1520
Effect of dietary nitrate and organic copper supplementation on dairy enteric methane and nitrous oxide emissions

Wednesday, July 23, 2014
Exhibit Hall AB (Kansas City Convention Center)
Samantha J Werth , University of California, Davis, Davis, CA
Qian Wang , University of California, Davis, Davis, CA
Clayton J. Neumeier , University of California, Davis, Davis, CA
Girma Getachew , University of California, Davis, Davis, CA
Daniel H Putnam , University of California, Davis, Davis, CA
Alejandro R. Castillo , University of California Cooperative Extension, Merced, CA
Frank M. Mitloehner , University of California, Davis, Davis, CA
Abstract Text: Previous research on nitrate (NO3-) supplementation in dairy cattle diets demonstrated that NO3- is effective in decreasing methane (CH4) production; however, it also induced nitrous oxide (N2O) production under the rumen simulated conditions. One possible strategy to mitigate concomitant N2O emission is by enhancing the activity of nitrous oxide reductase (N2OR) to increase the reduction of N2O to nitrogen gas (N2). Nitrous oxide reductase is a metalloenzyme with one enzyme that contains 12 copper (Cu) atoms to be fully active. Copper availability under rumen condition is typically low, which could impede N2OR activity and therefore the reduction of N2O to N2. Organic (OG), compared to inorganic (IN) Cu, might have a higher availability to microbes under rumen conditions. Organic Cu forms strong chelation complexes with small organic compounds, which renders the Cu complex high stability under the rumen environment (Stevenson, 1994), this may result in higher availability of OG Cu. The present study investigated the effect of OG vs. IN Cu on decreasing NO3- induced N2O production in the simulated rumen using in vitro gas production systems. Gas and liquid samples were obtained from the system every two-hours and were analyzed for carbon dioxide, CH4, N2O, NO3-, nitrite, and ammonium (NH4+) concentrations. Nitrate was totally consumed after 8h. Nitrate decreased (p<0.01) ruminal CH4 by 30.1% but increased (p<0.001) N2O production from 0 to 7.1 uL/g DM. Organic Cu was effective in decreasing (p<0.05) NO3- induced N2O production by 24.7% during enteric fermentation. Ammonium concentration in the rumen fluid was lower (p<0.01) with the supplementation of NO3- compared to urea especially during the early incubation period. In summary, NO3- and OG Cu feeding decreased ruminal CH4 and N2O production concomitantly although total greenhouse gas gasses were not affected by OG Cu supplement. 

Keywords: Cattle, Greenhouse gas, Nitrous oxide reductase

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