Nitrocompounds as potential methanogenic inhibitors in ruminant animals: A review

• Published in: Animal feed science and technology 2018-02, Vol.236, p.107-114
• Main Authors: Zhang, Zhen-Wei, Cao, Zhi-Jun, Wang, Yan-Lu, Wang, Ya-Jing, Yang, Hong-Jian, Li, Sheng-Li
• Format: Article
• Language: English
• Subjects: Methane production; Methanogenic inhibitors; Nitrocompounds; Ruminant
• ISSN: 0377-8401; 1873-2216
• DOI: 10.1016/j.anifeedsci.2017.12.010

Antimethanogenic mechanisms of nitrocompounds and its metabolism in rumen. NE, nitroethane, 2NEOH, 2-nitroalcohol; 2NPOH, 2-nitro-1-propanol; 3NPOH, 3-nitro-1-propanol; 3NPA, 3-nitro-1-propionic acid; D. detoxificans, Denitrobacterium detoxificans; A, hydrogen flow: interspecies-hydrogen transfer; B, hydrogen flow: contrabute to some VFA production (minority); ⊗, inbibition effect. [Display omitted] •Nitrocompounds show high antimethanogenic efficiency in the rumen fermentation.•The antimethanogenic action mode is discussed in terms of VFA, H2 accumulation, etc.•D. detoxificans can tolerate high levels of nitrotoxins metabolized from nitrocompounds.•Coenzymes responsible for methyl-group and H-electron transfer are less addressed. Methane production by ruminant husbandry, a major source of greenhouse gas emissions, has been increasingly regarded as an enormous threat to global climate warming. In the last few decades, a great number of researches have been done to mitigate methane emission in ruminant animals. More recently, as potential antimethanogenic additives, nitrocompounds have attracted extensive attention, and progressive and prospective advances have been achieved. In this review, the additive dietary effects of nitroethane, 2-nitroalcohol, 2-nitro-1-propanol, 3-nitrooxypropanol, 3-nitro-1-propanol, and 3-nitro-1-propionic acid were considered regarding their antimethanogenic role based on in vitro and in vivo studies. Along with this review, the possible inhibition action mode of these nitrocompounds in the rumen were discussed and summarized with the aim to provide scientific insights for mitigating methane emission in ruminant animals. Most rumen microbes have been reported to tolerate relatively high concentrations of nitrotoxins, and the nitrocompounds are considered to serve as alternative electron acceptors; their competitive consumption of reducing equivalents and the inhibitory effect on H2 and formate oxidation are currently well accepted regarding their inhibiting roles in ruminal methane production. Until now, the published data on the metabolic mechanism of the nitrocompounds mainly focus on their tolerance in ruminal systems that metabolized to major fraction of their corresponding amines and less fraction of nitrite. However, less research has been conducted to determine the metabolic fate of a diverse group of nitrocompounds biotransformed by rumen microbes. In addition, coenzyme M methyl-transferase (MTR) and methyl–coenzyme M re