Scholarly article on topic 'Dietary sources and their effects on animal production and environmental sustainability'

Dietary sources and their effects on animal production and environmental sustainability Academic research paper on "Animal and dairy science"

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Animal Nutrition
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{"Animal production system" / Feeding / "Feed resources" / Environment / Nutrition}

Abstract of research paper on Animal and dairy science, author of scientific article — Metha Wanapat, Anusorn Cherdthong, Kampanat Phesatcha, Sungchhang Kang

Abstract Animal agriculture has been an important component in the integrated farming systems in developing countries. It serves in a paramount diversified role in producing animal protein food, draft power, farm manure as well as ensuring social status-quo and enriching livelihood. Ruminants are importantly contributable to the well-being and the livelihood of the global population. Ruminant production systems can vary from subsistence to intensive type of farming depending on locality, resource availability, infrastructure accessibility, food demand and market potentials. The growing demand for sustainable animal production is compelling to researchers exploring the potential approaches to reduce greenhouse gases (GHG) emissions from livestock. Global warming has been an issue of concern and importance for all especially those engaged in animal agriculture. Methane (CH4) is one of the major GHG accounted for at least 14% of the total GHG with a global warming potential 25-fold of carbon dioxide and a 12-year atmospheric lifetime. Agricultural sector has a contribution of 50 to 60% methane emission and ruminants are the major source of methane contribution (15 to 33%). Methane emission by enteric fermentation of ruminants represents a loss of energy intake (5 to 15% of total) and is produced by methanogens (archae) as a result of fermentation end-products. Ruminants׳ digestive fermentation results in fermentation end-products of volatile fatty acids (VFA), microbial protein and methane production in the rumen. Rumen microorganisms including bacteria, protozoa and fungal zoospores are closely associated with the rumen fermentation efficiency. Besides using feed formulation and feeding management, local feed resources have been used as alternative feed additives for manipulation of rumen ecology with promising results for replacement in ruminant feeding. Those potential feed additive practices are as follows: 1) the use of plant extracts or plants containing secondary compounds (e.g., condensed tannins and saponins) such as mangosteen peel powder, rain tree pod; 2) plants rich in minerals, e.g., banana flower powder; and 3) plant essential oils, e.g., garlic, eucalyptus leaf powder, etc. Implementation of the -feed-system using cash crop and leguminous shrubs or fodder trees are of promising results.

Academic research paper on topic "Dietary sources and their effects on animal production and environmental sustainability"

Animal Nutrition

" KeAi SE

Accepted Manuscript

Dietary sources and their effects on animal production and environmental sustainability

Metha Wanapat, Anusorn Cherdthong, Kampanat Phesatcha, Sungchhang Kang

PII: S2405-6545(15)30016-0

DOI: 10.1016/j.aninu.2015.07.004

Reference: ANINU 18

To appear in: Animal Nutrition Journal

Received Date: 17 July 2015 Accepted Date: 27 July 2015

Please cite this article as: Wanapat M, Cherdthong A, Phesatcha K, Kang S, Dietary sources and their effects on animal production and environmental sustainability, Animal Nutrition Journal (2015), doi: 10.1016/j.aninu.2015.07.004.

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Running head: Dietary sources for animal production and environment

Dietary sources and their effects on animal production and environmental sustainability

Metha Wanapat^*, Anusorn Cherdthonga, Kampanat Phesatchaa, Sungchhang Kangb

aTropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand Agricultural Unit, Department of Education, National Institute of Education, Phnom Penh, 12401, Cambodia

* Corresponding author.

E-mail (M. Wanapat)


Animal agriculture has been an important component in the integrated farming systems in developing countries. It serves in a paramount diversified role in producing animal protein food, draft power, farm manure as well as ensuring social status-quo and enriching livelihood. Ruminants are importantly contributable to the well-being and the livelihood of the global population. Ruminant production systems can vary from subsistence to intensive type of farming depending on locality, resource availability, infrastructure accessibility, food demand and market potentials. The growing demand for sustainable animal production is compelling to researchers exploring the potential approaches to reduce greenhouse gases(GHG) emissions from livestock.Global warming has been an issue of concern and importance for all especially those engaged in animal agriculture. Methane (CH4) is one of the major GHG accounted for at least 14% of the total GHG with a global warming potential 25-fold of carbon dioxide and a 12-year atmospheric lifetime. Agricultural sector has a contribution of 50 to 60% methane emission and ruminants are the major source of methane contribution (15 to 33%). Methane emission by enteric fermentation of ruminants represents a loss of energy intake (5 to 15% of total) and is produced by methanogens (archae) as a result of fermentation end-products. Ruminants' digestive fermentation results in fermentation end-products of volatile fatty acids (VFA), microbial protein and methane production in the rumen. Rumen microorganisms including bacteria, protozoa and fungal zoospores are closely associated with the rumen fermentation efficiency. Besides using feed formulation and feeding management, local feed resources have been used as alternative feed additives for manipulation of rumen ecology with promising results for replacement in ruminant feeding. Those potential feed additive practices are as follows: i) the use of plant

extracts or plants containing secondary compounds (e.g. condensed tannins and saponins) such as mangosteen peel powder, rain tree pod; ii) plants rich in minerals, e.g., banana flower powder; and iii) plant essential oils, e.g., garlic, eucalyptus leaf powder, etc. Implementation of the -feed-system using cash crop and leguminous shrubs or fodder trees are of promising results.

Keywords: Animal production system, Feeding, Feed resources, Environment, Nutrition 1. Introduction

Livestock production is undertaken in a multitude of ways across the planet, providing a large variety of goods and services, and using different animal species and different sets of resources, in a wide spectrum of agro-ecological and socio-economic conditions (Kearney, 2010).Global livestock systems occupy about 30% of the planet'sice-free terrestrial surface area (Steinfeld et al.,2006) and are a significant global asset with a valueof at least $1.4 trillion (Thornton et al., 2010). Currently, livestock is one of the fastest growing agricultural subsectors in developing countries. This growth is driven by the rapidly increasing demand for livestock products, this demand being driven by population growth, urbanization and increasing incomes in developing countries (Delgado, 2005). This combination of growing demand in the developing world and stagnant demand in industrialized countries represents a major opportunity for livestock keepers in developing countries, where most demand is met by local production, and this is likely to continue well into the foreseeable future (Thornton et al., 2010). Along with an exploration of food consumption trends and projections to 2050, both globally and for different regions of the world, the drivers largely responsible for these observed consumption trends will be examined (Kearney, 2010).At the same time, the expansion of agricultural production needs to take place in a way that allows the less well-off to benefit from increased demand and that

moderates its impact on the environment. Although integral to many farming systems, livestock production is nevertheless associated with many impacts that are deemed socially undesirable (Moran and Wall, 2011). Whereas animal welfare concerns have been documented for centuries, damage attributed to and responsibility for greenhouse gas (GHG) emissions are more recent concerns. Enteric methane (CH4) emission in ruminants, which is produced via fermentation of feeds in the rumen and lower digestive tract by methanogenic archaea, represents a loss of 2 to 12% of gross energy of feeds and contributes to global greenhouse effects. Globally, about 80 million tonnes of CH4 is produced annually from enteric fermentation mainly from ruminants. Therefore, CH4 mitigation strategies in ruminants have been focused onobtaining economic as well as environmental benefits (Patra, 2011).

2. Global animal production systems

Production environments, and the intensities and purposes of production, vary greatly within and across countries (Steinfeld et al., 2006). Animal productionsystems have been categorised on the basis of agro-ecological opportunities and demand for livestock commodities. In many of these systems, the livestock element is interwoven with crop production, as in the rice/buffalo or cereal/cattle systems of Asia. Animal manure is often essential for maintaining soil fertility, and the role of animals in nutrient cycling is often an important motivation for keeping animals, particularly where this involves a transfer of nutrients from common property resources to private land. Many of these systems that are the result of a long evolution are currently under pressure to adjust to rapidly evolving socioeconomic conditions; large intensive livestock production units, in particular for pig and poultry production, have emerged over the last decades in many developing regions in response to the rapidly growing demand for livestock products. Moreover, the degree to

which each system is integrated into the market economy varies according to a host of factors, perhaps the most important of which is geographical location.The influence of geographical location on market integration is twofold: partly agro-ecological and partly infrastructural. Some areas may have a higher degree of market integration because rainfall and soil conditions are conducive to cash cropping and the production of surpluses; others may lack one or both of these advantages but are compensated by their relative proximity to urban markets and other facilities. Animal production systems can be described into categories as follows ILRI (1995) and Wanapat (1990, 1999).

2.1 Subsistence animal production systems

For the subsistence-oriented household, land and labour are the principal factors of production. Capital investment is limited to non-monetary self-produced equipment, land improvement and livestock raised through natural reproduction. Increases in production are mainly dependent on the weather and on the quantity and quality of those factors of production controlled by the household. These, for example, may include:

• use of surplus labour for bush clearing and erosion control

• use of animal manure to raise soil fertility

• better livestock management practices

Progress in production is likely to be slow but improvements are possible through farming systems research, education and extension programmes. There are few local off-farm employment opportunities. The monetary circuit plays little role in the economy of the mainly subsistence-oriented household. For the subsistence-oriented farm, output and consumption are identical. Such households thus remain largely (but not wholly) unresponsive to price and market signals.Families living under these conditions rarely aim to maximize production, since this would imply specialization, with its attendant risks. Rather,

the goal is to maximize the chances of survival. A mainly subsistence-oriented farmer will be reluctant to shift from a traditional practice to a new technology if doing so incurs greater risk of failure.

2.2 Semi-subsistence animal production systems

A semi-subsistence household produces a considerable proportion of its consumption requirements (60 to 80%). In addition, it will produce cash crops such as vegetables, coffee and tea, and keep livestock for sale. The semi-subsistence producer will therefore be confronted with the risks associated with price fluctuations and with variations in the natural environment. The monetary circuit thus assumes an important role in the semi-subsistence production unit. Such units tend to be more responsive to market and price signals than the subsistence-oriented producers. The higher the share of output being sold on the market, the greater the importance of the monetary circuit in the semi-subsistence production system. The impact of market and price signals will ultimately depend on the degree of market integration.

What are the reasons behind a household's desire to enter the monetary circuit? Answering this question will help us understand the factors which influence production responses. The first step in the transition process from subsistence to more commercialized production may be a need to obtain cash to meet legal or social obligations, such as the payment of school fees or the hosting of a wedding reception. Insofar as such needs are the only purpose of sales, there will be a negative relationship between price and market supply. In other words, the higher the market price, the smaller will be the amounts that need to be sold and vice versa.

As the transition process continues, market supply responses become positive as producers recognise that increasing their cash income enables them to buy other consumer

150 goods which improve their welfare. If these goods are regularly available at local markets,

151 income growth may become an important family goal. Higher income also enables a

152 household to purchase more external inputs (fertilizer, seeds, etc), thus increasing output still

153 further in the future. Finally, cash can also be used to pay interest and principal on credit,

154 opening up greater opportunities for investment and hence the development of new

155 enterprises.Thus, the transition from pure subsistence, through semi-subsistence to more

156 commercial farming will have two interrelated effects on consumption and production in the

157 rural household, namely:

158 • The direct acquisition of consumer goods and services

159 • The further growth of income through increased use of external inputs.

160 For families living under these systems, risk aversion remains an important

161 determinant of household decisions. These producers confront the risks associated with price

162 fluctuation as well as those resulting from climate. Sometimes these will offset one another,

163 as when low yields lead to scarcity, causing market prices to rise, and vice versa. At other

164 times, factors bearing no relationship to yield variations will influence prices. For semi-

165 subsistence producers, innovations with minimal input of external factors of production could

166 be offered.

168 2.3 Intensive (commercial) animal production systems

169 In these systems, the monetary circuit becomes more important than the physical one,

170 which may become less complex as a result of specialisation. These production units tend to

171 be highly responsive to price and market signals, switching enterprises and increasing or

172 decreasing their market involvement in accordance with them. Increases in production are

173 almost certain to involve the use of external inputs and services. Progress in production can

174 be rapid, but dramatic setbacks may occasionally occur. Off-farm employment opportunities

175 are more common and are found nearer home.For families living under these conditions, the

176 allocation of resources will be determined largely by the profit rather than the survival

177 motive. However, although risk aversion plays a smaller part in decision making, households

178 will tend to refrain from fully commercial production if markets are unreliable or if

179 institutional support (access to credit, price stabilisation schemes, animal health services etc)

180 is inadequate.

181 The presence ofcommercialsystems is connected to both demand factorsand supply

182 determinants; areas with high populationdensity and purchasing power, in particular coastal

183 areas in East Asia, Europe and North America, which also haveaccess to ocean ports, show a

184 high prevalence of industrialsystems and import much of the necessary feed (Steinfeld et al.,

185 2006). Incontrast, there are areas with ample feed supplies such asthe mid-western United

186 States of America (USA) andinterior parts of Brazil and Argentina, where industrialsystems

187 rely mainly on local feed surpluses. East andSoutheast Asia strongly dominate industrial

188 monogastrics'production in the developing regions. Southern Brazil isanother industrial

189 production hot spot at world level,while important regional centres of industrial

190 productionare found, for example in Mexico, Colombia, Venezuelaand Chile. Similarly there

191 are major regional centres for theindustrial production of chicken in Nigeria, South Africaand

192 the Middle East.

194 3. Animal protein products consumption demand for increasing global

195 population(WHO, 2013)

196 There has been an increasing pressure on the livestock sector to meet the growing

197 demand for high-value animal protein. The world's livestock sector is growing at an

198 unprecedented rate and the driving force behind this enormous surge is a combination of

199 population growth, rising incomes and urbanization. Annual meat production is projected to

200 increase from 218 million tonnes in 1997-1999 to 376 million tonnes by 2030 (WHO, 2013).

201 There is a strong positive relationship between the level of income and the

202 consumption of animal protein, with the consumption of meat, milk and eggs increasing at

203 the expense of staple foods. Because of the recent steep decline in prices, developing

204 countries are embarking on higher meat consumption at much lower levels of gross domestic

205 product than the industrialized countries did some 20 to 30 years ago.

206 Urbanization is a major driving force influencing global demand for livestock

207 products. Urbanization stimulates improvements in infrastructure, including cold chains,

208 which permit trade in perishable goods. Compared with the less diversified diets of the rural

209 communities, city dwellers have a varied diet rich in animal proteins and fats, and

210 characterized by higher consumption of meat, poultry, milk and other dairy products. Table 1

211 shows trends in per capita consumption of livestock products in different regions and country

212 groups. There has been a remarkable increase in the consumption of animal products in

213 countries such as Brazil and China, although the levels are still well below the levels of

214 consumption in North American and most other industrialized countries.Consumption of

215 meat in the U.S. were highest when compared to the global average. The countries that

216 consume the least amount of meat are in Africa and South Asia; the lowest ten are Sierra

217 Leone, Democratic Republic ofCongo, Mozambique, Sri Lanka, Rwanda, India, Malawi,

218 Guinea, Burundi and Bangladesh. Consumption in these countries is between 3 and 5 kg per

219 capita per year (Speedy, 2003). This is compensatedto some extent in Bangladesh by higher

220 fish consumption (17.5 kg) and in India and Sri Lanka by higher milk consumption (47.5 kg

221 and 35.9 kg, respectively). Milk consumption in the U.S. is 118 kg per capita per year. Many

222 African countries are in the bottom quartile forconsumption of meat plus fish combined.

As diets become richer and more diverse, the high-value protein that the livestock sector offers improves the nutrition of the vast majority of the world. Livestock products not only provide high-value protein but are also important sources of a wide range of essential micronutrients, in particular minerals such as iron and zinc, and vitamins such as vitamin A. For the large majority of people in the world, particularly in developing countries, livestock products remain a desired food for nutritional value and taste. Excessive consumption of animal products in some countries and social classes can, however, lead to excessive intakes of fat.

4. Greenhouse gases and animal contribution

The growing demand for livestock products is likely to have an undesirable impact on the environment. For example, there will be more large-scale, industrial production, often located close to urban centers, which brings with it a range of environmental and public health risks (WHO, 2013). Environmental impacts oflivestock production have historically been confined to more localizedproblems of overgrazing, desertification, and water pollution bypoor waste handling (Moran and Wall, 2011). Such concerns were often offset by recognitionof the cultural significance of livestock and more tangible benefits fromthe use of animal products and manures in farming systems (Moll, 2005).In developing countries, livestock production provides not only food, butalso a wide range of nonfood benefitsincluding income, employment,and many other contributions to rural and social development.The need to respond to global climate change has focused attention onthe main sources of emissions with all significant sources coming underscrutiny (World Bank, 2008). This is largely becausedeveloped countrieshave committed themselves to externally defined emissions reductions(mitigation) targets that must somehow be shared amongst pollutingindustries within their jurisdictional control. Livestock production systemscontribute

an estimated 18% of global anthropogenic GHG emissions (FAO, 2006). These emissions represent a significant proportion for some countries, including New Zealand, Ireland, andthe United Kingdom. The main sources and types of GHG from livestocksystems are methane production from animals (25%), carbon dioxide(CO2) from land use and its changes (32%), and nitrous oxide (N2O) frommanure and slurry management (31%).

5. Strategies in preventing and alleviating GHG especially from animals

Livestock are already well-known to contribute to GHG emissions and accounting for about 18% of the anthropogenic GHG emissions (Steinfield et al., 2006). Among domesticated livestock, ruminant animals (cattle, buffalo, sheep, goats, and camels) produce significant amounts of CH4 and they areproduced in the rumen and hindgut.Fermentation of feeds in the rumen is the largest source of CH4from enteric fermentation. CH4 production from ruminant is a complex process that involves a group of Archaea known collectively as methanogens, which belong to the phylum Euryarcheota (Patra, 2011). During this process, rumen microbes convert ingested organic matter into energy for microbial growth, and into fermentation end-products, including VFA, alcohols, H2, and CO2. The major VFA produced in the rumen include acetate (Ac), propionate (Pr) and butyrate (Bu), which generally account for more than 95% of the total VFA production. Excess reducing power generated during conversion of hexose to Ac or Bu is utilized in part by Pr, but mainly by conversion to CH4 (Moss et al., 2000). Methanogenic archaea are able to take some of these end products and reduce them with H2 to produce CH4 and H2O. Accumulated CH4 and other volatile gases produced in the rumen are eventually expelled through the mouth into the atmosphere via eructation. CH4 emissions in ruminants accounts for 2 to12% of gross energy loss of feeds depending upon the type of diets (Johnson and Johnson 1995). Moreover, Leng (2008) reported that CH4 emitted by the world's farmed ruminant livestock accounts for about one

quarter of all anthropogenic CH4 emission, typically estimated at 80 to 90 Tg/yr (1 Tg-1 million tonnes) of a total of around350 Tg/yr.Therefore, lowering global CH4 emissions

from enteric fermentation is an important part of any effort to reduce anthropogenic GHG emissions and ruminant producers are also seeking to identify and promote good management practices. The current approaches for reducing methane production from ruminants are shown in Table 2.

5.1 Feed managerment

It is well established that increasing the level of concentratein the diet leads to a reduction in CH4 emissions as aproportion of energy intake or expressed by unit of animalproduct (milk and meat) (Matin et al., 2010). A meta-analysis of the bibliographyshowed that the relationship between concentrateproportion in the diet and CH4 production is curvilinear(Sauvant and Giger-Reverdin, 2007). Methane lossesappear relatively constant(6 to 7% of GE intake) for diets containing 30 to40% concentrate and thendecrease rapidly to low values (2 to 3% of GE intake) fordiets containing 80 to 90% concentrate (Martin et al.,2010). Replacing structural carbohydrates from forages(cellulose, hemicellulose) in the diet with non-structuralcarbohydrates (starch and sugars) contained in mostenergy-rich concentrates is associated with increases infeed intake, higher rates of ruminal fermentation andaccelerated feed turnover, which results in large modificationsof rumen physico-chemical conditions and microbialpopulations. A shift of VFA production from acetate towardspropionate occurs with the development of starch-fermentingmicrobes. This results in a lower CH4 productionbecause the relative proportion of ruminal hydrogen sourcesdeclines whereas that of hydrogen sinks increases.However, this low acetate:propionate ratio may not bealways observed in high-concentrate fed animals, that is,young bulls fed maize grain-based diets containing 30 or45% starch had a similar ratio

(2.50 vs. 2.88, respectively). The lower CH4 emissionsfrom bulls fed the diet containing 45% starch compared tothose fed other two diets containing 30% starch (2.5%vs. 6.9% of GE intake, respectively) could be better explainedby a lower ruminal pH (5.06 vs. 5.90, respectively; Martinet al., 2010) and a decrease in protozoal number. The low ruminal pH might also inhibit thegrowth and/or activity of methanogens (Hegarty,1999) and of cellulolytic bacteria. Apositive correlation between cellulolytic bacteria andmethanogens in the rumen of different species (cattle,sheep, llamas, deer) has been shown,except in buffalos. This exception was explained by thefact that F. succinogenes, a non-hydrogen-producing cellulolyticspecies, was the major cellulolytic bacteria of thisanimal species (Matin et al., 2010).

Concerning the effect of the nature of concentrate onmethanogenesis, few direct comparisons have been carriedout. Concentrates rich in starch (wheat, barley, maize) havea more important negative effect on CH4 production thanfibrous concentrates (beet pulp). Substitution of beet pulpby barley in a high concentrate diet (70%) fed to dairy cowsreduced CH4 emissions by 34%. Lovettet al. (2005) reported that this was not the case when freshforages were the main ingredients of the basal diet.Beauchemin et al. (2008) measured CH4 emissionsfrom feedlot cattle fed backgrounding and finishing dietscontaining maize (slowly degradable starch) or barley grain(rapidly degradable starch). Effect of grain source on CH4emissions was conditioned by the production phase.Expressed on the basis of GE intake, CH4 emissions duringthe backgrounding phase were not affected by grainsource, whereas emissions were surprisingly less for themaize finishing diet than for the barley finishing period.The authors suggested that this was mediated through thelower ruminal pH observed with the maize diet ratherthan a shift in the site of digestion from the rumen to theintestines (Matin et al., 2010).

323 5.2 Plant secondary compounds

324 Plant secondary compounds (condensed tannins and saponins) are important ruminant

325 feed additives, particularly for a methane mitigation strategy because of their natural origin as

326 opposed to chemical additives(Wanapat et al., 2013). Anti-methanogenic activity can be

327 attributed to both condensed tannins(CT)and hydrolysable tannins. There are two modes of

328 action of tannins in methanogenesis: a direct effect on ruminal methanogens and an indirect

329 effect on hydrogen production due to lower feed degradation. There is also evidence that

330 some CT can reduce methane emissions while reducing bloat and increasing amino acid

331 absorption in the small intestine. Methane emissions are also commonly lower with higher

332 proportions of forage legumes in the diet, partly due to lower fiber contact, a faster rate of

333 passage and, in some cases, the presence of CT. Supplementation with Phaseolus

334 calcaratus hay at 600 g/animal/day was beneficial for swamp buffaloes fed rice straw as a

335 basal roughage, as it resulted in increased DM intake, reduced protozoal numbers and

336 methane gas production in the rumen, increased N retention as well as improving the

337 efficiency of rumen microbial CP synthesis (Chanthakhoun et al., 2011). Legumes containing

338 CT (e.g. Lotuses) are able to lower methane (based on g/kg DMI) by 12 to 15%

339 (Chanthakhoun et al., 2011). Also, some authors have reported that CT can reduce methane

340 production by 13 to 16% (DMI basis), mainly through a direct toxic effect on methanogens.

341 At an appropriate dose, saponins or saponin-containing plants have been shown to suppress

342 the protozoal population, increase the bacteria and fungi population, the production of

343 propionate, the partitioning factor, the yield and efficiency of microbial protein synthesis and

344 to decrease methanogenesis, all of which improve performance in ruminants. Tannins,

345 especially CT, also decrease methane production and increase the efficiency of microbial

346 protein synthesis(Wanapat et al., 2013).

Saponins are natural detergents found in many plants. Interest has increased in using saponin-containing plants as a possible means of suppressing or eliminating protozoa in the rumen. Decreased numbers of ruminal ciliate protozoa may enhance the flow of microbial protein from the rumen, to increase the efficiency of feed utilization and decrease methanogenesis. Saponins are also known to influence both the composition and number of ruminal bacterial species through specific inhibition or selective enhancement of the growth of individual species. Saponins have been shown to possess strong defaunation properties both in vitro and in vivo which could reduce methane emissions. While extracts of CT and saponins may be commercially available, their cost is currently prohibitive for their routine use in ruminant production systems. However, research is still required on the optimum sources of CT and saponins, the level of CT astringency (chemical composition) and the feeding methods and dose rates required to reduce methane and stimulate animal production (Wanapat et al., 2013).

Mangosteen peel powder (MP) supplementation both for in vitro and in vivo trials significantly increased the production of total VFA (P < 0.05), as well as propionate production, while acetate, butyrate production and the acetate:propionate ratio were significantly decreased (P < 0.05) (Norrapoke et al., 2012).Condensed tannins and saponins contained in MP could contribute to the above effects. These findings showed that MP supplementation did not affect DM intakes, while digestibility and rumen methane production (by estimation using VFA concentration) were significantly decreased (P < 0.05). MP supplementation reduced rumen protozoa production remarkably, while the numbers of the predominant cellulolytic bacteria increased (P < 0.05). In addition, methanogen numbers tended to decrease. However, it was found that mangosteen peel powder significantly increased (P < 0.05) the cellulolytic bacteria population. The CT and saponins present in the MP could influence such changes in the rumen (Wanapat et al., 2013).

5.3 Organic acids

Organic acids (malate, fumarate and acrylate) have beenassayed as diet additives (Morgavi et al., 2010). Fumarate and acrylate has been shown to be themost effective in vitro. In contrast tothe well-documented CH4 production response to organicacids in vitro, responses to dietary supplementation in vivoremain inconclusive and highly variable. For example, nochanges were reported in beef heifers (Beauchemin et al., 2008), whereas up to 16% decreases werereported in beef cattle (Foley et al., 2009), although in thislast study feed intake for organic acid-supplemented animalswas also reduced. An exceptional decrease in CH4production, up to 75%, has been shown with 10%encapsulated fumarate in the diet of lambs without negativeeffect on animal growth (Wallace et al., 2006). Incontrast, encapsulated fumarate had no significant effect inanother trial in dairy cows (McCourt et al., 2008). Furtherresearch is needed with such a product as additive. It hasbeen suggested by Martin (1998) that the high malatecontent in fresh forages at early growth stage, especiallylucerne, could lead to significant changes in rumen microbialfermentation (Matin et al., 2010).

5.4 Ionophores

Ionophore antibiotics such as monensin are usuallyused in ruminants to improve the efficiency ofmeat and milk production (Morgavi et al., 2010). Ionophores do notalter the quantity and diversity of methanogens(Hook et al., 2011), but they change the bacterialpopulation from Gram-positive to Gram-negativeorganisms with a concomitant changein the fermentation from acetate to propionate.This fermentation shift lowers the availability ofH2 for CH4 production by methanogens. Theymight also reduce ruminal protozoal numbers.Relatively high-dose levels might be required tolessen CH4 compared

with doses needed to improvefeed efficiency. Monensin included in dietsat a dose of <20 mg/kg diet may not always haveprofound effect on CH4 production (Beaucheminet al., 2008). Higher doses (24-35 mg/kg diet)decreased CH4 production by 4 to10% (Odongo et al., 2007) with short-termdecreases in CH4 up to 30% at a dose level of33 mg/kg diet (Guan et al., 2006). Unfortunately,some long-term trials suggest that the inhibitionof methanogenesis by ionophores may not persistover time (Guan et al., 2006). It appears thatmonensin can be used for short-term decreases inCH4 emissions, which can also improve efficiencyof feed utilization in ruminants. However, the useof ionophores as feed additives has been bannedin the European Union and is restricted in someother countries as feed additives (Matin et al., 2010).

5.5 Immunisation and biological control

Several biotechnological strategies are currently beingexplored (Matin et al., 2010). A vaccine against three selected methanogensdecreased CH4 production by nearly 8% in Australian sheep(Wright et al., 2004). However, vaccines prepared with adifferent set of methanogen species or tested in other geographicalregions did not elicit a positive response (Wrightet al., 2004). The highly diverse methanogenic communitypresent in animals reared under different conditions (Wrightet al., 2007) and the replacement of the ecological niche leftby the targeted species by another methanogens (Williamset al., 2009) might account for immunisation failures. Therecent completion of the complete genome sequence ofMethanobrevibacter ruminantium by New Zealand scientists( opens the way for the identificationof specific immunological targets that could be common toother methanogens found in the rumen. This informationcould be used for the development of second-generationvaccines (Attwood and McSweeney, 2008).Passive immunisation was also recently assayed usingantibodies, which were produced in laying hens, againstthree

common methanogens present in the digestive tractof animals. Treatments using whole eggs decreased transientlyCH4 production in vitro but the effect was lost at theend of the 24-h incubation (Cook et al., 2008). Up to now,immunisation has not delivered a clear, positive answer inreducing CH4 emissions by ruminants, highlighting the difficultiesof this approach (Morgavi et al., 2010).

5.6 Defaunation

Defaunation, which is theremoval of protozoa from the rumen, has been used toinvestigate the role of protozoa in rumen function, andalso to study the effect on methane production (Hook et al., 2011). Rumenprotozoa, as stated previously, share a symbiotic relationshipwith methanogens, participating in interspecies hydrogentransfer, which provides methanogens with the hydrogenthey require to reduce carbon dioxide to methane. Ithas been estimated that the methanogens associated withthe ciliate protozoa, both intracellularly and extracellularly,are responsible for 9 to 37% of the methane productionin the rumen (Newbold et al., 1995). For this reason, treatments thatdecrease the protozoal population of the rumen, may alsodecrease the protozoa-associated methanogen populationand therefore, decrease the methane production within therumen. Treatments that have been used include coppersulphate, acids, surface-active chemicals, triazine, lipids, tannins,ionophores, and saponins. It has been suggestedthat the effect of defaunation on methane output is dietdependent. Hegarty (1999) found that defaunation reducedmethane output 13%, but the magnitude of reduction variedwith diet. The greatest reduction in methane productionwith defaunation was measured on a high-concentrate diet,likely because protozoa are the predominant source of hydrogenfor methanogenesis on starch-based diets. Although,Hegarty et al. (2007) also found that there was no main effectof protozoa on rumen methane production, when investigatedin chemically-defaunated, defaunated from birth, andfaunated

lambs. Another consideration is whether there arelong-term effects of defaunation on methanogenesis. Morgavi et al. (2010) found methane reductions dueto defaunation to last more than two years, but a study ofionophore supplementation by Guan et al. (2006) found thatreductions in rumen methanogenesis were short-lived andhypothesized this was due to adaptation of ciliate protozoa.Finally, maintenance of defaunated animals can be difficult.A recent study found that transfer of viable protozoa todefaunated animals does not occur readily through contactwith feed or feces of faunated animals, nor with directcontact with faunated animals, but does occur throughcontaminated water (Hook et al., 2011).

5.7 Lipids

Dietary fat seems a promising nutritional alternative todepress ruminal methanogenesis without affecting otherruminal parameters (Wanapat et al., 2013). There are five possible mechanisms by which lipid supplementation reduces methane: reducing fiber digestion (mainly in long chain fatty acids); lowering DMI (if total dietary fat exceeds 6 to 7%); suppression of methanogens (mainly in medium chain fatty acids); suppression of rumen protozoa and to a limited extent through biohydrogenation. Oils offer a practical approach to reducing methane in situations where animals can be given daily feed supplements, but excess oil is detrimental to fiber digestion and animal production. Oils may act as hydrogen sinks but medium chain length oils appear to act directly on methanogens and reduce the numbers of ciliate protozoa. However, Kongmun et al. (2010) reported that supplementation of coconut with garlic powder improved in vitro ruminal fluid fermentation in terms of the VFA profile, reduced methane losses and reduced protozoal population. While this is encouraging, many factors need to be considered such as the type of oil, the form of the oil (whole crushed oilseeds vs. pure oils), handling issues (e.g. coconut oil has a melting point of 25°C) and the cost of oils which has increased dramatically in recent years due to the

increased demand for food and industrial use. Few reports cover the effect of oil supplementation on methane emissions from dairy cows, where its impact on milk fatty acid composition and overall milk fat content would need to be carefully studied. Recent strategies, based on processed linseed, turned out to be very promising in both respects. Most importantly, a comprehensive whole system analysis needs to be carried out to assess the overall impact on global GHG emissions (Wanapat et al., 2013).

Manh et al. (2012) reported that supplementation with Eucalyptus leaf meal at 100 g/d for ruminants could be an alternative feed enhancer: it reduces the production of rumen methane gas in cattle, while the digestibility of nutrients was unchanged. Conversely, Pilajun and Wanapat (2010) reported that increasing the coconut oil and Mago-pel (Mangosteen Peel Pellets) levels decreased proportion of methane production, and that a suitable level should not exceed 6% for coconut oil and 4% DM for Mago-pel supplementation. In the future, comprehensive research into the individual components of essential oils, the physiological status of animals, the nutrient composition of diets and their effects on the rumen microbial ecosystem and metabolism of essential oils will be required to obtain consistent beneficial effects. Moreover, previous work, based on using plant secondary compounds and oils in both in vitro and in vivo trials, concerning rumen microorganisms, methane production and their impact on the mitigation of methane in the rumen, shows great potential for improving rumen ecology in the study of ruminant productivity (Wanapat et al., 2013).

5.8Genetic selection

Recently, it has been studied that CH4 productionfrom different animals under same feeding conditionsshows significant variation among animals (Patra, 2011).In trials with grazing sheep, Pinares-Patino et al.(2003) identified some animals as high and lowCH4

emitters on the basis of CH4 output per unitof feed intake and noted that these differencespersisted all the four measurement periods of5 months when the same type of diet was fed.Although the reason is not clear, it might be dueto variations of methanogen numbers among animals(Zhou et al., 2009). This finding suggests thepossibility of genetic differences between animalsin CH4 production, which could be utilized forgenetic selection for low CH4 production.Recent research has demonstrated that ruminantswith low residual feed intake (RFI; i.e.,the difference between actual feed intake and theexpected feed requirements for maintenance andproduction) emit less CH4 than the animals withhigh RFI (Hegarty et al., 2007).This may offer an opportunity for genetic selectionfor this trait and it can be selected without compromising the production traits. For instance,Hegarty et al. (2007) reported that CH4 emissionwas lower in Angus steers selected based on lowRFI than in steers having high RFI (142 vs. 192 gCH4per day or 132 vs. 173 g CH4per kg daily gain)and daily gain was similar in both groups. Thelow CH4 emissions by cattle with low RFI mightbe due to lower methanogen numbers in low RFIcattle than in high RFI cattle (Zhou et al., 2009). Ithas also been suggested that the greater suppressionof CH4 could be achieved on low digestibilitydiets, when animals are selected based on low RFI(Hegarty et al., 2007). Thus, this strategy couldbe more advantageous for the tropical countrieswhere low-quality feeds are fed to ruminants.

6. Conclusions

Livestock production is essential for food security and for bringing millions of people out of poverty and starvation to build and maintain a stable society. The world is facing major challenges, from feeding the growing population to tackling severe environmental crises including natural resource degradation and catastrophic climate change. The management strategies to mitigate methane emissions from ruminant not only will enhance utilization of

522 dietary, improve feed efficiency and animal productivity, but also a decrease in methane

523 emissions will reduce the contribution of ruminant livestock to the global methane inventory.

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Table 1. Protein consumption demand per capita of livestock products1

Meat, kg/yr Milk, kg/yr

Region 1964 - 1997 - 2030 1964 - 1997 - 2030

1966 1999 1966 1999

World 24.2 36.4 45.3 73.9 78.1 89.5

Developing countries 10.2 25.5 36.7 28.0 44.6 65.8

Near East and North Africa 11.9 21.2 35.0 68.6 72.3 89.9

Sub-Saharan Africa2 9.9 9.4 13.4 28.5 29.1 33.8

Latin America and the 31.7 53.8 76.6 80.1 110.2 139.8


East Asia 8.7 37.7 58.5 3.6 10.0 17.8

South Asia 3.9 5.3 11.7 37.0 67.5 106.9

Industrialized countries 61.5 88.2 100.1 185.5 212.2 221.0

Transition countries 42.5 46.2 60.7 156.6 159.1 178.7

1 Source: WHO (2013).

Excludes South Africa.

Table 2.Methane abatement strategies, mechanism of abatement, considerations for use and reducing efficiency of CH4.

CH4 abatement strategies Mechanism of abatement Considerations for use

Reducing efficiency of CH4

• Feed management -Roughage: Concentrate ratio, Increased hemicellulose/starch, Reducing cell wall

• Plant Compounds -Condensed tannins, Saponins, Essential oils, Organosulfur compound

• Organic Acids -Fumarate, Malate, Nitroethane, Nitrate, Thiamine,


• Ionophore -Monensin or Rumensin

• Immunisation and biological control

- Methanogen vaccine, Methanotrophs, Probiotic, Bacteriophages, Bacteriocins

• Defaunation -Chemical, Feed additives

• Lipids

-Fatty acids, Oils, Seed oils, Taloow

Indreased rate of passed; increased C3:C2 ratio, reduced rumen pH

Antimicrobial activity; reduced H availability

H sink, greater proportion propionate versus acetate -Thiamine: inhibitspyruvate oxidative decarboxylation - Bromochloromethane inhibitscobamide-dependent methyl inCH4 production. Inhibits protozoa and grampositive bacteria; lack of substrate for methanogenesis Host immune response to methanogens

Removes associated methanogens; less H for methanogenesis

Inhibition of methanogens and protozoa; greater proportion propionate versus acetate; biohydrogenation

Shift methanogensis to 7 to 90% hind gut or manure, risk of subacute ruminal acidosis

Optimum dosage 10 to 96%

unknown; more in vivo

research needed; long-

term studies needed; may

affect digestibility;

residues unknown

Varies with diet; more in 3 to 75% vivo research needed; long-term studies needed; may affect digestibility

Adaptation of microbiota 4 to 76% may occur; varies with diet and animal; banned in the EU

Vaccine targets; diet and 7 to 50% host geographicallocation differences

Adaptation of microbiota may occur; varies with diet; maintenance of defaunated animals Effect on palatability, intake, performance, and milk components; varies with diet and ruminant species; long-term studies needed

20 to 60%

10 to 90%

• Genetic selection Genetic selection of animals Varies with diet and

for decreasing methane ruminant species; longemissions term studies needed

Source: Compiled by Cherdthong (2012)