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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: Assoc Prof Dr Nguyen Xuan Ba Dr Dinh Van Dung 1streviewer: ………………………………… ………………………………… 2nd reviewer: ……………………………… …………………………………… 3rd reviewer: ……………………………… …………………………………… The dissertation will be defended at the Council of dissertation assessment of Hue University, 04 Le Loi Street, Hue city, at………….on……/…… /2019 Dissertation can be further referred at: National Library Center for Information and Library of Hue University of Agriculture and Forestry, Hue University List of abbreviations, symbols and equivalents ADF ATP BW BSP CP CT CNP CH4 CO2 DM EPG FW GHG EPS HT HCN LW N NDF SCFA TMR VFA WRC Acid detergent fiber Adenosine triphosphate Body weight Brewery spent grain Crude protein Condensed tannins Cyanogenic potential Methane Carbon dioxide Dry matter Eggs per gram Fresh weight Green house gas Self-produced polymeric substance Hydrolysable tannins Hydrogen cyanide Live weight Nitrogen Neutral ditergent fiber Short -chain fatty acid Total mix ration Volatile fatty acid Water retention capacity INTRODUCTION 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 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 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 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) 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 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 * = 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) Chemical analysis All samples of cassava forage and stems were analyzed for DM, CP and ash using procedures described by AOAC (1990) ADF and NDF were analyzed according to Van Soest and Robertson (1991) HCN and total tannin were analyzed according to ISO 6703-1:1984 (TCVN 6181:1996), AOAC 955.35 by AOAC (2016) Statistical analysis Data was collected, preliminary calculations performed and stored in the Microsoft Office spreadsheet EXCEL 2010 Data were analysed using General Linear Model (GML); the basic model for analysis of variance (ANOVA); the constants described as averages, the standard deviation was performed on the MINITAB statistical software 16 RESULTS AND DISCUSSION Cassava production Chemical composition of cassava Table 2.1 Chemical composition of cassava parts % DM Variety of cassava Bitter cassava Sweet cassava Bitter cassava Cassava stems Sweet cassava Notes: FW: fresh weight Cassava forage DM, % 26.8 21.7 31.5 24.5 CP NDF 13.4 13.8 4.9 6.1 49.4 47.0 66.1 65.8 Total tannin 4.6 3.1 1.6 1.3 HCN (mg/kg FW) 153 34.5 68.0 30.5 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 Proportion Bitter cassava Proportion Fresh cassava plant Hard stems Cassava forage Cassava stems Leaves + petiole DM cassava plant Hard stems Cassava forage Cassava stems Leaves + petiole CP of cassava forage in DM (tons/ha) (tons/ha) % (tons/ha) % 13.2 ± 3.6 26.2 ± 7.2 8.7 ± 2.4 17.5 ± 4.8 33.5 66.5 22.1 44.4 17.2 ± 4.5 14.7 ± 3.8 4.9 ± 1.3 9.8 ± 2.5 54.0 46.1 15.3 30.7 5.5 ± 1.5 5.7 ± 1.6 2.1 ± 0.5 3.6 ± 1.0 49.1 50.9 18.4 32.5 6.4 ± 1.6 3.9 ±1.0 1.2 ± 0.3 2.7 ± 0.76 62.1 37.9 11.3 26.6 0.79 ± 0.23 - 0.52 ± 0.15 - The fresh and dry weight proportion of cassava plant is shown in Table 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 Goat production Table 2.3 Farm size and purpose raising Tri Ton Tinh Bien Total percentag e% Items Farm size (Household) 1- 20 head/farm Purpose raising (Heads) Meat Breeding Total Numbe percentag Numbe percentag r e% r e% 14 27 19 23.3 45 31.7 15 40 8.3 25 66.7 691 62.9 1,163 95.1 408 1,099 37.1 60 1,223 4.9 19 42 59 15.8 35.0 49.2 1,85 468 79.8 20.2 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 Percentage Tinh Percentage Total Management Tri Ton ,% Bien ,% Intensive 31 51.7 35 58.3 66 Semi27 45.0 25 41.7 intensive 52 Extensive 3.33 0.00 Percentage ,% 55.0 43.3 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 Tri Ton Tinh Bien percentage, percentage, Items Household Household % % Feed Natural grass 60 100 60 100 Natural grass + Leaves (except CL) 15 6.67 Natural grass + by-products 28 46.7 36 60 Natural grass + cassava forage 6.67 3.33 Natural grass + Grass growing 13 21.7 13 21.7 Natural grass + Commercial concentrate Supplements Salt Rice bran Commercial Concentrate No supplement Note: CL: cassava leaves 10 8.33 15 31 25.0 15.0 8.3 51.7 23 11 21 38.3 18.3 8.33 35.0 CONCLUSIONS 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 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 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, to 10 months after planting, the forage production can be about 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), 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 al (2013) MATERIALS AND METHODS EXPERIMENT The treatments had five levels of urea (0, 1, 2, and 4%, DM basis) added to freshly chopped cassava stems; and five storage times (0, 2, 4, and weeks) Each treatment combination was replicated 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 then sealed After preservation for 0; 2; 4; and 8weeks samples of cassava stems 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 Experimental design Four “Bach Thao” goats (14 ± 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 (UCSWB) The design was a Latin square with four treatments and four periods, each lasting 15 days (ten days for adaptation and days for collection of faeces and urine) Between each period there was a period of 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 Sources of variation were treatments, animals, periods and error for experiment RESULTS AND DISCUSSION EXPERIMENT 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 cassava stems Storage time, weeks Urea (%) SEM p-value 6.14 aE 6.11dEF 6.06eF 5.63dG 5.18eH 0.014