Phụ phẩm từ sắn là nguồn thức ăn tiềm năng trong chăn nuôi bò ở cộng hoà dân chủ nhân dân lào (tt)

LIST OF PUBLISHED SCIENTIFIC PAPERS
RELATED TO DISSERTATION
1. Full name:

Mr. Phanthavong VONGSAMPHANH

2. Birth place:

Vientiane Capital, Lao PDR

3. Date of birth:

18 February 1972

4. Working place:

Department of Livestock and Fisheries, Ministry of Agriculture and
Forestry, Lao PDR

5. List of published scientific papers (Name of papers, publication house, volume, issue)
Name of paper:
1: Effect of leaves from sweet or bitter cassava and brewers’ grains on methane production in
an in vitro rumen incubation of cassava root pulp-urea
2: Fattening “Yellow” cattle on cassava root pulp, urea and rice straw: completely mixed ration
system with cassava foliage as protein supplement compared with feeds not mixed and
brewers’ grains as protein source
Publication house:
1& 2: Livestock Research for Rural Development (www.lrrd.org)
Volume:
1 & 2: 30, On-Line Edition
Issues:

1: 9 (September) & article # 167 />2: 10 (October) & article # 169 />
The next pages is attached full text of published scientific papers
Hue, date: 20 September 2019
PhD student Signature

Phanthavong VONGSAMPHANH


Livestock Research for Rural
Development 30 (9) 2018

Guide for preparation of
papers

LRRD Newsletter

Citation of this
paper

Effect of leaves from sweet or bitter cassava and brewers’ grains
on methane production in an in vitro rumen incubation of cassava
root pulp-urea
Phanthavong Vongsamphanh, Sangkhom Inthapanya1, T R Preston2, Dinh Van
Dung3 and Nguyen Xuan Ba3
Department of Livestock and Fisheries, Ministry of Agriculture and Forestry PO Box 6644 Vientiane, Lao PDR

1
Animal Science Department, Faculty of Agriculture and Forest Resource Souphanouvong University Lao PDR
2
Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 662 Cali, Colombia

3
Faculty of Animal Husbandry and Veterinary Medicine, Hue University of Agriculture and Forestry, Hue
University, Hue City, Vietnam

Abstract
The aim of this study was to evaluate the effect of cassava leaves (from sweet and
bitter varieties) and supplementation with brewers’ grains (0 or 4%) on methane production in
an in vitro rumen incubation of cassava pulp-urea as the main substrate. The design was a 2*2
factorial of 4 treatments with 4 replications. The two factors were: source of cassava leaves:
sweet or bitter variety; and 4% brewers’ grains or none. The incubation was for 24h with
measurements of total gas production and methane percentage at 6h intervals and
determination of residual undigested substrate at the end.
The rate of gas production was higher when leaves of sweet rather than bitter cassava
were the source of protein; and when brewers’ grains were added to the substrate. For all
incubation intervals the methane content in the gas was lower for bitter than for sweet cassava
leaves and lower when brewers’ grains were added to the substrate. The proportion of
substrate DM that was digested, and the methane produced per unit DM digested, was
reduced when the leaves of bitter rather than sweet cassava were the source of protein. The
effect of the brewers’ grains was to increase the proportion of DM digested and to reduce the
methane production per unit of substrate digested.
Key words: fermentation, secondary plant compounds, soluble protein, tannins

1


Introduction
Cassava in Lao PDR is mainly planted as an industrial tuber crop for starch
production. It is the third most important food crop after rice and maize, the planting area
having increased from 6,765 ha in 2005 to 63,260 ha in 2017 (MAF 2017). In the processing
of the roots some 15% remains in the form of cassava pulp (Sriroth et al 2000). The pulp is

high in fermentable carbohydrates and can contaminate the environment if not well managed.
However, we have shown that when adequately supplemented the pulp can be the basis of an
intensive cattle fattening system to produce quality beef for export (Phanthavong et al., 2015).
The cassava varieties used for industrial starch production have been selected for high
yield and are known as “bitter” varieties due to the high content of cyanogenic glucosides that
are converted into the highly toxic hydrocyanic acid when consumed by animals and people.
However, research by Phuong et al (2012) showed that from the point of view of the
environment, and especially the problem of global warming, the presence of the cyanogenic
glucosides in cassava could be an advantage as methane production in an in vitro rumen
fermentation was found to be lower when the cassava leaves in the fermentation substrate
were from “bitter” rather than from “sweet “varieties”. A related finding was that enteric
methane production from a cassava-based feeding system could also be reduced by adding
small amounts (4% of diet DM) of brewers’ grains to a cassava root-urea feeding system
(Binh et al 2017).

Objective:
o To study effects of source of cassava leaves (sweet or bitter at 4% DM) and with or
without of brewers’ grain at 4% DM in an in vitro rumen fermentation on gas and
methane production using the ensiled cassava pulp supplemented with urea as basal
substrate

Materials and methods
Location
The experiment was conducted in the laboratory of the Faculty of Agriculture and
Forest Resource, Souphanouvong University, Lao PDR.
Treatments and experimental design
Two factors were studied in an in vitro rumen incubation according to a 2*2 factorial
design with 4 replications. The factors were:
2



Source of cassava leaves: Sweet or Bitter variety



With or without addition of 4% brewers’ grains in the fermentation substrate.

The basal substrate was ensiled cassava pulp supplemented with urea (Table 1) and
with additions of rice straw and rice bran.
Table 1. Ingredients in the substrate, g DM
BCF
SCF
0%BG
4%BG
0%BG
4%BG
CP
46
46
46
46
BCF
30
26
SCF
30
26
BW

4
4
RS
16
16
16
16
Rice bran
5
5
5
5
Urea
2.5
2.5
2.5
2.5
Mineral #
0.5
0.5
0.5
0.5
Total
100
100
100
100
Contains P and S to provide 0.3 % P and 0.2% S in the substrate DM:
CP: Cassava pulp; BCF bitter cassava foliage; SCF sweet cassava foliage, BW
brewers ‘grain; RS rice straw

In vitro rumen fermentation system
The in vitro rumen fermentation system was that described by Inthapanya et al (2011;
Diagram 1). Recycled water bottles (capacity 1500ml) were used for the fermentation and
collection of the gas. A hole was made in the lid of each of the bottles, which were
interconnected with a plastic tube (id 4mm). The bottle receiving the gas had the bottom
removed and was suspended in a larger bottle (5 liter capacity) partially filled with water, to
collect the gas by water displacement. The bottle that was suspended in water was calibrated
at 50ml intervals to indicate the volume of gas.

3


Figure 1. A schematic view of measuring gas production in the in vitro rumen
fermentation

Experimental procedure
Leaves from sweet and bitter cassava varieties were collected in the morning from
plots in the campus of Souphanouvong University. They were immediately chopped into
small pieces (0.5-1.0 cm) and then ground (1mm sieve). Cassava pulp was collected from the
storage pit at the Cassava Starch Factory in Nashaw village (Phanthavong et al., 2014). Urea,
rice bran, rice straw (chopped and ground), sulphur-rich minerals and brewers’ grains were
mixed with the cassava pulp and cassava leaves and put in the fermentation bottle prior to
adding 960 ml of buffer solution (Table 2) and 240 ml of rumen fluid (obtained from a newly
slaughtered animal of the local “Yellow” breed in the Luang Prabang District abattoir). The
residual air in the fermentation bottle was flushed with carbon dioxide. The bottles were
incubated at 38ºC in a water bath for 24h.
Table 2. Ingredients of the buffer solution (g/liter)
CaCl2
0.04

NaHPO4.12H2O NaCl
9.30
0.47

KCl
0.57

MgSO4.7H2O
0.12

NaHCO3
9.80

Cysteine
0.25

Source : Tilly and Terry (1963)

Data collection and measurements
The volume of gas was measured at 6, 12, 18 and 24h of the incubation, and the
methane concentration recorded by passing the gas through a Crowcon infra-red analyser
(Crowcon Instruments Ltd, UK). The residual DM in the incubation bottle was determined by
filtering the residue through cloth and drying at 65°C for 72h. Solubility of the protein in the
cassava leaves was determined by shaking 3g of dry leaf meal in 100 ml of M NaCl for 3h
then filtering through Whatman No.4 filter paper and determining the N content of the filtrate
(Whitelaw and Preston, 1963). The ingredients in the substrate and the residue were analysed
for DM, ash and N according to AOAC (1990) methods

Statistical analysis

The data were analyzed by the general linear model option of the ANOVA program in
the Minitab software (Minitab 2014). The statistical model used was:
Yijk = μ + Pi + Aj + Pi*A j+ eijk
μ = Overall mean
Pi = Source of cassava leaves
4


Aj = With or without brewers’ grains
Pi*Aj = Interaction between source of cassava leaves and brewers’ grains
eijk = random error

Results and discussion
Chemical composition
The solubility of the protein was lower in bitter than in sweet cassava leaves (Table 3)
presumably due to higher levels of condensed tannins as reported by Sarkiyayi Agar (2010).
Table 3. The chemical composition of substrate ingredients (% in DM, except DM which
is on fresh basis)
DM

CP

Ash

Protein solubility, %

Cassava pulp

24.3

1.8

5.6

-

Sweet cassava leaves

27.2

25.0

9.2

32.2

Bitter cassava leaves

26.9

26.1

9.5

30.8

Rice straw

90.4

2.1

13.4

-

Rice bran

90.1

12.0

10.9

Gas and methane production
The rate of gas production was highest in the incubation interval 12-18h, and over 24h
was higher for leaves of sweet compared with bitter cassava variety, and higher when
brewers’ grains were added to the substrate (Table 4; Figures 2-5). For all incubation intervals
the methane content in the gas was lower for bitter than for sweet cassava leaves and lower
when brewers’ grains were added to the substrate (Figures 6-8). The percent of substrate that
was digested was reduced by presence of bitter compared with sweet cassava leaves and was
increased when brewers’ grains were added to the substrate (Figure10). Methane produced per
unit DM digested was reduced by bitter cassava leaves and by adding brewers’ grain to the
substrate.

5


Table 4. Mean values for gas production, methane in the gas, DM digestibility and methane
per units substrate

Variety cassava leaves
Bitter
Sweet
Gas production, ml
0-6h
715
6-12h
1006
12-18h
1081
18-24h
625
Methane in the gas, %
0-6h
9.3
6-12h
13.6
12-18h
20.1
18-24h
26.1
Total gas, ml
3428
Total methane, ml
583
DM digested, %
67.1
CH4, ml/g DM
69.4
digested

p

Brewers’ grains
None
4%

SEM

p

788
1075
1213
838

0.002
0.036
<0.001
<.001

721
994
1088
706

781
1088
1206
756

12.7
20.6
15.5
34.4

0.006
0.007
<0.001
0.325

10.3
16.1
21.9
29.3
3913
763
71.2

0.04
0.002
<0.001
0.001
<0.001
<0.001
0.003

10
15.4
21.6

28.4
3509
662
65.7

9.5
14.4
20.4
27
3831
684
72.5

0.306
0.439
0.280
0.528
36.52
9.228
0.772

0.271
0.133
0.008
0.09
<0.001
0.129
<0.001

86.5

<0.001

81.0

74.9

1.613

0.002

Figure 2. Effect of sweet or bitter cassava
leaves with or without brewers’ grains on
gas production 0-6h

Figure 3. Effect of sweet or bitter cassava leaves
with or without brewers’ grains on gas production
6-12h

6


Figure 4. Effect of sweet or bitter cassava
leaves with or without brewers’ grains on
gas production 12-18h

Figure 5. Effect of sweet or bitter cassava
leaves with or without brewers’ grains on gas
production 18-24h

The methane content of the gas increased as the fermentation advanced and was
reduced when bitter cassava leaves replaced leaves of sweet cassava, and when 4% brewers’
grains was included in the substrate (Table 4; Figures 6-9).

Figure 6. Effect of sweet or bitter cassava leaves
with or without brewers’ grains on percent
methane in the gas 0-6h

Figure 7. Effect of sweet or bitter cassava leaves with
or without brewers’ grains on percent methane in the
gas 6-12h

Figure 8. Effect of sweet or bitter cassava leaves
with or without brewers’ grains on percent
methane in the gas 12-18h

Figure 9. Effect of sweet or bitter cassava leaves
with or without brewers’ grains on percent
methane in the gas 18-24h

The proportion of the substrate DM that was digested during the incubation was
increased when brewers’ grains were included in the substrate and was reduced when the
protein supplement was from bitter compared with sweet cassava leaves (Table 4; Figure 10).

7


Figure 10. Effect of sweet or bitter cassava leaves with or without brewers’ grains on
percent DM digested

Figure 11. Effect of sweet or bitter cassava leaves with or without brewers’ grains on methane
per unit substrate digested

Discussion
There is now abundant evidence confirming the reduction in methane production when
leaves from bitter cassava replace leaves from the sweet variety in in vitro rumen incubations
of: molasses (Phuong et al., 2012), cassava root pulp (Phanthavong et al., 2015; Binh et al.,
2018) and Bauhinia acuminata (Silivong et al., 2018). This effect in reducing methane
production would seem to be the direct consequence of the higher concentrations in bitter
versus sweet cassava leaves of a range of anti-nutritional compounds (cyanogenic glycosides,
trypsin inhibitors, oxalates, phytate and tannin) reported by Sarkiyayi and Agar (2010). The
research of Smith et al (1985) supports the concept that cyanide is toxic to methanogens,
and/or reduces their potential growth by lowering the availability of sulphur by formation of
8


thiocyanates (Majak and Cheng, 1984). Additions of 5, 10, and 25 mg 1itre-l cyanide (from
KCN or linamarin) temporarily inhibited methanogenesis in biodigesters charged with
cassava root waste, but when the concentration of cyanide returned to lower levels (as it was
before KCN or linamarin addition), methane production recovered (Cuzin and Labat, 1992). It
was concluded that the biodigester methanogenic microflora were sensitive to the added
cyanide.
The reduction in DM digestibility when the cassava leaves were from bitter rather than
sweet varieties suggests that the higher concentration of cyanogenic glucosides (and perhaps
other secondary plant compounds) in the bitter varieties were having an inhibitory effect on
the rumen microbiota in general as well as on methanogens.
There is also supporting evidence that the addition of small amounts (4% as DM) of
brewers’ grains to an in vitro incubation of cassava pulp reduces methane production (Binh et
al., 2018), and that a byproduct from rice fermentation and distillation (rice distillers’
byproduct) has similar effects (Sangkhom and Preston, 2016; Inthapanya et al., 2017).

It is suggested that the increased rumen DM digestibility due to both these additives
may reflect the improvement in habitat and consequent support for formation of biofilms that
facilitate the activities of the overall rumen microbiota, as postulated by Leng (2017). The
“prebiotic” effect of the beta-glucan present in the cell walls of barley, rice and yeast, which
appears to be released by the process of fermentation and distillation in the manufacture of
beer and rice wine, is another factor that could have contributed to the beneficial effects on
rumen fermentation, and hence on digestibility, due to these additives.

Conclusions
In an in vitro incubation of cassava pulp the rate of gas production was higher, when
leaves of sweet rather than bitter cassava were the source of protein; and when 4% of brewers’
grains were added to the substrate.
For all incubation intervals the methane content in the gas was lower for bitter than for
sweet cassava leaves and lower when brewers’ grain was added to the substrate.
The proportion of substrate DM that was digested, and the methane produced per unit
DM digested, were reduced when leaves of bitter rather than sweet cassava were the source of
protein. By contrast, the effect of the brewers’ grain was to increase the proportion of DM
digested and to reduce the methane production per unit of substrate digested.

9


References
AOAC 1990 Official Methods of Analysis.Association of Official Analytical Chemists.15th
Edition (K Helrick editor). Arlington pp 1230.
Binh P L T, Preston T R, Duong K N and Leng R A 2017 A low concentration (4% in diet dry
matter) of brewers’ grains improves the growth rate and reduces thiocyanate excretion
of cattle fed cassava pulp-urea and “bitter” cassava foliage. Livestock Research for
Rural Development. Volume 29, Article #104.
/>Binh P L T, Preston T R, Van H N and Dinh V D 2018 Methane production in an in vitro

rumen incubation of cassava pulp-urea with additives of brewers’ grain, rice wine
yeast culture, yeast-fermented cassava pulp and leaves of sweet or bitter cassava
variety. Livestock Research for Rural Development. Volume 30, Article #77.
/>Cuzin N and Labat M 1992 Reduction of cyanide levels during anaerobic digestion of
cassava. International Journal of Food Science 27 329-326
Inthapanya S, Preston T R and Leng R A 2011 Mitigating methane production from
ruminants; effect of calcium nitrate as modifier of the fermentation in an in vitro
incubation using cassava root as the energy source and leaves of cassava or Mimosa
pigra as source of protein. Livestock Research for Rural Development. Volume 23,
Article #21. />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. />Leng R A 2017 Biofilm compartmentalisation of the rumen microbiome: modification of
fermentation and degradation of dietary toxins. Animal Production Science. 57(11)
2188-2203. />MAF 2017 Agricultural statistics year book 2017, Department of Planning and Finance,
Ministry of Agriculture and Forestry, Lao PDR, 138 pp.
Majak W and Cheng K J 1984 Cyanogrnesis in bovine rumen contents and pure cultures of
rumen bacteria Journal Animal Science 59, 784-790
/>Minitab 2014 Statistical Software. Minitab Inc. Company. State College (Pennsylvania).

Phanthavong V, Viengsakoun N, Sangkhom I and Preston T R 2014 Cassava pulp as livestock
feed; effects of storage in an open pit. Livestock Research for Rural Development.
Volume 26, Article #169. />Phanthavong V, Viengsakoun N, Sangkhom I and Preston T R 2015 Effect of biochar and
leaves from sweet or bitter cassava on gas and methane production in an in vitro
rumen incubation using cassava root pulp as source of energy. Livestock Research for
10


Rural Development. Volume 27, Article #72. />Phuong L T B, Preston T R and Leng R A 2012 Effect of foliage from “sweet” and “bitter”

cassava varieties on methane production in in vitro incubation with molasses
supplemented with potassium nitrate or urea. Livestock Research for Rural
Development. Volume 24, Article #189. />Sarkiyayi S and Agar T M 2010 Comparative Analysis on the Nutritional and Anti-Nutritional
Contents of the Sweet and Bitter Cassava Varieties. Advance Journal of Food Science
and Technology 2(6): 328-334,
Silivong Phonevilay, Preston T R, Nguyen Huu Van and Duong Thanh Hai 2018 Effect of
sweet or bitter cassava leaves and biochar on methane production in an in vitro
incubation with substrates of Bauhinia acuminata and water spinach (Ipomoea
aquatica). Livestock Research for Rural Development. Volume 30, Article #163.
/>Smith M R, Lequerica J L and Hart M R 1985 Inhibition of methanogenesis and carbon
metabolism in Methanosarcina sp. by cyanide, Journal of Bacteriology, 162, 67-71.
Sriroth K, Chollakup R, Chotineeranat S, Piyachomkwan K and Oates C G 2000 Processing
of cassava waste for improved biomass utilization. Bioresource Technology , Volume
71, pp 63-69
Tilley J M A and Terry R A 1963 A two stage technique for the in vitro digestion of forage
crops. Journal of the British Grassland Society 18: 104
Whitelaw F G and Preston T R 1963 The nutrition of the early-weaned calf III. Protein
solubility and amino acid composition as factors affecting protein utilization. Animal
Science, Volume 5, Issue 2, pp. 131-145 Published online: 01 September 2010
/>
11


Livestock Research for Rural
Development 30 (10) 2018

Guide for preparation of
papers

LRRD Newsletter

Citation of
this paper

Fattening “Yellow” cattle on cassava root pulp, urea and rice straw:
completely mixed ration system with cassava foliage as protein supplement
compared with feeds not mixed and brewers’ grains as protein source
Phanthavong Vongsamphanh, T R Preston1, Thansamay Vorlaphim2, Dinh Van
Dung3 and Nguyen Xuan Ba3
Department of Livestock and Fisheries, Ministry of Agriculture and Forestry, Vientiane, Lao PDR

1
Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera
25 No 6-62 Cali, Colombia
2
Livestock Research Center, National Agriculture, Forestry and Rural Development Institute
Vientiane, Lao PDR
3
Faculty of Animal Husbandry and Veterinary Medicine, Hue University of Agriculture and Forestry,
Hue University, Hue City, Vietnam.

Abstract
The concept of the “Complete Mixed Ration” (CMR)” was evaluated as the basis of the
method for incorporating cassava foliage as the protein-fiber source in a fattening system for
local Yellow cattle based on ensiled cassava pulp (derived from processing of cassava roots
for starch production). Ensiled cassava pulp was mixed with fresh cassava foliage and rice
straw in fresh form the day prior to feeding (CMR); or ensiled during three weeks prior to
feeding (ECMR). In both cases urea and minerals were added to the mixed rations at the time
of feeding. The control system (CTL) was providing the feeds separately, in the same feed
trough, with the cassava foliage replaced by brewers’ grains. Local Yellow cattle (n=15; mean

live weight 160 kg) were housed in individual pens and fed for 90 days on each of the
treatments.
Growth rates were 622 and 608 g/day when the diet of ensiled cassava pulp,
supplemented with urea, cassava foliage, brewers’ grains and rice straw, was fed as a
completely mixed ration in fresh form (CMR), or after ensiling for 21 days (ECMR). Live
weight gains were 30% higher (857 g/day) when almost all the protein was in the form of
brewers’ grains, and the ingredients were not mixed (apart from the urea which was dissolved
in the cassava pulp at the time of feeding). Feed conversion rates were 8.85 and 9.14 for the
CMR and ECMR systems compared with 6.61 for the control. It is suggested that excessively
high levels of cyanogenic glucosides in the cassava foliage, which was collected at the end of
the dry season from a “bitter” cassava variety at the time of root harvest, may have
contributed to the poorer performance of the cattle fed the CMR diets.

1


Key words: bitter cassava, cyanogenic glucosides, ensiling, fumonisin, HCN, mycotoxins

Introduction
The commercial beef industry and beef value chain in Lao People’s Democratic Republic
(Lao PDR) is relatively small and at an early stage of development (MAF 2016).
Transforming cattle production from smallholder subsistence to more intensive systems using
locally available byproducts from cassava starch factories is a recent development
(Phanthavong et al 2014) that has potential widespread application There are five factories
processing annually 1.6 million tonnes of cassava roots, of which some 15% remains in the
form of cassava pulp. The system built around the cassava pulp as the basal feed resource
(Phanthavong et al 2016a) used urea to provide the ammonia needed by rumen microorganisms, brewers’ grains as the source of bypass protein and rice straw for fiber. On this
system the growth rates of local Yellow cattle were close to 800g/day with a conformation
after 90 days feeding indicative of quality beef grade (Photo 1).

Photo 1. Local Yellow cattle fattened for 90 days on cassava pulp-urea, brewers’ grains and rice straw

One of the challenges for extending the application of this fattening system has been to
identify a local replacement for the brewers’ grains, which was the initial source of the bypass
protein that plays a key role in supplementing the microbial protein derived from urea. The
foliage from the cassava plant is the obvious first choice in view of the successful use of this
protein source to supplement urea in a cattle-fattening system based on molasses-urea
(Ffoulkes and Preston 1978).
The first attempts to use cassava foliage to supplement the cassava pulp-urea system were
disappointing as feed intakes and growth rates were low (Phanthavong et al 2016b) apparently
because the cattle were averse to eating the cassava foliage. It became apparent that the
difference between the experiment of Ffoulkes and Preston (1978) in the Dominican Republic
and the initial studies in Laos was related to the source of the cassava which was a sweet
variety as grown for human consumption in the Dominican Republic (Ffoulkes and Preston
2


1978) compared with the “bitter” variety, which is used for commercial starch production in
Laos. As the names imply, levels of the cyanogenic glucosides, which on digestion in the
animal give rise to toxic hydrocyanic acid (HCN), are higher in bitter compared with sweet
varieties (Sarkiyayi and Agar 2010; Phuong et al 2012). Important steps forward were: (i) the
observation that cattle fed bitter cassava foliage had a “craving” to eat brewers’ grains
(Phanthavong 2016, unpublished observations); and (ii) the “craving” was explained by the
immediate improvement in growth rate (from 10 to 600 g/day) when 4% of brewers’ grains
was fed alongside the bitter cassava foliage accompanying the basal diet of cassava pulp-urea
(Binh et al 2017). It was shown that the brewers' grains apparently assisted in the
detoxification of the HCN precursors in bitter cassava foliage, as reflected in reduced
excretion of thiocyanate in the urine of the cattle fed the bitter cassava foliage (Binh et al
2017).
There are two altenatives for incorporating cassava foliage in the feeding system: (i)

growing cassava as a semi-perennial forage (eg: Preston and Rodriguez 2004; Phengvilaysouk
and Wanapat 2008) with repeated harvesting ar 8-12 week intervals (Vivasane et al 2017) and
feedng it in the fresh state withut processing (Keopaseuth and Preston (2917); or (ii)
preserving (or feeding directly) cassava leaves, petioles and fine stems collected immediately
prior to root harvest (Photos 2-5). It is estimated that the quantities of foliage available at root
harvest are of the order of 1,200 tonnes annually.

photo 2. The cassava
field ready for root
harvest

Photo 3. Harvesting
the foliage

Photo 4. The branch
Photo 5. Residual stems to
(tender stem, petioles
be used for planting the
and leaves) to be used as next cassava crop
animal feed

The following experiment was set up to evaluate the system in which the cassava foliage
was collected during the time of root harvest.

3


Materials and methods
Location and duration
The experiment was carried out in Natthana Chok Farm, Xaythany District, situated some

30 km from Vientiane Capital, from 14 January to 14 April 2018.
Treatments
The three feeding systems were based on the ingredients described in Tables 1 and 2.
Table 1. Composition of the experimental diets (% DM basis)
CMR

ECMR

CTL

Ensiled cassava pulp

46

46

46

Fresh brewers’ grains

4

4

30

Cassava foliage (bitter)

26

26

0

Rice straw

16

16

16

2.5

2.5

2.5

5

5

5

Salt

0.3

0.3

0.3

Sulphur

0.2

0.2

0.2

Supplements#
Urea
Rice bran

# Added before offering the feed

Table 2. Composition of diet ingredients
4


Cassava
pulp

DM, %

Brewers' Cassava foliage Rice
grains (bitter variety) straw

23.6

24.3

26.6

90.1

Ash

4.48

6.3

9.7

13.6

Crude protein

2.6

24.8

16.4

3.1

NDF

34.8

32.8

42.8

67.8

ADF

28.7

22.6

33.4

43.1

33.9

30.3

% in DM

N solubility#
# % N soluble in M NaCl

The treatments were:
CTL: The fattening system developed by Phanthavong et al (2016a), based on ad libitum
ensiled cassava pulp-urea, fresh brewers’ grains (1% of live weight, DM basis) and rice straw
(1 kg/day) (Table 1). The ingredients were given as separate feeds in the trough (without
mixing).

CMR: All the diet components (Table 1) were mixed together 18-24h before feeding.
ECMR: The ensiled cassava pulp, cassava foliage, brewers’ grains and rice straw (Table 1)
were mixed and ensiled in closed 100 liter plastic drums for 21 days prior to feeding.
For both CMR and ECMR, the urea, rice bran and minerals were added and mixed with the
feeds immediately prior to feeding.
Animals
Fifteen female local Yellow cattle with average age 2 years and mean initial weight 160
kg were housed in individual pens. There were five animals on each of the three treatments in
5


a completely randomized design. They were injected intramuscularly with Ivermectin (1ml/50
kg live weight) to control internal and external parasites.
Feeding system
The CMR diet was prepared daily, at about 3 pm, one day before being fed to the cattle.
For the ECMR diet the ingredients were mixed and ensiled in closed 100 liter plastic drums
for 21 days before feeding (Table 3).
The pH of the mixed feeds (ECMR and CMR) was taken after mixing, after 21 days of
ensiling (for ECMR) and immediately after adding the urea and minerals prior to feeding
(Table 4).
Midway through the experiment (after 45 days) samples were taken of the three diets
prior to feeding and stored frozen prior to analysis for the mycotoxin "Fumonisin".
Table 3. Chemical composition of experimental diets
CMR
DM,%
% in DM
Ash
Crude protein
Ether extract
NDF/p>

ADF

ECMR

CTL

25.4

27.4

29.5

8.7
16.7
2.6
39.0
27.8

9.8
114.4
00.9
441.6
339.6

6.2
14.2
1.4
41.3
29.9

Table 4. pH of completed mixed feeds prior to and after ensiling, and before feeding
(ECMR) and after mixing and before feeding, for CMR. Fumonisis was determined in
representative samples of feeds mid-way through the experiment
CTL

CMR

EMR

3.85

3.80

pH
After mixing
After ensiling

3.40

Prior to feeding
Mycotoxin
Fumonisin, ppm in DM

0.0425

3.75

3.30

0.538

0.0107

Measurements
The cattle were weighed before morning feeding at the beginning of the trial and every 14
days. Feeds offered and refused were recorded daily. After 90 days, at the end of the
experiment, rumen fluid samples were taken by stomach tube prior to acidification with
sulphuric acid for subsequent analysis of volatile fatty acids by gas chromatography (Samuel
6


et al 1997) and ammonia by Kjeldahl digestion (AOAC 1990). DM and crude protein in feeds
were analysed using the methods of AOAC (1990). Protein solubility was determined by the
method described in Whitelaw et al (1961). Fumonisin levels in feed samples were
determined following the method described by Pestkai et al (1994).

Statistical analysis
The data were analyzed as a Complete Randomized Design (CRD) using the general
linear model in the ANOVA program of the MINITAB (2000) software. Live weight gains
were determined from the linear regression of live weight (Y) on days in the experiment (X).

Results and discussion
Growth rates were decreased by 30% on the completely mixed rations compared with the
control diet with feeds given separately (Table 5; Figure 1). Feed intake was similar on the
three feeding systems with the result that the DM feed conversion ratio was also poorer on the
CMR/ECMR diets. On all three feeding systems the offer level exceeded the intake by a
margin of 14-19% but did not differ among feeding systems. Feed offered and not consumed
is an economic loss unless the residues are fed to other animals.

Table 5. Mean values for DM intake, initial and final live weights, live weight gain and feed

conversion for Yellow cattle fed cassava pulp-urea, cassava foliage, rice bran and rice straw as
complete mixed feed (CMR), as ensiled mixed feed (ECMR) or with the major feed ingredients
offered separately (CTL)
CMR

ECMR

CTL

SEM

p

Initial

181

188

172

5.18

0.15

Final

240

247

250

6.24

0.54

LW gain, g/d

622b

608b

857a

47.4

0.005

6.26

6.47

6.32

0.17

0.67

Live weight, kg

Feed DM, kg/d
Offered

7


Consumed

5.47

5.43

5.54

0.17

0.99

FCR

8.85 a

9.14 a

6.61 b

0.60

0.022

ab

Mean values without common superscript differ at p<0.05
FCR = Feed DM consumed per unit live weight gain

Figure 1. Comparative growth rates and DM feed conversion of Yellow cattle fed ensiled cassava pulp-urea,
and rice straw supplemented with brewers’ grains (CTL); or a completely mixed ration (CMR) of 46%
ensiled cassava pulp, 26% fresh cassava foliage and 4% brewers grains (all on DM basis); or the completely
mixed ration ensiled 3 weeks before feeding (ECMR). On all diets, urea and minerals were added
immediately before feeding.

Molar proportions of acetate were lower and those of butyrate higher in rumen fluid from
cattle fed the CTL diet compared with the completely mixed rations (Table 6). There was a
tendency (p=0.10) for the acetate: propionate ratio to be lower in rumen samples from cattle
fed the CTL diet.
Table 6. Mean values for rumen pH and VFA in cattle fed cassava pulp-urea,
cassava foliage and rice straw as complete mixed ration (CMR) or as ensiled
mixed ration (ECMR) or cassava pulp-urea, brewers’ grains and rice straw fed
separately (CTL)
CMR
ECMR
CTL
SEM
p
pH
Molar %

6.85

6.84

6.75

0.070

0.55

Acetate

71.3 ab

73.9 a

68.5 b

0.81

0.05

Propionate

15.85

15.93

15.59

0.25

0.84

ab

b

a

0.86

0.05

Butyrate

12.9

10.2

15.9

Discussion
There was a major difference between the CMR and CTL diets in the sources of protein
with cassava foliage (26%) and brewers’ grains (4%) in the CMR diets replaced by 30%
8


brewers’ grains in the control diet. This is not thought to be the reason for the differences in
performance as in a feeding trial with the same basal diets and breed of animals (but with
feeds that were not mixed), there were no differences in live weight gain between treatments
in which brewers’ grains were the sole source of protein (ADG 563g/d) compared with only

fresh cassava foliage as protein source (ADG 528g/d) (Keopaseuth and Preston 2017). When
cassava foliage was the sole source of protein in a cattle-fattening diet based on molassesurea, there were no benefits from replacing 50% of the cassava foliage with soybean meal
(Ffoulkes and Preston 1978).
The proportion of rumen-undegradable (or bypass) protein in brewers’ grains was
determined by Promkot and Wanapat (2005) to be 59%, only slightly higher that in cassava
hay (53%). These relative values can be compared with the solubility of the protein (Table 2)
which was 34 and 30%, respectively for brewers’ grains and cassava foliage. Protein
solubility is a good index of rumen protein bypass characteristics (Preston and Leng 1987).
There were only minor differences in the VFA pattern on the three diets (Table 6) and
thus were unlikely to affect the energy status of the products of fermentation.
The level of fumonisin detected in the ECMR (0.528 ppm) was considerably less than the
30 ppm considered to be the safe upper limit by the "Animal Nutrition Association of Canada
(ANAC)". The data nevertheless suggest that mycotoxin contamination is an issue to be taken
into consideration when using complete mixed feeds that are rich in protein and moisture, and
ensiled over an extended period prior to feeding.
It is suggested that the poorer performance of cttle fed the CMR and ECMR diets may
have been related to the known negative effect of the presence of cyanogenic glucosides in the
cassava foliage, which was of a “bitter” variety used exclusively for starch production. The
addition of the low level (4%) of brewers’ grains to the CMR diets was based on the findings
reported by Binh et al (2017) that this was an effective means of counteracting the potential
HCN toxicity associated with bitter cassava varieties. However, the cassava foliage (leaves
and petioles), used in the CRM diets, was obtained from cassava plants at the end of their
growth cycle immediately prior to, or coinciding with, root harvesting, which is done during
the dry season. Dry season conditions lead to soil water stress which is known to result in
increased concentrations of HCN precursors in the cassava foliage (Tan 1985).
The results of the present experiment confirm that local "Yellow" cattle can be fattened on
the byproduct pulp from cassava-starch factories using urea as source of rumen ammonia and
cassava foliage as the main source of bypass protein, derived by recovering the leaves,
petioles and fine stems available at the time of root harvest. These findings complement those
of Keopaseuth and Preston (2017) using cassava foliage grown specifically as a forage crop to

9


balance the cassava pulp-urea, but with these feeds offered separately. Growth rates (650g/d)
were similar to those obtained in the present experiment with the cassava foliage collected at
the time of root harvest and used in the .CMR and ECMR systems. In both these cases,
brewers' grains were fed in limited amounts of 1 kg/d fresh basis (equivalent to 4% of the diet
DM basis). Choice of either of these two systems of using cassava foliage will depend on the
economic feasibility of collecting and preserving cassava foliage (tender stems, leaves and
petioles) harvested immediately prior to the root harvest (Photos 2-5), as opposed to growing
cassava foliage as a semi-perennial forage, or the purchase of brewers' grains as protein
cource.
The final issue concerns the relevance, from a management perspective, of CMR systems
compared with offering the feed ingredients separately. CMR systems undoubtedly have
advantages in large scale feedlots where feeder wagons enable major savings in costs
compared with hand feeding. But at small and medium scales of operation the CMR system
may be more, not less, labor-intensive. The moderate degree of contamination with the fungal
fumonisin in the ensiled complete mixed ration indicates that ensiling of a complete mixed
feed may not be the way to manage high moisture forage-based feeds under humid tropical
conditions. Preparing the CMR immediately before, or some hours prior to, feeding would
appear to be a more appropriate system.

Conclusions


Growth rates of local Yellow cattle were 622 and 608 g/day when a diet of ensiled
cassava pulp, supplemented with urea, cassava foliage (leaves and petioles), brewers’
grains and rice straw, was fed as a completely mixed ration in fresh form or after
ensiling for 21 days. Live weight gains were 857 g/day when almost all the protein
was in the form of brewers’ grains, and the ingredients were not mixed (apart from the

urea which was dissolved in the cassava pulp at the time of feeding).



It is suggested that excessively high levels of cyanogenic glucosides in the cassava
leaves and petioles, which were collected at the end of the dry season from a “bitter”
cassava variety at the time of root harvest, may have contributed to the poorer
performance of the cattle fed the CMR diets.

Acknowledgements
This research was done by the senior author as part of the requirements for the PhD
degree in Animal Production of Hue University of Agriculture and Forestry, Vietnam. The
authors acknowledge support for this research from the MEKARN II project “"Improving
Livelihood and Food Security of the people in Lower Mekong Basin through Climate Change
10


Mitigation", financed by Sida. The authors are indebted to Mr. Vakili Vongxay, owner of the
Natthanasouck farm where the experiment was carried out, for providing access to cattle, feed
resources and infrastructure. The Tropical Feed Resources Research and Development Center
(TROFEC) of Khon Kaen University is acknowledged for support in collection of rumen
samples and VFA analysis. We thank Dr Bundit Tengjaroenkul, Faculty of Veterinary
Medicine, Khon Kaen University for analysis of fumonisin in feed samples.

References
AOAC 1990 Official methods of analysis. 15th ed. AOAC, Washington, DC
Binh P L T, Preston T R, Duong K N and Leng R A 2017 A low concentration (4% in diet
dry matter) of brewers’ grains improves the growth rate and reduces thiocyanate excretion of
cattle fed cassava pulp-urea and “bitter” cassava foliage. Livestock Research for Rural
Development. Volume 29, Article #104. />Ffoulkes D and Preston T R 1978 Cassava or sweet potato forage as combined sources of

protein and roughage in molasses-based diets: effect of supplementation with soybean meal.
Tropical Animal Production, Volume 3, Number 3 pp186192 />Keopaseuth T and Preston T R 2017 Cassava (Manihot esculenta Cranz) foliage replacing
brewer’s grains as protein supplement for Yellow cattle fed cassava pulp-urea and rice straw;
effects on growth, feed conversion and methane emissions. Livestock Research for Rural
Development. Volume 29, Article #35. />MAF 2016 Ministry Agriculture and Forestry Development Strategy 2025 and vision 2030.
Vientiane Capital: Ministry of Agriculture and Forestry (MAF).
MINITAB 2000 Minitab user's guide. Data analysis and quality tools. Release 13.1 for
windows. Minitab Inc., Pennsylvania, USA.
Phanthavong V, Khamla S and Preston T R 2016a Fattening cattle in Lao PDR with
cassava pulp. Livestock Research for Rural Development. Volume 28, Article
#10 />Phanthavong V, Preston T R, Viengsakoun N and Pattaya N 2016b Brewers' grain and
cassava foliage (Manihot esculenta Cranz) as protein sources for local “Yellow” cattle fed
cassava pulp-urea as basal diet. Livestock Research for Rural Development. Volume 28,
Article #196. />Phanthavong V, Sangkhom I, Preston T R, Dung D V and Ba N X 2018 Effect of leaves
from sweet or bitter cassava and brewers’ grains on methane production in an in vitro rumen
incubation of cassava root pulp-urea. Livestock Research for Rural Development. Volume 30,
Article #167. />Phanthavong V, Viengsakoun N, Sangkhom I and Preston T R 2014 Cassava pulp as
livestock feed; effects of storage in an open pit. Livestock Research for Rural Development.
Volume 26, Article #169. />11


Phengvilaysouk A and Wanapat M 2008 Study on the effect of harvesting frequency on
cassava foliage for cassava hay production and its nutritive value. Livestock Research for
Rural Development. Volume 20,
supplement. />Phuong L T B, Preston T R and Leng R A 2012 Effect of foliage from “sweet” and “bitter”
cassava varieties on methane production in in vitro incubation with molasses supplemented
with potassium nitrate or urea. Livestock Research for Rural Development. Volume 24,
Article #189. />Preston T R and Leng R A 1987 Matching Ruminant Production Systems with Available
Resources in the Tropics and Sub-Tropics. />Preston T R and Rodríguez Lylian 2004 Production and utilization of cassava foliage for
livestock in integrated farming systems. Livestock Research for Rural Development. Volume

16, Art. No. 28. />Samuel M S, Sagathewan J T and Mathen G 1997 An HPLC method for estimation of
volatile fatty acids of rumen fluid. Indian J. Anim. Sci. 67:805–807.
Sarkiyayi S and Agar T M 2010 Comparative Analysis on the Nutritional and AntiNutritional Contents of the Sweet and Bitter Cassava Varieties. Advance Journal of Food
Science and Technology 2(6): 328-334
Tan S L 1995 Factors affecting cyanide content in cassava (Manihot esculenta Crantz).
MARDI Research Journal 23 (2), 121–131
Vivasane S, Do H Q and Preston T R 2017 Effect of different harvesting intervals on foliage
yield and chemical composition of cassava (Manihot esculenta Crantz). Livestock Research
for Rural Development. Volume 29, Article
#162. />Whitelaw F G, Preston T R and Dawson G S 1961 The nutrition of the earlyweaned calf. II.
A comparison of commercial groundnut meal, heat-treated groundnut meal and fish meal as
the major protein source in the diet. Animal Production, 3, pp 127-133 doi:
10.1017/S0003356100033882

Received 30 June 2018; Accepted 11 September 2018; Published 1 October 2018
Go to top

12