Livestock and climate change mitigation strategies

Table of contents

List of tables

Abbreviation

Acknowledgement:

Abstract

1) INTRODUCTION
Objective

2) Literature Review
2.1. Livestock and climate change
2.2. Livestock impact and mitigation measures
2.3. Sequestering carbon and mitigating carbon emissions
2.4. Methane mitigation strategies
2.4.1. Enteric methane mitigation through nutrition
2.5. Mitigation through manure management
2.6. Animal genetics Improvement
2.7. Animal health and longevity

3) CONCLUSION

4) RECOMENDETION

5) REFERANCE

List of tables

Table 1. Livestock species that contribute to GHG emission

Table 2. Global Warming Potential (GWP) of GHGS

Table 3. Methane emission from enteric fermentation indigenous cattle in Ethiopia

Table 4. Estimated development of methane emission from animal manure

Fig. 1. Different enteric methane mitigation strategies

Abbreviation

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Acknowledgement:

God, the Almighty, helped me to pass through tough times that cannot be forgotten in every corner of my life. Had it not been the will of God, nothing would have been possible. So, I would like to thanks my GOD.

I would like to extend my thanks to Kassahun Desalegn(MSC), my advisor, whom I found to be helpful in guiding , Material and commenting me on the current topic writing paper.

Abstract

The objective of this review is to point out that the global dialog on reducing greenhouse gas emissions in animal agriculture has, thus far, not adequately considered animal welfare in proposed climate change mitigation strategies. Many suggested approaches for reducing emissions, most of which could generally be described as calls for the intensification of production, can have substantial effects on the animals. Climate change is seen as a major threat to the survival of many species, ecosystems and the sustainability of livestock production systems in many parts of the world. As per estimates, about 12.5% of total emissions of greenhouse gases are related to livestock production. This contribution is even higher (18%) when the deforestation related to the expansion of livestock production area is also considered to meet the growing demand of animal products. Livestock contributes about 9% of total carbon dioxide production emissions, 37% of methane, and 64% of nitrous oxide emissions throughout production process. There is an urgent need to integrate these other sustainability measures into GHG mitigation assessments. Mitigation in reducing emissions can be achieved in different ways related to animal feeding and management, manure collection, storage, improved animal waste management through energy (biogas) recovery, and management of crops fed to the livestock by bringing more drastic changes of the whole production system. A number of techniques exist to reduce methane emissions from enteric fermentation from ruminants. Improving the genetic potential of animals through planned cross-breeding or selection within a breed, and achieving this genetic potential through proper nutrition and improvements in reproductive efficiency, animal health and reproductive lifespan are effective and recommended approaches for improving animal productivity and reducing GHG emissions per unit of product. There are several factors which need to be considered for selection of best options for methane emission reduction: these include climate, economic, technical and material resources, existing manure management practices, regulatory requirements etc. Generally the methane mitigation strategies can be grouped under three broader headings viz., manage mental, nutritional and advanced biotechnological strategies.

1) INTRODUCTION

Climate change is seen as a major threat to the survival of many species, ecosystems and the sustainability of livestock production systems in many parts of the world. Green house gases (GHG) are released in the atmosphere both by natural sources and anthropogenic (human related) activities. An attempt has been made in this article to understand the contribution of ruminant livestock to climate change and to identify the mitigation strategies to reduce enteric methane emission in livestock. The GHG emissions from the agriculture sector account for about 25.5% of total global radioactive forcing and over 60% of anthropogenic sources. Animal husbandry accounts for 18% of GHG emissions that cause global warming (Sarah, 2010).

Climate change mitigation strategies often use the term, “sustainable intensification.” Yet, societal norms related to the way we treat animals and use them in agriculture are changing and some past practices are no longer as widely accepted. Intensification of animal farming may not ever truly be sustainable, unless, among other things, there is concomitant attention to the health and behavioral needs of the animals, a meaningful effort to provide them with a life worth living. There is an urgent need to integrate these other sustainability measures into GHG mitigation assessments (Sara Shields * and Geoffrey Orme-Evans, 2015).

Mitigation in reducing emissions can be achieved in different ways related to animal feeding and management, manure collection, storage, improved animal waste management through energy (biogas) recovery, and management of crops fed to the livestock by bringing more drastic changes of the whole production system. Several manure management practices have a significant potential for decreasing GHG emission from manure, like dietary management, storage, dietary manipulation, filtration, manure acidification, composting etc.Economically feasible mitigation options in the reductionof excess protein in the diet of ruminant and non- ruminantspecies exist .Increasing efficiency of animal production can be a very effective strategy for reducing GHG emissions per unit of livestock product improving the genetic potential of animals through planned cross-breeding or selection within a breed, and achieving this genetic potential through proper nutrition and improvements in reproductive efficiency, animal health and reproductive life span are effective and recommended approaches for improving animal productivity and reducing GHG emissions per unit of product (Wageningen,2014). According to ( Havlík et al. 2014), Feed production and processing and enteric fermentation in ruminants constitute the two main sources of emissions, representing 45 percent and 39 percent of global livestock sector emissions, respectively. Manure storage and processing represent 10 percent of emissions, the remainder being attributable to processing and transportation of animal products. Technologies and practices that help reduce emissions exist but are not widely used due to a number of reasons, such as adoption costs and conflicting objectives and standards (e.g. animal welfare). Those that improve production efficiency at animal and herd levels, including feeding, breeding, health and reproduction management, also have productivity co-benefits.

Plant secondary compounds (tannins and saponins) are more important as ruminant feed additives, particularly on CH4 mitigation strategy because of their natural origin in opposition to chemicals additives. Tannins containing plants, the anti methanogenic activity has been attributed mainly to condensed tannins. According to Beauchemin et al., 2008, there are two modes of action of tannins on methanogenesis: a direct effect on ruminal methanogens and an indirect effect on hydrogen production due to lower feed degradation. Also, there is evidence that some condensed tannins (CT) can reduce CH4 emissions as well as reducing bloat and increasing amino acid absorption in small intestine. Methane emissions are also commonly lower with higher proportions of forage legumes in the diet, partly due to lower fiber contact, faster rate of passage and in some case the presence of condensed tannins (Metha Wanapat, 2012).An important consideration may be the emissions cost of extracting tannins from plants for use as additives compared with that present in plants and use of the plants for enteric CH4 mitigation. Generally, the livestock sector contribution to climate change necessitates comprehensive and immediate action by policy makers, producers, and consumers. Enhanced regulation is required in order to hold facilities accountable for their GHG emissions.

Objective

- To Review Livestock and climatic change Mitigation strategies.

2) Literature Review

2.1. Livestock and climate change

The major global warming potential (GWP) of livestock production worldwide comes from the natural life processes of the animals.The main sources of global anthropogenic methane emissions include enteric fermentation in ruminant species (29%), rice cultivation (10%), and decomposition of manure under anaerobic and warm conditions (4%). Agricultural fields (4%), forests (16%), and grasses and woodlands (20%) are responsible for approximately 40%, of global black carbon emissions of 7.6 million metric tons per year (Wageningen, D 2014).

Much of the global GHG emissions currently come from enteric fermentation and manure from grazing animals and traditional small-scale mixed farming in developing countries.Ruminant livestock has been recognized as a major contributor to greenhouse gases (Seinfeld et al., 2006). Livestock account for mainly 80% of all emissions from the Agricultural sector. Emissions into the air by any animal production system can be problematic in terms of pollutants and toxicity and in terms of odor and the perception of air quality by human neighbors. The three major greenhouse gases (GHGs) are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). CH4 also has serious impact on high atmosphere ozone formation (Veerasamy Sejian and S. M. K. Naqvi (2012).As per estimates, about 12.5% of total emissions of greenhouse gases are related to livestock production .This contribution are even higher (18%) when the deforestation related to the expansion of livestock production area is also considered to meet the growing demand of animal products. Livestock contributes about 9% of total carbon dioxide production emissions, 37% of methane, and 64% of nitrous oxide emissions throughout production process (IJAIR, 2015). According to (Sara Shields * and Geoffrey Orme-Evans,2015), About 44% of the emissions generated by livestock are CH4, which is released during enteric fermentation (eructation in ruminants) and emitted from manure decomposition; 27% are in the form of CO2 emitted during the production and transport of animal products and feed, and 29% are N2O attributable to manure and fertilizer And also (According to Steinfeld et al., 2006), Livestock contribute 18% of global anthropogenic greenhouse-gas (GHG) emissions . The main greenhouse gases from livestock systems are methane from animals (25%), carbon dioxide from land use and its changes (32%), and nitrous oxide from manure and slurry (31%). Though GHG emissions may come from non- ruminant herbivores, wild animals and poultry, but their contributions are negligible. Ruminants emit over 75% of the total carbon dioxide emissions from livestock. According to (J,.Dijkstra Ousting, 2013), five major sources of emissions along livestock supply chain Land use and land using chain , Feed production , Animal production, Manure management, and Processing and international transport.

The development of management strategies to mitigate CH4 emissions from ruminant livestock is possible and desirable. Not only can the enhanced utilization of dietary ‘C’, improve energy utilization and feed efficiency hence animal productivity, but a decrease in CH4 emissions and also reduce the contribution of ruminant livestock to the global CH4 inventory(Wageningen,2014).

Table 1. Livestock species that contribute to GHG emission and their emission sources category

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Source (Bayu Nebsu & Asefa Tadesse (2015))

Table.2. Global Warming Potential (GWP) of GHGS

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Source: (Veerasamy Sejian and S. M. K. Naqvi (2012))

2.2. Livestock impact and mitigation measures

Overall livestock activities contribute 12.5-18% of total GHG emissions from five major sectors. GHG emissions from livestock have been long recognized to be a function of the efficiency of livestock production and of total number of livestock reared. So improved productivity is essential to reduce emissions. There are various emission reduction options from ruminant production. Mitigation in reducing emissions can be achieved in different ways related to animal feeding and management, manure collection, storage, improved animal waste management through energy (biogas) recovery, and management of crops fed to the livestock by bringing more drastic changes of the whole production system ( Rama Prasad J.,2015 ).

Agriculture is recognized as a sector with such potential, and farmers, herders, ranchers and other land users could and should be part of the solution. Therefore, it is importantto identify mitigation measures that are easy to implement and cost effective in order to strengthen the capacity of local actors to adapt to climate. The livestock production system contributes to global climate change directly through the production of GHG emissions and indirectly through the destruction of biodiversity, the degradation of land, and water and air pollution. There are three main sources of GHG emissions in the livestock production system: the enteric fermentation of animals, manure (waste products) and production of feed and forage (field use) .Indirect sources of GHGs from livestock systems are mainly attributable to changes in land use a deforestation to create pasture land. Mitigation of GHG emissions in the livestock sector can be achieved through various activities, including: Different animal feeding Management, Manure management (collection, storage, spreading) (Dourmad et al., 2008).

According to Gerber et al., 2011) ,shown that non CO2 greenhouse gas (GHG) emissions (i.e. enteric Methane (CH4) and nitrous oxide (N2O)] are inversely related to animal productivity .Higher producing animals consume more feed, produce more manure, and emit greater absolute amount Of GHG from enteric fermentation or during manure storage and application or deposition than low-producing animals. Converted per unit of animal product, however, higher-producing animals usually have lower GHG emissions than low-producing animals. Therefore, enhancing animal productivity is usually a successful strategy for mitigating GHG emissions from livestock production systems ((Gerber et al., 2011).

2.3. Sequestering carbon and mitigating carbon emissions

Carbon dioxide is the most important GHG, which has significant direct-warming impact on global temperature rise because of volume of its emission. Amount of carbon release from changes in the land use and land degradation are higher. Livestock offers a significant potential for carbon sequestering in the form of improved pastures. Improved grassland management is major area where carbon losses from soil can be reversed. Improved grassland management can facilitate better breeding: reducing the number of replacement heifers, reaching slaughter weight at an earlier age, increasing milk production, bringing higher pregnancy rates, etc. This in turn could reduce GHG emissions per unit product, despite the fact that none of the practices mentioned above directly reduce emissions (Rama Prasad J., 2015).

The most promising practices for reducing enteric CH4 emissions and for sequestering soil C in grazing lands could abate up to 379 MtCO2-eq yr−1 of emissions, which is equivalent to 11 % of annual global ruminant GHG emissions. Around two thirds of this potential possible at a carbon price of $20 tCO2-eq−1, a price level that has been observed in Kyoto-compliant carbon markets in the past, but distinctly above current market price (Henderson et al. (2015).

According to Abridged, 2014 ), estimates between 0.7 and 1.6 Gt CO2e per year could be sequestered in cropland and grazing land soils and in agro forestry systems by 2030. It is possible to sequester more carbon in agricultural lands, both in the soil and in above-ground biomass through a range of soil, crop, and livestock management practices. However, there continues to be a great deal of uncertainty in the science of soil carbon sequestration, the degree to which carbon sequestration practices are economically viable for farmers, and the availability of biomass. Additionally, carbon sequestration is complicated by the realities of saturation and permanence. Levels of carbon in the soil and above-ground biomass eventually reach saturation, at which point additional sequestration is not possible. In the future, that carbon can also be released back into the atmosphere depending on the crop management practice and climatic conditions . Carbon stores in grazing lands can be protected and increased through a variety of measures that promote productivity of grasses. Improved pasture management practices include managing stocking rates, timing and rotation of livestock, introduction of grass species or legumes with higher productivity, and application of biochar, compost, fertilizer, or irrigation to increase productivity. All of these practices can increase soil carbon storage.

2.4. Methane mitigation strategies

Methane is produced in ruminant as a by-product of enteric fermentation, whereby carbohydrates are broken down by bacteria in the digestive tract. The amount of methane that is produced depends on: The type of digestive tract. Ruminant livestock have an expansive chamber, the rumen, which fosters extensive enteric fermentation and high CH4 emissions. The main ruminant livestock are cattle, goats, sheep, and camel. Non-ruminant livestock (horses, mules, asses) and mono-gastric livestock (poultry) have relatively lower CH4 emissions because much less CH4-producing digestion takes place in their digestive systems. Among ruminant species methane emission from sheep and goat are considered to be small to quantify. In general methane production by ruminant livestock is influenced by dietary characteristics as well as the fermentation conditions in the rumen. In addition to the above one methane production from enteric fermentation depends on production level, stage of lactation, pregnancy, age, size of livestock (feed intake is positively related to animal size, growth rate, and production e.g., milk production, or pregnancy) and management related interventions like grazing regime, feeding regime, housing and milking (IPCC, 2006).

CH4 mitigation strategies can be broadly divided into preventative and ‘end of pipe ‘options. Preventative measures reduce carbon/nitrogen inputs into the system of animal husbandry, generally through dietary manipulation and, while a reduction in the volume of CH4 emitted per animal may result, this is often secondary to the (primary) objective of improved productive efficiency. Alternatively, ‘end of pipe’ options reduce or inhibit the production of CH4 (methanogenesis) within the system of animal husbandry (Sejian et al., 2011). There are several factors which need to be considered for selection of best options for methane emission reduction: these include climate, economic, technical and material resources, existing manure management practices, regulatory requirements etc. Generally the methane mitigation strategies can be grouped under three broader headings viz., manage mental, nutritional and advanced biotechnological strategies (Sejian et al., 2011).

Ruminants produce GHGs in a number of ways, directly through enteric fermentation (methane), nitrogen excretion (nitrous oxide) and stored manure (methane and nitrous oxide) .Indirectly through use of fossil fuels and electric power in animal production systems, and use of feed stuffs for their feeding that have incurred emission of GHG in their production. In general methane production in ruminants represents 4-12% of gross energy intake (GEI) due to inefficiency in converting feed energy. It is not only environmental hazard but also loss of productivity to the animal. Methane originates from anaerobic microbial fermentation process, in reticules-rumen of ruminants. Other end products of fermentation are microbial biomass and volatile fatty acids (acetic, prop ionic and butyric). Several factors like dietary characteristics and fermentation conditions influence the methane production in the rumen. It is widely accepted that dietary alterations and composition (roughages to concentrate ratio or the fiber, starch, sugars and protein content of the feed) affect rumen functioning and animal performance. So basic principle to reduce methane emission in the rumen should be to increase the digestibility of the feedstuffs either through modifying the feed or by manipulation of rumen fermentation. When the diet is poor methane emissions are higher. The most promising approach for reducing emissions from livestock sector is by improving productivity and efficiency of livestock production (Rama Prasad J., 2015).

Among Ethiopian livestock species the major contributor to CH4 emission are cattle which account for 83% of emission. Cattle also represent a large portion of Ethiopian livestock population. Detailed country-specific data (input data) required for determination of feed intake for cattle species are presented. IPCC, 2006).

Table 3. Methane emission from enteric fermentation indigenous cattle in Ethiopia

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Source, CSA, 2013

2.4.1. Enteric methane mitigation through nutrition

More recently the nutritional mitigation strategy to reduce enteric methane emission from ruminants was extensively reviewed. A number of techniques exist to reduce methane emissions from enteric fermentation from ruminants. These methods include, improving the quality of the roughage, improving grazing practices, use of rotational grazing, inclusion of legumes, feeding highly digestible forages. Increasing forage digestibility and digestible forage intake will reduce methane emission from rumen fermentation (Rama Prasad J, 2015).

Mitigation of GHG emissions in the livestock sector can be achieved through various activities, including: Different animal feeding management, Manure management (collection, storage, preading), Management of feed crop production, the contribution the livestock sector can make to the reduction of emissions varies. Possible mitigation options include composition of feed has some bearing on enteric fermentation and the emission of CH4 from the rumen or hindgut. The volume of feed intake is related to the volume of waste product. The higher the proportion of concentrate in the diet, the lower the emissions of CH4, (Dourmad, et al., 2008).

2.4.1.1. Dietary manipulation

The chemical composition of diet is an important factor which affects rumen fermentation and methane emission by the animals. Improvement in the digestibility of lignocelluloses feeds with different treatments also resulted in lower methanogenesis by the animals. Wheat straw treated with urea (4kg urea par 100kg DM) or urea plus calcium hydroxide (3kg urea+3 kg calcium hydroxide per 100kg DM) and stored for 21 days before feeding, reduced methane emission from sheep. The treatment of straw with urea and urea molasses mineral block lick caused a reduction of 12-15% methane production and the molar proportion of acetate decreased accompanied with an increase in propionate production. On inclusion of green maize and be seem in the ration, methanogenesis decreased significantly. By increasing the concentrate level in the paddy straw based diet there was a depression in methane production accompanied with an increase in propionate concentration in the rumen liquor (Agrawal & Kamra, 2010).

The most successful methane inhibitors tested in vivo are bromochromomethane (BCM), 2bromoethanesulfonate(2.BES), chloroform and cytodoxins. Among thesecompounds tested bromochromomethane (BCM) is the effective enteric methane inhibitor, but it is a banned compound in many countries of the world because it is an ozone depleting compound (IJAIR, 2015).BCM can be used as an antimethanogenic compound to decrease methane production. BCM supplementation at 0.3 g/100 kg of body weight (BW) significantly decreased methane production and methanogen abundance in Japanese goats, lactating dairy goats, steers, and Sprague-Dawley rats. BCM inhibits methanogenesis by reacting with coalmine. Coalmine-dependent enzymes, including coalmine-dependent methionine syntheses, methylmalonyl-coenzyme A (Coal) mutate, and glutamate mutate, contribute to the bacterial metabolism under physiological conditions (Rama Prasad J, 2015).

Feed resources for ruminants are mainly agricultural by-products, especially in the tropical countries where the roughage resources are in shortage during the dry season. These resources have low nutritive values with low crude protein (CP) but with high levels of lingo-cellulosic, hence can reduce on animal production. Protein is the most important factor in maintaining the rumen ecosystem, stimulating dry matter intake as well as digestibility, and leading to high animal performance. Therefore, supplementation of the diet with protein concentrate will enhance rumen bacterial population, improving intake and digestibility. However, the price of concentrate is relatively high and not always available. To solve this problem, finding locally available protein supplemental resources especially fodder trees and shrub legumes such as Leucaena leucocephala (Luciana) or Flemingia macrophylla have been recommended. Luciana, a local available tree legume, was used for ruminants due to its good characteristics such as high protein; palatability, vitamin, and mineral especially sulfur content, which positively effects microbial populations. In addition, Luciana has high digestibility of protein and dry mater (DM) at 60 to 70%. Moreover, Luciana has been reported to contain plant secondary compounds such as condensed tannin (CT), which could be beneficial in reducing protozoal populations leading to a reduced emission of ruminal methane. However, there is still limited data on the use of Luciana silage (LS) as high quality roughage for ruminants and its effect on rumen ecology and performances. Therefore, the objective of this study was to investigate the effect of replacing rice straw (RS) with LS levels on microbial populations and microbial protein synthesis in dairy steers (Metha Wanapat, 2017).

Fig. 1. Different enteric methane mitigation strategies

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2.4.1.2. Adding lipid to the diet

Dietary fat seems a promising nutritional alternative to depress ruminal methanogenesiswithout decreasing luminal pH as opposed to concentrates (Sejian et al., 2011). Addition ofoils to ruminant diets may decrease CH4 emission by up to 80% in vitro and about 25% invivo (Singh, 2010). Lipids cause depressive effect on CH4 emission by toxicity tomethanogens, reduction of protozoa numbers and therefore protozoa associatedmethanogens, and a reduction in fiber digestion. Oils containing laurel Acid and mysticacid are particularly toxic to methanogens. The dietary lipids have been reported to suppress the methane emissions when added in the rations in the range of 6-8%, but are also cost effective. When fed at the rate of less than 8% in the diet, at 10 g /Kg DM increase in dietary fat would decrease methane yield by 1g/Kg DM in cattle and 2.6 g/Kg DM in sheep. High oil by-product feeds such as distillers grains and meals from bio-diesel industry can serve as cost effective sources of dietary lipids with potential methane suppressing effect (Rama Prasad J.,2015).

Mitigation of greenhouse gas emissions in livestock production. Their mitigating potential, however, has not been well-established and in some cases CH4 production may increase due to increased fiber intake. There are a large number of non-traditional oilseeds being investigated as bio fuel feedstock that, if available, may be used as livestock feed and have a beneficial effect on animal productivity (through improvements in energy and protein supply), including a CH4-mitigating effect (FAO,Rome,2013).

Lipids, such as fatty acids and oils, are options for feed supplementation that have been investigated both in vitro and in vivo for their effects on methanogenesis. Increased lipid content in the feed is thought to decrease methanogenesis through inhibition of protozoa, increased production of propionic acid, and by “biohydrogenation of unsaturated fatty acids. Unsaturated fatty acids may be used as hydrogen acceptors as an alternative to the reduction of carbon dioxide. Also, fatty acids are thought to inhibit methanogens directly through binding to the cell membrane and interrupting membrane transport (SE.Hook, 2010).

2.4.1.3. Plant secondary metabolites

The term plant secondary metabolite is used to describe a group of chemical compounds found in plants that are not involved in the primary biochemical processes of plant growth and reproduction (Agrawal & Kamra, 2010). These compounds might function as a nutrient store and defense mechanisms which ensures survival of their structure and reproductive elements protecting against insect or pathogen predation or by restricting grazing herbivores.(Rama Prasad J ., 2015).Many varieties of plant secondary compounds, specially tannins, spooning etc. are promising options. Hydrolysable and condensed tannins may offer an opportunity to reduce enteric methane. They reported decreased enteric methane emission from 6-27%. It has been reported that anti methanogenic effect of tannins depend on application rate and is positively related to the number of hydroxyl groups in their structure and directly affecting rumen methanogenesis. Tea spooning seems to have great potential. Extracts from plants such as rhubarb and garlic could decrease methane emission, but long term effectsareyet to be established (Lincoln, Nebraska August, 2015).

Manipulation of the rumen microbial ecosystem to enhance fibrous feed digestibility ,reduce methane emission and reduce nitrogen excretion by ruminants such as to improve their performance are some of the most important goals for animal nutritionists. Currently, utilization of feed additive has proved to be useful strategy to improve the efficiency of energy and protein utilization in the ruminant. According to (Ngamseang et al., 2006), One of possible alternatives is using the secondary compound in natural plants such as saponins, tannins, and essential oils. Mangos teen peel contains high amount of secondary compounds, especially condensed tannin (15.8%) and saponin (9.8%). Poungchompu et al. (2009) reported that mangosteenpeel containing condensed tannin and saponin caused changes in ruminal microorganism and fermentation end-products. Garlic is another kind of herb that has been used by humans as a source of antimicrobial agents for the gastrointestinal. Therefore, it could manipulate rumen fermentation. Garlic supplementation decreased in the proportion of acetate and increased proportion of propionate and butyrate, inhibition of methanogenesis and decreased in the CH4: VFA ratio .According to Beauchemin et al., 2008, there are two modes of action of tannins on methanogenesis: a direct effect on luminal methanogens and an indirect effect on hydrogen production due to lower feed degradation. Also, some condensed tannins (CT) can reduce CH4 emissions as well as reducing bloat and increasing amino acid absorption in small intestine.

Condensed tannins can reduce the rate of digestion, but this will have little effect on animals fed at the maintenance level of intake because the rumen can accommodate more feed; however, in a lactating animal, production can be reduced because of bulk fill limitations on feed intake (Grainger et al., 2009a). An important consideration may be the emissions cost of extracting tannins from plants (e.g. from Acacia mearnsii) for use as additives compared with that present in plants and use of the plants for enteric CH4 mitigation. Tannins, supplemented through the diet, are undesirable for monogastric species, particularly when low-protein diets are fed (Goel and Makkar, 2012).

The risk of impaired rumen function and animal productivity with tannins is greater than with saponins and, for decreasing enteric CH4 production, the concentration range for tannins is narrower than for saponins. In, hydrolysable and condensed tannins are plant bioactive components that may offer an opportunity to reduce enteric CH4 production, although intake and animal production may be compromised. The agronomic characteristics of tanniferous forages must be considered Mitigation practices when they are discussed as a GHG mitigation option. Tea saponins seem to have potential, but more and long-term studies are required before they could be recommended for use. Most essential oils or their active ingredients do not reduce CH4 production and, when CH4 production was reduced in vivo, their long-tem effects were not established (Tekippe et al., 2011). Numerous studies have demonstrated that Saponins and Saponin containing plants have toxic effects on protozoa. Forages containing condensed tannins have been shown todecrease methane production by the ruminants. Tannins present in Calendar clothiersreduced nutrient degradation and methane release per gram of organic matter degraded in in vitro experiments with rumen simulation technique (Hess et al., 2003).

2.4.1.4. Feeds and feeding management

More recently the nutritional mitigation strategy to reduce enteric methane emission from ruminants was extensively reviewed. A number of techniques exist to reduce methane emissions from enteric fermentation from ruminants. These methods include, improving the quality of the roughage, improving grazing practices, use of rotational grazing, inclusion of legumes, feeding highly digestible forages. Increasing forage digestibility and digestible forage intake will reduce methane emission from rumen fermentation (Rama Prasad J., 2015).

Composition of feed has some bearing on enteric fermentation and the emission of CH4 from the rumen or hindgut. The volume of feed intake is related to the volume of waste product. The higher the proportion of concentrate in the diet, the lower the emissions of CH4. Increasing feed efficiency and improving the digestibility of feed intake are potential ways to reduce GHG emissions and maximize production and gross efficiency, as is lowering the number of heads. All livestock practices – such as genetics, nutrition, reproduction, health and dietary supplements and proper feeding (including grazing) management - that could result in improved feed efficiency need to be taken into account. Proper pasture management through rotational grazing would be the most cost-effective way to mitigate GHG emissions from feed crop production. Animal grazing on pasture also helps reduce emissions attributable to animal manure storage. Introducing grass species and legumes into grazing lands can enhance carbon storage in soils (Dourmad, et al, 2008).

Feeding steam flaked- or high-moisture corn decreases enteric methane production by about 20% compared to feeding dry rolled corn-based high-concentrate finishing diets because of more efficient digestion of starch in the rumen. Steam flaking may also decrease methane emissions from manures because it decreases the concentration of starch in the feces. (Hales et al., 2012).

2.4.1.4.1. Feed intake

There is a clear relationship between feed DM digestibility, concentrate feed and the pattern of rumen fermentation. Feed intake is the important variable in methane emission. Addition of starch and lipid combinations to the diets of feedlot bulls reduced GHG emissions, inclusion of concentrate feed at above 35-40% of DM is likely reduce methane emission. Supplementation with small amounts of concentrates in the feed is likely to increase animal production and decrease methane emission (Rama Prasad. Jwalapur, 2015).

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