Paenibacillus 79R4, a potential rumen probiotic to enhance nitrite detoxification and methane mitigation in nitrate-treated ruminants

Authors: LATHAM, ELIZABETH - Texas A&M University; PINCHAK, WILLIAM - Texas A&M Agrilife; TRACHSEL, JULIAN - Iowa State University; Allen, Heather; Callaway, Todd; Nisbet, David; Anderson, Robin

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2019
Publication Date: 3/25/2019
Citation: Latham, E.A., Pinchak, W.E., Trachsel, J., Allen, H.K., Callaway, T.R., Nisbet, D.J., Anderson, R.C. 2019. Paenibacillus 79R4, a potential rumen probiotic to enhance nitrite detoxification and methane mitigation in nitrate-treated ruminants. Science of the Total Environment. 671:324-328. https://doi.org/10.1016/j.scitotenv.2019.03.390.
DOI: https://doi.org/10.1016/j.scitotenv.2019.03.390

Interpretive Summary: Cattle and sheep are important meat- and milk-producing animals that can sometimes carry unwanted foodborne pathogens in their gastrointestinal tract and emit considerable amounts of methane, a potent greenhouse gas, into the atmosphere due to digestive inefficiencies in their gut. Recently, we isolated a novel pathogen-fighting bacterium, which we have named Paenibacillus 79R4, from the gut of a cow and found in laboratory studies that this beneficial bacterium could dramatically reduce methane production by gut bacteria when grown with a certain nutrient. The objective of this study was to see if the laboratory results could be repeated in real world animal settings. We found that when the special nutrient, called nitrate, and Paenibacillus 79R4 were administered to Holstein steers, methane-production by the steers' gut contents was significantly decreased. The nitrate-treated steers administered both the nutrient and Paenibacillus 79R4 had a better blood profile than steers that were administered only the nutrient. Accumulations of fermentation acids and determinations of fermentation efficiency revealed that steers administered both Paenibacillus 79R4 and nitrate were improved compared to steers administered nitrate alone. These results demonstrate that inoculation of nitrate-fed ruminants with Paenibacillus 79R4 can help prevent and reduce methane emissions without inhibiting fermentation efficiency by the microbial ecosystem. Ultimately, this research will help farmers and ranchers produce safer food at less cost and lower environmental impact.

Technical Abstract: This study aimed to investigate the effects of dietary nitrate and a denitrifying ruminal bacterium selected for enhanced nitrate- and nitrite-metabolizing ability, designated as Paenibacillus 79R4 (79R4) in vivo. Measurements included methane emissions, nitrate- and nitrite-metabolizing ability, and volatile fatty acid concentrations. When inoculated to nitrate-treated (83 mg sodium nitrate/kg body weight) Holstein steers (786 ± 29.3 kg), the strain 79R4 (provided to achieve 10**6 cells/mL rumen contents) tended to decrease methane-producing activity of ruminal contents more (P < 0.10) than by nitrate treatment alone (51 versus 46%). The nitrate-treated steers inoculated with strain 79R4 tended to have less methemoglobin (P < 0.10) and had increased ruminal nitrate- and nitrite- metabolizing activity (P < 0.05) compared with steers treated with nitrate alone. Accumulations of fermentation acids and estimates of amounts of hexose fermented in the rumen of animals administered the nitrite-selected Paenibacillus 79R4 and nitrate were more similar to pretreated animals than to steers administered nitrate alone. These results demonstrate that inoculation of nitrate-fed ruminants with the nitrite-selected Paenibacillus 79R4 can help prevent nitrite toxicity in the host while maintaining benefits of reduced methane emissions without inhibiting fermentation efficiency by the microbial ecosystem.