical profile of the essential oil, especially regarding its proportion of oxygenated compounds.

Abstract

There is interest in identifying natural products capable of manipulating rumen microbial activity to develop new feed additives for ruminant nutrition as a strategy to reduce methane. Two trials were performed using the in vitro gas production technique to evaluate the interaction of substrate (n = 5) and additive (n = 6, increasing doses: 0, 0.3, 3, 30, and 300 µL/L of essential oils—EO—of Lippia turbinata or Tagetes minuta, and monensin at 1.87 mg/L). The two EO utilized were selected because they differ markedly in their chemical composition, especially in the proportion of oxygenated compounds. For both EO, the interaction between the substrate and additive was significant for all variables; however, the interaction behaved differently for the two EO. Within each substrate, the response was dose-dependent, without effects at a low level of EO and a negative outcome at the highest dose. The intermediate dose (30 µL/L) inhibited methane with a slight reduction on substrate digestibility, with L. turbinata being more effective than T. minuta. It is concluded that the effectiveness of the EO to reduce methane production depends on interactions between the substrate that is fermented and the additive dose that generates different characteristics within the incubation medium (e.g., pH); and thus, the chemical nature of the compounds of the EO modulates the magnitude of this response.

Encapsulated nitrate replacing soybean meal changes in vitro ruminal fermentation and methane production in diets differing in concentrate to forage ratio

The objective of this study was to evaluate the effects of using encapsulated nitrate product (ENP) replacing soybean meal in diets differing in concentrate to forage ratio on ruminal fermentation and methane production in vitro using a semi-automatic gas production technique. Eight treatments were used in a randomized complete design with a 2 × 4 factorial arrangement: two diet (20C:80F and 80C:20F concentrate to forage ratio) and four levels of ENP addition (0%, 1.5%, 3.0%, and 4.5% of DM) replacing soybean meal. There was a diet × ENP interaction (p = 0.02) for methane production. According to ENP addition, diets with 80C:20F showed more intense reduction on methane production that 20C:80F. A negative linear effect was observed for propionate production with ENP addition in diet with 80C:20F and to the relative abundance of methanogens Archaea, in both diet. The replacement of soybean meal by ENP in levels up to 3% of DM inhibited methane production due to a reduction in the methanogens community without affecting the organic matter degradability. However, ENP at 4.5% of DM level affected fiber degradability, abundance of cellulolytic bacteria, and propionic acid production, indicating that this level of inclusion is not recommended for ruminant production.

Potentials of patchouli (Pogostemon cablin) essential oil on ruminal methanogenesis, feed degradability, and enzyme activities in vitro

The effects of patchouli essential oil (PEO) as an alternative to antibiotics on ruminal methanogenesis, feed degradability, and enzyme activities were evaluated. The basal substrate was incubated without additives (control, CTL) and with monensin (MON, 6 μM/g DM) or patchouli essential oil (PEO, 90 μg/g DM) for 24 h. In three different runs, the gas production (GP) was recorded at 2, 4, 8, 12, and 24 h of incubation using a semi-automatic system. The results revealed that MON had decreased (P < 0.05) the net GP and CH₄ production and digestible and metabolizable energy relative to PEO supplementation. The in vitro truly degraded organic matter was not influenced by PEO application, while was reduced (P = 0.027) with MON. Both PEO and MON had similar reducing effect on the activity of carboxymethylcellulase (P = 0.030), in vitro truly degraded neutral detergent fiber (P = 0.010), NH₃-N concentrations (P = 0.012), acetate proportion (C2, P = 0.046), C2 to C3 ratio (P = 0.023), and total protozoal count (P = 0.017). Both additives recorded similar elevating potential on the α-amylase activity (P = 0.012), propionate (C3) proportion (P = 0.011), and microbial protein (P = 0.034) compared with CTL. Effects of MON and PEO on ruminal feed degradability, microbial enzyme activities, and total protozoa counts may be responsible for modifying rumen fermentation ecology. Addition of PEO may act as a desirable alternative rumen modifier for MON in ruminant diets.

Methodological factors affecting gas and methane production during in vitro rumen fermentation evaluated by meta-analysis approach

Effects of some methodological factors on in vitro measures of gas production (GP, mL/g DM), CH₄ production (mL/g DM) and proportion (% CH₄ on total GP) were investigated by meta-analysis. These factors were considered: pressure in the GP equipment (0 = constant; 1 = increasing), incubation time (0 = 24; 1 = ≥ 48 h), time of rumen fluid collection (0 = before feeding; 1 = after feeding of donor animals), donor species of rumen fluid (0 = sheep; 1 = bovine), presence of N in the buffer solution (0 = presence; 1 = absence), and ratio between amount of buffered rumen fluid and feed sample (BRF/FS; 0 = ≤ 130 mL/g DM; 1 = 130–140 mL/g DM; 2 = ≥ 140 mL/g DM). The NDF content of feed sample incubated (NDF) was considered as a continuous variable. From an initial database of 105 papers, 58 were discarded because one of the above-mentioned factors was not stated. After discarding 17 papers, the final dataset comprised 30 papers (339 observations). A preliminary mixed model analysis was carried out on experimental data considering the study as random factor. Variables adjusted for study effect were analyzed using a backward stepwise analysis including the above-mentioned variables. The analysis showed that the extension of incubation time and reduction of NDF increased GP and CH₄ values. Values of GP and CH₄ also increased when rumen fluid was collected after feeding compared to before feeding (+26.4 and +9.0 mL/g DM, for GP and CH₄), from bovine compared to sheep (+32.8 and +5.2 mL/g DM, for GP and CH₄), and when the buffer solution did not contain N (+24.7 and +6.7 mL/g DM for GP and CH₄). The increase of BRF/FS ratio enhanced GP and CH₄ production (+7.7 and +3.3 mL/g DM per each class of increase, respectively). In vitro techniques for measuring GP and CH₄ production are mostly used as screening methods, thus a full standardization of such techniques is not feasible. However, a greater harmonization of analytical procedures (i.e., a reduction in the number of available protocols) would be useful to facilitate comparison between results of different experiments.

Effects of plants and essential oils on ruminal in vitro batch culture methane production and fermentation

Tekippe, J. A., Hristov, A. N., Heyler, K. S., Zheljazkov, V. D., Ferreira, J. F. S., Cantrell, C. L. and Varga, G. A. 2012. Effects of plants and essential oils on ruminal in vitro batch culture methane production and fermentation. Can. J. Anim. Sci. 92: 395–408. In this study, plants (14) and essential oils (EO; 88) from plants that are naturalized to, or can be successfully grown in North America were evaluated in a batch culture in vitro screening experiments with ruminal fluid as potential anti-methanogenic additives for ruminant diets. Essential oils were tested at four inclusion levels: 0 (blank), 10, 50, and 100 mg L−1and plants were tested at 313, 1250, 2500, and 5000 mg L−1final incubation medium concentration. Compared with the blank, two of the EO increased acetate concentration (8 to 10%), 11 EO increased propionate concentration (9 to 23%), 10 EO increased butyrate concentration (24 to 29%), and three EO reduced methane production [20 to 30%; Anethum graveolens (dill weed oil), Lavandula latifolia, and Ocimum basilicum #7 accession]. Four EO decreased and one increased neutral detergent fiber (NDF) degradability. Three plants increased acetate concentration (8 to 12%), two increased propionate concentration (16%), and one (Origanum vulgare) decreased methane production (31%). Eight of the plants increased NDF degradability at various inclusion levels. Overall, these results indicate that some EO, or EO-producing plants could have a potential anti-methanogenic effect. Further research is needed to verify these results in vivo in long-term experiments.