Effects of oral nitroethane administration on enteric methane emissions and ruminal fermentation in cattle

Authors: BROWN, ERIN - Stephen F Austin State University; Anderson, Robin; CARSTENS, GORDON - Texas A&M University; GUTIERREZ-BANUELOS, HECTOR - Autonomous University Of Zacatecas; McReynolds, Jackson; SLAY, LISA - Texas A&M University; Callaway, Todd; Nisbet, David

Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2011
Publication Date: 6/10/2011
Citation: Brown, E.G., Anderson, R.C., Carstens, G.E., Gutierrez-Banuelos, H., McReynolds, J.L., Slay, L.J., Callaway, T.R., Nisbet, D.J. 2011. Effects of oral nitroethane administration on enteric methane emissions and ruminal fermentation in cattle. Animal Feed Science and Technology. 166-167:275-281.

Interpretive Summary: Methane is a potent greenhouse gas and its release to the atmosphere is considered to contribute to global warming. Bacteria inhabiting the gastrointestinal tracts of cattle and sheep produce large amounts of methane via an inefficient digestive process that results in the loss of 2% to 15% of the animal’s dietary energy intake. This process also contributes nearly 20% of the United States's total methane emissions. Select short chain nitrocompounds, such as nitroethane, are a type of chemical shown to inhibit growth of foodborne pathogens such as Campylobacter, Listeria, and Escherichia coli O157:H7 while concomitantly inhibiting methane production by gut microbes. However, studies evaluating their effects on methane production and enteric digestion processes in animals are lacking. This study determined effects of oral nitroethane administration on enteric methane emissions and on accumulation of end products of microbial digestion in steers fed a forage based diet. Our results revealed that steers administered a medium dose of nitroethane, 60 mg nitroethane per kg of body weight, ate 14% less food than steers administered either no nitroethane or a low dose of nitroethane, 30 mg nitroethane per kg of steer body weight. As compared to control steers administered no nitroethane, however, methane emitted from the animals was decreased 9% to 22% and estimates of numbers of methane-producing bacteria in the steers gastrointestinal tract were decreased by 24% to 26% in steers administered the medium (60 mg nitroethane per kg animal body weight) or high dose (120 mg nitroethane per kg animal body weight). Microbial digestive processes, as determined by measurement of end products of digestion, were unaffected by nitroethane treatment. Our findings demonstrate that oral administration of nitroethane effectively inhibits methane production by bacteria in the gastrointestinal tract of cattle without adversely affecting digestion. These results provide a foundation for future research that ultimately may yield a strategy that can help cattle and sheep producers reduce the carriage of foodborne pathogens in their animals while at the same time improving digestive efficiency and reducing emissions of methane to the environment.

Technical Abstract: Methane is a potent greenhouse gas and its release to the atmosphere is considered to contribute to global warming. Ruminal enteric methane production represents a loss of 2% to 15% of the animal’s energy intake and contributes nearly 20% of the United States total methane emissions. Studies have evaluated the methane-inhibiting potential of select short chain nitrocompounds, such as nitroethane, but results demonstrating their effects on ruminant respired methane emissions and on ruminal fermentation characteristics in animals are lacking. This study determined effects of oral nitroethane administration on exhaled methane emissions, accumulations of volatile fatty acids, and on ruminal methane-producing activity in steers fed a forage based diet containing 8.8 MJ/kg of metabolizable energy on a dry matter basis. Effects of nitroethane administration on ruminal nitroethane-reducing activity were also determined. Holstein steers (24) averaging 317 ± 6.5 kg body weight were assigned to 4 treatments of 6 steers being: 0, 30, 60, and 120 mg nitroethane/kg BW per d. Treatments were administered via oral gavage twice daily at 08:00 and 16:00 h for 8 d. The DM intake of 7.21 kg/d by steers administered 60 mg nitroethane/kg BW per d was 14% lower (P<0.01) than steers administered 0 or 30 mg nitroethane (i.e., 8.40 and 8.44 kg/d, respectively) but not different from that of steers administered 120 mg nitroethane of 7.80 kg/d. As compared to control steers, exhaled methane emissions (6.86% of GE intake) and ruminal methane-producing activity (5.83 µmol CH4/ml/h) were decreased (P<0.05) 9% to 22% and 24% to 26%, respectively, in steers administered 60 and 120 mg nitroethane/kg BW per d. Ruminal VFA accumulations were unaffected by nitroethane. Results demonstrate that short-term oral administration of nitroethane may be an effective anti-methanogenic compound in steers fed high forage diets. Further research is warranted to determine if strategies using nitroethane lower enteric methane emissions in ruminants long term. Ultimately, nitrocompounds that can be reduced by rumen microbes to yield compounds with nutritional value for the host, such as amino acids, would be preferred.