The Nutritive Value and Fermentative Quality of Different Inclusion Level of Sweet Potato Vine in Napier Grass Silage

Abstract

Napier grass, NG is well known a s a feedstuff for ruminants for its high crude protein value when harvested at its recommended age, 6 to 8 weeks old. Potato vine, SPV is Meanwhile, Sweet considered as crop waste due to underutilization regardless of it potential nutritional value. s This neglection of Sweet Potato vine happened due to lack of interest to further process the vine as a feedstuff. This research was conducted to evaluate the chemical composition and physical properties of various inclusion level of Sweet Potato vine in en siling Napier grass with 0.3% molasses for 30 days. The treatments were 100%NG, 75%NG:25%SPV, 50%NG:50%SPV, 25%NG:75%SPV and 100%SPV. Common Napier grass and Bukit Naga Sweet Potato vines were used in this research. The forages were harvested at 6 weeks ol d on the second harvesting cycle. The physical properties of silages such as colour and pH were analysed to determine the silage quality. All of the treatments showed an optimum pH for a good silage which is 3.5 to 4.0. The colour evaluation for all the tr identifiable structure. eatments was greenish brown with The chemical composition of the treatments was determined by using proximate analysis procedures. 100%SPV had the highest crude protein content compared to other treatments ( 17.56±0. 33). Overall fiber value, 100%NG had the highest content.

Full text

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The Nutritive Value and Fermentative Quality of Different Inclusion Level of
Sweet Potato Vine in Napier Grass Silage
BY:
SAFWAH NAJIHAH BAHARIN
(189556)
FACULTY OF AGRICULTURE
UNIVERSITI PUTRA MALAYSIA
2019/2020

CERTIFICATION
This project report entitled “The Nutritive Value and Fermentative Quality of Different
Inclusion Level of Sweet Potato Vine in Napier Grass Silage” was prepared by Safwah
Najihah Binti Baharin and submitted to the Faculty of Agriculture in fulfilment the
requirement of SHW 4999 (Final Year Project) for the award of the degree of Bachelor
of Agriculture (Animal Science).
Student’s Signature : ………………………………
Student’s Name : Safwah Najihah binti Baharin
Matric No. : 189556
Certified by :
……………………………………
Dr. Shokri bin Jusoh,
Project Supervisor,
Department of Animal Science,
Faculty of Agriculture,
Universiti Putra Malaysia.
Date :

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ACKNOWLEDGEMENT
First of all, all praise to Almighty Allah S.W.T for blessing me with strength and
patience to complete this final year project thesis. I would like to express my deepest
gratitude to my supportive project supervisor, Dr. Shokri bin Jusoh, for his time and
guidance.
Next, I would like to thank my beloved parents, Mr. Baharin bin Rahaman and
Mrs. Aminah binti Khamis for their great support and blessings. I also would like to thank
to my friends for their help in completing this project. Especially, those whom
contributed their strength and time in planting and harvesting the materials, Serdang
Angel’s rugby players, Ms. Alyaa Husna Ab. Rahman, Ms. Shahida Izami Samsul Ikram
and Ms. Saidatul Atirah Sumidi.
Next, I would like to gratitude the supportive staffs, Mr. Mohd Faizal Yeop
Baharuddin from Farm 15 and Mrs. Ezazura Abdul Rahim and Mr, Khairul Anwar Bahari
from Nutrition Laboratory for their willingness to help and guide me. Lastly, thank you
to to all who directly and indirectly involved in completing this final year project

ABSTRACT
Napier grass, NG is well known as a feedstuff for ruminants for its high crude protein
value when harvested at its recommended age, 6 to 8 weeks old. Meanwhile, Sweet
Potato vine, SPV is considered as crop waste due to underutilization regardless of its
potential nutritional value. This neglection of Sweet Potato vine happened due to lack of
interest to further process the vine as a feedstuff.
This research was conducted to evaluate the chemical composition and physical
properties of various inclusion level of Sweet Potato vine in ensiling Napier grass with
0.3% molasses for 30 days. The treatments were 100%NG, 75%NG:25%SPV,
50%NG:50%SPV, 25%NG:75%SPV and 100%SPV. Common Napier grass and Bukit
Naga Sweet Potato vines were used in this research. The forages were harvested at 6
weeks old on the second harvesting cycle.
The physical properties of silages such as colour and pH were analysed to determine the
silage quality. All of the treatments showed an optimum pH for a good silage which is
3.5 to 4.0. The colour evaluation for all the treatments was greenish brown with
identifiable structure.
The chemical composition of the treatments was determined by using proximate analysis
procedures. 100%SPV had the highest crude protein content compared to other
treatments (17.56±0.33). Overall fiber value, 100%NG had the highest NDF, ADF and
ADL content.

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ABSTRAK
Rumput Napier, NG terkenal sebagai makanan haiwan ruminan yang mempunyai
nilai protein yang tinggi apabila dituai pada usia yang optimum iaitu pada minggu ke-6
hingga ke-8 penanaman. Manakala, daun ubi keledek, SPV sering dibuang walaupun
mempunyai nilai nutrisi yang tinggi. Hal ini disebabkan pengusaha ubi keledek hanya
memfokuskan pengeluaran ubi keledek berbanding sekaligus memproses daun ubi
keledek sebagai bahan makanan ternakan.
Kajian ini telah dijalankan bertujuan untuk menilai komposisi nutrisi dan nilai pH
silaj rumput Napier ditapai dengan pelbagai tahap campuran daun ubi keledek dan 0.3%
molas selama 30 hari. Nilai campurannya ialah 100%NG, 75%NG:25%SPV,
50%NG:50%SPV, 25%NG:75%SPV dan 100%SPV. Rumput Napier variasi Common
dan Keledek Bukit Naga berusia 6 minggu pada kitaran tuai kedua telah digunakan bagi
kajian ini.
Nilai pH telah dianalisa untuk menentukan kualiti silaj. Kesemua rawatan telah
menunjukkan pH yang optimum untuk silaj yang baik iaitu 3.5 ke 4.0. Penelitian warna
juga telah dilakukan dan dapatan menunjukkan kesemua rawatan berwarna coklat
kehijaun dengan struktur fizikal yang masih boleh dikenal pasti.
Komposisi nutrisi telah dianalisa menggunakan prosedur ‘proximate analysis’.
100%SPV mempunyai kandungan protein yang paling tinggi berbanding rawatan yang
lain (17.56±0.33). Bagi nilai serat secara keseluruhan, 100%NG mempunyai nilai NDF,
ADF dan ADL yang paling tinggi.

TABLE OF CONTENTS
CHAPTER 1 ..................................................................................................................... 1
INTRODUCTION ............................................................................................................ 1
1.1 Problem statement ....................................................................................................... 2
1.2 Objectives .................................................................................................................... 2
1.3 Hypothesis .................................................................................................................. 2
1.4 Significance of the Study............................................................................................ 2
CHAPTER 2 ..................................................................................................................... 3
LITERATURE REVIEW ................................................................................................. 3
a)Napier grass, Pennisetum purpureum ........................................................................... 3
b)Sweet potato vines, Ipomoea batatas ............................................................................ 4
c)Mixture of ensiled Napier grass, NG and Sweet potato vines, SPV ............................. 4
d)Ensiling ......................................................................................................................... 5
CHAPTER 3 ..................................................................................................................... 6
MATERIALS AND METHOD ....................................................................................... 6
3.1 Study Design .............................................................................................................. 6
3.2 Location ...................................................................................................................... 6
3.3 Subjects....................................................................................................................... 6
3.4 Sample Size ................................................................................................................ 6
3.5 Experimental Procedure ............................................................................................. 7
CHAPTER 4 ................................................................................................................... 10
RESULTS AND DISCUSSION..................................................................................... 10
4.1 Ensiling effect on Napier grass and Sweet potato vine ............................................ 10
4.1.1 The effect of ensiling on the DM content of the fodders ...................................... 10
4.1.2 The effect of ensiling on the OM content of the fodders ...................................... 12
4.1.3 The effect of ensiling on the CP content of the fodders ........................................ 13
4.1.4 The effect of ensiling on the EE content of the fodders ........................................ 14
4.1.5 The effect of ensiling on the fiber content of the fodders ..................................... 15
4.2 The effect of different inclusion level of SPV in ensiling NG ................................. 17
4.2.1 The effect of different inclusion level on the DM and pH value of the silages .... 17
4.2.2 The effect of different inclusion level on the OM value of the silages. ................ 19
4.2.3 The effect of different inclusion level on the CP value of the silages. .................. 20
4.2.4 The effect of different inclusion level on the EE value of the silages. .................. 22

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4.2.5 The effect of different inclusion level on the fiber content of the silages. ............ 23
CHAPTER 5 ................................................................................................................... 25
CONCLUSION .............................................................................................................. 25
REFERENCES ............................................................................................................... 26
APPENDICES ................................................................................................................ 28

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CHAPTER 1
INTRODUCTION
Napier grass, Pennisetum purpureum is commonly used in Malaysia as a
livestock feedstuff since its nutrient content and planting management is well practised
by livestock farmers. It is best been utilized at 6-8 weeks of growth to optimise the dry
matter yield and nutritive value (Lounglawan et al., 2014). Napier grass aged more than
8 weeks old contains low digestibility rate due to lignocellulosic material. Nevertheless,
too young Napier grass which below than 6 weeks old contains poor dry matter content
though the crude protein is high (Zailan et. al., 2016). Prior to this maturity constraint
that adversely affect the nutritional value of Napier grass, ensiling is always been carried
out to conserve its nutrient content.
Meanwhile, Sweet potato, Ipomoea batatas is mainly cultivated for food as a root
crop (Ruiz et. al., 1981). Malaysia planned to expand another 300 hectare of Sweet potato
plantation to fulfil the demand of its tuber (DAN, 2011). Sweet potato vine is considered
as crop waste due to underutilization regardless of its potential protein content (Phuc,
2000 and Dung, 2001). This is due to farmer lack of interest to efficiently utilized crop
residue as a feed production. Sweet potato is a hardiness plant harvest as it can tolerate
to harvesting up to 4 times per growing season and can be preserved by ensiling (Lebot,
2009).
Silage is the feed material produced by a successful anaerobic fermentation. The
production of silage is important in region where animals are unable to obtain the
required energy or nutrient throughout the year from grazing due to unfavourable climate
where hay production is restricted (McDonald et. al., 2010).

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1.1 Problem statement
Good quality silage can be made from SPV due to their high crude protein content, high
digestibility and palatability as a livestock feed. However, due to insufficient quantities
of SPV for sole ensiling (Kabirizi et al., 2015), there is need to explore the possibility of
making silage from a mixture of SPV and Napier. Hence, inclusion effects of SPV along
with Napier grass in Malaysia is yet to be documented.
1.2 Objectives
The general objective of this study is;
To determine the different inclusion ratio effect of Sweet potato vines in ensiling Napier
grass for a production of a better chemical composition of silage.
The specific objectives of this study are;
1. To evaluate the silage quality through pH and colour of ensiled Napier grass and Sweet
potato vine.
2. To determine the content of dry matter, crude protein, ether extract, neutral detergent
fiber, acid detergent fiber of the silage.
1.3 Hypothesis
Better silage quality can be achieved with an optimum ratio of Sweet potato, Ipomoea
batatas vine in ensiling Napier grass, Pennisetum purpureum.
1.4 Significance of the Study
Sweet potato vines as feedstuff can be supplemented to livestock in Malaysia to exploit
the nutritional value of this underutilized crop by-product.

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CHAPTER 2
LITERATURE REVIEW
a) Napier grass, Pennisetum purpureum
Napier grass, Pennisetum purpureum has been the promising and high yield grass, giving
dry matter yield that surpasses most other tropical grasses, like Guinea grass and Rhodes
grass. It also has a higher nutritive value compared to Brachiaria species (Gomez et al.,
2011). Napier grass can produce more dry matter per unit area than any other crop but,
the total digestible nutrient, TDN will decline with advancing maturity age. The reduction
of digestibility as the harvesting age increases is related to lignin content in the mature
plant (Zailan et al., 2016). The recommended age to harvest Napier is at 6-8 weeks of
growth to optimise the dry matter yield and nutritive value (Lounglawan et al., 2014).
Prior to this maturity constraint that adversely affect the nutritional value of Napier grass,
ensiling is always been carried out to conserve its nutrient content. Napier grass can be
propagated through seeds, however as seed production is inconsistent, collection is
difficult. As an alternative, it can be propagated vegetatively by stem cuttings or stolons.
After planting, Napier grass grows vigorously and can reach 4 m in 3 months (Skerman
and Riveros, 1990). Napier grass can be planted as monocrop and be intercropped with
legumes or other fodder trees (Burton, 1993). Thus, in this study, the Napier grass will
be intercropped with Sweet potato plant. Napier grass and Sweet potato vines are
characterised by low dry matter content, low water-soluble carbohydrates (WSC) and
high buffering capacity due to the high crude protein content at early stages of maturity
(Bureenok et al., 2012) which in turn makes it difficult to achieve good silage when these
materials are ensiled alone. Furthermore, high moisture content of pre-ensiled materials
facilitates the activity of undesirable silage spoilage microbes like clostridia and

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enterobacteria which are associated with poorly preserved silage (McDonald et. al.,
1991).
b) Sweet potato vines, Ipomoea batatas
Sweet potato is a traditional crop that is still popular in Malaysia, especially in rural areas.
Sweet potato production in 2017 is in third place after sweet corn and tapioca production.
The hectarage of sweet potato by state from 2013-2017 is mainly in Perak, followed by
Kelantan and Selangor (DOA, 2017). Nonconventional feedstuff resources, NCFR refer
to all those feeds that have not been traditionally used in animal feeding and are not
normally used in commercially produced rations for animals (Devender, 1985). Sweet
potato vine (SPV) is one of NCFR which is a by-product from sweet potato production
and also is a valuable forage for ruminants and other livestock species (Giang et. al.,
2004). At 6 to 8 weeks old, Sweet potato vine contains high crude protein, 18% and high
nitrogen-free extract, 44.6%. (DVS, 2005). Nevertheless, a large amount of these by-
products is wasted due to their high perishability. Thus, its potential value as livestock
feed resources is neglected. These potential nutrients can be conserved in ensiling.
c) Mixture of ensiled Napier grass, NG and Sweet potato vines, SPV
The highest crude protein level is attained by the inclusion level of 50% SPV in ensiling
Napier grass. However, this mixture produced the least amount of neutral detergent fiber,
acid detergent fiber and ether extract (Lutwama et. al., 2016). There is no other inclusion
level between NG and SPV being measured except for the ratio of 50NG:50SPV. Thus,
in this research, the addition of 75%NG: 25%SPV and 25%NG: 75% SPV inclusion level
were analysed and documented.

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d) Ensiling
The activities of undesirable microorganisms such as clostridia and enterobacteria can be
inhibited by achieving anaerobic fermentation. In practice, this is done by cutting the
crop during harvesting, immediately filling the silo and providing airtight containment.
Proper containment can minimize oxygen content during storage. Hence, it can reduce
the oxidation rate for preservation and undesired aerobic microbial activity of the ensiled
material. (McDonald et. al., 2010).

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CHAPTER 3
MATERIALS AND METHOD
3.1 Study Design
A completely randomized design (CRD) was used to study the effects of five (5) different
treatments, 100% Napier grass as control; 75% Napier grass: 25% Sweet potato vines;
50% Napier grass: 50% Sweet potato vines; 25% Napier grass: 75% Sweet potato vines
and 100% Sweet potato vines on the silage quality.
3.2 Location
The forage preparation and sample collection were carried out at Farm 15, UPM. While
the laboratory analysis was conducted at Nutrition Laboratory of Department of Animal
Science, Faculty of Agriculture, UPM.
3.3 Subjects
The treatments were tested on the second cycle of harvesting at which the Napier grass
and Sweet potato vines were 6 weeks old.
3.4 Sample Size
The materials were ensiled with 0.3% molasses for 30 days in 1kg airtight plastic
container according to the designated treatments. Each treatment was replicated 3 times,
which in total, 15 transparent plastic containers were used throughout the research.

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3.5 Experimental Procedure
3.5.1 Material preparation
3.5.1.1 Forage preparation
Both Napier grass, NG and Sweet potato vine, SPV were intercropped and planted
vegetatively at Farm 15. Hence, no seed was used for forage preparation. Napier grass
was planted from stem cutting whilst Sweet potato vine was planted from vines. Both
Napier grass and Sweet potato vines were harvested on the second cycle of harvesting at
which the Napier grass and Sweet potato vines were 6 weeks old.
3.5.1.2 Ensiling
Harvested Napier grass and Sweet potato vines were chopped into 2 to 4 cm length to
increase the fermentative surface area and aided in compaction for air exclusion purpose.
The forage then was wilted under the Sun for 4 hours. Both wilted NG and SPV were
weighed and ensiled with 0.3% of molasses in 1kg transparent container plastic with ratio
according to each designated treatment for 30 days.
3.5.2 Data analysis and interpretation.
3.5.2.1 Determination of physical properties.
a) Colour
The colour was observed.
b) pH-value
25g silage sample was weighed and mixed with 25ml distilled water in a plastic
container. The solution was then be shaken vigorously and the pH was analysed by
using a calibrated pH electrode meter.
3.5.2.2 Determination of chemical properties
a) Dry matter determination

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2 to 5 g of ground sample was weighed and placed in the pre-weight crucible. The
sample then was air-dried in the 105℃ oven for 24 hours. The weight of the dried
sample was recorded and calculated by using this formula:
% of dry matter = ( weight of sample before drying−weight of sample after drying)
weight of sample before drying x 100
b) Organic matter determination
The sample from previous dry matter testing was used and undergone further
combustion. The sample was transferred into 550℃ muffle furnace for 4 hours. The
last result which was in the form of ash was weighed.
c) Crude protein determination
The crude protein (CP) content of the mixture was analyzed by using Kjeldahl method,
(AOAC, 1990)
d) Ether extract determination
The lipid content in the mixture was determined by using Soxhlet apparatus. The
extracted lipid was calculated by using this formula:
% of ether extract: ( weight of tin contained extracted lipid−weight of empty tin)
weight of sample X 100
e) Fiber determination
Van Soest’s method (was used in determining non-detergent fiber, NDF; acid
detergent fiber, ADF and acid detergent lignin, ADL; of each designated treatment.
3.5.2.3 Statistical analysis
Analysis of variance (ANOVA) was used to test for statistical significance of each
treatment on silage chemical composition and fermentative characteristics using
the PROC GLM procedure of SAS. When the F test indicated a significant
difference (P<0.05) due to type of material used in silage making, the LSMEANS

9
statement was used to separate the least square means using the PDIFF option of
SAS. Post hoc test which is Tukey Multiple Range Test from SAS software was
used to verify the significance level (SAS, 2012)

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CHAPTER 4
RESULTS AND DISCUSSION
4.1 Ensiling effect on Napier grass and Sweet potato vine
4.1.1 The effect of ensiling on the DM content of the fodders
Figure 1 shows the dry matter, DM of pre-ensiled and ensiled for both Napier grass and
Sweet potato vine.
Pre-ensiled NG shows significantly lower content (P<0.05) than ensiled NG,
same goes with SPV. This is because before ensiling, the forages were wilted under the
Sun for 4 hours until the DM content reaches 30% and the way to determine it on the
field is by handheld the forages. The forages should leave no moist on the hand and back
to its origin shape. This is contradicting with the studies done by Lutwama et. al., (2016)
and Yokota et. al., (1992) where they found that ensiling can reduce DM content. The
reason behind it is that microorganisms ferment the naturally occurring sugars within
25.74 26.40 31.04 31.29
20
22
24
26
28
30
32
PE-NG E-NG PE-SPV E-SPV
%
DM
d
c
ba
Figure 1: DM content of pre-ensiled and ensiled for both forages
PE-NG: Pre-ensiled Napier grass; E-NG: Ensiled Napier grass
PE-SPV: Pre-ensiled Sweet potato vine ; E-SPV: Ensiled Sweet potato vine
abcd: different alphabet in the same row showed significant different by Tukey Test (P<0.05)

11
the forages for their metabolic activity (McDonald et. al., 2010). DM content in ensiled
forages is higher than pre-ensiled forages in this study is believed affected by the usage
of 0.3% of molasses.

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4.1.2 The effect of ensiling on the OM content of the fodders
Figure 2 shows the organic matter, OM of pre-ensiled and ensiled for both Napier grass
and Sweet potato vine.
From the graph above, both pre-ensiled and ensiled forages show no significant
difference in intra-species but there is a significant difference in inter-species. OM value
was determined by ash content obtained by removing the moisture and minerals in the
treatments. Ash indicated the minerals content in the mixture as minerals usually have
almost similar amount of ash content. This shows that ensiling has no significant effect
on the ash content for both forages.
6.59 5.35 9.14 7.62
0
2
4
6
8
10
PE-NG E-NG PE-SPV E-SPV
% on DM basis
OM % on DM basis
b
b
a
a
Figure 2: OM content of pre-ensiled and ensiled for both forages
PE-NG: Pre-ensiled Napier grass; E-NG: Ensiled Napier grass
PE-SPV: Pre-ensiled Sweet potato vine ; E-SPV: Ensiled Sweet potato vine
ab: different alphabet in the same row showed significant different by Tukey Test (P<0.05)

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4.1.3 The effect of ensiling on the CP content of the fodders
Figure 3 shows the crude protein, CP of pre-ensiled and ensiled for both Napier grass
and Sweet potato vine.
From the graph above, ensiled NG shows significantly lower content of CP
(P<0.05) than pre-ensiled NG, same goes with SPV. This shows that ensiling has a
significant effect on the CP content for both forages. The possible reason for reduced in
CP in ensiling is the evidence of proteolysis activity during fermentation that produces
NH3. Furthermore, proteolytic activity from plant protease occurs more extensively
during the anaerobic fermentation process (Baron et. al., 1986) Crude protein mainly
consists of nitrogenous compound for which the proteolytic organisms able to transform
proteins to such products as ammonia, amino acids, amines, and amides. These
metabolic waste products will be formed in greatest quantity when the nitrogen
requirements of the organisms are lowest. Hence, reduction in CP during ensiling occurs
when the organism is using protein as an energy source as well as for the synthesis of
cell substance (Bender et. al., 1939).
13.23 9.70 24.27 17.56
0
5
10
15
20
25
30
PE-NG E-NG PE-SPV E-SPV
% on DM basis
CP % on DM basis
d
c
b
a
Figure 3: CP content of pre-ensiled and ensiled for both forages
PE-NG: Pre-ensiled Napier grass; E-NG: Ensiled Napier grass
PE-SPV: Pre-ensiled Sweet potato vine ; E-SPV: Ensiled Sweet potato vine
abcd: different alphabet in the same row showed significant different by Tukey Test (P<0.05)

14
4.1.4 The effect of ensiling on the EE content of the fodders
Figure 4 shows the ether extract, EE of pre-ensiled and ensiled for both Napier grass and
Sweet potato vine.
From the graph above, ensiled NG shows significantly lower content of EE
(P<0.05) than pre-ensiled NG, same goes with SPV. EE content is the lipid content in the
forages. Lipid oxidation is influenced by the lipoxygenases activity that found in a plant
at all growth stages, predominantly at maturing stage. Almost all of the total fat in fresh
forage is in the form of esterified fatty acids, whereas in silage, a large proportion is in
the form of free fatty acids which then further oxidized by lipoxygenases (Elgersma et.
al., 2003). Free fatty acid is susceptible to oxidation during ensiling which can be related
to the pH changes occurred during ensiling. Lipoxygenases activity is plausible in high
pH and is inhibited by low pH. Furthermore, lipoxygenases required aerobic condition
whereas ensiling is the process progress from aerobic to anaerobic condition resulting
the decline of lipoxygenases activity (Lourenco et. al., 2005, Zhong and Glatz, 2006).
Hence, EE content of ensiled forages are reduced.
3.60 2.51 3.84 3.20
0
1
2
3
4
PE-NG E-NG PE-SPV E-SPV
% on DM basis
EE % on DM basis
a
c
b
a
Figure 4: EE content of pre-ensiled and ensiled for both forages
PE-NG: Pre-ensiled Napier grass; E-NG: Ensiled Napier grass
PE-SPV: Pre-ensiled Sweet potato vine ; E-SPV: Ensiled Sweet potato vine
abc: different alphabet in the same row showed significant different by Tukey Test (P<0.05)

15
4.1.5 The effect of ensiling on the fiber content of the fodders
Figure 5 shows the fiber content of pre-ensiled and ensiled for both Napier grass and
Sweet potato vines that were determined by Van Soest’s Analysis.
From the graph above, ensiling has no significant difference on hemicellulose,
cellulose and lignin content for both forages. However, there is significant difference on
cellulose content for both ensiled forages. This is contradicting with the research done
by Lutwama et. al., (2016) where they found that ensiling can significantly reduce the
hemicellulose content. It may be due to the incorporation of 0.3% molasses in ensiling
the forages in this study. Molasses contains high water-soluble carbohydrate in which
microorganisms able to consume for their metabolic activity and producing acids. That
is why the hemicellulose and cellulose content of the forages were not significantly
affected by ensiling.
PE-NG E-NG PE-SPV E-SPV
Hemicellulose 27.22 25.68 23.74 22.63
Cellulose 46.97 44.48 34.41 30.9
Lignin 1.44 0.97 0.78 0.61
0
5
10
15
20
25
30
35
40
45
50
% on DM basis
Van Soest's Analysis
a
ab
b
a
a
b
b
b
bb
a
Figure 5: The Van Soest’s Analysis of pre-ensiled and ensiled forages
PE-NG: Pre-ensiled Napier grass; E-NG: Ensiled Napier grass; PE-SPV: Pre-ensiled Sweet potato vine;
E-SPV: Ensiled Sweet potato vine
ab: different alphabet in the same row showed significant different by Tukey Test (P<0.05)

16
The composition of the dry matter is dependent on the relative proportions of cell
walls and cell contents. The cell walls consist of cellulose and hemicelluloses, reinforced
by lignin. The cellulose content is generally within the range of 200–300 g/kg DM
whereas hemicelluloses may vary from 100 g/kg to 300 g/kg DM. The concentrations of
both these polysaccharide components increase with maturity so does that of lignin,
which reduces the digestibility of the polysaccharides (McDonald et. al., 2010).
Hemicellulose content is obtained by subtracting ADF from non-detergent fiber, NDF
whereas cellulose content is obtained by subtracting ADL from acid detergent fiber,
ADF. Lignin proportion is the acid detergent ligin, ADL content.

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4.2 The effect of different inclusion level of SPV in ensiling NG
4.2.1 The effect of different inclusion level on the DM and pH value of the silages
Figure 6 below shows the dry matter content and the pH value of all treatments.
In term of Dry matter (DM) content, all the treatments are significantly difference.
The 100%NG shows the lowest DM whilst 100%SPV shows the highest DM. DM
contains both organic and organic material of the plant except water content. During
ensiling, microorganisms such as lactic acid bacteria ferment the naturally occurring
sugars present in the plant such as glucose and fructose and produce a mixture of acids,
but predominantly lactic acid. The acids produced increase the hydrogen ion
concentration to a level at which the undesirable microorganisms are inhibited to do their
metabolic activity (McDonald et. al., 2010). Thus, pH drop within a good range in
ensiling is a desired criteria.
100NG 75NG:25SPV 50NG:50SPV 25NG:75SPV 100SPV
DM 26.40 27.71 28.97 29.96 31.29
pH 3.47 3.60 3.66 3.69 3.87
0
4
8
12
16
20
24
28
32
%
Inclusion Level
The difference between DM and pH of ensiled forages
d
ecba
cb b ba
Figure 6: The difference between DM and pH of ensiled forages
DM: Dry matter; pH: Concentration of hydrogen ion
abcde: different alphabet in the same row showed significant different by Tukey Test (P<0.05)

18
In term of pH value, treatment of 75%NG, 50%NG and 25%NG has no
significant difference (P> 0.05). However, when compared with treatment of 100%NG
and 100%SPV, a significant difference (P< 0.05) can be seen (Figure 2). 100%NG shows
the lowest and 100%SPV shows the highest pH. Overall, the treatments show an
optimum pH value of good silage.
The desired microorganism in ensiling is lactic acid bacteria which favours
anaerobic condition. The optimum pH for silage preservation is between 3.5 to 4.0. When
the pH of the mass drops to 3.5, the rate of cell respiration is reduced to 10%, resulting
in less oxygen production during ensiling. The harmful aerobic bacterial action which
gives rise to the formation of butyric acid is completely inhibited at a pH below 4
(McDonald et. al., 2010). Thus, anaerobic condition could be maintained for a longer
period.
Ensiling of forage is intended to preserve forage nutrient quality through the
production of lactic acid which inhibit activity of aerobic microbes in silage which are
known to result into silage DM losses. The pH of silage is significantly dependent on
the DM content of the ensiled material (Woolford & Pahlow, 1998). This explains why
the ensiled material with the highest DM had the greatest differences or changes in pH.

19
4.2.2 The effect of different inclusion level on the OM value of the silages.
Figure 7 below shows the organic matter content of all treatments.
The graph above shows that even a slight incorporation of SPV in ensiling NG
can significantly (P<0.05) increase the OM content. OM value was determined by ash
content obtained by removing the moisture and minerals in the treatments. Ash indicated
the minerals content in the mixture as minerals usually have almost similar amount of
ash content. It can only tell the amount of the mineral not the type of the mineral.
Contamination of silage can increase the pH of silage and it usually happen due
to soil contamination. Soil contains silica, a mineral that is indigestible by rumen
microbes. Meanwhile, mineral such as calcium is desired in the dietary intake of the
ruminants.
5.35 6.73 6.78 7.11 7.62
0
1
2
3
4
5
6
7
8
100NG 75NG:25SPV 50NG:50SPV 25NG:75SPV 100SPV
%
Inclusion Level
OM % on DM basis
b
aaa
a
Figure 7: The OM % of different inclusion level of SPV in ensiling NG
ab: different alphabet in the same row showed significant different by Tukey Test (P<0.05)

20
4.2.3 The effect of different inclusion level on the CP value of the silages.
Figure 8 shows the CP content of all treatments. There is a significant difference
(P<0.05) in all the treatments with. The maximum inclusion level of SPV that can be
incorporated in ensiling NG to gain the highest CP content is 25%NG:75%SPV whereas
treatment 100%SPV is to show to what extent the possibility could be.
The age of harvesting is crucial in preparing the forage for ensiling. This is
because ensiling is intended to preserve the chemical properties of the forages at its
desired age. The recommended age to harvest NG is at 6 to 8 weeks old to optimise the
DM yield and nutritive value (Lounglawan et. al., 2014). Furthermore, the digestibility
reduces as the harvesting age increase due to ligninocellulosic material (Zailan et. al.,
2016). Thus, in this study NG used is harvested at 6 weeks old on the second harvesting
cycle as NG at this age contains an optimum CP content and low ligninocellulosic
material.
9.70 10.52 11.71 13.45 17.56
0
2
4
6
8
10
12
14
16
18
20
100NG 75NG:25SPV 50NG:50SPV 25NG:75SPV 100SPV
%
Inclusion Level
CP % on DM basis
ecb
a
d
Figure 8: The CP % of different inclusion level of SPV in ensiling NG
abcde: different alphabet in the same row showed significant different by Tukey Test (P<0.05)

21
Meanwhile, the same age for harvesting NG is not applicable in SPV harvesting.
Age of vine harvesting has impact on the tuber production of sweet potato. However,
harvesting the SPV at 105 days after planting led to insignificantly reduction of the tuber
production. In addition, harvesting SPV at this age can enhance shoot development and
dry matter of tuber (Mohammed et. al., 2011). This is due to concern of the tuber
production. Hence, in this study, SPV is harvested at 112 days (16 weeks old) of
planting. Harvest SPV at 105 days led to insignificant reduction of tuber (Mohammed
et. al., 2011). The other factor that proved as to why the higher the inclusion level of
SPV in ensiling NG is that SPV has crude protein contents range from 16%-29% on DM
basis which is comparable to leguminous forages (An et. al., 2003; Dung, 2001).

22
4.2.4 The effect of different inclusion level on the EE value of the silages.
Figure 9 shows the EE content of all treatments. There is no significant difference
(P>0.05) of EE content for all treatments.
EE content is associated with the lipid content. Besides of its importance in
providing the proportion of fatty acids and antioxidant in the diet, fat also is important in
enhancing the palatability of the silages (McDonald et. al., 2010). Fat can stimulate the
saliva gland during mastication and increase the intake of the DM content.
Lipid oxidation that associated with lipoxygenases can be reduced by ensiling as
lipoxygenases favours aerobic condition (Elgersma et. al., 2003). The products of
oxidation include shorter-chain fatty acids, fatty acid polymers, aldehydes (alkanals),
ketones (alkanones), epoxides and hydrocarbons. The acids and alkanals are major
contributors to the smells and flavours associated with oxidised fat, and they significantly
reduce its palatability (McDonald et. al., 2010). Thus, by ensiling the lipid oxidation can
be inhibited and the palatability of the forage is maintained.
2.51 2.53 2.79 2.99 3.20
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
100NG 75NG:25SPV 50NG:50SPV 25NG:75SPV 100SPV
%
Inclusion Level
EE % on DM basis
aaaa
a
Figure 9: The EE % of different inclusion level of SPV in ensiling NG
a: same alphabet in the same row showed insignificant different by Tukey Test (P>0.05)

23
4.2.5 The effect of different inclusion level on the fiber content of the silages.
Figure 10 shows the fiber content of all treatments that were determined by Van Soest’s
Analysis.
In term of hemicellulose content, only 100%NG shows a highly significant
difference (P<0.05) than other treatments. Meanwhile, cellulose content of all treatments
is significantly difference (P<0.05) except 50%NG:50%SPV and 25%NG:75%SPV has
insignificant difference (P>0.05). In lignin content, only 100%SPV shows a significant
difference (P<0.05) whereas the other treatments are not significantly difference
(P>0.05).
Hydrolysis of hemicellulose occurs during ensiling and liberating pentose which
then will be fermented to lactic acid and acetic acid by lactic acid bacteria. Cellulose
digestibility is dependent on the lignification degree of the plant. Lignin can hinder the
Figure 10: The Van Soest’s Analysis of different inclusion level of SPV in ensiling NG
abcd: different alphabet in the same row showed significant different by Tukey Test (P<0.05)
100NG 75NG:25SPV 50NG:50SPV 25NG:75SPV 100SPV
Hemicellulose 25.68 20.38 21.29 20.63 22.63
Cellulose 44.48 38.95 36.04 35.31 30.90
Lignin 0.97 0.92 0.87 0.82 0.61
0
5
10
15
20
25
30
35
40
45
% on DM basis
Inclusion Level
Van Soest's Analysis
aaaab
abbbb
a
bccd

24
breakdown of the cellulose with which it is associated. In young pasture grass containing
only 50 g lignin/kg DM, 80% cellulose proportion is digestible, but in older herbage with
100 g lignin/kg DM, the proportion of cellulose digested can reduce to <60%. (McDonald
et. al., 2010).

25
CHAPTER 5
CONCLUSION
From the data presented in this study, it can be concluded that by incorporation
of Sweet potato vine, SPV in ensiling Napier grass, NG can improve significantly the
nutritional value of NG silage in term of CP and DM content. For the fermentative
quality, increment of SPV ratio increase pH value significantly, but within range of good
quality silage. Therefore, Napier grass and sweet potato vine can be ensiled alone or they
can be ensiled together.

26
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28
APPENDICES
Figure 6.1: ANOVA run for DM by SAS 9.4
Figure 6.2: ANOVA run for CP by SAS 9.4
Figure 6.3: ANOVA run for EE by SAS 9.4
Figure 6.4: ANOVA run for Hemicellulose by SAS 9.4

29
Figure 6.5: ANOVA run for Cellulose by SAS 9.4
Figure 6.6: ANOVA run for Cellulose by SAS 9.4
Figure 6.7: ANOVA run for Pre-ensiled and Ensiled DM
by SAS 9.4
Figure 6.8: ANOVA run for Pre-ensiled and Ensiled OM
by SAS 9.4

30
Figure 6.9: ANOVA run for Pre-ensiled and Ensiled CP
by SAS 9.4
Figure 6.10: ANOVA run for Pre-ensiled and Ensiled EE
by SAS 9.4
Figure 6.11: ANOVA run for Pre-ensiled and Ensiled
Hemicellulsose content by SAS 9.4
Figure 6.12: ANOVA run for Pre-ensiled and Ensiled
Cellulsose content by SAS 9.4

31
Figure 6.13: ANOVA run for Pre-ensiled and Ensiled
Lignin content by SAS 9.4