Rumen Methanogenesis, Rumen Fermentation, and Microbial Community Response to Nitroethane, 2-Nitroethanol, and 2-Nitro-1-Propanol: An In Vitro Study

• Main Authors: Zhenwei Zhang, Yanlu Wang, Xuemeng Si, Zhijun Cao, Shengli Li, Hongjian Yang
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Animals
• Subjects: nitrocompounds; methanogenesis; rumen fermentation; microbial community; coenzyme
• Online Access: https://www.mdpi.com/2076-2615/10/3/479

Nitroethane (NE), 2-nitroethanol (NEOH), and 2-nitro-1-propanol (NPOH) were comparatively examined to determine their inhibitory actions on rumen fermentation and methanogenesis in vitro. Fermentation characteristics, CH₄ and total gas production, and coenzyme contents were determined at 6, 12, 24, 48, and 72 h incubation time, and the populations of ruminal microbiota were analyzed by real-time PCR at 72 h incubation time. The addition of NE, NEOH, and NPOH slowed down in vitro rumen fermentation and reduced the proportion of molar CH₄ by 96.7%, 96.7%, and 41.7%, respectively (<i>p</i> &lt; 0.01). The content of coenzymes F₄₂₀ and F₄₃₀ and the relative expression of the <i>mcr</i>A gene declined with the supplementation of NE, NEOH, and NPOH in comparison with the control (<i>p</i> &lt; 0.01). The addition of NE, NEOH, and NPOH decreased total volatile fatty acids (VFAs) and acetate (<i>p</i> &lt; 0.05), but had no effect on propionate concentration (<i>p</i> &gt; 0.05). Real-time PCR results showed that the relative abundance of total methanogens, <i>Methanobacteriales</i>, <i>Methanococcales,</i> and <i>Fibrobacter succinogenes</i> were reduced by NE, NEOH, and NPOH (<i>p</i> &lt; 0.05). In addition, the nitro-degradation rates in culture fluids were ranked as NEOH (&#8722;0.088) &gt; NE (&#8722;0.069) &gt; NPOH (&#8722;0.054). In brief, the results firstly provided evidence that NE, NEOH, and NPOH were able to decrease methanogen abundance and dramatically decrease <i>mcr</i>A gene expression and coenzyme F₄₂₀ and F₄₃₀ contents with different magnitudes to reduce ruminal CH₄ production.