SỬ DỤNG cây KHOAI mì (sắn) để PHÁT TRIỂN CHĂN NUÔI dê ở AN GIANG, VIỆT NAM

The positive effects of storing ensiling the cassava stem with addition of urea were the reduction in HCN levels and the possible synthesis of protein from the ammonia derived from the u

Livestock Research for Rural Guide for preparation of LRRD Newsletter Citation of this

Effect on nutritive value of cassava (Manihot esculenta Crantz) stems of ensiling them

with urea

Department of Animal Sciences and Veterinary Medicine, Agricultural and

Natural Resources Faculty, An Giang University, Vietnam

thuyhang.agu@gmail.com

1 Centro para la Investigación en Sistemas Sostenibles de Producción

Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia

4, 6 and 8 weeks) Each treatment combination was replicated 4 times.

The positive effects of storing (ensiling) the cassava stem with addition of urea were 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 On the negative side was the considerable loss of biomass (about 24%) resulting from the fermentation of part of the cassava stem

carbohydrate stimulated by the availability of ammonia from the added urea.

Key words: ammonia, fermentation, HCN, protein, tannins

Introduction

Cassava (Manihot esculenta Crantz) is a perennial woody shrub of the family Euphorbiaceae

It originated in the Caribbean and South America and is extensively cultivated as an annual crop in the tropics and sub-tropics for the dual purpose of tuberous roots for human

consumption and roots and foliage as a feed for animals Cassava foliage is recognized as a source of bypass protein with a high content of digestible nutrients for both non-ruminants and ruminants (Wanapat 1997) The foliage 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 foliage production can be about 5 tonnes dry matter (DM)/ha (Mui 1994) It is estimated that more than 2.5 milion tonnes of cassava foliage are produced in Vietnam, of which about 15,000 tonnes in An Giang, Cassava foliage is usually thrown away after harvesting the root, because of its content of cyanogenic

glucoside, mainly linamarin and lotaustralin (Alan and John 1993) Hydrolysis of these cyanogenic glucosides liberates hydrogen cyanide (HCN) (Poulton 1988) and causes

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toxicity symptoms in animals when the tolerated dose is exceeded.

Cassava foliage consists of the leaves, petioles and small branches which attach to the highly lignified stem Observations at the Rabbit and Goat Center in Bavi, North Vietnam indicated that the stem was well appreciated by goats and this led to the experiment reported by Thanh et al (2013) in which chopped cassava stems supplemented with fresh cassava foliage supported live weight gains in growing goats of 57 g/day, 100% higher than when Guinea grass was used to supplement the cassava stems.

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 stem DM as has been widely proven

in the urea-ensiling of low-protein, fibrous feeds such as rice straw (Trach et al 1998) The specific objectives were to determine if the addition of urea to cassava stems would facilitate the storage of this feed resource and at the same time improve its digestibility.

Material and methods

The experiment was carried out at An Giang University in An Giang Province

in the South of Vietnam from March to June 2015.

Treatments and experimental design

The treatments in a random block 5*5 factorial design were: (a) five levels of urea (0, 1, 2,

3 and 4%, DM basis) added to freshly chopped cassava stems; and (b) five storage times (0, 2, 4, 6 and 8 weeks) Each treatment combination was replicated 4 times Cassava stems were collected from farmers’ fields directly after root harvesting and chopped by hand Representative amounts were analyzed for DM by infra-red 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 the appropriate storage times, samples of the treated stems were taken for measurement of pH (ORION model 420 A) and proximate composition The DM, ash and HCN content were determined according to the standard methods of AOAC (2016) Nitrogen was determined by the Kjeldahl procedure NDF and ADF were analysed according to the procedure of Van Soest et al(1991) Total tannin content was determined according to the method (955.35) of AOAC (2016).

Statistical analysis

The data were subjected to an analysis of variance (ANOVA) using the General Linear Model (GLM) procedure of Minitab 16 Sources of variation were levels of urea, storage time, the interaction urea levels*storage time and random error.

Results and discussion

There were major effects of urea level and storage time on chemical attributes of the

urea-ensiled cassava stems (Tables 1, 2 and 3; Figures 1 – 8).

Table 1 Mean values for effects of urea level on composition of the ensiled cassava stems

Table 2 Mean values for effects of storage time on composition of the ensiled cassava stems

The content of tannin was reduced after 4 weeks of storage and the

effect tended to be greater the higher the level of urea (Figure 1).

Figure 1 Effect of urea level and storage time on tannins in cassava stems

The content of HCN in the stems was reduced gradually over the first two weeks and then more rapidly after 4 weeks with none being detected after 6 weeks of storage (Figure 2).

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Figure 2 Effect of urea level and storage time on HCN in cassava stems

Ammonia level increased massively in the second week of storage, then fell by half

at 4 weeks the levels being proportional to the amounts of urea added (Figure 3).

Figure 3 Effect of urea level and storage time on ammonia in cassava stems

There were consistent effects of urea level on the pH in the stored stems with curvilinear increases to maximum values after 4 weeks of storage declining subsequently (Figure 4) Within storage times the pH was positively related to the level of urea added at the beginning of storage.

Figure 4 Effect of urea level and storage time on pH in cassava stems

After the second week of storage, NDF and ADF levels were reduced linearly by increasing

levels of urea and by length of storage time; however, the changes were of relatively small order (Figures 5 and 6).

Figure 5 Effect of urea level and storage time on NDF in cassava stems

Figure 6 Effect of urea level and storage time on ADF in cassava stems

As expected, the crude protein level in the stems was related linearly to the proportion of urea added at the beginning (Figure 7) There were only slight reductions in overall CP levels with length of storage

Figure 7 Effect of urea level and storage time on crude protein in cassava stems

Urea level had no effect on the DM content of the cassava stems during the first two weeks

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of storage, when the DM content of the cassava stems did not change (Table 3); but from 4 to 8 weeks of storage, the DM content declined linearly, and the

decline was increased linearly with the level of added urea (Figure 8).

Table 3 Mean values for effect of storage time and level of added urea on the DM percentage in the cassava stems

as rice straw (Thuy Hang et al 2005; Trach et al 1998).

The decrease in tannin with urea treatment is likely to be a result of the high

pH caused by evolution of ammonia from urea (Price et al 1979; Makkar 2003a,b) Tannins are easily oxidized at alkaline pH values to quinines,

which may promote covalent bonds to other compounds (Rawel et al 2000) The decrease in HCN with storage time may similarly be the 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 A decrease in HCN toxicity has been reported as a result of increasing the pH of the medium (Huertas et al 2010).

The data for crude protein (N*6.25) is misleading as they do not differentiate between true protein and the products of multiplying the N content by 6.25 The result of major concern for the farmer is the loss of DM from the combined effect of storage time and level of added urea, which resulted in the DM content of the stored stems declining from initial values of 23.6% to 17.6% after 8 weeks of storage with 4% added urea (a loss of about 24%; Figure 8) The slight decline in the percentages of NDF (about 10%) and ADF (4%) account for

only part of the losses; the remainder supposedly being in the form of soluble

carbohydrates There may have been some gain in true protein during storage, but this could not be ascertained in the absence of analytical data for true protein.

Conclusions

The positive effects of storing (ensiling) the cassava stem 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.

On the negative side is the considerable loss of biomass (about 24%) resulting from the fermentation of part of the cassava stems stimulated

by the availability of ammonia rom the added urea.

References

Alan J D and John A M 1993 Effect of oral administration of brassica secondary

metabolites allyl cyanide, allyl isothocyanate and dimethyl disulphide, on the voluntary food intake and metabolism of sheep British Journal of Nutrition 70, 631-645

AOAC 2016 Association of offic ial Analytical chemists (20 th Ed.), Washington, DC

Huertas M J, Sáez L P, Roldán M D, Luque-Almagro V M, Martínez-Luque M, Blasco R,

Castillo F, Moreno-Vivián C and García-García I 2010 Alkaline cyanide degradation by

Pseudomonas pseudoalcaligenes CECT5344 in a batch reactor Influence of pH J Hazard Mater 2010 Jul 15;179(1-3):72-8 doi:10.1016/j.jhazmat.2010.02.059 Epub 2010 Feb 25.

Makkar H P S 2003a Quantification of Tannins in Tree and Shrubs Foliages—A Laboratory Manual Kluwer Academic Press Dordrecht, The Netehrland, p 102.

Makkar H P S 2003b Effects and fate of tannins in ruminant animals, adaptation to tannins, and strategies to overcome detrimental effects of feeding tannin-rich feeds Small Ruminant Res 49, 241–256.

Mui N T 1994 Economic evaluation of growing Elephant grass, Guinea grass, Sugarcane and Cassava as animal feed or as cash crops on Bavi high land In: Proceeding on Sustainable

Livestock Production on Local Feed Resources Agricultural Publishing House, 16-19

Phengvichith V and Ledin I 2007 Effect of a diet high in energy and protein on growth, carcase

characteristics and parasite resistance in goats Tropical Animal Health Production 39, 59–70

Poulton J E 1988 Localization and catabolism of cyanogenic glycosides In: Cyanide Compounds in Biology,

pp 67-91 DOI:10.1002/9780470513712.ch6

Price M L, Butler L G, Rogler J C and Featherston W R 1979 Overcoming the nutritionally harmful effects

of tannin in sorghum grain by treatment with inexpensive chemicals J Agric Food Chem 27, 441–445 Rawel H M Rohn S and Kroll J 2000 Reactions of selected secondary plant metabolites (glucosinolates and phenols) with food proteins and enzymes—influence on physico-chemical protein properties, enzyme activity and proteolytic degradation Recent Res Devel Phytochem 4, 115–142.

Thanh T X, Hue K T, Anh N N and Preston T R 2013 Comparison of different forages as

supplements to a basal diet of chopped cassava stems for growing goats Livestock Research for Rural Development Volume 25, Article #7 http://www.lrrd.org/lrrd25/1/than25007.htm

Thuy Hang L T, Man N V and Wiktorsson H 2005 Fresh rice straw treated with urea and lime

as feed for dairy cattle in An Giang province, Vietnam MSc Thesis Department of Animal Nutrition and Management Swedish University of Agricultural Science

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Trach N X, Dan C X, Ly L V and Sundstøl F 1998 Effects of urea concentration, moisture content and duration of treatment on chemical composition of alkali treated rice straw Livestock Research for Rural Development Volume 10, Article #9 http://www.lrrd.org/lrrd10/1/trac101.htm Undersander D, Mertens, D R and Thiex N 1993 Forage Analayses Procedures.National forage Testing Association, Omaha.

Van Soest P J, Robertson J B and Lewis B A 1991 Methods for Dietary Fiber, Neutral Detergent Fiber, and Nonstarch Polysaccharides in Relation to Animal Nutrition Journal of Dairy Science 74(10), 3583-3597.

Wanapat M, Pimpa O, Petlum A and Boontao U 1997 Cassava hay: A new strategic feed for ruminants during the dry season Livestock Research for Rural Development Volume 9, Article #18 http://www.lrrd.org /lrrd9/2/metha92.htm

Received 20 May 2019; Accepted 20 May 2019; Published 4 June 2019

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Livestock Research for Rural Development 30 (5) 2018 Guide for preparation of LRRD Newsletter Citation of this

Effect of biochar and water spinach on feed intake, digestibility and

N-retention in goats fed urea-treated cassava stems

Le Thi Thuy Hang, T R Preston1, R A Leng2 and Nguyen Xuan Ba3

Faculty of Animal Sciences and Veterinary Medicine, Agricultural and Natural Resources Faculty, An Giang University, Vietnam

thuyhang.agu@gmail.com

1 Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia

2 University of New England, Armidale, NSW 2351, Australia

3 Hue College of Agriculture and Forestry, Hue University, VietnamAbstract

Four “Bach Thao” goats (LW 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 (derived by carbonization of rice husks in an updraft gasifier stove) at 1% of DM intake (UCSB) or with water spinach + 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 feces and urine).

Urea treatment of the cassava stems increased the crude protein from 5.5 to 11.7% in DM DM intake was increased 18% by supplementing the treated cassava stems 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%.

urea-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 microbial growth resulting in an increase in synthesis and hence of absorption of amino acids We suggest that biochar effectively functions as a “prebiotic” – stimulating the activity of beneficial microbial communities through its support for biofilms in the digestive tract of the animal.

Key words: biofilms, biological value, microbial communities, prebiotic

Introduction

Major advances have been made recently in the integrated use of the cassava plant as a means of intensifying ruminant livestock

production A system of fattening cattle intensively on cassava pulp (the residue after industrial starch extraction) was developed by Phanthavong et al (2014, 2015), in which urea provided rumen fermentable ammonia and bypass protein was supplied by brewers’ grains at 30% of the diet In a follow-up series of experiments it was shown that fresh cassava foliage could replace the major part of the brewers’ grains as bypass protein source, provided that a small amount of brewers’ grains (4 to 5% of the diet DM) was retained apparently acting as a

“prebiotic” to counteract the potential toxicity of the HCN released from the cyanogenic glucosides in the cassava foliage (Inthapanya et al 2016; Binh et al 2017) The system was further developed to use ensiled cassava root as the carbohydrate energy source with a local “rice wine” byproduct replacing the brewers’ grains as the source of prebiotic (Sengsouly et al 2016; Inthapanya et al 2017).

An experiment with growing goats fed almost exclusively (95% of the diet DM) on fresh cassava foliage (Sina et

2017),confirmed the vital role of the small supplement of brewers’ grains’ in a cassava-based feeding system Growth performance was more than doubled from 65 to 160g/day when the brewery byproduct was included at 5% of the diet DM.

Increased understanding of the role of prebiotics as support for biofilms and their associated microbial communities involved in the animal’s digestive system led to an appraisal of the potential role of biochar as a prebiotic, following it’s known ameliorating properties in soils (Lehmann 2007; Preston 2015) thought to be due to its interactive role in supporting microbial communities in this medium.

In an initial study with 1% biochar in the diet (Leng et al 2012), growth rates were increased 20% but were probably constrained by errors in management of the feed resource (fresh cassava root) that probably propitiated growth of mycotoxins (R A Leng, personal communication) More recent studies have shown synergistic effects from combining biochar with rice distillers’ byproduct in a cassava-based diet for fattening cattle (Sengsouly et al 2016) and by combining biochar with water spinach in diets of goats (Silivong et al 2015, 2016).

On the basis of this background, the present experiment was designed with the aim of determining if the synergistic effects of biochar and water spinach on growth of goats fed foliage of Bauhinia accuminata would be equally manifested when the basal diet was composed of urea-treated cassava stems, shown to be a potential feed resource for goats by Thanh et al (2013).

Materials and methods

Experimental design

The experiment was conducted from June to September 2015 at An Giang University farm, An Giang province, Vietnam 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 water spinach + biochar (CSWB) The design was a Latin square (Table 1) with four

treatments and four periods, each lasting 17 days (12 days for adaptation and 5 days for collection of feces and urine).

Table 1 The layout of the experiment Period Goat 1 Goat 2 Goat 3 Goat 4

Animals and management

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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 (sweet variety) was planted in sandy soil in the An Giang University farm from January to August 2015 It was fertilized (per ha) with 8 tonnes of cattle manure, 175 kg urea, 200 kg super-phosphate and 130 kg potassium chloride The cassava stems (no leaves; Photo1) were harvested at 30-40cm 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 (Photo 2), mixed with urea (3% DM basis;

no water was added) and ensiled in closed plastic bags after first extracting the air (Photo 4) They were ensiled for 21 days (Photo 5), after which they were fed ad libitum as the basal diet of the goats (Photo 6).

Photo 1 Freshly harvested Photo 2 Chopping into Photo 3 Urea added at

cassava stems 5-10 cm lengths 3% of stem DM

Photo 4 Chopped stems-urea are put in Photo 5 Urea-treated stems Photo 6 Urea-treated stems after

polyethylene bags and the air extracted are stored for 21 days 21-day storage ready for feedingThe biochar was made by combusting rice husks in an updraft gasifier stove (Photo 7) The chosen amounts were

offered twice daily in troughs separate from the cassava stem (Photo 8).

Before starting the experiment, it took several days to accustom the goats to eat the biochar First, biochar was mixed with small quantities of rice bran and water spinach After, 3-4 days all the goats were eating this mixture Then the rice bran and water spinach were gradually removed over the following 3-4 days During the experiment, when the diets were changed from “no biochar” to “biochar” [eg: “UCSW to UCSWB] it required only 1 to 2 days for the goats to adapt to the biochar as they had already been accustomed to eat it before the experiment began.

Photo 7 The biochar was the residue from rice husks used as fuel in a gasifier stove (Paul Olivier)

Photo 8 Biochar, water spinach and urea-treated cassava stems were fed in separate troughs Feed refusals were weighed every morning prior to giving the new feed Samples of each diet component were taken daily, stored at -18C, 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 am and 16:00pm and added to jars containing 100 ml of 10% (v/v) 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.

Statistical analysis

Data were analyzed with the General Linear Model option of the ANOVA program in the MINITAB software (Minitab 2000) Sources of variation were treatments, animals, periods and error.

Results and discussion

Composition of the diet ingredients

Urea-treatment of the cassava stems doubled the crude protein content (Table 2) The WRC value (water retention

capacity) of 4.4 liters of water per 1 kg of biochar is similar to that reported for combustion of rice husks in a down-draft gasifier (Orosco et al 2018), and indicates that the biochar had a high “adsorptive” capacity.

Table 2 Chemical composition of diet ingredients (UCS is urea-treated cassava stems

% CP ADF NDF OM

CS 33.4 5.50 51.8 66.30 93.5 UCS 23 0 11.7 51.4 67.1 92 6.92 Water spinach 13.6 18.1 27.6 36.2 93.4

WRC Water retention capacity

DM intake was increased 18% by supplementing the urea-treated cassava stems with biochar which was fed separately {Photo 8) at 1% of the diet DM (Table 3; Figure 1) 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%.

Figure 1 Effect of biochar on DM intake goats fed urea-treated cassava stems, with or without fresh water spinach and with or without biochar

Table 3 Mean values of feed DM intake (DMI)in goats fed urea-treated cassava stems, with or without fresh water spinach and with or without biochar

Coefficients of apparent DM digestibility were increased more by biochar (by 9%) than by water spinach (2.4%) (Table 4; Figures 2 and 3) The combined effect of biochar plus water spinach was to increase DM digestibility by 12% Results for organic matter were similar Digestibility coefficients for crude protein have no real meaning when the major part of the dietary nitrogen (40-50%) is in the form of NPN (urea and ammonia) derived from urea-treatment of the cassava stems.

Table 4 Mean values of apparent digestibility coefficients (%) in goats fed urea-treated cassava stems

supplemented with or without fresh water spinach (1% of LW, DM basis) and biochar at 1% of DM intake.

Dry matter (%) 59.4 b 64.8 a 60.8 b 66.3 a 0.88 <0.001 Crude protein 53.2 b 60.1 a 59.3 a 63.1 a 1.54 <0.010 Organic matter 59.4 b 65.0 a 61.6 ab 66.8 a 1.78 0.066

ab, Means within rows without common superscripts differ at P<0.05

Table 5 Mean values for N balance in goats fed urea-treated cassava stem supplemented with or without fresh water spinach (1% of LW, DM basis) and biochar at 1% of DM intake.

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UCS UCSB UCSW UCSWB SEM p

N balance, g/d Intake 8.13 d 9.23 c 12.4 b 13.0 a 0.151 <0.001 Feces 3.79 b 3.659 b 5.099 a 4.81 a 0.171 <0.001 Urine 1.30 1.17 1.42 1.25 0.065 0.065 Retention 3.03 d 4.42 c 5.84 b 6.9 a 0.217 <0.001 Biol value# 69.9 c 78.6 b 80.0 ab 84.4 a 1.39 <0.001 ab,c Means within rows without common superscripts differ at P<0.05

# N retention as % of N digested

Figure 2 Effect of water spinach on DM digestibility in goats fed urea-treated Figure 3 Effect of biochar on DM digestibility in goats fed urea-treated

cassava stems with or without a supplement of biochar cassava stems with or without a supplement of water spinach

The most dramatic effects of biochar supplementation were on N retention (Table 5; Figures 4 and 5) and the biological value of the protein absorbed (calculated as the N retained as percent of N digested) (Figures 6 and 7) 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 5) Comparable values for the increases in biological value of the protein were 12 and 4% Biochar provides essentially no protein (0.0037% CP in diet DM) thus the increase in N retained and in its biological value can only have come about as a result of the biochar stimulating rumen microbial growth resulting in an increase in synthesis and hence in absorption of amino acids It is hypothesized that biochar promotes habitat for micro- organisms that detoxify phytotoxins (Leng 2017); and that the “free” selection of biochar is an example of

“self-medication”, similar to that reported by Struhsaker et al (1997) These authors reported that: “charcoals adsorb organic materials, such as phenolics, particularly well and, as a consequence, remove these compounds, which have the potential to be toxic or interfere with digestion or both”.

Figure 4 Effect of water spinach on N retention in goats fed urea-treated Figure 5 Effect of biochar on N retention in goats fed urea-treated cassava

cassava stems with or without a supplement of biochar stems with or without a supplement of water spinach

Figure 6 Effect of water spinach on N retention as % of digested N in goats fed Figure 7 Effect of biochar on N retention as % of digested N in goats fed

urea-urea-treated cassava stems with or without a supplement of biochar treated cassava stems with or without a supplement of water spinach

Conclusions

Urea treatment of the cassava stems increased the crude protein from 5.5 to 11.7% in DM.

DM intake was increased 18% by supplementing the urea-treated cassava stems 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%.

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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 microbial growth resulting in an increase in synthesis and hence of

absorption of amino acids.

We suggest that biochar functions as a “prebiotic” – facilitating the activity of beneficial microbial communities that enhance fermentation or remove the effects of phytotoxins or mycotoxins.

Acknowledgments

This research is part of the requirement by the senior author for the degree of PhD at Hue University of Agriculture and Forestry, Hue University, Vietnam The authors acknowledge support for this research from the MEKARN II project financed by Sida; and the University of An Giang, Vietnam.

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Inthapanya S, Preston T R and Leng R A 2016; Ensiled brewers’ grains increased feed intake, digestibility and N retention in cattle fed ensiled cassava root, urea and rice straw with fresh cassava foliage or water spinach as main source of protein Livestock Research for Rural Development Volume 28, Article #20 http://www.lrrd.org/lrrd28 /2/sang28020.htm

Inthapanya S, Preston T R, Phung L D and Ngoan L D 2017: Effect of supplements of yeast (Saccharomyces cerevisiae), rice distillers’ by-product and fermented cassava root on methane production in an in vitro rumen incubation of ensiled cassava root, urea and cassava leaf meal Livestock Research for Rural Development Volume 29, Article #220 http://www.lrrd.org/lrrd29/12/sang29220.html

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Sengsouly P and Preston T R 2016: Effect of rice-wine distillers’ byproduct and biochar on growth performance and methane emissions in local “Yellow” cattle fed ensiled cassava root, urea, cassava foliage and rice straw Livestock Research for Rural Development Volume 28, Article #178 http://www.lrrd.org/lrrd28/10/seng28178.html

Silivong P and Preston T R 2015: Growth performance of goats was improved when a basal diet of foliage of Bauhinia acuminata was supplemented with water spinach and biochar Livestock Research for Rural Development Volume 27, Article #58 http://www.lrrd.org/lrrd27/3/sili27058.html Silivong P and Preston T R 2016 : Supplements of water spinach (Ipomoea aquatica) and biochar improved feed intake, digestibility, N retention and growth performance of goats fed foliage of Bauhinia acuminata as the basal diet Livestock Research for Rural Development Volume 28, Article #98 http://www.lrrd.org/lrrd28/5/sili28098.html

Sina V, Preston T R and Tham T H 2017 : Brewers’ grains have a synergistic effect on growth rate of goats fed fresh cassava foliage (Manihot esculenta Crantz) as basal diet Livestock Research for Rural Development Volume 29, Article #137 http://www.lrrd.org/lrrd29/7/sina29137.html

Struhsaker T T, Cooney D O and Siex K S 1997 Charcoal Consumption by Zanzibar Red Colobus Monkeys: Its Function and Its Ecological and Demographic Consequences.

International Journal of Primatology, 18: 61-72 doi:10.1023/A:1026341207045 https://link.springer.com/article/10.1023/A:1026341207045

Thanh T X, Hue K T, Anh N N and Preston T R 2013 : Comparison of different forages as supplements to a basal diet of chopped cassava stems for growing goats Livestock Research for Rural Development Volume 25, Article #7 http://www.lrrd.org/lrrd25/1/than25007.htm

Received 16 March 2018; Accepted 27 April 2018; Published 1 May 2018

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