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This experiment was designed to test the effect of inclusion rate of 3-nitrooxypropanol (3-NOP), a methane inhibitor, on enteric methane emissions in dairy cows. The study was conducted with 49 multiparous Holstein cows in a randomized complete block design in 2 phases; phase 1 was with 28 cows, and phase 2 with 21 cows. Cows were fed a basal total mixed ration ad libitum and were blocked based on days in milk, milk yield, and enteric methane emissions during a 14-d covariate period. Treatments were control (no 3-NOP) and 40, 60, 80, 100, 150, and 200 mg of 3-NOP/kg of feed dry matter. Following a 14-d adaptation period, enteric gaseous emissions (methane, carbon dioxide, and hydrogen) were measured using the GreenFeed system (C-Lock Inc., Rapid City, SD) over a 3-d period. Compared with the control, inclusion rate of 3-NOP quadratically decreased daily enteric methane emissions from 22 to 40%. Maximum mitigation effect was achieved with the 3 highest 3-NOP doses (with no statistical difference among 100, 150, and 200 mg/kg). The decrease in methane emission yield and emission intensity ranged from 16 to 36% and from 25 to 45%, respectively. Emissions of hydrogen quadratically increased 6- to 10-fold, compared with the control; the maximum increase was with 150 mg/kg 3-NOP. Treatment did not affect daily emissions of carbon dioxide, but a linear increase in carbon dioxide emission yield was observed with increasing 3-NOP doses. Dry matter intake and milk yield of the cows was not affected by 3-NOP. Milk fat concentration and yield were increased by 3-NOP due to increased concentration of de novo synthetized short-chain fatty acids in milk. Inclusion of 3-NOP also tended to increase milk urea nitrogen but had no other effects on milk components. In this short-term experiment, 3-NOP decreased enteric methane emissions without affecting dry matter intake or milk yield and increased milk fat in dairy cows. Maximum mitigation effect was achieved at 100 to 200 mg/kg of feed dry matter.

This study examined the effect of 3-nitrooxypropanol (3-NOP), a substance under investigation, on enteric methane (CH4) emission, rumen fermentation, lactational performance, sensory properties of milk, and the resumption of ovarian cyclicity in early-lactation dairy cows. Fifty-six multi- and primiparous Holstein cows, including 8 that were rumen cannulated, were used in a 15-wk randomized complete block design experiment. Cows were blocked based on parity and previous lactation milk yield (MY) or predicted MY, and within each block were randomly assigned to one of 2 treatments: (1) control (CON), administered no 3-NOP, or (2) 3-NOP applied at 60 mg/kg of feed dry matter (3-NOP). Enteric CH4 emission was measured during experimental wk 2, 6, 9, and 15, using the GreenFeed system. Dry matter intake (DMI) and MY data were collected daily throughout the experiment, and milk composition samples were collected 7 times during the experiment. Milk samples were collected from 14 to 60 (±2) d after calving, 3 d per week, and assayed for progesterone concentration to determine resumption of ovarian activity. Compared with CON, 3-NOP decreased daily CH4 emission by 26%, CH4 yield (CH4 per kg of DMI) by 21%, and CH4 emission intensity [CH4 per kg of MY or energy-corrected milk (ECM)] by 25%. Enteric emission of carbon dioxide was decreased by 5%, and hydrogen emission was increased 48-fold by 3-NOP. Inclusion of 3-NOP decreased concentration of total volatile fatty acids (by 9.3%) and acetate but increased butyrate molar proportion, ethanol, and formate concentrations in ruminal fluid. Dry matter intake was lower for 3-NOP compared with CON, but DMI expressed as a percentage of body weight was not different between treatments. Treatment had no effect on milk and ECM, body weight change, or body condition score. Milk composition and milk fat and protein yields were not affected by treatment, except that concentrations of short-chain fatty acids in milk were increased by 3-NOP. Nutrient digestibility and blood metabolites and hormones were not affected by 3-NOP, except that insulin was decreased by 3-NOP. There was no effect of 3-NOP on postpartum resumption of ovarian activity, including days to first and second luteal phases, length of first and second luteal phases, and interval from first to second luteal phase. Sensory properties of milk from cows fed 3-NOP and cheese made from that milk were not affected by treatment. In this experiment, 3-NOP decreased daily enteric CH4 emission, emission yield, and emission intensity, improved feed efficiency, and did not affect lactational performance or onset of ovarian activity in early-lactation dairy cows.

The aim of this work was to determine the effect of 3-nitrooxypropanol (3-NOP) on the enteric methane (CH4) emissions and performance of lactating dairy cows when mixed in with roughage or incorporated into a concentrate pellet. After 2 pretreatment weeks without 3-NOP supplementation, 30 Holstein Friesian cows were divided into 3 homogeneous treatment groups: no additive, 3-NOP mixed in with the basal diet (roughage; NOPbas), and 3-NOP incorporated into a concentrate pellet (NOPconc). The pretreatment period was followed by a 10-wk treatment period in which the NOPbas and NOPconc cows were fed 1.6 g of 3-NOP/cow per day. After the treatment period, a 2-wk washout period followed without 3-NOP supplementation. The CH4 emissions were measured using a GreenFeed unit (C-Lock Inc., Rapid City, SD) installed in a freestall with cubicles during the entire experimental period. On average for the total treatment period and compared with the no-additive group, CH4 production (g/d) was 28 and 23% lower for NOPbas and NOPconc, respectively. Methane yield (g/kg of dry matter intake) and methane intensity (g/kg of milk) were 23 and 24% lower for NOPbas, respectively, and 21 and 22% lower for NOPconc, respectively. No differences were found between NOPbas and NOPconc. Moreover, supplying 3-NOP did not affect total dry matter intake, milk production, or milk composition. The results of this experiment show that 3-NOP can reduce enteric CH4 emissions of dairy cattle when incorporated into a concentrate pellet and that this reduction is not different from the effect of mixing in 3-NOP with the basal diet (roughage). This broadens the possibilities for using 3-NOP in the dairy sector worldwide, as it is not always feasible to provide an additive mixed in with the basal diet.

This study examined the effect of 3-nitrooxypropanol (3-NOP), an investigational substance, on enteric methane emission, milk production, and composition in Holstein dairy cows. Following a 3-wk covariate period, 48 multi- and primiparous cows averaging (± standard deviation) 118 ± 28 d in milk, 43.4 ± 8 kg/d milk yield, and 594 ± 57 kg of body weight were blocked based on days in milk, milk yield, and enteric methane emission and randomly assigned to 1 of 2 treatment groups: (1) control, no 3-NOP, and (2) 3-NOP applied at 60 mg/kg feed dry matter. Inclusion of 3-NOP was through the total mixed ration and fed for 15 consecutive weeks. Cows were housed in a freestall barn equipped with a Calan Broadbent Feeding System (American Calan Inc., Northwood, NH) for monitoring individual dry matter intake and fed ad libitum once daily. Enteric gaseous emissions (methane, carbon dioxide, and hydrogen) were measured using 3 GreenFeed (C-Lock Inc., Rapid City, SD) units. Dry matter intake, cow body weight, and body weight change were not affected by 3-NOP. Compared with the control group, 3-NOP applied at 60 mg/kg feed dry matter decreased daily methane emission, emission yield, and emission intensity by 26, 27, and 29%, respectively. Enteric emission of carbon dioxide was not affected, and hydrogen emission was increased 6-fold by 3-NOP. Administration of 3-NOP had no effect on milk and energy-corrected milk yields and feed efficiency, increased milk fat and milk urea nitrogen concentrations, and increased milk fat yield but had no other effects on milk components. Concentration of C6:0 and C8:0 and the sum of saturated fatty acids in milk fat were increased by 3-NOP. Total trans fatty acids and the sum of polyunsaturated fatty acids were decreased by 3-NOP. In this experiment, 3-NOP decreased enteric methane daily emission, yield, and intensity without affecting dry matter intake and milk yield, but increased milk fat in high-producing dairy cows.

The objective of this study was to investigate the effect of 3-nitrooxypropanol (3-NOP), an enteric methane inhibitor under investigation, on short-term dry matter intake (DMI) in lactating dairy cows. Following a 1-wk adaptation period, 12 multiparous Holstein cows were fed a basal total mixed ration (TMR) containing increasing levels of 3-NOP during 5 consecutive, 6-d periods. The experiment was conducted in a tiestall barn. Feed bins were split in half by a solid divider, and cows simultaneously received the basal TMR supplemented with the following: (1) a placebo without 3-NOP or (2) 3-NOP included in the TMR at 30, 60, 90, or 120 mg/kg of feed dry matter (experimental periods 2, 3, 4, and 5, respectively). Cows received the control diet (basal TMR plus placebo premix) during experimental period 1. A premix containing ground corn grain, soybean oil, and dry molasses was used to incorporate 3-NOP in the ration. Cows were fed twice daily as follows: 60% of the daily feed allowance at 0800 h and 40% at 1800 h. Feed offered and refused was recorded at each feeding. During the morning feedings, each cow was offered either control or 3-NOP-treated TMR at 150% of her average intake during the previous 3 d. After collection of the evening refusals, cows received only the basal TMR without the premix until the next morning feeding. The test period for the short-term DMI data collection was defined from morning feeding to afternoon refusals collection during each day of each experimental period. Location (left or right) of the control and 3-NOP diets within a feed bin was switched every day during each period to avoid feed location bias. Dry matter intake of TMR during the test period was quadratically increased by 3-NOP compared with the control. Inclusion of 3-NOP at 120 mg/kg of feed dry matter resulted in decreased 10-h DMI compared with the lower 3-NOP doses, but was similar to the control. There was no effect of feed location (left or right) within feed bin on DMI. Data from this short-term study suggests that 3-NOP does not have a negative effect on DMI in lactating dairy cows.

There is currently an urgent need for effective anti-methanogen small molecule inhibitors to help control ruminant methane emissions on a global scale. No assays system has yet been reported that would enable high-throughput screening of either rumen methanogen cultures or an assay system that utilises rumen fluid. We report here the development of a high-throughput 0.2 ml rumen fluid-based 96-well screening system that incorporates a simple substrate for fermentation with a short incubation time The fermentation parameters determined are total gas, methane and hydrogen production. The system markedly enhances the number of samples that can be processed (∼1000 incubation vials per week) compared to previously published assays. The system does not try to mimic rumen fermentation but is a means of screening compounds for their potential effect against rumen methanogens. We also assessed the system using known rumen anti-methanogen inhibitory compounds, a set of anthraquinone derivatives and 3-nitrooxypropanol. The system can differentiate between specific methane inhibition and the inhibition of overall fermentation and it discriminates between molecules that act as methanogen inhibitors and those acting as electron sinks.

The study objective was to evaluate the combined effects of supplementing monensin (MON) and the methane (CH4) inhibitor 3-nitrooxypropanol (NOP) on enteric CH4 emissions, growth rate, and feed conversion efficiency of backgrounding and finishing beef cattle. Two hundred and forty crossbred steers were used in a 238-d feeding study and fed a backgrounding diet for the first 105 d (backgrounding phase), transition diets for 28 d, followed by a finishing diet for 105 d (finishing phase). Treatments were as follows: 1) control (no additive); 2) MON (monensin supplemented at 33 mg/kg DM; 3) NOP (3-nitrooxypropanol supplemented at 200 mg/kg DM for backgrounding or 125 mg/kg DM for finishing phase); and 4) MONOP (33 mg/kg DM MON supplemented with either 200 mg/kg DM or 125 mg/kg DM NOP). The experiment was a randomized complete block (weight: heavy and light) design with 2 (NOP) × 2 (MON) factorial arrangement of treatments using 24 pens (8 cattle/pen; 6 pens/treatment) at the main feedlot and 8 pens (6 cattle/pen; 2 pens/treatment) at the controlled environment building (CEB) feedlot. Five animals per treatment were moved to chambers for CH4 measurements during both phases. Data were analyzed using a Mixed procedure of SAS with pen as experimental unit (except CH4). Location (Main vs. CEB) had no significant effect and was thus omitted from the final model. Overall, there were few interactions between MON and NOP indicating that the effects of the 2 compounds were independent. When cattle were fed the backgrounding diet, pen DMI was decreased by 7%, whereas gain-to-feed ratio (G:F) was improved by 5% with NOP supplementation (P < 0.01). Similarly, MON improved G:F ratio by 4% (P < 0.01), but without affecting DMI. During the finishing phase, DMI tended (P = 0.06) to decrease by 5% with both MON (5%) and NOP (5%), whereas ADG tended (P = 0.08) to decrease by 3% with MON. Gain-to-feed ratio for finishing cattle was improved with NOP by 3% (P < 0.01); however, no effects were observed with MON. 3-Nitrooxypropanol decreased CH4 yield (g/kg DMI) by 42% and 37% with backgrounding and finishing diets (P ≤ 0.01), respectively, whereas MON did not lower CH4 yield. Overall, these results demonstrate efficacy of NOP in reducing enteric CH4 emissions and subsequently improving feed conversion efficiency in cattle fed high-forage and high-grain diets. Furthermore, effects of NOP did not depend on whether MON was included in the diet.

This review examines the role of nutritional strategies to improve lifetime performance in ruminants. Strategies to increase ruminants' productive longevity by means of nutritional interventions provide the opportunity not only to increase their lifetime performances and their welfare, but also to decrease their environmental impact. This paper will also address how such nutritional interventions can increase herd efficiency and farm profitability. The key competencies reviewed in this article are redox balance, skeletal development and health, nutrient utilization and sustainability, which includes rearing ruminants without antibiotics and methane mitigation. While the relationships between these areas are extremely complex, a multidisciplinary approach is needed to develop nutritional strategies that would allow ruminants to become more resilient to the environmental and physiological challenges that they will have to endure during their productive career. As the demand of ruminant products from the rapidly growing human world population is ever-increasing, the aim of this review is to present animal and veterinary scientists as well as nutritionists a multidisciplinary approach towards a sustainable ruminant production, while improving their nutrient utilization, health and welfare, and mitigation of their carbon footprint at the same time.

Simple Summary 3-Nitrooxypropanol is an effective methane-mitigating feed additive. However, a decrease in feed intake is frequently observed in beef cattle fed a diet supplemented with 3-nitrooxypropanol. Thus, a study was conducted to determine the short-term preference of beef cattle offered diets supplemented with 3-nitrooxypropanol. When given a choice, the cattle initially showed less preference for a diet supplemented with 3-nitrooxypropanol, suggesting potential changes in organoleptic properties of the diet. However, the animals acclimatized to the supplemented diet rapidly such that there was no preference between a diet with and without 3-nitrooxypropanol within a week. Therefore, the change in the organoleptic properties of a diet supplemented with 3-nitrooxypropanol does not appear to be the main reason for reduced feed intake of beef cattle. Abstract Two experiments were conducted to examine eating preference of beef cattle for diets with or without the investigative enteric methane inhibitor 3-nitrooxypropanol (3-NOP). Nine beef steers were housed in individual stalls, each equipped with two feed bunks. The first experiment (Exp. 1) was conducted with a high forage diet and each animal received a diet without 3-NOP (CON) in one bunk and a diet with 3-NOP (dNOP) in the other bunk. The second study (Exp. 2) was conducted with the same animals about 6 months after Exp. 1 where a high grain diet without (CON) or with 3-NOP (dNOP) was offered. In Exp. 1, animals initially preferred CON compared with dNOP. Feed consumption from 0 to 3, 3 to 6, and 6 to 12 h after feeding was lower for dNOP compared with CON. However, dry matter intake (DMI) and feed consumption of dNOP gradually increased during Exp. 1 such that there was no preference between CON and dNOP on day 7. In Exp. 2, there was no preference for or against dNOP. Average DMI was greater for dNOP vs. CON, but interactions between diet and day for DMI and feed consumption rates indicated that daily preference between CON and dNOP was variable. In conclusion, beef steers initially detected a difference between CON and dNOP and selected in favor of CON rather than dNOP when they had not previously been exposed to 3-NOP. However, the animals rapidly acclimatized to a diet with 3-NOP (Exp. 1) and showed no eating preference between CON and dNOP within 7 days. This lack of preference was maintained throughout Exp. 2 when the same animals were fed a high grain diet.

The aim of this study was to determine the methane (CH4) mitigation potential of 3-nitrooxypropanol and the persistency of its effect when fed to dairy cows in early lactation. Sixteen Holstein-Friesian cows (all multiparous; 11 cows in their second parity and 5 cows in their third parity) were blocked in pairs, based on actual calving date, parity, and previous lactation milk yield, and randomly allocated to 1 of 2 dietary treatments: a diet including 51 mg of 3-nitrooxypropanol/kg of dry matter (3-NOP) and a diet including a placebo at the same concentration (CON). Cows were fed a 35% grass silage, 25% corn silage, and 40% concentrate (on dry matter basis) diet from 3 d after calving up to 115 d in milk (DIM). Every 4 weeks, the cows were housed in climate respiration chambers for 5 d to measure lactation performance, feed and nutrient intake, apparent total-tract digestibility of nutrients, energy and N metabolism, and gaseous exchange (4 chamber visits per cow in total, representing 27, 55, 83, and 111 DIM). Feeding 3-NOP did not affect dry matter intake (DMI), milk yield, milk component yield, or feed efficiency. These variables were affected by stage of lactation, following the expected pattern of advanced lactation. Feeding 3-NOP did not affect CH4 production (g/d) at 27 and 83 DIM, but decreased CH4 production at 55 and 111 DIM by an average of 18.5%. This response in CH4 production is most likely due to the differences observed in feed intake across the different stages of lactation because CH4 yield (g/kg of DMI) was lower (on average 16%) at each stage of lactation upon feeding 3-NOP. On average, feeding 3-NOP increased H2 production and intensity 12-fold; with the control diet, H2 yield did not differ between the different stages of lactation, whereas with the 3-NOP treatment H2 yield decreased from 0.429 g/kg of DMI at 27 DIM to 0.387 g/kg of DMI at 111 DIM. The apparent total-tract digestibility of dry matter, organic matter, neutral detergent fiber, and gross energy was greater for the 3-NOP treatment. In comparison to the control treatment, 3-NOP did not affect energy and N balance, except for a greater metabolizable energy intake to gross energy intake ratio (65.4 and 63.7%, respectively) and a greater body weight gain (average 0.90 and 0.01% body weight change, respectively). In conclusion, feeding 3-NOP is an effective strategy to decrease CH4 emissions (while increasing H2 emission) in early lactation Holstein-Friesian cows with positive effects on apparent total-tract digestibility of nutrients.

The objective of the study was to determine whether feeding a diet supplemented with 3-nitrooxypropanol (3-NOP) affects feeding behavior altering intake and rumen fermentation. Two experiments were conducted with 9 rumen-cannulated beef steers in a replicated 3 × 3 Latin square design where animals received a high-forage or high-grain diet. Treatments were 1) a basal diet (CON), the CON diet supplemented with 3-NOP (dNOP; 100 mg/kg in dietary DM or 1 g/d), or the CON diet with 3-NOP (1 g/d) infused into the rumen (infNOP). Each experimental period consisted of 14-d diet adaptation and 7-d sample collection. A 7-d washout period was provided between experiment periods. All data were analyzed as a Latin square design using Mixed Procedure of SAS. In Exp. 1 (high-forage diet), methane yield (measured by the Greenfeed system) was lowered by 18% (18.6 vs. 22.7 g/kg DMI; P < 0.01) by dNOP compared with CON. Rumen fermentation was altered similarly by both NOP treatments compared with CON where dNOP and infNOP increased (P < 0.01) rumen pH at 3 h and decreased (P < 0.01) proportion of acetate in total VFA. However, DMI, feed consumption rate (0 to 3, 3 to 6, 6 to 12, and 12 to 24 h after feeding), particle size distribution of orts, and feeding behavior (videotaped for individual animals over 48 h) were not affected by dNOP and infNOP compared with CON. In Exp. 2 (high-grain diet), methane production was not affected by dNOP or infNOP compared with CON. Dry matter intake, feed consumption rate, particle size distribution of orts, and feeding behavior were not altered by dNOP and infNOP compared with CON. However, both dNOP and infNOP affected rumen fermentation where total VFA decreased (P = 0.04) and acetate proportion in total VFA tended to decrease (P = 0.07) compared with CON. In conclusion, dietary supplementation of 3-NOP did not affect feeding behavior of beef steers fed a high-forage or high-grain diet. However, rumen fermentation was similarly changed when 3-NOP was provided in the diet or directly infused in the rumen. Thus, observed changes in rumen fermentation with 3-NOP were not due to changes in feeding behavior indicating no effects on the organoleptic property of the diets. In addition, according to small or no changes in DMI in both experiments and relatively small changes in rumen fermentation in Exp. 2, a greater dosage level of 3-NOP than 100 mg/kg (dietary DM) may need further examination of its effects on feeding behavior of beef cattle.

3-Nitrooxypropanol (NOP) is an enzymatic inhibitor that has consistently decreased enteric methane (CH4) emissions in ruminants while monensin (MON) has a moderate, and sometimes transitory, effect on CH4 decrease. We hypothesised that combining NOP and MON would result in an additive CH4 decrease. The objective was to evaluate the effect of NOP (2 mg), MON (2 mg) and the combination of NOP (2 mg) and MON (2 mg) on CH4 production using a forage-based diet (600 g/kg barley silage, 350 g/kg barley grain and 50 g/kg vitamin-mineral supplement; dry matter basis) incubated in Rusitec fermenters. The experiment included an adaptation period without treatment supplementation (8 d), a treatment period (7 d), and a recovery period where treatments were discontinued (3 d). During the treatment period CH4 production (mL/d) was decreased (P < 0.01) by 71.5, 11.8 and 69.9% with NOP, MON and NOP + MON respectively. Hydrogen gas (H2) production was increased (P < 0.01) by 66.4 and 82.5% with NOP and NOP + MON respectively. The total copy number of the 16S rRNA gene for methanogens (log10 copies/mL) in the solid fraction, obtained using quantitative PCR, was decreased (P < 0.01) by 17.0 and 21.4% for NOP and NOP + MON, respectively. During the recovery period, CH4 production remained lower than control (P < 0.01) with NOP and NOP + MON treatments; however, a gradual increase in CH4 concentration was observed after treatment withdrawal. No effect (P = 0.53) on H2 production was observed during the recovery period. In conclusion, addition of NOP and, to a lesser extent, MON, to a forage-based diet is an effective means of decreasing CH4 production in vitro; however, the combination of both did not produce an additive effect.

The study objective was to evaluate the effects of sustained reduction of enteric methane (CH) emissions with dietary supplementation of the inhibitor 3-nitrooxypropanol (NOP) on growth rate and feed conversion efficiency of growing and finishing beef cattle. Eighty-four crossbred steers were used in a 238-d feeding study and fed a backgrounding diet for the first 105 d (backgrounding phase) and transition diets for 28 d followed by a finishing diet for 105 d (finishing phase) with 3 doses of NOP (0, 100, and 200 mg/kg DM). The experiment was a completely randomized design using 21 pens (4 cattle/pen) with 7 pens per treatment. When cattle were fed the backgrounding diet, pen DMI was reduced ( < 0.01) whereas G:F tended to improve ( = 0.06) with increasing dose of NOP supplementation. During the finishing phase, DMI ( = 0.06) and ADG ( = 0.07) tended to decrease with increasing dose of NOP supplementation. Although both levels of NOP were effective in reducing CH emissions from the backgrounding diet ( < 0.01), only NOP supplemented at the highest dose was effective in reducing total CH emissions from the finishing diet ( < 0.01). Methane yield (g/kg DMI) was reduced whereas hydrogen emissions were increased at the highest dose of NOP supplementation with both backgrounding and finishing diets ( < 0.01). Overall, these results demonstrate efficacy of NOP in reducing enteric CH emissions from cattle fed backgrounding and finishing diets, and these effects were negated once NOP supplementation was discontinued.

The aim of this study was to investigate the effects of 3-nitrooxypropanol (3-NOP) and chloroform on methane (CH4) and H2 production, ruminal metabolites and microbial community structure in cattle fed a tropical forage diet. Eight rumen-fistulated steers were fed a roughage hay diet (Rhodes grass; Chloris gayana) for 31 days (control period). Four animals received the antimethanogenic compound chloroform (1.6 g chloroform–cyclodextrin/100 kg live weight (LW)) while the other four received 3-NOP (2.5 g 3-NOP/animal/day) for 21 days. Methane decrease compared with control period was similar for both treatments (30–38%) with no differences for expelled H2 between controls and treatments. Daily weight gain (DWG) was significantly increased when animals were treated with 3-NOP compared with chloroform and control. Regarding the ruminal fermentation parameters increases in ammonia, acetate and branched chain fatty acids were observed with both compounds compared with the controls. Also, methylamines, alcohols and dimethyl sulfone (DMSO2) concentrations were significantly increased with the treatments compared with control, being greater with 3-NOP. The rumen microbial analyses revealed a similar profile for both treatments, with a shift in operational taxonomic units (OTUs) assigned to the Prevotellaceae and Campylobacteraceae family. Moreover, major archaeal OTUs associated with Methanobrevibacter and Methanosphaera were significantly affected to varying extents based on the inhibitory treatments compared to the control. The abundance of the Methanobrevibacter spp. was decreased by 3-NOP and chloroform, while the Methanomassiliicoccaceae family was inhibited only by 3-NOP. The results suggest that despite the specific mode of action of 3-NOP on methanogens, inhibition of methanogenesis by both compounds resulted in similar responses in metabolism and microbial community structure in the rumen. We hypothesized that these changes were driven by the redirection of metabolic hydrogen ([H]) by both treatments. Therefore results from previous publications using chloroform as an inhibitor of methanogenesis may be useful in predicting ruminal microbiota and fermentation responses to 3-NOP.

The purpose of this study was to evaluate the effect of different doses of 3-nitrooxypropanol (NOP) to a backgrounding diet on methane (CH4) emissions using the in vitro rumen simulation technique (Rusitec). 3-Nitrooxypropanol is an enzymatic inhibitor that has consistently reduced CH4 emissions in sheep, dairy and beef cattle (up to 59% reduction on a long term basis). Two Rusitec apparatuses each equipped with 8 fermenters were used in a completely randomized block design with 2 blocks (apparatus) and 4 treatments: 0, 5, 10 and 20 mg of NOP. Within each apparatus, 2 fermenters were randomly assigned to a treatment. Treatments were supplied daily with 10 g of diet (6 g of barley silage, 3.5 g of barley grain and 0.5 g of supplement; dry matter [DM] basis). The experiment included an adaptation period without treatment supplementation (8 days) and a treatment period (7 days) with NOP addition. 3-Nitrooxypropanol did not affect dry matter (DMD; P = 0.79) or organic matter disappearance (OMD; P = 0.50) but reduced CH4 production (mL g−1 DM) by up to 86.2% (P 0.12); however, that for methanogens in the solid phase was reduced (P

The objective was to evaluate whether long-term addition of 3-nitrooxypropanol (NOP) to a beef cattle diet results in a sustained reduction in enteric CH4 emissions in beef cattle. Eight ruminally cannulated heifers (637 ± 16.2 kg BW) were used in a completely randomized design with 2 treatments: Control (0 g/d of NOP) and NOP (2 g/d of NOP). Treatments were mixed by hand into the total mixed ration (60% forage, DM basis) at feeding time. Feed offered was restricted to 65% of ad libitum DMI (slightly over maintenance energy intake) and provided once per day. The duration of the experiment was 146 d, including an initial 18-d covariate period without NOP use; a 112-d treatment period with NOP addition to the diet, divided into four 28-d time intervals (d 1 to 28, 29 to 56, 57 to 84, and 85 to 112); and a final 16-d recovery period without NOP use. During the covariate period and at the end of each interval and the end of the recovery period, CH4 was measured for 3 d using whole animal metabolic chambers. The concentration of VFA was measured in rumen fluid samples collected 0, 3, and 6 h after feeding, and the microbial population was evaluated using rumen samples collected 3 h after feeding on d 12 of the covariate period, d 22 of each interval within the treatment period, and d 8 of the recovery period. Average DMI for the experiment was 7.04 ± 0.27 kg. Methane emissions were reduced by 59.2% when NOP was used (9.16 vs. 22.46 g/kg DMI; P < 0.01). Total VFA concentrations were not affected (P = 0.12); however, molar proportion of acetate was reduced and that for propionate increased when NOP was added (P < 0.01), which reduced the acetate to propionate ratio (3.0 vs. 4.0; P < 0.01). The total copy number of the 16S rRNA gene of total bacteria was not affected (P = 0.50) by NOP, but the copy number of the 16S rRNA gene of methanogens was reduced (P < 0.01) and the copy number of the 18S rRNA gene of protozoa was increased (P = 0.03). The residual effect of NOP for most of the variables studied was not observed or was minimal during the recovery period. These results demonstrated that the addition of NOP to a diet for beef cattle caused a sustained decrease of methanogenesis, with no sign of adaptation, and that these effects were reversed once NOP addition was discontinued

The objective of this study was to evaluate the effects of 3-nitrooxypropanol (NOP), a known methane (CH) inhibitor; the ionophore monensin (MON); and their combination on in vitro CH production in a high-grain diet (85% barley grain, 10% barley silage, and 5% vitamin-mineral supplement; DM basis) using a rumen simulation technique (Rusitec). Sixteen fermentation vessels in 2 Rusitec apparatuses (blocks) were used in a completely randomized block design with 4 treatments: Control, NOP (200 µg/g DM), MON (200 µg/g DM), and the combination of 200 µg NOP/g DM and 200 µg MON/g DM (NOP + MON). Two fermenters within each apparatus were randomly assigned to a treatment. Treatments were mixed with 10 g of substrate and supplied on a daily basis. The study included an 8-d adaptation period without treatment supplementation and a 6-d period for addition of treatments. Dry matter disappearance, pH, and total VFA were not affected by treatment ( ≥ 0.34). Acetate proportion was decreased by 8.3% and 14.9% with NOP and NOP + MON ( < 0.01), respectively; however, propionate proportion was not affected by treatment ( = 0.44). The acetate to propionate ratio was lowered by 21.1% with the combination of NOP and MON ( = 0.02), whereas ammonia-N concentration was not affected by treatment ( = 0.50). Total gas production was unaffected ( = 0.50), but CH production decreased by 77.7% and 75.95% ( < 0.01) with NOP and NOP + MON addition, respectively. Concurrently, H gas production increased by 131.3% and 185.6% ( = 0.01) with NOP and NOP + MON treatments, respectively. The copy number of methanogens was decreased in both solid and liquid phases ( < 0.01) with NOP and NOP + MON treatments. Despite the combination of NOP + MON showing the greatest decrease in acetate molar proportion and acetate to propionate ratio, it did not further inhibit CH beyond the effect of NOP alone. The decrease in CH emissions with treatments that included NOP occurred along with a decrease in the copy number of methanogens associated with the solid and liquid phases, confirming the inhibitory effects of NOP on these microorganisms. In conclusion, the combined effects of NOP and MON on CH mitigation did not exceed the effect of NOP alone when using a high-grain diet in vitro.

This study evaluated if 3-nitrooxypropanol reduces enteric methane (CH4) emissions when added to the diet of beef cattle. The effects of 3-nitrooxypropanol on related variables including diet digestibility, ruminal fermentation, and ruminal microorganisms were also investigated. Eight ruminally cannulated Angus heifers (549 ± 64.3 kg [mean BW ± SD]) were fed a high forage diet (backgrounding diet) supplemented with 4 levels of 3-nitrooxypropanol (0, 0.75, 2.25 and 4.50 mg/kg BW). The experiment was designed as a duplicated 4 × 4 Latin square with 2 groups of heifers and four 28-d periods. Methane emissions were measured during 3 consecutive days using metabolic chambers. Up to a 5.8% reduction in ad libitum DMI was observed when 2.5 mg/kg BW of 3-nitrooxypropanol was fed (P = 0.03). Increasing level of 3-nitrooxypropanol linearly (P < 0.001) reduced CH4, with 33% less CH4 (corrected for DMI) at the highest level of supplementation compared with the control. Feed energy lost as CH4 was also reduced when 3-nitrooxypropanol was supplemented (P < 0.001). Molar proportion of acetate was reduced (P < 0.001) and that for propionate increased (P < 0.001) with increasing dose of 3-nitrooxypropanol, which in turn led to a reduction in the acetate to propionate ratio (P < 0.001). Total copy numbers of 16S ribosomal RNA (rRNA) genes for bacteria, methanogens, and 18S rRNA genes for protozoa in ruminal contents were not affected by 3-nitrooxypropanol supplementation (P ≥ 0.31). There was no effect of 3-nitrooxypropanol on DM (P = 0.1) digestibility in the total tract. The use of 4.5 mg/kg BW of 3-nitrooxypropanol in beef cattle consuming a backgrounding diet was effective in reducing enteric CH4 emissions without negatively affecting diet digestibility.

The objective was to measure effects of 3-nitrooxypropanol (3 NP) on methane production of lactating dairy cows and any associated changes in digestion and energy and N metabolism. Six Holstein-Friesian dairy cows in mid-lactation were fed twice daily a total mixed ration with maize silage as the primary forage source. Cows received 1 of 3 treatments using an experimental design based on two 3 × 3 Latin squares with 5-wk periods. Treatments were a control placebo or 500 or 2,500 mg/d of 3 NP delivered directly into the rumen, via the rumen fistula, in equal doses before each feeding. Measurements of methane production and energy and N balance were obtained during wk 5 of each period using respiration calorimeters and digestion trials. Measurements of rumen pH (48 h) and postprandial volatile fatty acid and ammonia concentrations were made at the end of wk 4. Daily methane production was reduced by 3 NP, but the effects were not dose dependent (reductions of 6.6 and 9.8% for 500 and 2,500 mg/d, respectively). Dosing 3 NP had a transitory inhibitory effect on methane production, which may have been due to the product leaving the rumen in liquid outflow or through absorption or metabolism. Changes in rumen concentrations of volatile fatty acids indicated that the pattern of rumen fermentation was affected by both doses of the product, with a decrease in acetate:propionate ratio observed, but that acetate production was inhibited by the higher dose. Dry matter, organic matter, acid detergent fiber, N, and energy digestibility were reduced at the higher dose of the product. The decrease in digestible energy supply was not completely countered by the decrease in methane excretion such that metabolizable energy supply, metabolizable energy concentration of the diet, and net energy balance (milk plus tissue energy) were reduced by the highest dose of 3 NP. Similarly, the decrease in N digestibility at the higher dose of the product was associated with a decrease in body N balance that was not observed for the lower dose. Milk yield and milk fat concentration and fatty acid composition were not affected but milk protein concentration was greater for the higher dose of 3 NP. Twice-daily rumen dosing of 3 NP reduced methane production by lactating dairy cows, but the dose of 2,500 mg/d reduced rumen acetate concentration, diet digestibility, and energy supply. Further research is warranted to determine the optimal dose and delivery method of the product.

The objective of the current study was to determine the effects of adding 3-nitrooxypropanol to the diet of lactating Holstein cows on methane emissions, rumen fermentation, ruminal microbial profile, and milk production. Twelve ruminally cannulated Holstein cows in midlactation were used in a crossover design study with 28-d periods. Cows were fed a diet containing 38% forage on a dry matter basis with either 2,500 mg/d of 3-nitrooxypropanol (fed as 25 g of 10% 3-nitrooxypropanol on silicon dioxide) or 25 g/d of silicon dioxide (control). After a 21-d diet adaptation period, dry matter intake (DMI) and milk yield were recorded daily. Rumen fluid and digesta were collected on d 22 and 28 for volatile fatty acid analysis and microbial profiling. Enteric methane emissions were measured on d 23 to 27 using the sulfur hexafluoride tracer gas technique. Feeding 3-nitrooxypropanol did not affect DMI; however, methane production was reduced from 17.8 to 7.18 g/kg of DMI. No change in milk or milk component yields was observed, but cows fed 3-nitrooxypropanol gained more body weight than control cows (1.06 vs. 0.39 kg/d). Concentrations of total volatile fatty acids in ruminal fluid were not affected by treatment, but a reduction in acetate proportion and a tendency for an increase in propionate proportion was noted. As such, a reduction in the acetate-to-propionate ratio was observed (2.02 vs. 2.36). Protozoa counts were not affected by treatment; however, a reduction in methanogen copy count number was observed when 3-nitrooxypropanol was fed (0.95 vs. 2.69 × 10(8)/g of rumen digesta). The data showed that feeding 3-nitrooxypropanol to lactating dairy cows at 2,500 mg/d can reduce methane emissions without compromising DMI or milk production.

The antiprotozoal effect of saponins is transitory, as when saponins are deglycosylated to the sapogenin by rumen microorganisms they become inactive. We postulated that the substitution of the sugar moiety of the saponin with small polar residues would produce sapogen-like analogs which might be resistant to degradation in the rumen as they would not be enzymatically cleaved, allowing the antiprotozoal effect to persist over time. In this study, we used an acute assay based on the ability of protozoa to break down [14C] leucine-labeled Streptococcus bovis and a longer term assay based on protozoal motility over 24 h to evaluate both the antiprotozoal effect and the stability of this effect with fifteen hederagenin bis-esters esterified with two identical groups, and five cholesterol and cholic acid based derivatives carrying one to three succinate residues. The acute antiprotozoal effect of hederagenin derivatives was more pronounced than that of cholesterol and cholic acid derivatives. Modifications in the structure of hederagenin, cholesterol, and cholic acid derivatives resulted in compounds with different biological activities in terms of acute effect and stability, although those which were highly toxic to protozoa were not always the most stable over time. Most of the hederagenin bis-esters, and in particular hederagenin bis-succinate (TSB24), hederagenin bis-betainate dichloride (TSB37) and hederagenin bis-adipate (TSB47) had a persistent effect against rumen protozoa in vitro, shifting the fermentation pattern toward higher propionate and lower butyrate. These chemically modified triterpenes could potentially be used in ruminant diets as an effective defaunation agent to, ultimately, increase nitrogen utilization, decrease methane emissions, and enhance animal production. Further trials in vivo or in long term rumen simulators are now needed to confirm the in vitro observations presented.

Ruminants, such as cows, sheep, and goats, predominantly ferment in their rumen plant material to acetate, propionate, butyrate, CO2, and methane. Whereas the short fatty acids are absorbed and metabolized by the animals, the greenhouse gas methane escapes via eructation and breathing of the animals into the atmosphere. Along with the methane, up to 12% of the gross energy content of the feedstock is lost. Therefore, our recent report has raised interest in 3-nitrooxypropanol (3-NOP), which when added to the feed of ruminants in milligram amounts persistently reduces enteric methane emissions from livestock without apparent negative side effects [Hristov AN, et al. (2015) Proc Natl Acad Sci USA 112(34):10663-10668]. We now show with the aid of in silico, in vitro, and in vivo experiments that 3-NOP specifically targets methyl-coenzyme M reductase (MCR). The nickel enzyme, which is only active when its Ni ion is in the +1 oxidation state, catalyzes the methane-forming step in the rumen fermentation. Molecular docking suggested that 3-NOP preferably binds into the active site of MCR in a pose that places its reducible nitrate group in electron transfer distance to Ni(I). With purified MCR, we found that 3-NOP indeed inactivates MCR at micromolar concentrations by oxidation of its active site Ni(I). Concomitantly, the nitrate ester is reduced to nitrite, which also inactivates MCR at micromolar concentrations by oxidation of Ni(I). Using pure cultures, 3-NOP is demonstrated to inhibit growth of methanogenic archaea at concentrations that do not affect the growth of nonmethanogenic bacteria in the rumen.

The objective of this study was to compare 2 commonly used techniques for measuring methane emissions from ruminant animals: the GreenFeed (GF) system and the sulfur hexafluoride (SF6) technique. The study was part of a larger experiment in which a methane inhibitor, 3-nitrooxypropanol, fed at 4 application rates (0, 40, 60, and 80 mg/kg of feed dry matter) decreased enteric methane emission by an average of 30% (measured by both GF and SF6) in a 12-wk experiment with 48 lactating Holstein cows fed a total mixed ration. The larger experiment used a randomized block design and was conducted in 2 phases (February to May, phase 1, and June to August, phase 2), with 2 sets of 24 cows in each phase. Using both GF and SF6 techniques, methane emission data were collected simultaneously during experimental wk 2, 6, and 12 (phase 1) and 2, 9, and 12 (phase 2), which corresponded to a total of 6 sampling periods. During each sampling period, 8 spot samples of gas emissions (staggered over a 3-d period) were collected from each cow using GF, as well as 3×24-h collections using the SF6 technique. Methane emission data were averaged per cow for the statistical analysis. The mean methane emission was 373 (standard deviation=96.3) and 405 (standard deviation=156) g/cow per day for GF and SF6, respectively. Coefficients of variation for the 2 methods were 25.8 and 38.6%, respectively; correlation and concordance between the 2 methods were 0.40 and 0.34, respectively. The difference in methane emission between the 2 methods (SF6 - GF) within treatment was from 46 to 144 and 24 to 27 g/d for phases 1 and 2, respectively. In the conditions of this experiment, the SF6 technique produced larger variability in methane emissions than the GF method. The overall difference between the 2 methods was on average about 8%, but was not consistent over time, likely influenced by barn ventilation and background methane and SF6 concentrations.

The objective of this study was to evaluate the effect of exogenous amylase supplementation on gas production and on in vitro rumen starch degradability (IVSD) of different sized particles of corn and barley meals (Cm and Bm, respectively). An aqueous liquid amylase formulation from Bacillus licheniformis was tested at 3 enzyme doses (EnzD; 0, 300 and 1,500 kilo novo units/kg of dry matter) on small (

Ruminants, such as cows, sheep, and goats, predominantly ferment in their rumen plant material to acetate, propionate, butyrate, CO, and methane. Whereas the short fatty acids are absorbed and metabolized by the animals, the greenhouse gas methane escapes via eructation and breathing of the animals into the atmosphere. Along with the methane, up to 12% of the gross energy content of the feedstock is lost. Therefore, our recent report has raised interest in 3-nitrooxypropanol (3-NOP), which when added to the feed of ruminants in milligram amounts persistently reduces enteric methane emissions from livestock without apparent negative side effects [Hristov AN, et al. (2015) Proc Natl Acad Sci USA 112(34):10663-10668]. We now show with the aid of in silico, in vitro, and in vivo experiments that 3-NOP specifically targets methyl-coenzyme M reductase (MCR). The nickel enzyme, which is only active when its Ni ion is in the+1 oxidation state, catalyzes the methane-forming step in the rumen fermentation. Molecular docking suggested that 3-NOP preferably binds into the active site of MCR in a pose that places its reducible nitrate group in electron transfer distance to Ni(I). With purified MCR, we found that 3-NOP indeed inactivates MCR at micromolar concentrations by oxidation of its active site Ni(I). Concomitantly, the nitrate ester is reduced to nitrite, which also inactivates MCR at micromolar concentrations by oxidation of Ni(I). Using pure cultures, 3-NOP is demonstrated to inhibit growth of methanogenic archaea at concentrations that do not affect the growth of nonmethanogenic bacteria in the rumen., We thank Peter Livant (Auburn University), Elisabeth Jimenez (Consejo Superior de Investigaciones Cientificas), John Wallace (University of Aberdeen), and Jamie Newbold (Aberystwyth University) for the use of the gas chromatograph, for the in vitro culture work, and for providing stock pure cultures, respectively; Ulrich Ermler and the staff of the PXII beam line at Swiss Light Source (Villigen, Switzerland) for helping with the X-ray data collection; and David Rinaldo (Schrödinger, LLC) for molecular modeling support.

Currently research on feed supplementation with natural compounds to improve energy and protein utilisation and to mitigate the greenhouse gas methane in ruminants is intensively pursued. Two compounds, diallyl disulphide (DADS), an important component of garlic oil, and lovastatin, an inhibitor of a key enzyme of methanogenic Archaea, were selected on the basis of their in vitro anti-methanogenic potential. In three 23-day experimental runs, six sheep received hay and concentrate in a duplicate 3 x 3 Latin square design. The concentrate was either not supplemented or supplemented with either 4 g DADS or 80 mg lovastatin per kg of total dietary dry matter. There were no refusals of concentrate for any treatment. Respiratory measurements were conducted on experimental days 7/8 (Period 1) and days 17/18 (Period 2). Relative to the control, digestibility of neutral detergent fibre (NDF) tended to increase (p = 0.09) with DADS by 14%. This was associated with an increased (p = 0.07) body energy retention of the animals. Effects on nitrogen balance and ruminal fermentation traits were never significant. No influence of supplements or period was found on total daily CH4 production which averaged at 28.6 g per sheep. However, across both periods the amount of CH4 produced per kg NDF digested was lower (-8%; p = 0.02) with DADS than without supplementation, and the lovastatin treatment ranged in between. In conclusion, the study demonstrated a certain potential of DADS to improve fibre digestion and body energy retention and to limit CH4 formation in relation to digestible fibre intake, while lovastatin remained ineffective.

British Journal of Nutrition, 106 (1), ISSN:0007-1145, ISSN:1475-2662

Aspergillus fumigatus is the major cause of invasive aspergillosis (IA),a disease associated with high rates of morbidity and mortality in patientsundergoing treatment for haematological malignancies. This study investigated A. fumigatus growth in vitro and in a murine model of IA inorder to provide insights into the dynamics of extracellular DNA and galactomannan (GM)release and their relevance to early diagnosis of IA. Following inoculationof whole blood with 20 A. fumigatus conidia ml−1,DNA that corresponded to the inoculum could be detected by PCR but GM wasnot detected in plasma separated from the blood sample, indicating that thefungus did not grow in whole blood. The quantities of DNA detected by PCR,and GM, were proportional to the amount of fungal biomass present in vitro. Fungal DNA could be detected in the sera of mice experimentally infectedwith A. fumigatus with maximum detection in cyclophosphamide-treatedmice.

The objective of the present study was to determine the dose response of the methane (CH4) inhibitor 3-nitrooxypropanol (NOP) on enteric CH4 production and dry matter intake (DMI) for beef cattle fed a high-forage or high-grain diet. Fifteen crossbred yearling steers were used in two consecutive studies (high-forage backgrounding, high-grain finishing), each designed as an incomplete block with two 28-day periods with a 7-day washout in between and treatments corresponding to six doses of NOP (0 (Control), 50, 75, 100, 150, 200 mg/kg DM). The NOP was provided in the ration daily with the dose increased gradually over the first 10 days of each period. No treatment effects were observed on overall DMI or DMI of cattle when they were in the chambers either for the high-forage (P ≥ 0.54) or high-grain (P ≥ 0.26) diet. With the high-forage diet, NOP supplementation lowered total CH4 emissions (g/day) (P = 0.05), with the response at 200 mg NOP/kg DM different from Control (P < 0.05). Similarly, CH4 emissions corrected for DMI (g/kg DMI) and as a percentage of gross energy intake were linearly reduced in the high-forage diet with supplemental NOP (P < 0.01) and responses observed at 100, 150 and 200 mg NOP/kg DM differed from Control (P < 0.05). For the high-grain diet, total CH4 emissions decreased with incremental increases in the concentration of NOP supplemented (P = 0.04) and responses observed at 150 and 200 mg/kg DM differed from Control. Similarly, linear responses were observed with CH4 emissions corrected for DMI (P = 0.04) and gross energy intake (P = 0.02), with 100–200 mg NOP/kg DM differing from Control. Overall, results from the present study demonstrated that for beef cattle fed high-forage and high-grain diets, supplementation of 100–200 mg NOP/kg DM lowered enteric CH4 emissions without inducing any negative effects on DMI.

The objective of this crossover experiment was to investigate the effect of a methane inhibitor, 3-nitrooxypropanol (3NOP), on enteric methane emission, methane isotopic composition, and rumen fermentation and microbial profile in lactating dairy cows. The experiment involved 6 ruminally cannulated late-lactation Holstein cows assigned to 2 treatments: control and 3NOP (60 mg/kg of feed dry matter). Compared with the control, 3NOP decreased methane emission by 31% and increased hydrogen emission from undetectable to 1.33 g/d. Methane emissions per kilogram of dry matter intake and milk yield were also decreased 34% by 3NOP. Milk production and composition were not affected by 3NOP, except milk fat concentration was increased compared with the control. Concentrations of total VFA and propionate in ruminal fluid were not affected by treatment, but acetate concentration tended to be lower and acetate-to-propionate ratio was lower for 3NOP compared with the control. The 3NOP decreased the molar proportion of acetate and increase those of propionate, butyrate, valerate, and isovalerate. Deuterium-to-hydrogen ratios of methane and the abundance of (13)CH3D were similar between treatments. Compared with the control, minor (4‰) depletion in the (13)C/(12)C ratio was observed for 3NOP. Genus composition of methanogenic archaea (Methanobrevibacter, Methanosphaera, and Methanomicrobium) was not affected by 3NOP, but the proportion of methanogens in the total cell counts tended to be decreased by 3NOP. Prevotella spp., the predominant bacterial genus in ruminal contents in this experiment, was also not affected by 3NOP. Compared with the control, Ruminococcus and Clostridium spp. were decreased and Butyrivibrio spp. was increased by 3NOP. This experiment demonstrated that a substantial inhibition of enteric methane emission by 3NOP in dairy cows was accompanied with increased hydrogen emission and decreased acetate-to-propionate ratio; however, neither an effect on rumen archaeal community composition nor a significant change in the isotope composition of methane was observed.

A quarter of all anthropogenic methane emissions in the United States are from enteric fermentation, primarily from ruminant livestock. This study was undertaken to test the effect of a methane inhibitor, 3-nitrooxypropanol (3NOP), on enteric methane emission in lactating Holstein cows. An experiment was conducted using 48 cows in a randomized block design with a 2-wk covariate period and a 12-wk data collection period. Feed intake, milk production, and fiber digestibility were not affected by the inhibitor. Milk protein and lactose yields were increased by 3NOP. Rumen methane emission was linearly decreased by 3NOP, averaging about 30% lower than the control. Methane emission per unit of feed dry matter intake or per unit of energy-corrected milk were also about 30% less for the 3NOP-treated cows. On average, the body weight gain of 3NOP-treated cows was 80% greater than control cows during the 12-wk experiment. The experiment demonstrated that the methane inhibitor 3NOP, applied at 40 to 80 mg/kg feed dry matter, decreased methane emissions from high-producing dairy cows by 30% and increased body weight gain without negatively affecting feed intake or milk production and composition. The inhibitory effect persisted over 12 wk of treatment, thus offering an effective methane mitigation practice for the livestock industries.

The objective of this study was to determine the effects of feeding 3-nitrooxypropanol (NOP) in the total mixed ration of lactating Holstein cows on rumen fermentation, ruminal microbial population, enteric methane production, milk production, nutrient digestibility, and blood metabolites. Fifteen ruminally cannulated Holstein cows in mid to late lactation were used in a 3 × 3 Latin square design study with 28-day periods. Cows were fed a 60%-forage diet (dry matter basis) with 2500 (HIGH), 1250 (LOW) or 0 (CON) mg/day of NOP. After a 20-day diet adaptation period, dry matter intake (DMI) and milk yield were recorded daily. Rumen digesta and rumen fluid were collected on Days 21 and 28 and ruminal pH was determined on Days 23–28. Methane emissions were measured on Days 23–27 using the sulfur hexafluoride tracer gas technique. Faecal and blood samples were taken on Days 25–27. Feeding NOP at either dose did not affect DMI, milk production or bodyweight gain. Total concentration of volatile fatty acids in rumen fluid did not differ; however, there was a decrease in molar proportion of acetate and increase in molar proportion of propionate with feeding NOP in a dose-dependent manner. Microbial profile and ruminal pH were not affected by treatment. Apparent total-tract digestibility of DM (62.7% vs 58.4%; P < 0.05) and neutral detergent fibre (38.0% vs 30.7%; P < 0.05) were increased with the HIGH dose compared with CON. Feeding NOP reduced methane yield from 19.9 to 15.3 g/kg DMI for CON versus LOW (P < 0.05) and from 19.9 to 12.6 for CON versus HIGH (P < 0.05). Feeding NOP at 1250 or 2500 mg/day reduced methane yield and affected ruminal volatile fatty acid profile without compromising DMI or apparent total-tract nutrient digestibility.

Cattle husbandry is a major contributor to atmospheric methane, which is considered as an important greenhouse gas. Moreover, the generation of methane in the intestine of domestic ruminants by methanogenic bacteria is a drag on feed efficacy. Studies on methanogenesis have typically implied model organisms that are, however, not relevant in the ruminant gut. This paper shows that methyl-CoM reductase catalyzing the final step of methanogenesis in Methanobrevibacter ruminantium, a major participant in methane production by cattle, is inhibited by 2-bromoethanesulfonate, a compound often used as a model in animal agriculture, with an apparent IC50 of 0.4 ± 0.04 μM.

International audience; The aim of this work was to investigate the effect of feeding ethyl-3-nitrooxy propionate (E3NP) and 3-nitrooxypropanol (3NP), 2 recently developed compounds with potential antimethanogenic activity, in vitro and in vivo in nonlactating sheep on ruminal methane production, fermentation pattern, the abundance of major microbial groups, and feed degradability. Three experiments were conducted, 1 in vitro and 2 in vivo. The in vitro batch culture trial (experiment 1) tested 2 doses of E3NP and 3NP (40 and 80μL/L), which showed a substantial reduction of methane production (up to 95%) without affecting concentration of volatile fatty acids (VFA). The 2 in vivo trials were conducted over 16 d (experiment 2) and 30 d (experiment 3) to study their effects in sheep. In experiment 2, 6 adult nonpregnant sheep, with permanent rumen cannula and fed alfalfa hay and oats (60:40), were treated with E3NP at 2 doses (50 and 500mg/animal per day). After 7, 14, and 15 d of treatment, methane emissions were recorded in respiration chambers and rumen fluid samples were collected for VFA analysis and quantification of bacterial, protozoal, and archaeal numbers by real-time PCR. Methane production decreased by 29% compared with the control with the higher dose of E3NP on d 14 to 15. A decrease in the acetate:propionate ratio was observed without detrimental effects on dry matter intake. In experiment 3, 9 adult nonpregnant sheep, with permanent rumen cannula and fed with alfalfa hay and oats (60:40), were treated with E3NP or 3NP at one dose (100mg/animal per day) over 30 d. On d 14 and d 29 to 30, methane emissions were recorded in respiration chambers. Rumen fluid samples were collected on d 29 and 30 for VFA analysis and quantification of bacterial, protozoal, and archaeal numbers by real-time PCR. In addition, on d 22 and 23, samples of oats and alfalfa hay were incubated in the rumen of sheep to determine dry matter ruminal degradation over 24 and 48h, respectively; no effect was observed (78.6, 78.3, and 78.8% of alfalfa and 74.2, 74.0, and 70.6% of oats in control, E3NP, and 3NP groups, respectively). A reduction in methane production was observed for both additives at d 14 and d 29 to 30. In both treatments, the acetate:propionate ratio was significantly decreased. Likewise, total concentrations of the analyzed microbial groups in the rumen showed no difference among treatments and doses for both experiments. Both tested compounds showed promise as methane inhibitors in the rumen, with no detrimental effects on fermentation or intake, which would need to be confirmed in lactating animals