Effect of sole or combined administration of nitrate and 3-nitro-1-propionic acid on fermentation and Salmonella survivability in alfalfa-fed rumen cultures in vitro

Authors: CASTANEDA CORREA, ALEJANDRO - Universidad Autonoma De Chihuahua; TRACHSEL, JULIAN - Iowa State University; Allen, Heather; CORRAL-LUNA, AGUSTIN - Universidad Autonoma De Chihuahua; GUTIERREZ-BANUELOS, HECTOR - Autonomous University Of Zacatecas; OCHOA-GARCIA, PEDRO - Universidad Autonoma De Chihuahua; RUIZ-BARRERA, OSCAR - Universidad Autonoma De Chihuahua; Hume, Michael; Callaway, Todd; Harvey, Roger; Beier, Ross; Anderson, Robin; Nisbet, David

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2017
Publication Date: 4/1/2017
Citation: Castaneda Correa, A., Trachsel, J., Allen, H.K., Corral-Luna, A., Gutierrez-Banuelos, H., Ochoa-Garcia, P.A., Ruiz-Barrera, O., Hume, M.E., Callaway, T.R., Harvey, R.B., Beier, R.C., Anderson, R.C., Nisbet, D.J. 2017. Effect of sole or combined administration of nitrate and 3-nitro-1-propionic acid on fermentation and Salmonella survivability in alfalfa-fed rumen cultures in vitro. Bioresource Technology. 229:69-77. doi: 10.1016/j.biortech.2017.01.012.

Interpretive Summary: The production of methane by microbes inhabiting the stomach of cattle, sheep, and goats is a digestive inefficiency resulting in the loss of dietary energy consumed by the host and contributes substantially to environmental emissions of methane by agriculture industries worldwide. Nitrate and 3-nitro-1-propionate (abbreviated NPA) are naturally available chemicals being investigated as possible feed supplements to reduce methane emissions by cattle, sheep, and goats, but proper dosing protocols have not yet been determined. Consequently, we conducted two studies to assess effects of co-administering sub-toxic amounts of nitrate, NPA, or their combination on digestion and microbial diversity for a forage-based diet commonly eaten by cattle, sheep, and goats. We found that nitrate and NPA, whether alone or in combination, were very potent inhibitors of methane production, but found also that at the concentrations used in these studies these chemicals were inhibitory to digestion of the forage-based diet. We found also that nitrate, but not NPA, caused undesirable growth promotion of a pathogenic bacterium named Salmonella Typhimurium, and this nitrate-caused growth-promotion was prevented when NPA was co-administered with nitrate. These results reveal a need for dose optimization to safely reduce rumen methane production with forage-based diets. This research will ultimately lead to the development of safe and efficacious supplementation protocols to help farmers and ranchers more economically produce safe meat and milk, while at the same time reducing their impact on the environment.

Technical Abstract: Ruminal methanogenesis is a digestive inefficiency resulting in the loss of dietary energy consumed by the host and contributing to environmental methane emission. Nitrate is being investigated as a feed supplement to reduce rumen methane emissions, but safety and efficacy concerns persist. To assess potential synergies of co-administering sub-toxic amounts of nitrate and 3-nitro-1-propionate (NPA) on fermentation and Salmonella survivability with an alfalfa-based diet, ruminal microbes were cultured with additions of 8 or 16 mM nitrate, 4 or 12 mM NPA, or their combinations. All treatments decreased methanogenesis compared to untreated controls, but volatile fatty acid production and fermentation of hexose were also decreased. Nitrate was converted to nitrite, which accumulated to levels inhibitory to digestion. Salmonella populations were enriched in nitrate only-treated cultures, but not in cultures co- or solely treated with NPA. These results reveal a need for dose optimization to safely reduce rumen methane production with forage-based diets.