Sử dụng cây khoai mì (sắn) để phát triển chăn nuôi dê ở an giang, việt nam (tt)

- 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 int

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-2020

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 ADF Acid detergent fiber

ATP Adenosine triphosphate

GHG Green house gas

EPS Self-produced polymeric substance

NDF Neutral ditergent fiber

SCFA Short -chain fatty acid

TMR Total mix ration

WRC Water retention capacity

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

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 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 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 cassava production

in An Giang province; (ii) the use of available feed resources for goat production; (iii) introduction to some main local feed resources such as cassava and their by-products and brewers’ grains and (iv) feed and feeding strategies for methane mitigation from goat production The literature review shows a potential to use local feed resources for goat production for the two purposes of increasing animal 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 rainy season 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) Total area of hilly land in An Giang is about 29,320 ha, accounting for 8.6% of 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 ton/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 have been 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 hard stems (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)

RESULTS AND DISCUSSION

Cassava production

Chemical composition of cassava

Table 2.1 Chemical composition of cassava parts

Variety of cassava DM, %

(mg/kg FW)

CP NDF Total

tannin Cassava forage Bitter cassava 26.8 13.4 49.4 4.6 153

Sweet cassava 21.7 13.8 47.0 3.1 34.5

Cassava stems Bitter cassava 31.5 4.9 66.1 1.6 68.0

Sweet cassava 24.5 6.1 65.8 1.3 30.5

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)

Proporti

on %

Bitter cassava (tons/ha)

Proporti

on % Fresh cassava plant

Hard stems 13.2 ± 3.6 33.5 17.2 ± 4.5 54.0 Cassava forage 26.2 ± 7.2 66.5 14.7 ± 3.8 46.1 Cassava stems 8.7 ± 2.4 22.1 4.9 ± 1.3 15.3 Leaves + petiole 17.5 ± 4.8 44.4 9.8 ± 2.5 30.7

DM cassava plant

Hard stems 5.5 ± 1.5 49.1 6.4 ± 1.6 62.1 Cassava forage 5.7 ± 1.6 50.9 3.9 ±1.0 37.9 Cassava stems 2.1 ± 0.5 18.4 1.2 ± 0.3 11.3 Leaves + petiole 3.6 ± 1.0 32.5 2.7 ± 0.76 26.6

CP of cassava forage in

DM (tons/ha) 0.79 ± 0.23 - 0.52 ± 0.15 -

The fresh and dry weight proportion of cassava plant is shown in Table 2 The cassava forage was differences between two varieties of cassava The proportion of sweet cassava forage was higher than the bitter cassava These results were different due to the differences in variety, farming conditions, regions, soil, and fertilization and cutting time

Purpose raising

(Heads)

Meat 691 62.9 1,163 95.1 1,854 79.8 Breeding 408 37.1 60 4.9 468 20.2 Total 1,099 1,223

The purpose of raising goats here was mainly to sell meat at 79.8%, in addition

to raising goats with the purpose of selecting good ones in the herd to sell goats for local market, or neighbourhood; but account for a smaller percentage (20.6%) In addition, markets for goat production (eg: milk, cheese, ) are in the cities providing farmers with better income and opportunities for further development

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,

%

Intensive 31 51.7 35 58.3 66 55.0 Semi-intensive 27 45.0 25 41.7 52 43.3 Extensive 2 3.33 0 0.00 2 1.67 Intensive systems are the main method of goat raising in An Giang, this systems of complete confinement helps the farmers manage each individual, can detect disease or manage oestrus in a timely manner, but feed had to controled actively, while semi- intensive systems help goats have time to graze, develop the right features and reduce the reserve of feed

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

% Household

percentage,

% Feed

Natural grass 60 100 60 100 Natural grass + Leaves (except

Natural grass + by-products 28 46.7 36 60 Natural grass + cassava forage 4 6.67 2 3.33 Natural grass + Grass growing 13 21.7 13 21.7 Natural grass + Commercial

Supplements

Rice bran 9 15.0 11 18.3 Commercial Concentrate 5 8.3 5 8.33

2017 They can be used as a protein source, as a replacement for grass for ruminants but farmers did not use 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 the family Euphorbiaceae The forage can be used as a supplement for animals in either fresh or wilted form or as hay (Phengvichith and Ledin, 2007; Wanapat et al., 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 2.5 milion tonnes of cassava forage are produced in Vietnam, of which about 15,000 tonnes are in An Giang, Cassava forage is usually thrown away after harvesting the root, because of its content

of cyanogenic glucoside, mainly linamarin and lotaustralin (Alan and John, 1993)

Since the use of urea (CO(NH2)2 for straw treatment has been widely studied 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 a double benefit from ensiling the cassava stems with urea: (i) to provide the ammonia needed by rumen organisms; and (ii) to improve the digestibility of the stems DM as has been widely proven in the urea-ensiling of low-protein, fibrous feeds such as rice straw (Trach et al., 1998) Major advances have been made recently in the integrated use of the cassava plant as

a means of intensifying for ruminant livestock production With this background, the specific objectives were to determine the level of urea treated cassava stems that would facilitate the storage and at the same time improve its digestibility Then, determining the synergistic effect of biochar and water spinach on growth of goat fed urea treated cassava stems, shown to be a potential feed resource for goat by Thanh et

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 stems alone (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 (CSWB) The design was a Latin square with four treatments and four 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 resting during which time they

were fed the diet destined for the subsequent period of the experiment

Animals and management

The goats were housed in metabolism cages made from bamboo, designed to collect 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 in troughs separate from the cassava stems and water spinach

Water spinach was chopped by hand prior to being put into the feed troughs The chosen amounts were offered twice daily in troughs separate from the cassava stems

The cassava stems (no leaves) were harvested at 40-50cm above soil level at intervals of 150 days when it had attained a height of 100 - 120 cm The cassava stems were chopped by machine, mixed with urea (3% DM basis; no water was added) and ensiled in plastic bags after first extracting the air They were ensiled for

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, NDF and 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 levels

of urea, storage time, random error for experiment 1 Sources of variation were treatments, animals, periods and error for experiment 2

RESULTS AND DISCUSSION

EXPERIMENT 1

Hygienic quality of cassava stems treated by physical evaluation

The evaluation of the physical appearance of the treated cassava stems with respect to color, smell, and mold, the quality of treated cassava stems in the bags or bales were considered to be good, except in the treatments 1(no urea) Cassava stems in these treatments had no, or only a slight ammonia smell, and some fungi developed on the surface of the bags

Chemical compositions of cassava stems treated with difference levels of urea and stored times

The magnitude of the CP increase of treated cassava stems varies according to many factors such as material, environment and procedure of the treatment process Furthermore, the CP increases are related to the urea level in the treatment, the water content of material, and the temperature Variation of material CP concentration determines the magnitude of the increase, and higher increases were noted for cassava stems with low CP concentration after urea treatment

Table 3.1 Effect of urea level and storage time on crude protein in

SEM: standard error of mean

p- value: The level of statistical significance is different

The HCN content in cassava stems treated with 2% or higher urea level after 2 weeks storing was lower than 100mg/kg DM (from 95.3 to 98.8mg/kgDM), and lower than 50mg/kgDM after 4 weeks storing (35.6 – 43.4mg/kgDM) (Table 3.2) This means that the goat (20kg live weight) will eat 19.9 to 24.3mg of HCN (equivalent to 1-1.2mg / kg of LW), which is not yet enough to be toxic for goats The decrease in HCN with storage time may similarly be he result of the high pH (>7.00) following 2 weeks of storage with urea and would appear to be related to chemical reactions resulting in neutralization of the hydrocyanic acid by the ammonia

Table 3.2 Effect of urea level and storage time on HCN (mg/kgDM) content of cassava stems

SEM: standard error of mean

p- value: The level of statistical significance is different

EXPERIMENT 2

Chemical composition of diet ingredients

Table 3.3 Chemical composition of diet ingredients (UCS is

urea-treated cassava stems) in experiment 2

Notes: nd: Not determined; WRC: Water retention capacity

CS: cassava stems; UCS: urea treated cassava stems

DM: Dry matter CP: Crude protein; ADF: Acid detergent fiber; NDF: Neutral detergent fiber, OM: Organic matter

Feed intake

Increasing intake of diet DM, and especially of the dietary concentration of crude protein, with resultant improvements in N retention All these effects appear to have been caused by the increased crude protein content of the diet when the water spinach was fed (13.0 versus 9.4% in the DM) When the N retention data were corrected for differences in N intake the effects of the water spinach were no longer apparent

Table 3.4 Effect of biochar and water spinach on feed intake

Unit (gDM/day) Treatment SEM p- value

UCS 367a 428a 300b 352ab 15.10 0.002 Biochar 0 3.84 0 3.91 0.450 <0.001 Water spinach 0 0 159 163 3.306 <0.001 Total DM intake 367b 432ab 459ab 519a 19.97 0.009 DMI, % LW 2.27d 2.59c 2.83b 3.12a 0.048 <0.001 OMI (gDM/day) 337c 391bc 428ab 488a 15.04 <0.001

CP in DM, % 11.4b 11.6b 14.05a 14.07a 0.512 0.003

ME (MJ/kgDM) 4.00 4.35 4.12 4.47 0.207 0.376

(p<0.05)

UCS: urea treated cassava stems; UCSB: UCS with biochar; UCSW: UCS

with water spinach; UCSWB: UCS with water spinach and biochar

SEM: standard error of the mean

p- value: The level of statistical significance is different

Biochar increased daily N retention by 46% on the diet of urea-treated cassava stems and by 21% when water spinach replaced half of the urea-treated cassava stems (Table 11) Comparable values for the increases in biological value of the protein were 12 and 4%

Table 3.5 Nutrient digestibility (%) and nitrogen balance in goats fed urea-treated cassava stems supplemented with or without fresh water spinach and biochar

Nutrient digestibility (%)

Dry matter 59.4b 64.8a 60.8b 66.3a 0.88 0.001 Crude protein 53.2b 60.1ab 61.7ab 63.1a 1.54 0.010 Organic matter 59.4 65.0 61.6 66.8 1.78 0.066

N balance, g/d

Intake 8.13c 9.36bc 12.4ab 13.0a 0.782 0.001 Feces 3.79bc 3.65c 5.09a 4.81ab 0.245 0.003 Urine 1.30 1.17 1.42 1.25 0.217 0.874

Nitrogen retention

(g/day) 3.03b 4.42ab 5.84a 6.91a 0.607 0.004 % of N intake 37.4b 47.3ab 46.9ab 52.9a 2.55 0.008 % of N digested 69.9c 78.6b 80.0ab 84.3a 1.390 <0.001

Notes: a,b,c Mean values with the different letters in the same rows are significantly different

at the level of P≤0.05

UCS: urea treated cassava stems; UCSB: UCS with biochar; UCSW: UCS with water spinach

CONCLUSIONS

Supplementation with 1% of biochar and 1% water spinach to a diet of treated cassava stems, increased the DM intake by 41% , the apparent dry matter (DM) digestibility and nitrogen (N) retention in goats Biochar increased daily N retention by 46% and the biological value of the absorbed N by 12%

urea-CHAPTER 4: EFFECT OF DIFFERENT LEVELS OF BREWERS’ GRAINS SUPLEMENTATION ON PERFORMANCE AND METHANE EMISSION OF

GOATS FED CASSAVA FORAGE

INTRODUCTION

Cassava (Manihot esculenta Crantz) is a major crop in Vietnam, grown on 570,000 ha producing annually some 1 million tonnes of roots (GSO, 2016) The roots are used mainly for manufacture of starch and as an ingredient in livestock feed Growing the crop as a semi-perennial forage with repeated harvesting at 2 to 3month intervals is a recent development (Wanapat 1997; Preston and Rodriguez, 2004) Several reports have shown the benefits of the fresh forage as a source of bypass protein in ruminant diets based on molasses-urea (Ffoulkes and Preston, 1978), rice straw (Do et al., 2002; fresh cassava stems (Trinh Xuan Thanh et al., 2013) and ensiled cassava pulp-urea (Keopaseuth et al., 2017; Binh et al., 2017) The use of fresh cassava forage as the sole diet of goats was pioneered by Sina et al., 2017 Growth rates on a diet of fresh cassava forage were 65 g/day and were more than doubled to 160 g/day when a small supplement (5%) of ensiled brewers’ grains was included in the diet, It was proposed that this “synergistic” effect of the brewers’ grains was due to its role as a source of beta-glucan, a component of the cell walls of cereal grains and fungi such as yeasts, that has been shown to have prebiotic properties (Novak and Vetvicka 2008).The present experiment was designed to provide further evidence for the prebiotic effect of brewers’ grains in a basal diet of cassava forage fed to growing goats Proportions of ensiled brewers’ grains above (6%) and below (2%) the 4% level were compared to identify the optimum level

MATERIALS AND METHODS

Experimental design

Four “Bach Thao” goats (14 ± 2 kg) were fed the 4 levels if ensiled brewers’ grains (0, 2, 4 and 6% DM basis) as the only supplement to a diet of ad libitum fresh cassava forage (sweet variety) The design was a Latin square with four treatments and four periods, each lasting 15 days

Animals and management

The goats were housed in metabolism cages made from bamboo, designed to collect separately feces and urine They were vaccinated against Pasteurellosis and Foot and Mouth disease and treated with Ivermectin (1ml/10 kg live weight) to control internal and external parasites They were weighed between 06:30 and 07:30h before feeding at the start and end of each experimental period

Feeds and feeding

The cassava forage was harvested 50-60cm above soil level at intervals of 120 days when it had attained a height of 100 - 120 cm Harvesting of the cassava was done 2h prior to each feed, morning and afternoon The forage was chopped by hand prior to being put into the feed troughs The brewers’ grains were stored in closed plastic bags for every 5 days The chosen amounts were offered twice daily in troughs separate from the cassava forage Feed refusals were weighed every morning prior to

giving the new feed Samples of each diet component were collected daily and bulked

at the end of each period for analysis

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

Rumen parameters

Rumen fluid was taken by stomach tube 3h after the morning feed following the last day of each collection period During this time the goats were still on the designated diet for that period

Rumen gas emissions

At the end of each period the goats were confined individually in a gas-proof chamber (a bamboo frame covered with polyethylene plastic) for sampling of eructed gases and residual air in the chamber Measurements of the concentrations of methane and carbon dioxide were taken continuously over a 10-minute period, using

a Gasmet infra-red meter (GASMET 4030; Gasmet Technologies Oy, Pulttitie 8A, FI-00880 Helsinki, Finland)

Analytical procedures

All of samples of feeds offered and refused, and of the feces, were analysed for

DM and Ash by AOAC (1990) methods NDF and ADF were analyzed according to the procedure of Van Soest and Robertson (1991) Nitrogen in urine and ammonia in rumen fluid were determined by the Kjeldahl method (AOAC 1990) Metabolizable energy (ME) 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

Statistical analysis

Data were analyzed with the General Linear Model option of the ANOVA program in the MINITAB software (Minitab 2016) Sources of variation were treatments, animals, periods and error

RESULTS AND DISCUSSION

Chemical composition

The crude protein (CP) of the cassava forage (leaf and petiole combined) was considerably lower than the value of 21% CP in DM reported by Sina et al., 2017 where the leaf alone had 29% CP in DM and the petiole 9.6% in DM

Table 4.1 Composition of diet ingredients

Notes: DM: Dry matter, CP: cruduce protein, NDF: Neutral

Detergent fiber; ADF: Acid detergent fiber

Feed intake and digestibility

Increasing the proportion of cassava forage DM fed to goats from 0 to 47% of total DM feed offered resulted in increased DM intake (DMI), organic matter (OM) digestibility and nitrogen retention In the present results, metabolizable energy was increased by the level of brewers’ grains in the diet The level of CP in the treatment

3 was 7,5g CP/kg LW/day with the ME intake and daily gain of 3.80 MJ/day and 142g, respectively (Table 4.2)

Table 4.2 Feed intake in goats fed cassava forage supplemented with different levels

% of DM intake

Brewers’ grains 0.00 2.15 3.97 6.16 0.05 <0.001 Crude protein 12.9 14.0 13.5 14.6 0.54 0.192

Table 4.3 Nutrient digestibility (%) in goats fed cassava forage supplemented

with different levels of brewers’ grains

CP 62.4a 69.9b 72.7b 70.8b 1.66 0.021

DM 55.9a 67.2b 70.8b 65.5b 2.7 0.036

OM 53.0a 58.2b 66.0c 56.6ab 1.05 0.001 NDF 57.8 67.4 70.6 63.0 4.34 0.248

Notes: CP: crude protein; DM: dry matter; OM: organic matter, NDF: neutral

detergent fiber; BG0, BG2; BG4; BG6: Treatments supplemented brewers’grain levels of 0, 2, 4, 6% (DM basic)

abc Mean values with the different letters in the same rows are significantly different

at the level of P≤0.05

Nitrogen retention

The effect of adding 4% brewers’ grains to the diet was a 65% increase in N retention and a 14% increase in N retained per unit of N digested

Table 4.4: N balance (g/day) in goats fed cassava forage supplemented

with different levels of brewers’ grain

The mechanism by which small quantities of brewers’ grain (4% of diet DM) bring about these positive effects, benefitting animal performance, but increasing ratio

of methane and carbon dioxide is still to be identified Here we suggest the idea that substances in brewery grains (perhaps β-glucan or related compounds) support biofilm formation which in turn increases the efficiency of microbial growth (Leng, 2014)

Table 4.5 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

CHAPTER 5: EFFECT OF BIOCHAR SUPPLEMENTATION LEVELS ON GROWTH AND METHANE EMISSIONS OF GOATS FED FRESH

CASSAVA FORAGE

INTRODUCTION

The population of goats in An Giang in 2017 was 6 times higher than in 2012 (Statistic yearbook of An Giang 2017) The relative price of meat from goats is higher than that from cattle, eg: price of goat meat 3.2 USD/kg LW compared to cattle (2.5 USD/kg LW) (Do Thi Thanh Van et al., 2018) Most goats are kept in confinement in small scale systems with the feed supplied from around the household

or close by (eg: natural grasses, water spinach, sweet potato leaves…but not cassava forage, that is traditionally thrown away, or burned, causing environment pollution)

source of protein for feeding to many kinds of animals Brewers’ grains are the solid residue left after the distillation of germinated cereal grains to produce beer and other alcoholic beverages The recent reports of benefits in growth and health of cattle and goats fed small quantities of brewers’ grains (Thuy Hang et al 2018; Silivong et al 2018; Binh et al 2017) are believed to be related to their “prebiotic” qualities in enhancing the action of beneficial microbial communities along the digestive tract of the animal (Inthapanya et al 2019) Biochar is generated from the partial combustion

or fibrous biomass, and although primarily used as a soil amendment (Lehmann and Joseph 2009; Preston 2015), it has recently been reported that at a level of 1% of the diet DM enhanced the growth rate and reduced enteric methane emissions of cattle (Leng et al 2012) and goats (Binh et al 2018; Silivong et al 2018)

The hypothesis underlying the research reported in this paper was that growth rate and methane emissions of goats would reflect a dose response relationship to biochar, which merited the study of levels of biochar in the range of 0 to 1.5% in diet DM

MATERIALS AND METHODS

Experimental design

Twelve growing male goats of the Bach Thao breed, with an initial body weight 16 ± 1 kg and about 3.5 – 4.5 months of age, were housed in individual cages (Figure1) and given a basal diet of fresh cassava forage ad libitum plus 4% (DM basis) of ensiled brewers’ grain Treatments were 4 levels of biochar: 0, 0.5, 1.0 and 1.5% of diet DM The design was a randomized completely block design with three replicates of the four treatments The trial was for 12 weeks after a period of 15 days

to accustom the goats to the diets

Feeding and management

The Cassava forage (leaves, petioles and stems) were harvested at 60 days intervals The cassava forage was fed to animals 2- 3 hours after harvesting Harvesting was by hand-cutting the cassava stems at ground level then rejecting the lower 50cm of “hard” stems The brewers’ grains were brought from the brewery in Kien Giang Province every 10 days The biochar was produced by burning rice husks

in a top-lit, updraft (TLUD) gasifier stove (Olivier 2010) The animals had free access to clean water for drinking

Measurements

Live weight was recorded in the morning before feeding at the beginning and

at 10-day intervals until the end of the 90-day experiment Live weight gain was calculated from the linear regression of live weight (Y) on days from the start of the experiment (X)

Feed consumption was recorded by weighing feeds offered and refusals from individual animals every morning before offering new feed

Eructed gas emissions and analysis

At the end of the experiment the goats were confined individually in a closed chamber for sampling of eructed gases and residual air in the chamber (madsen et al., 2010) Measurements of the concentrations of methane and carbon dioxide were taken continuously over a 10-minute period, using a gasmet infra-red meter (gasmet 4030; gasmet technologies oy, pulttitie 8a, fi-00880 helsinki, finland)

Statistical analysis

Data were analyzed with the general linear model option of the anova program

in the MINITAB software (Minitab 2016) Sources of variation were treatments and error Production responses (feed intake, live weight gain and feed conversion) were related to percent biochar in the diet using polynomial regression equations from Microsoft Office Excel software

RESULTS AND DISCUSSION

Composition of diet ingredients

Two batches of biochar were used in the experiment The first batch, which was fed during the 15-day adaptation period and the first 10 days of the growth trial had a water retention capacity of 3.81 ml water/g dry biochar The second batch which was fed from day 10 of the feeding trial to the end after 90 days had a much higher water retention capacity of 4.89

Table 5.1 Composition of diet ingredients

Notes: DM: Dry matter, CP: Crude protein; ADF: Acid detergent fiber; NDF:

Neutral detergent fiber; HCN: Hydrogen cyanic acid; WRC: Water retention capacity

Feed intake

For all the growth criteria expected to be influenced by nutrient manipulation

of ruminant diets the responses were curvilinear with positive effects from increasing biochar supplementation from 0 to 0.86% of the diet DM followed by a decline as the biochar level was raised to 1.3% in diet DM

Table 5.2 Feed intake in goats fed increasing levels of biochar in a diet of

fresh cassava forage

Notes: B0; B0.5; B1.0; B1.5: Treatments supplemented biochar levels of

0;0.5; 1.0; 1.5 (% in diet DM)

SEM: Standard error of the mean

Growth and feed conversion

Biochar is not a nutrition source for the animals, but it will be an additive effect on reduction of methane emissions from adding both biochar (increasing the potential microbial habit) and nitrate to the diet of cattle fed a base diet of fresh cassava root chips supplemented with fresh cassava leaves (Leng et al., 2012)

Table 5.3 Live weight and feed conversion in goats fed increasing

levels of biochar in a diet of fresh cassava forage

The ratio of methane and carbon dioxide in eructed gases from goats fed

cassava forage supplemented with different level of biochar

The ratio of methane and carbon dioxide was the effect on the rumen

fermentation the improvement (decrease in methane production) was decreased linear

in goats fed increasing levels of biochar in a diet of fresh cassava forage

Table 5.4: The ratio methane: carbon dioxide in eructed gases

from goats fed cassava forage supplemented with biochar

GENERAL CONCLUSIONS

The positive effects of storing (ensiling) the cassava stems with addition of urea are the reduction in HCN levels and the possible synthesis of protein from the ammonia derived from the urea and the fermentation of part of the carbohydrate in the cassava stems Urea treatment of the cassava stems (with 3% in DM) increased the crude protein from 5.5 to 11.7% in DM and can be preserved up to 8 weeks

Cassava stems treated with 3% urea in DM improves nutrietive value and DM intake up to 18% by supplementing with biochar Addition of water spinach increased total DM intake by 25% while the combined effect of biochar plus water spinach was

to increase intake by 41% Biochar increased daily N retention by 46% and the biological value of the absorbed N by 12% Biochar provides no protein to the diet, thus it is postulated that the increase in N retained and in its biological value came about as a result of the biochar stimulating rumen microbialgrowth resulting in an increase in synthesis and hence of absorption of amino acids

Adding 4% of brewers’ grains to a diet of cassava forage increased the DM intake, the apparent DM digestibility, the N retention and the biological value of the absorbed nitrogenous compounds The benefits of such small quantities of brewers’ grains are believed to be related to their “prebiotic” qualities in enhancing the action

of beneficial microbial communities along the digestive tract of the animal

Feed intake, live weight gain and feed conversion were improved by increasing biochar supplementation from 0 to 0.8% of the diet DM followed by a decline as the biochar level was raised to 1.3% in diet DM Rumen methane emissions were reduced with a linear trend as the level of biochar in the diet was increased

PUBLICATION LIST

This thesis is based on the work contained in the following papers:

Paper 1: Digestibility, nitrogen balance and methane emissions in goats fed

cassava forage and restricted levels of brewers’ grains Livestock Research for Rural Development Volume 30, Article #68 from

http://www.lrrd.org/lrrd30/4/thuy30068.html

Paper 2: Effect of biochar and water spinach on feed intake, digestibility and

N-retention in goats fed urea-treated cassava stems Livestock Research for Rural Development Volume 30, Article #93 from

http://www.lrrd.org/lrrd30/5/thuyh30093.html

Paper 3: Effect of biochar on growth and methane emissions of goats fed fresh

cassava forage Livestock Research for Rural Development Volume 31, Article #67

from http://www.lrrd.org/lrrd31/5/thuyhang31067.html

Paper 4: Effect on nutritive value of cassava (Manihot esculenta Crantz) stems

of ensiling them with urea Livestock Research for Rural Development Volume 31, Article #92 from http://www.lrrd.org/lrrd31/6/thuyh31092.html