Sulfur Hexafluoride Tracer Research Articles

Effect of enriched biochar on methane emissions, rumen microbial structure and rumen fermentation characteristics in Holstein steers

Nutritional strategies, such as oil inclusion or addition of 3-Nitrooxypropanol, to reduce methane emissions from ruminants show promise, but have not been as effective in low quality or roughage based diets. The objective of this study was to investigate the effect of enriched biochar on methane production and fermentation characteristics in an oaten hay diet. This study used a 3 × 3 Latin square design, where 3 fistulated Holstein steers (790 ± 100 kg initial body weight) were fed a basal diet of oaten hay, with either 1) oaten pellets (Control), 2) Oaten pellets containing biochar at 1% of dietary DM; or 3) Oaten pellets containing enriched biochar at 1% DM. Each period lasted for 21 d, including 14 d dietary adaptation and 7 d experimental measurement. Rumen samples were collected on d 17-21 for determination of liquid and solid associated microbes, and rumen fermentation characteristics. The sulphur hexafluoride (SF6) tracer technique was used to quantify methane emissions. Body weights (kg), dry matter and organic matter intakes (DMI and OMI), methane production (g/d), methane intensity (g/kg BW) and methane yield (g/kg DMI) were similar (P ≥ 0.12) across the three treatment groups. Similarly, total VFA concentration and individual percentages of VFA were similar across treatments (P ≥ 0.16). Microbes in the solid and liquid fractions showed little differences among treatments (P≤0.049) indicating that biochar included in an oaten hay diet, whether standard or enriched, had little effect on rumen fermentation, microbial communities or methane emissions in Holstein steers.

SF6 Tracer Technique to Estimate Methane Emission in a Dual-Flow Continuous Culture System: Test and Application

This study aimed to evaluate the sulfur hexafluoride (SF6) tracer technique for estimating methane (CH4) emissions in dual-flow continuous culture systems (DFCCS). In experiment 1 (Exp1), fermenters were filled with water, and known CH4 concentrations (0, 1.35, 2.93, or 4.43 g/d) were injected using permeation tubes with SF6 release rates (3.30 or 9.65 mg/d). Headspace gas was collected using canisters, and the SF6 technique estimated CH4 recovery. Experiment 2 (Exp2) involved a DFCCS fermentation trial with ruminal fluid from three Holstein cows, testing diets with soybean meal or its partial replacement (50%) by Chlorella or Spirulina. Headspace gas was collected at intervals post-feeding. Standard curves for SF6 and CH4 quantification were inadequate for DFCCS samples, with the CH4:SF6 ratio differing from standards, indicating the data needs further SF6 release rate evaluation. In Exp1, a high correlation (r = 0.97) was found between infused and calculated CH4, indicating good repeatability. Low and high SF6 rates performed similarly at low CH4 infusion, but high SF6 overestimated CH4 at high infusion. Exp2 showed CH4 emissions irrespective of SF6 rate and indicated reduced CH4 emissions and increased NDF degradation with algae-containing diets. Further evaluation of the SF6 tracer technique is warranted for DFCCS.

Evaluation of increasing levels of condensed tannin extracted from Acacia mearnsii on performance, carcass traits, meat quality, methane emission, and health of finishing Nellore bulls

The objective of this study was to evaluate the impact of increasing levels of condensed tannin extracted from Acacia mearnsii on the performance, carcass traits, meat quality, methane (CH4) emissions, and health of finishing Nellore bulls in a feedlot system. Eighty 20-month-old Nellore bulls (426.7 ± 24.46 kg of body weight (BW)) were individually housed with ad libitum access to feed and water. The study followed a completely randomized design with five treatments, each consisting of sixteen animals. Treatments included a negative control (no additives), 3 levels of tannin (0.8, 1.6, and 3.2 g of tannin/kg DM; Tanfeed®, Tanac Company), and a positive control (28 mg/kg DM monensin; Elanco®). Animals underwent a 21-day adaptation period with three step-up adaptation diets before entering the 89-day finishing phase. The adaptation dietary program consisted of ad libitum feeding with 3 adaptation diets over 21 days, in which the finishing phase lasted 89 days. The adaptation dietary program consisted of ad libitum feeding of 3 step-up adaptation diets for 3 weeks (21 d). The concentrate level of the diet (DM basis) increased from 40 % to 50 % in week 1, 50–56 % in week 2, and 56–75 % in week 3 (finishing diet). The experimental period (adaptation + finishing phases) lasted 110 d. The diet was formulated to meet the requirements while considering an average daily gain (ADG) of 1.6 kg/d. Enteric CH4 emissions were estimated using the sulfur hexafluoride (SF6) tracer gas technique. Performance and carcass traits, except for shear force and ash in meat, were not affected by increasing levels of dietary tannin or monensin (P>0.10). Regression analysis indicated a quadratic effect on shear force, with the lowest value observed at 1.6 g/kg DM of dietary tannin inclusion (P=0.05). Ash in meat increased quadratically with tannin inclusion, peaking at 1.6 g/kg DM of tannin addition, differing from monensin-treated bulls (P=0.05). However, CH4 emission as g/d decreased quadratically with increasing tannin levels (P<0.01), reaching the lowest emission at 0.8 g/kg DM of tannin inclusion, differing from monensin treatment (P<0.01). Also, CH4 emission intensity (g/kg DMI at CH4 sampling period) tended to decrease quadratically with tannin inclusion (P=0.09), with the lowest intensity observed at 0.8 g/kg DM of tannin inclusion, but not differing from monensin-treated bulls. Liver abscess and rumen scores were not impacted by tannin level in the diet (P = 0.26 and 0.19, respectively); however, the odds of having a liver (0 to A+ scale) and ruminitis score (0-10 scale) of 0 was 0.178 less for monensin-treated bulls compared to control and 0.224 less for monensin than tannin-treated bulls at 3.2 g/kg DM of inclusion, respectively. Overall, condensed tannin effectively reduced meat shear force and CH4 emissionin finishing Nellore bulls in a dose-dependent manner, without detrimental effects on performance.

Systematic review for optimizing sample size in dairy cow methane emission studies in temperate regions: a comprehensive methodological approach.

This research introduces a systematic framework for calculating sample size in studies focusing on enteric methane (CH4, g/kg of DMI) yield reduction in dairy cows. Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a comprehensive search across the Web of Science, Scopus, and PubMed Central databases for studies published from 2012 to 2023. The inclusion criteria were: studies reporting CH4 yield and its variability in dairy cows, employing specific experimental designs (Latin Square Design (LSD), Crossover Design, Randomized Complete Block Design (RCBD), and Repeated Measures Design) and measurement methods (Open-circuit respirometry chambers (RC), the GreenFeed system, and the sulfur hexafluoride tracer technique), conducted in Canada, the United States and Europe. A total of 150 studies, which included 177 reports, met our criteria and were included in the database. Our methodology for using the database for sample size calculations began by defining 6 CH4 yield reduction levels (5, 10, 15, 20, 30, and 50%). Utilizing an adjusted Cohen's f formula and a power analysis we calculated the sample sizes required for these reductions in balanced LSD and RCBD reports from studies involving 3 or 4 treatments. The results indicate that within-subject studies (i.e., LSD) require smaller sample sizes to detect CH4 yield reductions compared with between-subject studies (i.e., RCBD). Although experiments using RC typically require fewer individuals due to their higher accuracy, our results demonstrate that this expected advantage is not evident in reports from RCBD studies with 4 treatments. A key innovation of this research is the development of a web-based tool that simplifies the process of sample size calculation (samplesizecalculator.ucdavis.edu). Developed using Python, this tool leverages the extensive database to provide tailored sample size recommendations for specific experimental scenarios. It ensures that experiments are adequately powered to detect meaningful differences in CH4 emissions, thereby contributing to the scientific rigor of studies in this critical area of environmental and agricultural research. With its user-friendly interface and robust backend calculations, this tool represents a significant advancement in the methodology for planning and executing CH4 emission studies in dairy cows, aligning with global efforts toward sustainable agricultural practices and environmental conservation.

Effect of combining the methanogenesis inhibitor 3-nitrooxypropanol and cottonseeds on methane emissions, feed intake, and milk production of grazing dairy cows

No single enteric CH4 mitigating strategy has been consistently effective or is readily applicable to ruminants in grassland systems. When CH4 mitigating strategies are effective under grazing conditions, mitigation is mild to moderate at best. A study was conducted to evaluate the potential of combining two CH4 mitigation strategies deemed feasible to apply in grazing dairy cows, the methanogenesis inhibitor 3-nitrooxypropanol additive (3-NOP) and cottonseed supplementation (CTS), seeking to enhance their individual CH4 mitigating potential. Forty-eight dairy cows were evaluated in a continuous grazing study and supplemented with either a starch-based concentrate (STA) or one that contained cottonseeds (1.75 kg DM/d; CTS), and with either 19 g/d of 10% 3-NOP (Bovaer®) or the additive’s carrier (placebo), in a 2 × 2 factorial arrangement of treatments. Treatments were supplied mixed with a concentrate supplement (5 kg/d as fed) and offered in two equal rations at milking. Methane emissions were measured on weeks 4 and 8 using the sulphur hexafluoride tracer gas technique over a 5-d period. The 3-NOP and CTS treatments tended to interact on absolute CH4 such that 3-NOP decreased CH4 by 13.4% with STA, but there was no mitigation with 3-NOP and CTS. Treatment interactions were also obtained for CH4 yield, where 3-NOP tended to decrease CH4 when supplied with STA, and tended to increase it with CTS. The increase in CH4 yield with the CTS diet was driven by a numerical decrease in DM intake. Methane intensity was not affected by the 3-NOP or CTS treatments. Total volatile fatty acids in ruminal fluid were not affected by 3-NOP supplementation, but a reduction in acetate and an increase in propionate proportion occurred, resulting in decreased acetate: propionate. The 3-NOP additive decreased grass intake; however, energy−corrected milk yield and milk composition were largely unaffected. Milk urea increased with 3-NOP supplementation. Combining twice daily supplementation of 3-NOP and CTS did not enhance their CH4 mitigation potential when fed to grazing dairy cows. The relatively low inhibition of CH4 production by 3-NOP compared to studies with total mixed rations may result from the mode of delivery (pulse dosed twice daily) and time gap caused by experimental handling and moving of animals to pasture after 3-NOP supplementation in the milking parlour, which could have impaired the synchrony between the additive presence in the rumen and grass intake in paddocks.

The effects of feeding liquid or pelleted formulations of Asparagopsis armata to lactating dairy cows on methane production, dry matter intake, milk production and milk composition

Asparagopsis armata has been reported to have strong antimethanogenic effects when fed to dairy cows. The aim of this study was to evaluate the effect of a liquid and a pelleted formulation of A. armata when fed to lactating dairy cows as a supplemental feed twice daily at milking on i) enteric methane emissions, milk yield and dry matter intake (DMI), and ii) presence of halogenated compounds in milk, urine, faeces, and blood. Forty lactating, multiparous, Holstein-Friesian cows (117 ± 20.2 days in milk) were randomly allocated one of four treatments; 1) CON1: basal diet plus liquid supplement without A. armata, 2) AA1: basal diet plus liquid supplement with A. armata, 3) CON2: basal diet plus pellet supplement without A. armata, and 4) AA2: basal diet plus pellet supplement with A. armata. The liquid and pelleted supplements were offered twice daily for 34 days. Supplements were offered with a grain mix during each milking. The basal diet consisted of vetch hay ad libitum and 6.15 kg dry matter (DM)/d of a grain mix fed as 3.07 kg DM in the dairy per milking. Cows given the AA1 treatment received 298 mg bromoform per day while cows on the AA2 treatment received 293 mg bromoform per day. Individual forage DMI were measured daily via electronic monitoring of individual cows at the feed bins. Methane emissions were measured using the modified sulphur hexafluoride tracer technique on the last 5 days of the experiment. Feeding the A. armata formulations showed no effect on total DMI, forage DMI, concentrate DMI or milk yield. Methane production (g CH4/d), methane yield (g CH4/kg DMI) and methane intensity (g CH4/kg energy corrected milk) were reduced by about 20 % for both the liquid and the pelleted A. armata formulations. Feeding the A. armata formulations led to increased bromoform concentrations in milk (∼2.0 µg/L) but were well below the limit for safe consumption (100 µg/L). It is concluded that both formulations were effective in reducing enteric methane emissions and that milk from cows fed these A. armata formulations is safe for human consumption.

Heritability estimates and genome-wide association study of methane emission traits in Nellore cattle.

The objectives of the present study were to estimate the heritability for daily methane emission (CH4) and residual daily methane emission (CH4res) in Nellore cattle, as well as to perform genome-wide association studies (GWAS) to identify genomic regions and candidate genes influencing the genetic variation of CH4 and CH4res. Methane emission phenotypes of 743 Nellore animals belonging to 3 breeding programs were evaluated. CH4 was measured using the sulfur hexafluoride (SF6) tracer technique (which involves an SF6 permeation tube introduced into the rumen, and an appropriate apparatus on each animal), and CH4res was obtained as the difference between observed CH4 and CH4 adjusted for dry matter intake. A total of 6,252 genotyped individuals were used for genomic analyses. Data were analyzed with a univariate animal model by the single-step GBLUP method using the average information restricted maximum likelihood (AIREML) algorithm. The effects of single nucleotide polymorphisms (SNPs) were obtained using a single-step GWAS approach. Candidate genes were identified based on genomic windows associated with quantitative trait loci (QTLs) related to the 2 traits. Annotation of QTLs and identification of candidate genes were based on the initial and final coordinates of each genomic window considering the bovine genome ARS-UCD1.2 assembly. Heritability estimates were of moderate to high magnitude, being 0.42 ± 0.09 for CH4 and 0.21 ± 0.09 for CH4res, indicating that these traits will respond rapidly to genetic selection. GWAS revealed 11 and 15 SNPs that were significantly associated (P < 10-6) with genetic variation of CH4 and CH4res, respectively. QTLs associated with feed efficiency, residual feed intake, body weight, and height overlapped with significant markers for the traits evaluated. Ten candidate genes were present in the regions of significant SNPs; 3 were associated with CH4 and 7 with CH4res. The identified genes are related to different functions such as modulation of the rumen microbiota, fatty acid production, and lipid metabolism. CH4 and CH4res presented sufficient genetic variation and may respond rapidly to selection. Therefore, these traits can be included in animal breeding programs aimed at reducing enteric methane emissions across generations.

Nitrogen and energy utilization and methane emissions of sheep grazing on annual pasture vs. native pasture.

The purpose of this study was to evaluate the differences in annual pasture and native pasture on dry matter (DM) intake, nutrient digestibility, nitrogen (N) and energy utilization, and methane (CH4) emission of grazing sheep, and to provide the basis for rational livestock grazing in salinized regions. The study used 10 male Hu sheep ♀ × thin-tailed Han sheep ♂ rams (20 ± 5kg) aged 5 mo. Sheep grazing was conducted in annual pasture and native pasture using a 2 × 2 Latin square design. After a 15-d adaptation period for grazing, the digestion and metabolism experiment of sheep were conducted, while CH4 emissions were measured using sulfur hexafluoride tracer gas. DM intake did not differ between annual pasture and native pasture (P = 0.386). Meanwhile, the digestibility of DM (P < 0.001), neutral detergent fiber (P < 0.001), acid detergent fiber (P < 0.01), crude protein (P < 0.001), and ether extract (P < 0.001) of sheep grazing on native pasture was significantly higher than that of annual pasture. Sheep grazing on native pasture had increased N intake (P < 0.001) and N retained (P < 0.001) compared with those grazing on annual pasture. Digestion energy (P < 0.05) and metabolic energy (P < 0.01) of sheep grazing on annual pasture were significantly improved compared with those on native pasture, while fecal energy (P < 0.001), urine energy (P < 0.001) and CH4 energy (CH4-E) output (P < 0.001) and CH4 emission (P < 0.001) of sheep grazing on annual pasture were significantly decreased. The CH4-E/gross energy (GE) values of sheep grazing on annual pasture and native pasture were 0.09 and 0.10, respectively. In conclusion, grazing sheep have higher N utilization on native pasture, whereas grazing sheep have higher energy utilization and low CH4 emissions in annual pasture. In conclusion, annual pasture has a lower CH4-E/GE compared to native pasture, which helps in reducing environmental pollution.

135 Growth Performance, Carcass Characteristics, and Methane Emissions of Feedlot Young Bulls

Abstract The growth performance, carcass characteristics, and methane emissions from feedlot beef cattle fed a high-lipid finishing diet (7.3% of ether extract) were evaluated. Fifty long-yearling young bulls were divided into two groups following their breed composition: Nellore (n = 25) and Angus × Nellore crossbred (n = 25), and randomly assigned into 4 pens (12 or 13 animals/pen) following a completely randomized design. Animals were sourced from the same breeding season and endured a grazing growing phase in Megathyrsus maximus cv. Mombaça pasture, with protein and energy supplement offered at 0.2% of body weight (BW). The feedlot phase comprehended 105 days of feed, and the diet (80% concentrate) was formulated to meet or safely exceed the beef cattle requirements to target an average daily gain (ADG) of 1.6 kg/day, in which major ingredients were represented by (% DM basis): sorghum silage (20%), ground corn (57.6%), ground soybean seed as the lipid source (20.4%), and a mineral/vitamin premix (2%). Titanium dioxide (TiO2) was used as an external marker to estimate dry matter intake (DMI), while 10 g was administered to 12 animals of each group, once daily, for 10 d. Animals were weighed every 30 d after a 16-h fasting period, and the day before slaughter to obtain the final body weight (FBW). Enteric methane emissions were measured using the sulfur hexafluoride (SF6) tracer gas technique in the same animals used for intake measurements. The animals were equipped with gas collection halters attached to pre-evacuated polyvinyl chloride (PVC) sampling canisters with a capillary tube (0.127 mm diameter), made to permit 50% filling in 24 h, for five consecutive days. Data were analyzed using the statistical analysis software R (R CORE TEAM, 2021), and the effect of breed on carcass traits and methane emissions was evaluated using the completely randomized design one-way, in which treatment means were compared by the F test (P &amp;lt; 0.05). The crossbred animals had a greater DMI (12.6 vs.0.6 kg/d), gain efficiency (0.16 vs. 0.14), initial BW upon feedlot phase (509.8 vs. 444.7 kg), FBW (720.8 vs. 595.6, kg), ADG (2.01 vs..44 kg), and hot carcass weight (404.7 vs. 345.0 kg; P &amp;lt; 0.01) compared with Nellore cattle. No difference was observed in dressing percentage between genetic groups (P = 0.28). Nellore animals produced more methane expressed as CH4 g/kg ADG (266.0 vs.73.4; P &amp;lt; 0.01), and tended to produce more methane expressed as CH4 kg/DMI (35.4 vs. 27.7; P = 0.08), and CH4 g/kg CW (1.09 vs. 0.87; P = 0.11). Crossbred F1 Nellore/Angus young bulls showed improved feedlot performance and carcass weight, while not negatively affecting total CH4 production, but rather lessening CH4 emissions per unit of beef produced.

Pigeon Pea Intercropped with Tropical Pasture as a Mitigation Strategy for Enteric Methane Emissions of Nellore Steers.

In this study, we evaluate the effects of intercropping pigeon pea (Cajanus cajan (L.) Millsp.) with tropical pastures for feeding Nellore cattle and compared animal performance and enteric CH4 emissions with other pasture-based systems during the dry and rainy seasons of 2021. Thirty-six Nellore steers (with a body weight of 221 ± 7 kg and an age of 15-16 months) were randomly distributed in three treatments with three replicates (in paddocks of 1.5 hectares each): (1) a degraded pasture of Urochloa spp. (DEG); (2) a recovered and fertilized pasture of Urochloa spp. (REC); and (3) pigeon pea intercropped with Urochloa spp. (MIX). Enteric CH4 emissions were estimated using the sulfur hexafluoride (SF6) tracer gas technique, and dry matter intake (DMI) was determined using internal (iNDF) and external (TiO2) markers. Forages were collected by hand plucking after observations of ingestive behavior, and feces was collected after voluntary defecation. The proportion of grass and legume intake was estimated by C stable isotopes, and the forage nutritional quality was determined, while animal performance was monitored monthly, and the stocking rate was adjusted by the "put and take" technique. The results indicated that intercropping pigeon pea with tropical grasses is an interesting strategy for sustainable livestock production based on pastures. The MIX treatment was able to meet the nutritional requirements of the animals, which presented higher performance. In addition, there was a reduction in CH4 emissions up to 70% when expressed per average daily weight gain in comparison to the DEG treatment.

Twice daily feeding of canola oil steeped with Asparagopsis armata reduced methane emissions of lactating dairy cows

Red seaweeds have emerged as a potent methane-mitigating feed additive in ruminant diets. However, to date they have only been applied to production systems where total mixed rations (TMR) are given. New formulations are being developed to increase the application of red seaweeds, mainly Asparagopsis spp., across different production systems including those without TMR such as grazing-based systems. One product of interest is Asparagopsis armata steeped in edible oil (ASP-Oil) to extract and stabilise the primary antimethanogenic compound, bromoform. The aim of this study was to determine the effect of feeding two formulations of ASP-Oil, with (ASP-Oil 1) and without (ASP-Oil 2) the seaweed biomass removed, on enteric methane emissions, dry matter intake (DMI), milk yield and milk composition of dairy cows over 32 d. Thirty-nine lactating, multiparous, Holstein-Friesian (75 ± 20.6 days in milk) were randomly allocated to one of the three treatments; control (CON; basal diet + 134 g canola oil), ASP-Oil with the seaweed biomass removed (ASP1; basal diet + 134 g ASP-Oil 1), and ASP-Oil without the seaweed biomass removed (ASP2; basal diet + 145 g ASP-Oil 2 + 12 g canola oil). The treatments were given twice daily, using a pulse feeding technique, as a concentrate/oil supplement during each milking. The basal diet consisted of vetch hay ad libitum and 7.0 kg DM/d of a grain mix. Individual forage intakes were measured daily via electronic monitoring of individual cows at the feed bins. Methane emissions were measured using the modified sulphur hexafluoride tracer technique on days 27–32. At the rate of 136 g/d, there was no significant effect of treatment on DMI or milk yield, however during the transition period a rate of 268 g/d decreased hay intake. The supplementation of ASP1 and ASP2 decreased energy corrected milk (ECM; P = 0.029) compared to those cows offered the CON diet. Methane production (g/d) of cows given the ASP1 diet was 44 % lower than cows on the CON diet, methane yield (g/kg DMI) was 44 % lower, and methane intensity (g/kg ECM) was 38 % lower. For the ASP2 cows, the reductions were 39 % for methane production, 33 % for methane yield, and 31 % for methane intensity. Feeding the ASP-Oil increased bromoform concentrations in milk. However, the concentrations detected were demonstrated to be considerably lower than published safe concentrations in milk for human consumption (100 μg/L). These results show that the ASP-Oil has potential to be used as a methane mitigating feed additive when fed in a pulse feeding system.

Tannin-based product in feedlot diet as a strategy to reduce enteric methane emissions of Nellore cattle finished under tropical conditions.

A total of 120 Nellore bulls, [initial body weight (BW) = 307 ± 11.6 kg and 12 mo of age] were allocated into 12 collective pens (10 bulls per pen) in a commercial feedlot to evaluate the effects of a specific blend of tannin and saponins on enteric methane (CH4) emissions. The study was a completely randomized design, in which pens were considered the experimental units (N = 6 pens per treatment) and were randomly allocated into one of two treatments: 1) Control (CON), a basal diet with monensin supplementation (25 mg/kg dry matter [DM]; Rumensin, Elanco Animal Health, Greenfield, IN, USA), or 2) Control + a specific blend of tannin and saponins (TAN; 7 g/kg DM; composed of quebracho and chestnut tannin extracts along with carriers from cereals rich in saponins; SilvaFeed BX, Silvateam, San Michele Mondovi, CN, Italy). After the adaptation period (20 d), the experiment was divided into two phases: growing phase (21 to 53 d; total of 33 d) and fattening phase (54 to 139 d; total of 86 d). Enteric methane emissions were estimated using the sulfur hexafluoride (SF6) tracer gas technique. Interactions between treatment and period (growing vs. fattening) were detected for daily CH4 emissions, in which animals fed TAN reduced CH4 emissions by 17.3% during the fattening period compared to bulls fed CON (P = 0.05). In addition, bulls fed TAN had lower CH4 emissions expressed by dry matter intake (DMI) during the fattening period compared to bulls fed CON (P = 0.06). The findings presented herein indicate that a specific blend of tannin and saponins can be used as a strategy to reduce enteric CH4 emissions and its intensity of Nellore bulls finished in feedlot systems under tropical conditions.

Feeding incremental amounts of ground flaxseed: effects on diversity and relative abundance of ruminal microbiota and enteric methane emissions in lactating dairy cows.

We evaluated the effects of incremental amounts of ground flaxseed (GFX) on diversity and relative abundance of ruminal microbiota taxa, enteric methane (CH4) emissions, and urinary excretion of purine derivatives (PD) in lactating dairy cows in a replicated 4 × 4 Latin square design. Twenty mid-lactation Jersey cows were used in the study. Of these 20 cows, 12 were used for ruminal sampling, 16 for enteric CH4 measurements, and all for spot urine collection. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. Diets were formulated by replacing corn meal and soybean meal with 0%, 5%, 10%, and 15% of GFX in the diet's dry matter. Ruminal fluid samples obtained via stomach tubing were used for DNA extraction. Enteric CH4 production was measured using the sulfur hexafluoride tracer technique. Diets had no effect on ruminal microbiota diversity. Similarly, the relative abundance of ruminal archaea genera was not affected by diets. In contrast, GFX decreased or increased linearly the relative abundance of Firmicutes (P < 0.01) and Bacteroidetes (P < 0.01), respectively. The relative abundance of the ruminal bacteria Ruminococcus (P < 0.01) and Clostridium (P < 0.01) decreased linearly, and that of Prevotella (P < 0.01) and Pseudobutyrivibrio (P < 0.01) increased linearly with feeding GFX. A tendency for a linear reduction (P = 0.055) in enteric CH4 production (from 304 to 256 g/d) was observed in cows fed increasing amounts of GFX. However, neither CH4 yield nor CH4 intensity was affected by treatments. Diets had no effect on the urinary excretion of uric acid, allantoin, and total PD. Overall, feeding GFX decreased linearly the relative abundance of the ruminal bacterial genera Ruminococcus and Clostridium and enteric CH4 production, but no change was seen for CH4 yield and CH4 intensity, or urinary excretion of total PD, suggesting no detrimental effect of GFX on microbial protein synthesis in the rumen.

Enteric Methane Emission from Sheep Fed with Rhodes Grass Hay (Chloris gayana) Alone or Supplemented with Dried Distillers’ Grains with Solubles

Livestock systems based on subtropical and tropical pastures are characterized by the low productivity of livestock due to the poor nutritional value of the forage (low nitrogen concentration and digestibility, and high fiber and lignin concentrations). These conditions lead to low productivity and, consequently, high absolute emissions of methane (CH4) per unit of product. Dry distilled grains with solubles (DDGS) are the main by-product resulting from ethanol production, and they are characterized by their high-energy fibrous and protein content, thus becoming an option for the supplementation of low-quality forage. This research investigated the effects of dietary DDGS inclusion on dry matter digestibility (DMD) and enteric CH4 emission. Eight adult sheep of 64 ± 8 kg live weight were used. The duration of the study was 54 days, divided into two periods (changeover design), which comprised a 17-day pre-experimental period and 10 days for experimental data collection. Animals were allocated to one of two treatments used: hay (H) as a control treatment, where animals were fed with Rhodes grass hay alone; and H + DDGS, where animals were fed with H supplemented with DDGS. CH4 emissions were estimated using the sulfur hexafluoride (SF6) tracer technique. Diets containing DDGS increased DMI by 22% (p &lt; 0.05) and reduced daily CH4 emissions by 24% (g/d), the CH4 yield by 35% (g/kg DMI), and the average value of CH4 energy per gross energy intake (Ym) by 44%, compared to the control treatment (p &lt; 0.05). The experiment demonstrated that supplementation with DDGS in low-quality roughage reduced daily CH4 emissions, yields, and Ym.

Impact of Supplementing Essential Oils on Reduction of Enteric Methane Emission in Indigenous Dairy Cattle

Background: Globally enteric methane emission is the largest contributor of anthropogenic global warming and methane is the second largest driver of global radiative forcing after carbon dioxide. The present study was conducted to evaluate the effect of supplementing essential oils (EOs) in combination of garlic oil and peppermint oil on enteric methane emission in indigenous dairy cattle. Methods: Eight indigenous dairy cattle were divided into two groups supplemented with essential oils in combination of garlic oil and peppermint oil (2.4 mL/animal) as treatment group and without supplementation with paddy straw and concentrate feed (60:40) based diet. A digestibility trial was conducted during the last six days of 30 days feeding trial to evaluate the effect of essential oils in combination on nutrients digestibility. The total methane emission was estimated by sulfur hexa fluoride tracer gas technique (SF6). Result: No significant difference in DMI, TDN and DCP intake could be noted with supplementation of essential oils in indigenous dairy cattle. However, cows fed with combination of garlic oil (GO) and peppermint oil (PO) significantly (P less than 0.05) reduced the methane emission by 10.60% in comparison to control group. Hence, the feasibility of feeding essential oils can be considered at farm level as a methane mitigation strategy.

Phenotypic association among performance, feed efficiency and methane emission traits in Nellore cattle.

Enteric methane (CH4) emissions are a natural process in ruminants and can result in up to 12% of energy losses. Hence, decreasing enteric CH4 production constitutes an important step towards improving the feed efficiency of Brazilian cattle herds. The aim of this study was to evaluate the relationship between performance, residual feed intake (RFI), and enteric CH4 emission in growing Nellore cattle (Bos indicus). Performance, RFI and CH4 emission data were obtained from 489 animals participating in selection programs (mid-test age and body weight: 414±159 days and 356±135 kg, respectively) that were evaluated in 12 performance tests carried out in individual pens (n = 95) or collective paddocks (n = 394) equipped with electronic feed bunks. The sulfur hexafluoride tracer gas technique was used to measure daily CH4 emissions. The following variables were estimated: CH4 emission rate (g/day), residual methane emission and emission expressed per mid-test body weight, metabolic body weight, dry matter intake (CH4/DMI), average daily gain, and ingested gross energy (CH4/GE). Animals classified as negative RFI (RFI<0), i.e., more efficient animals, consumed less dry matter (P <0.0001) and emitted less g CH4/day (P = 0.0022) than positive RFI animals (RFI>0). Nonetheless, more efficient animals emitted more CH4/DMI and CH4/GE (P < 0.0001), suggesting that the difference in daily intake between animals is a determinant factor for the difference in daily enteric CH4 emissions. In addition, animals classified as negative RFI emitted less CH4 per kg mid-test weight and metabolic weight (P = 0.0096 and P = 0.0033, respectively), i.e., most efficient animals could emit less CH4 per kg of carcass. In conclusion, more efficient animals produced less methane when expressed as g/day and per kg mid-test weight than less efficient animals, suggesting lower emissions per kg of carcass produced. However, it is not possible to state that feed efficiency has a direct effect on enteric CH4 emissions since emissions per kg of consumed dry matter and the percentage of gross energy lost as CH4 are higher for more efficient animals.

347 Enteric Methane: Current Measurement and Assessment Techniques

Abstract Enteric methane (ECH4) emissions from ruminants can be measured directly or indirectly using various techniques and recent reviews have discussed advantages and disadvantages of these techniques. The GLOBAL NETWORK project (GN; an international consortium of animal scientists) examined techniques for measuring ECH4, including respiration chambers, the sulfur hexafluoride tracer (SF6) technique, and techniques based on short-term measurements of gas concentrations in samples of exhaled air. The latter category includes automated head chambers (i.e., the GreenFeed system; GF), use of carbon dioxide as a marker, and (handheld) laser methane detection. The conclusion from this analysis was that “there is no ‘one size fits all’ method for measuring ECH4 emission by individual animals” and appropriate and frequent calibrations and recovery tests are necessary with all methods. The team also concluded that the need for screening large numbers of animals (for example, for genomic studies), does not justify the use of measurement methods that are inaccurate. Timing of sampling/data collection is critical for the spot-sampling techniques, such as GF. It is a well-established fact that ECH4 emission is closely related to animal’s dry matter intake (DMI) and feeding patterns. Therefore, data collection using GF has to be sufficiently long and frequent, during both day and night hours, to fully represent the diurnal patter of ECH4 emission. The in vitro gas production and analysis technique can be used to screen feed additives or other ECH4 mitigation treatments, but data must be always confirmed/supported by animal (preferably long-term) studies. ECH4 emission can be also predicted based on dietary or animal variables. Large databases developed by the GN project have confirmed that DMI is driving ECH4, but other factors, such as dietary neutral detergent fiber, milk yield and composition (dairy cows), or dietary forage inclusion and animal’s body weight (beef cattle) can improve prediction accuracy.

Dynamics of the ruminal microbial ecosystem, and inhibition of methanogenesis and propiogenesis in response to nitrate feeding to Holstein calves.

It is known that nitrate inhibits ruminal methanogenesis, mainly through competition with hydrogenotrophic methanogens for available hydrogen (H2) and also through toxic effects on the methanogens. However, there is limited knowledge about its effects on the others members of ruminal microbiota and their metabolites. In this study, we investigated the effects of dietary nitrate inclusion on enteric methane (CH4) emission, temporal changes in ruminal microbiota, and fermentation in Holstein calves. Eighteen animals were maintained in individual pens for 45 d. Animals were randomly allocated to either a control (CTR) or nitrate (NIT, containing 15 g of calcium nitrate/kg dry matter) diets. Methane emissions were estimated using the sulfur hexafluoride (SF6) tracer method. Ruminal microbiota changes and ruminal fermentation were evaluated at 0, 4, and 8 h post-feeding. In this study, feed dry matter intake (DMI) did not differ between dietary treatments (P > 0.05). Diets containing NIT reduced CH4 emissions by 27% (g/d) and yield by 21% (g/kg DMI) compared to the CTR (P < 0.05). The pH values and total volatile fatty acids (VFA) concentration did not differ between dietary treatments (P > 0.05) but differed with time, and post-feeding (P < 0.05). Increases in the concentrations of ruminal ammonia nitrogen (NH3–N) and acetate were observed, whereas propionate decreased at 4 h post-feeding with the NIT diet (P < 0.05). Feeding the NIT diet reduced the populations of total bacteria, total methanogens, Ruminococcus albus and Ruminococcus flavefaciens, and the abundance of Succiniclasticum, Coprococcus, Treponema, Shuttlewortia, Succinivibrio, Sharpea, Pseudobutyrivibrio, and Selenomona (P < 0.05); whereas, the population of total fungi, protozoa, Fibrobacter succinogenes, Atopobium and Erysipelotrichaceae L7A_E11 increased (P < 0.05). In conclusion, feeding nitrate reduces enteric CH4 emissions and the methanogens population, whereas it decreases the propionate concentration and the abundance of bacteria involved in the succinate and acrylate pathways. Despite the altered fermentation profile and ruminal microbiota, DMI was not influenced by dietary nitrate. These findings suggest that nitrate has a predominantly direct effect on the reduction of methanogenesis and propionate synthesis.

Effect of supplementing Leucaena leucocephalaleaves alone or in conjunction with malic acid on nutrient utilization, performance traits, and enteric methane emission in crossbred calves under tropical conditions.

Dietary strategies aiming at minimizing enteric methane (CH4) emission in ruminants are of practical interest from nutritional, economical, and environmental point of view. The present study evaluated the effects of supplementing Leucaena leucocephala leaves either alone or in conjunction with malic acid on nutrient utilization, growth performance, and enteric CH4 emission in crossbred cattle fed wheat straw and concentrate-based diet under tropical conditions. Eighteen crossbred (Karan-Fries) calves were randomly allocated into 3 groups: G-I (control)-fed wheat (Triticum aestivum) straw and concentrate mixture in the ratio 50:50; G-II-fed wheat straw, concentrate mixture, and Leucaena leucocephalaleaves in the ratio45:45:10; and (3) G-III-fed similar diet like G-II with an additional supplementation of 1% malic acid on dry matter intake basis. Experimental feeding spanning 90days included a 7-day metabolism trial and CH4 quantification study by sulfur hexafluoride tracer technique. Results revealed no significant effect of dietary treatments on dry matter intake (DMI) and digestibility of nutrients, except neutral detergent fiber (NDF) digestibility which was 5.5% higher (P < 0.05) in G-III as compared to control. Further, nitrogen (N) metabolism, rumen microbial protein synthesis, and growth performance remained similar among the treatments. No significant effect was also observed for enteric CH4 emission (expressed as g/day and g/kg DMI) in calves supplemented with Leucaena leucocephala leaves and malic acid. Therefore, the present findings depict modest improvement in fiber digestibility with no encouraging effect in mitigating enteric CH4 in growing cattle calves by supplementing Leucaena leucocephala leaves alone or with malic acid within the selected levels.

Performance, nutrient use, and methanogenesis of Nellore cattle on a continuous grazing system of Urochloa brizantha and fed supplement types varying on protein and energy sources

Supplementation of grazing cattle may improve forage utilization, methane emission and efficiency of nutrients use. This study aimed to evaluate the effect of different supllementation strategies on performance, metabolic parameters and methane emission in Nellore cattle reared on well-managed marandu palisadegrass (Urochloa brizantha cv Marandu) pastures. Three supplementation strategies consisted of protein and energy sources from traditional ingredients compared to a novel feedstuff: TS) Traditional supplement (protein-energy) composed of ground corn and soybean meal; ES) energy supplement composed of ground corn; and DS) Distiller's coproduct supplement (protein-energy) composed of ground corn and dried distiller grain (DDG). All supplements were offered at 0.3% of body weight (BW). Sixty-nine growing Nellore bulls [251 kg of body weight (BW) ± 13.0 kg] were randomly distributed according to initial BW in nine paddocks (twenty-three animals per treatment, three paddocks per treatment) to evaluate liveweight gain. From these, eighteen bulls (381.83 kg BW ± 16.15 kg) were selected for methane emission measurements (six animals per treatment) using sulfur hexafluoride tracer gas technique. Six rumen cannulated steers (289.5 kg BW ± 19.6 kg) across six paddocks (two per treatment) were used in an incomplete double Latin square design (3 treatments x 4 periods) to evaluate metabolic parameters. Statistical analyses were done using the Mixed Procedure in SAS and adopting significance level at 5%. It was hypothesized that the use of DS or ES, could increase the N use efficiency because of a higher rumen undegradable protein content, and more energy available for microbial synthesis in the rumen, respectively. Overall, there were no differences on animal performance, intake, nutrients digestibility, ruminal parameters, and microbial protein synthesis among treatments indicating that any of the supplemental sources could be utilized. Although, animals in DS had lower urine N excretion. The ES supplement increased methane yield (g/DMI) and the methane conversion factor Ym (% of gross energy intake) when compared to other treatments, but not methane production, which was similar among all treatments.