Details

Autor(en) / Beteiligte

• Welty, C.M.
• Wenner, B.A.
• Wagner, B.K.
• Roman-Garcia, Y.
• Plank, J.E.
• Meller, R.A.
• Gehman, A.M.
• Firkins, J.L.

Titel

Rumen microbial responses to supplemental nitrate. II. Potential interactions with live yeast culture on the prokaryotic community and methanogenesis in continuous culture

Ist Teil von

• Journal of dairy science, 2019-03, Vol.102 (3), p.2217-2231

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2019

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• Nitrates have been fed to ruminants, including dairy cows, as an electron sink to mitigate CH4 emissions. In the NO3− reduction process, NO2− can accumulate, which could directly inhibit methanogens and possibly other microbes in the rumen. Saccharomyces cerevisiae yeast was hypothesized to decrease NO2− through direct reduction or indirectly by stimulating the bacterium Selenomonas ruminantium, which is among the ruminal bacteria most well characterized to reduce both NO3− and NO2−. Ruminal fluid was incubated in continuous cultures fed diets without or with NaNO3 (1.5% of diet dry matter; i.e., 1.09% NO3−) and without or with live yeast culture (LYC) fed at a recommended 0.010 g/d (scaled from cattle to fermentor intakes) in a 2 × 2 factorial arrangement of treatments. Treatments with LYC had increased NDF digestibility and acetate:propionate by increasing acetate molar proportion but tended to decrease total VFA production. The main effect of NO3− increased acetate:propionate by increasing acetate molar proportion; NO3− also decreased molar proportions of isobutyrate and butyrate. Both NO3− and LYC shifted bacterial community composition (based on relative sequence abundance of 16S rRNA genes). An interaction occurred such that NO3− decreased valerate molar proportion only when no LYC was added. Nitrate decreased daily CH4 emissions by 29%. However, treatment × time interactions were present for both CH4 and H2 emission from the headspace; CH4 was decreased by the main effect of NO3− until 6 h postfeeding, but NO3− and LYC decreased H2 emission up to 4 h postfeeding. As expected, NO3− decreased methane emissions in continuous cultures; however, contrary to expectations, LYC did not attenuate NO2− accumulation.