Effects of nitrate adaptation by rumen inocula donors and substrate fiber proportion on in vitro nitrate disappearance, methanogenesis, and rumen fermentation acid

Lin, Maojuan; Schaefer, D.M.; Meng, Qingxiang

doi:10.1017/s1751731113000116

Cited by 17 publications

(16 citation statements)

References 25 publications

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“…Dietary interventions such as high starch and cereal grains have been proposed to help mitigate nitrate toxicity (Burrows et al, 1987 ; Hibberd et al, 1994 ) purportedly by stimulating the metabolism of ruminal microorganisms thereby promoting production and subsequent availability of electron-donating substrates for nitrate and nitrite metabolism (Lewis, 1950 , 1951 ; Allison and Reddy, 1984 ). High starch diets, within a pH range of about 6.6–6.8, have been shown to increase hydrogen production by mixed populations of ruminal microbes in vitro (Lin et al, 2013b ). However, high starch diets are also well established to decrease rumen pH, which could potentially create an environment inhibitory to ruminal nitrate and nitrite metabolism.…”

Section: Factors That Influence Nitrate and Nitrocompound Metabolismmentioning

confidence: 99%

Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds

Latham

Anderson

Pinchak³

et al. 2016

Front. Microbiol.

107

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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.

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Section: Factors That Influence Nitrate and Nitrocompound Metabolismmentioning

confidence: 99%

Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds

Latham

Anderson

Pinchak³

et al. 2016

Front. Microbiol.

107

View full text Add to dashboard Cite

show abstract

“…Nitrate has been evaluated in a number of methanogenesis studies both in vitro ( Sar et al, 2005b , c ; Leng, 2008 ; Guo et al, 2009 ; Lin et al, 2011 , 2013b ; Shi et al, 2012 ; Patra and Yu, 2013 ) and in vivo ( Nolan et al, 2010 ; Morgavi et al, 2010 ; van Zijderveld et al, 2010 , 2011a ; Hulshof et al, 2012 ; Li et al, 2013 ; Lee and Beauchemin, 2014 ; Newbold et al, 2014 ). The results have been among the most promising of all the interventions investigated to date ( Hristov et al, 2013a ), yet variations in response, e.g., in relation to the basal diet ( Troy et al, 2015 ), are difficult to explain (see the excellent review by Lee and Beauchemin, 2014 ), particularly in microbiological terms.…”

Section: Mitigation Of Methane Emissions and Possible Role For Nitratmentioning

confidence: 99%

“…Several major factors influence the toxicity of nitrite derived from nitrate ( Leng, 2008 ; Lin et al, 2013b ): (i) high nitrate concentrations in the diet, (ii) the rate of feed consumption, (iii) low rates of nitrite reduction to ammonia in the rumen, and (iv) slow rumen passage rate, resulting in longer nitrate, or nitrite retention in the rumen. In vivo studies have been careful to increase the dietary nitrate content gradually over a period of weeks to allow the rumen microbiota to adapt and for metabolism of nitrite to increase ( Alaboudi and Jones, 1985 ; Nolan et al, 2010 ; van Zijderveld et al, 2010 , 2011b ).…”

Section: Nitrate Metabolism In the Rumen And Nitrite Toxicitymentioning

confidence: 99%

“…In vivo studies have been careful to increase the dietary nitrate content gradually over a period of weeks to allow the rumen microbiota to adapt and for metabolism of nitrite to increase ( Alaboudi and Jones, 1985 ; Nolan et al, 2010 ; van Zijderveld et al, 2010 , 2011b ). These enhanced nitrite reduction rates are of prime importance for increased safety with high-nitrate diets ( Lin et al, 2013b ). It could be speculated that nitrite, rather than nitrate, might be a better compound to use to induce this adaptation, because nitrate itself will enrich for enhanced nitrate reduction as well, but we were unable to find any published evidence of nitrite having been used in this way.…”

Section: Nitrate Metabolism In the Rumen And Nitrite Toxicitymentioning

confidence: 99%

“…There is a need to establish minimum conditions for successful adaptation to nitrate-containing diets. During adaptation, the rates of nitrate and nitrite reduction ( Alaboudi and Jones, 1985 ; Lin et al, 2013a ), activity of nitrate reductase ( Asanuma et al, 2015 ) and numbers of nitrate-reducing bacteria increase ( Lin et al, 2013b ). However, the rate of nitrite reduction remains less than that of nitrate reduction, thus still favoring nitrite accumulation.…”

Section: Improving the Safety And Efficacy Of Nitrate Supplementationmentioning

confidence: 99%

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Nitrate and Inhibition of Ruminal Methanogenesis: Microbial Ecology, Obstacles, and Opportunities for Lowering Methane Emissions from Ruminant Livestock

et al. 2016

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Ruminal methane production is among the main targets for greenhouse gas (GHG) mitigation for the animal agriculture industry. Many compounds have been evaluated for their efficacy to suppress enteric methane production by ruminal microorganisms. Of these, nitrate as an alternative hydrogen sink has been among the most promising, but it suffers from variability in efficacy for reasons that are not understood. The accumulation of nitrite, which is poisonous when absorbed into the animal’s circulation, is also variable and poorly understood. This review identifies large gaps in our knowledge of rumen microbial ecology that handicap the further development and safety of nitrate as a dietary additive. Three main bacterial species have been associated historically with ruminal nitrate reduction, namely Wolinella succinogenes, Veillonella parvula, and Selenomonas ruminantium, but others almost certainly exist in the largely uncultivated ruminal microbiota. Indications are strong that ciliate protozoa can reduce nitrate, but the significance of their role relative to bacteria is not known. The metabolic fate of the reduced nitrate has not been studied in detail. It is important to be sure that nitrate metabolism and efforts to enhance rates of nitrite reduction do not lead to the evolution of the much more potent GHG, nitrous oxide. The relative importance of direct inhibition of archaeal methanogenic enzymes by nitrite or the efficiency of capture of hydrogen by nitrate reduction in lowering methane production is also not known, nor are nitrite effects on other members of the microbiota. How effective would combining mitigation methods be, based on our understanding of the effects of nitrate and nitrite on the microbiome? Answering these fundamental microbiological questions is essential in assessing the potential of dietary nitrate to limit methane emissions from ruminant livestock.

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