Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol86.Issue3-4.Aug2000:

Animal Feed Science and Technology
86 (2000) 165±176

Using the DVE/OEB model to determine optimal
conditions of pressure toasting on horse beans
(Vicia faba) for the dairy feed industry
P. Yu*, J.O. Goelema, S. Tamminga
Department of Animal Nutrition, Wageningen Agricultural University, Zodiac,
Marijkeweg 40, 6709 PG Wageningen, The Netherlands
Received 18 January 2000; received in revised form 27 April 2000; accepted 22 June 2000

Abstract
The effects of pressure toasting (100, 118 and 1368C for 3, 7, 15 and 30 min) of horse beans on
potential ruminant protein nutritional values were evaluated by the new Dutch protein evaluation
system: the DVE/OEB model. The items assessed in this experiment were: (a) rumen bypass protein
(BCP); (b) rumen bypass starch (BSt); (c) fermented organic matter (FOM); (d) truly absorbed
bypass protein (ABCP); (e) microbial protein synthesized in the rumen based on available energy
(E_MP); (f) microbial protein synthesized in the rumen based on available N (N_MP); (g) true
protein supplied to the small intestine (TPSI); (h) truly absorbed rumen synthesized microbial
protein (AMP); (i) endogenous protein losses (ENDP); (j) truly digested protein in the small
intestine (DVE) and (k), degraded protein balance (OEB). Pressure toasting signi®cantly increased

BCP, BSt, TPSI, ABCP, DVE (P < 0:001) and decreased FOM, E_MP, AMP, N_MP and OEB
(P < 0:001) with increasing temperatures and times. The values of BCP, BSt, TPSI, ABCP and
DVE at 1368C/15 min were increased by 213.0, 83.0, 66.1, 246.1 and 90.1% and the values of
FOM, E_MP, AMP, N_MP and OEB at 1368C/15 min were decreased by 28.7, 30.9, 29.0, 49.0 and
69%, respectively, over the raw horse beans. The results indicated that although pressure toasting
reduced microbial protein synthesis due to reducing FOM, TPSI didn't decrease but increased
substantially because BCP more than enough to compensate for the decrease in microbial protein.
Therefore the net absorbable DVE in the small intestine was highly increased. The OEB values
were signi®cantly reduced (P < 0:001) but were not negative. Results indicated that microbial
protein synthesis might not be impaired due to the suf®cient N supplied in the rumen, but the high
positive OEB values in the most treatments except 1368C/15 min (The OEB values: 31.9 g/kg DM)

*

Corresponding author. Present address: Department of Animal and Poultry Science, University of
Sasakatchewan, 51 Campus Drive, Saskatoon, SK, Canada S7N 5A8. Tel.: ‡1-306-966-4132;
fax: ‡1-306-966-4151.
E-mail address: yupe@sask.usask.ca (P. Yu).
0377-8401/00/$ ± see front matter # 2000 Published by Elsevier Science B.V.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 7 1 - 1

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P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

indicated that there were large losses of N in the rumen. It was concluded that pressure toasting at
high temperature was effective in shifting protein degradation from rumen to the intestines and in
increasing the DVE values without reaching negative OEB values. The treatments of 1008C for 7,
15 or 30 min, 1188C for 3, 7, 15 or 30 min and 1368C for 3 or 7 min were not suf®cient to reduce Nloss in the rumen due to the too high OEB values. But pressure toasting at 1368C/15 min might be
optimal treatments for horse beans due to the very lower OEB values. Additional study is required
concerning the effects of optimal pressure toasting of horse beans on animal performance.
# 2000 Published by Elsevier Science B.V.
Keywords: Horse bean; Protein evaluation; DVE/OEB model; Optimal pressure toasting; Cows

Nomenclature
ABCP
AMP
BCP
%BCP
BSt

%BSt
Cfat
D
DOM
DVE
dASH
dBCP
ENDP
E_MP
FOM
Kd
Kp
N_MP
OEB
S
T0
TPSI
U
UASH
UDM

UOM

truly absorbed bypass protein in the small intestine (g/kg DM)
truly absorbed rumen synthesized microbial protein in the small intestine
(g/kg DM)
bypassing rumen microbial degradation of feed protein (g/kg DM)
fraction of bypassing rumen degradation of feed protein
bypassing rumen microbial fermentation of feed starch (g/kg DM)
fraction of bypassing rumen degradation of feed starch
crude fat (g/kg DM)
insoluble but potential degradation fraction in the in sacco incubations (%)
digested organic matter (g/kg DM)
truly digested protein in the small intestine (g/kg DM)
digestibility of inorganic matter (%)
digestibility of bypass protein in the small intestine (%)
endogenous protein in the small intestine (g/kg DM)
microbial protein synthesized in the rumen based on available energy
(g/kg DM)
organic matter fermented in the rumen (g/kg DM)
the rate of degradation of D fraction (%/h)

passage rate (%/h)
microbial protein synthesized in the rumen based on available nitrogen
(g/kg DM)
degraded protein balance (g/kg DM)
soluble fraction in the in sacco incubation (%)
lag time in which no degradation takes place (h)
true protein supplied to the small intestine (g/kg DM)
undegradable fraction in the in sacco incubation (%)
undigested inorganic matter (g/kg DM)
undigested dry matter (g/kg DM)
undigested organic matter (g/kg DM)

P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

167

1. Introduction
Horse beans (Vicia faba), also called faba beans (Petterson and MacKintosh, 1994),
have high protein (25±30%) and starch contents (30±40%) (Tamminga et al., 1990;
Petterson and MacKintosh, 1994), are well suited agronomically to the ecological and

climatic conditions of many countries (Cros et al., 1992; Benchaar et al., 1994) and
appear to be potentially useful protein supplements in ruminal diets.
However their rapid and extensive degradation by rumen microbes, resulting in
imbalance between feed breakdown and microbial protein synthesis and causing
unnecessary N-loss from rumen, make them unsuitable and/or inef®cient to be used in the
unprocessed form in ruminal diets. Studies have shown that protein degradability of horse
bean was 85±90% (Van Straalen and Tamminga, 1990; Aguilera et al., 1992; Cros et al.,
1992). Thus there were little protein remaining to bypass the rumen to the small intestine.
But protein becomes available to the animal only after digestion in and absorption from
the small intestine (Hvelpund et al., 1992).
Not only is protein degradability high in horse beans but also the starch degradability.
The study indicated that ruminal starch degradability of horse beans was 76±78%
(Tamminga et al., 1990). In high producing dairy cows, glucose can also be a limiting
nutrient (Nocek and Tamminga, 1991; Van Bruchem, 1991). If the non-structural
dietary carbohydrates (starch) are quantitatively degraded in the rumen, the animal has
to rely for its glucose supply mainly on glucogenic precursors such as propionic acid
and glucogenic AA. Under such conditions, productivity increases if a part of the dietary
non-structural dietary carbohydrates bypasses the reticulo-rumen. It is advantageous
under such conditions to have more starch escape degradation in the rumen and provide
a source of glucose in the small intestine (Nocek and Tamminga, 1991) to achieve a

higher milk production. Such an advantage may also be true in growing meat animals
(Tudor, 1990).
If horse beans are to be used more ef®ciently in high yielding dairy cows or young
growing ruminants, the extent of protein and starch degradation in the rumen must be
reduced without altering their intestinal digestibilities.
Pressure toasting (Yu, 1995) reduced the rumen protein degradation and increased
BCP. But the optimal processing conditions have not yet been found.
To fully and accurately evaluate the above nutritive values in quantitative of raw
and pressure toasted horse beans in dairy cows, a proven evaluation method must be
used. The in sacco and mobile bag techniques which are internationally accepted
methods (Tamminga and Jansman, 1993), together with the newly developed Dutch
protein evaluation system: the DVE/OEB model (Tamminga et al., 1994) were
employed.
The objectives of this study were to evaluate the effects of pressure toasting on rumen
degradation and intestinal digestion characteristics of raw and toasted horse beans at
various conditions by the nylon bag methods, to give the quantitative aspects of how the
pressure toasting affected the protein and starch degradation and digestion in detail and to
give information for ration formula and the decision for the optimal treatment conditions
in dairy industry.

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P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

2. Materials and methods
2.1. Feedstuffs
Horse beans were obtained from the Dutch commercial company. The chemical
compositions of raw horse beans are present in Table 1.
2.2. Pressure toasting
Horse beans were pressure toasted at three different temperatures (100, 118 and 1368C)
for 3, 7, 15 and 30 min in an incomplete block design. All treatments were carried out in
duplicate resulting in 22 treatments in total divided into A and B series as shown in the
Table 1. The treatments of 1008C/3 min and 1368C/30 min were dropped due to no
expected signi®cant difference between the raw and 1008C/3 min and the risk of
overheating, respectively.
Processing was carried out at Wageningen Feed Processing Center (WFPC) using a
laboratory scale pressure toaster as described by Van der Poel (1990). After toasting,
horse beans were dried at 358C/18 h in the oven, allowed to cool down to ambient
temperature and then coarsely ground through a 3 mm screen (Hammer Mill AEG TYP
AM80N2).

2.3. Animals and diets
Four lactating Holstein±Friesian cows ®tted with a large rumen cannula with an
internal diameter of 10 cm for measuring rumen degradability were housed at the tie stall
at the experimental station in Wageningen Agricultural University. All cows received
daily about 16 kg of DM of a diet consisting of a commercial pelted concentrate (6.5 MJ

Table 1
The conditions of pressure toasting treatments of A and B series of horse beans
Treatments

1108C/7 min
1108C/15 min
1108C/30 min
1188C/3 min
1188C/7 min
1188C/15 min
1188C/30 min
1368C/3 min
1368C/7 min
1368C/15 min

a

Standard deviation.

Series A

Series B

Temperature
(8C) (S.D.)a

Pressure
(bar)

Temperature
(8C) (S.D.)a

Pressure
(bar)

100:9  0:6
100:0  0:1
100:8  0:4
118:0  0:4
118:2  0:2
117:8  0:4
118:3  0:2
136:0  0:2
136:2  0:2
136:0  0:2

0.10
0.10
0.10
0.90
0.90
0.89
0.90
2.21
2.24
2.24

101:1  0:4
100:2  0:6
101:0  0:8
118:4  0:1
118:5  0:3
118:6  0:2
118:5  0:3
136:4  0:2
136:4  0:2
136:4  0:3

0.11
0.10
0.10
0.90
0.90
0.90
0.90
2.25
2.30
2.30

P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

169

NEL and 120 g DVE/kg) and hay (55% of total DM intake, 853 g DM/kg, 5.4 MJ NEL
and 62 g DVE/kg) according to Dutch lactating dairy cow feed requirements.
Four lactating Dutch dairy cows, ®tted with a T-piece cannula in the proximal
duodenum, housed on a tie-stall and fed pelted commercial concentrate and hay to Dutch
feeding standards (CVB, 1996), were used to determine intestinal digestion by the mobile
bag technique at the research institute of IVVO (The Netherlands).
All the cows were individually fed twice daily at 08:00 h and 16:00 h. Water was
always available. A 14 days period of adaptation was allowed.
The animal used in these experiments were cared for in accordance with the guidelines
Dutch Animal Care and Use.
2.4. Rumen incubation
Ruminal degradation characteristics of horse beans in the rumen of 4 lactating dairy
cows were determined using the in sacco method. Incubation of all treatments in the
rumen were with 5.5 g DM in coded nylon bags (10 cm  17 cm) with the pore size of
approximately 40 mm (Nylot, Switzerland). The rumen incubations were performed
according to the `gradual addition/all out' schedule. Incubations were carried out for 24,
12, 8, 4 and 2 h, bags were inserted at 17:00, (next day) 05:00, 09:00, 13:00, 15:00 and all
were removed at 17:00 h. The 48 h rumen incubations were carried out from 20:00 until
20:00 h 2 days later. All treatments were randomly allocated over all cows and the whole
incubation period.
After incubation, the bags were removed from rumen and rinsed under a cold stream of
tap water to remove excess ruminal contents and microbes on the surface to stop
microbial activity. The bags were washed with cool water without detergent in a
commercial washing machine for 55 min without spinning and subsequently dried at
608C for 24 h. The 0 h incubation samples were only put in the washing machine under
the same conditions. Dry samples were stored in a cool room (48C) until analysis. The
residues were pooled according to feed treatment and incubation time and then ground
through a 1 mm screen and analyzed for DM, ash, St and N.
2.5. Intestinal digestion
The four intestinal cannulated lactating Dutch dairy cows were used to determine
intestinal digestion by the mobile bag technique. Extra bags were incubated in the rumen
to provide suf®cient material for the intestinal studies. The feed was preincubated for
12 h. After rumen incubation, the bags were removed and handled as described
previously. However, the residues were freeze dried and pooled according to feed
treatments. Approximately 0.5 g (DM) of rumen residues was then weighed into small
coded nylon bags (5 cm  3 cm, pore size 40 mm), 24 bags per treatment. Prior to
incubation in the small intestine the bags were incubated in a solution of pepsin±HCl
solution (1 g pepsin 2000 FIP u/g, Merck 7190 in 1 l 0.1 N HCl) at 398C for 1 h. Every
20 min, four mobile bags were taken at random and inserted into the intestine through the
duodenal cannula. The bags were retrieved from faeces. Checks were made every 2 h
after bag introduction, and the collection time was recorded for each bag. The retrieved

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P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

bags were stored at ÿ208C until all the bags had been recovered. These bags were thawed
and washed in a washing machine for 2 h at 408C without spinning. The residues were
freeze dried, weighed and pooled according to feed treatments and analyzed for N, DM
and ash after pooled residues were ground using a 1 mm mesh.
2.6. Chemical analysis
Laboratory samples of the feeds, rumen residues and mobile bags residues of all
treatments of horse beans were prepared by grinding to pass a 1 mm mesh. DM was
determined by drying at 1058C to constant weight (AOAC, 1984). Ash was determined by
ashing at 5508C to constant weight (AOAC, 1984). St was determined according to the
NIKO method (Brunt, 1992). N was analyzed by Kjeldahl digestion and distillation
(Gerhardt Vadopest 6, Germany) and CP content was obtained as N  6:25 (Boer, 1995).
2.7. The DVE/OEB model
2.7.1. Rumen protein and starch degradation characteristics
Rumen degradation characteristic, BCP and BSt in the rumen were determined by the
in sacco method (Tamminga and Jansman, 1993). In this technique, the results were
calculated using the NLIN (non linear) procedure of the statistical package SAS (SAS,
1991) using iterative least squares regression (Gauess±Newton method) by the following
the ®rst order kinetics equation: R…t† ˆ U ‡ D expÿKd…tÿT0† (érskov and McDonald,
1979; Tamminga et al., 1994) (1), where, R(t) stands for residue (in %) of the amount of
incubated material after t h of rumen incubation; U and D in %; T0 in h; Kd in %/h.
BCP were calculated as: %BCP ˆ U ‡ D  Kp/(Kp ‡ Kd); (2). BCP ˆ 1:11  CP
%BCP=100, (3), where, Kp of 6%/h was adopted based on international data (Tamminga
et al., 1994); BCP and CP in g/kg DM; The factor 1.11 in the formula was taken from the
French PDI-system (INRA, 1978), the regression coef®cient of in vivo on in sacco
degradation data.
BSt were calculated as: %BSt ˆ D  Kp=…Kp ‡ Kd† ‡ 0:1  S, (4); BSt ˆ St
…g=kg†  %BSt=100, (5), where: Kp of 6%/h was adopted based on international data
(Tamminga et al., 1994); BSt and St in g/kg, DM For the factor 0.1 in the formula (4), it
was assumed that for starch 10% of S escape rumen fermentation (Tamminga et al.,
1994).
2.8. Microbial protein synthesis in the rumen
FOM in the rumen was calculated as: FOM ˆ DOM ÿ CFat ÿ BCP ÿ BSt ÿ FP, (6),
where, DOM, CFat, BCP, BSt in g/kg DM; FP is the fermentation products for conserved
forages (g/kg DM) not for legume seeds.
Subsequently E_MP was estimated as: E_MP ˆ 0:15  FOM, (7), where, E_MP in g/
kg DM, the factor 0.15 means that per kg FOM, 150 g of microbial protein CP is assumed
to be synthesized. TPSI was calculated as: TPSI ˆ BCP ‡ 0:75  MP, (8), where, factor
0.75 means that 75% of microbial N is present in AA, the remaining part of N in nucleic
acids.

P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

171

2.9. Intestinal digestion of feed and microbial protein
The previously discussed BCP and TPSI did not give exact enough information on the
amount of AA absorbable from the small intestine. A correction is needed for protein
losses due to incomplete digestion and resulting from endogenous excretion. True digestibility of microbial protein is assumed to be 85% (Egan et al., 1985) and, therefore, the
amount of AMP can be estimated as: AMP ˆ 0:85  0:75  0:15  FOM, (9), where, AMP
in g/kg DM. For feed ingredients, ABCP is calculated as: ABCP ˆ …dBCP=100† BCP, (10).
In DVE/OEB model, ENDP in the intestine is related to the amount of DM excreted in
the feaces. According to DVE/OEB, 75 g of absorbed protein per kg DM in feacal
excretion is required to compensate for endogenous losses. Therefore ENDP is estimated
as: ENDP ˆ 75  UDM, (11), where, UDM and ENDP in g/kg DM; UDM ˆ UOM‡
UASH (12), where, UOM ˆ OM ÿ DOM; UASH ˆ ASH-ASH  dASH, dASH for both
horse beans are 50% (CVB, 1996).
The DVE value was estimated as: DVE ˆ ABCP ‡ AMP-ENDP, (13), where, DVE in
g/kg DM.
2.10. The degraded protein balance
The OEB value is balance between microbial protein synthesis from rumen degradable
CP and that from the energy extracted during anaerobic fermentation in the rumen. Therefore, the OEB value was estimated as: OEB ˆ N_MP-E_MP, (14), where, N_MP ˆ CP
ÿBCP ˆ CP-1:11  %BCP/100; E_MP ˆ 0:15  FOM; all parameters in g/kg DM. When
OEB is positive, it indicates the loss of N from the rumen. When negative, microbial
protein synthesis may be impaired, because of a shortage of N in the rumen. The optimum
OEB value in a ration is, therefore, zero or slightly above (Tamminga and Jansman, 1993).
2.11. Statistical analysis
Statistical analyses were carried out using the SAS (1991). Analysis of variance was by
using Proc GLM of SAS. Comparison of means were carried out by using the Student±
Newman±Keuls test (Steel and Torrie, 1980) when the effect of treatment was signi®cant
(P < 0:05).

3. Results
3.1. Chemical compositions
The chemical composition of raw and pressure toasted horse beans are given in Table 2.
Raw horse beans contained DM of 887.1 g/kg, ash of 35.8 g/kg DM, St of 322.6 g/kg DM
and N of 39.3 g/kg DM. Pressure toasting had signi®cantly affected DM content
(P < 0:01). This could be attributed to the water evaporating (Kibelolaud et al., 1993).
Pressure toasting did not signi®cantly change the OM, St and N contents on DM basis
(P > 0:05).

Raw

SEMb

Temperature (8C)
100
7 min

118
15 min

30 min

a
b

3 min

7 min

902.65 ab 903.05 ab 902.45 ab 906.45 a
35.85
36.00
35.85
36.00
335.43
334.90
345.87
336.38
40.08
40.49
40.52
40.42

Rumen degradation characteristics of crude protein (CP)
S (%)
64.20 a
61.41 b
58.23 c
D (%)
34.03 d
35.73 d
37.37 d
U %)
1.78
2.87
4.40
Kd (%/h)
7.37 ab
8.79 a
8.68 a
%BCP
17.31 g
17.52 g
20.03 fg
BCP (g/kg DM)
47.22 f
48.65 f
56.26 f
Rumen degradation characteristics
S_st (%)
58.22 a
D_st (%)
41.78 g
Kd_st (%/h)
4.86
%BSt
29.01 f
BSt (g/kg DM)
93.50 e
FOM (g/kg, DM)
651.01 a
E_MP (g/kg, DM)
97.65 a
TPSI (g/kg, DM)
120.46 g
AMP (g/kg, DM)
62.26 a
ENDP (g/kg, DM)
13.01
ABCP (g/kg, DM)
40.14 f
N_MP (g/kg, DM) 198.56 a
DVE (g/kg, DM)
89.39 g
OEB (g/kg, DM)
100.91 ab

136

of starch (St)
53.62 a
50.57
46.37 g
49.43
4.51
5.18
31.85 ef
31.58
106.84 d 105.80
631.48 ab 613.40
94.73 ab 92.01
119.69 g 125.27
60.39 ab 58.16
13.36
14.22
42.71 f
49.23
201.83 a 196.78
89.74 g
93.67
107.10 a 104.77

ab
fg

54.36
44.36
1.29
6.12
23.26
65.36

d
c
abc
ef
e

50.68 ab
49.33 fg
4.66
ef
32.87ef
d 113.59 d
ab 592.10 b
ab 88.82 b
fg 131.98 ef
b
26.62 b
14.56
f
58.57 e
a 187.86 ab
fg 100.63 ef
ab 99.05 ab

51.82
43.05
5.14
6.20
26.33
73.85
44.07
55.94
4.84
35.40
119.06
597.16
89.58
141.04
57.10
13.12
65.73
178.77
109.72
89.20

e
c
abc
e
e
bc
ef

15 min

30 min

3 min

7 min

15 min

902.35 ab 901.30 ab 900.45 ab 904.00 ab 899.45 b
36.05
36.20
36.15
36.35
36.15
333.78
338.89
333.09
332.80
339.18
40.41
39.98
40.01
39.83
39.77
48.57
47.25
4.18
7.42
25.39
71.19

39.37
60.64
4.73
ed 37.83
cd 126.28
b 592.27
b
88.84
e 137.82
b
56.64
13.14
e
64.35
b 181.35
e 107.85
b
92.51

f
c
ab
e
e
cd
de

41.21
58.80
0.00
4.38
34.01
94.26

19.60
61.88
3.60
d
42.51
c 144.01
b 464.70
b
81.07
e 155.05
b
51.68
13.97
e
86.06
b 155.60
e 123.77
ab 74.53

g
b
abc
d
d
cd
de
c
b
c
c
d
c
d
c
d
c

38.11
61.44
0.46
4.49
35.66
98.96
32.39
67.61
3.87
44.37
147.69
530.53
79.58
158.64
50.74
14.08
90.45
151.11
127.10
71.53

h
b

893.15 c
36.20
326.64
39.91

34.23 i
30.98
63.22 b
69.03
2.56
0.00
abc
3.97 abc
2.88
d
40.62 c
46.67
d 112.5 4c 128.76

31.27
68.73
0.00
bc
1.73
b
53.39
b 147.79

c
a
a

de
cd

fg
ab

g
a

30.12
69.89
4.08
c
44.60
b 148.38
cd 516.73
cd 77.51
d 170.36
cd 49.42
14.06
d 103.70
c 136.68
d 139.05
c
59.18

ef
bc
c
b
cd
cd
c
cd
c
dv
c
d

For the abbreviations see Nomenclature; means with the same letter in the same row are not signi®cantly different (P > 0:05).
Standard error of mean.

24.66
75.34
3.87
48.28
163.74
493.10
73.97
184.24
47.15
13.45
120.27
119.80
153.97
45.84

j
a

19.60
80.41
3.44
b
53.09
a 173.46
de 464.70
de 69.71
b 200.07
de 44.44
13.42
b 138.93
e 101.62
b 169.94
e
31.92

j
a

a
a
e
e
a
e
a
f
a
f

1.26
0.10
5.65
0.38
0.59
1.22
1.22
0.91
1.09
2.85
1.97
1.97
0.34
1.01
3.19
9.85
1.48
2.50
0.95
0.57
2.56
3.93
2.49
3.66

P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

Chemical compositions
DM (g/kg)
887.10 d
Ash (g/kg, DM)
35.80
St (g/kg, DM)
322.60
N (g/kg, DM)
39.32

172

Table 2
Effect of pressure toasting on nutritional values (e.g. DVE and OEB) of horse beans in lactating dairy cows, calculated according to the new Dutch DVE/OEB modela

P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

173

3.2. Quantitative evaluation of raw and pressure toasting horse beans
The effects of pressure toasting on protein degradation and digestion and microbial
protein synthesis and digestion of horse bean in dairy cows are presented in Table 2.
Pressure toasting had no signi®cant effects on U (CP), T0, dBCP DOM, UOM, UASH,
UDM and ENDP (P > 0:05), but had signi®cant effects on S, D, %BCP, %BSt, BCP, BSt,
FOM, E_MP, TPSI, AMP, ABCP, DVE, N_MP, OEB (P < 0:01) and Kd (P < 0:05).
Pressure toasting signi®cantly reduced S, increased D, reduced Kd without affecting U,
resulting in decreasing rumen degradability of CP and St thus increasing BCP 3.1 times
(from 47.2 in the raw to 147.8 g/kg DM in 1368C/15 min) and BSt 1.9 times (from 93.5 in
the raw to 173.5 g/kg DM in 1368C/15 min), compared with the raw, respectively.
FOM was reduced gradually and varied from 651.0 in the raw to 464.7 g/kg in 1368C/
15 min due to increasing BCP and BSt, resulting in decreasing E_MP. Though E_MP
decreased, TPSI was increased from 120.5 in the raw to 200.1 g/kg DM in the 1368C/
15 min. Based on the assumption of true digestibility of microbial protein as 85%, AMP
reduced from 62.3 in the raw to 44.4 g/kg DM in 1368C/15 min.
For ENDP, pressure toasting did not signi®cantly change its content, averaging 13.7 g/kg
DM.
Pressure toasting did not signi®cantly affect digestibility of BCP, averaging 90.2%. ABCP
in the small intestine was increased signi®cantly from 40.1 in the raw to 138.9 g/kg DM
in 1368C/15 min.
The DVE value was increased with increasing temperatures and times as shown in
Fig. 1. Compared with the raw, it was increased 1.9 times from 89.4 in the raw to 169.4 in
1368C/15 min.

Fig. 1. Effect of pressure toasting on the DVE value of horse beans in dairy cows (DVE ˆ truly digested protein
in the small intestine).

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P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

Fig. 2. Effect of pressure toasting on the OEB value of horse beans in dairy cows (OEB ˆ degraded protein
balance).

3.3. Degraded protein balance
As to the OEB value, it was reduced with increasing temperatures and times as shown
in Fig. 2. Compared with the raw (100.9 g/kg DM), it reduced 3.2 times in 1368C/15 min
but not to the level of negative.

4. Discussion
Input data from in sacco, mobile bag techniques were from dairy cows. Consequently
the data generated by the model, though of signi®cance in the dairy cows, are best
regarded as characteristics of the test material.
Protein evaluation results by the DVE/OEB model indicated that though pressure
toasting reduced microbial protein synthesis due to a reduction in FOM and a reduction in
rumen protein degradation, the DVE value did not decrease but increased markedly. This
was due to the fact that BCP was increased more than enough to compensate for the computed decrease in microbial protein production. Therefore, the net absorbable DVE value
in the animal was substantially increased. The largest increase was found in 1368C/15 min.
The OEB value shows the (im)balance between microbial protein synthesis from
available rumen degradable CP and potential energy from anaerobic fermentation in the
rumen. When the OEB value is positive, it indicates the N-loss from the rumen. When
negative, microbial protein synthesis is predicted to be impaired because of a shortage of
N in the rumen. The optimum OEB value in a ration is therefore zero or slightly above

P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

175

(Tamminga et al., 1994). The margin for safety is to allow for asynchrony Ð a factor
important in feeding supplements to grazing animal or feeding an ingredient separately of
the main basal feed.
Present study showed that raw horse beans had a high OEB value, which indicated an
imbalance between feed N degradation and utilization and indicated a potentially large
N-loss from rumen. Pressure toasting signi®cantly reduced the OEB values but did not
cause them to become negative. Pressure toasting at 1368C/15 min might cover the
optimal treatment range for horse bean in terms of treating to achieve target values for
potential net absorbable protein in the small intestine while holding any N-loss in the
rumen to a low level.
When combining with a roughage or another supplement, the OEB value, if positive,
will be reduced only by the presence of rapidly fermentable low N substrate. Roughage
with a negative OEB would bene®t from addition of higher OEB supplements. If OEB is
negative, the overall effect of a high ABCP may not be bene®cial until other material
raises OEB to zero or slightly above zero. The fermentable OM such as degradable starch
may improve microbial protein in such a case.
All the results reported here are output from a model with inputs based on in sacco,
mobile bag techniques measurements. The challenge is to apply the predictions and
evaluate them in an animal performance experiment. However, the number of such
studies in this area available to challenge the model is limited. Part of reason is that the
information on DVE and OEB values of each feedstuffs, or data from which these are
derived is limited.

5. Conclusion
It was concluded that pressure toasting was effective in shifting protein degradation
from rumen to intestine and increased the DVE value with increasing temperatures and
times but did not cause the OEB value to become negative.
However, pressure toasting of horse beans at 1008C (7, 15 and 30 min), 1188C (3, 7, 15
and 30 min) and 1368C (3 and 7 min) did not fully prevent unnecessary N-loss from
rumen due to their high OEB values, though it reduced rumen degradation of protein and
increasing true absorbed protein in the small intestine. Pressure toasting at 1368C/15 min
might be an upper to the optimal treatment range due to its high DVE without producing
negative OEB value affecting microbial protein production.
Further studies are required concerning the effects of optimal pressure toasting of horse
beans on animal performance.

Acknowledgements
The authors wish to thank the staff in Department of Animal Nutrition, Wageningen
Agricultural University, The Netherlands, for helpful assistance in the chemical analysis
and the staff of Research Institute for Livestock Feeding and Nutrition, The Netherlands,
for taking care of the intestinally cannulated dairy cows.

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P. Yu et al. / Animal Feed Science and Technology 86 (2000) 165±176

References
Aguilera, J.F., Bustos, M., Molina, E., 1992. The degradation of legume seed meals in the rumen: effect of heat
treatment. Anim. Feed Sci. Technol. 36, 101±112.
AOAC, Association of Of®cial Analytical Chemists, 1984. Of®cial Methods of Analysis. Washington, DC.
Benchaar, C., Vernay, M., Bayourthe, C., Moncoulon, R., 1994. Effects of extrusion of whole horse beans on
protein digestion and amino acid absorption in dairy cows. J. Dairy Sci. 77, 1360±1371.
Boer, H., 1995. Laboratory Analyses Procedures of Animal Nutrition, Lecture Note. Department of Animal
Nutrition, Wageningen Agricultural University, The Netherlands.
Brunt, K., 1992. Enzymatische bepaling van het gahalte aan zetmeel in veevoeder en veevoedergrondstoffen
(concept). Netherlands Instituut Voor Koolhydraten Onderzoek (NIKO), memo, pp. 92±115.
Cros, P., Vernay, M., Bayourthe, C., Moncoulon, R., 1992. In¯uences of extrusion on ruminal and intestinal
disappearance of amino acid in whole horse beans. Can. J. Anim. Sci. 72, 359±366.
CVB, Centraal Veevoeder Bureau, 1996. Voorlopig protocol voor in sacco pensincubatie voor het meten van
eiwitbestendigheid, 14 November.
Egan, A.R., Koda, K., Barady, K., 1985. Regulation of N metabolism and recycling. Control of Digestion and
Metabolism in Ruminants. In: Proceedings of the Sixth International Symposium on Ruminant Physiology.
Butterworths, London, pp. 146±153.
Hvelpund, T., Weisbjerg, M.R., Andersen, L.S., 1992. Estimation of the true digestibility of rumen undegraded
dietary protein in the small intestine of ruminants by the mobile bag technique. Acta Agric. Scand., Sect. A,
Anim. Sci. 42, 34±39.
INRA, 1978. Alimentation des ruminants. Inst. National de al Rech. Agron. Versailles, p. 597.
Kibelolaud, A.R., Vernay, M., Bayourthe, C., Moncoulon, R., 1993. Effect of extruding on ruminal
disappearance and lower gastrointestinal tract digestion of white lupiri seeds. Can. J. Anim. Sci. 73, 571±
579.
Nocek, J.E., Tamminga, S., 1991. Site of digestion of starch in the gastrointestinal tract of dairy cows and its
effect on milk yield and composition. J. Dairy Sci. 74, 3598±3629.
érskov, E.R., McDonald, I., 1979. The estimation of protein degradability in the rumen from incubation
measurements weighted according to the rate of passage. J. Agric. Sci. (Cambridge) 92, 499±503.
Petterson, D.S., MacKintosh, J.B., 1994. The chemical composition and nutritive value of Australia grain
legumes. Grain research and development corporation, Canberra, pp. 13±16.
SAS, 1991. User's Guide: Statistics, Version 6, SAS Inst., Inc., Cary, NC.
Steel, R.G., Torrie, J.H., 1980. Principles and Procedures of Statistics. McGraw-Hill, New York.
Tamminga, S., Jansman, A.J.M., 1993. Animal Nutrition Lecture Notes. In: Williams, B.A. (Ed.), Wageningen
Agricultural University, The Netherlands.
Tamminga, S., van Vuuren, A.M., van der Koelen, C.J., Ketelaar, R.S., van der Togt, P.L., 1990. Ruminal
behavior of structural carbohydrates, non-structural carbohydrates and crude protein from concentrate
ingredients in dairy cows. Neth. J. Agric. Sci. 38, 513±526.
Tamminga, S., Van Straalen, W.M., Subnel, A.P.J., Meijer, R.G.M., Steg, A., Wever, C.J.G., Block, M.C., 1994.
The Dutch protein evaluation system: the DVE/OEB-system. Livestock Prod. Sci. 40, 139±155.
Tudor, G.D., 1990. The in¯uence of diet on the chemical composition of cattle and sheep. Thesis. The University
of Adelaide, Australia.
Van Bruchem, J., 1991. Physiology of the Gastrointestinal Tract. Wageningen Agricultural University, The
Netherlands.
Van der Poel, A.F.B., 1990. Effects of processing on bean (Phaseolus vulgaris L.) protein quality. J. Agric. Sci.
38, 513±526.
Van Straalen, W.M., Tamminga, S., 1990. Protein degradation in ruminant diets. In: Wiseman, J., Cole, D.J.A.
(Eds.), Feed Evaluation. Butterworth, London, pp. 55±72.
Yu, P., 1995. In¯uence of pressure toasting on rumen degradation characteristics and in vitro digestibility of
whole horse bean. Thesis. Wageningen Agricultural University, The Netherlands.