Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 25, 2009
Publication Date: April 20, 2009
Citation: Anderson, R.C., Huwe, J.K., Smith, D.J., Stanton, T.B., Krueger, N.A., Callaway, T.R., Edrington, T.S., Harvey, R.B., Nisbet, D.J. 2009. Nitroethane, 2-nitro-methyl-propionate and dimethyl-2-nitroglutarate markedly reduce ruminal methane production without adversely affecting ruminal fermentation [abstract]. In: Proceedings of the 2009 Conference on Gastrointestinal Function, April 20-22, 2009, Chicago, IL. p. 562. Technical Abstract: Ruminal methanogenesis is considered a digestive inefficiency that results in the loss of 2-12% of the host’s gross energy intake and accounts for nearly 20% of the United States’ annual CH4 emissions. The objective of the present experiment was to evaluate the effects of the known CH4 inhibitor, nitroethane (NE) and two synthetic nitrocompounds, 2-nitro-methyl-propionate (NMP) and dimethyl-2-nitroglutarate (DNG) on ruminal CH4 production and fermentation in vitro. Ruminal fluid (10 ml/tube) obtained from a pasture fed cow was incubated (n = 3/treatment) at 39degC under 100% CO2 with 0.2 g alfalfa. After 24 h, incubations supplemented with 2.5 or 10 mM NE, NMP and DNG reduced (P less than 0.05) CH4 production greater than 92% compared to controls incubated without added nitrocompound (10.3 +/- 2.2 umol CH4 ml-1 ruminal fluid). Amounts of acetate, propionate, isobutyrate, isovalerate, and valerate produced were unaffected (P greater than 0.05) by nitro-treatment, averaging 33.4 +/- 14.4, 16.8 +/- 4.9, 0.4 +/- 0.2, 0.6 +/- 0.3 and 1.0 +/- 0.4 umol ml-1, respectively. Incubations containing 2.5 or 10 mM NE produced more butyrate (11.3 +/- 0.7 and 12.7 +/- 1.6 umol ml-1, respectively) than controls (4.3 +/- 1.8 umol ml-1) (P less than 0.05). Measurable amounts of lactate and formate did not accumulate in control or nitro-treated incubations. Accumulations of NH3 were increased (P less than 0.05), although slightly, in incubations containing 10 mM NE or 2.5 mM NMP (1.8 +/- 0.1 and 2.0 +/- 0.2 umol ml-1, respectively) compared to controls (1.4 +/- 0.1 umol ml-1) but not in any of the other nitro-treated incubations. Stoichiometric estimates of amounts of hexose fermented were unaffected (P greater than 0.05) by nitro-treatment and averaged 35.5 +/- 12.4 umol ml-1. Electron balance estimates of reducing equivalents produced were also unaffected by nitro-treatment, averaging 122.9 +/- 45.2 umol H2 ml-1. Greater than 96% of the reducing equivalents produced in the control incubations were recovered in fermentation products. However, because CH4 production was reduced by nitro-treatment amounts of reducing equivalents recovered in fermentation, products from nitro-treated incubations were consequently reduced greater than 36% (P less than 0.05). We hypothesize, but have yet to confirm, that microbial reduction of the added nitrocompounds may consume some of the reducing equivalents not accounted for in measured fermentation products.