Astragalus mollissimus plant extract: a strategy to reduce ruminal methanogenesis

Authors: OCHOA-GARCIA, PEDRO - Universidad Autonoma De Chihuahua; Anderson, Robin; AREVALOS-SANCHEZ, MARTHA - Universidad Autonoma De Chihuahua; RODRIGUEZ-ALMEIDA, FELIPE - Universidad Autonoma De Chihuahua; FELIX-PORTILLO, MONSERRATH - Universidad Autonoma De Chihuahua; MURO-REYES, ALBERTO - Autonomous University Of Zacatecas; BOZIC, ALEKSANDAR - University Of Novi Sad; ARZOLA-ALVAREZ, CLAUDIO - Universidad Autonoma De Chihuahua; CORRAL-LUNA, AGUSTIN - Universidad Autonoma De Chihuahua

Submitted to: Tropical Animal Health and Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2021
Publication Date: 8/16/2021
Citation: Ochoa-Garcia, P.A., Anderson, R.C., Arevalos-Sanchez, M.M., Rodriguez-Almeida, F.A., Felix-Portillo, M., Muro-Reyes, A., Bozic, A., Arzola-Alvarez, C., Corral-Luna, A. 2021. Astragalus mollissimus plant extract: a strategy to reduce ruminal methanogenesis. Tropical Animal Health and Production. 53. Article 436. https://doi.org/10.1007/s11250-021-02882-1.
DOI: https://doi.org/10.1007/s11250-021-02882-1

Interpretive Summary: The production of methane by microbes inhabiting the gut of animals like cattle, sheep, and goats is recognized as being an inefficient process that can result in the loss of up to 12 % of the animals' total energy intake; this also contributes to nearly 25% of the United States' emissions of this potent greenhouse gas. Recent studies have shown that certain chemicals such as nitroethane, nitroethanol, nitropropanol, and nitropropionic acid are capable of inhibiting methane production by the gut bacteria of a cow when tested in the laboratory. However, many of these nitro-based chemicals are made synthetically in the laboratory and thus, the use of the non-natural chemicals will be less desirable in practice. In contrast, some plants of the Astragalus genus produce a natural nitro-based chemical, although its anti-methane-producing effect has not been evaluated. To determine the anti-methane-producing effect, microbial populations obtained from the gut of a cow were treated with a preparation made from the plant named Astragalus mollissimus (called MISER for short). After a 24 h incubation period, methane production was reduced more than 98% for the samples treated with the MISER preparation compared to control populations that received treatment. Additionally, microbial populations from the cow gut that were treated with the MISER preparation produced end products from digestion of feed that demonstrate a more efficient digestive process than the control gut populations. These results demonstrate that the natural nitro-based compound produced in the MISER plant may be a favorable, cost effective alternative to reduce the economic and environmental costs associated with methane production by cattle, sheep, and goats. Ultimately, this research can help farmers and ranchers produce wholesome meat and milk at less cost to the consuming public while decreasing methane emissions to the atmosphere.

Technical Abstract: Ruminal methanogenesis is considered an inefficient process as it can result in the loss of four to 12% of the total energy consumed by the ruminant. Recent studies have shown that compounds such as nitroethane, 2-nitroethanol, 2-nitro-1-propanol, and 3-nitro-1-propionic acid are capable of inhibiting methane production during in vitro studies. However, many of these nitro-compounds are produced synthetically, which could limit the use of the non-natural compounds less desirable in practice. In contrast, some plants of the Astragalus genus produce a natural nitro-compound, although its anti-methanogenic effect has not been evaluated. To determine the anti-methanogenic effect, in vitro cultures of freshly collected mixed populations of ruminal microbes were supplemented with A. mollissimus extracts (MISER). Cultures supplemented with 2-nitroethanol, ethyl 2-nitroacetate, or nitroethane were used as positive controls whereas distilled water was added to the untreated control tubes. After a 24 h incubation period, the methane production was reduced in more than 98% for the samples treated with A. mollissimus extract (P < 0.05) compared to the untreated controls (10.2 ± 0.1 mmol mL**-1 incubated liquid). Cultures supplemented with MISER produced a greater (P < 0.05) amount of total VFA, compared to the rest of treated and untreated cultures. Considering that there are significant differences between MISER treatment, positive controls, and untreated cultures (P < 0.05) regarding the amounts of total gas, gas composition (CH4 and H2), and the amount of VFA produced, we conclude that A. mollissimus poses an alternative strategy to reduce ruminal methanogenesis. To further explore such alternatives, it is necessary to determine if the metabolization byproducts are safe and/or useful for the animal.