Effects of cassava forage (manihot esculenta crantz) in diet on growth and methane production in cattle

Chapter 1: INTRODUCTION
1.1. Necessary of thesis
Previous studies showed that ruminants contribute 25% of total methane
produced on earth due to microbial fermentation of feeds in rumen to produce volatile
fatty acids (VFA), methane and carbonic… These gasses are released by eructation.
Some researches in Vietnam showed that each cow daily emitted into environment
about 170 - 241 litters of methane depended on breed, age and productivity of
animals.
Some scientists reported that cassava leaf (CL) and copra meal (CM) are sources
of protein supplement as well as good by-pass feed due to their tannin and lipid.
Previous studies showed that supplementation of dried CL and CM in cattle diets
improved body weight gain but there was few study on methane emission from
rumen fermentation. Therefore, we conducted the study “Effects of cassava forage
(Manihot esculenta Crantz) in diet on growth and methane production in cattle”.
1.2. Research objectives
To measure in vitro digestibility and methane production of feeds and different
mixtures of Napier grass and dried cassava forage in beef cattle diet.
To measure effects of dried, ensiled and fresh cassava forage in diets based on
Napier grass on digestibility, body weight gain and methane production of Sindhi x
Yellow cattle.
To find out the appropriate ration by replacement of copra meal by dried cassava
forage in diets based on Napier grass on body weight gain and methane production of
Sindhi x Yellow cattle.
1.3. Research contents
The studies were conducted in following 4 experiements:
(1) Study on digestibility and methane production of some feeds and different
mixtures of Napier grass and cassava forage by in vitro gas production technique.
(2) Effects of dried, ensiled and fresh cassava forage in diets on digestibility and
methane production of Sindhi x Yellow cattle.
(3) Effects of dried, ensiled and fresh cassava forage in diets on live weight gain
and methane production of Sindhi x Yellow cattle.

1


(4) Effects of replacing copra meal by dried cassava forage in diets on live
weight gain and methane production of Sindhi x Yellow cattle.
1.4. Research subjects
Studying methane production of Napier grass, ruzi grass and para grass; dried
cassava forage, cotton seed meal and copra meal; mixtures of Napier grass and dried
cassava forage in cattle diets using in vitro gas production technique with Sindhi
cattle rumen fluid.
Studying the uses of fresh, dried and ensiled cassava forage after harvesting on
digestibility, body weight gain and methane production of Sindhi x Yellow cattle.
Studying the effects of replacing copra meal by dried cassava forage in diets on
body weight gain and methane production of Sindhi x Yellow cattle.
1.5. Location and duration
The study was conducted from October 2012 to March 2015. The experiment 1
was carried out at laboratory, department of Animal Sciences, college of Agriculture
and Applied Biology, Can Tho university. Experiment 2, 3 and 4 were carried out at
Center for Research and Technology Transfer, Nong Lam University of Ho Chi Minh
city.
1.6. Findings of dissertation
Para grass, dried cassava forage and a mixture of 20% dried cassava forage and
Napier grass decreased in vitro methane production.
Replacement of 20% dried, ensiled and fresh cassava forage for Napier grass in
diets decreased methane emission of Sindhi x Yellow cattle.
Replacement of 10% copra meal by 10% dried cassava forage in cattle diets
improved body weight gain and tended to reduce methane production.
1.7. Outline of dissertation
There are 3 pages of introduction, 32 pages of literature review, 19 pages of

materials and methods, 52 pages of results and discussion, 1 page of conclusion and
recommendation, references and index. The dissertation has 46 tables, 20 figures and
188 references.

2


Chapter 2: LITERATURE REVIEW
2.1. Rumen digestibility
Approximate 85% of feeds are digested in rumen by microbial fermentation.
Microbial fermentation of feeds produces VFA, NH3, amino acids and fatty acids…
These products are absorbed through rumen wall, whereas carbonic and methane are
released into environment by eructation. Undigestibility feeds move and digest at
abomasum and small intestine to supply nutrients for animals. However, studies
showed that 10% of energy intake are lost by rumen methane production. An balance
ration will improve performance and decrease methane production in cattle.
Cassava leaf contains 18.3–24.5% crude protein, full of essential amino acids and
minerals. Cassava leaf also contain quite high toxic compounds such as condensed
tannin (2.7– 4.4%) and hydrogen cyanide (325–399 mg/kg in dried and ensiled cassava
leaf and 911–1,426 mg/kg in fresh cassava leaf). If feeding at high amount of fresh
cassava leaf, it will affect animal health. By recommendation, the appropriate level of
additional cassava leaf in ruminant diet is 20%. The researches in cattle showed that
supplementation of cassava leaf and copra meal has improved dry matter intake, feed
digestion and body weight gain, but reduces protozoa population and methane
production.
2.2. Effect of diets on rumen methane production
Studies showed that supplemental diets of cassava leaf or copra meal reduce
methane emission because condensed tannin and lipid content in diet reduce amount
of protozoa and decrease rumen methane production.
Tannin: Addition of 20% cassava leaf or 0.4% condensed tannin in diet often

reduces ruminal protozoa population of cattle and buffaloes, which relates to decrease
methane emission. Ruminal protozoa involve in rumen methane production, and
protozoa may produce hydrogen and provide this gas for activity of rumen
methanogen bacteria. Methanogen bacteria and protozoa live symbiotically in rumen,
and therefore, reducing of protozoa population may affect activity of rumen
methanogen bacteria.
Lipid: Supplementing lipid in diet often decreases methane emission, which
depends on kinds of lipid. However, supplementation of lipid at 6 - 8% in diet will
cause negative effects on dry matter intake and digestibility of carbohydrates. On the
other hand, lipid reduces rumen protozoa population, and some fatty acids are toxic to
methanogen bacteria or hydrogenation of unsaturated fatty acids leads to decline
methane production.
3


Chapter 3: MATERIALS AND METHODS
3.1 Research methods
3.1.1 Experiment 1: Study on digestibility and methane production of feeds and
mixtures of Napier grass and cassava forage by in vitro gas production technique
The objectives of this experiment were to determine in vitro digestibility and
methane production of some feeds such as Napier grass, ruzi grass, guinea grass, para
grass, cassava forage, cotton seed meal, copra meal, and mixtures of Napier grasss
grass and cassava forage in cattle diet.
The experiment was carried out from October 2012 to March 2013.
Table 3.1: Nutrient composition of feeds used in experiment 1

Feed

DM, %

% DM basis
OM

CP

NDF

Ash

Para grass

17.6

88.2

8.40

57.7

11.8

Ruzi grass

20.0

91.2

8.65

58.0

8.82

Guinea grass

20.5

88.4

8.93

69.0

11.6

Napier grass

18.3

88.0

10.7

62.2

12.0

Cassava forage

87.9

86.1

21.2

44.0

13.9

Coconut meal

93.6

92.4

17.5

56.3

7.59

Cotton seed meal

87.8

92.6

35.6

41.4

7.37

DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber, Ash: total minerals

In vitro gas production technique was followed the method of Menke and
Steingass (1988). Preparation of media solution for in vitro gas production was a
mixture of solutions: macro-mineral solution, micro-mineral solution, buffer solution,
resazurin solution and reducing solution. The media solution was incubated at 39°C,
stirred and gassed carbonic until solution turns blue to pink. pH value of media
solution before incubation ranges from 7.0 to 7.3.
Rumen fluid was used from 03 fistulated cattle fed the same diet based on
natural grass and rice straw. Rumen fluid was collected before morning feeding and
kept in thermos flasks. It was then transported to laboratory, filtered through muslin
fabric into pre-warmed thermos flasks and incubated at 39°C. Rumen fluid was
gassed further with carbonic to make anaerobic condition, tighly closed and
incubated for experiments.
The experiment was conducted as a completely randomized design with 5
replicates. The treatments included (1) forages such as para grass, ruzi grass, guinea
4


grass and Napier grass; (2) protein-supplemented feeds such as cassava forage, cotton
seed meal and copra meal; (3) mixtures of replacing Napier grass for cassava forage
at 0, 10, 20 and 30% in diet (DM basis). Two replicates of blank solution were also
included in this study. The blank solution contained only rumen fluid and media
solution without substrates. Measured gas from blank solution was used to correct the
exact calculation of gas production.
Parameters: Digestibility of DM and OM, total gas volume, methane and
carbonic concentrations, methane and carbonic volumes at 48 h post incubation.

3.1.2 Experiment 2: Effects of dried, ensiled and fresh cassava forage in diet on
digestibility and methane production of Sindhi x Yellow cattle
The objective of this experiment was to determine effect of dried, ensiled and
fresh cassava forage in Napier grass diet on DM intake, nutrient digestibility,
nitrogen retention, rumen fluid parameters and methane production of Sindhi x
Yellow cattle.
The experiment was carried out from March to June 2013.
Nutrient composition of feeds and diets are presented in Table 3.2 and 3.3.
Table 3.2: Nutrient composition of feeds used in experiment 2
% DM basis

DM,
%

CP

Ash

NDF

Tannin1

HCN,mg/kg

ME,MJ/kg

NG

18.4

10.2

9.63

53.3

-

-

8.45

DCF

88.7

18.6

7.28

41.6

3.04

294

9.82

ECF

30.3

17.3

7.64

42.8

2.96

282

9.62

FCF

18.1

18.3

7.04

47.9

3.09

816

9.81

Feed

NG: Napier grass, DCF: dried cassava forage; ECF: ensiled cassava forage; FCF: fresh cassava forage,
DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber, Ash: total minerals,
HCN: hydrogen cyanide, ME: metabolizable energy (Abate and Mayer, 1997), 1condensed tannin
determination followed Butanol-HCl method of Terrill et al. (1992)

The experiment was conducted as a 4 x 4 Latin square design. Four treatments
were control without replacing of Napier grass by cassava forage (CF-0), replacing of
Napier grass by 20% dried cassava forage (DCF-20), replacing of Napier grass by
20% ensiled cassava forage (ECF-20) and replacing of Napier grass by 20% fresh
cassava forage (FCF-20).
Each experimental period lasted for 21 days including the first 14-day for
adaptation to experimental diets. Animals were then kept in cage floor for 7-day to
collect the data of feed intake, feces and urine. At the end of 3 days of each
5


experimental period, cattle were located into respiration chambers to determine
volume of methane emission.
Table 3.3: Diet formulation and nutrients of experiment 2 (% DM)
Ingredient, % DM

Treatment
CF-0

DCF-20

ECF-20

FCF-20

100

80

80

80

Cassava forage, %

0

20

20

20

NaCl, g

20

20

20

20

Crude protein, %

10.2

11.4

11.2

11.1

Neutral detergent fiber, %

53.3

51.0

51.2

51.4

Condensed tannin , %

00.0

0.60

0.59

0.53

ME, MJ/kgDM

8.45

8.60

8.58

8.59

Napier grass, %

CF-0: control without replacing cassava forage for Napier grass, DCF-20, ECF-20, FCF-20: replacing 20% dried,
ensiled, fresh cassava forage for Napier grass in diet; ME: metabolizable energy

Cattle methane production was determined by using improved respiration
chambers: the amount of cattle methane emission was measured through measuring
systems of air flow and methane concentration which were connected to improved
respiration chambers. The air circulation in improved respiration chambers was
control in one direction depending on the vacuum pump which was connected to the
air vent out. This system drawn air through the measuring device of air flow to
determine total amount of air which was sucked out of respiratory chambers. The air
inside improved respiration chambers was sucked out by Air Blower equiment
(Model GF180, Resun Group Co., Ltd., China) at air flow 18 m3/h. Air flow in
chambers was measured by Gas Meter equipment (Model G16, Hangzhou Beta Gas
Meter Co., Ltd., China) which could determine air flow from 16 to 25 m3/h.
Air samples inside respiratory chambers were collected for every 30 minutes. At
every sapling time points, air samples were collected for one minute and kept in 2 m3
gas collecting bags. When bags were full of air, it would be measured for methane
concentration using Gasmet equiment (Model DX 4030, Gasmet Techologies Inc.,

Finland). Similarly, this process was repeated during each sampling period.
Parameters: feed and nutrient intakes, nutrient digestibility, pH, N-NH3,
numbers of rumen bacteria and protozoa, daily volume of cattle methane emission.

6


3.1.3 Experiment 3: Effects of dried, ensiled and fresh cassava in diet on body
weight gain and methane production of Sindhi x Yellow cattle
The objective of experiment was to determine effect of dried, ensiled and fresh
cassava forage in Napier grass diet on body weight gain, feed conversion ratio,
economic effect and methane production of Sindhi x Yellow cattle.
The experiment was carried out from July 2012 to December 2013.
Chemical composition of feeds are presented in Table 3.4 and 3.5.
Table 3.4: Nutrient composition of feeds used in experiment 3
% DM basis

DM,
%

CP

Ash

NDF

Tannin1

HCN,mg/kg

ME, MJ/kg

NG

18.2

10.1

10.2

49.1

-

-

8.37

DCF

85.2

17.5

8.27

36.7

2.87

279.5

9.57

ECF

36.6

17.1

8.81

38.2

2.71

298.3

9.46

FCF

19.4

17.7

7.94

39.7

2.95

851.2

9.64

Feed

NG: Napier grass, DCF: dried cassava forage; ECF: ensiled cassava forage; FCF: fresh cassava forage,
DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber, Ash: total minerals,
HCN: hydrogen cyanide, ME: metabolizable energy (Abate and Mayer, 1997), 1condensed tannin
determination followed Butanol-HCl method of Terrill et al. (1992)

The experiment was conducted as a completely randomized design with 4
treatments and 5 replicates. Four treatments were control without replacing of Napier
grass by cassava forage (CF-0), replacing of Napier grass by 20% dried cassava
forage (DCF-20), replacing of Napier grass by 20% ensiled cassava forage (ECF-20)
and replacing of Napier grass by 20% fresh cassava forage (FCF-20).
Table 3.5: Diet formulation and nutrients of experiment 3 (% DM)
Item

Treatment
CF-0

DCF-20

ECF-20

FCF-20

100

80

80

80

Cassava forage, %

0

20

20

20

NaCl, g

20

20

20

20

Crude protein, %

10.1

11.2

11.0

11.1

Neutral detergent fiber, %

49.1

46.6

46.9

47.4

ME, MJ/kgDM

8.37

8.58

8.57

8.56

Napier grass, %

CF-0: control without replacing cassava forage for Napier grass, DCF-20, ECF-20, FCF-20: replacing
20% dried, ensiled, fresh cassava forage for Napier grass in diet; ME: metabolizable energy

7


Parameters: Feed and nutrient intakes, feed conversion ratio, weight gain,
economic effect and methane emission.
3.1.4 Experiment 4: Effect of replacing copra meal by dried cassava forage in
diet on body weight gain and methane production of beef cattle
The objective of experiment was to determine effect of replacing copra meal by
dried cassava forage in diet on body weight gain, feed conversion ratio, economic
effect and methane production of Sindhi x Yellow cattle.
The experiment was carried out from March 2014 to March 2015. Chemical
composition of feeds and diets are presented in Table 3.6 and 3.7.
Table 3.6: Nutrient composition of feeds used in experiment 4
% DM basis
DM,%

CP

EE

NDF

Ash

Tannin1

ME,

MJ/kg

NG

17.9

10.3

2.69

59.3

10.1

-

8.69

DCF

87.2

17.1

3.45

42.6

7.95

2.13

9.92

CM

87.8

17.9

7.02

50.1

7.28

0.21

11.0

RB

88.2

12.2

11.8

28.3

8.13

-

11.2

Feed

NG: Napier grass, DCF: dried cassava forage, CM: copra meal, RB: rice bran, DM: dry matter, EE: ether
extract, CP: crude protein, NDF: neutral detergent fiber, Ash: total minerals, HCN: hydrogen cyanide. ME:
metabolizable energy (Viện Chăn nuôi, 2001), tannin1: condensed tannin.

Table 3.7: Diet formulation and nutrients of experiment 4
Item

Treatment
CM-20

CM-15

CM-10

CM-5

CM-0

Napier grass, %

70

70

70

70

70

Concentrate, %

30

30

30

30

30

NaCl, g

20

20

20

20

20

Crude protein, %

11,9

11,9

11,9

11,8

11,8

Ether extract, %

4,28

4,15

3,76

3,73

3,61

ME, MJ/kgDM

9,39

9,34

9,29

9,24

9,19

CM-20, CM-15, CM-10,CM-5 và CM-0: replacing copra meal by dried cassava forage at 0, 5, 10, 15 and
20% in diet based on Napier grass; ME: metabolizable energy

The ratio of concentrate:roughage was 30:70. The levels of replacing copra meal
by dried cassava forage were at 0, 5, 10, 15 and 20% while rice bran was kept at 10%
in diets. The formulation of concentrate is presented in Table 3.8.

8


Table 3.8: Formulation and nutritional values of concentrate (% DM)
Item

Feed ingredients of concentrate (%)
CM-20

CM-15

CM-10

CM-5

CM-0

Coconut meal, %

68

51

34

17

0

Dried cassava forage, %

0

17

34

51

68

Rice bran, %

32

32

32

32

32

Crude protein, %

15,8

15,7

15,7

15,5

15,4

ME, MJ/kgDM

11,0

10,8

10,7

10,5

10,3

CM-20, CM-15, CM-10,CM-5 và CM-0: replacing copra meal by dried cassava forage at 0, 5, 10, 15 and
20% in diet based on Napier grass; ME: metabolizable energy

The experiment was conducted as a completely randomized design with 5
treatments and 4 replicates. Five treatments were 0, 5, 10, 15 and 20% copra meal
replaced by dried cassava forage in Napier grass basal diets.
All parameters in this experiment were similar to those in experiment 3.
3.2 Statistical analysis
Experimental data were analyzed variance by ANOVA procedure of General
Linear Model and regression of Minitab 16.0. Significant differences among
treatment means were assessed by Tukey's multiple comparison tests after a
significant F-test. Overall differences between treatment means were considered to be
significant at P<0.05.

9


Chapter 4: RESULTS AND DISCUSSION
4.1 Experiment 1: Study on digestibility and methane production of feeds and
mixtures of Napier grass and cassava forage by in vitro gas production technique
4.1.1 Digestibility and methane emission of para grass, ruzi grass, guinea grass
and Napier grass by using in vitro gas production technique
Table 4.1: In vitro digestibility, volume and concentration of methane and carbon dioxide
production of grass at 48 hours
Treatment
Item

Para

grass

Ruzi
grass

Guinea
grass

Napier
grass

MSE

P

DM digestibility, %

51.6a

54.2a

47.0b

53.3a

0.81

<0.01

OM digestibility, %

52.9a

55.5a

48.2b

54.1a

0.83

<0.01

b

a

b

a

Total gas, ml/0.2 g DM

27.7

32.5

25.5

35.1

0.87

<0.01

Methane, %

7.07b

10.8a

12.4a

12.4a

0.40

<0.01

Carbon dioxide, %

71.7

73.6

70.3

72.3

0.91

0.13

Methane, ml

1.95d

3.52b

3.15c

4.37a

0.62

<0.01

b

a

23.9

b

17.9

a

25.4

0.65

<0.01

c

b

c

a

Carbon dioxide, ml

19.8

Total gas, ml/g OMD

297

321

300

366

2.90

<0.01

Methane, ml/g OMD

21.0c

34.9b

37.2b

45.7a

0.75

<0.01

Carbon dioxide, ml/g OMD

213c

237b

211c

265a

1.97

<0.01

OMD: organic matter digestibility, DM: dry matter, OM: organic matter.

differing superscript letters are significantly different (P<0.01).

a, b, c, d

Means within rows with

Table 4.1 showed that in vitro dry matter digestibility (DMD) and organic
matter digestibility (OMD) at 48 hours of guinea grass was lowest 48.2% (P<0.05).
Because it contains high NDF and low CP. In vitro dry matter and organic matter
digestibility at 48 hours of para grass, ruzi grass, guinea grass and Napier grass were
more than 47%.
Total gas, methane and carbon dioxide volume (ml/g OMD) at 48 hours of para
grass and guinea grass were lowest while ruzi grass and Napier grass had the highest
value (P<0.01). Para grass has considerable potential to reduce methane emission.

10


4.1.2 Digestibility and methane emission of dried cassava forage, cotton seed
meal and copra meal using in vitro gas production technique
Table 4.2: Digestibility, volume and concentration of methane and carbon dioxide emission
at 48 hours of dried cassava forage, cotton seed meal and copra meal
Treatment
Item

DCF

CSM

CM

SE

P

DM digestibility, %

48.6b

65.8a

64.5a

2.27

<0.01

OM digestibility, %

52.1b

68.1a

66.1a

2.07

<0.01

Total gas, ml/0.2 g DM

14.2

c

26.2

b

a

39.6

0.66

<0.01

Methane, %

15.7

13.5

13.7

0.74

0.11

Carbon dioxide, %

65.4

69.4

74.9

2.65

0.07

Methane, ml

2.23c

3.52b

5.43a

0.15

<0.01

c

b

a

29.6

0.32

<0.01

Carbon dioxide, ml

9.27

18.1

Total gas, ml/g OMD

159c

224b

349a

3.19

<0.01

Methane, ml/g OMD

24.9c

30.1b

47.9a

0.45

<0.01

Carbon dioxide, ml/g OMD

104c

155b

262a

3.89

<0.01

DCF: dried cassava forage, CSM: cotton seed meal, CM: copra meal. OMD: Organic matter digestibility,
DM: dry matter, OM: Organic matter. a, b, c Means within rows with differing superscript letters are
significantly different (P<0.01).

Table 4.2 showed that DMD and OMD at 48 hours of dried cassava forage
(DCF), cotton seed meal (CSM) and copra meal (CM) were significantly different
(P<0.01). Dry matter digestibility of DCF was lowest 48.6%. DCF would be a good
cattle bypass source feed. Organic matter digestibility at 48 hours of DCF, CSM and
CM were more than 50%. It was a very good feed to supply protein for cattle.
Total gas, methane and caborbon dioxide volume (ml/g OMD) were lowest at 48
hours of DCF, next was CSM and highest was CM. It was significantly different
(P<0.01). Low in vitro digesitbility of DCF could be cause low total gas and methane
volume. Moreover, DCF would be a good source feed which contains rumen bypass

nutrients. It limited rumen fermentation, total gas emission. On the other hand, DCF
contained condensed tannin 3.04% (Table 3.2) which reduced rumen protozoa to
make low methane emission.
Total gas and methane volume of CM were highest due to high NDF content of
CM (56.3%), it was lower in DCF and CSM with 44 and 41,4%, respectively (Table
3.1). NDF digestion produced more acetic acid and caused increasing methane
volume. Because bacteria fermented cellulose and produced more hydrogen for
bacteria to synthesize methane.
11


DCF has the lowest methane volume, it is potenial feed source for cattle to
supply crude protein and reduce methane production.
4.1.3 Degestibility, methane and carbon dioxide emission of Napier grass
mixtured with levels of dried cassava forage by using in vitro gas production
technique
Table 4.3: Digestibility, volume and concentration of methane and carbon dioxide emission
at 48 hours of Napier grass mixtured with levels of dried cassava forage
Treatment

Item
DCF-0

DCF-10

DCF-20

DCF-30

MSE

P

DM digestibility, %

43.9ab

45.0a

45.3a

41.5b

0.71

<0.01

OM digestibility, %

44.7ab

45.9a

46.1a

42.1b

0.79

0.01

Total gas, ml/0.2 gDM

37.3

a

a

36.6

34.3

b

b

32.5

0.45

<0.01

Methane, %

18.0

18.0

17.6

18.1

0.32

0.66

Carbon dioxide, %

70.0

70.3

68.1

68.6

0.73

0.14

Methane, ml

6.73a

6.59ab

6.03bc

5.90c

0.16

0.01

a

a

25.7

23.4

b

b

22.3

0.46

<0.01

Carbon dioxide, ml

26.1

Total gas, ml/g OMD

473a

454ab

424c

442bc

6.80

<0.01

Methane, ml/g OMD

85.2a

81.5a

74.5b

80.1ab

1.49

<0.01

Carbon dioxide, ml/g OMD

331a

319ab

289c

303bc

5.24

<0.01

DCF-0, DCF-10, DCF-20, DCF-30: mixture Napier grass with replacement levels of dried cassava 0, 10,
20 và 30%. OMD: organic matter digestibility, DM: dry matter, OM: organic matter. a, b, c Means within
rows with differing superscript letters are significantly different (P<0.01).

Table 4.3 showed that DM and OM digestibility at 48 hours of DCF-30
treatment was lowest (P<0.01). DCF-30 treatment had the lowest digestibility. The
result is also fit with table 4.2; digestibility of cassava forage is lower than Napier
grass. Increasing replacemental levels of cassava forage with Napier grass reduced
digestibility in DCF-30 treatment. Results showed the mixture of Napier grass with
20% cassava forage is appropriate diet, no effect on digestibility.
Total gas, methane and carbon dioxide volume (ml/g OMD) at 48 hours reduced
with increasing replacement of dried cassava in Napier grass diet. It was significantly
different (P<0.01). Cassava forage may be good bypass source. DCF-20 treatment is
optimal, no effect on DM and OM digestibility, and reduction methane production.
Generally, para grass, dried cassava forage and mixture of Napier grass with
20% cassava forage in diet were potential feed to reduce methane.

12


4.2 Expriment 2: Effects of dried, ensiled and fresh cassava forage in diet on

digestibility and methane production of Sindhi x Yellow cattle
4.2.1 Feed intake, nutrients and metabolizable energy of cattle in experiment 2
Table 4.4: Feed intake, nutrients and metabolizable energy of cattle in experiment 2
Treatment
Item
CF-0

DCF-20

ECF-20

FCF-20

MSE

P

DM intake, % BW
OM, kg/head/day

1.95b
2.92b

2.26a
3.38a

2.25a
3.40a

2.18a

3.27a

0.03
0.05

<0.01
<0.01

NDF, kg/head/day
CP, g/head/day

1.72b
330b

1.90a
441a

1.92a
436a

1.89a
419a

0.03
5.26

<0.01
<0.01

CP, g/100kg BW

ME, MJ/ head/day
ME, MJ/kg W0.75

199b
27.3b
0.59b

269a
32.5a
0.71a

262a
32.5a
0.70a

253a
31.4a
0.68a

3.72
0.44
0.01

<0.01
<0.01
0.01

Tannin1, g/ head/day
HCN, mg/kg BW
HCN, mg/ head/day

0.00c
0.00c
0.00c

22.3a
1.32b
216b

22.1ab
1.27b
210b

19.2b
3.07a
508a

0.61
0.06
12.8

<0.01
<0.01
<0.01

DM: dry matter, OM: organic matter, CP: crude protein, NDF: neutral detergent fiber, ME: metabolizable
energy, W0,75: metabolism weight, HCN: hydrogen cyanua; BW: body weight. CF-0: without cassava forage;
DCF-20, ECF-20, FCF-20: replacement 20% dried cassava forage, ensiled cassava forage, fresh cassava
forage in Napier grass. diet. 1: tannin condensed. a, b, c Means within rows with differing superscript letters
are significantly different (P<0.01)

Table 4.4 showed that daily DM, OM, CP and NDF intakes increased with
replacement of cassava forage. Because cassava forage had CP and ME higher than
Napier grass to increase daily intake, rumen bacteria and digestibility (Table 4.5).
The daily metabolizable energy intakes (MJ/head/day) of treatments were from
30.5 to 36.7 MJ, increased in treatments of replacing DCF, ECF and FCF (P<0.05).
Replacement cassava forage treatments had ME intakes ranged from 31.4 to 32.5
MJ/head/day. This result was consistent with Kearl’s standard (1982) when cattle had
body weight of 150 kg and weight gain was 500 g/head/day, ME requirement of 33.6
MJ/head/day.
The amount of condensed tannin and HCN intakes in replacemental diets of
cassava forage ranged from 19.2 to 22.3 g/head/day and from 1.27 to 3.07 mg/kg
(P<0.01), but did not affect on DM intake.
Generally, DM, OM, CP and ME intakes increased in replacemental treatments
of DCF, ECF and FCF.

13


4.2.2 Nutrient digestibility and nitrogen balance of cattle in experiment 2
Table 4.5: Nutrient digestibility and nitrogen balance of cattle in experiment 2
Item

Treatment
CF-0

DCF-20

ECF-20

FCF-20

MSE

P

Dry matter

51.8b

60.9a

60.1a

59.0a

1.18

<0.01

Organic matter

53.9b

64.6a

63.5a

62.7a

1.11

<0.01

b

a

a

a

Digestibility, %

Crude protein

60.3

68.8

68.0

67.4

0.92

<0.01

Neutral detergent fiber

52.9b

60.9a

59.9a

59.2a

1.18

0.01

52.8b

70.6a

69.7a

67.0a

0.84

<0.01

b

a

a

a

Nitrogen balance, g/ngày
Nitrogen intake
Nitrogen excreted

29.2

35.5

36.2

37.2

0.45

<0.01

Nitrogen retention

23.5b

35.1a

33.5a

29.8a

1.18

0.02

Nitrogen retention, g/kg W0.75

0.51b

0.76a

0.72a

0.65a

0.03

0.02

CF-0: without cassava forage; DCF-20, ECF-20, FCF-20: replacement 20% dried cassava forage, ensiled
cassava forage, fresh cassava forage in Napier grass. W0,75: metabolism weight. a, b Means within rows with
differing superscript letters are significantly different (P<0.01)

Table 4.5 showed that digestibility of DM, OM, CP and NDF increased from 7
to 9% on treatments of replacement with dried, ensiled and fresh cassava forage. It
was significantly different (P<0.01). Because Napier grass is high fiber and low
protein content, thus nutrient digestibility is lower than cassava forage replacemental
treatments.
The amount of HCN intake in FCF-20 treatment was highest with 508
mg/head/day (Table 4.4). This result was lower than previous studies in cattle. They
found that amount of HCN intakes ranged from 1,180 to 1,256 mg/head/day and did
not effect on feed nutrient digestibility, amount of rumen bacteria, protozoa and
fungi. Similarly, condensed tannin intake in replacemental diets of cassava forage

ranged from 0.53 to 0.60% (Table 3.3), did not affect on feed nutrient digestibility.
With replacing 20% cassava forage in Napier grass diets, amount of HCN and
condensed tannin did not affect feed nutrient digestibility.
Table 4.5 showed that nitrogen intakes increased from 52.8 to 70.6, excreted
nitrogen increased from 29.2 to 37.2 g/day and nitrogen retention increase from 23.5
to 35.1 g/day. Nitrogen balance (g/day) increased in replacement diet of cassava
forage (P<0.05). Because replacement diets of cassava forage had high protein

14


digestibility and high amount of rumen N-NH3 (Table 4.6), high amount of blood
urea to increase body nitrogen retention.
Gerenally, digestibility and nitrogen retention increased in replacement diets of
cassava forage by increasing crude protein content in diets.
4.2.3 Concentration of ammonia nitrogen, pH, number of bacteria and protozoa
in rumen
Table 4.6: The concentration of ammonia nitrogen (N-NH3), pH, number bacteria and
protozoa in rumen at before and 3 hours after feeding

Item

Treatment
CF-0 DCF-20 ECF-20 FCF-20 SEM P

pH, before feeding

7.03

7.09

7.02

7.07

0.03 0.27

pH, 3 hours after feeding

6.82a

6.85a

6.71b

6.83a

0.02 0.01

N-NH3, mg/100ml, before feeding

9.11

10.3

10.0

10.1

0.34 0.17

N-NH3, mg/100ml, 3 hours after feeding

11.2b

15.9a

15.7a

15.6a

0.84 0.02

Bacteria, x109/ml, before feeding

2.23

2.39

2.44

2.32

0.09 0.44

Bacteria, x109/ml, 3 hours after feeding

2.65b

3.47a

3.37a

3.28a

0.13 0.01

Protozoa, x10 /ml, before feeding

0.99

0.78

0.71

0.70

0.08 0.14

Protozoa, x105/ml, 3 hours after feeding

1.71a

1.18b

1.22b

1.08b

0.10 0.02

5

CF-0: without cassava forage; DCF-20, ECF-20, FCF-20: replacement 20% dried cassava forage, ensiled
cassava forage, fresh cassava forage in Napier grass. N-NH3: nitrogen ammoniac. a, b Means within rows
with differing superscript letters are significantly different (P<0.05)

Table 4.6 showed that pH, N-NH3, bacteria and protozoa in rumen at before
feeding of treatments were similar (P> 0.05).
Rumen pH of experimental cattle at 3 hours after feeding ranged from 6.71 to
6.85 (P <0.05). Rumen pH of NMU-20 treatment was 6.71, it was lower than other
treatments. This could be explained that ensiled cassava forage was low pH, when
replacing ensiled cassava forage on experimental diet reduced rumen pH.
The concentration of N-NH3 in rumen of experiment at 3 hours after feeding
increased with replacemental treatments of DCF, ECF and FCF (P<0.05). Because
crude protein of cassava forage supplied in diets to increase amount of crude protein
in daily intake (Table 4.4) and increased protein digestibility (Table 4.5) and increase
rumen N-NH3.
At 3 hours after feeding, in replacemental treatments of cassava forage had
higher amount of bacteria (P<0.05). The protein of cassava forage provided amount
of N-NH3 for bacteria development.
15


Number of protozoa at 3 hours after feeding decreased with cassava forage
replacemental treatments (P<0.05). It could be caused by condensed tannin in cassava
forage that keep an important role in reducing number of protozoa in rumen fluid.
Condensed tannin are toxic for protozoa in rumen, because they change permeability
of cell membranes protozoa. So condensed tannin in cassava forage reduced number
of protozoa in rumen.

Generally, replacing of dried, ensiled and fresh cassava forage in Napier grass
diet increased N-NH3 concentration and total number of bacteria, but reduced number
of protozoa.
4.2.4 Cattle methane emission in experiment 2
Table 4.7 showed that total cattle methane emission at 24 hours and methane
volume of DM intake, OM intake and OM digestibility (litre/kg) reduced
significantly with replacing of dried, ensiled and fresh cassava forages (P<0,01).
Table 4.7: Methane production of cattle in experiment 2
Treat ment
Item
Total methane, litre/head/day

CF-0 DCF-20
117
a

105
b

ECF-20
104

FCF-20 SEM
3.38

0.09

27.9

b

28.4

1.15

<0.01

b

103

P

Methane, litre/kg DMI

36.3

28.2

Methane, litre/kg OMI

40.1a

31.1b

30.8b

31.3b

1.27

<0.01

Methane, litre/kg OMD

74.9a

48.1b

48.6b

49.9b

3.04

<0.01

DMI: dry matter intake, OMI: organic matter intake, OMD: organic matter digestibility.
rows with differing superscript letters are significantly different (P<0.01)

a, b

Means within

When replacing of 20% DCF, ECF and FCF in Napier grass diets reduced
methane emission. Because nutrient of cassava forage escaped rumen fermentation to
reduce methane production. Moreover, condensed tannin content in cassava forage
reduced rumen protozoa (Table 4.6). Rumen methane production is related to
protozoa number. Protozoa metabolism could provide hydrogen for methane bacteria
development.

Result of experiment 2 showed that repalcing of 20% DCF, ECF and FCF in
Napier grass gass diets in crossbreed Sinhdi has improved digestibility, increased
nitrogen retention, reduced protozoa population and methane emission.

16


4.3 Experiment 3: Effects of dried, ensiled and fresh cassava in diet on body
weight gain and methane production of Sindhi x Yellow cattle
4.3.1 Feed intake, nutrient value and metabolizable energy of cattle in
experiment 3
Table 4.8: Feed intake, nutrient value and metabolizable energy of cattle in experiment 3
Treatment

Item
CF-0

DCF-20

ECF-20

FCF-20

MSE

P

2.21b

2.45a

2.49a

2.39a

0.04

<0.01

OM, g/head/day

3.27

b

a

3.79

a

3.85

a

3.69

0.05

<0.01

CP, g/head/day

366b

484a

489a

467a

6.59

<0.01

CP, g/100kg BW

222b

282a

285a

272a

4.64

<0.01

ME, MJ/head/day

30.5b

36.2a

36.7a

35.1a

0.46

<0.01

0.66

b

a

a

a

0.01

<0.01

Tannin, g/head/day

0.00

b

a

HCN, mg/kg BW

0.00c

DM intake, % BW

0,75

ME, MJ/kg W

0.76

a

0.77

a

0.74

23.8

23.2

21.4

0.60

<0.01

1.35b

1.49b

3.60a

0.09

<0.01

DM: dry matter, OM: organic matter, CP: crude protein, ME: metabolizable energy, W0,75: metabolism
weight, HCN: hydrogen cyanua; BW: body weight. CF-0: without cassava forage; DCF-20, ECF-20, FCF20: replacement 20% dried cassava forage, ensiled cassava forage, fresh cassava forage in Napier grass
diet. a, b, c Means within rows with differing superscript letters are significantly different (P<0.01)

DM, OM and CP intakes increased dramatically in replacement diets of dried,
ensiled and fresh forages (P<0.05). Because CP and ME contents of cassava forage
were higher than Napier grass for stimulating rumen bacteria development and
increased digestibility feed (table 4.5) leaded to increase DM intake.
Crude protein intake ranged from 366 to 489 g/head/day, similar to Shane
Gadberry’s standard (1996) weight gain was 453 g/head/day and demand CP intake
with 430 – 489 g/head/day.
Metabolizable energy intake of treatments ranged from 30.5 to 36.7
MJ/head/day, increased with replacing of dried, ensiled and fresh cassava forage
(P<0.05). The treatments of replacement cassava forage had ME intake ranged from
35.1 to 36.7 MJ/head/day. This result was consistent with Kearl’s standard (1982)

cattle had average body weight of 175 kg and weight gain was 453 g/head/day, ME
requirement of 37.5 MJ/head/day.
The amount of condensed tannin and HCN intake in replacing treatments of
cassava forage ranged from 21.4 to 23.8 g/head/day and from 1.35 to 3.6 mg/kg BW
not influence to DM intake.
17


In general, intakes of DM, OM, CP and ME increased with replacement of
dried, ensiled and fresh cassava forage in diets.
4.3.2 Body weight gain, feed conversion ratio and economic effect of cattle in
experiments 3
Table 4.9 showed the initial body weight in treatments was the same and ranged
from 143 to 146 kg (P>0.05). However, final body weight was from 185 to 200 kg. It
increased in treatments of replacing dried, ensiled and fresh cassva forage (P<0.01).
Weight gain is lowest in the first month, tended to weight gain sightly in the second
month, highest in the thrid month and stably in the fourth month.
Table 4.9: Body weight and weight gain of cattle in experiment 3
Treat ment
Item

CF-0

DCF-20

ECF-20 FCF-20

MSE

P

Initial, kg

145

144

143

146

3.01

0.92

Month 1, kg

154

157

156

158

2.85

0.80

Month 2, kg

164

171

Month 3, kg

175

b

171

172

185

b

Body weight (BW)

Month 4, kg

ab

185

a

a

186

a

2.77

0.24

ab

2.66

0.03

a

184

200

200

196

2.61

<0.01

Average BW gain

Month 1, g/head/day

307b

427a

433a

407a

9.43

<0.01

Month 2, g/head/day

333b

460a

480a

453a

10.0

<0.01

Month 3, g/head/day

350

c

a

a

b

Month 4, g/head/day
Average BW gain in period,
g/head/day

493

507

420

12.0

<0.01

340c

477a

487a

400b

7.73

<0.01

333c

464a

477a

420b

8.18

<0.01

CF-0: without cassava forage; DCF-20, ECF-20, FCF-20: replacement 20% dried cassava forage, ensiled
cassava forage, fresh cassava forage in Napier grass diet. a, b, c Means within rows with differing superscript
letters are significantly different (P<0.01).

Table 4.9 showed lowest average weight gain (g/head/day) in treatment CF-0
was 333 grams, the next FCF-20 was 420 gram and highest was DCF-20 and ECF20, with 464 and 477 grams, respectively. It was significantly different (P<0.01).
Because cassava forage supplied crude protein in diets of Napier grass leaded to
increase digestibility and weight gain.
On the other hand, feed intakes in replacement diet of FCF had weight gain
lower than DCF and ECF diets. It could explain that FCF-20 diet had HCN intake
18

with 3.6mg/kg live weight (Table 4.8) to reduce blood thyroxine content leaded to
lower weigth gain in DCF and ECF diets. Therefore, replacing of 20% dried and
ensiled and fresh cassava forage in Napier grass diets improved weight gain.
Table 4.10 showed that feed intake and weight gain increased in diet of
replacing cassava forage leaded to feed conversion ratio reducing with replacing of
dried, ensiled and fresh cassva forage, significantly (P<0.01).
Table 4.10: Feed conversion ratio of cattle in experiment 3
Treat ment
Item

CF-0

DCF-20

ECF-20 FCF-20

MSE

P

Total feed intake, kg

437b

504a

512a

490a

6,35

<0,01

Total weight gain in period, kg

39,9c

55,7a

57,2a

50,4b

0,98

<0,01

Feed conversion ratio, kg

11,0a

9,06b

8,96b

9,76b

0,25

<0,01

CF-0: without cassava forage; DCF-20, ECF-20, FCF-20: replacement 20% dried cassava forage, ensiled
cassava forage, fresh cassava forage in Napier grass diet. a, b, c Means within rows with differing superscript
letters are significantly different (P<0.01)

The result of table 4.10 showed that income after 4 months of experiment ranged
from 2,337,000 – 3,265,000 VND/head. The diet of replacing of cassava forage was
higher from 30 to 40% than Napier grass in diet, it was significantly different
(P<0.01).
4.3.3 Methane emissions of cattle in experiment 3
Total gas, methane volume, methane volume per DM and OM intakes and
weight gain in experiment 3 reduced significantly with replacing of dried, ensiled and
fresh cassava forage treatments (P<0.01).
Table 4.11: Methane emissions of cattle in experiment 3
Treatment
Item

CF-0

DCF-20

ECF-20

Total methane, litre/head/day

123

109

110

103

6,20

Methane, litre/kg DMI

33,7a

25,9b

25,6b

25,2b

1,33 <0,01

Methane, litre/kg OMI

37,5a

28,7b

28,5b

27,9a

1,47 <0,01

a

b

b

b

16,0 <0,01

Methane, litre /kg weight gain

371

235

230

FCF-20 MSE

245

P
0,18

DMI: dry matter intake, OMI: organic matter intake. a, b Means within rows with differing superscript letters
are significantly different (P<0.01)

Cattle methane production counted on weight gain (litre/kg weight gain) ranged

from 230 to 371 litres, it decreased significantly with replacing of cassava forage
(P<0.01). The results of experiment showed that replacing of cassava forage to
19


Napier grass diet supplied more crude protein for cattle and apparently improved
weight gain, it led to reduce methane production per kg weight gain. Besides, cassava
forage escaped rumen fermentation and leaded to low methane emission.
In summary, results of experiment 3 showed that replacing of 20% dried and
ensiled cassava on Napier grass diets improved weight gain, economic effectiveness
in terms of feed. Methane emissions of Sindhi x Yellow cattle were reduced at the
same time. It is not recommended to replace of 20% fresh cassava forage in diet
because it may lead to the lower weight gain than dried and ensiled cassava forage.
4.4 Experiment 4: Effect of replacing copra meal by dried cassava forage in diet
on body weight gain and methane production of Sindhi x Yellow cattle
4.4.1 Feed intake, nutrient value and metabolizable energy of cattle in
experiment 4
Table 4.12: Feed intake, nutrient value and metabolizable energy of cattle in experiment 4
Item

Treatment
CM-20 CM-15

MSE

P

CM-10 CM-5 CM-0

DM intake, % BW

2,66

2,65

2,78

2,74

2,70

0.12

0.93

OM, kg/head/day

4,83

4,91

5,16

5,20

5,14

0.18

0.51

CP, g/head/day

630

642

678

681

673

24.9

0.50

NDF, kg/head/day

2,87

2,91

3,03

3,03

2,98

0.10

0.71

ME, MJ/head/day

49,6

50,3

52,8

53,0

52,1

1.87

0.63

ME, MJ/kg W0,75

0,94

0,93

0,98

0,96

0,94

0.04

0.92

Tannin g/head/day

2,15e

7,32d

13,6c

19,4b

24,8a

0.86 <0.01

EE, g/head/day

225

222

228

219

206

9.04

0.52

CM-20, CM-15, CM-10,CM-5 và CM-0: replacing copra meal by dried cassava forage at 0, 5, 10, 15 and
20% in diet based on Napier grass; OM: organic matter, CP: crude protein, ME: metabolizable energy,
W0,75: metabolism weight, EE: ether extract, NDF: neutral detergent fiber, BW: body weight. a-e Means
within rows with differing superscript letters are significant (P<0.01)

Table 4.12 showed that daily feed and nutrient intakes of OM, CP, NDF and ME
were similar among treatments (P>0.05). For this reason, dried cassava forage and
copra meal have quite similar values of OM, CP, NDF and ME contents. Daily ME
intake of diets ranged from 49.6 to 53.0 MJ/head. This result was in agreement with
Kearl (1982), where catlle had 200 kg body weight, and amount of daily ME intake
was 49 MJ/head. Condensed tannin intake linearly decreased (P<0.01) as increasing
levels of copra meal replaced for dried cassava forage. The content of daily tannin
intake was similar to experiment 3 (Table 4.8), thus it didn’t impact on DM intake.
Ether extract intake ranged from 206 to 225 g/head/day and held at 3.63 - 4.23% in
diets (Table 3.8).
20


4.4.2 Body weight gain, feed conversion ratio and economic effect of cattle in
experiment 4
The result showed that the initial and final body weights of cattle in this
experiment were 158–168 kg and 243–253 kg, respectively, and these values were
not significant difference (P>0.05).
Table 4.13: Body weight and body weight gain of cattle in experiment 4
Item

Treatment
CM-20

CM-15 CM-10

MSE

P

CM-5 CM-0

Body weight (BW)
Initial, kg

158

162

160

166

168

4.12

0.42

Month 1, kg

177

182

181

186

186

4.13

0.57

Month 2, kg

198

204

205

208

208

4.05

0.39

Month 3, kg

221

226

228

232

231

3.93

0.33

Month 4, kg

243

246

249

253

253

3.87

0.27

Average BW gain, g/head/day
Month 1

638

671

700

638

600

29.7

0.22

Month 2

679

729

771

750

729

23.7

0.14

Month 3

775

725

792

796

758

31.5

0.52

Month 4

721

663

675

708

742

22.8

0.14

BW gain in period

703

697

734

723

707

13.2

0.29

CM-20, CM-15, CM-10,CM-5 và CM-0: replacing copra meal by dried cassava forage at 0, 5, 10, 15 and
20% in diet based on Napier grass

Overall, weight gain was lowest in the first month, tended to sightly increase in
the second month, highest in the third month and stable in the fourth month. This may
be due to the experimental diets had equal CP and ME amounts, and palatability was

the same. After 120-day feeding, the daily weight gain of experimental animals
ranged from 697 to 734 g/head. This result was similar on finding of Shane Gadberry
(1996), weight gain of cattle was 680 g/head/day. Kearl (1982) reported that weight
gain of cattle was 750 g/head/day.
Table 4.14 showed that total amount of feed intake, weight gain of entire
experimental period and feed conversion ratio were similar among treatments
(P>0.05). Because replacement of DCF for CM in diet did not affect DM intake and
weight gain of animals.

21


Table 4.14: Feed conversion ratio of cattle in experiment 4
Item

Treatment
CM-20 CM-15 CM-10

MSE

CM-5

P

CM-0

Total feed intake, kg

637

648

682

688

681

23.5 0.45

Weight gain entire study, kg

84,4

83,6

88,1

86,8

84,9

1.58 0.29

Feed conversion ratio, kg

7,56

7,75

7,76

7,93

8,02

0.27 0.79

CM-20, CM-15, CM-10,CM-5 và CM-0: replacing copra meal by dried cassava forage at 0, 5, 10, 15 and
20% in diet based on Napier grass

The result showed that income over feed costs after 4-month feeding ranged
from 4,270,000 to 4,490,000 VND/head, and this parameter was similar among
treatments (P>0.05).
4.4.3 Methane emission of cattle in experiment 4
Table 4.15: Methane emission of cattle in experiment 4
Item

treatment

MSE

CM-20 CM-15 CM-10 CM-5

P

CM-0

Total methane. litre/head/day

122

117

115

118

113

4.36 0.69

Methane, litre/kg DMI

23,0

21,7

20,2

20,7

20,0 1.01 0.28

Methane, litre/kg OMI

25,2

23,8

22,3

22,8

22,1 1.12 0.31

Methane, litre/kg weight gain

173

168

157

164

160

7.79 0.62

DMI: dry matter intake, OMI: organic matter intake

Table 4.5 showed that treatment had no effect on methane emission (P>0.05). In
this study, methane emission of cattle ranged from 113 to 122 litres/day and from 157
to 173 litre/kg weight gain. The current result showed that methane emission of cattle
expressed as litre/kg DMI was lower than those of previous researches. This may
relate to effect of lipid content in copra meal and rice bran and condensed tannin
content in dried cassava leaf on methane production. Condensed tannin and lipid
could reduce rumen protozoa population, and therefore low methane production.
Reports in sheep and cattle showed that defaunation of rumen protozoa and protein

supplementation in diets lead to decrease methane emission. Moreover,
biohydrogenation process, which transforms unsaturated fatty acids to saturated fatty
acids by rumen microorganisms also to reduce hydrogen in rumen relecting on
mitigation of methane production. In general, an ideal treatment should look for
replacement of 10% copra meal for dried cassava forage.

22


Chapter 5: CONCLUSIONS AND SUGGESTIONS
5.1 Conclusions
Para grass and dried cassava forage were potential feeds that helps to reduce
methane emissions. The supplement of 20% dried cassava forage to Napier grass diet
does not affect organic matter digestibility, but helps to reduce methane emissions.
Replacing of 20% dried, ensiled and fresh cassava forages in Napier grass diets
improved dry matter intake, nutrient digestibility while reducing number of protozoa
and methane emission in Sindhi x Yellow cattle.
Replacing of 20% dried and ensiled cassava forages in Napier grass diets
improves dry matter intake, weight gain, economic effectiveness in terms of feed and
reduction of methane emission on Sindhi x Yellow cattle. It is not recommended to
replace of 20% fresh cassava forage in diet of cattle because it may lead to the lower
weight gain.
Replacing of 20% copra meal with dried cassava forage in Napier grass diet
does not affect dry matter intake, weight gain and methane emission on Sindhi x
Yellow cattle. In general, replacing of 10% copra meal with 10% dried cassava
forage in diet are more promising outcomes.
5.2 Suggestions
It could be applied the best cattle diets and reduce methane emissions.
Further research may be needed focusing on replacing dried cassava forage or
copra meal with other forage sources to better use locally available forage sources

and contribute to reduce methane emissions in cattle. While continuing research on
methane and carbon dioxide emission from other feeds.

23