Objective: Fasting may lead to changes in the microbiota and activity in the rumen. In the present study, the effects of fasting on rumen microbiota and the impact of fasting on in vitro rumen fermentation were evaluated using molecular culture-independent methods. Methods: Three ruminally cannulated Holstein steers were fed rice straw and concentrates. The ruminal fluids were obtained from the same steers 2 h after the morning feeding (control) and 24 h after fasting (fasting). The ruminal fluid was filtrated through four layers of muslin, collected for a culture-independent microbial analysis, and used to determine the in vitro rumen fermentation characteristics. Total DNA was extracted from both control and fasting ruminal fluids. The rumen microbiota was assessed using denaturing gradient gel electrophoresis (DGGE) and quantitative polymerase chain reaction. Microbial activity was evaluated in control and fasting steers at various intervals using in vitro batch culture with rice straw and concentrate at a ratio of 60:40. Results: Fasting for 24 h slightly affected the microbiota structure in the rumen as determined by DGGE. Additionally, several microorganisms, including Anaerovibrio lipolytica, Eubacterium ruminantium, Prevotella albensis, Prevotella ruminicola, and Ruminobacter amylophilus, decreased in number after fasting. In addition, using the ruminal fluid as the inoculum after 24 h of fasting, the fermentation characteristics differed from those obtained using non-fasted ruminal fluid. Compared with the control, the fasting showed higher total gas production, ammonia, and microbial protein production (p<0.05). No significant differences, however, was observed in pH and dry matter digestibility. Conclusion: When in vitro techniques are used to evaluate feed, the use of the ruminal fluid from fasted animals should be used with caution.

Journal of Animal Science and Technology (JAST) is a peer-reviewed, open access journal publishing original research, review articles and notes in all fields of animal science. Topics covered by the journal include: genetics and breeding, physiology, nutrition of monogastric animals, nutrition of ruminants, animal products (milk, meat, eggs and their by-products) and their processing, grasslands and roughages, livestock environment, animal biotechnology, animal behavior and welfare.

This study was conducted in order to examine the impact of magnetite (Fe₃O₄), a conductive material capable of promoting direct interspecies electron transfer (DIET) among microorganisms, on the efficiency of anaerobic digestion in a plug flow reactor (PFR) using food wastewater (FW) as the substrate. The effects of recovering and replenishing magnetite discharged along with the digestate during continuous operation of the PFR were also evaluated. A PFR with a total volume of 17 L was utilized as the reactor for anaerobic digestion. The inoculum was obtained from Icheon Biogas Research Facility, which operated with a mixture of pig slurry and FW in a 7:3 (w/w) ratio. FW was used as the substrate (volatile solids (VS) content of 85,865 mg-VS/L). The PFR was set for operation at 39 °C, and after a stabilization period of approximately 82 days, the hydraulic retention time (HRT) was set at 40 days. The study was conducted in three stages: stage 1 (83~122 days), stage 2 (123~162 days), and stage 3 (163~202 days). For the maintenance of an organic loading rate of 2.12 kg-VS/m³/d, 0.3 L/d of substrate was added every 24 h, and analysis of an equal amount of discharged digestate was performed. The experimental treatments included a control without the addition of magnetite after the stabilization period, treatment (T1) with addition of magnetite (20 mM in digestate) and subsequent recovery and replenishment of magnetite on the discharge of digestate, and treatment (T2) with addition of magnetite (20 mM) without the replenishment of magnetite. Analytical parameters included the characteristics of the discharged digestate (pH, NH₄⁺-N, chemical oxygen demand (COD_Cr), total volatile fatty acids (TVFAs), and alkalinity), and methane production (M_p). During the period of operation of the PFR after the stabilization period, no significant differences in pH and NH₄⁺-N, based on the recovery and replenishment of magnetite, were observed, and a stably functioning PFR was observed. However, in stage 2, due to the increased degradation of organic matter caused by DIET, the COD_Cr of T1 and T2 decreased by 9.42% compared with the control. In stage 3, the magnetite content in the reactor in T2 decreased by a maximum of 9.42% compared to T1. In stage 3, the M_p for T2 was similar to that of the control, with a maximum discharge of magnetite of 3.06%, and the M_p decreased by 5.40% compared to T1. Regarding the ratio of methanogens in the community, the results of an analysis of the digestate from stage 3 showed an increase in the community of acetotrophic methanogens, specifically Methanosarcina. The findings of this study confirm that DIET was effectively promoted by maintaining the concentration of 20 mM magnetite in the PFR while using FW as a substrate.

This study investigated the feasibility of incorporating Chenopodium album L. (CAL) into ruminant feed ingredients through evaluating the effects of harvest time and substitution levels on in vitro rumen fermentation. In the first phase, a sole-substrate experiment was conducted using CAL harvested from June to August, analyzing its chemical composition and total saponins content. The impact of harvest time on fermentation parameters was assessed with CAL as the sole substrate. The second phase involved a mixed-substrate experiment using an early-fattening Hanwoo diet (30% rice straw and 70% concentrate), where increasing proportions of CAL (control: 0%, T1: 5%, T2: 10%, T3: 15%, and T4: 20%) replaced rice straw. Seasonal variations in CAL composition influenced the fermentation characteristics. CAL harvested in July exhibited higher fermentability, with total volatile fatty acids (TVFAs) reaching 103.87 mM at 72 h. In contrast, CAL harvested in August showed lower fermentability and digestibility. However, August-harvested CAL was selected for the subsequent experiment, as it provided a more practical balance of sufficient biomass yield and a higher saponins concentration, aligned with the study’s methane mitigation objectives, while also exhibiting a fiber composition comparable to that of rice straw. We hypothesized that the saponins in CAL contribute to methane reductions. Supplementation with 15% of CAL significantly reduced methane production per gram of inoculated and digested dry matter (p < 0.05), likely due to differences in crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and saponins content. However, despite having the lowest fiber content, T4 (20% CAL) exhibited the lowest in vitro dry matter digestibility (IVDMD), suggesting that factors such as saponins, CAL’s chemical composition, or microbial shifts may have hindered digestibility. Ammonia–nitrogen production increased from 0 to 3 h, but it continuously decreased between 3 and 9 h due to microbial growth and nitrogen assimilation, as microbes incorporate ammonia into their biomass (p < 0.05). Fermentation characteristics further revealed that the acetate-to-propionate (A/P) ratio decreased with increasing CAL levels, with T4 showing the lowest ratio (1.55 at 72 h), confirming a shift toward propionate-based fermentation. Notably, T2 (10% CAL) showed an optimized fermentation efficiency, producing the highest TVFA concentration at 24 h (98.28 mM). These findings highlight the potential for using CAL as a functional feed ingredient, with moderate substitution levels (10–15%) enhancing fermentation efficiency while reducing methane production.

This study investigated the feasibility of incorporating Chenopodium album L (CAL) into ruminant feed ingredients by evaluating the effects of harvest time and substitution levels on in vitro rumen fermentation. In the first phase, a sole-substrate experiment was conducted using CAL harvested from June to August, analyzing its chemical composition and total saponin content. The impact of harvest time on fermentation parameters was assessed with CAL as the sole substrate. The second phase involved a mixed-substrate experiment using an early-fattening Hanwoo diet (30% rice straw and 70% concentrate), where increasing proportions of CAL (Control: 0%, T1: 5%, T2: 10%, T3: 15%, and T4: 20%) replaced rice straw. Seasonal variations in CAL composition influenced fermentation characteristics, with July-harvested CAL exhibiting higher fermentability, while August-harvested CAL had lower fermentability. However, August-harvested CAL was selected for the second experiment due to its greater availability. We hypothesized that saponins in CAL contribute to methane reduction. Supplementation with 15% of CAL significantly reduced methane production per gram of digested substrate (p < 0.05), likely due to differences in crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and saponin content. However, despite having the lowest fiber content, T4 (20% CAL) exhibited the lowest in vitro dry matter digestibility (IVDMD), suggesting that factors such as saponins, CAL’s chemical composition, or microbial shifts may have hindered digestibility. Fermentation characteristics further revealed that the acetate-to-propionate (A/P) ratio decreased with increasing CAL levels, with T4 showing the lowest ratio (1.55 at 72 hours), confirming a shift toward propionate-based fermentation. Notably, T2 (10% CAL) optimized fermentation efficiency, producing the highest total volatile fatty acid (VFA) concentration at 24 hours (98.28 mM). These findings highlight the potential of CAL as a functional feed ingredient, with moderate substitution levels (10–15%) enhancing fermentation efficiency while reducing methane production.