Development of enteric methane emission factors for Holstein-Friesian and Norwegian first lactation cows

Abstract

The objectives were to accurately quantify enteric methane (CH₄) emissions for first lactation dairy cows and to use these data to develop CH₄ prediction equations. Calorimeter measurements and production data were used to calculate CH₄ emissions for Holstein-Friesian (HF, n?=?32) and Norwegian (n?=?32) first lactation cows during a 305-d lactation period. Methane outputs were similar between HF and Norwegian (123 vs. 126?kg/305 d) when offered high-concentrate diets, but HF produced more CH₄ (P?<?0.05) than Norwegian (105 vs. 98?kg/305 d) when given low-concentrate diets. The HF offered high-concentrate diets had a lower (P?<?.05) CH₄ emission per energy-corrected milk yield (16.3?g/kg) than the other three treatments (19.7–20.4?g/kg). These data were then used to develop CH₄ prediction equations, which provide an alternative approach to estimate enteric CH₄ emissions for HF and Norwegian first lactation dairy cows.     

A prediction equation for enteric methane emission from dairy cows for use in NorFor

Abstract

A data-set with 47 treatment means (N = 211) was compiled from research institutions in Denmark, Norway, and Sweden in order to develop a prediction equation for enteric methane (CH₄) emissions from dairy cows. The aim was to implement the equation in the Nordic feed evaluation system NorFor. The equation should therefore be based on input variables available in NorFor. The best equation to predict CH₄ (MJ/d) was based on dry matter intake (DMI, kg/d), and content of (g/kg DM) fatty acids (FA), crude protein (CP), and neutral detergent fiber (NDF). The equation was CH₄ = 1.36 (±0.10) × DMI – 0.125 (±0.039) × FA – 0.02 (±0.012) × CP + 0.017 (±0.005) × NDF (RMSE = 3.00 MJ CH₄/d; CV = 13.8%; R² = 0.77), where RMSE is the root mean square error and CV is the coefficient of variation. However, CP was on the borderline of being significant and did not quantitatively explain much variation in CH₄ emission. Based on the present research, we concluded, therefore, that the equation CH₄ = 1.23 (±0.08) × DMI – 0.145 (±0.039) × FA + 0.012 (±0.005) × NDF (RMSE = 3.10 MJ CH₄/d; CV = 14.3%; R² = 0.75) is most suited for being implemented in NorFor. However, the ability of the proposed equation to predict enteric methane emissions is uncertain until evaluated on an independent data-set.     

Prediction of enteric methane emission from beef cattle in Southeast Asia

We conducted a meta‐data analysis to develop prediction equations to estimate enteric methane (CH₄) emission from beef cattle in Southeast Asia. The dataset was obtained from 25 studies, which included 332 individual observations on nutrient intakes, digestibilities, and CH₄ emissions. Cattle were provided tropical forage or rice straw, with or without concentrates in individual pens equipped with indirect open‐circuit head hood apparatus. The simplest and best equation to predict daily CH₄ emission was CH₄ (g/day) = 22.71 (±1.008) × dry matter intake (DMI, kg/day) + 8.91 (±10.896) [R² = 0.77; root mean square error (RMSE) = 19.363 g/day]. The best equation to predict CH₄ energy as a proportion of gross energy intake (CH₄‐E/GEI, J/100 J) was obtained using DMI per body weight (DMIBW, kg/100 kg), content (g/100 g DM) of ether extract (EE) and crude protein (CP), and DM digestibility (DMD, g/100 g); CH₄‐E/GEI = ?0.782 (±0.2526) DMIBW ? 0.436 (±0.0548) EE ? 0.073 (±0.0218) CP + 0.049 (±0.0097) DMD + 8.654 (±0.6517) (R² = 0.39; RMSE = 1.3479 J/100 J GEI). It was indicated that CH₄ emissions from beef cattle in Southeast Asia are predictable using present developed models including simple indices.     

Prediction of enteric methane emissions from lactating cows using methane to carbon dioxide ratio in the breath

The aim of this study was to develop prediction equations for methane (CH₄) emissions from lactating cows using the CH₄/carbon dioxide (CO₂) ratio in the breath measured in the automatic milking system (AMS) and to evaluate the predicted values and factors affecting the CH₄/CO₂ ratio. The model development was conducted using a dataset determined in respiration chambers or head boxes (n = 121). Then, gas measurements in the AMS as well as in the head box were carried out with six lactating cows fed one of three different levels of neutral detergent fiber (NDF) content, following a 3 × 3 Latin square experimental design. The obtained equation that is suitable for practical use on farms to predict CH₄ was CH₄ (L/day) = −507 + 0.536 live weight (kg) + 8.76 energy-corrected milk (kg/day) + 5,029 CH₄/CO₂ (adjusted R² = 0.83; root mean square error = 40.8 L/day). Results showed that the predicted values correlated positively with the observed values, the determined CH₄/CO₂ ratio increased with increasing dietary NDF content, and the detected eructation rate was in the normal range. On the other hand, the CH₄/CO₂ ratio was affected by the time interval between measurement and last eating before the measurement.     

Expected consequences of including methane footprint into the breeding goals in beef cattle. A Spanish Blonde d'Aquitaine population as a case of study

This study evaluates two potential scenarios for including methane (CH₄) emissions in the breeding objectives of beef cattle, using the Spanish population of Blonde d′Aquitaine as a case of study. First, CH₄ emissions were included as a cost using a shadow carbon price of 1.22€/CH₄ kg (0.044€/CO₂ kg) (carbon tax scenario). In the other scenario, a CH₄ quota was applied, optimizing emissions per unit of product. The current production system was used as benchmark scenario (Scenario 1). The economic value of CH₄ was calculated under all scenarios using a bioeconomic model that translated the production system into a mathematical function. Then, CH₄ emissions were included with proper relative weight in the selection index under each scenario. The economic value of CH₄ production from cows was ?0.54€/year and ?0.16€/year in a carbon tax and in a CH₄ quota scenario, respectively. Economic values for CH₄ production from fattening calves were ?1.22€/year and ?0.34€/year in a carbon tax and a quota scenario, respectively. The relative weights of total CH₄ traits in the indices were 4.9% and 1.8% in a carbon tax and quota scenario. The carbon tax scenario led to smaller cows (?7.59 kg of mature weight) and a decrease in carcass weight gain of calves (?4.78 g/day) involving a reduction in emissions in comparison with Scenario 1 (?0.76 CH₄ kg/slaughtered calf/year). However, it also led to a lower expected gain in profit per unit of product (?7.86 €/slaughtered calf/year). A carbon quota scenario would select slightly smaller cows (?0.48 kg) with similar responses in maternal abilities (age at first calving, calving interval, maternal weaning weight, and calving ease) and growth, and lower emissions (?0.22 CH₄ kg/slaughtered calf/year) regarding the benchmark scenario. Profit per cow would increase by +1.52€/slaughtered calf/year although this scenario implies a reduction in the number of cows per herd. In a carbon tax scenario, higher reduction in emissions implied a reduction of profitability per animal.     

Enteric methane emissions from dairy cows fed different proportions of highly digestible grass silage

Abstract

Enteric methane (CH₄) emissions were measured from six lactating dairy cows using the sulfur hexafluoride tracer technique. Three diets with different proportions of highly digestible grass silage/concentrates were fed: 500/500, 700/300, or 900/100 g kg^–1 dry matter (DM). The average daily CH₄ emissions were 282, 300, and 321 g animal^–1, respectively and the methane conversion factor (Y _m ) from gross energy (GE) ranged from 0.051 to 0.056. However, the statistical power of the study was weak and the differences between diets were not significant (p=0.149 and p=0.293, respectively). A linear regression analysis showed a trend (p=0.08) toward higher enteric CH₄ emissions with higher proportion of high quality grass silage in the diet. A definite conclusion is not possible and further studies are needed as a base for concrete advice on how to mitigate enteric CH₄ emissions from high yielding dairy cows in Scandinavia.     

Methane emissions and δ13C composition from beef steers consuming increasing proportions of sericea lespedeza hay on bermudagrass hay diets

An experiment was conducted to evaluate the effects of different proportions of ‘Au Grazer’ sericea lespedeza [SL, Lespedeza cuneata (Dum. Cours.) G. Don], a legume rich in condensed tannins (CT), on nutrient intake and digestibility, and to estimate methane (CH₄) emissions and ¹³C isotopic composition (δ¹³C_CH4) from beef steers consuming a forage-based diet. Twenty-five Angus-crossbred steers were distributed in a randomized complete block design (344 ± 48 kg initial BW), and randomly assigned to one of five treatments: 0SL, 25SL, 50SL, 75SL, and 100SL, diets containing 0%, 25%, 50%, 75%, and 100% of SL hay, respectively, mixed with ‘Tifton-85’ bermudagrass hay (Cynodon spp.). The study was carried out for two experimental periods of 21-d each. The statistical model included the fixed effect of treatment and random effects of block, experimental period, and their interaction. Apparent total tract digestibility of crude protein, neutral detergent fiber, and acid detergent fiber was linearly decreased (P < 0.001) by the inclusion of SL. No effects were observed for total CH₄ emissions per day, nor for CH₄ relative to organic matter intake or digestible organic matter with the inclusion of SL. However, emission of CH₄ in relation to intake of CT was affected by treatment (P < 0.001). A linear (P < 0.001) decrease and a quadratic effect (P < 0.001) were observed for δ¹³C of diets and gas, respectively, in which diets and enteric CH₄ with greater inclusion of SL were more depleted in ¹³C. Moreover, the difference in δ¹³C between diets and gas (Δδ¹³C) had a linear decrease (P = 0.001) with the inclusion of SL. The model developed to predict the C₃ proportions in the enteric CH₄ fitted to predicted values (P < 0.0001). Therefore, greater proportions of SL resulted in lesser CH₄ emission when CT intake was considered and the isotopic composition from enteric CH₄ was able to predict the contribution of SL in the emissions.     

Estimation of enteric methane emission factors for Ndama cattle in the Sudanian zone of Senegal

Methane (CH₄) emission estimations for cattle in Sub-Saharan Africa (SSA) reflect limited production levels and diets that are high in cellulose forage. However, data on these livestock systems is lacking for their accurate evaluation. To provide guidance for climate change mitigation strategies in Senegal, it is necessary to obtain reliable estimates of CH₄ emissions from Ndama cattle reared in grazing systems, which is the predominant cattle system in the country. The objective of this study was to determine the annual methane emission factor (MEF) for enteric fermentation of Ndama cattle following the IPCC Tier 2 procedure. Our estimated annual MEF at the herd scale was 30.8 kg CH₄/TLU (30.7 kg CH₄/head/yr for lactating cows and 15.1 kg CH₄/head/yr for other cattle). These values are well below the default IPCC emission factor (46 and 31 kg CH₄/head/yr for dairy and other cattle, respectively) proposed in the Tier 1 method for Africa. Our study showed that feed digestibility values differ with season (from 46 to 64%). We also showed that cattle lose weight and adapt to lower feed requirements during the long dry season, with a resulting major reduction in methane emissions. The results of this work provide a new framework to re-estimate the contribution of grazing systems to methane emissions in Africa.

     

Meta-analysis quantifying the potential of dietary additives and rumen modifiers for methane mitigation in ruminant production systems

Increasingly countries are seeking to reduce emission of greenhouse gases from the agricultural industries, and livestock production in particular, as part of their climate change management. While many reviews update progress in mitigation research, a quantitative assessment of the efficacy and performance-consequences of nutritional strategies to mitigate enteric methane (CH₄) emissions from ruminants has been lacking. A meta-analysis was conducted based on 108 refereed papers from recent animal studies (2000–2020) to report effects on CH₄ production, CH₄ yield and CH₄ emission intensity from 8 dietary interventions. The interventions (oils, microalgae, nitrate, ionophores, protozoal control, phytochemicals, essential oils and 3-nitrooxypropanol). Of these, macroalgae and 3-nitrooxypropanol showed greatest efficacy in reducing CH₄ yield (g CH₄/kg of dry matter intake) at the doses trialled. The confidence intervals derived for the mitigation efficacies could be applied to estimate the potential to reduce national livestock emissions through the implementation of these dietary interventions.     

Use of 3-nitrooxypropanol in a commercial feedlot to decrease enteric methane emissions from cattle fed a corn-based finishing diet

The present study evaluated enteric CH₄ production, dry matter (DM) intake (DMI), and rumen fermentation in feedlot cattle supplemented with increasing concentrations of 3-nitrooxypropanol (3-NOP). A total of 100 crossbred steers (body weight, 421 ± 11 kg) was randomly assigned to one of four treatments (n = 25/treatment): control (no 3-NOP) or low (100 mg/kg DM), medium (125 mg/kg DM), and high (150 mg/kg DM) doses of 3-NOP. The study was comprised of 28 d of adaptation followed by three 28-d periods, with CH₄ measured for 7 d per period and cattle remaining on their respective diets throughout the 112-d study. Each treatment group was assigned to a pen, with the cattle and diets rotated among pens weekly to allow the animals to access the GreenFeed emission monitoring (GEM) system stationed in one of the pens for CH₄ measurement. Measured concentration (mg/kg DM) of 3-NOP in the total diet consumed (basal diet + GEM pellet) was 85.6 for low, 107.6 for medium, and 124.5 for high doses of 3-NOP. There was a treatment × period interaction (P < 0.001) for DMI; compared with control, the DMI was less for the low and high doses in period 1, with no differences thereafter. Compared with control (10.78 g/kg DMI), CH₄ yield (g/kg DMI) was decreased (P < 0.001) by 52%, 76%, and 63% for low, medium, and high doses of 3-NOP, respectively. A treatment × period effect (P = 0.048) for CH₄ yield indicated that the low dose decreased in efficacy from 59% decrease in periods 1 and 2 to 37% decrease in period 3, while the efficacy of the medium and high doses remained consistent over time. Irrespective of dose, hydrogen emissions increased by 4.9-fold (P < 0.001), and acetate:propionate ratio in rumen fluid decreased (P = 0.045) with 3-NOP supplementation, confirming that other hydrogen-utilizing pathways become more important in the CH₄-inhibited rumen. The study indicates that supplementation of corn-based finishing diets with 3-NOP using a medium dose is an effective CH₄ mitigation strategy for commercial beef feedlots with a 76% decrease in CH₄ yield. Further research is needed to determine the effects of 3-NOP dose on weight gain, feed conversion efficiency, and carcass characteristics of feedlot cattle at a commercial scale.     

Ranking cows’ methane emissions under commercial conditions with sniffers versus respiration chambers

This study assessed the ranking of dairy cows using individual-level correlations for methane (CH₄) emission on-farm using sniffers and in respiration chambers. In total 20 lactating dairy cows, ten Holstein and ten Jerseys were recorded using sniffers installed in milking robots for three weeks of lactation and subsequently in respiration chambers (RC) where they were each recorded on three occasions within the RC. Bivariate linear mixed models were used to determine the individual-level correlations (r_I) between sniffer and RC phenotypes as proxies for genetic correlations. Despite differences in feeding and management, the predicted CH₄ production from sniffers correlated highly with RC CH₄ production r_I?=?0.77?±?0.18 and CH₄ breath concentration correlated nearly as well with RC CH₄ production r_I?=?0.75?±?0.20. These correlations between sniffers on-farm and RC demonstrate the potential of sniffers measurements as large-scale indicator traits for CH₄ emissions in dairy cattle.     

Effect of dietary fiber on methane production in Chinese Lantang gilts

The objective of this study was to determine the effect of dietary fiber on methane (CH₄) production in pigs using the Chinese native Lantang gilts as study model. The study consisted of two experiments. In the first, 12 Lantang gilts (58.7±0.37 kg), individually housed in open-circuit respiration chambers were randomly divided into two groups (six replicates per dietary group) and fed either with low fiber diet [LFD; neutral detergent fiber (NDF)=201.5 g/kg] or high fiber diet (HFD; NDF=329.7 g/kg). Wheat bran was the main source of fiber for the LFD while ground rice hull (mixture of rice bran and rice hull) was used in the HFD. Results of the study showed that gilts fed LFD recorded higher (P<0.05) digestibility coefficients for dry matter (DM), total organic carbon (TOC), acid detergent fiber (ADF) and cellulose than those in the HFD. However, digestibility coefficient for NDF did not differ between treatments but that for hemicellulose was higher for HDF than for LDF. Because of the higher NDF and hemicellulose contents in the diet, pigs in the HFD recorded higher (P<0.05) amount of digested NDF (126.1 vs. 83.6 g/d) and hemicellulose (38.7 vs. 11.9 g/d) than those fed LFD. The higher amount of digested NDF and hemicellulose recorded for the HFD treatment was inconsistent with the lower (P<0.01) daily CH₄ production from gilts fed the HFD compared to that fed LFD (2.46 vs. 3.90 L/pig). To better explain for the unexpected higher CH₄ production from pigs fed LFD, an in vitro fermentation study was conducted using a factorial design comprised of two inocula (collected from low fiber and high fiber diets) and eight substrates (LFD, HFD, wheat bran, ground rice hull and their respective NDF residues). Results of the in vitro trial seems to suggest that the low CH₄ production from the HFD animals was primarily the results of low fermentation rates of HFD and the ground rice hull. However, the calculated CH₄ productions based on the molar percentage of volatile fatty acids (VFA) in both, in vivo and in vitro experiments reaffirmed the in vivo result, that is, CH₄ production from pigs fed HFD was lower than that fed LFD. Although there is a lack of scientific data from this study to fully explain for the unexpected lower CH₄ production from pigs fed the HFD, our results seems to suggest that quantity of digested fiber (including NDF) was not the sole factor affecting enteric CH₄ production in pigs.     

Combined effects of 3-nitrooxypropanol and canola oil supplementation on methane emissions,rumen fermentation and biohydrogenation,and total tract digestibility in beef cattle

The individual and combined effects of 3-nitrooxypropanol (3-NOP) and canola oil (OIL) supplementation on enteric methane (CH₄) and hydrogen (H₂) emissions, rumen fermentation and biohydrogenation, and total tract nutrient digestibility were investigated in beef cattle. Eight beef heifers (mean body weight ± SD, 732 ± 43 kg) with ruminal fistulas were used in a replicated 4 × 4 Latin square with a 2 (with and without 3-NOP) × 2 (with and without OIL) arrangement of treatments and 28-d periods (13 d adaption and 15 d measurements). The four treatments were: control (no 3-NOP, no OIL), 3-NOP (200 mg/kg dry matter [DM]), OIL (50 g/kg DM), and 3-NOP (200 mg/kg DM) plus OIL (50 g/kg DM). Animals were fed restrictively (7.6 kg DM/d) a basal diet of 900 g/kg DM barley silage and 100 g/kg DM supplement. 3-NOP and OIL decreased (P < 0.01) CH₄ yield (g/kg DM intake) by 31.6% and 27.4%, respectively, with no 3-NOP × OIL interaction (P = 0.85). Feeding 3-NOP plus OIL decreased CH₄ yield by 51% compared with control. There was a 3-NOP × OIL interaction (P = 0.02) for H₂ yield (g/kg DM intake); the increase in H₂ yield (P < 0.01) due to 3-NOP was less when it was combined with OIL. There were 3-NOP × OIL interactions for molar percentages of acetate and propionate (P < 0.01); individually, 3-NOP and OIL decreased acetate and increased propionate percentages with no further effect when supplemented together. 3-NOP slightly increased crude protein (P = 0.02) and starch (P = 0.01) digestibilities, while OIL decreased the digestibilities of DM (P < 0.01) and neutral detergent fiber (P < 0.01) with no interactions (P = 0.15 and 0.10, respectively). 3-NOP and OIL increased (P = 0.04 and P < 0.01, respectively) saturated fatty acid concentration in rumen fluid, with no interaction effect. Interactions for ruminal trans-monounsaturated fatty acids (t-MUFA) concentration and percentage were observed (P = 0.02 and P < 0.01); 3-NOP had no effect on t-MUFA concentration and percentage, while OIL increased the concentration (P < 0.01) and percentage (P < 0.01) of t-MUFA but to a lesser extent when combined with 3-NOP. In conclusion, the CH₄-mitigating effects of 3-NOP and OIL were independent and incremental. Supplementing ruminant diets with a combination of 3-NOP and OIL may help mitigate CH₄ emissions, but the decrease in total tract digestibility due to OIL may decrease animal performance and needs further investigation.     

Dietary mitigation of enteric methane emissions from ruminants: A review of plant tannin mitigation options

Methane gas from livestock production activities is a significant source of greenhouse gas (GHG) emissions which have been shown to influence climate change. New technologies offer a potential to manipulate the rumen biome through genetic selection reducing CH₄ production. Methane production may also be mitigated to varying degrees by various dietary intervention strategies. Strategies to reduce GHG emissions need to be developed which increase ruminant production efficiency whereas reducing production of CH₄ from cattle, sheep, and goats. Methane emissions may be efficiently mitigated by manipulation of natural ruminal microbiota with various dietary interventions and animal production efficiency improved. Although some CH₄ abatement strategies have shown efficacy in vivo, more research is required to make any of these approaches pertinent to modern animal production systems. The objective of this review is to explain how anti-methanogenic compounds (e.g., plant tannins) affect ruminal microbiota, reduce CH₄ emission, and the effects on host responses. Thus, this review provides information relevant to understanding the impact of tannins on methanogenesis, which may provide a cost-effective means to reduce enteric CH₄ production and the influence of ruminant animals on global GHG emissions.     

Effects of protein supplementation to steers consuming low-quality forages on greenhouse gas emissions

Providing supplements that enhance the efficiency of feed utilization can reduce methane (CH₄) emissions from ruminants. Protein supplementation is widely used to increase intake and digestion of low-quality forages, yet little is known about its impact on CH₄ emissions. British-cross steers (n = 23; initial body weight [BW] = 344 ± 33.9 kg) were used in a three-period crossover design to evaluate the effect of protein supplementation to beef cattle consuming low-quality forage on ruminal CH₄, metabolic carbon dioxide (CO₂) emissions, forage intake, and ruminal fermentation. Steers individually had ad libitum access to low-quality bluestem hay (4.6% crude protein [CP]) and were provided supplemental protein based on (dry matter basis): cottonseed meal (CSM; 0.29% of BW daily; 391 g/d CP), dried distillers grains with solubles (DDGS; 0.41% of BW daily 563 g/d CP), or none (CON). Urea was added to DDGS to match rumen degradable protein provided by CSM. Ruminal CH₄ and metabolic CO₂ fluxes were obtained 2.4 ± 0.4 times per steer daily using an automated open-circuit gas quantification system (GreenFeed emission monitoring system; C-Lock Inc., Rapid City, SD). Forage intake increased (P < 0.01) with protein supplementation; however, no difference in forage intake (P = 0.14) was observed between CSM and DDGS treatments. Flux of CO₂ (g/d) was greater (P < 0.01) for steers fed CSM and DDGS than for steers fed CON. Steers supplemented with CSM had greater (P < 0.01) CH₄ emissions (211 g/d) than DDGS (197 g/d) both of which were greater (P < 0.01) than CON (175 g/d). Methane emissions as a proportion of gross energy intake (GEI) were lowest (P < 0.01) for DDGS (7.66%), intermediate for CSM (8.46%) steers, and greatest for CON (10.53%). Steers fed DDGS also had the lowest (P < 0.01) ruminal acetate:propionate ratio (3.60), whereas CSM (4.89) was intermediate, and CON (5.64) steers were greatest. This study suggests that the common practice of supplementing protein to cattle consuming low-quality forage decreases greenhouse gas emissions per unit of GEI.     

Tropical tanniniferous legumes used as an option to mitigate sheep enteric methane emission

This study presents the first results from Brazil using SF₆ tracer technique adapted from cattle to evaluate the capability of condensed tannin (CT) present in three tropical legume forages, Leucaena leucocephala (LEU), Styzolobium aterrimum (STA), and Mimosa caesalpiniaefolia Benth (MIM) to reduce enteric CH₄ production in Santa Inês sheep. Twelve male lambs [27.88?±?2.85 kg body weight (BW)] were allocated in individual metabolic cages for 20-day adaptation followed by 6 days for measuring dry matter intake (DMI) and CH₄ emission. All lambs received water, mineral supplement, and Cynodon dactylon v. coast-cross hay ad libitum. The treatments consisted of soybean meal (710 g/kg) and ground corn (290 g/kg) [control (CON)]; soybean meal (150 g/kg), ground corn (30 g/kg), and Leucaena hay (820 g/kg) (LEU); soybean meal (160 g/kg), ground corn (150 g/kg), and Mucuna hay (690 g/kg) (STA); and soybean meal (280 g/kg), ground corn (190 g/kg), and Mimosa hay (530 g/kg) (MIM); all calculated to provide 40 g/kg CT (except for CON). DMI (in grams of DMI per kilogram BW per day) was lower for LEU (22.0) than CON (29.3), STA (31.2), and MIM (31.6). The LEU group showed emission of 7.8 g CH₄/day, significantly lower than CON (10.5 g CH₄/day), STA (10.4 g CH₄/day), and MIM (11.3 g CH₄/day). However, when the CH₄ emission per DMI was considered, there were no significant differences among treatments (0.37, 0.36, 0.33, and 0.35 g CH₄/g DMI/kg BW/day, respectively, for CON, LEU, STA, and MIM). The sheep receiving STA had shown a tendency (p?=?0.15) to reduce methane emission when compared to the CON group. Therefore, it is suggested that tropical tanniniferous legumes may have potential to reduce CH₄ emission in sheep, but more research is warranted to confirm these results.     

Effects of defaunation and dietary coconut oil distillate on fermentation,digesta kinetics and methane production of Brahman heifers

A 2 × 2 factorial experiment was conducted to assess the effects of presence or absence of rumen protozoa and of dietary coconut oil distillate (COD) supplementation on rumen fermentation characteristics, digesta kinetics and methane production in Brahman heifers. Twelve Brahman heifers were selected to defaunate, with 6 being subsequently refaunated. After defaunation and refaunation, heifers were randomly allocated to COD supplement or no supplement treatments while fed an oaten chaff‐based diet. Methane production (MP; 94.17 v 104.72 g CH₄/d) and methane yield [MY; 19.45 v 21.64 g CH₄/kg dry matter intake (DMI)] were reduced in defaunated heifers compared with refaunated heifers when measured at 5 weeks after refaunation treatment (p < 0.01). Supplement of COD similarly reduced MP and MY (89.36 v 109.53 g/d and 18.46 v 22.63 g/kg DMI, respectively; p < 0.01), and there were no significant interactions of defaunation and COD effects on rumen fermentation or methane emissions. Concentration of total volatile fatty acid (VFA) and molar proportions of acetate, propionate and butyrate was not affected by defaunation or by COD. Microbial crude protein (MCP; g/d) outflow was increased by defaunation (p < 0.01) in the absence of COD but was unaffected by defaunation in COD‐supplemented heifers. There was a tendency towards a greater average daily gain (ADG) in defaunated heifers (p = 0.09), but COD did not increase ADG (p > 0.05). The results confirmed that defaunation and COD independently reduced enteric MP even though the reduced emissions were achieved without altering rumen fermentation VFA levels or gut digesta kinetics.     

The role of seaweed as a potential dietary supplementation for enteric methane mitigation in ruminants: Challenges and opportunities

Seaweeds are macroalgae, which can be of many different morphologies, sizes, colors, and chemical profiles. They include brown, red, and green seaweeds. Brown seaweeds have been more investigated and exploited in comparison to other seaweed types for their use in animal feeding studies due to their large sizes and ease of harvesting. Recent in vitro and in vivo studies suggest that plant secondary compound-containing seaweeds (e.g., halogenated compounds, phlorotannins, etc.) have the potential to mitigate enteric methane (CH₄) emissions from ruminants when added to the diets of beef and dairy cattle. Red seaweeds including Asparagopsis spp. are rich in crude protein and halogenated compounds compared to brown and green seaweeds. When halogenated-containing red seaweeds are used as the active ingredient in ruminant diets, bromoform concentration can be used as an indicator of anti-methanogenic properties. Phlorotannin-containing brown seaweed has also the potential to decrease CH₄ production. However, numerous studies examined the possible anti-methanogenic effects of marine seaweeds with inconsistent results. This work reviews existing data associated with seaweeds and in vitro and in vivo rumen fermentation, animal performance, and enteric CH₄ emissions in ruminants. Increased understanding of the seaweed supplementation related to rumen fermentation and its effect on animal performance and CH₄ emissions in ruminants may lead to novel strategies aimed at reducing greenhouse gas emissions while improving animal productivity.     

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.     

Effects of quebracho tannin extract on intake,digestibility, rumen fermentation,and methane production in crossbred heifers fed low-quality tropical grass

The aim of this work was to evaluate the effect of quebracho tannins extract (QTE) on feed intake, dry matter (DM) digestibility, and methane (CH₄) emissions in cattle fed low-quality Pennisetum purpureum grass. Five heifers (Bos taurus × Bos indicus) with an average live weight (LW) of 295 ± 19 kg were allotted to five treatments (0, 1, 2, 3, and 4% QTE/kg DM) in a 5 × 5 Latin square design. Intake, digestibility, and total methane emissions (L/day) were recorded for periods of 23 h when cattle were housed in open-circuit respiration chambers. Dry matter intake (DMI), organic matter intake (OMI), dry matter digestibility (DMD), and organic matter digestibility (OMD) were different between treatments with 0 and 4% of QTE/kg DM (P < 0.05). Total volatile fatty acid and the molar proportion of acetate in the rumen was not affected (P < 0.05); however, the molar proportion of propionate increased linearly (P < 0.01) for treatments with 3 and 4% QTE. Total CH₄ production decreased linearly (P < 0.01) as QTE increased in the diet, particularly with 3 and 4% concentration. When expressed as DMI and OMI by CH₄, production (L/kg) was different between treatments with 0 vs 3 and 4% QTE (P < 0.05). It is concluded that the addition of QTE at 2 or 3% of dry matter ration can decrease methane production up to 29 and 41%, respectively, without significantly compromising feed intake and nutrients digestibility.