hue university hue university of agriculture and forestry

Effect of additives (brewer’s grains and biochar) and cassava variety (sweet versus bitter) on nitrogen retention, thiocyanate excretion and methane production by B[r]

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)

http://www.lrrd.org

Hue University, 2020

Le Thi Thuy Hang, PhD Student

DEDICATION

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

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

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

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

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

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

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

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 N-RETENTION 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

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

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

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

Figure 3.15 Effect of biochar on N retention as % of digested N in goats fed treated cassava stems with or without a supplement of water spinach 81Figure 4.1 Relationship between dry matter inatke and different level of brewers’ grain

urea-in goats fed cassava forage 92Figure 4.2 Correlation between the differnce level of brewers’ grains and apparent digestibility of DM and CP 93Figure 4.3 Relationship between different levels of brewers’ grains and rumen ammonia before and after offering new morning feed 94Figure 4.4 Relationship beween of dietary level of brewers’ grains and N retention as a percentage of N digested 95Figure 4.5 Relationship between live weight gain and different levels of brewers’ grain in goats fed cassava forage 97Figure 4.6 Effect of level of brewers’ grains on DM feed efficiency 97Figure 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 98Figure 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 108Figure 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 110Figure 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) 110Figure 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 112Figure 6.1 Forage and stems that remain when the cassava roots are harvested 117

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 4.2 Composition of diet ingredients 91Table 4.3 Feed intake in goats fed cassava forage supplemented with different levels of brewers’ grains 91Table 4.4 Nutrient digestibility (%) in goats fed cassava forage supplemented with different levels of brewers’ grains 93Table 4.5 Protozoa numbers, ammonia and pH in rumen fluid, before and 4h after, offering fresh feed in the morning 94Table 4.6: N balance (g/day) in goats fed cassava forage supplemented with different levels of brewers’ grain 95Table 4.7 Live weight gain and feed efficiency in goats fed cassava forage supplemented with different levels of brewers’ grain 96Table 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 98Table 5.1 Composition of diet ingredients 107Table 5.2 Feed intake in goats fed increasing levels of biochar in a diet of fresh cassava forage 108Table 5.3 Live weight and feed conversion in goats fed increasing levels of biochar in

a diet of fresh cassava forage 109Table 5.4: The ratio methane: carbon dioxide in eructed gases from goats fed cassava forage supplemented with biochar 111

LIST OF ABBREVIATIONS, SYMBOLS AND EQUIVALENTS

EPS Self-produced polymeric substance

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

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

- 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

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

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 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

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

Long Xuyen City, 428

Chau Đoc city, 234

An Phu, 840

Tan Chau, 1,774

Phu Tan, 2,045

Chau Phu, 924 Tinh Bien,

Thoai Son, 719

GOAT

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

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)

Cassava leaves and cassava foliage were also excellent protein supplement sources 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 of crude 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 of cassava 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 main problems 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 Khang and Wiktorsson (2006), Promkot et al (2007) and Phengvichith and Ledin (2007), the HCN content in fresh cassava foliage was 983, 1179 and 325 mg/kg, respectively, while only 225 mg/kg was recorded in the experiment of Thang et al (2010) Therefore, when using fresh cassava foliage or cassava leaves as goat feed, they should

be reduced HCN content by processing This is also a worry of the farmers in An Giang, because they did not know to use cassava as feed for ruminants, they are afraid

of ruminants poisoning Therefore, cassava in An Giang is wasted or burned in the field, polluting the water and environmental pollution An Giang is province in Mekong delta, so it is affected by flooding every year There is flooding from August to November, and this cause 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 goat from another region According to Nguyen Thanh Binh (2018), agricultural byproducts abounded in the Mekong Delta (including An Giang), but they were used for cattle, and

buffaloes while goats are modest and mainly in fresh form, not processed to form a source of feed reserves with higher nutritive value If the farmers implement processing, then storage methods will contribute to solve the shortage of raw feed for ruminants 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% (60/90 surveyed households) In the semi-intensive systems, goats are grazed from 4-8 hours/day depending on the season, and additional feeds are supplemented at night with 32.2% (29/90) of surveyed households This system is found suitable to the existing goat farms in Vietnam In the extensive systems, goats are grazed on available pasture without supplementation This system is common in mountainous and forest areas for the meat goats, but low productivity, capital investment in breeding, breeding facilities, feed, veterinary medicine, and public care It is difficult to manage breeding and insemination among the animals in the herd, environmental pollution caused by faeces, or not fully utilized 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 when eating around the tree and eat only the most delicious food, then quickly move to the next tree and dust They like to eat at a height of 0.2-1.2m, they can stand on two feet to eat the 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 of the development strategies of the province and should be considered by the Government and investors Since 2015, An Giang People's Committee has many policies and strategies to support farmers development of livestock such as policies to support 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 mix ratio) with available local resources (broken rice, bran, corn etc)

To gradually shift small-scale farming to more intensive farms and from small and medium enterprises in livestock Strive to reach the total number of ruminants up to 200,000 heads by 2020, corresponding to the average growth rate of 10% per year for the period 2015-2020

To build and reorganize animal slaughtering systems in industrial districts in association with animal husbandry areas, veterinary hygiene, food safety and environmental treatment Simultaneously build modern slaughter facilities associated with export processing

Research to create value-added products from the livestock industry similar to cattle 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): to organize and manage the livestock sector more effectively, create higher value livestock and help diversification and promotion of trade in livestock products better

Recently, farmers and the local and central government of Vietnam have paid more attention to enhancing goat production such as producing the development policies, standards of goat farms, technical trainings and incentives for establishment of goat production cooperatives, larger intensive farms and extensive clubs, improved markets There have also been collaborations among the universities, companies and local institutions to create chances of investments on technology, finance and human resources for improving production and markets The veterinary networks, vaccines of common diseases, parasite preventions and effective medicines are available to protect the goat herds from diseases However, goats also produce CH4 and CO2 during their life time, which contribute to climate change Therefore, strategies for reducing green house gas emission of goats by feeding, nutrition balance, supplementations, and breeding, should be applied (Nguyen Van Thu and Nguyen Thi Kim Dong, 2015) for improving 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 the complex fiber source to provide essential nutrients that are readily digested by the host while this is completely restricted in non- ruminants (Owen and Basalan, 2016) In term

of biochemical metabolism, ruminant microbes secrete the enzyme that hydrolyses all macromolecule such as polysacharide, protein, lipid and other compounds to monomers 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)

8H 8H Methanogenic bacteria (pH>6.2)

Propionate bacteria (pH>6.2)

VFA CH4 CH4 VFA Propionate

Acetate Butyrate

TCA Cycl

Succinyl-CoA Propionyl-CoA

Propionate

2.1.2 Volatile fatty acids pattern

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

of acetic acid whereas high concentrate rations will result in slightly higher levels of propionic acid With by-product diet or dry pasture, poorly absorbed glucose thus gluconeogenesis play the major role to provide glucose needed for ruminant, while some starch 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 in rumen 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 to microbes leading to low fermentation rate In contrast, excessive ammonia results in ammonia toxicity for the animal Therefore, to utilize effectively, the conversion of ammonia to microbial protein requires the availability of ATP energy generated by the fermentation of carbohydrates In other words, it requires the balance between carbohydrate 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, and the remaining 40% is from ruminally un-degraded dietary protein In addition, the rumen can use effective sources of protein from by-product sources

The term of by-pass protein in rumen fermentation is defined to be protein that escapes the degradation of rumen microbes Two important factors influencing the amount of protein bypassing degradation in the rumen are the length of time spent in the rumen and fermentation of the protein (Miller, 2012) Leng et al (1981) indicated that by-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 addition increasing 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 by microbes, and microbial protein would escape the rumen to lower digestion to compensate protein needed of the animal, meanwhile, the by-pass protein can provide essential amino acids that are not synthesized by animal tissues, via absorption from digested 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 the desirable 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 degradable protein 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 N excretion 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 in early 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 Domesticated ruminants represents a loss of 2–15% of the gross energy (GE) intake by methane production (Holter and Young, 1992), therefore being one of most important factors contributing 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 of energy yielding (-130.7 kJ/mol substrate and -32.3 kJ/mol substrate respectively) The distribution of methanogen is diverse, it is assumed that they are free-swimming in fluid or attach to digested solid or attach to protozoa (Morgavi et al., 2010)

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

of enteric greenhouse gases emissions should be considered However, goats being small 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, three important strategies including nutritional, biotechnological and microbiological strategies are required for controlling and decreasing methane emission Carla et al (2016) showed that the replacement of cereal grain with fibrous by-products did not increase 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 diverse microbes in the rumen create overall synergistic and antagonistic interactions However, it is known that formate, carbon dioxide, methanol, and acetate derived from

carbohydrate fermentation are concerned as terminal electron receptor for hydrogen to form methane (Diagram 1) Based on biochemistry pathway, it can be seen that hexose metabolism via the Emden-Meyerhof-Parnas pathway (EMP) produces pyruvate as an intermediate associated with co-factor NADH generation (Leng, 2011) In the rumen, methane production from CO2 substrate as an electron acceptor is a predominant pathway 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 methane produced 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 to methanogenesis (Galand et al., 2005)

Figure 1.6 The reaction of methane generation

The process of methane production is a requirement in low partial pressure hydrogen, which is necessary for the continuous fermentation in the rumen (Figure 1.6) However, the inhibition of methanogenesis would redirect the available hydrogen into alternative energy-yielding metabolic pathways which are expected to improve the productivity 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 the expeulsion of hydrogen but there was no effect on both dry matter intake and fiber degradation The critical issue found in this study is that expelled H2 per mole of decreased methane was lower on steer fed roughage hay only diet compared with hay concentrate The evaluation of rumen microbial response in this study showed that

decreasing Archaea and Synergistetes for both diets accompanied with increasing Bacteroidetes (the bacteria involved in propionate production) but did not change fibrolytic bacteria, fungi, and protozoa These results can conclude that hydrogen was redirected 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 roughage hay in the diet is the suggestion in slowing fermentation that creates a condition for microbes 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 VFA production patterns and shift some digestion to the intestines;

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

Most microorganisms in the rumen and lower digestive tract use fermentation to fuel their cellular function and produce Short-Chain Fatty Acids (SCFAs) as a byproduct The SCFAs, namely acetate, propionate, and butyrate, are subsequently absorbed 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 microbial fermentation, and differences in feed digestibility and chemical composition alter the amount 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 propionate formation consumes fewer equivalents, whereas acetate and butyrate formation generate H2 for methanogenesis (Hungate, 1966) In this case, we also focus

to find the feed ingredients that can provide the substrates for microbial fermentation such as biofilm, and can control the proportion of VFA, reduce CH4 produced

Based on the mechanism of methane production, a series of studies in replacement 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 gradually increase nitrate salt in the diet without methemoglobin

De-fauna protozoa by oil is believed to affect the protozoa depletion population where methanogen attachment Although the mechanism of action is poorly understood, it may be related to the lipophilic nature of compounds such as anethol which facilitates permeation of essential oil across the protozoal membrane (Cardozo et al., 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 with cholesterol in the protozoal cell membrane to cause the destruction of the cell membrane, cell lysis and death (Francis et al., 2002) In the case of tannins, reported results 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 of hydrolyzable and condensed tannins exhibits higher antiprotozoal activity than hydrolyzable tannins alone Although the mode of action of tannins on protozoa is not

clear, it might be like that observed on bacteria

Preston et al (2013) assumed that there is a correlation between lower soluble crude protein in fish meal with lower methane production when it is compared with groundnut meal being higher solube CP and higher methane production This author interpreted 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 effective electron sink It is thus possible that there might be some negative feedback of this rapid production of ammonia from dietary protein on the pathway of ammonia formation 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 CH4

production remarkably significantly decreased with increasing coconut oil supplementation in the diets (Nguyen Thi Kim Dong & Nguyen Van Thu, 2018) This result is consistent with the findings that CH4 production reduced in the diet

supplemented 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 a significant 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 but mitigates methane production in the rumen, improves the growth biochar is included at 1% 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 improved location for biofilm microbial consortia and that this would facilitate microbial activity, including oxidation of methane by methanotrophic organisms The idea that biochar could act as a functional site for improved biofilm formation is based on the large surface to weight ratio (>30m2/g and up to 500m2/g), creating opportunities for adsorption of both micro-organisms, nutrients and gases

Biocarbon pyrolyzed at high temperature in a manner that generates a very high surface area is called engineered or activated biocarbon and has been theorized to promote the formation of microbial biofilms in the rumen (Leng et al., 2012a, 2014), a process essential for ruminal feed digestion (McAllister et al., 1994) Further, biochar may 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 low fertility soil and adverse climatic conditions It is also a source of raw materials for starch processing and for the animal feed industry with high commercial value Cassava has been planted throughout the 7 agro-ecological zones of the country: The Red River Delta, the Northern Midlands and Mountains, the North Central Coast, South Central Coast, 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 of November 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 the field Based on the areas of cassava cultivation in 2017, the yield of cassava root was 20.5 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 estimated 6.15 tonnes of dry matter per hectare (Erdmann et al., 1993) The amount of cassava foliage produced was an estimated 8.6million tonnes per year in An Giang This was a large 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 is dominant (73%), the rest is other varieties (Nguyen Huu Hy et al., 2014) The popular cassava 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 bitter cassava Sweet cassavas are used as food consumption for human; bitter cassavas are used for industrial processing such as wheat flours, animal feed, etc In An Giang there were 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 correlated with 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 the content of HCN in cassava roots, it is divided into two groups of cassava varieties: sweet cassava 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) The sweet cassava is local breeds, low yield, small roots, fresh and cassava roots are used for human 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 are used 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 only basic 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 tolerable levels (Cooke 1983; Dufour 1988a) Other reports show cyanogenic glicosides concentration in the roots Sweet cassava has HCN concentrations below 100 mg HCN 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, depending upon their cyanide content The low HCN, or sweet cassava, has less than 50 ppm of cyanogenic equivalents, while the high-HCN, or bitter cassava has more than 100 ppm (Wilson and Dufour, 2002) The major difference between low- and high-CNP cultivars 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-CNP cassava (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 to the differences in variety (Gomez and Valdivieso, 1984; Simwambana et al., 1992), fertilizer (Molina and ElSharkawy, 1995), age at first cutting and interval between cuttings (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 last three 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 including variety, harvesting interval (Khang et al., 2005), difference fertility of soil, processing, and also climate, environmental conditions, such as drought (leading to an increase in cyanogenic 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 mg/kgDM Sources

Cassava Root 26.0 1.0 - 3.0 - - - Stupat et al (2006) Cassava Leaves - 18.6 - 20.7 20.7 - 28.5 2.86 - 4.36 489 -730 Hue et al (2012)

3.2.3 Using cassava foliage for goat production

Many studies have focused on cassava foliage as a feed for animals, especially for ruminants Fresh cassava foliage, cassava leaves, cassava hay; cassava foliage silage 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 supplementation improved total DM and N intake of cattle fed a basal diet of rice straw and para grass Maximum weight gain and N retention were achieved when 40% of total 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 animal performance Cassava foliage is also a good protein source for small ruminants Feeding cassava foliage (wilted, sun-dried or ensiled) to goats housed at night after day-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 goats resulted in improved growth performance (Ngo Tien Dung et al., 2005; Phengvichith et al., 2006) An additional benefit from feeding cassava foliage to goats is that the tannins appear 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 or medium 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 a component that significantly affects the digestion of food and the metabolism of rumen nutrients that is tannin and HCN These two substances will affect the ability to eat, and digestibility for animals, especially ruminants According to Sousa et al (2003), sheep and goats are considered to be highly susceptible to HCN toxification, and the tolerance level 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 as goat feed is limited

Cassava plant is a sources of protein and good energy for livestock feed, but using fresh cassava forage as a feed for ruminants can be a problem due to its fairly high 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 fresh leaves, with the variation being attributed to genetic, physiological and edaphic factors, and climate One of the more important differences between different varieties of cassava is in the content of HCN The cyanide levels in cassava depend on the variety