Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds.
Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds.
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DOI：
10.3389/fmicb.2016.00228
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发表时间：
2016
影响因子：
5.2
通讯作者：
Nisbet DJ
中科院分区：
文献类型：
--
作者：
Latham EA;Anderson RC;Pinchak WE;Nisbet DJ
硝酸盐和某些短链硝基化合物和硝基氧化合物正在被研究作为膳食补充剂，以减少与瘤胃甲烷排放相关的经济和环境成本。在热力学上，硝酸盐是瘤胃中优选的电子受体，其在异化还原为中间体亚硝酸盐期间以产甲烷为代价消耗电子，亚硝酸盐主要还原为氨，尽管也可能产生少量的一氧化二氮。短链硝基化合物作为产甲烷细菌的直接抑制剂，尽管这些化合物中的某些也可能以产甲烷为代价消耗电子，并且是重要食源性病原体的有效抑制剂。将硝酸盐掺入反刍动物饮食中的微生物和营养后果通常导致乙酸盐产量增加。与大多数其他甲烷抑制补充剂不同，硝酸盐减少或对丙酸盐的产生没有影响。添加的硝酸盐的类型影响硝酸盐还原的速率、亚硝酸盐积累的速率和甲烷还原的功效，其中钠盐和钾盐比硝酸钙盐更有效。在反刍动物日粮中添加硝基化合物的消化结果更易变，在某些情况下可能会增加丙酸盐的产生。对硝酸盐的中间产物亚硝酸盐对反刍动物的毒性的关注需要管理，因为动物中毒可能通过高铁血红蛋白血症发生。某些天然存在的硝基化合物，如3-硝基-1-丙酸酯或3-硝基-1-丙醇也会引起中毒，但通过抑制琥珀酸脱氢酶。避免亚硝酸盐毒性的典型风险管理程序包括使动物逐渐适应更高浓度的硝酸盐和亚硝酸盐，这也可能与硝基化合物一起使用。许多负责瘤胃中硝酸盐代谢的生物体已被表征。到目前为止，一个单一的瘤胃细菌被确定为显着的硝基化合物代谢的贡献。适当剂量的硝基化合物和硝酸盐，单独或与选择用于亚硝酸盐和硝基化合物解毒活性的益生菌组合，有望减轻毒性风险。需要进一步研究，以更清楚地界定这些技术的好处和风险，使其适合畜牧生产者销售。
Nitrate and certain short chain nitrocompounds and nitro-oxy compounds are being investigated as dietary supplements to reduce economic and environmental costs associated with ruminal methane emissions. Thermodynamically, nitrate is a preferred electron acceptor in the rumen that consumes electrons at the expense of methanogenesis during dissimilatory reduction to an intermediate, nitrite, which is primarily reduced to ammonia although small quantities of nitrous oxide may also be produced. Short chain nitrocompounds act as direct inhibitors of methanogenic bacteria although certain of these compounds may also consume electrons at the expense of methanogenesis and are effective inhibitors of important foodborne pathogens. Microbial and nutritional consequences of incorporating nitrate into ruminant diets typically results in increased acetate production. Unlike most other methane-inhibiting supplements, nitrate decreases or has no effect on propionate production. The type of nitrate salt added influences rates of nitrate reduction, rates of nitrite accumulation and efficacy of methane reduction, with sodium and potassium salts being more potent than calcium nitrate salts. Digestive consequences of adding nitrocompounds to ruminant diets are more variable and may in some cases increase propionate production. Concerns about the toxicity of nitrate's intermediate product, nitrite, to ruminants necessitate management, as animal poisoning may occur via methemoglobinemia. Certain of the naturally occurring nitrocompounds, such as 3-nitro-1-propionate or 3-nitro-1-propanol also cause poisoning but via inhibition of succinate dehydrogenase. Typical risk management procedures to avoid nitrite toxicity involve gradually adapting the animals to higher concentrations of nitrate and nitrite, which could possibly be used with the nitrocompounds as well. A number of organisms responsible for nitrate metabolism in the rumen have been characterized. To date a single rumen bacterium is identified as contributing appreciably to nitrocompound metabolism. Appropriate doses of the nitrocompounds and nitrate, singly or in combination with probiotic bacteria selected for nitrite and nitrocompound detoxification activity promise to alleviate risks of toxicity. Further studies are needed to more clearly define benefits and risk of these technologies to make them saleable for livestock producers.