SỬ DỤNG CÂY KHOAI MÌ (SẮN) ĐỂ PHÁT TRIỂN CHĂN NUÔI DÊ Ở AN GIANG, VIỆT NAM

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

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


Hue University, 2020

Le Thi Thuy Hang, PhD. Student

i


DEDICATION
To my parents who taught me the good things in my life, my loving husband
and my sons.

ii


ACKNOWLEDGEMENTS
These studies were carried out at An Giang University, Hue University of
Agricultural and Forestry, Hue University with financial support from the Mekong
Basin Animal Research Network (MEKARN II) Project. I am grateful for their support
for 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 social
activities. He has given me invaluable support, encouragement and guidance
throughout my study. His reading, editing and follow -up of this thesis are gratefully

acknowledged.
Dr. Dinh Van Dung, my second supervisor, who has given me invaluable
support, encouragement, criticism, excellent skilled technical assistance and guidance
throughout my study.
Professor Thomas R. Preston, who has given me invaluable support, for valuable
advice, encouragement, enthusiasm and discussions throughout the study. His reading
and 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 and
Forestry for giving us the best conditions, encouragement and support during our
studies in Hue.
Dr. Khieu - Borin, Regional Coordinator of Mekarn II Project “Vietnam –
SAREC Sustainable Livestock Production Systems” project, for valuable advice and
discussions.
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 attended
during my studies for sharing their valuable knowledge.
Associate Prof. Dr. Vo Van Thang, Rector of An Giang University for giving
me permission to study, facilitation and encouragement.

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My Dean, Dr. Ho Thanh Binh, Dean of Agriculture and Natural Resources
Faculty of An Giang university for giving me permission to study, facilitation and
encouragement.
My colleagues at the Department of Animal Husbandry and Veterinary
Medicine of Agriculture and Natural Resources Faculty of An Giang University for
performing the chemical analyses and sharing experiences in scientific research and

social 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 my
work, and shared the happiness and sadness with me, for his loving, unceasing support
and patience for my whole- life study.

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ABSTRACT
The aims of the study were to improve utilization cassava forage for increasing
performance and reducing enteric methane emission in goat fed cassava forage
restricted level of brewery grain and biochar in An Giang province, Vietnam. There
were one survey and four experiments in this study.
The survey of cassava and goat systems in Tinh Bien and Tri Ton districts, An
Giang province showed that there is an increasing tendency to plant cassava. At the
same time there are major trends in the population of goats increasing. However, goat
production systems were still extensive, exploiting natural feed resources with small
herds of indigenous goats, which have small sizes and low growth rates. Feed and
feeding for goats were mainly natural grass and by-products, from crop growing, low
nutrition. It is not enough feed in rainy and flooding season. Whole, cassava forage
averaginge 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 its
chemical properties was investigated (Experiment 1). The urea treated cassava stems
(UCS) (3% in DM) made good quality ensilage, with no loss in nutritive value that
could be stored up to 8 weeks. An additional benefit was that the urea treatment
reduced the content of HCN in the ensiled stems.

Base on these results of the experiment 1, experiment determined the effect on
feed intake, digestibility and N- retention in goats of supplementing the urea treated
cassava stems (UCS) with fresh water spinach and biochar (Experiment 2). DM
intake was increased 18% by supplementing the UCS with biochar; and by 24% by
addition of water spinach. The combined effect of biochar plus water spinach was to
increase DM intake by 41%. Biochar increased daily N retention by 46% and the
biological value of the absorbed N by 12%. It is thought that this major benefit from
biochar arises from the role it plays as physical support for biofilms acting as habitat
for diverse microbial communities working for the benefit of the host animal and thus
acting as a form of prebiotic.
Experiment 3 describes the addition of increasing levels of brewers’ grains (0 to
6%) 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 retention
v


and the biological value of the absorbed nitrogenous compounds. The methane levels in
eructed gas increased with a curvilinear trend as the proportion of brewers’ grains in the
diet was increased.
The benefits of biochar were tested further in experiment 4. Twelve growing
male goats of the Bach Thao breed, were given a basal diet of ad libitum fresh cassava
forage supplemented with 4% (DM basis) of brewers’ grain. The biochar was supplied
over the range of 0 to 1.5% in diet DM. Responses in feed intake, live weight gain and
feed conversion to biochar followed curvilinear trends with optimum benefits when
biochar was added at 0.86% of the diet DM. By contrast, the eructed methane
production was decreased linearly with level of biochar.
Key word: Cassava stems, cassava forage, brewers’ grain, liveweight gain,
biochar, methane emission

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TABLE OF CONTENTS
DECLARATION .............................................................................................................. i
DEDICATION ................................................................................................................. ii
ACKNOWLEDGEMENTS ............................................................................................ iii
ABSTRACT .....................................................................................................................v
TABLE OF CONTENTS .............................................................................................. vii
LIST OF FIGURES ....................................................................................................... xii
LIST OF TABLES ........................................................................................................ xiv
LIST OF ABBREVIATIONS, SYMBOLS AND EQUIVALENTS ................................. xvi
INTRODUCTION ............................................................................................................1
1. PROBLEM STATEMENT ...........................................................................................1
2. AIMS AND OBJECTIVES OF THE STUDY .............................................................2
2.1. THE AIMS OF THE STUDY ...................................................................................2
2.2 OBJECTIVES OF THE STUDY................................................................................2
3. RESEARCH HYPOTHESES .......................................................................................2
4. SIGNIFICANCE/INNOVATION OF THE DISSERTATION....................................3
4.1 SCIENTIFIC SIGNIFICANCE ..................................................................................3
4.2. PRACTICAL SIGNIFICANCE ................................................................................3
CHAPTER 1 OVERVIEW OF RESEARCH ISSUES ....................................................4
1. GOAT PRODUCTION SYSTEMS IN AN GIANG....................................................4
1.1 GEOGRAPHICAL LOCATION AND CLIMATE IN AN GIANG .........................4
1.2. GOAT RAISING SYSTEMS IN AN GIANG ..........................................................4
1.2.1 Goat population and management ...........................................................................4
1.2.2. Feed and feeding management for goat ..................................................................7
1.3. OPPORTUNITIES AND CHALLENGE FOR GOAT PRODUCTION ..................9
2. THE DIGESTIVE SYSTEMS AND ENTERIC METHANE EMISSION IN
RUMINANTS.................................................................................................................11
2.1. RUMEN FERMENTATION AND METHANE PRODUCTION ..........................11

2.1.1. Rumen fermentation .............................................................................................11
2.1.2. Volatile fatty acids pattern ....................................................................................12
2.1.3. Protein metabolism ...............................................................................................13
2.2. METHANE PRODUCTION ...................................................................................14
2.2.1. Pathway of methane production ...........................................................................14
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2.2.2. Manipulation in mitigation of methane production ..............................................16
3. POTENTIAL OF CASSAVA FORAGE FOR GOAT PRODUCTION ....................19
3.1. PLANT AREA AND DISTRIBUTION OF CASSAVA AND YIELD OF
CASSAVA IN VIETNAM, AN GIANG .......................................................................19
3.2. POTENTIAL OF CASSAVA FORAGE FOR GOAT PRODUCTION .................21
3.2.1. Proportion yield of parts of cassava forage .........................................................21
3.2.2. Composition of cassava forage, parts of cassava forage ......................................21
3.2.3. Using cassava foliage for goat production............................................................21
3.2.4. Antinutritional factors (Tannin and HCN) of cassava forage ...............................22
3.2.5. Reducing methods antinutrients factor in cassava foliage ...................................24
4. IMPROVING GOAT PRODUCTION AND REduction of METHANE EMISSION
PRODUCTION...............................................................................................................26
4.1. IMPROVING STRATEGY GOAT PRODUCTION ..............................................26
4.2.

CLIMATE

CHANGE

AND

REduction

of

METHANE

EMISSION

PRODUCTION...............................................................................................................27
5. CONCLUSIONS ........................................................................................................29
CHAPTER 2 EVALUATION OF THE POTENTIAL OF CASSAVA forage AS FEED
FOR GOATS IN AN GIANG PROVINCE, VIETNAM ...............................................42
1. INTRODUCTION ......................................................................................................42
2. MATERIALS AND METHODS ...............................................................................43
2.1. THE FOLLOWING INDICATORS WERE USED IN THE INVESTIGATION OF
THE SURVEY ................................................................................................................43
2.2. DATA COLLECTION AND CALCULATION .....................................................44
2.3. CHEMICAL ANALYSIS ........................................................................................45
2.4. STATISTICAL ANALYSIS ...................................................................................45
3. RESULTS AND DISCUSSION .................................................................................46
3.1. CASSAVA PRODUCTION IN AN GIANG PROVINCE .....................................46
3.1.1. The production and yiled of cassava ....................................................................46
3.1.2. Plant area of cassava by district from 2014-2017 .................................................46
3.1.3. Yield of cassava with different of variety in An Giang ........................................48
3.1.4. Planted area and the purposes of cassava cultivation ...........................................48
3.1.5. Evaluation of chemical composition of cassava parts ..........................................50
3.1.6. The fresh and dry yield of cassava proportion with different variety..................50
3.2. GOAT PRODUCTION IN AN GIANG PROVINCE.............................................51

viii

3.2.1. Ruminants population in An Giang from 2014- 2017 ..........................................51
3.2.2. Goat farm size and purpose raising in An Giang province ...................................52
3.2.3. Goat prodution systems in An Giang....................................................................53
3.2.4. Feed and feeding systems .....................................................................................54
3.2.5. Diseases and diseases management .....................................................................55
4. CONCLUSIONS ........................................................................................................56
CHAPTER 3 USING UREA TO TREAT CASSAVA STEMS AND EFFECT OF
WATER SPINACH AND BIOCHAR ON FEED INTAKE, DIGESTIBILITY AND NRETENTION IN GOATS FED UREA TREATED CASSAVA STEMS .....................60
1. INTRODUCTION ......................................................................................................61
2. MATERIALS AND METHODS ...............................................................................63
2.1. EXPERIMENT 1 .....................................................................................................63
2.2. EXPERIMENT 2 .....................................................................................................64
3. RESULTS AND DISCUSSION .................................................................................68
3.1 EXPERIMENT 1 ......................................................................................................68
3.1.1 Hygienic quality of cassava stems treated by physical evaluation ........................68
3.1.2. Chemical compositions of cassava stems treated with difference levels of urea
and stored times ..............................................................................................................70
3.2. EXPERIMENT 2 .....................................................................................................76
3.2.1. Composition of the diet ingredients ......................................................................76
3.2.2. Feed intake and digestibility .................................................................................77
3.2.3. Nitrogen retention .................................................................................................80
4. CONCLUSIONS ........................................................................................................82
CHAPTER 4 EFFECT OF DIFFERENT LEVELS OF BREWERS’ GRAINS
SUPLEMENTATION ON PERFORMANCE AND METHANE EMISSION OF
GOATS FED CASSAVA FORAGE ..............................................................................87
1. INTRODUCTION ......................................................................................................87
2. MATERIALS AND METHODS ...............................................................................88
2.1. EXPERIMENTAL DESIGN ...................................................................................88
2.2. ANIMALS AND MANAGEMENT........................................................................88

2.3. FEEDS AND FEEDING .........................................................................................89
2.4. DIGESTIBILITY AND N RETENTION ................................................................89
2.5. RUMEN PARAMETERS .......................................................................................89
2.6. RUMEN GAS EMISSIONS ....................................................................................90

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2.7. ANALYTICAL PROCEDURES.............................................................................90
2.8. STATISTICAL ANALYSIS ...................................................................................90
3. RESULTS AND DISCUSSION .................................................................................90
3.1. COMPOSITION OF DIET INGREDIENTS ..........................................................90
3.2. FEED INTAKE AND DIGESTIBILITY ................................................................91
3.3. RUMEN PARAMETERS .......................................................................................93
3.4. NITROGEN RETENTION .....................................................................................94
3.5. LIVE WEIGHT GAIN AND FEED EFFICIENCY ................................................96
3.6. METHANE EMISSIONS ........................................................................................98
4. CONCLUSIONS ........................................................................................................99
CHAPTER 5 EFFECT OF BIOCHAR SUPPLEMENTATION LEVELS ON
GROWTH AND METHANE EMISSIONS OF GOATS FED FRESH CASSAVA
FORAGE ......................................................................................................................102
1. INTRODUCTION ....................................................................................................102
2. MATERIALS AND METHODS .............................................................................103
2.1. LOCATION AND DURATION ...........................................................................103
2.2. EXPERIMENTAL DESIGN .................................................................................103
2.3. FEEDING AND MANAGEMENT .......................................................................104
2.4. MEASUREMENTS ...............................................................................................105
2.5. ERUCTED GAS EMISSIONS AND ANALYSIS ...............................................106
2.6. ANALYTICAL PROCEDURES...........................................................................106
2.7. STATISTICAL ANALYSIS .................................................................................106

3. RESULTS AND DISCUSSION ...............................................................................107
3.1. COMPOSITION OF DIET INGREDIENTS ........................................................107
3.2. FEED INTAKE .....................................................................................................107
3.3. GROWTH AND FEED CONVERSION ..............................................................108
3.4. METHANE EMISSION ........................................................................................111
4. CONCLUSIONS ......................................................................................................113
CHAPTER 6 GENERAL DISCUSSION AND CONCLUSIONS ..............................117
1. GENERAL DISCUSSION .......................................................................................117
1.1. POTENTIAL OF CASSAVA IN VIETNAM .......................................................117
1.2 EFFECT ON NUTRITIVE VALUE OF CASSAVA (MANIHOT ESCULENTA
CRANTZ) STEMS OF ENSILING THEM WITH UREA ...........................................118

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1.3 DIGESTIBILITY, NITROGEN BALANCE AND METHANE EMISSIONS IN GOATS
FED CASSAVA FORAGE AND RESTRICTED LEVELS OF BREWERS’ GRAINS ....118
1.4 EFFECT OF BIOCHAR AND WATER SPINACH ON FEED INTAKE,
DIGESTIBILITY AND N-RETENTION IN GOATS FED UREA-TREATED
CASSAVA STEMS ......................................................................................................119
1.5. EFFECT OF BIOCHAR ON GROWTH AND METHANE EMISSIONS OF
GOATS FED FRESH CASSAVA FORAGE. .............................................................120
2. GENERAL CONCLUSIONS ...................................................................................120
3. IMPLICATION AND FUTHER RESEARCH ........................................................121
3.1 IMPLICATIONS ....................................................................................................121
3.2 FUTURE RESEARCH ...........................................................................................122
PUBLICATION LIST ..................................................................................................126

xi

LIST OF FIGURES
Figure 1.1. Number of goats in An Giang from 2012 -2017 ............................................4
Figure 1.2. Distribution of goat by district in An Giang, 2017 ........................................5
Figure 1.3. Farmers buy grass from another region..........................................................8
Figure 1.4. Microbes needed for fermentation (Leek, 1993) ..........................................11
Figure 1.5. Metabolic pathways of VFA (Bergman, 1993) ............................................12
Figure 1.6. The reaction of methane generation .............................................................15
Figure 1.7. Plant area of cassava in Vietnam, 2017........................................................19
Figure 2.1. Cassava plant parts .......................................................................................45
Figure 2.2. Cassava forage parts .....................................................................................45
Figure 3.1. Freshly harvested cassava stems ..................................................................64
Figure 3.2. Chopping into 5-10 cm lengths ....................................................................64
Figure 3.3. Urea added at 3% of stems DM ...................................................................64
Figure 3.4. Chopped stems-urea are put in polyethylene bags and the air extracted .....65
Figure 3.5. Urea-treated stems are stored for 21 days ....................................................65
Figure 3.6. Urea-treated stems after 21-day storage ready for feeding ..........................65
Figure 3.7. The biochar was the residue from rice husks used as fuel in a gasifier stove
(Olivier) ..........................................................................................................................66
Figure 3.8. Biochar, water spinach and urea-treated cassava stems were fed in separate
troughs ............................................................................................................................66
Figure 3.9. Supplements of water spinach and biochar increased DM intake by goats
fed urea-treated cassava stems ........................................................................................79
Figure 3.10. Effect of water spinach on DM digestibility in goats fed urea-treated
cassava stems with or without a supplement of biochar .................................................80
Figure 3.11. Effect of biochar on DM digestibility in goats fed urea-treated cassava
stems with or without a supplement of water spinach ....................................................80
Figure 3.12. Effect of water spinach on N retention in goats fed urea-treated cassava stems
with or without a supplement of biochar ...........................................................................81
Figure 3.13. Effect of biochar on N retention in goats fed urea-treated cassava stems

with or without a supplement of water spinach ..............................................................81
Figure 3.14. Effect of water spinach on N retention as % of digested N in goats fed
urea-treated cassava stems with or without a supplement of biochar .............................81

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Figure 3.15. Effect of biochar on N retention as % of digested N in goats fed ureatreated cassava stems with or without a supplement of water spinach ...........................81
Figure 4.1. Relationship between dry matter inatke and different level of brewers’ grain
in goats fed cassava forage. ............................................................................................92
Figure 4.2. Correlation between the differnce level of brewers’ grains and apparent
digestibility of DM and CP ...............................................................................................93
Figure 4.3. Relationship between different levels of brewers’ grains and rumen
ammonia before and after offering new morning feed. ..................................................94
Figure 4.4. Relationship beween of dietary level of brewers’ grains and N retention as a
percentage of N digested ................................................................................................95
Figure 4.5. Relationship between live weight gain and different levels of brewers’
grain in goats fed cassava forage. ...................................................................................97
Figure 4.6. Effect of level of brewers’ grains on DM feed efficiency............................97
Figure 4.7. Effect of increasing intake of brewers’ grains on the methane: carbon
dioxide ratio in mixed air-expired breath of the goats fed a basal diet of fresh cassava
forage. .............................................................................................................................98
Figure 5.5. Curvilinear response of DM intake of goats to percent biochar in a cassava
forage diet with the optimum level at about 0.8 % biochar in DM ..............................108
Figure 5.6. Curvilinear response of live weight gain of goats to percent biochar in a
cassava forage diet with the optimum level at about 0.86 % biochar in DM ...............110
Figure 5.7. Growth response curves to biochar with water retention capacities of 3.81
and 4.89 fed in succeeding periods (-15 to + 10 days) and 10-90 days) ......................110
Figure 5.8. Linear reduction in methane: carbon dioxide ratio in eructed gas of goats
fed up to 1.3% biochar in a diet of cassava forage .......................................................112

Figure 6.1. Forage and stems that remain when the cassava roots are harvested .........117

xiii


LIST OF TABLES
Table 1.1. The chemical composition of cassava forage variety ....................................21
Table 1.2. Tannin and HCN content of cassava foliage .................................................24
Table 2.1. Plant area of cassava in An Giang from 2014-2017 ......................................46
Table 2.2. Plant area of cassava in An Giang province ..................................................48
Table 2.3. Yield of cassava with different variety in 2017 .............................................48
Table 2.4. Plant area of cassava cultivation in An Giang ...............................................49
Table 2.5. Chemical composition of cassava parts .........................................................50
Table 2.6: Yield of cassava proportion with different variety ........................................51
Table 2.7. Population of ruminants in An Giang from 2014- 2017 ...............................52
Table 2.8. Farm size and purpose raising ......................................................................53
Table 2.9. Goat production systems in Tri Ton and Tinh Bien district ..........................53
Table 2.10. Feed and feeding systems for goats in Tri Ton and Tinh Bien district .......55
Table 2.11. Diseases and diseases management of goats ..............................................56
Table 3.1. The chemical composition of cassava stems before treating in experiment 164
Table 3.2. The layout of the experiment .........................................................................65
Table 3.3. Effect of urea level and storage time on pH in cassava stems .......................69
Table 3.4 : Effect of urea level and storage time on ammonia in cassava stems ............70
Table 3.5. Effect of urea level and storage time on HCN (mg/kgDM) content of
cassava stems. .................................................................................................................71
Table 3.6. Effect of urea level and storage time on tannins in cassava stems ................72
Table 3.7. Effect of urea level and storage time on DM of cassava stems ....................73
Table 3.8. Effect of urea level and storage time on crude protein in cassava stems ......74
Table 3.9. Effect of urea level and storage time on NDF in cassava stems ...................75
Table 3.10. Effect of urea level and storage time on ADF in cassava stems..................76

Table 3.11. Chemical composition of diet ingredients (UCS is urea-treated cassava
stems) in experiment 2 ....................................................................................................77
Table 3.12. Effect of biochar and water spinach on feed intake .....................................78
Table 3.13. Effect of water spinach and biochar on nutrient digestibility (%) in goats
fed urea treated cassava stems ........................................................................................79
Table 3.14. Nitrogen balance in goats fed urea-treated cassava stems supplemented
with or without fresh water spinach and biochar. ...........................................................80
Table 4.1. The layout of the experiment .........................................................................88
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Table 4.2. Composition of diet ingredients ....................................................................91
Table 4.3. Feed intake in goats fed cassava forage supplemented with different levels of
brewers’ grains................................................................................................................91
Table 4.4. Nutrient digestibility (%) in goats fed cassava forage supplemented with
different levels of brewers’ grains ..................................................................................93
Table 4.5. Protozoa numbers, ammonia and pH in rumen fluid, before and 4h after,
offering fresh feed in the morning ..................................................................................94
Table 4.6: N balance (g/day) in goats fed cassava forage supplemented with different
levels of brewers’ grain ..................................................................................................95
Table 4.7.

Live weight gain and feed efficiency in goats fed cassava forage

supplemented with different levels of brewers’ grain ....................................................96
Table 4.8. Mean values for the ratio methane: carbon dioxide in mixed eructed gas and
air in the plastic-enclosed chambers where the goats were enclosed over ten minutes
periods.............................................................................................................................98
Table 5.1. Composition of diet ingredients ..................................................................107
Table 5.2. Feed intake in goats fed increasing levels of biochar in a diet of fresh

cassava forage ..............................................................................................................108
Table 5.3. Live weight and feed conversion in goats fed increasing levels of biochar in
a diet of fresh cassava forage ........................................................................................109
Table 5.4: The ratio methane: carbon dioxide in eructed gases from goats fed cassava
forage supplemented with biochar ................................................................................111

xv


LIST OF ABBREVIATIONS, SYMBOLS AND EQUIVALENTS
ADF

Acid detergent fiber

ATP

Adenosine triphosphate

BW

Body weight

BSP

Brewery spent grain

CP

Crude protein

CT

Condensed tannins

CNP

Cyanogenic potential

CH4

Methane

CO2

Carbon dioxide

DM

Dry matter

EPG

Eggs per gram

FW

Fresh weight

GHG

Green house gas

EPS

Self-produced polymeric substance

HT

Hydrolysable tannins

HCN

Hydrogen cyanide

LW

Live weight

N

Nitrogen

ND

No detection

NDF

Neutral ditergent fiber

SCFA

Short -chain fatty acid

TMR

Total mix ration

VFA

Volatile fatty acid

WRC

Water retention capacity

xvi


INTRODUCTION
1. PROBLEM STATEMENT
An Giang province in the South of Vietnam, is a watershed province in the
Mekong Delta, and one of the largest cultivated areas in the Mekong Delta. The total
area of agricultural land is more than 282,676 ha, of which paddy land accounts for
85.2% (Statistic yearbook of An Giang, 2018). An Giang is one of the two provinces in
the Mekong Delta with hills and mountains, mostly in the northwest of the province, in
Tinh Bien and Tri Ton districts. This is the last mountain cluster of the Annamites, so
the geological features also have similarities with the Southern Truong Son. An Giang
has 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. The

rainy season is the least in February and the highest in September. The average
humidity is 75-80% (An Giang hydrometeorological Station, 2017). Due to the
topography, the land resources are divided into different types: alluvial soil, alkaline
soil, 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 this
mountainous area is not favorable because of its low productivity, lack of water for
irrigation in the dry season, but when the rainy season comes, some districts are
affected by floods eg: the flooding in 2018 affected hundreds of hectares of rice and
crops in the Mekong Delta. As Naqvi and Sejian (2011) showed droughts, flooding and
depletion of natural resources, were caused by global climate change. Therefore, goat is
one of animal species, selected to keep with its advantagous characteristics of low
water consumption, drought resistance and browsing behaviors adapting to feeds from
plants adapting to the sea water. Besides, goat production in An Giang has developed in
recent years. The number of goats were 13,950 head in 2017 (Statistic yearbook of An
Giang, 2018). Nguyen Binh Truong (2016) showed that in An Giang province, goats
were 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 the
season such as sweet potato, banana leaf, water spinach, lipstick around the house,
settling idle work, bringing economic efficiency to farmers. Some separate supplement
feeds are used such as coconut cake, soybean extraction meal, brewery waste, soya
waste, rice bran, etc., and concentrate is also supplemented with protein and energy
1


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 food
for ruminants but the farmers in An Giang do not use it.
Based on the above problems and threats, we hypothesize that utilization of
cassava forage for improving goat production and reducing enteric methane emission

from goat production in An Giang province, Vietnam. This study was designed to test
the hypothesis by addressing the following specific aims were to improve nutritive
value of cassava stems and stored by urea treatment. In addition, using brewers’ grain
and biochar supplied to improve growth rate and reduce methane emissions in a basal
diet 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 for
increasing 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, and
cassava forage for goats in An Giang Province.
- To determine level of urea addition to cassava stems for storage to improve
nutritive 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 and
growth in goats fed sweet cassava foliage as basal diet.
- To determine levels of biochar that would reduce methane production in goats
fed 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
production in An Giang.

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- Using urea to treat cassava stems will improve nutritive value and storge long
time 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, growth
and 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 goat
fed a basal diet of fresh cassava forage and brewery grain. (the best level of brewery
grain 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 Thao
goat’s diet, that is basal of fresh cassava foliage has improved growth and reduced
enteric methane emission from goat production.
4.2. PRACTICAL SIGNIFICANCE
- The results of the study are of scientific value for managers, researchers,
universities, graduate students and agricultural students’ references.
- The present results of show that adding urea to cassava stems can provide
storage to use as feed goat for year around, specially in flooding or rainy season.
- The study results of the dissertation serve as a scientific basis for businesses
and husbandry to use and coordinate goat diets towards reducing methane emissions.
- Introducing cassava forage as goats feed, reducing the HCN content,
improving growth and reducing methane emission with supplementing additive as
brewery grain and biochar.

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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 in
the 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 Tho
city (44,734 km), to the east by Dong Thap province (107,628 km). An Giang in the
geographical latitude of about 10 to 110 North latitudes, ie, close to the equator, so
temperature and precipitation are similar to the equatorial climate. There are two
seasons 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 to
November). 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

Number of goat (heads)

16,000
14,000
12,000
10,000
8,000
6,000
4,000

2,000
0

13,950
11,905
7,876
4,325
2,346

2012

3,006

2013

2014

2015

2016

2017

Year
Figure 1.1. Number of goats in An Giang from 2012 -2017
Source: Statistic yearbook of An Giang, 2018

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In recent years goat production in Vietnam has been developed very fast around
30.0% annually with the total population of 2,556,300 heads in 2017, due to high
demand of goat meat for consumption. Some projects of goat production funded by
Oxfam UK, associated with Mekong delta provinces, which show the effective
production 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 of
goats in 2012, which shows that the trend of goat production in An Giang gradually
develops, the farmers are interested in and develop goat husbandry. In recent years,
consumers have been more interested in nutritious food sources from goat meat, goat
meat market has increased, and the goat meat prices have also increased, but goat
farming is low investment, easy to manage, less risky, more diversified feed than other
ruminants like cattle. Therefore, raising goats will help farmers to earn higher profits.
- Distribution of goat by district in 2017
GOAT

Long Xuyen
Thoai Son,
City, 428
Cho Moi , 719
1,406
Chau Thanh ,
907

Chau Đoc
city, 234
An Phu, 840
Tan Chau,
1,774

Tri Ton,

2,245

Phu Tan,
2,045
Chau Phu,
924

Tinh Bien,
2,428

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 of
Phu Tan and Tan Chau in 2017. The number goats increased because the price of goat
meat has been high in recent years: Price of goat meat (3.2 USD/kg LW) compared to
beef cattle (2.5 USD/kg LW) (Do Thi Thanh Van et al., 2018). It is one of the reasons
and potential to develop goat production in An Giang province and Vietnam also. But

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goat production will be suitanable development, if it uses and improves by- products as
goat feed in this area efficiency.
- Goat raising purpose and farm scale.
In An Giang, goat raising began to develop in recent years (figure 1). The
number 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 by
small scale and with three main purposes: selling meat product; breeding; breeding and

meat. Goat farming for breeding and meat accounted for the highest proportion of
74.4% of goats, followed by raising 18.9% with selling meat product and 6.67% for
selling 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
female and sell meat with male goat after 7-8 months old. On the other hand, goats
were raised by farmers spontaneously, the farmers learn how to breed each other, so
that the number of goats per farms average 6-10 heads accounted for 28.9% (26/90
surveyed households). A few households raise from 1 to 5 heads per household (12/90
surveyed households), number of goats from 11- 15 heads/farm was 26.7% (24/90
surveyed households, from 16-20 heads/farm with 14.4% (15/90 surveyed households)
and the number 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
goat production 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 invest
too much money compared with raising pigs or cattle, goat farmers choose the trees
planted around the house to make 4-5cm square floor and wall paneling. Goat's cages
are made of simple materials such as bamboo, acassia aneura, coconut tree, etc. The
roofs are usually covered with leaves or tole. Therefore, 100% of the farmers make goat
cages, sheet metal roofs, convenient cleaning of effluent and leftovers of goats. Goat is
easy raising, less take care. They were raised by genetic traditional, therefore the
farmers did not use vaccine for goats.
With the advantages of low capital, easy to buy, to sell, goat raising is gradually
becoming a landlord for the poor farmers, who have limited land area or less productive

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land. In the context of rising food prices, the output of some livestock is limited. The

goat raising is attracting many families to participate by utilizing agricultural
byproducts profitably. In Vietnam the domestic markets of goat products are good.
Although the marketing of goat products, and meat are limited, the local markets for
them are very good for the producers. There is a high demand for goat meat in many
different areas of Vietnam from the North to the South and the rate of increase in the
number of goats annually is not sufficient to meet the demand. Therefore, many
farmers and companies are preparing to build large commercial farms with the
importation of dairy goat breeds from developed countries for both milk and meat (Do
Thi Thanh Van and Nguyen Van Thu, 2018).
1.2.2. Feed and feeding management for goat
Feed is one of the determining factors of goat efficiency. Feed for goats is as
diverse 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. Goat
feed 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 good
feed for goats. When feeding goats banana leaves 100% in diet, DM consumption about
2.62% of body weight (DM basic) with digestibility of DM and CP were 62.0% and
59.1%. At that time goats ate 100% banana stems, DM consumption was 1.25% of
body weight (Nguyen Huu Van, 2012b). According to the author, the use of banana
leaves 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 were
high but were not affected by NPN source. Even wild trees were a feed source for
goats, 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).

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