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HUE UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRYLE THI THUY HANG UTILIZATION OF CASSAVA FORAGES FOR GOAT PRODUCTION IN AN GIANG PROVINCE, VIETNAM Specialization: Animal Sciences Co

HUE UNIVERSITY 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

SUMMARY OF DISERTATION IN ANIMAL SCIENCES

HUE-2019

This dissertation is completed at: University of Agriculture and Forestry, Hue University

Supervised by:

1 Assoc Prof Dr Nguyen Xuan Ba

2 Dr Dinh Van Dung

List of abbreviations, symbols and equivalents

EPS Self-produced polymeric substance

SCFA Short -chain fatty acid

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

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 THE OBJECTIVES

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 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 improvenutritive value, especially its digestibility

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

digestibility, N retention in goats fed urea treated cassava stems

- To determine levels of brewery grain that affect feed intake, digestibility 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 SIGNIFICANCE/INNOVATION OF THE DISSERTATION

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

- 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

CHAPTER 1: LITERATURE REVIEW

In this chapter, there are main points following (i) Goat and cassavaproduction in An Giang province; (ii) the use of available feed resources for goatproduction; (iii) introduction to some main local feed resources such as cassavaand their by-products and brewers’ grains and (iv) feed and feeding strategies formethane mitigation from goat production The literature review shows a potential

to use local feed resources for goat production for the two purposes of increasinganimal performance and reducing methane emission

CHAPTER 2: EVALUATION OF THE POTENTIAL OF CASSAVA FORAGE AS FEED FOR GOATS IN AN GIANG PROVINCE,

VIETNAM

INTRODUCTION

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 An Giang is in the tropical monsoon climate, with two distinct seasons: rainy season and dry season The rainy season is the least in February and the rainyseason is the highest in September The average humidity is 75-80% The basic climate is favorable for agricultural development Due to the topography, the land resources are divided into different types: alluvial soil, alkaline soil, mountainous land Hilly land is mainly distributed in two districts of Tri Ton and Tinh Bien, a small part of Thoai Son district (Ba The area) The total area of hilly land in An Giang is about 29,320 ha, accounting for 8.6% of the total land area of the

province So, the area of grazing land is limited, the grassland is also limited The cassava was planted in there, it is not so much (representing 0.5% of agricultural land) The production of cassava roots in this area was 28.7 tons/year It is

estimated that an amount of cassava foliage is produced 61 thousand tonnes The reason is difficulties in drying the straw or other roughage in the rainy season, but by- production is an underutilized resource for feeding livestock The purpose of planting cassava in this area is to harvest roots, cassava foliage is underutilized, being left to rot in the monsoon season (flooding season) and burned in the dry season Even with a small number of cattle in the province by 98,758 heads in

2017 (Statistic yearbook of An Giang, 2018) a sufficient supply of roughage is not easy to find during the rainy season, and cassava foliage is an underutilized

resource for feeding livestock, especially in the hilly land area These areas are suitable for goats raising The design of this thesis responds to tendencies that havebeen observed in the development of crop and livestock systems in Tinh Bien and Tri Ton districts in An Giang province The survey described in showed that there

is an increasing tendency to plant cassava both as a food crop and as a source of starch for industrial processing At the same time, there are major trends in

ruminant livestock numbers, with the population of goats increasing

MATERIALS AND METHODS

The following indicators were used in the investigation of the survey

From secondary data:

- Planting area and cassava productivity in each district in the An Giang province

- Number of goats raised in each district in the An Giang province

The following indicators were used to select 120 households (60 households have grown cassava; 60 households have raised goats)

Data collection and calculation

In each district, we chose five households (from 60 selected households) with cassava cultivators at eight months after growing and an area of 1000 m2/plot

to collection and calculation of fresh cassava forage productivity Five positions were selected in each plot of land by diagonal method Land area of each position was 4m2 (Total area was 4 * 5 = 20m2) In each position, all cassava plant was cut and weighed (except root) Cassava plants were the whole plant above the soil Cassava plant was divided into two parts: Cassava forage – which were two thirds

of the above ground part of cassava plant; weighed the cassava forage (1); and hardstems (blue line on the right in figure 2.1) - which was one third above soil level, weighted them (2)

In this case, cassava forage was divided into two parts: (3) Tenderstems + (4) leaves (including peiole)

Tenderstems were called cassava stems (3)

Weight of cassva plant = (1) + (2)

Weight of cassva forage (1) = (3) + (4)

Chemical analysis

All samples of cassava forage and stems were analyzed for DM, CP and ash usingprocedures described by AOAC (1990) ADF and NDF were analyzed according toVan Soest and Robertson (1991) HCN and total tannin were analyzed according toISO 6703-1:1984 (TCVN 6181:1996), AOAC 955.35 by AOAC (2016)

Statistical analysis

Data was collected, preliminary calculations performed and stored in the MicrosoftOffice spreadsheet EXCEL 2010 Data were analysed using General Linear Model

(GML); the basic model for analysis of variance (ANOVA); the constantsdescribed as averages, the standard deviation was performed on the MINITABstatistical software 16

RESULTS AND DISCUSSION

Cassava production

Chemical composition of cassava

Table 2.1 Chemical composition of cassava parts

Variety of cassava DM, %

% DM

HCN (mg/kg FW)

CP NDF tannin Total Cassava forage Bitter cassava 26.8 13.4 49.4 4.6 153

Cassava stems Sweet cassavaBitter cassava 31.524.5 4.96.1 66.165.8 1.61.3 68.030.5

Notes: FW: fresh weight

DM: Dry matter, CP: crude proetin, NDF: neutral detergent fiber, HCN: Hydrogen cyanide

Table 2.2 Yield of cassava proportion with different variety

Sweet cassava (tons/ha)

Proportion

%

Bitter cassava (tons/ha)

Proportion % Fresh cassava plant

Goat production

Table 2.3 Farm size and purpose raising

Tri Ton Tinh Bien Total percentag

e % Numbe

r

percentag

e %

Numbe r

Table 2.4 Goat production systems in Tri Ton and Tinh Bien district

Number of farms in district

Total Percentage , % Management Tri Ton Percentage , % Tinh Bien Percentage , %

Table 2.5 Feed and feeding systems for goats in Tri Ton and Tinh Bien district

Tri Ton Tinh Bien Items Household percentage,

% Household

percentage,

% Feed

Natural grass + Commercial

In An Giang province, goat production is developing with promising

conditions of abundant feed resources, good government policies However, some constraints for production development such as low breed quality, lack of large farms and improving nutrient of feed for year-round Besides that, cassava forage has potential in An Giang The average dry matter cassava forages were 5 tons/ha

in 2017 They can be used as a protein source, as a replacement for grass for

ruminants but farmers did not use it because it is high HCN content How to use and preserve cassava (including the stems) as feed ruminants and against toxicosis

by reducing HCN content

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

INTRODUCTION

Cassava (Manihot esculenta Crantz) is a perennial woody shrub of thefamily Euphorbiaceae The forage can be used as a supplement for animals ineither fresh or wilted form or as hay (Phengvichith and Ledin, 2007; Wanapat etal., 1997) At root harvest, 9 to 10 months after planting, the forage production can

be about 5 tonnes dry matter/ha (Mui, 1994) It is estimated that more than 2.5milion tonnes of cassava forage are produced in Vietnam, of which about 15,000tonnes are in An Giang, Cassava forage is usually thrown away after harvesting theroot, because of its content of cyanogenic glucoside, mainly linamarin andlotaustralin (Alan and John, 1993)

Since the use of urea (CO(NH2)2 for straw treatment has been widelystudied and proved to be effective in the Tropics (Schiere and Ibrahim, 1989;Chenost and Kayouli, 1997; Trach et al., 2001; ThuyHang el at., 2005), 3 or 4%urea – treated straw viewed as a positive control together with untreated straw

being the negative control in the present studies to evaluate other treatments.According to Thanh et al (2013), cassava stems contain 33% DM but only 5.5%crude protein (CP) in the DM It was therefore hypothesized that there could be adouble benefit from ensiling the cassava stems with urea: (i) to provide theammonia needed by rumen organisms; and (ii) to improve the digestibility of thestems DM as has been widely proven in the urea-ensiling of low-protein, fibrousfeeds such as rice straw (Trach et al., 1998) Major advances have been maderecently in the integrated use of the cassava plant as a means of intensifying forruminant livestock production With this background, the specific objectives were

to determine the level of urea treated cassava stems that would facilitate the storageand at the same time improve its digestibility Then, determining the synergisticeffect of biochar and water spinach on growth of goat fed urea treated cassavastems, shown to be a potential feed resource for goat by Thanh et al (2013)

MATERIALS AND METHODS

EXPERIMENT 1

The treatments had five levels of urea (0, 1, 2, 3 and 4%, DM basis) added tofreshly chopped cassava stems; and five storage times (0, 2, 4, 6 and 8 weeks) Each treatment combination was replicated 4 times Two tonnes of cassava stems were collected from farmers’ fields directly after root harvesting; and chopped by hand Representative amounts were analyzed for DM by infrared radiation

(Undersander et al., 1993) prior to hand mixing 20 kg quantities with the indicated amounts of crystalline urea followed by storage in polyethylene bags which were

treated with urea were taken for evaluation of physical appearance characteristics, measurement of pH, chemical composition and in a comparative study on DM degradation with untreated cassava stems

EXPERIMENT 2

Experimental design

Four “Bach Thao” goats (14 ± 2 kg) were fed urea-treated cassava stemsalone (UCS) or with a supplement of water spinach at 1% of LW (DM basis)(UCSW), with biochar at 1% of DM intake (UCSB) or with 1% water spinach +1% biochar (UCSWB) The design was a Latin square with four treatments andfour periods, each lasting 15 days (ten days for adaptation and 5 days for collection

of faeces and urine) Between each period there was a period of 7 days for restingduring which time they were fed the diet destined for the subsequent period of theexperiment

Animals and management

The goats were housed in metabolism cages made from bamboo, designed tocollect separately faeces and urine They were weighed between 06:30 and 07:30h before feeding at the start and end of each experimental period

Feeding and management

The biochar was made by burning rice husks in a top-lit, updraft (TLUD)gasifier stove (Olivier 2010) The chosen amounts were offered twice daily introughs separate from the cassava stems and water spinach

Water spinach was chopped by hand prior to being put into the feed troughs Thechosen amounts were offered twice daily in troughs separate from the cassavastems

The cassava stems (no leaves) were harvested at 40-50cm above soil level atintervals of 150 days when it had attained a height of 100 - 120 cm The cassavastems were chopped by machine, mixed with urea (3% DM basis; no water wasadded) and ensiled in plastic bags after first extracting the air They were ensiledfor 21 days, after which they were fed ad libitum as the basal diet of the goats

Digestibility and N retention

During the data collection periods, the feces and urine were recorded twice daily at 7:00 and 16:00 and added to jars containing 100 ml of 10% sulphuric acid The pH was measured and, if necessary, more acid added to keep the pH below 4.0 After each collection period: (i) a sample of 10% of the urine was stored at -4o

C for analysis of nitrogen (AOAC 1990); (ii) the feces were mixed and a sample (10%) stored frozen at -20oC

Chemical analyses

The samples of CS, UCS, WS, and BG were analyzed for DM, ash, CP, NDFand ADF in feed offered and refused according to standard methods (AOAC, 1990) The feces were analyzed for DM and ash the urine and feces were analyzed for N according to AOAC, (1990) methods HCN content was determined

according to the standard methods of AOAC (2016) Total tannin content was determined according to the method (955.35) of AOAC (2016) Metabolizable energy of the diet (MJ/kg) were calculated from organic matter digestibility (OMD:

%) by formula of Mc Donald et al (2002) The formula is: ME = 0.160*OMD The rumen fluid was analyzed for the pH and NH3

Statistical analyses

Data were analyzed with the General Linear Model option of the ANOVA program in the MINITAB software (Minitab 2016) Sources of variation were