Methane release from enteric fermentation and manure management of domestic water buffalo in Nepal.

Methane (CH4) emission in livestock arises from enteric fermentation (EnF) and manure management (MM). This study develops the country-specific CH4 emission factors (EFs) in both EnF and MM for domestic water buffalo (Bubalus bubalis) and estimates total CH4 emission in Nepal using Intergovernmental Panel on Climate Change (IPCC) Tier 2 methodology. Seasonal field data were collected on morphological characteristics, feed characteristics, and manure management practices of the buffalo. The buffalo population was divided into five age groups, and at least 35 buffalo individuals were measured from each age group in the Hilly and Plain regions of Nepal in the winter and summer seasons. Buffalo adult male (BAM) had the highest body weight of 530 ± 53 kg in the plain region and 514 ± 65 kg in the Hill region. Similarly, the weight of buffalo calf (BC) was 91 ± 25 kg in the plain region and 77 ± 26 kg in the Hill region. For different age groups of buffalo, EnF EFs ranged from 34 ± 8 to 90 ± 10 kg CH4 head-1 year-1 and MM EFs ranged from 2.5 ± 0.5 to 7.5 ± 0.5 kg CH4 head-1 year-1. The estimated EnF and MM EFs of buffalo were not statistically different by region (p > 0 .05). The total CH4 flux from buffalo was 347.8 Gg year-1 in Nepal, contributing 322.2 Gg year-1 from EnF and 25.6 Gg year-1 from MM. The country-specific EFs are highly recommended for precise computing of the national emissions and carrying out mitigation action.

Enteric methane emission estimates for the Zimbabwean Sanga cattle breeds of Tuli and Mashona.

The effectiveness of methane mitigation in ruminant livestock production systems depends on the accuracy of estimating methane emission factors and providing accurate emission inventories. Following the Paris Climate agreement, it is recommended that countries adopt the Tier-2 approach for estimating enteric methane emissions from ruminants instead of the Tier-1 approach currently used by most countries. This study sought to provide base line enteric methane emission estimates for the Tuli and Mashona Sanga cattle breeds in Zimbabwe using the IPCC Tier-2 model. Using animal characterization data collected from 412 cattle from Grasslands Research Institute and 406 cattle from Makoholi Research Institute, net energy requirements were estimated. From this and the estimate for digestibility, gross energy intake and dry matter intake were estimated. Gross energy intakes and the estimated methane conversion factor were used to estimate enteric methane emissions. Mean emission factors for Tuli were 45.1, 56, 28.5, 28.4 and 20.6 kg CH4/head/year for cows, bulls, heifers, steers and calves, respectively. For Mashona, they were 47.8, 51.9, 29, 29.1 and 20.7 kgCH4/head/year for cows, bulls, heifers, steers and calves, respectively. Generally, estimated Tier-2 emission factors were significantly different from the IPCC Tier-1 default emission factors. This study concluded that enteric methane emission factors estimated using the IPCC Tier-2 model offer insights into the controversial use of the default IPCC Tier-1 emission factors.

Provincial cattle carbon emissions from enteric fermentation and manure management in South Africa.

Livestock is a major producer of agricultural greenhouse gas emissions in South Africa. Cattle methane (CH4) from enteric fermentation is the main source of the emissions. However, due to shortage of information to guide agricultural mitigation plans in the country, the main objective of this study is to investigate causal factors of the emissions from cattle in all nine national provinces. This study calculates provincial CH4 emission factors and factors (i.e. nitrogen excretion rate and average annual nitrogen excretion per animal) required for nitrous oxide (N2O) emissions from cattle manure management. The study further uses these factors and other values obtained from the literature to calculate cattle CH4 emissions from enteric fermentation and manure management. It also provides similar N2O emissions from manure management as well as urine and dung deposited on the pasture, range and paddock. The emissions are calculated for each cattle type: commercial dairy, commercial beef, subsistence and feedlot cattle. Cattle in South Africa produced a total of 35.37 million tonnes (Mt) of carbon dioxide equivalent (CO2e) emissions in 2019, inclusive of emissions from pasture, range and paddock. Methane from enteric fermentation accounts for 64.54% of the total emissions followed by emissions from pasture, range and paddock (27.66%). Manure management contributes 4.34% of N2O to the total emissions while this source also produces 3.45% of CH4 emissions. Commercial beef is responsible for 50.21% of the total emissions, followed by subsistence beef (36.72%), commercial dairy (10.52%) and feedlot cattle (2.52%). The Eastern Cape province is the highest producer of cattle emissions with 8.66 Mt CO2e, a quarter of the emissions. It is followed by KwaZulu-Natal (7.14 Mt CO2e, 20%) and the Free State (5.65 Mt CO2e, 16%). Gauteng province is responsible for the lowest producer of the emissions with 0.71 Mt CO2e (2%) of the total. South Africa's emission factors are higher than values for Africa, indicating importance of developing national factors to avoid uncertainties in emissions. As a result of national landscape and environmental conditions, the eastern provinces of the country are major sources of cattle emissions in the country.

Severe below-maintenance feed intake increases methane yield from enteric fermentation in cattle.

The relationship between feed intake at production levels and enteric CH4 production in ruminants consuming forage-based diets is well described and considered to be strongly linear. Unlike temperate grazing systems, the intake of ruminants in rain-fed tropical systems is typically below maintenance requirements for part of the year (dry seasons). The relationship between CH4 production and feed intake in animals fed well below maintenance is unexplored, but changes in key digestive parameters in animals fed at low levels suggest that this relationship may be altered. We conducted a study using Boran yearling steers (n 12; live weight: 162·3 kg) in a 4 × 4 Latin square design to assess the effect of moderate to severe undernutrition on apparent digestibility, rumen turnover and enteric CH4 production of cattle consuming a tropical forage diet. We concluded that while production of CH4 decreased (1133·3-65·0 g CH4/d; P < 0·0001), over the range of feeding from about 1·0 to 0·4 maintenance energy requirement, both CH4 yield (29·0-31·2 g CH4/kg DM intake; P < 0·001) and CH4 conversion factor (Ym 9·1-10·1 MJ CH4/MJ gross energy intake; P < 0·01) increased as intake fell and postulate that this may be attributable to changes in nutrient partitioning. We suggest there is a case for revising emission factors of ruminants where there are seasonal nutritional deficits and both environmental and financial benefits for improved feeding of animals under nutritional stress.

The potential of Turkey's province-based livestock sector to mitigate GHG emissions through biogas production.

Methane and nitrous oxide are the two leading greenhouse gases (GHG) that are released to the atmosphere due to livestock enteric fermentation and manure management. This study examines Turkey's province-based GHG emissions released by its livestock sector due to these processes. Besides, this study focusses on biogas production through anaerobic digestion, which is one of the most effective GHG mitigation options from manure management. This study aims to show the importance of the livestock sector in regards to GHG emissions in Turkey based on estimations made by the Intergovernmental Panel on Climate Change (IPCC) 2006 Guidelines. As a result of these estimations, for the year 2015, 33.85 million tons of carbon dioxide equivalent (CO2-eq) were produced from enteric fermentation and manure management system. The study also aims to evaluate Turkey's province-based biogas production potential from animal manure through the anaerobic digestion (AD) technology. Two different biogas potential scenarios with varying manure recovery rates were developed. Scenario 1 was developed based on the assumption of that total amount of produced animal manure would be used in AD for biogas production, and scenario 2 was developed based on the realistic manure recovery rates that vary with the type of livestock. Biogas potentials for scenario 1 and scenario 2 were determined as 8.41 billion m3 and 4.18 billion m3 in 2015, respectively. These values can meet Turkey's total electricity demand at a rate of 5.25% for scenario 1, and the rate of 2.3% for scenario 2. In addition, according to Turkey's GHG Inventory, submitted annually to the United Nations Framework Convention on Climate Change (UNFCCC), GHG emissions from manure management can be reduced by 1.13% through biogas production.

Bayesian mechanistic modeling of thermodynamically controlled volatile fatty acid, hydrogen and methane production in the bovine rumen.

Dynamic modeling of mechanisms driving volatile fatty acid and hydrogen production in the rumen microbial ecosystem contributes to the heuristic prediction of CH4 emissions from dairy cattle into the environment. Existing mathematical rumen models, however, lack the representation of these mechanisms. A dynamic mechanistic model was developed that simulates the thermodynamic control of hydrogen partial pressure ( [Formula: see text] ) on volatile fatty acid (VFA) fermentation pathways via the NAD+ to NADH ratio in fermentative microbes, and methanogenesis in the bovine rumen. This model is unique and closely aligns with principles of reaction kinetics and thermodynamics. Model state variables represent ruminal carbohydrate substrates, bacteria and protozoa, methanogens, and gaseous and dissolved fermentation end products. The model was extended with static equations to model the hindgut metabolism. Feed composition and twice daily feeding were used as model inputs. Model parameters were estimated to experimental data using a Bayesian calibration procedure, after which the uncertainty of the parameter distribution on the model output was assessed. The model predicted a marked peak in [Formula: see text] after feeding that rapidly declined in time. This peak in [Formula: see text] caused a decrease in NAD+ to NADH ratio followed by an increased propionate molar proportion at the expense of acetate molar proportion, and an increase in CH4 production that steadily decreased in time, although the magnitude of increase for CH4 emission was less than for [Formula: see text] . A global sensitivity analysis indicated that parameters that determine the fractional passage rate and NADH oxidation rate altogether explained 86% of the variation in predicted daily CH4 emission. Model evaluation indicated over-prediction of in vivo CH4 emissions shortly after feeding, whereas under-prediction was indicated at later times. The present rumen fermentation modeling effort uniquely provides the integration of the [Formula: see text] controlled NAD+ to NADH ratio for dynamically predicting metabolic pathways that yield VFA, H2 and CH4.

Methane emission from global livestock sector during 1890-2014: Magnitude, trends and spatiotemporal patterns.

Human demand for livestock products has increased rapidly during the past few decades largely due to dietary transition and population growth, with significant impact on climate and the environment. The contribution of ruminant livestock to greenhouse gas (GHG) emissions has been investigated extensively at various scales from regional to global, but the long-term trend, regional variation and drivers of methane (CH4 ) emission remain unclear. In this study, we use Intergovernmental Panel on Climate Change (IPCC) Tier II guidelines to quantify the evolution of CH4 emissions from ruminant livestock during 1890-2014. We estimate that total CH4 emissions in 2014 was 97.1 million tonnes (MT) CH4 or 2.72 Gigatonnes (Gt) CO2 -eq (1 MT = 1012 g, 1 Gt = 1015 g) from ruminant livestock, which accounted for 47%-54% of all non-CO2 GHG emissions from the agricultural sector. Our estimate shows that CH4 emissions from the ruminant livestock had increased by 332% (73.6 MT CH4 or 2.06 Gt CO2 -eq) since the 1890s. Our results further indicate that livestock sector in drylands had 36% higher emission intensity (CH4 emissions/km2 ) compared to that in nondrylands in 2014, due to the combined effect of higher rate of increase in livestock population and low feed quality. We also find that the contribution of developing regions (Africa, Asia and Latin America) to the total CH4 emissions had increased from 51.7% in the 1890s to 72.5% in the 2010s. These changes were driven by increases in livestock numbers (LU units) by up to 121% in developing regions, but decreases in livestock numbers and emission intensity (emission/km2 ) by up to 47% and 32%, respectively, in developed regions. Our results indicate that future increases in livestock production would likely contribute to higher CH4 emissions, unless effective strategies to mitigate GHG emissions in livestock system are implemented.

Determining Appropriate Numbers and Times of Daily Measurements Using GreenFeed System to Estimate Ruminal Methane Emission of Meat Goats.

The study was conducted to determine appropriate numbers and times of daily gas measurements to estimate total daily methane (CH4) emission of meat goats using a GreenFeed system (GFS). A replicated 4 (four measurement protocols) × 4 (four periods) Latin square design was employed with 16 Boer wethers in a confinement pen setting. Measurement protocols entailed three (G-3T; 0600-0700, 1400-1500, and 2200-2300 h), four (G-4T; 0700-0800, 1300-1400, 1900-2000, and 0100-0200 h), and six (G-6T; 0800-0900, 1200-1300, 1600-1700, 2000-2100, 0000-0100, and 0400-0500 h) times for daily measurement periods in GFS. The fourth protocol was continuous measurement over 24 h with animals in an open-circuit respiration calorimetry system (CS). Oat hay was given in individual feeders, and a small predetermined quantity of a pelleted concentrate supplement (bait) was dispensed by the GFS or manually offered for the CS. Overall, total dry matter (DM) intake (614, 625, 635, and 577 g/day for CS, G-3T, G-4T, and G-6T, respectively; SEM = 13.9) and digestible DM intake (359, 368, 374, and 320 CS, G-3T, G-4T, and G-6T, respectively; SEM = 15.9) were lower for CS than for G-3T, G-4T, and G-6T (p < 0.05), but these variables were not different among the GFS protocols. There was a significant (p < 0.001) effect of measurement protocol on CH4 emission in g/day (11.1, 25.6, 27.3, and 26.7 for CS, G-3T, G-4T, and G-6T, respectively; SEM = 1.11), g/kg DM intake (19.3, 46.4, 43.9, and 42.4 for CS, G-3T, G-4T, and G-6T, respectively; SEM = 2.03), and g/kg body weight (0.49, 1.11, 1.18, and 1.16 for CS, G-3T, G-4T, and G-6T, respectively; SEM = 0.052), with values being much lower for CS than for G-3T, G-4T and G-6T. Conversely, CH4 emission was similar among the GFS protocols despite differences in the time and number of daily visits (2.03, 2.76, and 3.75 visits for G-3T, G-4T, and G-6T, respectively; SEM = 0.114; p < 0.001). Pearson correlation (r) analysis indicated a moderate to high (p < 0.05) correlation between CS and G-3T (r = 0.62 for CH4 in g/day and r = 0.59 for CH4 in g/kg BW), CS and G-4T (r = 0.67 for CH4 in g/day and r = 0.76 for CH4 in g/kg BW), and CS and G-6T (r = 0.70 for CH4 in g/day and r = 0.75 for CH4 in g/kg BW). However, the correlation coefficient for CH4 in g/kg DM intake was low between CS and G-3T (r = 0.11) and CS and G-6T (r = 0.31) but slightly greater between CS and G-4T (r = 0.47). In conclusion, the results suggest that CH4 emissions using GFS in a confinement setting were greater compared with the CS in goats, but CH4-emission estimation using the GFS correlated with the CH4 emission in the CS system with a stronger relationship for the four times of daily measurements.

For sustainability environment: some determinants of greenhouse gas emissions from the agricultural sector in EU-27 countries.

Climate events significantly affect the lives of not only humanity but also all living things. Just as transformation in the ecosystem affects sectors, all sectors also transform the ecosystem. It is stated that the agricultural sector is at the root of the deterioration in the ecosystem due to the effect of intensive agriculture after the green revolution. It can be stated that, with an understanding far from the concept of sustainability, the foodstuffs and their waste produced in the agricultural sector are considered among the causes of climate change, which is now concentrated on the whole world in the third millennium. In this study, the effect of N2O gas released from produce residues and the release of enteric fermentation on the level of CO2 released from agricultural-food systems was investigated using advanced econometric models. The findings reveal that both factors are effective. However, it can be stated that the effect of N2O gas released from the produce residues is greater. Suggestions such as improving feed rations and maintaining herd management strategies within certain patterns to reduce the level of enteric fermentation may contribute to the process. In produce residue management, turning waste into compost and expanding bioenergy power plants will ensure both waste disposal and resource continuity in generating energy. Otherwise, the decreasing resources in the world may come to an end, and there will be disruptions and problems in the agricultural sector, as in all sectors. Considering the increasing world population, it is inevitable that food supply security may be endangered and the hunger problem may reach an irreversible level.

Environmental impacts of extensive beef production in Colombia by life cycle assessment: a case study.

The increase in the negative effects of global change promotes the search for alternatives to supply the demand for food worldwide aligned with the Sustainable Development Goals (SDGs) to ensure food security. Animal protein, which is a main source of nutrients in the diet of today's society, especially beef, which is one of the most demanded products nowadays, has been criticized not only for its high water consumption and land occupation for production but also for the emission of greenhouse gases (GHG) from enteric methane generated in the fermentation process within the bovine rumen and deforestation for the adaptation of pastures. This study is mainly motivated by the lack of quantifiable scientific information in Colombia on the environmental impacts of beef production. Therefore, it is intended to estimate some of the impacts of beef production in extensive systems using the life cycle assessment (LCA) method under a particular scenario considering all the production phases (from raw material to fattening, where the cattle are ready to be slaughtered). The study was conducted with data supplied by a farm in Antioquia, Colombia, and the functional unit (FU) was defined as 1 kg of live weight (LW). The scope of this study was gate-to-gate. "The 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories" (IPCC  2006; IPCC 2019) was used to calculate methane and nitrous oxide emissions. LCA modeling was developed with Ecoinvent database v3.8 and the Umberto LCA + software. It was found that the most affected category of damage was ecosystem quality, which represents 77% of the total, followed by human health at 17% and resources at 6%. The category impact of agricultural land occupation is the one that represents the most significant contribution to the ecosystem quality endpoint, with a percentage of 87%, due to the soil's compaction and the loss of the soil's properties. Additionally, the obtained carbon footprint for the system was 28.9 kg of CO2-eq/kg LW.

Effect of Tithonia diversifolia (Hemsl.) A. Gray intake on in vivo methane (CH4) emission and milk production in dual-purpose cows in the Colombian Amazonian piedmont.

The inclusion of Tithonia diversifolia in pasture-based diets is a promising alternative to increase bovine productivity, due to its chemical composition and wide adaptation, but there are few in vivo studies to determine its effect on methane yield and animal production in grazing systems. The objective of this study was to determine the effects of the T. diversifolia inclusion in a basal diet of Brachiaria humidicola on methane (CH4) emissions by enteric fermentation, and on milk yield and quality in dual-purpose cows. The polytunnel technique was used for the determination of methane yield and two diets were evaluated (Diet 1: Brachiaria humidicola 100%; Diet 2: T. diversifolia 15% + B. humidicola 85% dry matter basis) in the moderate rainy and rainy seasons using a cross-over experimental design; milk production was measured by daily milk weighing, and milk quality was determined using a LACTOSCAN analyzer. The inclusion of T. diversifolia did not increase the dry matter intake (P = 0.369), but increased the intake of crude protein and minerals, and reduced fiber intake, resulting in the increased yield of milk and its components in the moderate rainy season (P = 0.012). The inclusion of T. diversifolia reduced the absolute CH4 emissions (P = 0.016), Ym and emission intensity (per unit of fat, protein and kilogram fat and protein corrected milk yields) both in the moderate rainy and rainy seasons (P < 0.05). We conclude that the inclusion of T. diversifolia in the forage feed base in the humid tropics such as the Amazon piedmont can be used as a tool to both mitigate enteric CH4 emissions and to increase animal productivity and hence reduce emissions intensity, and thus reduce pressure on the agricultural frontier in critical areas such as the Amazon.

Assessment of livestock greenhouse gases in Colombia between 1995 and 2015.

The livestock sector in Colombia significantly participates in national economic dynamics but makes significant worldwide contributions to greenhouse gas emissions. Hence, climate change mitigation in this sector is essential. This study aims to assess the greenhouse gas in the livestock sector. The results are reported in methane emissions (CH4) and nitrous oxide (N2O) from enteric fermentation, and N2O by manure management based on the information from the Emission Database for Global Atmospheric Research (EDGAR), in all cases expressed as dioxide of carbon (CO2eq). The emissions obtained from the EDGAR database for 2015 were proportional to the values of the National Inventory of Greenhouse Gases published by the Institute of Hydrology, Meteorology, and Environmental Studies (IDEAM) in 2016. Colombia is the 12th on global, 4th in America and 2nd in South America position by livestock GHG emission, and is the dominant source in all economic sector. The results showed higher records for CH4 emissions during the years 2010 and 2015, while the N2O emissions were higher during 2015. The regions with the highest emissions of CH4 and N2O corresponded to the northwestern area of Colombia. The Spearman correlation test showed a positive correlation between the CH4 emissions, and the age groups studied. The post hoc analysis of the Kruskal-Wallis test showed a more significant influence on CH4 emissions.

Improving productivity reduces methane intensity but increases the net emissions of sheepmeat and wool enterprises.

Greenhouse gas emissions from Western Australia's sheep flock account for 26% of the state's agricultural emissions, principally as a result of enteric methane emissions. A decrease in emissions between 2005 and 2019 can be partly explained by a 44% drop in sheep numbers over that period, but less is known about potential changes in the methane intensity of sheepmeat and wool kg CO2 equivalents/kg product. Using the livestock systems modelling software GrassGro™, we assessed the changes in methane intensity of sheepmeat and wool produced in two major sheep-producing regions in Western Australia. We also evaluated a series of future scenarios. Our results demonstrate that the observed emissions reductions are largely a result of a decrease in flock size, although methane intensity has also decreased somewhat by 11.1%. Simulation of future trajectories indicates that methane intensity could be as much as 18.8% lower by 2030, compared to 2005, with further reductions of up to 42% considered possible. The primary driver of the decreased methane intensity to date is increased flock reproductive performance through increased marking rates, higher rates of ewe lamb mating, and lower ewe death rates. However, despite reductions in methane intensity per kg of product, net emissions per ewe have risen 11.6% since 2005 and are forecast to rise by up to 21.8% by 2030, with potential further increases of up to 61% considered possible. This is driven by increased feed intake due to an increased number of lambs produced per ewe, higher ewe standard reference weights, and lower ewe death rates. Therefore, achieving absolute net reductions in the methane emissions through productivity improvements is unlikely to be prospective. Reducing net emissions is instead likely to be contingent on a reduction in flock numbers, breakthroughs in anti-methanogenic research, or via emissions offsetting. Our approach can be applied in other major livestock producing regions to evaluate emissions performance, with potential implications for agricultural and trade policy as markets increasingly seek lower emissions product.

Exploring greenhouse gas mitigation strategies for agriculture in Africa: The case of Nigeria.

We used the Agriculture and Land Use National Greenhouse Gas Inventory Software to estimate the total greenhouse gas (GHG) emissions from the Nigerian agriculture sector in 2010. We went ahead to project future GHG emissions up to 2050. Two alternative GHG mitigation scenarios such as moderate (MS) and aggressive (AS) scenarios were developed and examined. Our results showed that total GHG emissions from Nigerian agriculture in 2010 were around 34.9 million tonnes of carbon dioxide equivalent. GHG emissions from livestock accounted for about 69.2 % of the total emissions, making it the largest source of GHG emissions in the sector. Nigeria's agriculture GHG emissions are expected to increase by 94 % in 2050 relative to 2010 levels. Mitigation strategies in the Nigerian agriculture sector that do not compromise food security are limited. However, with the implementation of different GHG mitigation strategies in the alternative scenarios, emissions are expected to fall by around 13.2 % and 26.7 % by 2050 in the MS and AS, respectively, compared to the baseline scenario. While the mitigation potentials are significant, we argue that robust and dedicated policies are required to accelerate climate-smart agriculture in Nigeria.

Pasture intensification in beef cattle production can affect methane emission intensity.

Increasing greenhouse gas (GHG) emissions from anthropogenic activities have contributed to global warming and consequently to climate change. Among all sources of emissions, the agricultural sector accounts for just under a quarter, mainly because of the intensification of food production systems necessary to supply the growing demand of the population. As ruminal fermentation is the largest source of methane emission in the livestock industry, emission by cattle has become the focus of studies. The aim of this study was to evaluate enteric methane emission and emission intensities of Nellore cattle at different ages submitted to levels of intensification of the grazing system. Twenty-four animals per cycle (age of 21.8 and 13.1 mo in cycles 1 and 2, respectively) were randomly distributed across different grazing systems: irrigated pasture with a high stocking rate (IHS), dryland pasture with a high stocking rate (DHS), recovering dryland pasture with a moderate stocking rate (DMS), and degraded pasture with a low stocking rate (DP). Methane emission was measured using the sulfur hexafluoride technique in each season of the cycle. Intensive systems provided higher yields of good-quality forage as well as superior animal performance when compared with DP. Methane yields were different between seasons and cycles. Methane emissions per average daily weight gain and dry matter digestible intake were different between treatments. Differences in the results were observed when they were analyzed per hectare, with the highest gain yield (P = 0.0134), stocking rate, weight gain, carcass production, and total methane emission (P < 0.0001) being found for the intensive systems. There were no differences in emissions per weight gain or carcass production between production systems, while a difference was observed between cycles (P = 0.0189 and P = 0.0255, respectively), resulting in lower emission intensities for younger animals. We conclude that more intensive systems resulted in a higher kilograms production of carcass per hectare; however, animals at 19 mo of age raised in the IHS and DMS systems had a lower emission intensity in kilogram of CO2-eq. per kilogram of carcass. Moderate intensification (DMS) using animals at about 19 mo of age might be an effective strategy to mitigate GHG emissions from Brazilian tropical pastures. Further studies are needed to understand the relationship between increasing productivity and decreasing environmental impacts, especially methane emission from ruminants.

Methane emission factors and carbon fluxes from enteric fermentation in cattle of Nepal Himalaya.

This study presents a first estimate of the country-specific enteric methane (CH4) emission factors (EFs) and the net CH4 fluxes for the local and improved cattle breeds (LCB and ICB) in Nepal using the IPCC Tier 2 methodology. The country-specific herd structure, morphological and feed characteristics data of cattle were collected from the field survey. In LCB, adult males had the highest mean live body weights (BWs) ranging from 222 ± 42 kg in the Hill to 237 ± 36 kg in the Plain region, while for improved cattle, adult females had the highest BW of 334 ± 45 kg in the Hill to 308 ± 38 kg in the Plain regions. Weight gains of ICB were higher than the LCB. Local calves gained BWs of 97 ± 20 g day-1, while improved calves gained a weight of 202 ± 41 g day-1. The CH4 EFs ranged from 13 ± 3 to 46 ± 9 kg CH4 head-1 yr-1 for different age-groups of the LCB, while for the ICB, the EFs ranged from 14 ± 3 to 75 ± 15 kg CH4 head-1 yr-1. Overall, the EFs were 33 ± 7 and 46 ± 9 kg CH4 head-1 yr-1 for LCB and ICB, respectively. The estimated enteric EFs of cattle in the Hill and Plain regions were not statistically different (p > 0.05), but a significant difference existed between the breeds (LCB and ICB; p < 0.05). The net CH4 flux was 254 ± 51 Gg yr-1 from enteric fermentation in cattle of Nepal using the country-specific EFs, about 15% higher than using the default EFs (221 ± 66 Gg yr-1). We underline that the emission estimation, deploying the country-specific EFs, will be more accurate, contributing to reduce the uncertainties in the national GHG inventories and supporting the mitigation actions.

Bovicins: The Bacteriocins of Streptococci and Their Potential in Methane Mitigation.

Bovicin is a type AII lantibiotic, possessing two ß-methyllanthionine and a disulfide bridge encoded by bovA gene hitherto unknown a couple of decades ago. Bacteriocins can be useful in directly inhibiting methanogens and/or redirecting H2 to other reductive microorganisms, in particular, propionate producers or reductive acetogens. So far, the role of nisin and bovicin to suppress greenhouse gas (GHG) production under in vitro conditions has been documented. GHG emissions from ruminants are a threat to the environment, because of their role in global warming as well as in climate change. Methane (CH4) produced from livestock farming practices is a potent GHG, comprising 18% of total GHG emissions in the world. Therefore, minimizing enteric CH4 production is quite essential from both the economical livestock production as well as environment perspectives. Strategies for the abatement of CH4 have provided two-way opportunities, viz., improved livestock productivity and reduced GHG emissions. In the past, different strategies have been proposed and tested to mitigate CH4, such as the dietary composition of feeds, ionophores, antibiotics, vaccines, analogues, probiotics, and secondary metabolites of plants and fungi. However, quite a few of these strategies have been adopted at farm level due to their varied effect on animal health and/or residues on animal products. The use of bacteriocins might have potential in inhibiting methanogens in the rumen. A bacteriocin produced by Streptococcus bovis (an isolate from rumen) named bovicin HC5 has been exhibited to decrease CH4 production to an extent of 50%. In this review, authors intend to discuss the sources, structure, biochemical properties, and antimicrobial spectra of bovicins, besides the potential applications with special reference to CH4 mitigation.

Compound- and context-dependent effects of antibiotics on greenhouse gas emissions from livestock.

The use of antibiotics in livestock production may trigger ecosystem disservices, including increased emissions of greenhouse gases. To evaluate this, we conducted two separate animal experiments, administering two widely used antibiotic compounds (benzylpenicillin and tetracycline) to dairy cows over a 4- or 5-day period locally and/or systemically. We then recorded enteric methane production, total gas production from dung decomposing under aerobic versus anaerobic conditions, prokaryotic community composition in rumen and dung, and accompanying changes in nutrient intake, rumen fermentation, and digestibility resulting from antibiotic administration. The focal antibiotics had no detectable effect on gas emissions from enteric fermentation or dung in aerobic conditions, while they decreased total gas production from anaerobic dung. Microbiome-level effects of benzylpenicillin proved markedly different from those previously recorded for tetracycline in dung, and did not differ by the mode of administration (local or systemic). Antibiotic effects on gas production differed substantially between dung maintained under aerobic versus anaerobic conditions and between compounds. These findings demonstrate compound- and context-dependent impacts of antibiotics on methane emissions and underlying processes, and highlight the need for a global synthesis of data on agricultural antibiotic use before understanding their climatic impacts.

Enteric methane emissions and their response to agro-ecological and livestock production systems dynamics in Zimbabwe.

Without disregarding its role as one of the key sources of sustainable livelihoods in Zimbabwe and other developing countries, livestock production contributes significantly to greenhouse gas (GHG) emissions through enteric fermentation. For the livestock sector to complement global efforts to mitigate climate change, accurate estimations of GHG emissions are required. Methane emissions from enteric fermentation in Zimbabwe were quantified over 35years under four production systems and five agro-ecological regions. The Intergovernmental Panel on Climate Change emission factor methodology was used to derive CH4 emissions from seven livestock categories at national level. Emission intensities based on human population, domestic export of livestock meat and climate variables were used to assess emission drivers and predict future emission trends. Over the past 35years, enteric fermentation CH4 emissions from all livestock categories ranged between 158.3 and 204.3Ggyear-1. Communal lands, typified by indigenous livestock breeds, had the highest contribution of between 58% and 75% of the total annual emissions followed by livestock from large scale commercial (LSC) farms. The decreasing livestock population on LSC farms and consequent decline in production could explain the lack of a positive response of CH4 emissions to human population growth, and decreasing emissions per capita over time at -0.3kg CH4capita-1year-1. The emissions trend showed that even if Zimbabwe's national livestock population doubles in 2030 relative to the 2014 estimates, the country would still remain with similar magnitude of CH4 emission intensity as that of 1980. No significant correlations (P>0.05) were found between emissions and domestic export of beef and pork. Further research on enhanced characterisation of livestock species, population and production systems, as well as direct measurements and modelling of emissions from indigenous and exotic livestock breeds were recommended.

Methanobacterium formicicum as a target rumen methanogen for the development of new methane mitigation interventions: A review.

Methanobacterium formicicum (Methanobacteriaceae family) is an endosymbiotic methanogenic Archaean found in the digestive tracts of ruminants and elsewhere. It has been significantly implicated in global CH4 emission during enteric fermentation processes. In this review, we discuss current genomic and metabolic aspects of this microorganism for the purpose of the discovery of novel veterinary therapeutics. This microorganism encompasses a typical H2 scavenging system, which facilitates a metabolic symbiosis across the H2 producing cellulolytic bacteria and fumarate reducing bacteria. To date, five genome-scale metabolic models (iAF692, iMG746, iMB745, iVS941 and iMM518) have been developed. These metabolic reconstructions revealed the cellular and metabolic behaviors of methanogenic archaea. The characteristics of its symbiotic behavior and metabolic crosstalk with competitive rumen anaerobes support understanding of the physiological function and metabolic fate of shared metabolites in the rumen ecosystem. Thus, systems biological characterization of this microorganism may provide a new insight to realize its metabolic significance for the development of a healthy microbiota in ruminants. An in-depth knowledge of this microorganism may allow us to ensure a long term sustainability of ruminant-based agriculture.