Directory UMM :Data Elmu:jurnal:S:Small Ruminant Research:Vol36.Issue3.2000:
Small Ruminant Research 36 (2000) 251±259
Metabolizable energy of roughage in Taiwan
Mei-Ju Leea, Sen-Yuan Hwanga, Peter Wen-Shyg Chioub,*
a
b
Taiwan Livestock Research Institute, Hsin-hua, Tainan, Taiwan
Department of Animal Science, National Chung-Hsing University, Taichung, Taiwan
Accepted 27 September 1999
Abstract
The ®xed metabolizable energy (ME) values from the NRC do not represent the true ME values of the various feedstuff used in
livestock rations. Therefore, a rapid and effective method for evaluating the ME value of forage crops is required for proper ration
formulation to improve production ef®ciency. Dairy goat digestion trials were conducted as the in vivo reference using the method
of Menke and Steingass (1988) [Menke, K.H., Steingass, H., 1988. Feed Sci. Technol. 28, 91±97] which derived the amount of gas
produced from in vitro fermentation. This method was adapted in this study to evaluate the ME value. In the goat digestion trial, six
dairy goats were used for each roughage sample in a total fecal collection trial to determine the digestible nutrients, including energy
(DE) and total digestible nutrient (TDN). The in vivo ME value was calculated using the method of Shiemann et al. (1971)
[Shiemann, R., Nehring, K., Hoffmann, L., Jentsch, W., Chudy, A., 1971. Energetische Futterbewertung und Energienormen. VEB
Deutscher Land-wirtschaftsverlag, Berlin, p. 75. (in German)] (ME1 (MJ/kg) 5.2DCP 34.2DEE 12.8DCF 15.9DNFE,
g/g). The in vitro ME value was then estimated from the chemical composition of the feed and amount of gas produced (Gb) from
in vitro fermentation. The value calculated from both with (ME3) and without (ME2) the inclusion of nitrogen free extracts (NFE)
in the prediction equation. (ME2 (MJ/kg) 0.145Gb 4.12CP 6.5CP2 20.6EE 1.54, g/g; ME3 (MJ/kg) 0.118Gb
8.75CP 19.21EE 3.38NFE 0.691, g/g). The 12 roughage samples consisted different growth stages of Napier grass Taishi
No. 2: (day of harvest; 40, 50, 60 and 65), dwarf Napier grass Taishi No. 1: (Day 40 and 65) and Pangola grass (Day 45) hay (Day 70),
corn silage, imported alfalfa hay, timothy hay and Bermuda hay. The correlation between the ME values calculated from in vivo and
in vitro without NFE was lower than with NFE inclusion in the equation. A higher correlation between the ME values calculated
from in vivo and in vitro without NFE inclusion than with NFE inclusion in the prediction equation was obtained when alfalfa and
corn silage were not included. This indicated that the ME value of forage could be estimated rapidly using this in vitro gas method
adapted from Menke and Steingass (1988) [Menke, K.H., Steingass, H., 1988. Feed Sci. Technol. 28, 91±97] for practical
applications in ration formulation. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Roughage; Metabolizable energy; In vitro method; Gas production
1. Introduction
The nutrient composition including the metabolizable energy (ME) value of roughage varies widely
*
Corresponding author. Tel.: 886-4-2870613;
fax: 886-4-2860265.
E-mail address: wschiou@dragon.nchu.edu.tw (P.W.-S. Chiou)
according to different plant genetics, environment and
management, i.e. the growing season, fertilizer, irrigation, and harvesting stage. At present, forages used in
Taiwan is either imported (alfalfa, timothy and Bermuda) or locally produced (Napier grass, pangola
grass, green corn, corn silage, and by-products:
brewer's dried grain, peanut vine, soybean vine, soybean pod, and soybean curd residues). The ME content
0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 1 2 4 - 8
252
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
of this roughage however, has not been analyzed and
the NRC table values are used instead.
Animal feeding faces a bottleneck because this
important nutrient-energy can not be properly evaluated due to the lack of a rapid and effective method for
ME estimation. Estimation of the ME value in vivo
using cows or goats is tedious and requires labor and
facilities. It is good for research but not for practical
applications in feed formulation and feeding improvement. A rapid and precise in vitro method to evaluate
the ME value for roughage is therefore important for
ef®cient dairy production.
The end products of rumen fermentation are microbial cells, fermentation acids and gas. Measurement of
gas production is a convenient assay of metabolic
activity. Net gas production, although does not give
a direct value, it is correlated with the extent of
digestion (Van Soest, 1982). Application of gas production from forage fermentation to estimate the ME
value was established by Menke et al. (1979) and
Menke and Steingass (1988). The gas measuring
techniques for assessment of the nutritional quality
of feeds has been reviewed by Abreu and BrunoSoares (1998); Getachew et al. (1998) also applied
this technique to estimate the nutritive value of
feedgrain. This study is therefore aimed at the application of gas measurement techniques in establishing
a rapid in vitro method for evaluating the ME value
of different sources of roughage and thus providing
basic information for ration formulation in dairy
feeding.
2.2. In vivo method
2. Material and methods
The digestibility trials were conducted on six
dairy goats in their dry period. The nutrient digestion
coef®cients for each forage sample were measured
using the total fecal collection method according to
Harries (1970). After a 14 day preliminary period in
the metabolic cage with fecal collecting container
behind a screen ¯oor which allowed additional separating the feces and urine through the screen ¯oor with
funnel underneath for urine collection. During the
collection period, forage was cut to 2±9 cm and fed
to the dairy goat at 90% the maximum intake in the
adaptation period. Premix and water was available
all of the time. Feed consumed and feces eliminated
were recorded daily. Total feces were collected for
seven consecutive days and stored at ÿ188C in a
freezer. At the end of the trial, the collected fecal
samples were mixed and 5% of the collected feces
sampled and dried for chemical composition and
energy analysis in order to calculate digestibility.
Samples of the forages were also collected from the
goat digestion trials every day and mixed, dried and
ground at the end of the trial.
The total digestible nutrients (TDN) were also
calculated from the digestible nutrients. The parameters included digestible crude protein (DCP), digestible crude fat (DEE), digestible crude ®ber (DCF) and
digestible nitrogen free extract (DNFE). The metabolizable energy (ME1) was calculated from the digestion coef®cient, which was derived from the in vivo
digestion trial using the equation of Shiemann et al.
(1971), (ME1 15.2DCP 34.2DEE 12.8DCF
15.9DNFE; MJ/kg; g/g).
2.1. Material
2.3. In vitro method
Total of 12 different forage, which included Napier
grass, Pangola grass, corn silage, alfalfa hay, timothy
hay and Bermuda hay were used in this study. The
Napier grass and Pangola grasses used were from
different strains and harvesting stages. These grasses
included the Taishi #2 Napier grass from Day 40, 50,
60 and 65, the Taishi #1 dwarf Napier grass from Days
40 and 65, green chopped Pangola grass from Day 45
and Pangola grass hay from Day 70. The corn silage
was in the milk stage. The alfalfa hay, timothy hay and
Bermuda hay were imported from the USA.
2.3.1. Incubation facilities
Fermentation was carried out in glass-syringes
(piston pipettes) 3.2 cm in internal diameter, 20 cm
in length and 150 ml in volume, which were calibrated at 100 ml. The piston ®t precisely and was
lubricated using a small amount of Vaseline. The
needle of the syringe was connected with a silicon
rubber tube 4±5 cm in length and closed using a plastic
clip. The forage samples were dried at 608C, ground
into 1 mm portions, and placed into fermentation
tubes.
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
2.3.2. Preparation of rumen liquor
The rumen liquor was taken from the rumen ®stula
of a cow that had been fed green chopped Pangola
grass ad libitum with 2 kg of concentrate daily for 14
days, and ®ltered through two layers of cheesecloth.
Rumen liquor, 200 ml, was placed into a special glass,
and then placed into a warm ¯ask ®lled with CO2 and
mixed with arti®cial rumen ¯uid. The arti®cial rumen
¯uid consisted of (added in order) 400 ml H2O, 0.1 ml
solution A, 200 ml solution B, 200 ml solution C, 1 ml
resazurine (0.1%, w/v) solution D, and 40 ml reduction solution E. This mixture was then kept under CO2
in a 398C water bath and stirred using a magnetic
stirrer.
Solution A consisted of 13.2 g CuCl22H2O, 10.0 g
MnCl24H2O, 1.0 g CoCl26H2O, 8.0 g FeCl26H2O
and made up to 100 ml with water. Solution B consisted of 35 g NaHCO3 and 4 g NH4HCO3 added up to
1000 ml with water. Solution C consisted of 5.7 g
Na2HPO4, 6.2 g KH2PO4, 0.6 g MgSO47H2O added
up to 1000 ml with water, The solution D consisted of
0.5 g resazurine up to 100 ml with water. The solution
E is the reduction solution consisted of 95 ml H2O,
4 ml 1 N-NaOH and 625 mg Na2S9H2O.
2.3.3. Incubation
Thirty milliliter of the rumen ¯uid medium-mixture
kept at 398C was placed into each special syringe
using a pipette with an automatic pump. A sample of
forage(0.2 g drymatter)was introduced into thesyringe.
Simultaneously, 0.2 g of standard forage and a mixture
of concentrate and forage, at a ratio of 30±70 was
introduced into the syringe separately. The standard
forage was ryegrass hay with 12.1% CP and 21.1% CF
whereas the concentrate (14.1% CP, 9.6% CF) which
consist of 55% corn grain, 15% barley, 10% soybean
meal, 10% cottonseed and 10% sun¯ower seeds.
Each sample used six replicates. Each replicate of
the sample included one blank tube in the experiment.
Thirty milliliter of arti®cial rumen ¯uid and rumenliquor were added separately. During incubation, any
gas bubbles in the syringe were removed, the plastic
clip on the silicon tube closed, and the position of the
piston recorded and placed in parallel on a disk at
39 0.158C (a disc contained 60 syringes) rotating
automatically for a cultivation period of 24 h. The
rotor stand had two axles. One rotation per minute was
suf®cient for continuous mixing of the contents. Time
253
and temperature were controlled automatically. All of
the positions of the piston were read at 6±8 h intervals
to record gas production. Gas production was not
expected to exceed 60 ml. If 60 ml was exceeded,
the piston was moved back to the 30 ml position. The
®nal reading was taken 24 h after the beginning of
incubation. Moreover, the gas production in the blank
bottle (Gbo), 0 h (U0), 24 h (U24) and the standard
samples were recorded and the net gas production
computed [Gb (U24ÿU0ÿGbo)(FH FHS)/2; where
FH stands for standard hay, FHS for standard concentrate and hay mixture].
2.3.4. Calculation of metabolizable energy
The ME value was calculated from the amount of
gas produced and general chemical composition of the
forage according to the method of Menke and Steingass (1988). The calculation values included ME2
[ME2 0.145Gb 4.12CP 6.5CP2 20.6EE 1.54
(MJ/kg; g/g)] and ME3 [ME3 0.118Gb 8.72CP
19.21EE 3.38NFE 0.691(MJ/kg, g/g)].
2.4. Chemical analysis
Approximate analysis of feed and fecal samples
were performed according to the methods of the
Association of Of®cial Analytical Chemists (1980)
(AOAC, 1980). The gross energy was analyzed using
an Oxygen bomb calorimeter (Parr 1241 Adiabatic
Calorimeter, Parr Instrument Co., USA).
2.5. Statistical analysis
Analysis of the variance and covariance were calculated with the general linear model procedure
(GLM) of the Statistical Analysis System (1985).
Duncan's new multiple range test was used to compare
the treatment means and the correlation between the
ME estimates and signi®cance test were also calculated according to Steel and Torrie (1960).
3. Result and discussion
3.1. In vivo measurement with dairy goats
The chemical composition of the forage samples
was analyzed and is presented in Table 1. Table 2
254
DM (%)
Napier grass
Day 65
Day 60
Day 50
Day 40
Dwarf napier
Day 65
Day 40
Pangola
Hay Day 70
Fresh Day 45
Corn silage
Alfalfa hay
Bermuda hay
Timothy hay
a
CP (%)
EE (%)
CF (%)
Ash (%)
NFE (%)
ADF (%)
GE (kcal/g)
17.0
20.3
18.8
17.1
8.31
7.10
8.75
9.30
2.56
2.83
2.36
2.71
29.88
30.27
30.33
24.81
11.93
10.10
9.15
9.90
47.32
49.70
49.50
54.59
40.92
42.92
40.05
37.88
3.842
3.728
3.797
3.713
20.8
16.7
7.32
10.03
3.01
2.83
29.72
23.59
10.10
9.30
49.85
54.25
43.40
37.2
3.703
3.781
87.1
39.7
23.8
87.5
88.1
88.6
3.04
6.69
8.34
15.03
7.01
9.21
2.00
2.07
2.71
2.51
2.51
2.80
32.00
30.60
30.56
29.61
27.30
28.31
7.02
9.24
5.40
10.78
8.92
9.30
55.94
51.40
52.99
42.07
54.26
50.38
46.64
42.80
37.37
37.80
41.33
40.92
3.965
3.767
3.978
3.842
3.725
3.713
DM: Dry matter; CP: Crude protein; EE: Crude fat; CF: Crude ®ber; NFE: Nitrogen free extract; GE: Gross energy.
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
Table 1
The chemical composition of forage stuffs in Taiwana
255
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
Table 2
The nutrients digestibility of forage by dairy goat trial*
Napier grass
Day 65
Day 60
Day 50
Day 40
Dwarf napier grass
Day 65
Day 40
Pangola grass
Hay, Day 70
Fresh, Day 45
Corn silage
Imported forage
Alfalfa hay
Bermuda hay
Timothy hay
DM
CP
EE
CF
NFE
GE
TDN (%)
Gb (m1/200 mg)
61.0b 2.3
63.2b 6.2
70.4a 2.9
71.2a 2.4
70.4a 2.6
70.6a 1.8
62.5c 1.4
65.2b 1.3
60.4b 1.3
65.3a 3.4
50.9c 4.8
61.2b 2.2
65.4c 1.4
67.3b 1.8
72.9a,b 1.4
75.2a 2.7
62.5b 2.9
65.2b 3.7
75.8a 2.5
74.2a 3.2
63.1d 2.8
66.4c 3.3
71.5b 2.8
75.1a 1.5
58.4d 1.2
61.9b 1.5
67.8b 1.1
69.4a 1.7
43.4d 2.1
47.0c 1.8
48.1b 2.1
52.1a 1.5
64.9b 1.5
72.3a 2.2
70.4a 2.8
66.3b 3.2
64.9b 2.9
65.7a 3.2
66.9b 2.8
76.1a 3.2
68.2b 2.3
75.8a 2.2
65.7b 2.6
74.5a 2.1
63.4b 1.8
69.9a 2.0
49.3b 1.6
54.9a 2.3
54.1b 1.7
79.8a 4.1
65.2 3.5
34.0b 2.0
61.9a 1.3
52.3 0.9
55.2b 2.5
62.3a 5.2
64.4 3.3
54.0b 2.4
81.1a 1.7
68.8 1.0
53.2b 1.0
81.8a 1.3
63.2 3.3
47.1b 0.8
78.2a 4.1
61.2 1.7
50.6b 1.0
74.3a 1.1
63.6 1.8
40.3b 1.9
58.3a 2.5
53.4 1.9
60.2 6. 1
61.5 5.3
62.4 1.3
66.3 2.7
65.2 1.9
67.8 2.3
55.3 3.6
64.1 3.0
63.1 1.7
43.6 1.0
57.1 1.7
70.2 3.4
78.5 1.5
60.1 1.6
65.2 2.5
54.0 2.0
60.0 2.5
63.4 0.9
59.0 1.1
56.4 0.5
62.9 2.0
44.3 1.6
47.1 2.7
48.9 2.5
* a,b,c,d
: Means of the same column within the same forage species with the different superscript were signi®cantly different (P < 0.05).
shows the apparent digestibility of various types of
roughage in the dairy goat digestion trial. In Napier
grass from different growth stages, the digestibility of
DM and NFE from Days 40 and 50 were signi®cantly
higher than those from Days 60 and 65 (P < 0.001).
The CP digestibility from Days 60 and 65 were
signi®cantly higher than those from Days 40 and 50
(P < 0.001). The CP digestibility of Napier grass cut
on Day 40 was higher than that cut on Day 50
(P < 0.05). The digestibility of EE however, did not
show a constant trend. Napier grass cut on Day 60
showed signi®cantly higher EE digestibility than grass
cut on other days. Days 65 and 40 were next. The
digestibility of EE was signi®cantly lowest for Day 50.
The digestibility of CF, GE and hence the TDN value
were signi®cantly highest on Day 40, followed by
Days 50 and 60 in descending order. Digestibility was
signi®cantly lowest for Day 65 (P < 0.05). The digestibility of NFE also showed a similar trend toward a
digestibility decrease as the growth age increased.
Dwarf Napier grass on the other hand, showed
signi®cantly higher digestion in most of the nutrients
including EE, CF, NFE, GE and TDN for Day 40 over
that of Day 65 (P < 0.05). The CP digestibility for Day
65 however was signi®cantly higher than that for Day
40 in dwarf Napier grass (P < 0.05). The nutrient
digestibility for green chopped Pangola grass was also
signi®cantly higher for Day 45 than that for hay on
Day 70 (P < 0.001). This result was similar to the
®ndings of Chen et al. (1973) and Lee et al. (1991).
They indicated that the digestibility of DM, CF, NFE,
GE and hence the TDN value in Napeir and Pangola
grasses were higher at the earlier stages of growth and
decreased as the plant approached maturity. In this
trial, the digestibility of Napier and dwarf Napier
grasses however showed a lower CP in the early stage
than that in the late growing stages. This lower CP
digestibility in the early growth stages did not agree
with most of the results. Since fecal nitrogen loss and
negative nitrogen balance can be exacerbated by the
addition of highly digestible carbohydrates to a low
nitrogen diet (Van Soest, 1982). The high NFE with
low CP content in the early Napier grass growth stage
may result in an increase nitrogen loss, hence a
decrease in CP digestibility. Furthermore, the digestibility of most of the nutrients in Pangola grass hay
from Day 70 was signi®cantly lower than that from
Day 45, especially for crude protein. This extremely
low CP digestibility from Day 45 may be because of
the great amount of rainfall, which caused much of the
nitrogen to run off. The grass also became over-mature
in that summer. Hsu et al. (1990, 1993) also suggested
that the most appropriate period to harvest Pangola
and Napier grass was at 6±8 weeks of growth because
256
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
the digestibility of DM and other nutrients was richest
at this stage of growth. The DM digestibility and TDN
of grasses over 8 weeks of growth determined by the in
vitro method of Tilley and Terry (1963) declined as
growth advanced. Pangola grass harvested on Day 70
was over mature, with ligni®ed cell walls lowering the
digestibility. Van Soest (1982) suggested that a decline
in digestibility occurred as grass is harvested later in
its growing stage because of the ligni®cation in the cell
walls.
The DM, CP, EE, CF, GE digestibility of corn silage
was lower than the values for regular corn silage,
especially for CP, hence the lower TDN value
(63.6%) shown in this trial. This low digestibility
might be attributed to both the harvesting stage and
chopping. Corn used in this trial was harvested in the
milk stage and chopped to 5±6 cm in length. This
processing might cause dif®culties for goats to completely masticate the corn ear. High water content in
the forage corn may also result in a poor ensiled
quality (75%) with lower digestibility.
The imported alfalfa hay contained only 15% CP
which re¯ected over mature harvesting. The digestible
nutrients and TDN were similar in both dairy goats
and dairy cows when fed the same grades of alfalfa
(National Research Council, 1988). The digestibility
of the imported Bermuda hay and timothy hay were
intermediate to that of Pangola and Napier grass
harvested at Day-60 with a TDN of 56.4 and
62.9%, respectively. These values were also close to
the (National Research Council, 1988) estimations for
dairy cattle.
3.2. Correlation of ME estimated from the in vivo
and in vitro trials
Table 3 presents different prediction equations.
Table 4 presents the DE, TDN and ME of the forage
plants used in Taiwan. The correlation coef®cients of
the different ME estimate are presented Table 5.
In a comparison of the in vivo estimates of energy
values, the relationship between ME values from in
vivo trial, ME1, TDN and DE was highly correlated.
The correlation coef®cient was 0.9981 for TDN and
ME1, and 0.9997 for DE and ME1 with the 12 different
forages (n 12). When ME estimates were compared
with in vivo estimates (ME1) and in vitro gas production (ME2 and ME3), the correlation between the ME1
estimated from in vitro gas production and the ME2
from the gas production, CP and EE was high. But the
correlation was still lower (r 0.8790) than the ME1
and ME3 (r 0.8872) that included variable NFE into
the predict equation in addition to the variables of
ME2.
In a comparison of the ME estimates from the in
vivo (ME1) with the NRC (ME4) and the in vitro gas
production (ME2 and ME3), the correlation of ME1
and ME4 (r 0.9444, P < 0.0001) was higher than
both the correlation of ME2 and ME4 (r 0.8790,
P < 0.0001). It was also higher than the correlation of
ME3 and ME4 (r 0.8872, P < 0.0001). Since both
ME1 and ME4 were calculated from same set of data
derived from in vivo dairy goat digestion trial. From
higher correlation coef®cient of ME3 and ME1 to the
correlation of ME2 and ME1, and ME3 and ME4 to
Table 3
The predict equations of metabolizable energya
Item
Equation for ME estimation
Source
ME1
ME2
ME3
ME4
ME5
ME6
ME7
ME8
15.2DCP 34.2DEE 12.8DCF 15.9DNFE
0.145Gb 0.00412CP 0.00650CP2 0.0206fat 1.54
0.118Gb 8.72CP 19.21fat 3.38NFE 0.691
0.82DE
3.16 0.0695Gb 0.00007300 G2b 0.00732CP 0.02052fat
1.56 0.1390Gb 0.007400CP 0.01780fat
ÿ0.58 0.1590Gb 0.0102CP 0.03140fat
1.20 0.1456Gb 0.00076575CP 0.01642fat
In vitro digestion trial
Menke et al., 1979
Menke et al., 1979
National Research Council, 1988
Steingass, 1980
Close and Menke, 1986
Rohr et al., 1986
SchoÈner, 1981
a
DE: Digestibility of gross energy; TDN: Total Digestible of nutrient, where DCP, DEE, DCF, DNFE g digestible crude protein, fat,
®ber and N-free extracts/g DM of feedstuff, respectively, and where CP, EE and NFE represents crude protein, crude fat and N-free extracts;
Gb: Gas production by in vitro fermentation.
257
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
Table 4
The digestible energy, TDN and ME of forage stuffs in Taiwan
Item
DE (MJ/kg)
ME1 (MJ/kg)
Napier grass
Day 65
Day 60
Day 50
Day 40
10.15
10.35
11.35
11.67
8.62
9.15
10.04
10.31
8.38
8.77
9.08
9.75
8.64
9.07
9.25
10.01
8.32
8.49
9.31
9.57
Dwarf Napier grass
Day 65
Day 40
10.18
11.79
9.40
10.48
9.12
10.25
9.41
10.42
8.35
9.66
Pangola grass
Hay Day 70
Fresh Day 45
Corn silage
Alfalfa hay
Bermuda hay
Timothy hay
7.82
12.33
10.18
8.67
9.35
9.85
7.36
11.00
9.31
8.89
8.43
9.32
7.48
10.35
9.83
9.54
8.77
9.28
7.82
10.31
10.04
9.13
9.18
9.50
6.41
10.11
8.35
7.11
7.67
8.08
ME2 and ME4, this indicated that when all of the 12
forages were evaluated, ME3 was highly correlated to
in vivo estimates as compared to that for ME2. It
appears that the ME estimate on all forages measured
ME2 (MJ/kg)
ME3 (MJ/kg)
ME4 (MJ/kg)
will be more precise with NFE inclusion in their
equation.
Comparison of the ME4 of the NRC estimate to the
other in vivo result without inclusion of corn silage
Table 5
The correlation coef®cients of metabolizable energy estimatesa
Item
DE
DE
TDN
ME1
ME2
ME3
ME4
ME5
ME6
ME7
ME8
a
0.9981
0.0001
0.9997
0.0001
0.7747
0.0051
0.7602
0.0001
0.8745
0.002
0.6562
0.0001
0.6591
0.0001
0.6585
0.0001
0.8519
0.0001
TDN
ME1
ME2
ME3
ME4
ME5
ME6
ME7
ME8
0.9980
0.0001
0.9980
0.0001
0.9998
0.0001
0.9024
0.0001
0.9416
0.0001
0.9521
0.0001
0.8874
0.0002
0.9126
0.0007
0.9272
0.0001
0.8297
0.0016
0.7825
0.0044
0.7600
0.0066
0.9673
0.0001
0.9024
0.0001
0.8774
0.0001
0.8198
0.0001
0.8231
0.0001
0.8302
0.0001
0.9806
0.0001
0.9554
0.0001
0.9995
0.0001
0.8177
0.0001
0.8252
0.0001
0.8352
0.0001
0.9845
0.0001
0.9627
0.0001
1.000
0.0001
0.9999
0.0001
0.8174
0.0001
0.8290
0.0001
0.8368
0.0001
0.9856
0.0001
0.9644
0.0001
0.9999
0.0001
0.9993
0.0001
0.9999
0.0001
0.8837
0.0001
0.9287
0.0001
0.9283
0.0001
0.8242
0.0001
0.7953
0.0001
0.7877
0.0001
0.7849
0.0001
0.7877
0.0001
0.7890
0.0001
0.9981
0.0001
0.8608
0.001
0.8753
0.0002
0.9410
0.0001
0.7697
0.0001
0.7805
0.0001
0.7817
0.0001
0.8411
0.0001
0.8790
0.0001
0.8872
0.0001
0.9444
0.0001
0.7720
0.0001
0.7832
0.0001
0.7843
0.0001
0.8385
0.0001
0.9652
0.0001
0.8790
0.0001
0.8841
0.0001
0.8773
0.0001
0.8820
0.0001
0.5059
0.0001
0.8872
0.0001
0.9481
0.0001
0.9452
0.0001
0.9485
0.0001
0.5820
0.0001
0.9996
0.0001
1.0000
0.0001
0.9999
0.0001
0.6083
0.0001
0.9995
0.0001
0.9993
0.0001
0.7849
0.0001
0.9999
0.0001
0.6083
0.0001
0.6083
0.0001
The correlation coef®cient values in the lower and left side of diagonal of the table were calculated on the ME value which derived from
forages without inclusion of corn silage and alfalfa hay (n 10). The right and upper side of the table content values derived from ME values
of the 12 feeds (n 12).
258
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
and alfalfa (n 10), the correlation between ME1 and
ME4 was the highest (r 0.9673, P < 0.0001). The
correlation coef®cient for ME1 and ME2 (r 0.9521,
P < 0.0001) was higher than the correlation for ME1
and ME3 (r 0.9272, P < 0.0001) from the remaining
10 forages. The correlation of ME2 and ME4
(r 0.9024, P < 0.0001) was also higher than the
correlation of ME3 and ME4 (r 0.8774,
P < 0.0001). This indicated that ME2 and ME3 were
appropriate for estimating the ME of forage. ME2
was more practical for estimating the ME of forage
than ME3. This represents that inclusion of NFE
in addition to EE, CP and gas production in the
predicted equation did not improve the precision
of the ME estimates. For forage, both CF and NFE
procedures are known to be inadequate for accurate
determinations. The CF method tends to underestimate true ®ber content, especially in immature forage
with high hemicellulose content. Data presented in
Table 2 clearly demonstrates this concept as CF values
which are suppose to represent total ®ber are consistently lower than ADF which represents only the
cellulose content of the forage. Therefore, CF should
be replaced by ADF in the predicting equation to
improve the precision. The ME estimated on tropical
forage will be more precise without NFE inclusion
in the equation.
The NFE procedure also tends to overestimate
values for forage. The values presented in Table 2
are considerably high. The actual values for starch
would be much less. Take Bermuda grass for example,
Sniffer et al. (1992) indicated 79.5% carbohydrate
(CHO) with 66.6% ®brous and 12.9% non-®brous
CHO with only 0.8% starch and 53.1% slow degradable CHO. From our laboratory showed that Napier
grass with 56.0% ®brous CHO and 29.4% non-®brous
CHO with only 1.7% starch and 46.5% slow degradable CHO (unpublished data). Since high correlation
achieved in this trial, it appears that underestimation of
total ®ber was compensated for by an overestimation
of soluble carbohydrates.
The estimates for forage ME, which were derived
from in vitro methods using gas production, CP and
EE to calculate ME value (ME2) was initiated by
Menke et al. (1979) and were modi®ed by Menke
and Steingass (1988). This revised equation is
ME6 1.56 0.1390Gb 0.007400CP 0.01780EE. The correlation of ME6 and ME1 estimated from
the goat digestion trial in this study (r 0.7832) was
lower where the correlation of ME6 and ME2
(r 0.8773) was lower than that of the correlation
of ME6 and ME3 (r 0.9452). When comparing the
ME estimates of gas production, CP and EE from this
study to other data, the correlation coef®cients were
also very high. The ME1 and ME5 (r 0.7720), which
were estimated from the goat digestion trial (Steingass
and Menke, 1980) and ME7 (Rohr et al., 1986) and
ME8 (SchoÈner, 1981) which was calculated using
regression were high. These values however were still
lower than correlation coef®cient determined from
ME1 and ME2.
The amount of gas produced from this trial showed
a trend toward decreasing as the period of forage
growth advanced. The average gas production was
around 40±58 ml/200 mg (Table 2) and agreed with
the value of Zinash et al. (1996). They also found a
decrease in gas production as the forage growing
period was prolonged.
It appears that the ME of forage estimated from this
trial is easy to measure and provides a reasonable
estimate and can be used to replace the digestion trial.
This however, can not provide precise estimates for
lactating dairy goat because this study utilized dried
dairy goats at a maintenance level to generate the in
vivo data. Lactation stage has a great impact on
nutrient intake and subsequently, nutrient digestibility
and utilization.
4. Conclusion
The correlation coef®cient of metabolizable energy
estimated from the gross energy digestibility, total
digestible nutrients determined by the dairy goat
digestion trial and metabolizable energy estimated
from the digestible nutrients and gas production using
the Menke and Steingass (1988) in vitro method was
high. The in vitro ME estimate for forage can be
applied in Taiwan, because it not only is rapid, convenient and cost saving, but is also suitable for application to dairy goats and cattle. It can be adapted to
evaluate various sources of forage with different
compositions and provide data for the most important
nutrients and energy sources, for proper ration formulation in dairy farming.
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
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Metabolizable energy of roughage in Taiwan
Mei-Ju Leea, Sen-Yuan Hwanga, Peter Wen-Shyg Chioub,*
a
b
Taiwan Livestock Research Institute, Hsin-hua, Tainan, Taiwan
Department of Animal Science, National Chung-Hsing University, Taichung, Taiwan
Accepted 27 September 1999
Abstract
The ®xed metabolizable energy (ME) values from the NRC do not represent the true ME values of the various feedstuff used in
livestock rations. Therefore, a rapid and effective method for evaluating the ME value of forage crops is required for proper ration
formulation to improve production ef®ciency. Dairy goat digestion trials were conducted as the in vivo reference using the method
of Menke and Steingass (1988) [Menke, K.H., Steingass, H., 1988. Feed Sci. Technol. 28, 91±97] which derived the amount of gas
produced from in vitro fermentation. This method was adapted in this study to evaluate the ME value. In the goat digestion trial, six
dairy goats were used for each roughage sample in a total fecal collection trial to determine the digestible nutrients, including energy
(DE) and total digestible nutrient (TDN). The in vivo ME value was calculated using the method of Shiemann et al. (1971)
[Shiemann, R., Nehring, K., Hoffmann, L., Jentsch, W., Chudy, A., 1971. Energetische Futterbewertung und Energienormen. VEB
Deutscher Land-wirtschaftsverlag, Berlin, p. 75. (in German)] (ME1 (MJ/kg) 5.2DCP 34.2DEE 12.8DCF 15.9DNFE,
g/g). The in vitro ME value was then estimated from the chemical composition of the feed and amount of gas produced (Gb) from
in vitro fermentation. The value calculated from both with (ME3) and without (ME2) the inclusion of nitrogen free extracts (NFE)
in the prediction equation. (ME2 (MJ/kg) 0.145Gb 4.12CP 6.5CP2 20.6EE 1.54, g/g; ME3 (MJ/kg) 0.118Gb
8.75CP 19.21EE 3.38NFE 0.691, g/g). The 12 roughage samples consisted different growth stages of Napier grass Taishi
No. 2: (day of harvest; 40, 50, 60 and 65), dwarf Napier grass Taishi No. 1: (Day 40 and 65) and Pangola grass (Day 45) hay (Day 70),
corn silage, imported alfalfa hay, timothy hay and Bermuda hay. The correlation between the ME values calculated from in vivo and
in vitro without NFE was lower than with NFE inclusion in the equation. A higher correlation between the ME values calculated
from in vivo and in vitro without NFE inclusion than with NFE inclusion in the prediction equation was obtained when alfalfa and
corn silage were not included. This indicated that the ME value of forage could be estimated rapidly using this in vitro gas method
adapted from Menke and Steingass (1988) [Menke, K.H., Steingass, H., 1988. Feed Sci. Technol. 28, 91±97] for practical
applications in ration formulation. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Roughage; Metabolizable energy; In vitro method; Gas production
1. Introduction
The nutrient composition including the metabolizable energy (ME) value of roughage varies widely
*
Corresponding author. Tel.: 886-4-2870613;
fax: 886-4-2860265.
E-mail address: wschiou@dragon.nchu.edu.tw (P.W.-S. Chiou)
according to different plant genetics, environment and
management, i.e. the growing season, fertilizer, irrigation, and harvesting stage. At present, forages used in
Taiwan is either imported (alfalfa, timothy and Bermuda) or locally produced (Napier grass, pangola
grass, green corn, corn silage, and by-products:
brewer's dried grain, peanut vine, soybean vine, soybean pod, and soybean curd residues). The ME content
0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 1 2 4 - 8
252
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
of this roughage however, has not been analyzed and
the NRC table values are used instead.
Animal feeding faces a bottleneck because this
important nutrient-energy can not be properly evaluated due to the lack of a rapid and effective method for
ME estimation. Estimation of the ME value in vivo
using cows or goats is tedious and requires labor and
facilities. It is good for research but not for practical
applications in feed formulation and feeding improvement. A rapid and precise in vitro method to evaluate
the ME value for roughage is therefore important for
ef®cient dairy production.
The end products of rumen fermentation are microbial cells, fermentation acids and gas. Measurement of
gas production is a convenient assay of metabolic
activity. Net gas production, although does not give
a direct value, it is correlated with the extent of
digestion (Van Soest, 1982). Application of gas production from forage fermentation to estimate the ME
value was established by Menke et al. (1979) and
Menke and Steingass (1988). The gas measuring
techniques for assessment of the nutritional quality
of feeds has been reviewed by Abreu and BrunoSoares (1998); Getachew et al. (1998) also applied
this technique to estimate the nutritive value of
feedgrain. This study is therefore aimed at the application of gas measurement techniques in establishing
a rapid in vitro method for evaluating the ME value
of different sources of roughage and thus providing
basic information for ration formulation in dairy
feeding.
2.2. In vivo method
2. Material and methods
The digestibility trials were conducted on six
dairy goats in their dry period. The nutrient digestion
coef®cients for each forage sample were measured
using the total fecal collection method according to
Harries (1970). After a 14 day preliminary period in
the metabolic cage with fecal collecting container
behind a screen ¯oor which allowed additional separating the feces and urine through the screen ¯oor with
funnel underneath for urine collection. During the
collection period, forage was cut to 2±9 cm and fed
to the dairy goat at 90% the maximum intake in the
adaptation period. Premix and water was available
all of the time. Feed consumed and feces eliminated
were recorded daily. Total feces were collected for
seven consecutive days and stored at ÿ188C in a
freezer. At the end of the trial, the collected fecal
samples were mixed and 5% of the collected feces
sampled and dried for chemical composition and
energy analysis in order to calculate digestibility.
Samples of the forages were also collected from the
goat digestion trials every day and mixed, dried and
ground at the end of the trial.
The total digestible nutrients (TDN) were also
calculated from the digestible nutrients. The parameters included digestible crude protein (DCP), digestible crude fat (DEE), digestible crude ®ber (DCF) and
digestible nitrogen free extract (DNFE). The metabolizable energy (ME1) was calculated from the digestion coef®cient, which was derived from the in vivo
digestion trial using the equation of Shiemann et al.
(1971), (ME1 15.2DCP 34.2DEE 12.8DCF
15.9DNFE; MJ/kg; g/g).
2.1. Material
2.3. In vitro method
Total of 12 different forage, which included Napier
grass, Pangola grass, corn silage, alfalfa hay, timothy
hay and Bermuda hay were used in this study. The
Napier grass and Pangola grasses used were from
different strains and harvesting stages. These grasses
included the Taishi #2 Napier grass from Day 40, 50,
60 and 65, the Taishi #1 dwarf Napier grass from Days
40 and 65, green chopped Pangola grass from Day 45
and Pangola grass hay from Day 70. The corn silage
was in the milk stage. The alfalfa hay, timothy hay and
Bermuda hay were imported from the USA.
2.3.1. Incubation facilities
Fermentation was carried out in glass-syringes
(piston pipettes) 3.2 cm in internal diameter, 20 cm
in length and 150 ml in volume, which were calibrated at 100 ml. The piston ®t precisely and was
lubricated using a small amount of Vaseline. The
needle of the syringe was connected with a silicon
rubber tube 4±5 cm in length and closed using a plastic
clip. The forage samples were dried at 608C, ground
into 1 mm portions, and placed into fermentation
tubes.
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
2.3.2. Preparation of rumen liquor
The rumen liquor was taken from the rumen ®stula
of a cow that had been fed green chopped Pangola
grass ad libitum with 2 kg of concentrate daily for 14
days, and ®ltered through two layers of cheesecloth.
Rumen liquor, 200 ml, was placed into a special glass,
and then placed into a warm ¯ask ®lled with CO2 and
mixed with arti®cial rumen ¯uid. The arti®cial rumen
¯uid consisted of (added in order) 400 ml H2O, 0.1 ml
solution A, 200 ml solution B, 200 ml solution C, 1 ml
resazurine (0.1%, w/v) solution D, and 40 ml reduction solution E. This mixture was then kept under CO2
in a 398C water bath and stirred using a magnetic
stirrer.
Solution A consisted of 13.2 g CuCl22H2O, 10.0 g
MnCl24H2O, 1.0 g CoCl26H2O, 8.0 g FeCl26H2O
and made up to 100 ml with water. Solution B consisted of 35 g NaHCO3 and 4 g NH4HCO3 added up to
1000 ml with water. Solution C consisted of 5.7 g
Na2HPO4, 6.2 g KH2PO4, 0.6 g MgSO47H2O added
up to 1000 ml with water, The solution D consisted of
0.5 g resazurine up to 100 ml with water. The solution
E is the reduction solution consisted of 95 ml H2O,
4 ml 1 N-NaOH and 625 mg Na2S9H2O.
2.3.3. Incubation
Thirty milliliter of the rumen ¯uid medium-mixture
kept at 398C was placed into each special syringe
using a pipette with an automatic pump. A sample of
forage(0.2 g drymatter)was introduced into thesyringe.
Simultaneously, 0.2 g of standard forage and a mixture
of concentrate and forage, at a ratio of 30±70 was
introduced into the syringe separately. The standard
forage was ryegrass hay with 12.1% CP and 21.1% CF
whereas the concentrate (14.1% CP, 9.6% CF) which
consist of 55% corn grain, 15% barley, 10% soybean
meal, 10% cottonseed and 10% sun¯ower seeds.
Each sample used six replicates. Each replicate of
the sample included one blank tube in the experiment.
Thirty milliliter of arti®cial rumen ¯uid and rumenliquor were added separately. During incubation, any
gas bubbles in the syringe were removed, the plastic
clip on the silicon tube closed, and the position of the
piston recorded and placed in parallel on a disk at
39 0.158C (a disc contained 60 syringes) rotating
automatically for a cultivation period of 24 h. The
rotor stand had two axles. One rotation per minute was
suf®cient for continuous mixing of the contents. Time
253
and temperature were controlled automatically. All of
the positions of the piston were read at 6±8 h intervals
to record gas production. Gas production was not
expected to exceed 60 ml. If 60 ml was exceeded,
the piston was moved back to the 30 ml position. The
®nal reading was taken 24 h after the beginning of
incubation. Moreover, the gas production in the blank
bottle (Gbo), 0 h (U0), 24 h (U24) and the standard
samples were recorded and the net gas production
computed [Gb (U24ÿU0ÿGbo)(FH FHS)/2; where
FH stands for standard hay, FHS for standard concentrate and hay mixture].
2.3.4. Calculation of metabolizable energy
The ME value was calculated from the amount of
gas produced and general chemical composition of the
forage according to the method of Menke and Steingass (1988). The calculation values included ME2
[ME2 0.145Gb 4.12CP 6.5CP2 20.6EE 1.54
(MJ/kg; g/g)] and ME3 [ME3 0.118Gb 8.72CP
19.21EE 3.38NFE 0.691(MJ/kg, g/g)].
2.4. Chemical analysis
Approximate analysis of feed and fecal samples
were performed according to the methods of the
Association of Of®cial Analytical Chemists (1980)
(AOAC, 1980). The gross energy was analyzed using
an Oxygen bomb calorimeter (Parr 1241 Adiabatic
Calorimeter, Parr Instrument Co., USA).
2.5. Statistical analysis
Analysis of the variance and covariance were calculated with the general linear model procedure
(GLM) of the Statistical Analysis System (1985).
Duncan's new multiple range test was used to compare
the treatment means and the correlation between the
ME estimates and signi®cance test were also calculated according to Steel and Torrie (1960).
3. Result and discussion
3.1. In vivo measurement with dairy goats
The chemical composition of the forage samples
was analyzed and is presented in Table 1. Table 2
254
DM (%)
Napier grass
Day 65
Day 60
Day 50
Day 40
Dwarf napier
Day 65
Day 40
Pangola
Hay Day 70
Fresh Day 45
Corn silage
Alfalfa hay
Bermuda hay
Timothy hay
a
CP (%)
EE (%)
CF (%)
Ash (%)
NFE (%)
ADF (%)
GE (kcal/g)
17.0
20.3
18.8
17.1
8.31
7.10
8.75
9.30
2.56
2.83
2.36
2.71
29.88
30.27
30.33
24.81
11.93
10.10
9.15
9.90
47.32
49.70
49.50
54.59
40.92
42.92
40.05
37.88
3.842
3.728
3.797
3.713
20.8
16.7
7.32
10.03
3.01
2.83
29.72
23.59
10.10
9.30
49.85
54.25
43.40
37.2
3.703
3.781
87.1
39.7
23.8
87.5
88.1
88.6
3.04
6.69
8.34
15.03
7.01
9.21
2.00
2.07
2.71
2.51
2.51
2.80
32.00
30.60
30.56
29.61
27.30
28.31
7.02
9.24
5.40
10.78
8.92
9.30
55.94
51.40
52.99
42.07
54.26
50.38
46.64
42.80
37.37
37.80
41.33
40.92
3.965
3.767
3.978
3.842
3.725
3.713
DM: Dry matter; CP: Crude protein; EE: Crude fat; CF: Crude ®ber; NFE: Nitrogen free extract; GE: Gross energy.
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
Table 1
The chemical composition of forage stuffs in Taiwana
255
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
Table 2
The nutrients digestibility of forage by dairy goat trial*
Napier grass
Day 65
Day 60
Day 50
Day 40
Dwarf napier grass
Day 65
Day 40
Pangola grass
Hay, Day 70
Fresh, Day 45
Corn silage
Imported forage
Alfalfa hay
Bermuda hay
Timothy hay
DM
CP
EE
CF
NFE
GE
TDN (%)
Gb (m1/200 mg)
61.0b 2.3
63.2b 6.2
70.4a 2.9
71.2a 2.4
70.4a 2.6
70.6a 1.8
62.5c 1.4
65.2b 1.3
60.4b 1.3
65.3a 3.4
50.9c 4.8
61.2b 2.2
65.4c 1.4
67.3b 1.8
72.9a,b 1.4
75.2a 2.7
62.5b 2.9
65.2b 3.7
75.8a 2.5
74.2a 3.2
63.1d 2.8
66.4c 3.3
71.5b 2.8
75.1a 1.5
58.4d 1.2
61.9b 1.5
67.8b 1.1
69.4a 1.7
43.4d 2.1
47.0c 1.8
48.1b 2.1
52.1a 1.5
64.9b 1.5
72.3a 2.2
70.4a 2.8
66.3b 3.2
64.9b 2.9
65.7a 3.2
66.9b 2.8
76.1a 3.2
68.2b 2.3
75.8a 2.2
65.7b 2.6
74.5a 2.1
63.4b 1.8
69.9a 2.0
49.3b 1.6
54.9a 2.3
54.1b 1.7
79.8a 4.1
65.2 3.5
34.0b 2.0
61.9a 1.3
52.3 0.9
55.2b 2.5
62.3a 5.2
64.4 3.3
54.0b 2.4
81.1a 1.7
68.8 1.0
53.2b 1.0
81.8a 1.3
63.2 3.3
47.1b 0.8
78.2a 4.1
61.2 1.7
50.6b 1.0
74.3a 1.1
63.6 1.8
40.3b 1.9
58.3a 2.5
53.4 1.9
60.2 6. 1
61.5 5.3
62.4 1.3
66.3 2.7
65.2 1.9
67.8 2.3
55.3 3.6
64.1 3.0
63.1 1.7
43.6 1.0
57.1 1.7
70.2 3.4
78.5 1.5
60.1 1.6
65.2 2.5
54.0 2.0
60.0 2.5
63.4 0.9
59.0 1.1
56.4 0.5
62.9 2.0
44.3 1.6
47.1 2.7
48.9 2.5
* a,b,c,d
: Means of the same column within the same forage species with the different superscript were signi®cantly different (P < 0.05).
shows the apparent digestibility of various types of
roughage in the dairy goat digestion trial. In Napier
grass from different growth stages, the digestibility of
DM and NFE from Days 40 and 50 were signi®cantly
higher than those from Days 60 and 65 (P < 0.001).
The CP digestibility from Days 60 and 65 were
signi®cantly higher than those from Days 40 and 50
(P < 0.001). The CP digestibility of Napier grass cut
on Day 40 was higher than that cut on Day 50
(P < 0.05). The digestibility of EE however, did not
show a constant trend. Napier grass cut on Day 60
showed signi®cantly higher EE digestibility than grass
cut on other days. Days 65 and 40 were next. The
digestibility of EE was signi®cantly lowest for Day 50.
The digestibility of CF, GE and hence the TDN value
were signi®cantly highest on Day 40, followed by
Days 50 and 60 in descending order. Digestibility was
signi®cantly lowest for Day 65 (P < 0.05). The digestibility of NFE also showed a similar trend toward a
digestibility decrease as the growth age increased.
Dwarf Napier grass on the other hand, showed
signi®cantly higher digestion in most of the nutrients
including EE, CF, NFE, GE and TDN for Day 40 over
that of Day 65 (P < 0.05). The CP digestibility for Day
65 however was signi®cantly higher than that for Day
40 in dwarf Napier grass (P < 0.05). The nutrient
digestibility for green chopped Pangola grass was also
signi®cantly higher for Day 45 than that for hay on
Day 70 (P < 0.001). This result was similar to the
®ndings of Chen et al. (1973) and Lee et al. (1991).
They indicated that the digestibility of DM, CF, NFE,
GE and hence the TDN value in Napeir and Pangola
grasses were higher at the earlier stages of growth and
decreased as the plant approached maturity. In this
trial, the digestibility of Napier and dwarf Napier
grasses however showed a lower CP in the early stage
than that in the late growing stages. This lower CP
digestibility in the early growth stages did not agree
with most of the results. Since fecal nitrogen loss and
negative nitrogen balance can be exacerbated by the
addition of highly digestible carbohydrates to a low
nitrogen diet (Van Soest, 1982). The high NFE with
low CP content in the early Napier grass growth stage
may result in an increase nitrogen loss, hence a
decrease in CP digestibility. Furthermore, the digestibility of most of the nutrients in Pangola grass hay
from Day 70 was signi®cantly lower than that from
Day 45, especially for crude protein. This extremely
low CP digestibility from Day 45 may be because of
the great amount of rainfall, which caused much of the
nitrogen to run off. The grass also became over-mature
in that summer. Hsu et al. (1990, 1993) also suggested
that the most appropriate period to harvest Pangola
and Napier grass was at 6±8 weeks of growth because
256
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
the digestibility of DM and other nutrients was richest
at this stage of growth. The DM digestibility and TDN
of grasses over 8 weeks of growth determined by the in
vitro method of Tilley and Terry (1963) declined as
growth advanced. Pangola grass harvested on Day 70
was over mature, with ligni®ed cell walls lowering the
digestibility. Van Soest (1982) suggested that a decline
in digestibility occurred as grass is harvested later in
its growing stage because of the ligni®cation in the cell
walls.
The DM, CP, EE, CF, GE digestibility of corn silage
was lower than the values for regular corn silage,
especially for CP, hence the lower TDN value
(63.6%) shown in this trial. This low digestibility
might be attributed to both the harvesting stage and
chopping. Corn used in this trial was harvested in the
milk stage and chopped to 5±6 cm in length. This
processing might cause dif®culties for goats to completely masticate the corn ear. High water content in
the forage corn may also result in a poor ensiled
quality (75%) with lower digestibility.
The imported alfalfa hay contained only 15% CP
which re¯ected over mature harvesting. The digestible
nutrients and TDN were similar in both dairy goats
and dairy cows when fed the same grades of alfalfa
(National Research Council, 1988). The digestibility
of the imported Bermuda hay and timothy hay were
intermediate to that of Pangola and Napier grass
harvested at Day-60 with a TDN of 56.4 and
62.9%, respectively. These values were also close to
the (National Research Council, 1988) estimations for
dairy cattle.
3.2. Correlation of ME estimated from the in vivo
and in vitro trials
Table 3 presents different prediction equations.
Table 4 presents the DE, TDN and ME of the forage
plants used in Taiwan. The correlation coef®cients of
the different ME estimate are presented Table 5.
In a comparison of the in vivo estimates of energy
values, the relationship between ME values from in
vivo trial, ME1, TDN and DE was highly correlated.
The correlation coef®cient was 0.9981 for TDN and
ME1, and 0.9997 for DE and ME1 with the 12 different
forages (n 12). When ME estimates were compared
with in vivo estimates (ME1) and in vitro gas production (ME2 and ME3), the correlation between the ME1
estimated from in vitro gas production and the ME2
from the gas production, CP and EE was high. But the
correlation was still lower (r 0.8790) than the ME1
and ME3 (r 0.8872) that included variable NFE into
the predict equation in addition to the variables of
ME2.
In a comparison of the ME estimates from the in
vivo (ME1) with the NRC (ME4) and the in vitro gas
production (ME2 and ME3), the correlation of ME1
and ME4 (r 0.9444, P < 0.0001) was higher than
both the correlation of ME2 and ME4 (r 0.8790,
P < 0.0001). It was also higher than the correlation of
ME3 and ME4 (r 0.8872, P < 0.0001). Since both
ME1 and ME4 were calculated from same set of data
derived from in vivo dairy goat digestion trial. From
higher correlation coef®cient of ME3 and ME1 to the
correlation of ME2 and ME1, and ME3 and ME4 to
Table 3
The predict equations of metabolizable energya
Item
Equation for ME estimation
Source
ME1
ME2
ME3
ME4
ME5
ME6
ME7
ME8
15.2DCP 34.2DEE 12.8DCF 15.9DNFE
0.145Gb 0.00412CP 0.00650CP2 0.0206fat 1.54
0.118Gb 8.72CP 19.21fat 3.38NFE 0.691
0.82DE
3.16 0.0695Gb 0.00007300 G2b 0.00732CP 0.02052fat
1.56 0.1390Gb 0.007400CP 0.01780fat
ÿ0.58 0.1590Gb 0.0102CP 0.03140fat
1.20 0.1456Gb 0.00076575CP 0.01642fat
In vitro digestion trial
Menke et al., 1979
Menke et al., 1979
National Research Council, 1988
Steingass, 1980
Close and Menke, 1986
Rohr et al., 1986
SchoÈner, 1981
a
DE: Digestibility of gross energy; TDN: Total Digestible of nutrient, where DCP, DEE, DCF, DNFE g digestible crude protein, fat,
®ber and N-free extracts/g DM of feedstuff, respectively, and where CP, EE and NFE represents crude protein, crude fat and N-free extracts;
Gb: Gas production by in vitro fermentation.
257
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
Table 4
The digestible energy, TDN and ME of forage stuffs in Taiwan
Item
DE (MJ/kg)
ME1 (MJ/kg)
Napier grass
Day 65
Day 60
Day 50
Day 40
10.15
10.35
11.35
11.67
8.62
9.15
10.04
10.31
8.38
8.77
9.08
9.75
8.64
9.07
9.25
10.01
8.32
8.49
9.31
9.57
Dwarf Napier grass
Day 65
Day 40
10.18
11.79
9.40
10.48
9.12
10.25
9.41
10.42
8.35
9.66
Pangola grass
Hay Day 70
Fresh Day 45
Corn silage
Alfalfa hay
Bermuda hay
Timothy hay
7.82
12.33
10.18
8.67
9.35
9.85
7.36
11.00
9.31
8.89
8.43
9.32
7.48
10.35
9.83
9.54
8.77
9.28
7.82
10.31
10.04
9.13
9.18
9.50
6.41
10.11
8.35
7.11
7.67
8.08
ME2 and ME4, this indicated that when all of the 12
forages were evaluated, ME3 was highly correlated to
in vivo estimates as compared to that for ME2. It
appears that the ME estimate on all forages measured
ME2 (MJ/kg)
ME3 (MJ/kg)
ME4 (MJ/kg)
will be more precise with NFE inclusion in their
equation.
Comparison of the ME4 of the NRC estimate to the
other in vivo result without inclusion of corn silage
Table 5
The correlation coef®cients of metabolizable energy estimatesa
Item
DE
DE
TDN
ME1
ME2
ME3
ME4
ME5
ME6
ME7
ME8
a
0.9981
0.0001
0.9997
0.0001
0.7747
0.0051
0.7602
0.0001
0.8745
0.002
0.6562
0.0001
0.6591
0.0001
0.6585
0.0001
0.8519
0.0001
TDN
ME1
ME2
ME3
ME4
ME5
ME6
ME7
ME8
0.9980
0.0001
0.9980
0.0001
0.9998
0.0001
0.9024
0.0001
0.9416
0.0001
0.9521
0.0001
0.8874
0.0002
0.9126
0.0007
0.9272
0.0001
0.8297
0.0016
0.7825
0.0044
0.7600
0.0066
0.9673
0.0001
0.9024
0.0001
0.8774
0.0001
0.8198
0.0001
0.8231
0.0001
0.8302
0.0001
0.9806
0.0001
0.9554
0.0001
0.9995
0.0001
0.8177
0.0001
0.8252
0.0001
0.8352
0.0001
0.9845
0.0001
0.9627
0.0001
1.000
0.0001
0.9999
0.0001
0.8174
0.0001
0.8290
0.0001
0.8368
0.0001
0.9856
0.0001
0.9644
0.0001
0.9999
0.0001
0.9993
0.0001
0.9999
0.0001
0.8837
0.0001
0.9287
0.0001
0.9283
0.0001
0.8242
0.0001
0.7953
0.0001
0.7877
0.0001
0.7849
0.0001
0.7877
0.0001
0.7890
0.0001
0.9981
0.0001
0.8608
0.001
0.8753
0.0002
0.9410
0.0001
0.7697
0.0001
0.7805
0.0001
0.7817
0.0001
0.8411
0.0001
0.8790
0.0001
0.8872
0.0001
0.9444
0.0001
0.7720
0.0001
0.7832
0.0001
0.7843
0.0001
0.8385
0.0001
0.9652
0.0001
0.8790
0.0001
0.8841
0.0001
0.8773
0.0001
0.8820
0.0001
0.5059
0.0001
0.8872
0.0001
0.9481
0.0001
0.9452
0.0001
0.9485
0.0001
0.5820
0.0001
0.9996
0.0001
1.0000
0.0001
0.9999
0.0001
0.6083
0.0001
0.9995
0.0001
0.9993
0.0001
0.7849
0.0001
0.9999
0.0001
0.6083
0.0001
0.6083
0.0001
The correlation coef®cient values in the lower and left side of diagonal of the table were calculated on the ME value which derived from
forages without inclusion of corn silage and alfalfa hay (n 10). The right and upper side of the table content values derived from ME values
of the 12 feeds (n 12).
258
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
and alfalfa (n 10), the correlation between ME1 and
ME4 was the highest (r 0.9673, P < 0.0001). The
correlation coef®cient for ME1 and ME2 (r 0.9521,
P < 0.0001) was higher than the correlation for ME1
and ME3 (r 0.9272, P < 0.0001) from the remaining
10 forages. The correlation of ME2 and ME4
(r 0.9024, P < 0.0001) was also higher than the
correlation of ME3 and ME4 (r 0.8774,
P < 0.0001). This indicated that ME2 and ME3 were
appropriate for estimating the ME of forage. ME2
was more practical for estimating the ME of forage
than ME3. This represents that inclusion of NFE
in addition to EE, CP and gas production in the
predicted equation did not improve the precision
of the ME estimates. For forage, both CF and NFE
procedures are known to be inadequate for accurate
determinations. The CF method tends to underestimate true ®ber content, especially in immature forage
with high hemicellulose content. Data presented in
Table 2 clearly demonstrates this concept as CF values
which are suppose to represent total ®ber are consistently lower than ADF which represents only the
cellulose content of the forage. Therefore, CF should
be replaced by ADF in the predicting equation to
improve the precision. The ME estimated on tropical
forage will be more precise without NFE inclusion
in the equation.
The NFE procedure also tends to overestimate
values for forage. The values presented in Table 2
are considerably high. The actual values for starch
would be much less. Take Bermuda grass for example,
Sniffer et al. (1992) indicated 79.5% carbohydrate
(CHO) with 66.6% ®brous and 12.9% non-®brous
CHO with only 0.8% starch and 53.1% slow degradable CHO. From our laboratory showed that Napier
grass with 56.0% ®brous CHO and 29.4% non-®brous
CHO with only 1.7% starch and 46.5% slow degradable CHO (unpublished data). Since high correlation
achieved in this trial, it appears that underestimation of
total ®ber was compensated for by an overestimation
of soluble carbohydrates.
The estimates for forage ME, which were derived
from in vitro methods using gas production, CP and
EE to calculate ME value (ME2) was initiated by
Menke et al. (1979) and were modi®ed by Menke
and Steingass (1988). This revised equation is
ME6 1.56 0.1390Gb 0.007400CP 0.01780EE. The correlation of ME6 and ME1 estimated from
the goat digestion trial in this study (r 0.7832) was
lower where the correlation of ME6 and ME2
(r 0.8773) was lower than that of the correlation
of ME6 and ME3 (r 0.9452). When comparing the
ME estimates of gas production, CP and EE from this
study to other data, the correlation coef®cients were
also very high. The ME1 and ME5 (r 0.7720), which
were estimated from the goat digestion trial (Steingass
and Menke, 1980) and ME7 (Rohr et al., 1986) and
ME8 (SchoÈner, 1981) which was calculated using
regression were high. These values however were still
lower than correlation coef®cient determined from
ME1 and ME2.
The amount of gas produced from this trial showed
a trend toward decreasing as the period of forage
growth advanced. The average gas production was
around 40±58 ml/200 mg (Table 2) and agreed with
the value of Zinash et al. (1996). They also found a
decrease in gas production as the forage growing
period was prolonged.
It appears that the ME of forage estimated from this
trial is easy to measure and provides a reasonable
estimate and can be used to replace the digestion trial.
This however, can not provide precise estimates for
lactating dairy goat because this study utilized dried
dairy goats at a maintenance level to generate the in
vivo data. Lactation stage has a great impact on
nutrient intake and subsequently, nutrient digestibility
and utilization.
4. Conclusion
The correlation coef®cient of metabolizable energy
estimated from the gross energy digestibility, total
digestible nutrients determined by the dairy goat
digestion trial and metabolizable energy estimated
from the digestible nutrients and gas production using
the Menke and Steingass (1988) in vitro method was
high. The in vitro ME estimate for forage can be
applied in Taiwan, because it not only is rapid, convenient and cost saving, but is also suitable for application to dairy goats and cattle. It can be adapted to
evaluate various sources of forage with different
compositions and provide data for the most important
nutrients and energy sources, for proper ration formulation in dairy farming.
M.-J. Lee et al. / Small Ruminant Research 36 (2000) 251±259
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