|MURRAY, SYRITA - Texas A&M University|
|TRACHSEL, JULIAN - Iowa State University|
|WICKERSHAM, TYRON - Texas A&M University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/5/2015
Publication Date: N/A
Technical Abstract: Rumen methane production results in the loss of up to 12% of the host’s energy intake and contributes to global emissions of this greenhouse gas. Nitrate is being investigated as a feed supplement to reduce rumen methane production, but risks of methemoglobinemia due to accumulation of nitrite are a deterrent to livestock producers. 3-nitro-1-propionate is also a potent inhibitor of rumen methanogenesis but its toxicity to animals differs mechanistically from nitrite. To investigate potential fermentative synergies of co-administration of sub-toxic amounts of nitrate and 3-nitro-1-propionate, mixed populations of ruminal microbes were cultured in triplicate during three consecutive 24 h batch cultures (39oC) without or with sole or co-administration of 22 mM sodium nitrate or 2 mM 3-nitro-1-propionate. Cultures were incubated with 50:50 H2:CO2. Methane produced by controls averaged (±SD) 9.0±2.1 µmol/mL incubation fluid across the incubation series. All treatments reduced methane production >36% during the first incubation series and >80% thereafter. Reductant recovered in volatile fatty acids (VFA) was highest in untreated controls, intermediate in cultures treated solely with 3-nitro-1-propionate, and lowest in nitrate-treated cultures, including those co-treated with 3-nitro-1-propionate (79.1, 56.9, and 9.1 µmol hydrogen/mL, respectively), the latter which directed electrons (74.5 µmol hydrogen/mL) to nitrate reduction and formate accumulation. Fermentation efficiency, based on heats of combustion of glucose fermented and VFA produced, was >14% lower in nitrate- and co-treated cultures than in controls (80.0±2.2%) or cultures treated solely with 3-nitro-1-propionate (84.0±5.0%). Results reveal that co-treatment with 3-nitro-1-propionate did not compensate for the decreasing effect of nitrate on fermentation.