HUE UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY LE THUY BINH PHUONG SYNERGIC EFFECT OF CASSAVA (MANIHOT ESCULENTA CRANTZ) FOLIAGE, BREWER’S GRAINS, AND BIOCHAR ON METHANE PRODUCTION AND PERFORMANCE OF RUMINANTS 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: Assoc Prof Dr Nguyen Huu Van Dr Dinh Van Dung 1streviewer: ………………………………… ………………………………………………… 2ndreviewer: ……………………………… …………………………………………………… 3rdreviewer: ……………………………… …………………………………………………… The dissertation will be defended at the Council of dissertation assessment of Hue University, 04 Le Loi Street, Hue city, at……………….…….on……/…… /2020 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 ADG Average daily gain BG Brewers’ grain CP Crude protein CFU Colony-forming unit DM Dry matter DMI Dry matter intake HCN Hydrocyanic acid GE Gross energy LW Live weight N Nitrogen NDF Neutral detergent fiber NPN Non-protein nitrogen SEM VFA Standard error mean Volatile fatty acid INTRODUCTION Problem statement Cassava is perspective plant to climate change adaptation; its pests and its diseases resistance and greater drought tolerance is a major factor in ranking cassava in the food security of the world (Jarvis et al 2012) In Vietnam, cassava is second crop, is grown mainly in both at the household and small-scale processor level (Hoang Kim et al 2000) From the successful experiment in utilization of cassava foliage (sweet variety) as protein source on cattle which was originally reported by Ffoulkes and Preston (1978), and then have been successfully fed as fresh state to goat and cattle in Cambodia (See report of Preston and Rodríguez Lylian, 2004), that make cassava foliage become important plant protein source in ruminant diet Nevertheless, cyanide toxin in fresh cassava foliage, especially bitter cassava foliage, is the main obstacle for animal such as restricting the consumption intake of ruminant or causing poisoning when they consume rapidly Nowadays, as the quantity of bitter cassava (high cyanide content) predominate over sweet cassava (lower cyanide content) on the field, looking for feeding method of bitter cassava foliage diet with minimizing negative effect of cyanide toxin will match reality more but will a challenge Many studies are beginning to be interested in cyanide toxic that has certain effect on methanogenic bacteria population by inhibited methanogenesis activity lead to diminish methane production (Ch Olga Rojas et al 1999; Phuong et al 2012; Phanthavong et al 2015) However, whether cyanide may affect overall microbial activity and impact the rate of rumen fermentation indirectly, it is still not fully understood Previously, the knowledge of ruminant nutritionists focused on rumen, but the impact of cyanide on rumen fermentation may profoundly influence lower digestive physiology of ruminant and must be considered to fully understand when utilizing bitter cassava foliage in diet Even so, the challenge of bitter cassava foliage diet (high cyanide content) is a new approach but must require the safety for animal's health Therefore, building suitable feeding method for fresh cassava foliage diet, particularly bitter cassava foliage, without causing cyanide toxin is needed to utilize cassava foliage more effectively in the ruminant feeding system The objectives The aim of this thesis was to develop a greater understanding of both the constraints and benefits of using cassava foliage in ruminant feeding systems From these things can improve the utilization of cassava foliage in ruminant feeding by enhancing its properties as a source of bypass protein and verify the role of HCN toxin in cassava foliage on the reduction of methane production that was built on earlier findings The following objectives are required to accomplish the aim of this research: i Determining the trend influences of HCN concentration in cassava foliage on the characteristic of in vitro rumen fermentation such as gas and methane production, ammonia concentration ii iii Building feeding method of “bitter” cassava foliage (KM 94 variety; moderate HCN content) diet by added 4% brewers’ grain (of DM) and/or 1% biochar (as DM), then evaluating the effects of this feeding method on growth, digestibility/N retention, excretion of thiocyanate in urine and methane production of cattle and goat Considering the benefit of brewers’ grain to “bitter” cassava foliage (KM94) diet by examining Saccharomyces and acid lactic bacteria in fresh brewers’ grain and compare it with potential fermented cassava pulp on gas and methane production of ruminal in vitro incubation Significance/innovation of the dissertation This dissertation successfully demonstrated that HCN in cassava foliage is main factor for reduction of methane production while the earlier finding could only use it as prediction for decreased methane Currently, the best-known cassava foliage to feed animal is “sweet” cassava foliage with low cyanide content, my dissertation succeeds to build feeding method for “bitter” cassava foliage diet (higher cyanide content) with support of adding restricted brewers grain (4% of DM) and biochar (1% of DM) to feed cattle and goats without cause HCN toxicity Additionally, discovery of the feeding of the bitter cassava foliage appear to modify the rumen fermentation lead to increases in nitrogen retention associated with reduced methane production, it made a part of this dissertation provided the implication for new approach of the proposed partial shift in sites of digestion (from rumen to small intestine and the cecal-colon region) that previously it is thought that only rumen fermentation have a truly symbiotic relationship with the ruminant ©©©©© CHAPTER 1: LITERATURE REVIEW The literature review consists of the key issue on: (i) Process of rumen fermentation that related to methane production and direct its effect on the growth of ruminant Interpreting interaction of ruminal microorganism is possible detoxification strategies in context of using cassava foliage that contain high HCN content (ii) The utilization of some by-products in ruminant feeding such as: (i) cassava foliage varieties as a protein source implied that HCN content as inhibition of methanogenesis, and (ii) restricted brewer grain and biochar as additives that it is thought cyanide detoxification in cassava foliage diet; (iii) the role of Saccharomyces in brewer’s grain was expected as “prebiotic” to support cassava foliage diet All above issues were placed in integrative review via the description, interpretation of prior research and reveal gap in literature ©©©©© CHAPTER THE EFFECT OF SUPPLEMENTATION WITH “BITTER” OR “SWEET” VARIETIES ON METHANE PRODUCTION IN AN IN VITRO INCUBATION Introduction Recent industrial development of cassava root processing for extraction of starch released source of abundant cassava pulp Cassava pulp and other by-products of cassava such as leaves, and stalk have potential feeding value for livestock Cassava by-product needs to be utilized in ruminant’s feeding system is cassava pulp, due to its negative fermentation impact lead to polluted environment The pulp is very low in protein; however, the foliage is high in CP with content of more than 20% in DM (Lukuyu et al 2014) It was reported by Ffoulkes and Preston (1978) that fresh cassava foliage could replace soybean meal as the only protein source in a fattening diet for cattle based on ad libitum molasses-urea Preston and Leng (2009) postulated that part of the cassava leaf protein had “rumen-escape” characteristics which helped to balance the microbial protein produced from the rumen fermentation of molasses supplemented with urea Cassava products contain cyanogenic glucosides which liberate hydrocyanic acid (HCN) when enzymatically degraded Cyanogenic glucosides exist as linamarin and lotaustralin in unbruised leaf (Nartey 1968) When the cellular structure is broken, the glucoside is exposed to extracellular enzymes such as linamarase which gives rise to toxic hydrocyanic acid In studies on bio-digestion of cassava residues it was shown that the HCN liberated in the digestion process was toxic to methanogenic bacteria (Smith et al 1985; Rojas et al 1999) It is therefore postulated that a similar process could take place in the rumen of cattle fed cassava products, which could be an advantage as a strategy for reducing greenhouse gas emissions from ruminant animals Cassava varieties are generally categorized into “sweet” varieties suitable for human consumption, and “bitter” varieties more appropriately used for industrial production of starch It is understood that the ‘bitter” varieties are so-called because they have higher concentrations of cyanogenic glucosides making them potentially toxic to humans and animals Establishing a feeding system from cassava by-product is limited the available information on its effectiveness and the impact of different level of HCN concentration in cassava foliage varieties on reduced methane production is not clear Therefore, the hypothesis of this study was to test that methane production in an in vitro rumen fermentation would be reduced when urea-supplemented cassava root pulp was incubated with the leaves from bitter, rather than sweet, varieties of cassava Materials and methods Experimental design The four treatments in a completely randomized design (CRD) were the leaves of a “sweet” variety of cassava (Gon) and leaves from three bitter varieties (Japan, KM94 and KM 140-1) with four replications The substrates were cassava pulp and urea (Table 1) The leaves were added to provide an overall level of 12.8% crude protein in substrate DM Table 2.1 Composition of the substrates Gon Japan DM basis, % Cassava pulp 73.1 73.1 Cassava leaves 25 25 Urea 1.8 1.8 Fresh basis, g Cassava pulp 10.4 10.4 Cassava leaves 12.3 9.8 Urea 0.216 0.216 KM94 KM 140-1 73.1 25 1.8 73.1 25 1.8 10.4 12.2 0.216 10.4 13.5 0.216 A simple in vitro system was used based on the procedure reported by Inthapanya et al (2011) Material preparation The cassava leaves (without petioles) were selected at a point approximately one third of the height of the plant measured from the top They were stored in plastic bags to avoid loss of moisture In the laboratory, the fresh leaves were chopped into small pieces and then ground (1mm sieve) Dry cassava pulp was taken from the Wuson starch factory, Binh Phuoc Province The 12 grams of substrates (Table 2.1) were mixed with 0.24 liters of rumen fluid and followed by 0.96 liters of buffer solution (Table 2.2) This mixture was contained in the fermentation bottle, gassed with carbon dioxide, and incubated in a water bath at 38 °C for 24h Table 2.2 Ingredients in buffer solution Ingredient s CaCl2 NaHPO4.12H2O g/liter 0.04 9.3 Source: Tilley and Terry (1963) NaCl 0.47 KCl 0.57 MgSO4.7H2O 0.12 NaHCO3 9.8 Cysteine 0.25 Measurements The gas volume was measured by water displacement from the receiving bottle suspended in water The bottle was calibrated at intervals of 50ml The methane percentage in the gas was measured with a Crowcon meter (Crowcon Instruments Ltd, UK) The DM and crude protein contents of the substrates were determined according to AOAC (1990) methods Ammonia was analysed in the filtrate after separating the solids using a cloth filter HCN was determined by titration with AgNO after boiling the sample in KOH to concentrate the HCN Tannin was analyzed by the Lowenthal method consisting of boiling the leaves in 0.1N H 2SO4, adding indigo dye and titrating with potassium permanganate Statistical analysis The data were analysed with the general linear model (GLM) option in the ANOVA program of the Minitab software (Minitab 2000) Sources of variation were treatments, and error Results and discussion Chemical composition of the substrate The cassava leaves contained a high level of crude protein (27.5-31.8% CP in DM); the cassava pulp had less than 3% CP in DM (Table 2.3) Table 2.3 Chemical composition of the ingredients in the substrate Gon Japan KM 94 KM 140-1 Dry matter, % 24.4 30.6 24.6 22.2 Crude protein, % in DM 32.1 27.5 30 29.7 Starch, % in DM HCN concentration, mg/kg 339 419 570 826 DM (*) Data taken from Khempaka et al (2009); ND= not detected Pulp 84.4 2.5 53.5 (*) ND Gas production, ammonia concentration and DM mineralized The percentage of DM mineralized (or DM solubilized) was lower in the sweet cassava variety than in the three bitter varieties among which there were no differences Ammonia concentration in the fermentation medium at the end of the incubation was higher for the sweet cassava than for the bitter varieties (Table 2.4) Table 2.4 Mean values for gas production in 24 hours, DM mineralized and ammonia in an in vitro rumen fermentation Sweet leaves Bitter leaves p value Japa KM 140- SEM Gon KM 94 n Gas, ml/24h 425 520 515 458 39.6 0.300 DM mineralized, 33.6 26.6a 32.6 ab 38.2 b 2.5 0.044 ab % Ammonia mg/L 197 175 177 170 12.3 0.45 ab Mean values in rows without common letter are different at p