Evaluation of 30 novel plant secondary compounds for gas production, methane concentration, nutrient digestibility, and volatile fatty acid concentrations using in vitro batch culture fermentation

Authors: STYPINSKI, JASON - University Of Minnesota; Heuschele, Deborah; SALFER, ISAAC - University Of Minnesota

Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2025
Publication Date: N/A
Citation: N/A
DOI: https://doi.org/10.1017/S0021859626100537

Interpretive Summary: Enteric fermentation from cattle is an indicator of inefficient conversion of animal feed into milk or meat within the animal. To improve the nutrient absorption and digestibility of feed, the dairy industry uses feed additives that reduce methane. Plants produce compounds that have the potential to alter microbial digestion for a reduction in methane and increased feed digestibility. We screened 30 pure plant compounds for methane production, digestibility, and volatile fatty acid profile. A group of compounds were found to reduce methane production, however only thymol decreased methane production and increased digestibility similar to monesin, a feed additive no longer available for farmer use. However other compounds were found to decrease enteric methane production with moderate increase in digestibility. The next steps are to determine the ideal concentrations of thymol and other promising compounds for farm use.

Technical Abstract: Enteric fermentation from ruminants is a major source of anthropogenic methane emissions. Many feed additives have shown promise in significantly reducing these emissions. Some of these feed additives, such as essential oils, are derived from plants, however, a group of plant compounds called ‘secondary metabolites’ have largely not been evaluated for their impacts on methane production. Secondary metabolites are associated with antimicrobial activity as they protect the plant from pathogens, which suggests potential antimethanogenic activity. Therefore, the objective of the current study was to screen 30 pure plant secondary metabolites for gas production (GP) and composition using in vitro techniques. One g of a ground total mixed ration consisting of a 50:50 ratio of forage to concentration was inoculated with 100 ml of a 20:80 ratio of rumen fluid-buffer mixture. Purified compounds were included at a rate of 25 mg per g of feed. Each experimental run consisted of two rumen fluid-buffer blanks and two control flasks without pure compound supplementation. Rumen fluid was collected from two mid-lactation Holstein cows consuming the same basal ration. Flasks were fit with ANKOM RF gas pressure analyzers (ANKOM Technology, Macedone, NY) to record cumulative GP for 48 h, at which point a 10 ml gas subsample was taken for compositional analysis using flame ionized detector gas chromatography (Agilent, Santa Clara, CA). Interestingly, adamantane increased (P < 0.01) total GP by 117%, while stigmasterol and luteolin increased (P < 0.01) total GP by 50.9%. Of the 30 purified compounds evaluated, only thymol and monensin (included as an internal control) reduced (P < 0.01) total GP, by an average of 58.0%. Alpha-pinene increased (P < 0.01) methane concentration by 145% while no compounds reduced methane concentration. Adamantane significantly increased (P < 0.01) methane production by 297%, while abscisic acid, quercetin, rutin, thymol, uridine, and vitexin reduced (P < 0.01) methane production by an average of 60.7%.