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Use of dietary nitrate to increase productivity and reduce methane production of defaunated and faunated lambs consuming protein deficient chaff

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The effects of dietary nitrate supplementation and defaunation on methane (CH 4) emission, microbial protein outflow, digesta kinetics and average daily gain were studied in lambs fed chaff containing 4.1% crude protein in dry matter. Twenty ewe lambs were randomly allocated in a 2 · 2 factorial experiment (0% or 3.1% calcium nitrate supplementation and defaunated or faunated protozoal state). Nitrate supplementation increased blood methaemoglobin concentration (P < 0.05), rumen volatile fatty acids, ammonia concentration, dry matter intake, microbial protein outflow, average daily gain, dry matter digestibility, clean wool growth and wool fibre diameter (P < 0.01). Nitrate increased CH 4 production (g/day) due to greater dry matter intake, but did not affect CH 4 yield (g/kg dry matter intake). Nitrate-supplemented lambs had a shorter total mean retention time of digesta in the gut (P < 0.05). Defaunation reduced CH 4 production and CH 4 yield by 43% and 47%, but did not cause changes in dry matter intake, microbial protein outflow, average daily gain or clean wool growth. Defaunation decreased total volatile fatty acids and the molar percentage of propionate, but increased the molar percentage of acetate (P < 0.05). Interactions were observed such that combined treatments of defaunation and nitrate supplementation increased blood methaemoglobin (P = 0.04), and decreased CH 4 yield (P = 0.01).
... The effect of NPN on stimulating gas production was expected due to the lack of available N for microbial use in the basal substrate (basal substrate CP = 7.4%). Other researchers have observed that when CAN was provided as an NPN source to ewes consuming oaten chaff (4.1% CP), ruminal fermentation was increased, improving DM digestibility (Nguyen et al., 2016). Furthermore, CH 4 production was increased with the addition of CAN, which was speculated to be in relation to the increase in fermentation, and as a result, led to a reduction in CH 4 yield (g/kg of DMI; Nguyen et al., 2016). ...
... Other researchers have observed that when CAN was provided as an NPN source to ewes consuming oaten chaff (4.1% CP), ruminal fermentation was increased, improving DM digestibility (Nguyen et al., 2016). Furthermore, CH 4 production was increased with the addition of CAN, which was speculated to be in relation to the increase in fermentation, and as a result, led to a reduction in CH 4 yield (g/kg of DMI; Nguyen et al., 2016). Interestingly, when a high protein grass hay (12.9%) substrate was provided with 2.5% CAN in vitro, total gas production was reduced by 8% compared with a isonitrogenous control (Capelari and Powers, 2017) indicating a potential interaction with CAN and basal CP of the substrate. ...
Article
There is a need to increase efficiency of beef production. Decreasing losses of CH4 and improving byproduct utilization are popular strategies. Two feed additives were tested to find potential solutions. Three randomized complete block design experiments were performed using batch culture systems to evaluate the effects of bismuth subsalicylate (BSS) and calcium-ammonium nitrate (CAN) on in vitro ruminal fermentation of bahiagrass hay and supplemental molasses. The first experiment contained four treatments: (1) basal substrate; (2) basal substrate with 0.75% urea (DM basis); (3) basal substrate with 1.2% CAN and 0.38% urea (DM basis); and (4) basal substrate with 2.4% CAN (DM basis). Treatments 2, 3, and 4 were isonitrogenous. The second experiment had a 4 × 3 factorial arrangement of treatments with 4 concentrations of BSS (0.00, 0.33, 0.66, and 1.00%; DM basis) and 3 concentrations of CAN (0.0, 1.2, and 2.4%; DM basis). The third experiment had the following treatments: (1) basal substrate; (2) basal substrate with 0.05% BSS (DM basis); (3) basal substrate with 0.10% BSS (DM basis); and (4) basal substrate with 0.33% BSS (DM basis). For all experiments, basal substrate consisted of Pensacola bahiagrass hay (Paspalum notatum Flüggé; 80% substrate DM) and molasses (20% substrate DM). All data were analyzed using the MIXED procedure of SAS. In Exp. 1, in vitro organic matter (OM) digestibility (IVOMD) was linearly reduced (P
... It was hypothesized that nutrient digestibility would have been enhanced with the addition of an NPN source; however, this effect was not observed. In the current experiment, the DMI of the NCTRL steers was composed of nearly 9.8% CP, which is a drastic difference from the 4% CP oaten chaff that was provided to Merino ewes by Nguyen et al. (2016). Nguyen et al. (2016) reported that the addition of NPN in the form of calcium-ammonium nitrate increased DM digestibility by 12% along with an increase in DMI of more than 200 g/d. ...
... In the current experiment, the DMI of the NCTRL steers was composed of nearly 9.8% CP, which is a drastic difference from the 4% CP oaten chaff that was provided to Merino ewes by Nguyen et al. (2016). Nguyen et al. (2016) reported that the addition of NPN in the form of calcium-ammonium nitrate increased DM digestibility by 12% along with an increase in DMI of more than 200 g/d. The authors attributed this change in digestibility to an increase in ruminal NH 3 -N. ...
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Two randomized block designs were performed to evaluate the effects of bismuth subsalicylate (BSS) and encapsulated calcium-ammonium nitrate (eCAN) on enteric methane production, nutrient digestibility, liver mineral concentration, and performance of beef cattle consuming bahiagrass hay (Paspalum notatum; ad libitum) and sugar cane molasses [1.07 kg/d; dry matter (DM) basis]. Experiment 1, used 25 crossbred steers [335 ± 46 kg of initial body weight (BW)] with a 2 × 2 + 1 factorial arrangement of treatments for two 20 d periods. Factors were non-protein nitrogen (NPN) source (350 mg/kg BW of nitrate or 182 mg/kg BW of urea), BSS (0 or 58.4 mg/kg BW), and a negative control (NCTRL; bahiagrass hay and molasses only). Steers were re-randomized for a second period (n = 10/treatment total). Intake, apparent total tract digestibility and enteric methane were evaluated. Experiment 2 used 75 crossbred heifers in 25 pens (3 heifers/pen; 279 ± 57 kg of initial BW), consuming the same diet and treatments as Exp. 1, to determine liver mineral concentration and growth performance over 56 d. Orthogonal contrasts were used to evaluate the effects of NPN (NCTRL vs. others), source of NPN (NS; urea vs. eCAN), BSS, and NS × BSS. For Exp. 1, no interactions were observed for any variables, nor were there any effects of NPN on total-tract digestibility of nutrients, except for crude protein. Digestibility of all nutrients was reduced (P ≤ 0.021) for steers consuming eCAN compared with urea. There was no effect (P > 0.155) of BSS on digestibility of nutrients; however, BSS reduced (P = 0.003) apparent S retention. Enteric CH4 emission (g/kg BW0.75) was decreased (P = 0.051) by 11% with the addition of eCAN compared with urea. For Exp. 2, no NS×BSS interactions (P ≥ 0.251) were observed to affect liver mineral concentration; however, the addition of BSS decreased liver concentration of Cu (P = 0.002) while increasing Fe concentration (P = 0.016). There was a NS×BSS interaction (P = 0.048) where heifers consuming eCAN and BSS had lesser final BW compared with heifers consuming urea and BSS. While eCAN may be a viable resource for mitigating enteric CH4 production of forage-fed cattle, the negative effects on digestibility should be considered. Furthermore, BSS, at the amount provided, appears to have no negative effects on digestibility of nutrients in forage-fed cattle; however, there may be deleterious impacts on performance depending upon what nitrogen source is supplied.
... In addition, a shorter rumen mean retention time (MRT) and a smaller rumen volume are associated with a reduction of CH 4 emission rate in sheep (Pinares-Patiño et al., 2011a;Goopy et al., 2014). Dietary NO 3¯h as been shown to reduce total MRT and to increase microbial N outflow in sheep while reducing CH 4 emissions (Nguyen et al., 2016). Similarly, the inclusion of oils rich in polyunsaturated fatty acids in the diet of ruminants has been shown to increase microbial synthesis and non-ammonia N flow particularly when ruminal protozoal number in the rumen are reduced (Doreau and Ferlay, 1995;Ueda et al., 2003), and consequently a reduction in enteric CH 4 production is also expected (Newbold et al., 2015). ...
... Rumen NH 3 -N tended to be lost irreversibly at a greater rate in cattle fed NO 3¯-containing diets but no effects were observed on microbial growth efficiency (g MicNAN/ kg DOMI) with all values at the lower end of reported ranges (Poppi and McLennan, 2010). Feeding NO 3¯h as been shown to increase microbial N outflow in lambs fed a protein-deficient chaff (Nguyen et al., 2016) and improved NH 3 incorporation into microbial protein in dairy cattle fed a low-protein diet (Wang et al., 2018). These results suggest that NO 3¯i nclusion in the diet of ruminants may be more beneficial when dietary N is limiting. ...
Article
Nitrate and lipids have been recognized as effective dietary additives to reduce enteric methane (CH4) production. The objective of this experiment was to evaluate the effects of nitrate (NO3¯) and canola oil, alone or in combination, on enteric CH4, volatile fatty acid (VFA) concentrations, digesta kinetics and outflow of DM and microbial non-ammonia nitrogen (MicNAN) from the rumen of cattle. Four rumen-cannulated steers were used in the experiment which was designed as 4 × 4 Latin Square with four 21-d periods and four treatments. Dietary treatments consisted of a control diet (CON: 400 g/kg lucerne chaff and 600 g/kg barley grain), NO3¯ (CON + 20 g NO3¯/kg), O (CON + 50 g canola oil/kg), and NO3¯+O (CON + 20 g NO3¯/kg + 50 g canola oil/kg) with all inclusions expressed as g/kg as-fed. Exogenous markers (Co-EDTA, Yb-acetate and ¹⁵NH4Cl) were continuously infused into the rumen over 4 d to estimate digesta flow and rumen N outflow while whole tract digestibility (DMD) was determined using chromic oxide. Compared with the CON diet, feeding the NO3¯+O diet reduced (P < 0.01) methane yield (MY, g CH4/kg DMI) by 25%, daily methane production (DMP, g CH4/d) by 26% (P < 0.01) and the rumen mean retention time (MRT; P < 0.05). Nitrate containing diets reduced DMD (P < 0.01). Total VFA did not differ between treatments (P > 0.05) but NO3¯-containing diets increased acetate proportion (P < 0.01) whereas feeding the O diet increased propionate proportion (P < 0.01). Oil-containing diets reduced rumen volume (P < 0.01). The rumen protozoa concentration was reduced by including NO3¯ and canola oil alone or in combination in the diet of cattle (P < 0.05). This experiment demonstrates that feeding NO3¯+O has a synergistic effect on reducing methanogenesis from beef cattle which is consistent with NO3¯ and canola oil having complementary mechanisms for suppressing enteric CH4 production. Reducing methanogenesis by feeding NO3¯+O in this experiment did not improve the flow of MicNAN from the rumen (g MicNAN/d), microbial growth efficiency (g MicNAN/digestible organic matter intake, DOMI) or the proportion of microbial N derived from rumen NH3.
... Previous studies on sheep (Malik et al., 2017a,b;Baruah et al., 2019;Poornachandra et al., 2019) support our findings that a considerable reduction in enteric methane emissions can be attributed to the reduction in ruminal protozoa due to tanniferous phyto-sources. Further, the comparison of tannin-driven partial defaunation in this paper with the previous studies (Qin et al., 2012;Guyader et al., 2014;Nguyen et al., 2016) reported partial defaunation with other agents other than tanniferous sources also revealed a similar reduction in the enteric methane emission. Protozoa are abundant but unwanted inhabitants of the rumen (Morgavi et al., 2012). ...
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A study was conducted to investigate the impact of an anti-methanogenic product supplementation on enteric methane emissions, whole rumen metagenome and ruminal fermentation in sheep. Twelve adult male sheep were randomly divided into two groups of six animals each. Animals were fed ad libitum on a total mixed ration either without (CON) or with an anti-methanogenic supplement (Harit Dhara-HD). The anti-methanogenic supplement contained 22.1% tannic acid in a 3: 1 ratio of condensed and hydrolysable tannins. The supplementation of product revealed a significant reduction in daily enteric methane emission (21.9 vs. 17.2 g/d) and methane yield (23.2 vs. 18.2) without affecting the nutrient intake and digestibility. However, the propionate concentration in the HD treatment group was significantly higher than in the CON group. On the contrary, the ammonia nitrogen concentration was lower. The anti-methanogenic supplement significantly decreased the ruminal protozoa in the HD treatment group. Whole rumen metagenome analysis revealed that the core bacterial (Bacteroidetes and Firmicutes) and archaeal communities (Methanobrevibacter and Methanosarcina) were comparable between the CON and HD treatment groups. However, the supplementation of anti-methanogenic product led to a considerable reduction in the abundance of Proteobacteria, whereas the abundance of Lentisphaerae was greater. The supplementation significantly decreased the abundance of Methanocaldococcus, Methanococcoides, Methanocella, and Methanoregula methanogens. A total of 36 KO related to methanogenesis were identified in this study. The activities of formate dehydrogenase (EC 1.8.98.6) and tetrahydromethanopterin S-methyltransferase (EC 2.1.1.86) were significantly lowered by the anti-methanogenic product supplementation in sheep. In conclusion, the anti-methanogenic supplement has the potential to decrease enteric methane emission (~22%) at the recommended level (5% of DM) of supplementation. The contribution of minor methanogens vulnerable to supplementation to rumen methanogenesis is not known; hence, the culturing of these archaea should be taken on priority for determining the impact on overall rumen methanogenesis.
... Nitrate supplementation does not benefit animal productivity unless added to an N-deficient diet (Yang et al., 2016), as is often the case in tropical and subtropical regions. In that regard, Nguyen et al. (2016) reported an improvement with nitrate supplementation in DMI and ADG of lambs fed N-deficient chaff. ...
Article
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Ruminant livestock are an important source of anthropogenic methane (CH4). Decreasing the emissions of enteric CH4 from ruminant production is strategic to limit the global temperature increase to 1.5°C by 2050. Research in the area of enteric CH4 mitigation has grown exponentially in the last 2 decades, with various strategies for enteric CH4 abatement being investigated: production intensification, dietary manipulation (including supplementation and processing of concentrates and lipids, and management of forage and pastures), rumen manipulation (supplementation of ionophores, 3-nitrooxypropanol, macroalgae, alternative electron acceptors, and phytochemicals), and selection of low-CH4-producing animals. Other enteric CH4 mitigation strategies are at earlier stages of research but rapidly developing. Herein, we discuss and analyze the current status of available enteric CH4 mitigation strategies with an emphasis on opportunities and barriers to their implementation in confined and partial grazing production systems, and in extensive and fully grazing production systems. For each enteric CH4 mitigation strategy, we discuss its effectiveness to decrease total CH4 emissions and emissions on a per animal product basis, safety issues, impacts on the emissions of other greenhouse gases, as well as other economic, regulatory, and societal aspects that are key to implementation. Most research has been conducted with confined animals, and considerably more research is needed to develop, adapt, and evaluate antimethanogenic strategies for grazing systems. In general, few options are currently available for extensive production systems without feed supplementation. Continuous research and development are needed to develop enteric CH4 mitigation strategies that are locally applicable. Information is needed to calculate carbon footprints of interventions on a regional basis to evaluate the impact of mitigation strategies on net greenhouse gas emissions. Economically affordable enteric CH4 mitigation solutions are urgently needed. Successful implementation of safe and effective antimethanogenic strategies will also require delivery mechanisms and adequate technical support for producers, as well as consumer involvement and acceptance. The most appropriate metrics should be used in quantifying the overall climate outcomes associated with mitigation of enteric CH4 emissions. A holistic approach is required, and buy-in is needed at all levels of the supply chain.
... £ = U had greater concentration compared with UB and NITB (P < 0.05). than 160% (Nguyen et al., 2016). It is unclear why no changes in microbial N were observed in the current experiment. ...
Article
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A replicated 5 × 5 Latin square design with a 2 × 2 + 1 factorial arrangement of treatments was used to determine the effects of bismuth subsalicylate (BSS) and encapsulated calcium-ammonium nitrate (eCAN) on ruminal fermentation of beef cattle consuming bahiagrass hay (Paspalum notatum) and sugarcane molasses. Ten ruminally cannulated steers (n = 8; 461 ± 148 kg of BW; average BW ± SD) and heifers (n = 2; 337 ± 74 kg of BW) were randomly assigned to 1 of 5 treatments as follows: 2.7 g/kg of body weight (BW) of molasses (NCTRL); NCTRL + 182 mg/kg of BW of urea (U); U + 58.4 mg/kg of BW of BSS (UB); NCTRL + 538 mg/kg of BW of eCAN (NIT); and NIT + 58.4 mg/kg of BW of BSS (NITB). With the exception of NCTRL, all treatments were isonitrogenous. Beginning on d 14 of each period, ruminal fluid was collected and rectal temperature was recorded 4× per day for 3 d to determine ruminal changes every 2 h from 0 to 22 h post-feeding. Ruminal gas cap samples were collected at 0, 3, 6, 9, and 12 h on d 0 of each period followed by 0 h on d 1, 2, 3, and 14. Microbial N flow was determined using Cr-EDTA, YbCl3, and indigestible neutral detergent fiber for liquid, small particle, and large particle phases, respectively. Data were analyzed using the MIXED procedure of SAS. Orthogonal contrasts were used to evaluate the effects of non-protein nitrogen (NPN) inclusion, NPN source, BSS, and NPN source × BSS. There was no treatment effect (P > 0.05) on concentrations of H2S on d 0, 1, 2, or 14; however, on d 3, concentrations of H2S were reduced (P = 0.018) when NPN was provided. No effect of treatment (P = 0.864) occurred for ruminal pH. There was an effect of NPN source on total concentrations of VFA (P = 0.011), where a 6% reduction occurred when eCAN was provided. There were effects of NPN (P = 0.001) and NPN source (P = 0.009) on concentration of NH3-N, where cattle consuming NPN had greater concentration than those not consuming NPN, and eCAN reduced concentration compared with urea. Total concentrations of VFA and NH3-N were not affected (P > 0.05) by BSS. There was an effect of BSS (P = 0.009) on rectal temperature, where cattle not consuming BSS had greater temperatures than those receiving BSS. No differences for NPN, NPN source, nor BSS (P > 0.05) were observed for microbial N flow. In conclusion, eCAN does not appear to deliver equivalent ruminal fermentation parameters compared to urea, and BSS has limited effects on fermentation.
... In contrast to our hypothesis and to previous observations (Nakamura & Yoshida, 1991;Nguyen, Barnett, et al., 2016;Nguyen, Bremner, et al., 2016), there were no differences in blood MetHb concentrations between DEF and FAU sheep, so there was no evidence of a greater susceptibility to NO − 2 toxicity in DEF sheep in the current experiment. A possible reason for these results could be related to the inter-animal variation in NO − 3 metabolism as reported in previous findings (Bruning-Fann & Kaneene, 1993;Cockrum et al., 2010;Raphélis-Soissan, Nolan, Godwin, Newbold, Eyre, et al., 2017). ...
Article
Nitrate ( ) supplementation is an effective methane (CH4) mitigation strategy for ruminants but may produce nitrite ( ) toxicity. It has been reported that rumen protozoa have greater ability for and reduction than bacteria. It was hypothesised that the absence of ruminal protozoa in sheep may lead to higher accumulation in the rumen and a higher blood methaemoglobin (MetHb) concentration. An in vivo experiment was conducted with defaunated (DEF) and faunated (FAU) sheep supplemented with 1.8% in DM. The effects of rumen protozoa on concentrations of plasma and ruminal and , blood MetHb, ruminal volatile fatty acid (VFA) and ruminal ammonia (NH3) were investigated. Subsequently, two in vitro experiments were conducted to determine the contribution of protozoa to and reduction rates in DEF and FAU whole rumen digesta (WRD) and its liquid (LIQ) and solid (SOL) fractions, incubated alone (CON), with the addition of or with the addition of . The results from the in vivo experiment showed no differences in total VFA concentrations, although ruminal NH3 was greater (p < .01) in FAU sheep. Ruminal , and plasma concentrations tended to increase (p < .10) 1.5 hr after feeding in FAU relative to DEF sheep. In vitro results showed that reduction to NH3 was stimulated (p < .01) by incoming in both DEF and FAU relative to CON digesta. However, adding increased (p < .05) the rate of accumulation in the SOL fraction of DEF relative to both fractions of FAU digesta. Results observed in vivo and in vitro suggest that and are more rapidly metabolised in the presence of rumen protozoa. Defaunated sheep may have an increased risk of poisoning due to accumulation in the rumen.
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Ruminant livestock enteric fermentation contributes approximately one-third of the global anthropogenic methane (CH 4 ) emissions and is projected to increase significantly to meet the increasing demand for animal-sourced protein. Methane, a short-lived greenhouse gas, needs to be reduced -24 to -47% by 2050 relative to 2010 to meet the 2.0°C target. This study describes the results of a comprehensive meta-analysis to determine effective mitigation strategies. The database included findings from 425 peer-reviewed studies (1963 to 2018). Mitigation strategies were classified into three main categories [animal and feed management, diet formulation, and rumen manipulation (additives and methods used to modify the rumen)] and up to five subcategories (98 total mitigation strategy combinations). A random-effects meta-analysis weighted by inverse variance was carried out (Comprehensive Meta-Analysis, V3.3.070). Five feeding strategies, namely CH 4 inhibitors, oils and fats, oilseeds, electron sinks, and tanniferous forages, decreased absolute CH 4 emissions by on average -21% (range -12 to -35%) and CH 4 emissions per unit of product (CH 4 I; meat or milk) by on average -17% (range -12 to -32%) without negatively affecting animal production (weight gain or milk yield). Furthermore, three strategies, namely decreasing dietary forage-to-concentrate ratio, increasing feeding level, and decreasing grass maturity, decreased CH 4 I by on average -12% (range -9 to -17%) and increased animal production by on average 45% (range 9 to 162%). The latter strategies are central to meeting the increasing demand for animal-sourced food. All strategies, but CH 4 inhibitors, can be implemented now and offer immediate approaches for combating global warming.
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The European Commission asked EFSA for a scientific opinion on the risks to animal health related to nitrite and nitrate in feed. For nitrate ion, the EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) identified a BMDL 10 of 64 mg nitrate/kg body weight (bw) per day for adult cattle, based on methaemoglobin (MetHb) levels in animal's blood that would not induce clinical signs of hypoxia. The BMDL 10 is applicable to all bovines, except for pregnant cows in which reproductive effects were not clearly associated with MetHb formation. Since the data available suggested that ovines and caprines are not more sensitive than bovines, the BMDL 10 could also be applied to these species. Highest mean exposure estimates of 53 and 60 mg nitrate/kg bw per day in grass silage-based diets for beef cattle and fattening goats, respectively, may raise a health concern for ruminants when compared with the BMDL 10 of 64 mg nitrate/kg bw per day. The concern may be higher because other forages might contain higher levels of nitrate. Highest mean exposure estimates of 2.0 mg nitrate/kg bw per day in pigs' feeds indicate a low risk for adverse health effects, when compared with an identified no observed adverse effect level (NOAEL) of 410 mg nitrate/kg bw per day, although the levels of exposure might be underestimated due to the absence of data on certain key ingredients in the diets of this species. Due to the limitations of the data available, the CONTAM Panel could not characterise the health risk in species other than ruminants and pigs from nitrate and in all livestock and companion animals from nitrite. Based on a limited data set, both the transfer of nitrate and nitrite from feed to food products of animal origin and the nitrate-and nitrite-mediated formation of N-nitrosamines and their transfer into these products are likely to be negligible.
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It was hypothesised that the inclusion of nitrate (NO3–) or cysteamine hydrochloride (CSH) in a protein deficient diet (4.8% crude protein; CP) would improve the productivity of sheep while reducing enteric methane (CH4) emissions. A complete randomised designed experiment was conducted with yearling Merino sheep (n = 24) consuming a protein-deficient wheaten chaff control diet (CON) alone or supplemented with 1.8% nitrate (NO3–; DM basis), 0.098% urea (Ur, DM basis) or 80 mg cysteamine hydrochloride/kg liveweight (CSH). Feed intake, CH4 emissions, volatile fatty acids (VFA), digesta kinetics and NO3–, nitrite (NO2–) and urea concentrations in plasma, saliva and urine samples were measured. There was no dietary effect on animal performance or digesta kinetics (P > 0.05), but adding NO3– to the CON diet reduced methane yield (MY) by 26% (P = 0.01). Nitrate supplementation increased blood MetHb, plasma NO3– and NO2– concentrations (P < 0.05), but there was no indication of NO2– toxicity. Overall, salivary NO3– concentration was greater than plasma NO3– (P < 0.05), indicating that NO3– was concentrated into saliva. Our results confirm the role of NO3– as an effective additive to reduce CH4 emissions, even in a highly protein-deficient diet and as a source of additional nitrogen (N) for microbial protein synthesis via N-recycling into saliva and the gut. The role of CSH as an additive in low quality diets for improving animal performance and reducing CH4 emissions is still unclear.
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The effects of dietary nitrate and of Propionibacterium acidipropionici (PA) on methane and nitrous oxide emissions, methaemoglobinaemia, volatile fatty acid (VFA) concentration and productivity of sheep were studied. It was hypothesised that PA supplementation would increase the rate of nitrite reduction to ammonia in the rumen and therefore reduce risks of methaemoglobinaemia. Fine-wool Merino wethers (n ≤ 28; 31.8 ± 3.7 kg; 11 months of age) were acclimated to four isonitrogenous and isoenergetic diets based on oaten chaff (1.0 kg/day) supplemented with either urea (1.1% of DM; T1 and T2) or a nitrate source (2.0% of DM; T3 and T4) while T2 and T4 were also supplemented with PA (11.5 × 1010 CFU/day). Replacing urea with nitrate lowered methane production (g/day) by 19% and methane yield (g/kg DMI) by 15%, improved clean wool growth by 12% (P < 0.001) and tended to increase skin temperature (P < 0.1). Nitrate increased ruminal acetate to propionate ratio by 27%, increased plasma nitrite and nitrate concentrations and blood methaemoglobin (MetHb) level up to 45% of total haemoglobin. Nitrous oxide emission from sheep confined in respiration chambers was higher (P < 0.001) when nitrate was fed, lowering the net benefit of methane mitigation on global warming potential (CO2 equivalents/kg DMI) by 18%. In contrast, PA had little effect, decreasing total VFA concentration (P < 0.05), increasing rumen pH (P < 0.05) and clean wool growth (P < 0.05) of urea-fed sheep. This study confirmed the beneficial effects of nitrate on net greenhouse gas reduction and wool growth, but showed that methaemoglobinaemia risks may be higher when diets are fed at a restricted level and contain only low levels of readily fermented carbohydrate. PA supplementation was not effective in reducing methaemoglobinaemia, but did increase clean wool growth of urea-fed sheep.
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The purpose of this review is to discuss the risks and benefits of using supplementary nitrate to reduce enteric methane emissions in ruminants based on the results of a meta-analysis. The meta-analysis confirmed possible nitrate poisoning triggered by higher blood methemoglobin levels with increasing nitrate consumption of ruminants: methemoglobin (%) = 41.3 x nitrate [g kg(-1) body weight (BW) d(-1)] + 1.2; R-2 = 0.76, P<0.001. However, acclimatizing animals to nitrate reduced the toxicity of nitrate: methemoglobin (%) = 4.2 x nitrate (g kg(-1) BW d(-1)) + 0.4, R-2 = 0.76, P = 0.002. Animals fed nitrate reduced enteric methane emissions in a dose-response manner: methane [g kg(-1) dry matter intake (DMI)] = -8.3 x nitrate (g kg(-1) BWd(-1)) + 15.2, R-2 = 0.80, P<0.001. The reduction of enteric methane emissions due to supplementary nitrate was effective and consistent in both in vitro and in vivo studies and also persistent in several long-term studies. Dry matter intake and live weight gain (LWG) of cattle were not affected by nitrate: DMI change, R-2 = 0.007, P = 0.65; LWG change, R-2 = 0.03, P = 0.31. It is anticipated that supplementary nitrate as a substitute for urea may change urinary nitrogen composition in a manner that increases ammonia and nitrous oxide emissions from manure. Furthermore, supplementary nitrate may have various physiological roles in nitric oxide metabolism in ruminants. In conclusion, supplementary nitrate is a viable means of mitigating enteric methane emissions due to its consistent and persistent efficacy. Risk of toxicity can be lowered by gradual acclimation of animals to nitrate. However, lowered methane production may not re-direct additional metabolizable energy towards animal production.
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水素供与体併用による硝酸中毒防止の可能性を追求するため,乳酸•ギ酸塩の投与がルーメン内硝酸,亜硝酸の消失速度並びに血中MHb形成量に及ぼす影響を検討した.硝酸塩を体重1kg当り0.35または0.40g(3.5または4.0m mol),あるいはこれに水素供与体(硝酸塩の4倍モル)を併用して投与したところ,その併用によってルーメン内硝酸,亜硝酸の消失がかなり促進された.また,血中MHbは,KNO3単用の場合,投与後増加し,2~4時間後に最高値(22~34%)となり,これ以後減少したが,8時間後でも投与前の値にもどらなかった。水素供与体併用の場合は,KNO3単用にくらべ,MHbの最高値(10~16%)が低く,その減少もすみやかであり,また平常値に復するのも速い傾向が示された.なお,KNO3単用ではどの動物においても貧血様症状などが認められたが,水素供与体併用の場合は,外観上,ほとんど異常は認められないか,あるいは認められたとしても回復が速かった.以上の結果から,乳酸•ギ酸塩の併用によって中毒の危険性をかなり低下し得ると推定された.
Article
Rumen fermentation results in the production of a pool of reduced cofactors in the pathways of catabolism of organic matter within rumen microbes. These reduced cofactors are regenerated by 1) synthesis of microbial cells, 2) production of more reduced end products such as propionate and 3) saturation of unsaturated long chain fatty acids but by far the largest proportion of reduced cofactor appear to be regenerated by 4) formation of hydrogen. The concentration of hydrogen in rumen fluid negatively feeds back on the rate of fermentation and microbial growth. The rumen ecosystem has evolved to remove this hydrogen through growth of Archae that obtain energy for their growth by reducing carbon dioxide to methane and water in the rumen. Ruminal methanogenesis represents a loss of dietary energy to the animal and it is a significant greenhouse gas. Ruminants are credited with a large proportion of the methane accumulating in the world's atmosphere and a high proportion of the radiative heat forcing of greenhouse gases that have accumulated in the atmosphere. These factors have led to a global search for strategies (including nutritional intervention) to mitigate methane emission from ruminants. The use of nitrate as a hydrogen sink has been down played, due to the possible toxic effects of nitrite that under some circumstances is formed as an intermediate during the reduction of nitrate to ammonia in the rumen. A few reports have examined the potential of nitrate in vitro as a methane reducing feed additive, which appears to lower methanogenesis consistently. The rumen ecosystem and the animal need time to adapt to any fermentable N source including urea and nitrate. The requirements for minerals in different dietary conditions appear to be important in determining the microbial consortiums that use these fermentable N sources.The potential of nitrate conversion ammonia to act as a hydrogen sink in the rumen was reviewed (Leng 2008) with a clear indication emerging that it is entirely feasible that nitrate could be used as a fermentable N source by ruminants provided the rumen ecosystem was allowed to adapt over a sufficiently long period and provided certain nutritional conditions were met. In particular the availability of sulphur appears to be a crucial issue. Information derived from other microbial, anaerobic ecosystems showed that in the presence of fermentable organic matter and a source of sulphur and nitrate, nitrate reducing organisms developed that can both reduce nitrate to ammonia and oxidize sulphide to sulphate (NRSOB) without release of nitrite. At least one prominent rumen organism has this capacity (Wollinella succinogenese) and may be termed an NRSOB. Studies from the MEKARN group have demonstrated that ruminants fed low protein agro industrial byproducts can utilize nitrate as a fermentable nitrogen source. These groups have been the first to show that nitrate can be fed to ruminants safely under practical conditions and maintain or increase production. Two other groups, with the facilities to measure methane production, have concentrated on the extent to which replacing urea with nitrate salts lowers methane production. Depending on diet and inclusion rate of nitrate, the reduction in methane production has varied from 16-50%. Approximately 1 mole of nitrate in a diet reduces methane production by 10% and there is evidence of an interaction with dietary sulphur levels The major limitations to progress in using these alternative fermentable N sources that also act as high affinity electron acceptor has been the production of methaemoglobinaemia that results from nitrite generated in the rumen. The specialized nature and expensive equipment for measuring respired gases from ruminants has also become a major limitation to progress. Considerable advancement appears possible by a new approach where the ratio of methane to carbon dioxide in air receiving the ruminants breath are used to calculate the percentage lowering of methane release from the animal. This approach is possible as it is well demonstrated that where the only intervention is to replace urea with nitrate in a diet the animal's energy metabolism(carbon dioxide production) is a constant in both control(urea fed) and treatment(nitrate fed). In the present studies a modification of published methods have been used to assess the potential reductions in methane that can be achieved when providing alternative electron acceptor via nitrate in the diet and manipulation of other minerals to promote in particular nitrate reducing sulphide oxidation systems The simplistic and inexpensive requirements make this a useful approach with potential to increase the rate of progress at low cost.
Article
The effects of dietary nitrate and of urea on rumen fermentation pattern and enteric methane production were investigated using 4-month-old ewe lambs. Ten lambs were allocated into two groups (n = 5) and each group was offered one of two isonitrogenous and isoenergetic diets containing either 1.5% urea (T1) or 3% calcium nitrate (T2). Methane production was estimated using open-circuit respiration chambers after 6 weeks of feeding. No difference in nitrogen (N) balance, apparent digestibility of N or microbial N outflow existed between treatments (P>0.05). Animals offered the T2 diet lost less energy through methane than did those fed the T1 diet (P < 0.05). Total volatile fatty acid concentration, molar proportion of propionate, and the molar ratio of acetate to propionate in rumen fluid were not affected by dietary N source. Compared with urea inclusion, nitrate inclusion caused a significantly higher acetate and lower butyrate percentage in rumen volatile fatty acid. Nitrate supplementation tended to lower methane production by similar to 7.7 L/day relative to urea supplementation (P = 0.06). Methane yield (L/kg DM intake) was reduced (P < 0.05) by 35.4% when 1.5% urea was replaced by 3% calcium nitrate in the diet. Emission intensity (L methane/kg liveweight gain) was similar to 17.3% lower in the nitrate-supplemented sheep when compared with urea-fed sheep; however, the reduction was not statistically significant (P > 0.05). This study confirms that the presence of nitrate in the diet inhibits enteric methane production. As no clinical symptoms of nitrite toxicity were observed and sheep receiving nitrate-supplemented diet had similar growth to those consuming urea-supplemented diet, it is concluded that 3% calcium nitrate can replace 1.5% urea as a means of meeting ruminal N requirements and of reducing enteric methane emissions from sheep, provided animals are acclimated to nitrate gradually.
Chapter
Chemical reactions are controlled either thermodynamically or kinetically. With kinetic control, the profile of products formed depends on the substrate concentrations and enzyme activities which control de rates of synthesis for competing pathways. Thermodynamic control occurs when reactants are sufficiently limited relative to products so that the reactions cannot proceed according to the Second Law of Thermodynamics. Under these circumstances, thermodynamics control which pathway branches are available and the final concentration of products. In the rumen, glucose is readily fermented to end products including volatile fatty acids and gases. These end products are removed from the rumen slowly, suggesting that thermodynamics may affect ruminal metabolism. Our calculations show that synthesis of acetate from hydrogen and carbon dioxide is thermodynamically unfeasible in the normal rumen. Consistent with these calculations, attempts to increase acetate production by introducing acetogens into the rumen have not been fruitful unless methanogenesis was inhibited or hydrogen pressure was elevated. Addition of intermediates of propionate or butyrate synthesis increased these end products, but also increased acetate production, suggesting that intermediates may increase reaction rates in multiple directions when thermodynamically feasible. Rates of interconversion of major volatile fatty acids measured using isotopes were similar in opposing directions further suggesting that thermodynamics could play an important role in determining profiles of volatile fatty acids. Finally, a novel approach for estimating energy used for ATP production is demonstrated based on existing data and thermodynamic calculations. Although there have been no studies in which all necessary measurements were made to directly determine free energy of fermentation for different reaction pathways, preliminary research from meta-analysis with incomplete data suggests that thermodynamics may play a major role in the control of ruminal metabolic pathways.
An in vitro study was conducted to determine the effect of nitrate-nitrogen used as a sole dietary nitrogen source on ruminal fermentation characteristics and microbial nitrogen (MN) synthesis. Three treatment diets were formulated with different nitrogen sources to contain 13% CP and termed i) nitrate-N diet (NND), ii) urea-N diet (UND), used as negative control, and iii) tryptone-N diet (TND), used as positive control. The results of 24-h incubations showed that nitrate-N disappeared to background concentrations and was not detectable in microbial cells. The NND treatment decreased net production, but also decreased net production and increased net production. Total VFA concentration was lower (p