Luận văn sử DỤNG cây KHOAI mì (sắn) để PHÁT TRIỂN CHĂN NUÔI dê ở AN GIANG, VIỆT NAM

HUE UNIVERSITY HUE UNIVERSITY OF AGRICULTURE AND FORESTRYLE THI THUY HANG UTILIZATION OF CASSAVA FORAGES FOR GOAT PRODUCTION IN AN GIANG PROVINCE, VIETNAM DOCTOR OF PHILOSOPHY IN ANIMAL

HUE UNIVERSITY HUE UNIVERSITY OF AGRICULTURE AND FORESTRY

LE THI THUY HANG

UTILIZATION OF CASSAVA FORAGES FOR GOAT PRODUCTION IN AN GIANG PROVINCE, VIETNAM

DOCTOR OF PHILOSOPHY IN ANIMAL SCIENCES

HUE, 2020

HUE UNIVERSITY HUE UNIVERSITY OF AGRICULTURE AND FORESTRY

LE THI THUY HANG

UTILIZATION OF CASSAVA FORAGES FOR GOAT PRODUCTION IN AN GIANG PROVINCE, VIETNAM

SPECIALIZATION: ANIMAL SCIENCES

CODE: 9620105 DOCTOR OF PHILOSOPHY IN ANIMAL SCIENCES

SUPERVISOR 1: Assoc Prof Nguyen Xuan Ba

SUPERVISOR 2: Dr Dinh Van Dung

HUE, 2020

I hereby guarantee that scientific work in this thesis is mine All resultsdescribed in this thesis are righteous and objective They have been published inJournal of Livestock Research for Rural Development (LRRD)

http://www.lrrd.org

Hue University, 2020

Le Thi Thuy Hang, PhD Student

To my parents who taught me the good things in my life, my loving husbandand my sons

These studies were carried out at An Giang University, Hue University ofAgricultural and Forestry, Hue University with financial support from the MekongBasin Animal Research Network (MEKARN II) Project I am grateful for their supportfor the thesis research and the scholarship for the PhD study

I would like to express my sincere thanks to:

Associate Professor Nguyen Xuan Ba, my main supervisor, for all his ideas,knowledge and experience Thanks for unceasing support in research and socialactivities He has given me invaluable support, encouragement and guidancethroughout my study His reading, editing and follow -up of this thesis are gratefullyacknowledged

Dr Dinh Van Dung, my second supervisor, who has given me invaluablesupport, encouragement, criticism, excellent skilled technical assistance and guidancethroughout my study

Professor Thomas R Preston, who has given me invaluable support, for valuableadvice, encouragement, enthusiasm and discussions throughout the study His readingand correcting and follow-up of this thesis from the beginning to the end have enabled

me to accomplish this work successfully, especially in correction of my English

Associate Professor Le Van An, Rector of Hue University of Agriculture andForestry for giving us the best conditions, encouragement and support during ourstudies in Hue

Dr Khieu - Borin, Regional Coordinator of Mekarn II Project “Vietnam –SAREC Sustainable Livestock Production Systems” project, for valuable advice anddiscussions

Associate Professor Duong Nguyen Khang, Consultant of the “Vietnam –SAREC Sustainable Livestock Production Systems”, for valuable advice

Professors, Lectures and assistant lecturers in courses which I have attendedduring my studies for sharing their valuable knowledge

Associate Prof Dr Vo Van Thang, Rector of An Giang University for giving mepermission to study, facilitation and encouragement

My Dean, Dr Ho Thanh Binh, Dean of Agriculture and Natural ResourcesFaculty of An Giang university for giving me permission to study, facilitation andencouragement.

My colleagues at the Department of Animal Husbandry and VeterinaryMedicine of Agriculture and Natural Resources Faculty of An Giang University forperforming the chemical analyses and sharing experiences in scientific research andsocial activities

My students, for help me in taking care the experiments

To my friends in the PhD Course, from Lao, Cambodia and Vietnam for giving

me a warm and friendly atmosphere

To my big family, for all their support and encouragement throughout my study.And special thanks to my husband Tran Xuan Hien, two children’s who understood mywork, and shared the happiness and sadness with me, for his loving, unceasing supportand patience for my whole- life study

The aims of the study were to improve utilization cassava forage for increasingperformance and reducing enteric methane emission in goat fed cassava foragerestricted level of brewery grain and biochar in An Giang province, Vietnam Therewere one survey and four experiments in this study

The survey of cassava and goat systems in Tinh Bien and Tri Ton districts, AnGiang province showed that there is an increasing tendency to plant cassava At thesame time there are major trends in the population of goats increasing However, goatproduction systems were still extensive, exploiting natural feed resources with smallherds of indigenous goats, which have small sizes and low growth rates Feed andfeeding for goats were mainly natural grass and by-products, from crop growing, lownutrition It is not enough feed in rainy and flooding season Whole, cassava forageaveraginge 5 tons/ha was available, but the farmers did not use them as feed for goats

The impact of different levels of urea added to cassava stems (CS) and itschemical properties was investigated (Experiment 1) The urea treated cassava stems(UCS) (3% in DM) made good quality ensilage, with no loss in nutritive value thatcould be stored up to 8 weeks An additional benefit was that the urea treatmentreduced the content of HCN in the ensiled stems

Base on these results of the experiment 1, experiment determined the effect onfeed intake, digestibility and N- retention in goats of supplementing the urea treatedcassava stems (UCS) with fresh water spinach and biochar (Experiment 2) DMintake was increased 18% by supplementing the UCS with biochar; and by 24% byaddition of water spinach The combined effect of biochar plus water spinach was toincrease DM intake by 41% Biochar increased daily N retention by 46% and thebiological value of the absorbed N by 12% It is thought that this major benefit frombiochar arises from the role it plays as physical support for biofilms acting as habitatfor diverse microbial communities working for the benefit of the host animal and thusacting as a form of prebiotic

Experiment 3 describes the addition of increasing levels of brewers’ grains (0 to6%) in a diet of ad libitum sweet cassava forage for growing goats The 4% level of

brewers’ grains increased the DM intake, the apparent DM digestibility, the N retentionand the biological value of the absorbed nitrogenous compounds The methane levels ineructed gas increased with a curvilinear trend as the proportion of brewers’ grains in thediet was increased

The benefits of biochar were tested further in experiment 4 Twelve growingmale goats of the Bach Thao breed, were given a basal diet of ad libitum fresh cassavaforage supplemented with 4% (DM basis) of brewers’ grain The biochar was suppliedover the range of 0 to 1.5% in diet DM Responses in feed intake, live weight gain andfeed conversion to biochar followed curvilinear trends with optimum benefits whenbiochar was added at 0.86% of the diet DM By contrast, the eructed methaneproduction was decreased linearly with level of biochar

Key word: Cassava stems, cassava forage, brewers’ grain, liveweight gain,

biochar, methane emission

TABLE OF CONTENTS

LIST OF FIGURES

LIST OF TABLES

LIST OF ABBREVIATIONS, SYMBOLS AND EQUIVALENTS

EPS Self-produced polymeric substance

SCFA Short -chain fatty acid

VFA Volatile fatty acid

INTRODUCTION

1 PROBLEM STATEMENT

An Giang province in the South of Vietnam, is a watershed province in theMekong Delta, and one of the largest cultivated areas in the Mekong Delta The totalarea of agricultural land is more than 282,676 ha, of which paddy land accounts for85.2% (Statistic yearbook of An Giang, 2018) An Giang is one of the two provinces inthe Mekong Delta with hills and mountains, mostly in the northwest of the province, inTinh Bien and Tri Ton districts This is the last mountain cluster of the Annamites, sothe geological features also have similarities with the Southern Truong Son An Gianghas a tropical monsoon climate, with two distinct seasons: rainy season and dry season.The temperature ranges from 200C to 360C and rainfall from 1400 to 1600 mm Therainy season is the least in February and the highest in September The averagehumidity is 75-80% (An Giang hydrometeorological Station, 2017) Due to thetopography, the land resources are divided into different types: alluvial soil, alkalinesoil, mountainous land Total area of hilly land in An Giang is about 29,320 ha,accounting for 8.6% of total land area of the province Agricultural cultivation in thismountainous area is not favorable because of its low productivity, lack of water forirrigation in the dry season, but when the rainy season comes, some districts areaffected by floods eg: the flooding in 2018 affected hundreds of hectares of rice andcrops in the Mekong Delta As Naqvi and Sejian (2011) showed droughts, flooding anddepletion of natural resources, were caused by global climate change Therefore, goat isone of animal species, selected to keep with its advantagous characteristics of lowwater consumption, drought resistance and browsing behaviors adapting to feeds fromplants adapting to the sea water Besides, goat production in An Giang has developed inrecent years The number of goats were 13,950 head in 2017 (Statistic yearbook of AnGiang, 2018) Nguyen Binh Truong (2016) showed that in An Giang province, goatswere raised mainly in small scale and intensive systems for meat production; breeding;and meat Normally, feed for goats is from natural resources and by-products of theseason such as sweet potato, banana leaf, water spinach, lipstick around the house,settling idle work, bringing economic efficiency to farmers Some separate supplementfeeds are used such as coconut cake, soybean extraction meal, brewery waste, soyawaste, rice bran, etc., and concentrate is also supplemented with protein and energy

sources in diets (Nguyen Van Thu, 2016) The goat raisers in this area are spontaneous,under-invested, using local breeds, natural grass, not enough nutritional value for goat,

so the meat quality is not high But cassava is a potential, and plentiful, source of foodfor ruminants but the farmers in An Giang do not use it

Based on the above problems and threats, we hypothesize that utilization ofcassava forage for improving goat production and reducing enteric methane emissionfrom goat production in An Giang province, Vietnam This study was designed to testthe hypothesis by addressing the following specific aims were to improve nutritivevalue of cassava stems and stored by urea treatment In addition, using brewers’ grainand biochar supplied to improve growth rate and reduce methane emissions in a basaldiet of cassava forage fed to growing goats

2 AIMS AND OBJECTIVES OF THE STUDY

2.1 THE AIMS OF THE STUDY

The overall aim of this thesis was to improve utilization of cassava forage forincreasing performance and reducing enteric methane emission from goat production in

An Giang province, Vietnam

2.2 OBJECTIVES OF THE STUDY

The present study objectives were:

- To evaluate the potential productivity and nutritive value of cassava stems, andcassava forage for goats in An Giang Province

- To determine level of urea addition to cassava stems for storage to improvenutritive value, especially its digestibility

- To examine the effect of biochar supplementation on feed intake, digestibility,

N retention in goats fed urea treated cassava stems

- To determine levels of brewery grain that affect feed intake, digestibility andgrowth in goats fed sweet cassava foliage as basal diet

- To determine levels of biochar that would reduce methane production in goatsfed a basal diet of fresh cassava foliage and brewery grain

3 RESEARCH HYPOTHESES

The hypotheses tested were that:

- Cassava forage will have potential as a by-product for developing goat

- Using urea to treat cassava stems will improve nutritive value and storge longtime for feeding yearround.

- Supplementation with both water spinach and biochar will improve feed intake

and its digestibility in goats fed a basal diet of urea treated cassava stems

- Adding up to 6% of brewery grain will improve feed intake, digestibily, growthand reducing toxicity of the HCN in goat fed a basal diet of fresh cassava forage

- Adding biochar will reduce methane emissions and increase liveweight in goatfed a basal diet of fresh cassava forage and brewery grain (the best level of brewerygrain in previous experiment)

4 SIGNIFICANCE/INNOVATION OF THE DISSERTATION

4.1 SCIENTIFIC SIGNIFICANCE

The thesis contributes to the science of:

- Using urea to treat cassava stems is one of method to increase nutritive value,reduce HCN content and can be storeed at least 8 weeks

- Adding 4% brewery grain and 0.86% biochar (DM based) in Bach Thaogoat’s diet, that is basal of fresh cassava foliage has improved growth and reducedenteric methane emission from goat production

CHAPTER 1 OVERVIEW OF RESEARCH ISSUES

1 GOAT PRODUCTION SYSTEMS IN AN GIANG

1.1 GEOGRAPHICAL LOCATION AND CLIMATE IN AN GIANG

An Giang is a watershed province in the Mekong Delta, with an area of 3,536.8

km2, part of the Long Xuyen Quadrangle which is one of the largest cultivated areas inthe Mekong Delta The province is bordered by Cambodia to the northwest (104 km),

to the south-west by Kien Giang province (69,789 km), to the southeast by Can Thocity (44,734 km), to the east by Dong Thap province (107,628 km) An Giang in thegeographical latitude of about 10 to 110 North latitudes, ie, close to the equator, sotemperature and precipitation are similar to the equatorial climate There are twoseasons in An Giang province: dry season (from December April), and rainy season(from May to November), in this time there is flooding season (from August toNovember) Normally, when flooding comes, the field area is immersed by flooding, it

is difficult finding feed and there was not enough feed for ruminants or goat production

in this area

1.2 GOAT RAISING SYSTEMS IN AN GIANG

1.2.1 Goat population and management

Figure 1.1 Number of goats in An Giang from 2012 -2017

Source: Statistic yearbook of An Giang, 2018

In recent years goat production in Vietnam has been developed very fast around30.0% annually with the total population of 2,556,300 heads in 2017, due to highdemand of goat meat for consumption Some projects of goat production funded byOxfam UK, associated with Mekong delta provinces, which show the effectiveproduction contributing to the poor alleviation and prosperous income In An Giang,goat production in 2017 was 13,950 heads, that is 6 times higher than the number ofgoats in 2012, which shows that the trend of goat production in An Giang graduallydevelops, the farmers are interested in and develop goat husbandry In recent years,consumers have been more interested in nutritious food sources from goat meat, goatmeat market has increased, and the goat meat prices have also increased, but goatfarming is low investment, easy to manage, less risky, more diversified feed than otherruminants like cattle Therefore, raising goats will help farmers to earn higher profits

- Distribution of goat by district in 2017

Figure 1.2 Distribution of goat by district in An Giang, 2017

Source: Statistic yearbook of An Giang, 2018

Figure 1.2 shows the number of goats distributed across three geographic areas

in An Giang province Goats are most concentrated in Tinh Bien, Tri Ton, the island ofPhu Tan and Tan Chau in 2017 The number goats increased because the price of goatmeat has been high in recent years: Price of goat meat (3.2 USD/kg LW) compared tobeef cattle (2.5 USD/kg LW) (Do Thi Thanh Van et al., 2018) It is one of the reasonsand potential to develop goat production in An Giang province and Vietnam also Butgoat production will be suitanable development, if it uses and improves by- products asgoat feed in this area efficiency

- Goat raising purpose and farm scale

In An Giang, goat raising began to develop in recent years (figure 1) Thenumber of goats is 13,950 heads in 2017 (Statistic yearbook of An Giang, 2018).Nguyen Binh Truong (2016) showed that in An Giang province, goats were raised bysmall scale and with three main purposes: selling meat product; breeding; breeding andmeat Goat farming for breeding and meat accounted for the highest proportion of74.4% of goats, followed by raising 18.9% with selling meat product and 6.67% forselling breeding respectively Normally, farmers usually choose the best goats based on:

good shape, healthy appearance from good mother to raise or sell the breed with femaleand sell meat with male goat after 7-8 months old On the other hand, goats wereraised by farmers spontaneously, the farmers learn how to breed each other, so that thenumber of goats per farms average 6-10 heads accounted for 28.9% (26/90 surveyedhouseholds) A few households raise from 1 to 5 heads per household (12/90 surveyedhouseholds), number of goats from 11- 15 heads/farm was 26.7% (24/90 surveyedhouseholds, from 16-20 heads/farm with 14.4% (15/90 surveyed households) and thenumber of households raising more than 20 heads accounts for 16.7% (15/90 farms)(Nguyen Binh Truong, 2016) According to the author, this result had called that goatproduction is growing steadily

- Goat management

Normally each household has a small cage for captive goats, with small area.The cages are made near the house, surrounded by trees Goat housing did not investtoo much money compared with raising pigs or cattle, goat farmers choose the treesplanted around the house to make 4-5cm square floor and wall paneling Goat's cagesare made of simple materials such as bamboo, acassia aneura, coconut tree, etc Theroofs are usually covered with leaves or tole Therefore, 100% of the farmers make goatcages, sheet metal roofs, convenient cleaning of effluent and leftovers of goats Goat iseasy raising, less take care They were raised by genetic traditional, therefore thefarmers did not use vaccine for goats

With the advantages of low capital, easy to buy, to sell, goat raising is graduallybecoming a landlord for the poor farmers, who have limited land area or less productiveland In the context of rising food prices, the output of some livestock is limited Thegoat raising is attracting many families to participate by utilizing agriculturalbyproducts profitably In Vietnam the domestic markets of goat products are good.Although the marketing of goat products, and meat are limited, the local markets forthem are very good for the producers There is a high demand for goat meat in manydifferent areas of Vietnam from the North to the South and the rate of increase in thenumber of goats annually is not sufficient to meet the demand Therefore, many farmersand companies are preparing to build large commercial farms with the importation ofdairy goat breeds from developed countries for both milk and meat (Do Thi Thanh Van

1.2.2 Feed and feeding management for goat

Feed is one of the determining factors of goat efficiency Feed for goats is asdiverse as agricultural byproducts, leaves around the house such as banana leaves,jackfruit, legumes, etc Nguyen Binh Truong (2016) review said that, almost all goats in

An Giang province were fed natural grass with 33.31%, some large-scale farms (>=20heads/farm) had grown elephant grass, VA06 grass, and Panicum mai-mum Goatfeed is very diversified, abundant, they can utilize the variety of feed around the house.Nguyen Huu Van (2012a) showed that banana stems and leaves are a source of goodfeed for goats When feeding goats banana leaves 100% in diet, DM consumption about2.62% of body weight (DM basic) with digestibility of DM and CP were 62.0% and59.1% At that time goats ate 100% banana stems, DM consumption was 1.25% ofbody weight (Nguyen Huu Van, 2012b) According to the author, the use of bananaleaves in combination with other foods as a source of food for goats would be better

Many researchers reported that, leaves of trees which can grow around house

are good feed for goats Both Paper Mulberry and Muntingia were feed source for goats Silivong et al (2012) showed that the foliage of Paper Mulberry and Muntingia represented 60-70% of the total DM intake, total DM intake of Paper Mulberry and

Muntingia were 31.3 g/kg LW and 30.8 g/kgLW, and coefficients of apparent

digestibility of OM and crude protein of goats fed Paper mulberry and Muntingia werehigh but were not affected by NPN source Even wild trees were a feed source forgoats, for example growth rates of goats on a sole diet of Mimosa foliage were 81 g/day

in confinement and 98 g/day under free grazing (Thu Hong et al., 2008)

Cassava leaves and cassava foliage were also excellent protein supplementsources in the rations of ruminants So many researches about ration of cassava leaves

or cassava foliage will be supplement for goat, increasing DM intake, digestibly ofcrude protein and organic matter There were many results: There was a 21% increase

in N retention when cassava was the main foliage (Phonethep et al., 2016) The use ofcassava peels, leaves improved the performance of goat (Onwuka, 2015).Supplementing fresh, wilted or sun-dried foliage from cassava in the diet did not result

in any significant differences with respect to DM intake in percent of BW (3.4 to 3.6%)and LWG of the lambs was ranged from 73 to 77g/day (Hue et al., 2010) The mainproblems of fresh cassava leaves are high HCN contents (333 mg/ kg DM) The HCN

content in fresh cassava foliage reported by different researchers According to Khangand Wiktorsson (2006), Promkot et al (2007) and Phengvichith and Ledin (2007), theHCN content in fresh cassava foliage was 983, 1179 and 325 mg/kg, respectively, whileonly 225 mg/kg was recorded in the experiment of Thang et al (2010) Therefore, whenusing fresh cassava foliage or cassava leaves as goat feed, they should be reduced HCNcontent by processing This is also a worry of the farmers in An Giang, because theydid not know to use cassava as feed for ruminants, they are afraid of ruminantspoisoning Therefore, cassava in An Giang is wasted or burned in the field, pollutingthe water and environmental pollution An Giang is province in Mekong delta, so it isaffected by flooding every year There is flooding from August to November, and thiscause a lack of natural grass, and agricultural by product for goat

Figure 1.3 Farmers buy grass from another region

At that time, the farmers have to buy grass or agricultural by product for goatfrom another region According to Nguyen Thanh Binh (2018), agricultural byproductsabounded in the Mekong Delta (including An Giang), but they were used for cattle, andbuffaloes while goats are modest and mainly in fresh form, not processed to form asource of feed reserves with higher nutritive value If the farmers implementprocessing, then storage methods will contribute to solve the shortage of raw feed forruminants in the rainy and flooding season

Goats are small ruminants usually raised in An Giang in three ways: intensive,semi-intensive (semi-free), and extensive systems (grazing) In the intensive systems,goats are kept in confinement and the feed is supplied entirely from outside This system

is suitable where planted grasses and other supplements are available with 66.7% (60/90surveyed households) In the semi-intensive systems, goats are grazed from 4-8

32.2% (29/90) of surveyed households This system is found suitable to the existing goatfarms in Vietnam In the extensive systems, goats are grazed on available pasture withoutsupplementation This system is common in mountainous and forest areas for the meatgoats, but low productivity, capital investment in breeding, breeding facilities, feed,veterinary medicine, and public care It is difficult to manage breeding and inseminationamong the animals in the herd, environmental pollution caused by faeces, or not fullyutilized with 1.11% (1/90 surveyed households) in An Giang (Nguyen Binh Truong,2016) Because goats are active, agile, have an unusual temperament and are hyperactive.Goats are browsers and so are always looking for new food They move very fast wheneating around the tree and eat only the most delicious food, then quickly move to the nexttree and dust They like to eat at a height of 0.2-1.2m, they can stand on two feet to eatthe leaves, and even climb the tree to choose the delicious parts of the tree for eating, this

is problem when grazing in the limited grazing area

1.3 OPPORTUNITIES AND CHALLENGE FOR GOAT PRODUCTION

Decision No 929 / QD-UBND, 2015 and 2605/QĐ-UBND 2016 reported that

An Giang is a main source of agricultural products Livestock development is one ofthe development strategies of the province and should be considered by theGovernment and investors Since 2015, An Giang People's Committee has manypolicies and strategies to support farmers development of livestock such as policies tosupport agricultural restructuring (including livestock); support for breeding animals,training for technical breeding, and improving nutritive value feed resources

Construction of feed raw material areas: Strive to create quality feed equivalent

to the area planted with grass of about 900 ha by 2020 in Tri Ton and Tinh Bien Focus

on developing livestock production systems

To develop the technology of processing agricultural by-products (total mixratio) with available local resources (broken rice, bran, corn etc)

To gradually shift small-scale farming to more intensive farms and from smalland medium enterprises in livestock Strive to reach the total number of ruminants up to200,000 heads by 2020, corresponding to the average growth rate of 10% per year forthe period 2015-2020

To build and reorganize animal slaughtering systems in industrial districts inassociation with animal husbandry areas, veterinary hygiene, food safety and

environmental treatment Simultaneously build modern slaughter facilities associatedwith export processing.

Research to create value-added products from the livestock industry similar tocattle skin used in the footwear industry, livestock waste, faeces used to fertilize plants,

or for growing earthworm to improve nutrition of soils

Building the brand of animal products in the province (beef, goat meat): toorganize and manage the livestock sector more effectively, create higher value livestockand help diversification and promotion of trade in livestock products better

Recently, farmers and the local and central government of Vietnam have paidmore attention to enhancing goat production such as producing the developmentpolicies, standards of goat farms, technical trainings and incentives for establishment ofgoat production cooperatives, larger intensive farms and extensive clubs, improvedmarkets There have also been collaborations among the universities, companies andlocal institutions to create chances of investments on technology, finance and humanresources for improving production and markets The veterinary networks, vaccines ofcommon diseases, parasite preventions and effective medicines are available to protectthe goat herds from diseases However, goats also produce CH4 and CO2 during theirlife time, which contribute to climate change Therefore, strategies for reducing greenhouse gas emission of goats by feeding, nutrition balance, supplementations, andbreeding, should be applied (Nguyen Van Thu and Nguyen Thi Kim Dong, 2015) forimproving the livelihoods of the poor producers along the sea shore, where the effects

of climate change are greatest

2 THE DIGESTIVE SYSTEMS AND ENTERIC METHANE EMISSION

IN RUMINANTS

The digestive tract is not only important for nutrient digestion and absorption, but

it is the largest immunological organ in the body protecting against exogenous pathogens

2.1 RUMEN FERMENTATION AND METHANE PRODUCTION

2.1.1 Rumen fermentation

Anaerobic microbes in the rumen of the ruminant are able to degrade thecomplex fiber source to provide essential nutrients that are readily digested by the hostwhile this is completely restricted in non- ruminants (Owen and Basalan, 2016) In term

of biochemical metabolism, ruminant microbes secrete the enzyme that hydrolyses all

that are then fermented to the intermediate substrate (VFA, ammonia, ATP) The main

purpose of rumen fermentation is to generate energy for maintenance and synthesis

processes of microbial polymers which leads to the synthesis of more microbial cells

which in turn increases available protein to the animal (Phuong, 2012)

Figure 1.4 Microbes needed for fermentation (Leek, 1993)

Acetate Butyrate

TCA Cycle

2CO2 Succinyl-CoA

Propionyl-CoA Propionate

2.1.2 Volatile fatty acids pattern

Volatile fatty acids (VFA) are important products of rumen fermentation TheVFA are not only the major source of energy to the ruminant animals but also influencemethane production in the rumen The concentration of volatile fatty acid (VFA),mainly acetate, but some propionate and butyrate and largely part was absorbed viarumen wall as free form When rumen microbes ferment soluble sugar, they produceVFA and ATP that are considered energy sources and are re-utilized for maintenanceand growth of microbes Acetate may enter mainly fatty synthesis via actyl-CoAintermediate than ketone bodies because it must not pass through this stage ofmetabolism, while partly buturate is converted to ketone bodies (acetoacetate, β-hydroxybutyrate) in the liver, the excessive accumulation of ketone bodies results inketosis as a pathological condition of the ruminant Propionic acid is reported to beconcerned as a precusor of glucose synthesis with 80% propionate blood transfered tohepatic for gluconeogenesis by Van Soest (1982), Preston and Leng (1987) all of whomreported that propionate may contribute 80-90% of the glucose synthesized in sheep onroughage diets (Cridland, 1984) High roughage rations will contain a higher percentage

of acetic acid whereas high concentrate rations will result in slightly higher levels ofpropionic acid With by-product diet or dry pasture, poorly absorbed glucose thusgluconeogenesis play the major role to provide glucose needed for ruminant, while somestarch escape fermentation in grain-based diets can be digested in the small intestine

2.1.3 Protein metabolism

The rumen microbes are likely to utilize non-protein nitrogen source (NPN)such as urea to contribute to the ammonia pool in the rumen Level of ammonium inrumen caused by microbial output is likely to convert ammonia to protein for synthesis

to microbial polymer If there is low ammona then there will be nitrogen shortage tomicrobes leading to low fermentation rate In contrast, excessive ammonia results inammonia toxicity for the animal Therefore, to utilize effectively, the conversion ofammonia to microbial protein requires the availability of ATP energy generated by thefermentation of carbohydrates In other words, it requires the balance betweencarbohydrate and NPN in the diet Arccording to Wattiaux (1991), approximately 60%

of the amino acids absorbed through the small intestine is from a bacterial protein, andthe remaining 40% is from ruminally un-degraded dietary protein In addition, therumen can use effective sources of protein from by-product sources

The term of by-pass protein in rumen fermentation is defined to be protein thatescapes the degradation of rumen microbes Two important factors influencing theamount of protein bypassing degradation in the rumen are the length of time spent in therumen and fermentation of the protein (Miller, 2012) Leng et al (1981) indicated thatby-pass protein in the ruminant diet was postulated on stimulating feed intake,influencing the efficiency of microbial cell yield and digestion in small intestine,providing essential amino acids post ruminally which are used efficiently, and in additionincreasing the total energy intake If protein is too soluble and the sole diet in rumen,dietary protein can be lost due to a large part of essential amino acid is fermented bymicrobes, and microbial protein would escape the rumen to lower digestion tocompensate protein needed of the animal, meanwhile, the by-pass protein can provideessential amino acids that are not synthesized by animal tissues, via absorption fromdigested feed

It can be seen that un-degradable and degradable protein play an important role

in rumen function and animal efficiency Although it has not been well defined thedesirable proportion of undegradable and dregradable protein in ruminant feeding, but

it is quite evident that the diet has to contain sufficient protein to productivity (Miller,2012) There are many studies that discuss the most effective ratio of rumen degradableprotein and un-degradable protein (RDP: RUP) Wang et al (2008) and Tacoma et al

(2017) did not found a significant difference among ratios of RDP: RUP on milk yield,milk composion, and dry matter intake, but reducing the ratio of RDP: RUP reduced Nexcretion in urine and faeces lead to enhance the efficiency of N utilization Savari et

al (2018) suggested that an RDP: RUP ratio of 65:35 could be adequate for cows inearly lactation with an average milk production of 44 kg and a DMI of 25kg

2.2 METHANE PRODUCTION

Methane gas is produced from fermentation by rumen microbes Domesticatedruminants represents a loss of 2–15% of the gross energy (GE) intake by methaneproduction (Holter and Young, 1992), therefore being one of most important factorscontributing to inefficiencies in ruminant production systems (Moss et al., 2000)

In the rumen, methanogens are a large and diverse group of Archaea By isolation

method, it is classified as Methanobrevibacter ruminantium, Methanobrevibacter smithii,

Methanobrecibacter millerae, Methanobrevibacter olleyae, Methanobacterium formicicum, Methanobacterium bryantii, Methanosarcina barkeri, Methanosarcina mazai and Methanomicrobium mobile (Qiao et al., 2014) Overall, the methanogens can

be divided into two groups: H2/CO2 and acetate-consumers with different levels ofenergy yielding (-130.7 kJ/mol substrate and -32.3 kJ/mol substrate respectively) Thedistribution of methanogen is diverse, it is assumed that they are free-swimming influid or attach to digested solid or attach to protozoa (Morgavi et al., 2010)

In many tropical developing countries, goat production for milk and meat forhuman demands is a priority choice for adapting to climate change, and the abatement

of enteric greenhouse gases emissions should be considered However, goats beingsmall ruminants, which emit around 5.0kg CH4/head/year (Nguyen Van Thu, 2018),could create greenhouse gases that influence climate change Afshar et al (2015)concluded that it is notable that, other than management related strategies, threeimportant strategies including nutritional, biotechnological and microbiologicalstrategies are required for controlling and decreasing methane emission Carla et al.(2016) showed that the replacement of cereal grain with fibrous by-products did notincrease methane emissions (57.0 L/goat per day, on average)

2.2.1 Pathway of methane production

The pathway of methanogenesis has yet to be fully defined due to the diversemicrobes in the rumen create overall synergistic and antagonistic interactions

carbohydrate fermentation are concerned as terminal electron receptor for hydrogen toform methane (Diagram 1) Based on biochemistry pathway, it can be seen that hexosemetabolism via the Emden-Meyerhof-Parnas pathway (EMP) produces pyruvate as anintermediate associated with co-factor NADH generation (Leng, 2011) In the rumen,methane production from CO2 substrate as an electron acceptor is a predominantpathway of hydrogenotrophic methanogen This bacterium group also uses formate as

an important electron donor and it is estimated to produce up to 18% of the methaneproduced in the rumen Many of the syntrophs are able to produce both H2 and formate,and most of the methanogenic partners are able to oxidise both substrates to methane(Leng, 2014) Acetate as substrate produce methane through the aceticlastic pathway by

Methanosarcina group but in terms of energy order, the energy level of methane

production from acetate is very low, thus, Methanosarcina population is limited in the rumen (Morgavi et al., 2010) Furthermore, acetate is absorbed largely into the

bloodstream, thus, the hydrogen would be contributed mainly by CO2 tomethanogenesis (Galand et al., 2005)

Figure 1.6 The reaction of methane generation

The process of methane production is a requirement in low partial pressurehydrogen, which is necessary for the continuous fermentation in the rumen (Figure1.6) However, the inhibition of methanogenesis would redirect the available hydrogeninto alternative energy-yielding metabolic pathways which are expected to improve theproductivity of ruminant but not adversely affect ruminal metabolism Martinez-Fernandez et al (2016) had a comprehensive assessment on methanogenesis inhibition

by adding different levels of chloroform on steers fed roughage hay versus hay:concentrate, the result showed that increasing chloroform level would increase theexpeulsion of hydrogen but there was no effect on both dry matter intake and fiberdegradation The critical issue found in this study is that expelled H2 per mole ofdecreased methane was lower on steer fed roughage hay only diet compared with hayconcentrate The evaluation of rumen microbial response in this study showed thatdecreasing Archaea and Synergistetes for both diets accompanied with increasing

Bacteroidetes (the bacteria involved in propionate production) but did not changefibrolytic bacteria, fungi, and protozoa These results can conclude that hydrogen wasredirected into products other than into CH4 and H2, probably in microbial protein, it can

be expected to improve the performance of the animal Furthermore, using roughagehay in the diet is the suggestion in slowing fermentation that creates a condition formicrobes utilizing H2 more effectively as a reduction of methane production,meanwhile, highly concentrates fermentation in diet would high partial pressure of H2

2.2.2 Manipulation in mitigation of methane production

Nutritional mitigation of CH4 production is founded on 3 basic approaches:(1) VFA production patterns will be altered by feed ingredient

(2) Increased rate of passage, which can alter microbial populations and VFAproduction patterns and shift some digestion to the intestines;

(3) Choosing better quality diets to increase production will reduce the CH4 associatedwith maintenance energy requirements

Most microorganisms in the rumen and lower digestive tract use fermentation tofuel their cellular function and produce Short-Chain Fatty Acids (SCFAs) as abyproduct The SCFAs, namely acetate, propionate, and butyrate, are subsequentlyabsorbed through the rumen wall and metabolized by the host (Van Soest, 1994)

Now, many researchers have focused on factors (1) and (2) above, for reducing

CH4 emissions from ruminants Feed ingredients provide the substrates for microbialfermentation, and differences in feed digestibility and chemical composition alter theamount of energy extracted by the microbes and the patterns of VFA and CH4 produced.The proportions of VFA affect the amount of CH4 produced, because propionateformation consumes fewer equivalents, whereas acetate and butyrate formationgenerate H2 for methanogenesis (Hungate, 1966) In this case, we also focus to find thefeed ingredients that can provide the substrates for microbial fermentation such asbiofilm, and can control the proportion of VFA, reduce CH4 produced

Based on the mechanism of methane production, a series of studies inreplacement of urea by nitrate as electron acceptor to outcompete methanogen lead to

reduce methane production were conducted both in vivo and in vitro experiments (Trinh

Phuc Hao et al., 2009; Ngoc Huyen et al., 2010; Inthapanya et al., 2011; Binh Phuong

et al., 2011) In these studies, on ruminants, the animal was adapted to graduallyincrease nitrate salt in the diet without methemoglobin

De-fauna protozoa by oil is believed to affect the protozoa depletion populationwhere methanogen attachment Although the mechanism of action is poorlyunderstood, it may be related to the lipophilic nature of compounds such as anetholwhich facilitates permeation of essential oil across the protozoal membrane (Cardozo etal., 2004) Saponin and tannin have also been reported as removing protozoa The effect

of saponin seems to be mediated by their capacity to form irreversible complexes withcholesterol in the protozoal cell membrane to cause the destruction of the cellmembrane, cell lysis and death (Francis et al., 2002) In the case of tannins, reportedresults are somewhat confusing because some studies report unclear effects (Sliwinski

et al., 2002), while others report a clear defaunating effect (Bhatta et al., 2009;Monforte-Briceno et al., 2005) Bhatta et al., 2009 stated that the combination ofhydrolyzable and condensed tannins exhibits higher antiprotozoal activity thanhydrolyzable tannins alone Although the mode of action of tannins on protozoa is notclear, it might be like that observed on bacteria

Preston et al (2013) assumed that there is a correlation between lower solublecrude protein in fish meal with lower methane production when it is compared withgroundnut meal being higher solube CP and higher methane production This authorinterpreted that ammonia is likely to produce rapidly forms of highly soluble proteins

of diet, and soluble amino acids give rise to hydrogen sulphide, which is an effectiveelectron sink It is thus possible that there might be some negative feedback of thisrapid production of ammonia from dietary protein on the pathway of ammoniaformation from hydrogen

The recent studies have mainly been in vitro screening of good nutrients, agents

and feed sources to potentially reduce greenhouse gases such as essential oils, protein

sources, probiotics, TMR, silages, etc After that the in vivo studies could be tested and

then implemented for applications (Do Thi Thanh Van et al., 2018) The value of CH4production remarkably significantly decreased with increasing coconut oilsupplementation in the diets (Nguyen Thi Kim Dong & Nguyen Van Thu, 2018) Thisresult is consistent with the findings that CH4 production reduced in the dietsupplemented with 14% coconut oil versus without coconout oil supplement (12.6

versus 14.2 l/day) (Delgado et al., 2013) In an in vitro gas experiment adding

probiotics to the substrates Huynh Doan Nghich Luy (2016) found that there was asignificant reduction of CH4 and CO2 for the probiotic treatments Probiotics including

lactic acid and Bacillus bacteria, Saccharomyces yeast which are useful for the animals,

particularly improve the nutrient utilization, growth and milk production of ruminants

(Dunne et al., 1999) Recently, Riddell et al (2010) stated that probiotics reduce

methane production, depress the growth of pathenogenic bacteria by reducing rumen

pH and growth competition to methanenogenic bacteria

Biochar is known to increase the methane production in bio digesters butmitigates methane production in the rumen, improves the growth biochar is included at1% of DM basis in the diet of cattle (Leng et al., 2012a; Leng et al., 2012b) Leng et al.(2012a,b) showed that incorporation of biochar, prepared by carbonization of rice husks

in a gasifier stove reduced methane production both in vitro and in vivo (Leng 2012c).The action of biochar in the rumen resulted from it's potential to act as an improvedlocation for biofilm microbial consortia and that this would facilitate microbial activity,including oxidation of methane by methanotrophic organisms The idea that biocharcould act as a functional site for improved biofilm formation is based on the largesurface to weight ratio (>30m2/g and up to 500m2/g), creating opportunities foradsorption of both micro-organisms, nutrients and gases

Biocarbon pyrolyzed at high temperature in a manner that generates a very highsurface area is called engineered or activated biocarbon and has been theorized topromote the formation of microbial biofilms in the rumen (Leng et al., 2012a, 2014), aprocess essential for ruminal feed digestion (McAllister et al., 1994) Further, biocharmay lower the production of ruminal CH4 emissions both in vitro (Hansen et al., 2012; Leng et al., 2012a,b) and in vivo (Leng et al., 2012c) It has been suggested that

biochar reduces ruminal enteric CH4 emissions by altering rumen microbial biofilms,decreasing rumen methanogens and increasing rumen methanotrophs (Leng et al.,2012a,b,c; Toth and Dou, 2016)

3 POTENTIAL OF CASSAVA FORAGE FOR GOAT PRODUCTION

3.1 PLANT AREA AND DISTRIBUTION OF CASSAVA AND YIELD OF CASSAVA IN VIETNAM, AN GIANG

In Vietnam, cassava is a major source of income for farmers in areas of lowfertility soil and adverse climatic conditions It is also a source of raw materials forstarch processing and for the animal feed industry with high commercial value Cassavahas been planted throughout the 7 agro-ecological zones of the country: The Red RiverDelta, the Northern Midlands and Mountains, the North Central Coast, South CentralCoast, Central Highlands, South East and Mekong Delta However, the focus is mainly

in the Central Highlands (Figure 1.3)

According to the Ministry of Agriculture and Rural Development at the end ofNovember 2017, the area of cassava planting in the whole country was 1,400 hectares.Cassava has previously been cultivated mainly for the roots Small cassava stems can

be used for the next year’s growth Normally, cassava foliage was thrown away in thefield Based on the areas of cassava cultivation in 2017, the yield of cassava root was20.5 tonnes/ha (Statistic yearbook of An Giang, 2018), the amount of foliage available

at root harvesting is equivalent to about 30% of the root yield and was an estimated6.15 tonnes of dry matter per hectare (Erdmann et al., 1993) The amount of cassavafoliage produced was an estimated 8.6million tonnes per year in An Giang This was alarge amount of cassava foliage, but they were used only slightly at the harvesting time,but after 2 – 4 days harvesting, the leaves would fall down, and only stems remain.They were thrown away, although this resource is very good feed for ruminants

Figure 1.7 Plant area of cassava in Vietnam, 2017

Source: Ministry of Agriculture and Rural Development, 2017

About 70% of the cassava area of the country is grown using hybrid varieties;The remaining 30% is local varieties In the hybrid varieties, the KM94 variety isdominant (73%), the rest is other varieties (Nguyen Huu Hy et al., 2014) The popularcassava varieties were: Xanh Vĩnh Phú; Gòn; Nếp; Ba Trăng; Lá tre; Mì kè; HL23;KM94 KM140, KM98-5; KM95-3, KM98-1, KM 98-7 KM111-1; CM 101; SM937-26; KM419, NA1, KM21-12, 08SA06 There are two kinds of cassava: Sweet and bittercassava Sweet cassavas are used as food consumption for human; bitter cassavas areused for industrial processing such as wheat flours, animal feed, etc In An Giang therewere two kinds of cassava variety (Sweet cassava or Mi ke and bitter cassava)

Ubi et al (2008) found that the total HCN content of the roots was not correlatedwith the content in the leaves of the same plant Therefore, the classifications of “bitter”and “sweet” may not be applicable when regarding the whole plant So, based on thecontent of HCN in cassava roots, it is divided into two groups of cassava varieties: sweetcassava and bitter cassava Sweet cassava contains about 20 - 30mg kg-1 of fresh roots;bitter cassava contains 60 - 150 mg kg-1 of fresh roots (Mai Thach Hoanh, 2004) Thesweet cassava is local breeds, low yield, small roots, fresh and cassava roots are used forhuman food The bitter cassava is popular and grown with large area, high production.They are grown with large area in high land, and South-Central Coast Cassava roots areused to produce flour, processing starch, and industry products

"Sweet" or low- cyanogenic potential (CNP) cassava (root CNP less than 50 mg

kg-1 as HCN fresh weight basis) is generally considered safe for consumption with onlybasic processing (e.g., peeling and cooking), whereas "bitter" or high-CNP cassava(root CNP greater than 100 mg kg-1 as HCN fresh weight basis) must be processed prior

to consumption to eliminate the cyanogens or reduce them to physiologically tolerablelevels (Cooke 1983; Dufour 1988a) Other reports show cyanogenic glicosidesconcentration in the roots Sweet cassava has HCN concentrations below 100 mgHCN kg–1 and bitter cassava show concentrations above 100 mg kg–1 HCN (McKey

et al., 2010) Cassava plants are generally categorised as bitter or sweet, dependingupon their cyanide content The low HCN, or sweet cassava, has less than 50 ppm ofcyanogenic equivalents, while the high-HCN, or bitter cassava has more than 100ppm (Wilson and Dufour, 2002) The major difference between low- and high-CNPcultivars is limited to the CNP of the root parenchyma The CNP of the root periderm(peel, cortex) and aerial portions of the plant are high in both low- and high-CNPcassava (McMahon et al., 1995)

3.2 POTENTIAL OF CASSAVA FORAGE FOR GOAT PRODUCTION

3.2.1 Proportion yield of parts of cassava forage

The yield of cassava forage and differences in DM foliage yield could be due tothe differences in variety (Gomez and Valdivieso, 1984; Simwambana et al., 1992),fertilizer (Molina and ElSharkawy, 1995), age at first cutting and interval betweencuttings (Lockard et al., 1985; Simwambana et al., 1992; Tung et al., 2001; Hong et al.,2003) Although there is no data shown from the present study on the effects of seasons

on cassava forage yield, DM yield was reduced in all the treatments during the lastthree months of the experimental period, most likely due to the onset of dry season

3.2.2 Composition of cassava forage, parts of cassava forage

The chemical composition of cassava forage depends on many factors includingvariety, harvesting interval (Khang et al., 2005), difference fertility of soil, processing,and also climate, environmental conditions, such as drought (leading to an increase incyanogenic potential), geographic location age of the plant by Garcia and Dale (1999)and soil nutrient supply as reviewed in Burns et al (2013)

Table 1.1 The chemical composition of cassava forage variety

Cassava

Tannin (%)

HCN

Cassava Leaves - 18.6 - 20.7 20.7 - 28.5 2.86 - 4.36 489 -730 Hue et al (2012)

-Cassava Stems 33.7 ± 0.69 5.7 ± 0.06 60.3± 0.49 - 108.6 ±1.12 Lam (2013)

3.2.3 Using cassava foliage for goat production

Many studies have focused on cassava foliage as a feed for animals, especiallyfor ruminants Fresh cassava foliage, cassava leaves, cassava hay; cassava foliagesilage has been fed to cattle, with good results (Thang et al., 2010; Wanapat, 2009,Truong Van Hieu et al., 2014)

According to Sath et al (2008), increasing the level of sun-dried cassava foliage

and para grass Maximum weight gain and N retention were achieved when 40% oftotal N intake (1.3 g CP/kg BW) came from cassava foliage, corresponding to about 0.7

kg DM/100 kg BW, while higher cassava intake did not further improve animalperformance Cassava foliage is also a good protein source for small ruminants.Feeding cassava foliage (wilted, sun-dried or ensiled) to goats housed at night afterday-time grazing increased growth rates and reduced nematode parasite egg counts(Phengvichith et al., 2011)

Previous studies showed that feeding cassava foliage hay to penned goatsresulted in improved growth performance (Ngo Tien Dung et al., 2005; Phengvichith etal., 2006) An additional benefit from feeding cassava foliage to goats is that the tanninsappear to modify or control nematode infestations (Seng Sokerya et al., 2003)

Fresh or sun-dried cassava foliage is a valuable supplement for goats receiving low ormedium quality diets (Kounnavongsa et al., 2010)

3.2.4 Antinutritional factors (Tannin and HCN) of cassava forage

Besides the high protein content found in cassava forage, it also has acomponent that significantly affects the digestion of food and the metabolism of rumennutrients that is tannin and HCN These two substances will affect the ability to eat, anddigestibility for animals, especially ruminants According to Sousa et al (2003), sheepand goats are considered to be highly susceptible to HCN toxification, and the tolerancelevel of sheep was 2.0 to 4.0mg HCN/kgBW (Conn, 1979; Kumar, 1992) Aslani et al.(2004) gave doses corresponding to 5.8 and 10mg HCN/kg So, cassava leaves’ use asgoat feed is limited

Cassava plant is a sources of protein and good energy for livestock feed, butusing fresh cassava forage as a feed for ruminants can be a problem due to its fairlyhigh content of hydrogen cyanide (Hue et al., 2010) According to Ravindran (1993),the normal range of HCN content in cassava foliage is 200 to 800 mg/kg of freshleaves, with the variation being attributed to genetic, physiological and edaphic factors,and climate One of the more important differences between different varieties ofcassava is in the content of HCN The cyanide levels in cassava depend on the varietyand age of the plant, the soil conditions, presence of fertilizer and weather, among otherfactors (Ngiki et al., 2014)

In many cases the varieties with high HCN content are referred to as very bitter

or bitter varieties while those low in HCN are classified as sweet varieties (Mlingi etal., 1995) HCN content in leaves was higher than in petioles or stems and the content

in leaves varied less in soils than in varieties (Arvidsson et al., 2003) There wereconsiderable differences in chemical composition of the foliage from different varietiesharvested at different harvest occasions, harvest interval

The cyanide concentration of root parenchyma was less variable than that ofleaves and root peel; It showed a higher cyanide content in the parenchyma (900 to

1000 mg/kg DM) than the other three cultivars, which ranged from 100 to 200 mg/kg

DM The local cultivar was the only one in which the cyanide content of leaves washigher than that of the root peel (Gómez et al., 1985); the HCN content in cassavafoliage was much lower in the local variety and it also declined with foliage maturity

According to Hue et al (2012) the content of total tannins in cassava foliageincreased with increasing leaf maturity at the harvest but no differences were obtainedbetween varieties Another important aspect of cassava foliage is the content ofcondensed tannins Khang et al (2005) reported that unlike HCN, the content ofcondensed tannins in foliage increased at longer harvest intervals, ranging fromapproximately 3.5% of DM at 45 days harvest interval to around 4.3% of DM at rootharvest stage Significant tannin differences in varieties was also reported by Oni et al.(2011) The impact of condensed tannins in cassava forage on protein digestibility wasstudied by Reed et al., 1982 but information addressing cassava harvested for forage isstill limited The levels of the anti-nutrients (cyanide, phytate, oxalate and tannin) wassignificantly reduced by processing of cassava roots such as cooking, fermentation andsoaking, and hence render the processed roots safe for human consumption, animals.(John Manano et al., 2017)

The tannins are traditionally broadly divided into two categories: hydrolysabletannins (HTs) or condensed tannins (CTs) on the basis of their structure; Hydrolysabletannins have a central carbohydrate core the hydroxyl groups of which are esterified tovarious phenolic carboxylic acids This group of tannins is easily hydrolyzed to giveglucose or a polyhydroxy alcohol and the various phenolic acids The way in whichtannins affect animal performance is not exactly clear Tannins form complexes withproteins and carbohydrates in the feeds, and with digestive enzymes As a results

nutrient digestibility is depressed Other effects of tannins include reduced feed intake,increased damage to the gut wall, toxicity of absorbed tannins and reduced absorption

of some minerals These effects can largely be attributed to condensed tannins.Condensed tannins reduce protein degradation in the rumen and increase the flow ofamino acids to the intestine for absorption (Waghorn et al., 1994)

3.2.5 Reducing methods antinutrients factor in cassava foliage

The tannin and HCN contents of cassava depend on the variety, harvestinginterval, proportion of cassava, and processing method (Table 1.2)

Table 1.2 Tannin and HCN content of cassava foliage

Drying is the most popular practice used to reduce cyanide content of cassava.Sun drying is more effective at eradicating cyanide than oven-drying because with thismethod the cyanide is in contact with linamarase for a longer period (Ngiki et al.,2014) Ravindran (1991) stated that sun-drying alone can eliminate almost 90% ofinitial cyanide content Tewe and Iyayi (1989) compared the HCN level in fresh, oven-dried and sun-dried cassava The HCN levels in the root, pulp and peel were amaximum of approximately 416, 200 and 815 mg/kg respectively in the fresh samples,

64, 31 and 1,250 mg/kg in the oven-dried samples and 42, 27 and 322 mg/kg in thesun-dried samples Ravindran et al (1987) found that fresh cassava leaves had anaverage HCN content of 1,436 mg/kg, but when they were sun-dried this was reduced

to 173 mg/kg Additionally, Khajarern et al (1982) found HCN content was reducedfrom 111.83 to 22.97 mg/kg when cassava roots were sun-dried for 6 days Gomez et

al (1984) found that more than 86% of HCN in cassava 1984 was lost by sun-dryingdue to evaporation of free cyanide at 28 °C

Furthermore, cassava hay contains only 2-4% condensed tannins as compared tomore than 6% in mature cassava leaves at time of root harvest Producing cassava hay

as a high-protein fodder is a means of increasing the protein to energy ratio of thewhole cassava crop (Wanapat, 2001)

Fermentation also reduces the cyanide content of cassava products Freshcassava root contains approximately 400 to 440 mg/kg HCN which can be reduced to

84 mg/kg by wet fermentation and 14 mg/kg by solid-state fermentation (Muzanila etal., 2000), and to 15 or 8 g/kg when turned into unfermented or fermented meal,respectively (Udedibie et al 2004) Soaking of cassava roots preceding cooking andfermentation can enable heightened extraction of soluble cyanide by removingapproximately 20% of free cyanide in the fresh root after 4 h (Tewe, 1991) Boilingcassava chips also removes some of the cyanide; approximately 90% of free cyanide isremoved within 15 min of boiling and 55% of the bound cyanide is removed after 25min of boiling (Cooke and Maduagwu, 1985) Okoli et al (2012) found that there isgreat variation in the physiochemical and HCN contents of cassava processed bydifferent methods Samples that had been peeled, fermented and sun-dried had higherwater holding capacity and digestible fibre compared with samples not exposed to thesemethods, and samples that has been oven toasted prior to milling had higher crude fibreand HCN values compared with samples that were not toasted (100 – 200 mg/kgcompared with 5 – 15 mg/kg) In conclusion, there is not one optimum method forprocessing cassava, but rather a combination of different techniques is required based

on the specific variety of the cassava

Ensiling also reduced the HCN content of cassava products Ensiling is oneamong several techniques recommended for practical conditions to preserve the quality

of feed materials during periods of excess (McDonald et al., 1991) An advantage ofthis method is that plant materials can be preserved at any time of the year, even whenweather conditions are not suitable for sun-drying The ensiling process ensures notonly increased shelf life and microbiological safety, but it also makes most foodresources more digestible (Caplice and Fitzgerald, 1999) It has also been shown that

fermentation of cassava leaf and foliage reduces toxicity levels of HCN (Chhay et al.,2001; Sokerya et al., 2009).

According to Dang Hoang Lam (2013), HCN content of cassava stems wasstrong reduced by treated with urea or molassic silage HCN content of cassava stemstreated with urea was lower than HCN content of cassava stems silage Specially,cassava stems treated with 2.5% urea after, HCN content was not detected

On the other hand, using brewer’s grain from the small amounts is as a

“prebiotic” in reducing the sub-clinical toxicity caused by the cyanogenic glucosides inthe cassava foliage According to Phuong et al (2016) reported that major benefits ingrowth of cattle (from zero to 600g/day) when brewers’ grains (at only 4% of the dietDM) were added to a similar diet of cassava pulp-urea-cassava foliage (bitter variety)

It was also observed that urinary excretion of thiocyanate was substantially reduced bysupplementation with the brewers’ grains These authors concluded that the benefitsfrom the small amounts of brewers’ grains (4% of diet DM) possibly were due to a

“prebiotic” effect of this supplement in reducing the sub-clinical toxicity caused by thecyanogenic glucosides in the cassava foliage

4 IMPROVING GOAT PRODUCTION AND REDUCTION OF METHANE EMISSION PRODUCTION

4.1 IMPROVING STRATEGY GOAT PRODUCTION

Livestock development in An Giang is an urgent and practical issue, especiallygoat raising, as goat production is one of the solutions that can help farmers increase theirincomes and solve the problem of jobless farmers, and less land for production Thenatural conditions are erratic in this area, agricultural byproducts are over-harvested butthere are shortages in dry season or flood in rainy season Because the livestock farmersare small scale and employ traditional raising systems, they do not know how to stockpile

or produce agricultural byproducts immediately after harvesting to ensure that feed isavailable throughout the year This problem was interesting for the An Giang provinceGovernment, and they developed policies for farmers such as training for technology toimprove nutritive value of agricultural by products, and processing

4.2 CLIMATE CHANGE AND REDUCTION OF METHANE EMISSION PRODUCTION

In recent years Vietnam has suffered the negative effects of climate changeincluding droughts, strong storms, flooding, and slash lands, which have caused lost ofagricultural production and affected human livelihoods Do Thi Thanh Van (2006)reported that goats’ thriving in harsh tropical environments represents a climax in thedomestic ruminant’s capacity to adjust to such areas, where water sources are scarcelydistributed, and feed sources limited in quantity and quality The ecological,physiological and feed adaptive behavior of goats in the unfavorable tropics makes them

an appropriate candidate to sustain livestock production in the context of climate change

Greenhouse gases are the main reasons causing this phenomenon To adapt tothe climate change, goats as the ruminant, its production needs to mitigate the CH4 and

CO2 in the management, therefore number of studies aimed to abate the entericgreenhouse gases emissions without reducing the production yields has been done The

recent studies have mainly been in vitro screening of good nutrients, agents and feed

sources to potentially reduce greenhouse gases such as essential oils, protein sources,

probiotics, TMR, silages, etc After that the in vivo studies could be tested and

successful ones could be implemented

There are many studies that have been conducted with hypothesis reducingmethane production

The reduction in methane emissions was calculated on the basis that carbon dioxideproduction reflects energy utilization by the animal, so the ratio of methane to carbondioxide in eructed gas is a measure of the relative production of methane as a function ofthe intake of metabolizable energy (Madsen et al., 2010; Leng and Preston, 2010)

Kongvongxay et al (2011) investigated the effects of four different levels of atannin-rich foliage (Mimosa pigra) on feed intake, digestibility, nitrogen retention andmethane production in four goats fed a basal diet of Muntingia calabura Each goat wasprovided with each of the diets for a period of 10 days Rumen fluid, urine and faeceswere chemically analyzed to monitor the effects of the diet, and each goat was placedinside a sealed chamber (made with a bamboo frame and plastic sheeting) after thesecond and fourth feeding period to measure the methane: carbon dioxide ratio oferucted gas The results showed the greatest methane reduction (42%) with 72% of thedietary N from mimosa

Sophea and Preston (2011) investigated the effects of different levels ofsupplementary potassium nitrate replacing urea on the growth rates and methaneproduction in goats fed rice straw, mimosa foliage and water spinach It was postulatedthat nitrate could replace carbon dioxide as an electron acceptor in the rumen with thegeneration of ammonia instead of methane In this reaction, nitrate is reduced to nitriteand then to ammonia, resulting in lower methane gas emission Therefore, it washypothesized that a nitrate salt could potentially replace urea as a source of non–proteinnitrogen (NPN) because, as with urea, it would provide a fermentable nitrogen sourcefor microbial protein synthesis.

Leng et al (2012) explored the hypothesis that there will be an additive effect

on reduction of methane emissions from adding both biochar (increasing the potentialmicrobial habit) and nitrate to the diet of cattle fed a basal diet of fresh cassava rootchips supplemented with fresh cassava leaves Twelve young local “Yellow” cattleundertook a trial that lasted 98 days following a 21 days period of adaptation to thediets At the end of the experiment, a sample of mixed eructated and respired gas fromeach animal was analyzed for methane and carbon dioxide using the Gasmet equipmentbased on the approach suggested by Madsen et al (2010) Live weight gain wasincreased 25% by adding biochar to the diet and tended to be decreased when nitratereplaced urea Feed conversion was improved by biochar and by urea replacing nitrate.Feed intake was not affected by supplementation with biochar nor by the NPN source.Both biochar and nitrate reduced methane production by 22% and 29%, respectively;the effects being additive (41% reduction) for the combination of biochar and nitrate

The availability of brewers’ grains is limited to locations close to beerfactories, Keopaseuth et al (2017) therefore investigated the use of Cassava foliage;replacing brewer’s grains as a protein supplement for twelve Yellow cattle fed cassavapulp-urea and rice straw The maximum growth rate was recorded when the brewers’grains provided 9-17% of dietary dry matter, and the ratio of methane to carbon dioxide

in mixed eructed gas and air declined dramatically with a curvilinear trend as the freshcassava foliage replaced brewers’ grains in the diet