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This study investigated the effect of inclusion of dietary oligosaccharides, onion peel, and an essential oil blend (EOB; containing anise, clove, oregano, cedarwood, and ginger in the ratio 4:2:2:1:1) individually and in combinations in the total mixed ration of dairy cattle on in vitro gas production (GP), dry matter disappearance (DMD), fiber fraction disappearance, and total and individual volatile fatty acid (VFA) production. EOB was used at 200 µL g-1 of feed while the other additives were administered at 3% of the feed on a dry matter basis. The in vitro batch culture technique was used for this experiment and the design was a completely randomized design with 12 treatments replicated eight times. The total GP at 24 h was significantly (p < 0.0001) reduced by the inclusion of EOB-containing additives in the total mixed ration. The lowest gas volume was recorded for the treatment containing mannanoligosaccharide + EOB while the highest value was recorded for sole onion peel treatment. The EOB treatment had the lowest methane production while onion peel alone had the highest values for the greenhouse gas parameters. The inclusion of EOB individually and in combination with the oligosaccharides reduced (p < 0.05) propionate and increased acetate molar proportions, with the highest acetate and lowest propionate noted for the galacto-oligosaccharide and onion peel mixture treatment. Inclusion of the additives evaluated in this study had positive effects on rumen fermentation and digestibility indices with a potential for abatement of greenhouse gases when EOB is present individually or in combination with the oligosaccharides. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of an essential oil/fumaric combination, mannan-oligosaccharide, galactooligosaccharide, and a mannan-oligosaccharide/galactooligosaccharide combination on the dry matter disappearance (DMD), gas production, greenhouse gasses, volatile fatty acid, and microbial community of a total mixed ration using a 24 h in vitro batch culture technique. The study design was a completely randomized design with four treatments as follows: a control treatment without any additives, the control treatment supplemented with galactooligosaccharide at 3% (Gos treatment), a galactooligosaccharide and mannan-oligosaccharide mixture at 1:1 at 3% (Gosmos treatment), or an essential oil blend (200 μL/g feed) and fumaric acid at 3% combination (Eofumaric treatment). The Gosmos treatment had the highest (p < 0.05) DMD (63.8%) and the numerical lowest acetate–propionate ratio (p = 0.207), which was 36.9% higher compared to the control. The lowest Shannon index, Simpson's index, and all the diversity indices were recorded for the Eofumaric treatment, while the other treatments had similar Shannon index, Simpson's index, and diversity index. The Z-score differential abundance between the Eofumaric and the control indicated that the inclusion of the Eofumaric treatment differentially increased the abundance of Patescibacteria, Synergistota, Chloroflexi, Actinobacteriota, Firmicutes, and Euryarchaeota while Verrucomicrobiota, WPS-2, Fibrobacterota, and Spirochaetota were decreased. The Random Forest Classification showed that the lower relative abundance of Fibrobacterota, Spirochaetota, and Elusimicrobiota and the higher relative abundance of Firmicutes and Chloroflexi were most impactful in explaining the microbial community data. Overall, the essential oil blend showed great potential as a methane gas mitigation strategy by modifying rumen fermentation through changes in the microbial community dynamics. [ABSTRACT FROM AUTHOR]

Simple Summary: Essential oil blends show promise as natural ruminant feed additives, potentially modulating rumen fermentation and mitigating greenhouse gas emissions. The present study investigated the metabolite profiles, methane production, and fermentation dynamics of five novel essential oil blends in Black Angus beef cattle. The blends, composed of four distinct essential oils in varying proportions, were directly infused into the rumen to simulate practical application. Advanced metabolomics techniques were employed to analyze and elucidate the EOB-induced changes in the rumen fluid. Results demonstrated that the infusion of the blends modified the rumen metabolism, fermentation patterns, and metabolite production. The study provides insights into how the essential oil blends influenced the specific metabolic processes and fermentation characteristics in the rumen. This research contributes to the development of bio-based strategies for optimizing rumen function, offering valuable information for animal nutritionists and producers aiming to improve feed efficiency and minimize the environmental footprint of ruminant livestock production. Essential oils are natural feed additives that improve animal health and enhance their performance. This study investigated the effects of the rumen infusion of five essential oil blends (EOBs) on greenhouse gas (GHG) emissions, rumen fermentation parameters, and rumen metabolome and metabolic pathways in Black Angus cows. Using a 6 × 6 Latin Square experimental design, a 90-day study was conducted with six cattle. A daily dosage of 4 mL of EOBs was administered during each infusion. Volcano plot analyses between the control (CON) and each of the EOBs (EOB1, EOB2, EOB3, EOB4, and EOB5) revealed several differentially abundant (p ≤ 0.05; absolute fold change ≥1.5) metabolites. The EOB5 treatment exhibited the most significant impact, with 26 differentially abundant metabolites, including elevated valine and reduced gallic acid. Volatile fatty acids (VFAs), including valerate, isobutyrate, and isovalerate, were significantly increased (p < 0.05). GHG emissions were not significantly affected, but a numerical decrease was observed in the animals infused with the EOB5 treatment. Ammonia nitrogen concentrations remained within the suitable range for rumen microbes' growth, indicating a normal internal environment for microbial crude protein synthesis. In conclusion, the study has demonstrated that the direct infusion of EOBs significantly improved the generation of VFAs and impacted the energy production, protein synthesis, and microbial activity of the animals. [ABSTRACT FROM AUTHOR]

The present study evaluated the inclusion of fumaric acid and essential oil blends (EOBs) containing anise, cedarwood, clove, cumin, eucalyptus, garlic, ginger, lavender, lemongrass, nutmeg, oregano, and peppermint at different proportions on in vitro dry matter (DM) disappearance (DMD), fiber fraction disappearance, the efficiency of microbial production, and the total volatile fatty acids (VFAs). Ten treatments without (control treatment) or with different EOB/fumaric combinations were used in the study with eight replicates. The EOB inclusion level was 200 μL/g of feed (total mixed ration, (TMR)) while fumaric acid was administered at 3% of the TMR (DM basis). The highest DMD, in vitro true degradable DM, partitioning factor (PF24), and in vitro apparent degradable DM were recorded for the fumaric only treatment and the control. Neutral detergent fiber disappearance was reduced with the inclusion of EOB/fumaric combinations. The production of microbial mass and undegraded DM were higher (p < 0.001) for all EOBs and EOB and fumaric treatments. The inclusion of EOB and fumaric combinations reduced (p < 0.001) the total gas production, methane, and ammonia, with a higher PF24 value noted for EOB3 treatment. The inclusion of individual EOB1 containing garlic, lemongrass, cumin, lavender, and nutmeg in a ratio of 4:2:2:1:1 or combined with fumaric acid yielded the highest propionate concentration across all treatments. We concluded that EOBs decreased methane production and nutrient degradability with better results with the individual EOB1 or EOB1/fumaric combination, which showed a potential enhancement in energy production. [ABSTRACT FROM AUTHOR]

This study evaluated the synergistic effects of prebiotics containing galacto-oligosaccharides (GOS) and/or mannan oligosaccharides (MOS), essential oil blend (EOB), and onion peel (OPE) on fermentation characteristics using the rumen simulation technique (RUSITEC) system. Three rumen-cannulated, non-lactating Holstein Friesian cows were the inoculum donors. The substrate used for the study was a total mixed ration (TMR), which consisted of corn silage, alfalfa hay, and concentrate at 6:2:2, respectively. Sixteen fermentation vessels were randomly allotted to four treatments with four replicates each over a 9-day period in a completely randomized design. The treatments assessed include: control [TMR only], GEO [TMR + GOS + EOB + OPE], MEO [TMR + MOS + EOB + OPE], and OLEO [TMR + OLG + EOB + OPE]. OLG comprises GOS and MOS in equal proportion. EOB was included at 3 µL/g, while OPE, GOS, MOS, and OLG were added at 30 mg/g TMR. Results showed that pH, gas volume, effluent volume, and ammonia-N were not affected (p > 0.05) by the different additives. Similarly, greenhouse gas (GHG) emissions and nutrient digestibility were not affected by the treatments. Compared to the control, total volatile fatty acids (VFA) were decreased (p < 0.05) by 14.8, 10.8, and 8.5% with GEO, MEO, and OLEO inclusion, respectively, while the molar proportion of acetate was increased (p = 0.011) by 3.3, 1.1, and 3.8% with GEO, MEO, and OLEO inclusion, respectively. MEO increased isobutyrate (p = 0.001) and branched chain VFA (p = 0.013) contents; however, GEO and OLEO inclusion reduced them. Overall, the interaction of EOB, OPE, GOS, and/or MOS did not affect nutrient digestibility or GHG emissions but reduced VFA production. Further research is recommended to assess the dose effect of the additives on GHG emissions and VFA production; and to determine the long-term effects of these interventions on the rumen microbiome and animal performance. [ABSTRACT FROM AUTHOR]

Essential oils (EO) and fumaric acid (FA) are known for their ability to reduce greenhouse gas (GHG) emissions in ruminant animals. This study aimed to investigate the combined impact of essential oil blend (EOB) and FA (EF) on in vitro fermentation, total gas and volatile fatty acid (VFA) production and GHG emissions of a calf feed in a 24 h batch culture study. Rumen-cannulated black Angus beef cows (n = 3) served as inoculum donors. The calf feed contained 910, 5.8, 70.9, 792, 111, 72 g/kg dry matter (DM), fat, ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL), respectively. The EOB contained equal proportions of ginger, anise, peppermint, oregano and thyme. FA was added at 3% along with EOB at 10, 20, 30 and 40 µL/g calf feed. Five treatments evaluated were Control (without additives), EF10, EF20, EF30, and EF40. Results showed that pH and digestibility of DM, NDF, ADF were not significantly (P > 0.05) affected by the EF treatments (Table 1). ADL digestibility decreased linearly (P < 0.001) with increasing EF dosage. EF40 increased (P < 0.05) cellulose digestibility by approximately 11% compared with EF10. Total gas, methane and carbon dioxide production decreased (linear, quadratic, P < 0.001) with EF inclusion (Table 2). Ammonia concentration decreased linearly (P = 0.009) with increasing EF dosage, while hydrogen sulfide gas was not affected. EF inclusion reduced (P < 0.001) total VFA, acetate but increased propionate and butyrate proportion (Table 3). In conclusion, the combination of EOB and FA effectively mitigated GHG emissions without compromising nutrient digestibility in calves. Therefore, incorporating EOB at 10 µL/g and FA at 3% in calf feed is recommended as an effective nutritional strategy to reduce GHG emissions in calves. [ABSTRACT FROM AUTHOR]

Dairy products have a crucial role in the diets of over 6 billion people worldwide, providing essential nutrients such as energy, high-quality protein, and micronutrients. With dairy cows accounting for nearly 81% of global milk production, strategies to increase milk production sustainably are vital, especially with the U.S. being the second-largest producer. Essential oil blends (EOB), onion peel extract (OPE), and prebiotics such as mannan oligosaccharides (MOS) and galactooligosaccharides (GOS) offer promising avenues to enhance bovine milk production. These additives have the potential to modify rumen ecology and fermentation activity, while also mitigating greenhouse gas emissions in dairy cows. Therefore, this study investigated the effects of combining EOB, OPE, GOS, and/or MOS on specific rumen metabolites and metabolic pathways using the rumen simulation technique (RUSITEC) system. Rumen-cannulated non-lactating Holstein Friesian cows (n = 3) were used as rumen fluid donors. Total mixed ration (TMR) consisted of corn silage (60%), alfalfa hay (20%), and concentrate (20%). Using a completely randomized design, 16 fermentation vessels were divided into 4 groups with 4 replicates each over a 9-d period. The treatments included a control group (CON; TMR only), GEO (TMR+GOS+EOB+OPE), MEO (TMR+MOS+EOB+OPE), and OLEO (TMR+OLG+EOB+OPE). The EOB comprised of garlic, lemongrass, cumin, lavender, and nutmeg (4:2:2:1:1), while OLG contained GOS and MOS in equal proportions. EOB was added at 10 μL/g, and OPE, GOS, MOS, and OLG were included at 30 mg/g TMR. Rumen effluents were collected over 5 d for quantitative untargeted metabolome analysis. Analysis of rumen effluents using liquid chromatography-mass spectrometry and MetaboAnalyst 5.0 revealed 495 detected and identified metabolites. Volcano plot analysis showed no significant differences (P ≥ 0.05) in metabolite abundance between the CON and MEO, GEO, or OLEO treatments. Partial least squares-discriminant analysis (PLS-DA) also indicated no clear separation between the CON and treatment groups, suggesting no significant alteration in the metabolome. Compared with CON, the relative concentrations of dopamine 4-O-glucuronide, proline, and histamine were less while pyrocatechol was greater in MEO group. Isomer 1 of 2-hydroxyhepta-2,4-dienedioic acid, histamine, and dopamine 4-O-glucuronide were less while 2-aminomuconic acid and isomer 1 of hulupinic acid were greater in the GEO group. Histamine was less and hydroxypyridine was greater in the OLEO group. Phosphonate and phosphinate metabolism tended to be upregulated in OLEO. Meanwhile, metabolic pathways related to amino acids, vitamins, nitrogen metabolism, and primary bile acid biosynthesis remained unaltered by MEO, GEO and OLEO treatments. In summary, the study demonstrated that the inclusion of MEO, GEO, and OLEO had no adverse effects on rumen metabolites. Future research should focus on combinations of nutraceuticals that could positively impact nutrient metabolism and production performance of dairy cows. [ABSTRACT FROM AUTHOR]