Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol82.Issue3-4.Dec1999:
Animal Feed Science and Technology
82 (1999) 157±175
Ruminal degradability and intestinal digestibility
of protein and amino acids in barley and oats
expander-treated at various intensities
Egil Prestlùkken*
Department of Animal Science, Agricultural University of Norway, P.O. Box 5025, N-1432 AÊs, Norway
Received 11 December 1998; received in revised form 23 August 1999; accepted 8 September 1999
Abstract
The objectives of the experiment were to study effects of pelleting or expander treatment at
various intensities (mild, medium, hard or maximum) prior to pelleting at two temperatures in the
mixer-conditioner (60 and 758C) on ruminal degradation and intestinal digestibility of protein and
amino acids in barley and oats, using nylon bag methods. Temperatures achieved were 85±95, 100±
110 and 115±1258C at mild, medium and hard intensity, whereas maximum temperature achieved
was 1258C for barley and 1408C for oats. Thus, temperatures higher than 130±1358C appeared
unrealistic under commercial conditions.
Pelleting decreased ruminal degradation of protein, especially at high temperature in the mixerconditioner. Expander treatment decreased ruminal degradation of protein further and the lowest
effective protein degradability (EPD) achieved was 30% for barley and 29% for oats, both obtained
at maximum temperature in the expander and high temperature in the mixer-conditioner. These
values are low compared to previous results and need to be verified. No negative effects of
treatment on digestibility of protein were observed. This indicates that the treatments shifted site of
protein digestion from the rumen to the small intestine.
Expander treatment did not alter the contents of any individual amino acid either in barley or in
oats. Expander treatment reduced ruminal degradation of total amino acids to the same extent as
protein. The variation in ruminal degradation among amino acids was considerable. Thus, ruminal
degradation of protein cannot be used for determination of ruminal degradation of all individual
amino acids. Expander treatment did not increase the content of indigestible amino acids in barley
or oats, indicating that amino acids were not heat-damaged. # 1999 Elsevier Science B.V. All
rights reserved.
Keywords: Expander treatment; Nylon bags methods; Ruminants; Protein; Amino acids
*
Tel.: 47-64-94-80-57; fax: 47-64-94-79-60
E-mail address: ihfegp@ihf.nlh.no (E. Prestlùkken)
0377-8401/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 1 1 0 - 8
158
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
1. Introduction
Cereal grains, such as barley and oats, serve as an energy constituent in diets for
ruminants. Although the content is low, protein from these grains constitutes a significant
part of the dietary protein. However, the protein in barley and oats is extensively degraded
in the rumen, resulting in a rather low protein value. Nylon bag studies have shown that
expander treatment can protect protein in barley or oats against ruminal degradation
(Weisbjerg et al., 1996; Lund, 1997; Prestlùkken, 1999) and thereby increasing their
protein value by shifting the site of protein digestion from the rumen to the small
intestine.
The major parameters affecting nutrients in thermo-mechanical processes as the
expander treatment are temperature, moisture content, residence time and mechanical
shear (Voragen et al., 1995). Of them, only the influence of temperature during the
expansion process have been discussed earlier. Moreover, the effects of the expander
treatment have not been properly verified under commercial processing conditions. In
addition, steam is usually added in the mixer-conditioner located prior to the expander. To
what extent the addition of steam in the mixer-conditioner influence effects of the
expander process has not been studied previously.
Modern systems for protein evaluation in ruminants are moving in the direction of
predicting the absorption of individual amino acids from the small intestine (Rulquin and
VeÁriteÁ, 1993). Several studies (Susmel et al., 1989; Erasmus et al., 1994; O'Mara et al.,
1997; van Straalen et al., 1997) indicate that ruminal degradability of amino acids are not
similar to protein. Thus, knowledge to ruminal degradability of individual amino acids is
required when protein value is to be expressed on the basis of individual amino acids.
Excessive heat treatment may reduce the availability of certain amino acids. Lysine, in
particular, is susceptible to heat treatment through the reaction with reducing sugars and
the formation of Maillard products (Broderick et al., 1991). The determination of
intestinal digestibility of individual amino acids is, therefore, of special importance in
heat-treated feedstuffs.
The objectives of the experiment were (1) to study effects of pelleting or expander
treatment at various intensities prior to pelleting at two temperatures in the mixerconditioner on ruminal degradation and intestinal digestibility of protein, and (2) to study
effects of the treatments on ruminal degradation and intestinal digestibility of individual
amino acids in barley and oats.
2. Material and methods
2.1. Animals and diets
Three non-lactating dairy cows fitted with a flexible rumen cannulae (Bar Diamond,
Parma, ID, USA; 100 mm i.d.) and a simple T-type PVC cannulae (20 mm i.d.) located in
the duodenum 50±60 cm distal to pylorus (distal to the bile duct entrance), were used. At
06:00 and 15:00 hours, the cows were fed equal amounts of a standardised diet consisting
of grass hay (4 kg per day; 120 g CP, 60 g ash, 25 g fat, 600 g neutral detergent fibre
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
159
(NDF), g kgÿ1 DM) and a concentrate mixture (1.8 kg per day; 175 g CP, 55 g ash, 50 g
fat, 195 g NDF and 440 g starch plus sugar, g kgÿ1 DM). The cows were housed in tiestalls in a metabolism unit. Animal care was conducted according to laws and regulations
controlling experiments with live animals and the experiment was approved by the
Norwegian Animal Research Authority.
2.2. Experimental feedstuffs and treatments
The experimental feedstuffs were barley and oats. The feedstuffs were ground on a
horizontal shaft hammer mill and a sample was taken as an untreated control.
Experimental samples were produced at 60 and 758C in the mixer-conditioner. After the
mixer-conditioner, the feedstuffs were either subjected to traditional pelleting (75±808C)
or heat treatment with a Kahl OE 23 Expander (A. Kahl GmbH, Reinbek, Germany) at
various intensities (mild, medium, hard or maximum) prior to pelleting. In the samples
only pelleted, the expander acted as a screw feeder from the mixer-conditioner to the
pellet press. In the samples expander-treated prior to pelleting, treatment intensity was
regulated by adjusting the hydraulic pressure on the conical-shaped resistor in the outlet
of the expander, and at highest temperature stage in the mixer-conditioner, also through
addition of steam in the expander. Monitored treatment conditions are listed in Table 1.
2.3. Nylon bag measurements
Ruminal degradation and intestinal digestibility measurements were carried out using
nylon bag methods mainly as described by Madsen et al. (1995) and Prestlùkken (1999).
In the mobile bag experiment, original feed and residues after 16 h rumen incubation
were used. Except for 16 h residues for determination of intestinal digestibility, all
residues were milled for 1 min at frequency 80 with the MM2000 Mixer Mill (RETCH
GmbH & Co. KG, Haan, Germany).
2.4. Chemical analysis
The feedstuff samples were milled through a 1 mm screen before analysis. In all
samples, nitrogen (Kjeldahl-N) and dry matter were determined as described by AOAC
(1990). Within feedstuff, four samples were selected for additional chemical analysis.
Ash and fat (acid hydrolysis with petroleum ether extraction) were determined using
AOAC (1990) methods. Acid detergent fibre (ADF) and NDF were determined according
to van Soest et al. (1991) using the ANKOM220 Fiber Analyzer (ANKOM Technol.,
Fairport, NY). Starch was analysed according to the method of McCleary et al. (1994)
without correction for sugar. Amino acid analysis was performed according to Directive
98/64/EC (EEC, 1998), using acid hydrolysis. The amino acids were separated with ionexchange chromatography and quantified by UV-detection at 570 nm (440 nm for
proline) after post-column derivatisation with ninhydrin using the Biochrom 20 Amino
Acid Analyser (Pharmacia Biotech, Cambridge, UK). Tyrosine was analysed in oxidised
samples although oxidation reduces the content of tyrosine (Mason et al., 1980). Based on
unpublished results from our laboratory, tyrosine was increased by 10% to compensate
160
Treatmenta
Pelleted
Mild
Medium
Hard
Max
608C in mixer-conditioner
Barley, Sample No.
Capacity, expander (t, hÿ1)
Pressure, expander (bar)b
Temp., mixer (8C)
Temp., expander (8C)
H2OFeed (%)c
Oats, Sample No.
Capacity, expander (t, hÿ1)
Pressure, expander (bar)b
Temp., mixer (8C)
Temp., expander (8C)
H2OFeed (%)c
a
2
±
±
60
±
14.4
13
±
±
59
±
12.9
3
2.0
15
60
80
14.4
14
3.3
20
63
86
13.2
Pelleted
Mild
Medium
Hard
Max
9
3.0
25
76
102
16.9
20
2.9
33
75
108
15.5
10
3.0
33
75
114
16.9
21
2.8
45
74
126
15.5
11
3.0
33
75
125
16.9
22
2.7
50
75
140
15.5
758C in mixer-conditioner
4
2.0
25
60
95
14.4
15
2.7
42
62
105
13.2
5
2.0
42
62
116
14.5
16
2.1
46
59
120
12.9
6
2.0
42
62
125
14.5
17
2.1
50
60
135
13.0
7
±
±
74
±
15.4
18
±
±
74
±
14.0
8
2.8
10
72
90
16.4
19
2.6
10
76
92
15.5
Ordinary pelleting and expander treatment at mild, medium, hard or maximum treatment intensity.
Hydraulic pressure required to keep the cone in position.
c
Calculated water content in the feed samples based on 10.9 and 9.5% water in untreated barley and oats (Table 2), assuming a 0.7% increase in feed moisture
content for every 108C increase in temperature (A. Kahl, pers. commun.).
b
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Table 1
Processing conditions
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
161
for losses during oxidation. The content of serine, valine and isoleucine was increased by
6% for incomplete recovery after hydrolysis (Rudemo et al., 1980). Nitrogen in residues
after ruminal and intestinal incubation was determined according to Dumas method
(AOAC, 1990) using the EA 1108 Elemental Analyser (Fison Instruments S.p.A, Rudano
Milan, Italy).
2.5. Calculations and statistical analysis
Amino acid protein (AA-protein) was calculated using water-corrected molecular
weights. Ruminal degradation characteristics of CP were calculated as described by
érskov and McDonald (1979) using the PROC NLIN procedure in the statistical analysis
systems (SAS, 1990). Effective rumen degradability of protein (EPD) was calculated
assuming a rumen outflow rate of 8% hÿ1. Disappearance of amino acids from the rumen
nylon bag was calculated on animal basis as the mean of disappearance after 8, 16 and
24 h incubation time. Digestibility of rumen undegraded protein (dUDP) was calculated
according to Hvelplund et al. (1992). True indigestible residue of protein and amino acids
after intestinal incubation was calculated as a percentage of intact feed. Increase in the
moisture content of the feedstuffs during processing (H2OFeed) was calculated assuming
that 108C increase in temperature by the steam addition increased the water content with
0.7% units (A. Kahl GmbH, pers. commun.).
Analysis of variance (ANOVA) was performed with the GLM procedure in SAS (1990)
with effect of treatment and cow in the model. Means were separated with the PDIFF
statement. Means among treatments and among amino acids within treatment were
separated with the Duncan multiple range comparison statement. The significance level
was P < 0.05 unless stated otherwise.
3. Results and discussion
3.1. Effect of treatment on chemical composition and amino acids
In general, the chemical composition of the feedstuff samples was within expected
ranges (Table 2). The expander treatment did not appear to severely affect the
composition of feedstuffs except for a tendency to reduced NDF and ADF content. Heat
treatment increases the solubility of fibres (Shinnick et al., 1988; Vranjes and Wenk,
1995). Thus, the observed effect might be analytical rather than nutritional. Compared to
the Danish amino acid table (Kristensen et al., 1996), the content of amino acid nitrogen
in barley and oats was high (Table 3). However, the proportions of individual amino acids
were within the expected range in all samples. Furthermore, the expander treatment did
not influence the proportion of lysine or other essential amino acids relative to nonessential amino acids (Table 3). This indicates that amino acids, and lysin in particular,
were not heat damaged as might expected (Broderick et al., 1991; Schwab, 1995; Voragen
et al., 1995). However, the amino acid analysis may hydrolyse bonds that are not
hydrolysed by intestinal enzymes (Dworschak, 1980; Mauron, 1990). If this happens,
amino acid analysis will overestimated bioavailability of e.g., lysine.
162
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Table 2
Chemical composition (g kgÿ1 DM if not stated otherwise) and content of amino acid protein (AA-protein)a in
samples of barley and oats
Barley
Sample No.
b
Treatments
ÿ1
DM (g kg )
Ash
Fat
NDF
ADF
Starch
CP
AA-proteina
Oats
1
6
8
11
12
17
19
22
Untreated
62/125
72/90
75/125
Untreated
60/135
76/92
75/140
891
27
26
196
49
578
107
95
930
26
19
173
43
585
109
92
910
27
26
195
40
589
114
100
905
26
23
172
46
585
110
96
905
32
41
308
136
478
109
89
924
29
39
271
114
523
108
88
910
29
44
279
115
490
106
90
912
29
43
245
100
495
108
87
a
AA-protein calculated using water-corrected molecular weights.
Processing conditions: Untreated control and temperatures monitored in mixer-conditioner/expander (8C).
See also Table 1 for explanation.
b
Table 3
Amino acid N (g AAN 100 gÿ1 N), amino acid profile (g AA 100 gÿ1 AA) of barley and oatsa
Barley
Sample No.
b
Treatments
1
6
Control 62/125
Total AAN
83.3
Essential AA (EAA)
Arginine
5.4
Histidine
2.5 a
Isoleucine
3.9 ab
Leucine
7.2
Lysine
3.9 ab
Methionine
1.7
Phenylalanine 5.6
Threonine
3.7
Tyrosine
3.0
Valine
5.4
Sum EAA
42.3
Non essential AA (NEAA)
Alanine
4.3
Aspartic acid 6.2
Cystein
2.5
Glutamic acid 24.6 a
Glycine
4.2 b
Proline
11.3
Serine
4.6
Sum NEAA 57.7
a
Oats
78.5
8
12
c
17
22
75/125
SEM
Control 60/135
76/92
75/140
SEMc
84.7
82.2
1.58
80.3
82.5
79.9
1.25
5.4
2.5 ab
3.9 ab
7.2
3.8 ab
1.6
5.7
3.6
3.3
5.4
42.4
0.04
0.02
0.03
0.05
0.02
0.08
0.06
0.10
0.11
0.07
0.15
7.1
7.2
2.4 b
2.5 a
4.1 a
4.0 b
7.6
7.5
4.1
4.1
1.7
1.8
5.4
5.4
3.8
3.9
3.4
3.5
5.9 ab 5.8 abc
45.5
45.6
4.3
4.4
6.4
6.1
2.4
2.5
24.3 ab 24.2 ab
4.4 a
4.4 a
11.3
11.3
4.8
4.6
57.8
57.6
0.07
0.13
0.03
0.10
0.03
0.07
0.13
0.15
5.2
5.0
4.8
8.4
8.3
8.3
3.2 ab 3.1 b
3.3 a
21.5
21.2
21.3
5.4
5.4
5.2
5.5 c
6.3 ab 6.5 a
5.2
5.3
5.3
54.5
54.4
54.7
80.0
Different letters within grain type indicates statistical differences (p < 0.05).
See Tables 1 and 2 for explanation.
c
SEM: standard error mean.
b
19
72/90
5.4
5.4
2.5 ab 2.4 b
4.0 a
3.8 b
7.2
7.1
3.8 b
3.9 a
1.7
1.9
5.6
5.5
3.7
3.8
3.0
3.0
5.5
5.4
42.4
42.2
4.3
6.2
2.5
24.2 b
4.4 a
11.5
4.7
57.6
11
7.1
7.1
2.4 ab 2.5 ab
3.9 b 4.1 a
7.3
7.6
4.2
4.1
1.8
1.7
5.4
5.3
3.9
3.9
3.7
3.5
5.5 c
6.0 a
45.3
45.7
5.3
8.2
3.2 ab
20.9
5.4
6.0 bc
5.3
54.3
0.15
0.01
0.02
0.14
0.14
0.05
0.03
0.08
0.18
0.08
0.14
0.14
0.15
0.05
0.24
0.11
0.11
0.09
0.14
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
163
Fig. 1. Effective protein degradability (EPD) in untreated (Untr.), pelleted (Pell.) and different intensities of
expander treatment of barley at two temperatures in the mixer-conditioner. Different letters indicate statistical
differences between treatments (p < 0.05, MSE 3.9).
3.2. Effect of treatment on ruminal degradation of protein
It is well known that unfolding and denaturation of proteins at moderate heat can
increase digestibility of protein by making anti-nutritional proteins inactive. When heat is
added, bonds that stabilise the three-dimensional structure of proteins will break. If
hydrophobic groups are exposed, this will result in reduced solubility of proteins
(Voragen et al., 1995), and consequently reduced ruminal degradation of protein.
Consistent with Weisbjerg et al. (1996), Lund (1997) and Prestlùkken (1999), the
expander treatment, and even ordinary pelleting, reduced EPD markedly in barley (Fig. 1)
and oats (Fig. 2). Except for the ordinary pelleted samples, increased temperature in the
mixer-conditioner had no effect on EPD. In fact, in oats, EPD tended to be lower at the
low temperature in the mixer-conditioner (Fig. 2). This observation indicates that input of
mechanical energy is the main factor determining the effect of the expander treatment.
Thus, addition of thermal energy as steam probably plays a role only when input of
mechanical energy is low. Expander treatment of barley beyond mild intensity had only a
minor effect on EPD, whereas increased treatment intensity gradually decreased EPD in oats.
These findings are in agreement with Prestlùkken (1999), and have also been shown for
barley by Lund (1997). McNiven et al. (1995) and Prestlùkken (1999) have discussed
mechanisms for the different response of barley and oats to heat treatments. Differences in
morphologic configuration of the starch-protein matrix probably play an important role.
3.3. Effect of treatment on ruminal degradation of amino acids
Numerous publications exist on the effect of ruminal exposure on degradation of amino
acids in feedstuffs for ruminants (Varvikko et al., 1983; Mir et al., 1984; Varvikko, 1986;
164
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Fig. 2. Effective protein degradability (EPD) in untreated (Untr.), pelleted (Pell.) and different intensities of
expander treatment of oats at two temperatures in the mixer-conditioner. Different letters indicate statistical
differences between treatments (p < 0.05, MSE 4.4).
Crooker et al. (1986, 1987); Susmel et al., 1989; Erasmus et al., 1994; Weisbjerg et al., 1996;
Lund, 1997; O'Mara et al., 1997; van Straalen et al., 1997; Zebrowska et al., 1997) and
rapeseed meal, soybean meal and fish meal seem to be the most commonly studied. Of the
literature studied, only three references determined ruminal degradation of individual amino
acids of barley or oats (Weisbjerg et al., 1996; Lund, 1997; Zebrowska et al., 1997), and only
Weisbjerg et al. (1996) and Lund (1997) included heat-treated barley in the study.
Ruminal degradation of individual amino acids in the untreated and the expandertreated samples of barley and oats are shown in Figs. 3 and 4, respectively. In general, the
expander treatment reduced ruminal degradation of total amino acids to the same extent
as protein, indicating that ruminal degradation of protein can be used for the
determination of ruminal degradation of total amino acids. However, among the
individual amino acids there was considerable variation in ruminal degradation. Thus,
ruminal degradation of protein or total amino acids cannot be used for determination of
ruminal degradation of the individual amino acids. In the present experiment, arginine,
glutamic acid, cysteine and, to some extent, histidine were degraded to a relatively high
degree, whereas isoleucine, leucine, methionine, tyrosine, valine, and to some extent,
phenylalanine and alanine were degraded to a relatively low degree. In general, these
observations are in agreement with the literature referred earlier. However, considerable
variation among studies, and among feedstuffs within study, make it difficult to make
unambiguous conclusions on ruminal degradation of individual amino acids. Romagnolo
et al. (1994) suggested that hydrophobicity of proteins might be associated with reduced
degradability in the rumen. Although that study was on protein fractions, it is interesting
to observe that hydrophobic amino acids as leucine, isoleucine, phenylalanine,
methionine, valine, alanine and tyrosine, in the present study in general were degraded
to a lower extent than more hydrophilic amino acids as histidine, arginine, lysine,
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Fig. 3. Ruminal degradation of protein (N), amino acids (AA), essential AA (EAA), none essential AA (NEAA) and individual amino acids in untreated and expandertreated barley. Within sample, mean value for AA is shown as a horizontal line. Different letters indicate significant differences (p < 0.05) among AA within treatment.
MSE mean square error.
165
166
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Fig. 4. Ruminal degradation of protein (N), amino acids (AA), essential AA (EAA), none essential AA (NEAA) and individual amino acids in untreated and expandertreated oats. Within sample, mean value for AA is shown as a horizontal line. Different letters indicate significant differences (p < 0.05) among AA within treatment.
MSE mean square error.
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
167
cysteine, glutamic acid, glycine and serine (Figs. 3 and 4). Thus, their suggestion may be
of some relevance for individual amino acids as well.
As mentioned earlier, heat treatment may create Maillard products. If Maillard
products are formed, a reduced ruminal degradation of lysine might be expected. Lund
(1997), studying barley and seven other feedstuffs, concluded that the expander treatment
had no specific effect on ruminal degradation of lysine compared to total amino acids. In
the present study, the expander treatment tended to reduce ruminal degradation of lysine
relative to the mean for amino acids in barley (Fig. 3), whereas in oats, the opposite was
observed with a tendency to increased degradation of lysine compared to the mean of
amino acids (Fig. 4). Thus, treatment effects may vary among feedstuffs. However, the
expander treatment tended to reduce ruminal degradation of total essential amino acids
both in barley and in oats compared to total non-essential amino acids. If the decrease in
ruminal degradation is not followed by reduced intestinal digestibility of essential amino
acids, the expander treatment may improve the amino acid profile of escape protein.
3.4. Effect of treatment on intestinal digestion of protein
Hvelplund et al. (1992) proposed that feedstuffs contain a constant amount of
indigestible protein and that intestinal digestibility of rumen undegraded protein can be
calculated from nylon bag studies with intact feed. However, in barley, oats and several
other feedstuffs, the hypothesis of a constant indigestible protein residue does not seems
to be true (Volden and Harstad, 1995). Thus, digestibility of rumen undegraded protein
should be calculated on the basis of residues pre-incubated in the rumen (Madsen et al.,
1995). In the present experiment, indigestible protein was measured on intact feed and on
residues pre-incubated in the rumen for 16 h. In agreement with Volden and Harstad
(1995) and Prestlùkken (1999), rumen pre-incubation reduced indigestible protein,
especially in barley (Table 4). Furthermore, for intact barley, the content of indigestible
protein decreased in all expander-treated samples compared to the untreated. Since the
indigestible content of protein in the untreated sample was in agreement with that
determined by Volden and Harstad (1995), a positive effect of treatment on digestibility
of protein in intact barley cannot be excluded. However, this was not confirmed in the
study of Prestlùkken (1999). In oats, there was a tendency for treatment intensity to
increase the content of indigestible protein. Prestlùkken (1999) also observed this. The
increase was, however, marginal even at the highest treatment intensity. In fact, due to the
considerable reduction in ruminal degradation of protein, the expander treatment
increased digestibility of rumen undegraded protein, especially in oats (Table 4).
Therefore, as described by Satter (1986), the expander treatment seems to maximise the
amount of protein that can escape rumen degradation and still be digested in the intestine.
However, as shown by McNiven et al. (1994), with oats roasted at 1688C, the risk for
reducing digestibility of protein by heat treatment cannot be ignored.
3.5. Effect of treatment on intestinal digestion of amino acids
Although the mobile nylon bag experiment indicates that the expander treatment does
not decrease intestinal digestibility of protein (Table 4), severe heat treatment may have
168
Treatmentsc
Untr.
Pell.
Mild
Medium
Hard
Max
Pell.
608C in mixer-conditioner
Barley, No.
IF
IF16
dUDP
Oats, No.
IF
IF16
dUDP
a
1
6.07
1.73
95.8
12
2.42
1.88
87.8
a
b
b
cd
e
2
3.35
1.97
96.1
13
2.92
1.83
90.1
d
ab
ab
d
d
3
3.28
1.81
97.2
14
2.91
1.93
95.9
d
a
ab
cd
ab
4
4.52
2.08
96.8
15
2.87
2.07
96.9
Mild
Hard
9
4.10
2.07
97.0
20
3.70
2.01
96.7
10
4.93
2.29
96.5
21
3.40
2.32
96.5
MSEd
Max
758C in mixer-conditioner
bcd
ab
ab
abcd
a
5
3.92
2.22
96.6
16
3.12
2.18
96.8
cd
ab
ab
abc
a
6
4.31
1.98
97.2
17
2.98
2.29
96.7
bcd
a
ab
ab
a
7
4.72
1.92
96.5
18
3.14
1.87
93.8
abcd
ab
ab
d
c
8
4.15
2.07
96.7
19
2.79
1.96
95.4
Estimated according to Hvelplund et al. (1992) using indigestible residues after 16 h rumen pre-incubation.
Different letters within row indicates statistical differences (p < 0.05).
c
See Table 1 for explanation.
d
MSE: mean square error.
b
Medium
bcd
ab
ab
cd
b
bcd
ab
a
bcd
a
abc
ab
ab
a
a
11
5.47
2.08
97.0
22
3.79
2.18
96.8
ab
a
0.59
0.11
0.38
a
abc
a
0.30
0.03
0.30
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Table 4
Indigestible protein in intact feed (IF) and residues after 16 h rumen pre-incubation (IF16). Values in % of intact feed. Digestibility (%) of rumen undegraded proteina,b
(dUDP)
169
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Table 5
Indigestible protein and amino acids (AA) measured in residues after 16 h rumen pre-incubation. Values in % of
intact feeda
Barley
Sample No.
b
Treatments
1
Oats
6
8
Control 62/125 72/90
Protein
2.28
Amino acids
1.72
Essential AA (EAA)
Arginine
1.50
Histidine
1.59
Isoleucine
1.83
Leucine
1.83
Lysine
2.03
Methionine
1.65
Phenylalanine 1.70
Threonine
2.27
Tyrosine
1.87
Valine
1.98
Sum EAA
1.78
Non essential AA (NEAA)
Alanin
2.69
Aspartic acid 2.69
Cystein
2.01
Glutamic acid 0.75
Glysin
3.03
Prolin
1.14
Serin
2.09
Sum NEAA
1.65
11
12
17
19
22
75/125 SEM
Control
60/135
76/92
75/140 SEMc
c
2.04
1.75
2.08
1.73
2.16
1.71
0.08
0.06
2.07 b
1.47 bc
2.42 a
1.57 ab
2.10 b
1.32 c
2.42 a
1.66 a
0.10
0.05
1.54
1.67
1.84
1.86
1.90
1.65
1.72
2.38
1.64
2.05
1.77
1.64
1.65
1.84
1.88
2.09
1.51
1.73
2.16
1.84
1.88
1.81
1.53
1.62
1.92
1.81
2.03
1.67
1.67
2.15
1.74
1.88
1.76
0.06
0.05
0.07
0.07
0.09
0.11
0.06
0.12
0.06
0.09
0.07
0.84
1.66
1.32
1.65
1.70
1.56
1.28
1.68
1.26
1.54
1.36
ab
bc
0.91
1.87
1.65
1.75
1.69
1.40
1.53
1.53
1.74
1.70
1.43
a
ab
0.73
1.60
1.26
1.54
1.52
1.33
1.32
1.50
1.30
1.49
1.22
b
c
1.05
1.92
1.74
1.78
1.86
1.57
1.69
1.88
1.58
1.80
1.52
a
a
0.06
0.07
0.11
0.06
0.09
0.04
0.08
0.10
0.17
0.07
0.05
2.80
2.78
1.83
0.82
3.04
1.15
2.18
1.71
2.72
2.53
1.95
0.80
2.88
1.12
2.19
1.65
2.77
2.60
1.91
0.77
3.00
1.11
2.08
1.66
0.09
0.10
0.07
0.03
0.09
0.04
0.08
0.06
1.93
1.51
1.55
0.86
2.40
1.99
2.06
1.62
bc
b
ab
ab
a
a
ab
2.29
1.70
1.96
0.97
2.58
1.95
1.90
1.73
ab
a
a
a
a
ab
ab
2.03
1.39
1.57
0.78
2.26
1.44
1.50
1.43
c
b
b
b
b
b
b
2.26
1.78
2.07
1.07
2.61
2.11
1.82
1.80
a
a
a
a
a
ab
a
0.12
0.07
0.10
0.04
0.07
0.12
0.13
0.05
ab
bc
bc
ab
ab
a
b
ab
ab
ab
ab
a
ab
b
ab
b
b
c
c
b
b
b
b
b
a
a
a
a
a
a
a
a
a
Different letters within grain type indicates statistical differences (p < 0.05).
See Tables 1 and 2 for explanation.
c
SEM: standard error mean.
b
specific effects on certain amino acids (Broderick et al., 1991; Schwab, 1995; Voragen et
al., 1995). In agreement with Lund (1997), the results presented do not indicate that heat
treatment with an expander decreased the content of digestible lysine or any other amino
acid. However, the indigestible residues among amino acids varied considerably and
among the essential amino acids, lysine was one with a relatively high indigestible
residue (Table 5). Consequently, digestibility of lysine probably was low compared to
most other amino acids. A relative low digestibility of lysine was also observed by
Weisbjerg et al. (1996), studying 15 feedstuffs. However, as shown in Table 5,
indigestible residues were in general low. Thus, in practice, digestibility of dietary amino
acids was high both in untreated and treated barley and oats.
3.6. Amino acid profiles of ruminal and intestinal residues
Intestinal incubation markedly reduced the content of amino acids nitrogen both in
untreated and expander-treated barley (Table 6) and oats (Table 7). Reduced
170
Table 6
Amino acid N (g AAN 100 gÿ1 N), amino acid profile (g AA 100 gÿ1 AA) of intact feed (IF), residues after washing in machine (W), residues after 16 h rumen
incubation (R) and residues after intestinal incubation of 16 h rumen residues (I) in untreated and expander-treated barleya
Untreated barley
IF
Aamino acid N
83.6 a
Essential AA (EAA)
Arginine
5.4 a
Histidine
2.5 a
Isoleucine
4.0 c
Leucine
7.3 bc
Lysine
3.9 bc
Methionine
1.8
Phenylalanine
5.7 b
Threonine
3.7 b
Tyrosine
3.0 abc
Valine
5.4 b
Sum EAA
42.6 b
Non essential AA (NEAA)
Alanine
4.2 b
Aspartic acid
6.0 b
Cysteine
2.5 b
Glutamic acid
24.6 b
Glycine
4.2 b
Proline
11.2 b
Serine
4.6 b
Sum NEAA
57.4 b
Untreated vs. expanded
Expander-treated barley
R
I
IF
W
R
I
81.6 a
78.2 a
62.9 b
78.8 a
79.8 a
81.7 a
68.0 b
5.2
2.4
4.0
7.1
3.6
1.7
5.7
3.5
2.9
5.3
41.4
4.5
2.2
4.8
7.6
4.0
1.8
6.1
3.7
3.5
5.4
43.5
4.9
2.4
4.5
8.2
4.9
1.8
5.9
5.1
3.3
6.5
47.5
5.4
2.5
4.0
7.3
3.8
1.8
5.6
3.7
3.0
5.5
42.6
5.3
2.5
4.1
7.1
3.9
1.8
5.6
3.7
3.4
5.6
42.9
5.3
2.5
4.3
7.9
3.8
1.9
5.6
3.7
3.6
5.9
44.5
4.9
2.5
4.4
8.1
4.4
1.8
5.8
5.1
3.3
6.6
47.0
W
a
a
c
c
c
b
b
bc
b
c
4.1 b
5.5 c
2.2 c
25.8 a
4.1 b
12.5 a
4.5 bc
58.6 a
c
b
a
b
b
a
b
a
b
b
4.4 b
6.4 b
1.7 d
24.7 b
3.6 c
11.4 b
4.3 bc
56.4 b
b
a
b
a
a
ab
a
ab
a
a
7.0 a
10.1 a
2.9 a
11.2 c
7.7 a
7.7 c
5.9 a
52.5 c
a
b
b
b
b
b
c
c
4.2 c
6.2 b
2.4 b
24.2 a
4.3 b
11.4 a
4.7 b
57.4 a
a
b
b
b
b
ab
bc
c
4.4 bc
5.6 c
2.3 b
23.9 ab
4.3 b
11.7 a
4.7 b
57.2 a
Contrasts
a
a
a
b
b
a
b
b
4.6 b
6.4 b
2.2 c
22.9 b
4.1 b
10.5 b
4.8 b
55.5 b
b
a
a
a
a
ab
a
a
7.0 a
10.1 a
2.7 a
11.7 c
7.8 a
7.7 c
6.1 a
53.0 c
IF
W
R
I
2.46
n.s.
n.s.
n.s.
n.s.
0.05
0.06
0.05
0.11
0.14
0.09
0.09
0.10
0.15
0.1 3
0.36
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.02
n.s.
0.01
0.01
0.01
0.01
n.s.
n.s.
n.s.
0.01
n.s.
n.s.
0.03
0.08
n.s.
n.s.
n.s.
n.s.
0.02
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.10
0.18
0.04
0.33
0.09
0.22
0.10
0.36
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.06
0.09
0.05
0.01
n.s.
0.02
n.s.
0.01
0.10
n.s.
0.01
0.01
0.01
0.01
0.01
0.08
n.s.
n.s.
0.01
n.s.
n.s.
n.s.
n.s.
n.s.
a
Different letters within treatment indicates statistical differences (p < 0.05). Significance level in contrasts P < 0.10. SEM: standard error mean; n.s.: indicates not
significant.
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
SEM
Table 7
Amino acid N (g AAN 100 gÿ1 N), amino acid profile (g AA 100 gÿ1 AA) of intact feed (IF), residues after washing in machine (W), residues after 16 h rumen
incubation (R) and residues after intestinal incubation of 16 h rumen residues (I) in untreated and expander-treated oatsa
Untreated oats
IF
Amino acid N
80.3 a
Essential AA (EAA)
Arginine
7.1 a
Histidine
2.4 bc
Isoleucine
4.1 b
Leucine
7.6 b
Lysine
4.1 b
Methionine
1.7 b
Phenylalanine
5.4 ab
Threonine
3.8 b
Tyrosine
3.4 a
Valine
5.9 c
Sum EAA
45.5 c
Non essential AA (NEAA)
Alanine
5.2 c
Aspartic acid
8.4 c
Cystein
3.2 a
Glutamic acid
21.5 a
Glycine
5.4 bc
Proline
5.5 b
Serine
5.2 b
Sum NEAA
54.5 a
Untreated vs. expanded
Expander-treated oats
R
I
IF
W
R
I
78.5 a
71.4 b
57.4 c
80.0 a
79.7 a
75.0 b
52.5 c
7.5
2.5
4.4
7.7
4.1
1.8
5.6
3.8
3.3
6.5
47.2
6.1
2.3
5.1
8.2
5.2
2.1
5.7
4.7
2.8
6.7
49.3
3.9
2.9
4.0
8.2
5.0
1.6
5.2
4.6
3.3
6.2
44.8
7.2
2.5
4.0
7.5
4.1
1.8
5.4
3.9
3.5
5.8
45.6
6.9
2.5
4.3
7.5
4.4
1.9
5.3
4.0
3.7
6.1
46.6
7.0
2.5
4.4
8.1
3.9
1.9
5.7
3.9
3.7
6.3
47.4
4.2
2.8
4.3
8.2
4.3
1.5
5.4
4.2
3.5
6.4
44.7
W
a
b
b
b
b
b
a
b
a
ab
b
5.1 c
8.0 c
2.5 b
21.6 a
5.2 c
5.5 b
5.0 b
52.8 b
b
c
a
a
a
a
a
a
b
a
a
6.3 b
9.8 a
1.9 c
16.7 b
5.6b
5.3 b
5.2 b
50.8 c
c
a
b
a
a
c
b
a
a
bc
c
7.0 a
9.1 b
3.4 a
12.4 c
8.7 a
7.6 a
7.0 a
55.2 a
a
b
b
b
b
b
b
bc
5.0 b
8.3 b
3.1 b
21.2 a
5.4 b
6.3 b
5.3 b
54.4 ab
a
b
ab
b
ab
b
ab
ab
5.2 b
8.2 b
3.0 b
20.4 a
5.3 b
6.1 b
5.3 b
53.4 bc
Contrasts
a
b
a
a
a
a
a
a
5.2 b
8.1 b
2.4 c
21.4 a
4.8 c
5.9 b
4.9 b
52.6 c
IF
W
R
I
2.10
n.s.
n.s.
0.08
0.09
a
c
0.26
0.08
0.10
0.16
0.17
0.04
0.08
0.19
0.13
0.19
0.38
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.08
0.04
n.s.
n.s.
n.s.
n.s.
0.01
0.02
0.01
n.s.
0.01
0.01
n.s.
0.01
0.01
0.03
0.01
n.s.
n.s.
0.04
n.s.
0.01
n.s.
0.06
0.09
n.s.
n.s.
n.s.
7.3 a
8.9 a
3.5 a
13.1 b
8.7 a
7.7 a
6.2 a
55.3 a
0.16
0.21
0.06
0.45
0.14
0.13
0.34
0.38
n.s.
n.s.
n.s.
n.s.
n.s.
0.01
n.s.
n.s.
n.s.
n.s.
0.01
n.s.
n.s.
0.02
n.s.
n.s.
0.01
0.01
0.01
0.01
0.01
0.01
n.s.
0.01
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.06
n.s.
b
a
a
a
c
b
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
SEM
a
Different letters within treatment indicates statistical differences (p < 0.05). Significance level in contrasts P < 0.10. SEM: standard error mean; n.s. indicate not
significant.
171
172
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
concentration of amino acids shows that digestibility of amino acids was high relative to
other nitrogen components. The amino acid profile after intestinal incubation differed to a
great extent from the profile of the intact feed as well as the residues after washing and
ruminal incubation. This observation confirm that digestibility varied among individual
amino acids. No major differences between the amino acid profile of residues after
intestinal incubation of untreated and expander-treated samples was found, supporting the
statement that expander treatment does not decrease digestibility of specific individual
amino acids.
To obtain true ruminal degradation of protein and amino acids, correction for microbial
contamination of nylon bag residues are recommend (Varvikko, 1986; Nocek, 1988;
Erasmus et al., 1994). Since amino acid profile of the rumen microbes differs from that of
barley and oats, severe microbial contamination would alter amino acid profile of the
rumen nylon bag residues. Thus, differences in amino acid profile between intact feed and
the rumen nylon bag residues might be explained by microbial contamination. However,
except for untreated oats, ruminal incubation did not increase the relative proportion of
e.g., lysine compared to intact feed. The concentration of lysine in protein from particle
adherent bacteria is almost twice the concentration found in protein from barley and oats.
Erasmus et al. (1994), washing the nylon bags for 10 min in a washing machine, found on
average only 3.9% microbial contamination in residues after 16 h rumen incubation for
12 feedstuffs. In the present study, the bags were washed for 10 min three times in a
washing machine. Thus, microbial contamination was probably not severe in the present
study either. Consequently, the difference in amino acid profile between intact feed and
nylon bag residues most likely was attributed to different ruminal degradation among
dietary amino acids. Moreover, the similarity in amino acid profile between intact feed
and residues after ruminal incubation was greater for expander-treated samples than for
untreated samples. This shows that dietary protein was protected from being degraded in
the rumen, confirming that increased rumen escape of dietary amino acids can be
expected when expander-treating barley and oats.
3.7. Processing conditions
In a previous experiment conducted at the A. Kahl pilot plant, the expander
temperatures ranged from 1308C at mild to 1708C at hard treatment intensity
(Prestlùkken, 1999). In the present experiment conducted at a commercial production
plant, the expander temperatures ranged from 85±95, 100±110 and 115±1258C at mild,
medium and hard treatment intensity, respectively (Table 1). The maximum temperature
achieved was 1258C for barley and 1408C for oats. However, increasing the temperature
above 1208C was dependent on the skill of the operator. In addition, to achieve these high
temperatures, the expander must be well maintained with low mechanical wear.
Therefore, in agreement with the experience of the Norwegian compound feed industry,
which has used expanders for many years, processing temperatures above 130±1358C
usually are unrealistic under commercial conditions.
With 108C as a start temperature, the addition of steam increased the temperature by
about 50 and 658C at low and high temperature in the mixer-conditioner, respectively.
This accounted for a 3.5 and 4.5% increase of water in the feed material. Thus, at the low
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
173
temperature in the mixer-conditioner, the water content was around 14.5% in barley and
13.0% in oats during the expander processing (Table 1). The increase in temperature
caused by the addition of steam in the expander was not monitored. Assuming that the
temperature increased from 75 to 958C, 1.4% water was added in the expander as steam.
Consequently, content of water in the feed material were around 2.5% units higher during
the expander treatment at the high compared to the low temperature in the mixerconditioner. Since the presence of water is important in hydrothermal reactions (Voragen
et al., 1995), increased water content was expected to increase the treatment effects of the
expander process. However, this seemed not to be the case in the present study. Moreover,
with respect to the parameters studied, shifting the administration of energy in the
expander process from mainly mechanical energy at low temperature in the mixerconditioner to more hydrothermal energy at high temperature in the mixer conditioner,
seemed not to be crucial for the treatment effects. The through-put of the expander
increased from around 2.0 tonnes hÿ1 at the low temperature to around 3.0 tonnes hÿ1 at
the high temperature in the mixer-conditioner, indicating that the water content of the
feed material is important for the through-put of the expander. However, increased
through-put resulted in decreased residence time, which again affects time dependent
reactions. Thus, the effects caused by reduced residence time may confound the expected
increase in treatment effects caused by addition of water. Nevertheless, the results
confirm that expander treatment is an excellent method to alter the site and extent of
digestion of protein and amino acids in ruminants. It must, however, be emphasised that
the values observed for EPD at the medium, hard and maximum treatment intensities are
lower than previous results (Prestlùkken, 1999). The values need to be verified in
additional experiments before implementing the results in commercial feed production.
4. Conclusions
Expander treatment and even ordinary pelleting reduced ruminal degradation of protein in
barley and oats considerably. In general, the treatments reduced ruminal degradation of total
amino acids to the same extent as protein, indicating that ruminal degradation of protein can
be used for the determination of total amino acid degradation. However, among the individual
amino acids there was considerable variation in ruminal degradation. Thus, ruminal
degradation of protein cannot be used for determination of ruminal degradation of all of the
individual amino acids. Expander treatments did not increase the indigestible residue of
protein or individual amino acids. Thus, the risk that expander treatment thereby reduces
digestibility of protein or amino acids seems to be slight in practice. Consequently, the
treatments seemed to shift site of protein and amino acid digestion from the rumen to the
intestine. The observed values for EPD in expander-treated samples were low and need to be
verified in additional experiments. Expander processing at temperatures above 130±1358C is
probably unrealistic under commercial conditions.
Acknowledgements
The author gratefully acknowledges the staff at Eiker Mùlle Inc., Hokksund, Norway,
for production of experimental feedstuff samples, O.M. Harstad and H. Volden for taking
174
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
part in the planning of the experiment, K. Hove for surgery of animals, M. Bratberg, M.
Henne and R. évstegaÊrd for assistance in nylon bag experiments and care-taking of
animals, L.T. Mydland and W. Eckhardt for help with the amino acid analysis, and,
finally, N.P. Kjos and M.A. McNiven for critical review of the manuscript. The research
was financed by the Norwegian Research Council, Statkorn AS, Denofa AS, Felleskjùpet
FoÃrutvikling, Stormùllen AS, Norkorn and the Department of Animal Science, NLH.
References
AOAC, 1990. Official Methods of Analysis, 15th edn. Association of Official Analytical Chemists, Washington,
DC.
Broderick, G.A., Wallace, R.J., érskov, E.R., 1991. Control of rate and extent of protein degradation. In: Tsuda,
T., Sasaki, Y., Kawashima, R. (Eds.), Physiological Aspects of Digestion and Metabolism in Ruminants.
Academic Press, San Diego, pp. 541±592.
Crooker, B.A., Clark, J.H., Shanks, R.D., Hatfield, E.E., 1986. Effects of ruminal exposure on the amino acid
profile of heated and formaldehyde-treated soybean meal. J. Dairy Sci. 69, 2648±2657.
Crooker, B.A., Clark, J.H., Shanks, R.D., Fahey Jr., C., 1987. Effects of ruminal exposure on the amino acid
profile of feeds. Can. J. Anim. Sci. 67, 1143±1148.
Dworschak, E., 1980. Nonenzyme browning and its effect on protein. Crit. Rev. Food Sci. Nutr. 13, 1±40.
European Communities (EEC), 1998. Commission directive 98/64/EC Part A. Determination of amino acids.
Official J. Eur. Communities, OJ L 257, pp. 14±23.
Erasmus, L.J., Botha, P.M., Cruywagen, C.W., Meissner, H.H., 1994. Amino acid profile and intestinal
digestibility in dairy cows of rumen-undegraded protein from various feedstuffs. J. Dairy Sci. 77, 541±551.
Hvelplund, 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. Section A
± Anim. Sci. 42, 34±39.
Kristensen, M.B., Weisbjerg, M.R., Flye, J.C., Hvelplund, T., 1996. Aminosyretabel. Indhold af aminosyrer
AATmetionin and AATlysin i fodermidler til kvñg (Amino acid table. Contents of amino acids AATmethionine
and AATlysine in feedstuffs for ruminants). Landbrugets RaÊdgivningscenter, Denmark, Report No. 60, 40 pp.
Lund, P., 1997. Varmebehandling av kraftfoder til kvñg - Effekt paÊ omsñtning af protein, individuelle
aminosyrer og stivelse (Heat treatment of concentrated feedstuffs for cattle ± effects on utilisation of protein,
individual amino acids and starch), M.Sc. Thesis. The Royal Veterinary and Agricultural University of
Denmark, 146 pp.
Madsen, J., Hvelplund, T., Weisbjerg, M.R., Bertilsson, J., Olsson, I., SpoÈrndly, R., Harstad, O.M., Volden, H.,
Tuori, M., Varvikko, T., Huhtanen, P., Olafsson, B.L., 1995. The AAT/PBV protein evaluation system for
ruminants, A revision. Norwegian J. Agric. Sci. (Suppl. No. 19), 33 pp.
Mason, V.C., Bech-Andersen, S., Rudemo, M., 1980. Hydrolysate preparation for amino acid determination in
feed constituents 8. Studies of oxidation conditions for streamline procedures. Z. Tierphysiol. Tierernaehr.
Futtermittelk. 43, 146±164.
Mauron, J., 1990. Influence of processing on protein quality. J. Nutr. Sci. Vitaminol. 36, 57±69.
McCleary, B.V., Solah, V., Gibson, T.S., 1994. Measurement of total starch in cereal flours and products. J.
Cereal Sci. 20, 51±58.
McNiven, M.A., Hamilton, R.M.G., Robinson, P.H., de Leeuw, J.W., 1994. Effect of grain roasting on the
nutritional quality of common cereal grains for ruminants and non-ruminants. Anim. Feed Sci. Technol. 47,
31±40.
McNiven, M.A., Hvelplund, T., Weisbjerg, M.R., 1995. Influence of roasting or sodium hydroxide treatment of
barley on digestion in lactating cows. J. Dairy Sci. 78, 1106±1115.
Mir, Z., MacLeod, G.K., Buchanan-Smith, J.G., Grieve, D.G., Grovum, W.L., 1984. Methods for protecting
soybean and canola proteins from degradation in the rumen. Can. J. Anim. Sci. 64, 853±865.
Nocek, J.E., 1988. In situ and other methods to estimate ruminal protein and energy digestibility: a review. J.
Dairy Sci. 71, 2051±2069.
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
175
O'Mara, F.P., Murphy, J.J., Rath, M., 1997. The amino acid composition of protein feedstuffs before and after
ruminal incubation and after subsequent passage through the intestines of dairy cows. J. Anim. Sci. 75,
1941±1949.
Prestlùkken, E., 1999. In situ ruminal degradation and intestinal digestibility of dry matter and protein in
expanded feedstuffs. Anim. Feed Sci. Technol. 77, 1±23.
Rulquin, H., VeÁriteÁ, R., 1993. Amino acid nutrition of dairy cows: production effects and animal requirements.
In: Garnsworthy, P.C., Cole, D.J.A. (Eds.), Recent Advances in Animal Nutrition. Nottingham University
Press, UK, pp. 55±77.
Romagnolo, D., Polan, C.E., Barbeau, W.E., 1994. Electrophoretic analysis of ruminal degradability of corn
proteins. J. Dairy Sci. 77, 1093±1099.
Rudemo, M., Bech-Andersen, S., Mason, V.C., 1980. Hydrolysate preparation for amino acid determinations in
feed constituents 5. The influence of hydrolysis time on amino acid recovery. Z. Tierphysiol. Tierernaehr. u.
Futtermittelkde 43, 27±34.
SAS, 1990. Statistical Analysis System User's Guide, vols. 1 and 2, Version 6, 4th edn. SAS Institute Inc., Cary,
USA
Satter, L.D., 1986. Protein supply from undegraded dietary protein. J. Dairy Sci. 69, 2734±2749.
Schwab, C.G., 1995. Protected proteins and amino acids for ruminants. In: Wallace, R.J., Chesson, A. (Eds.),
Biotechnology in Animal Feeds and Animal Feeding. VCH Verlagsgesellschaft mbH, Weinheim, pp. 115±
141.
Shinnick, F.L., Longacre, M.J., Ink, S.L., Marlett, J.A., 1988. Oat fiber: composition versus physiological
function in rats. J. Nutr. 118, 144±151.
Susmel, P., Stefano, B., Mills, C.R., Candido, M., 1989. Change in amino acid composition of different protein
sources after rumen incubation. Anim. Prod. 49, 375±383.
van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fiber, neutral detergent fiber, and
nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583±3597.
van Straalen, W.M., Odinga, J.J., Mostert, W., 1997. Digestion of feed amino acids in the rumen and small
intestine of dairy cows measured with nylon-bag techniques. Br. J. Nutr. 77, 83±97.
Varvikko, T., Lindberg, J.E., Setala, J., Syrjala-Qvist, L., 1983. The effect of formaldehyde treatment of soyabean meal and rapeseed meal on the amino acid profiles and acid-pepsin solubility of rumen undegraded
protein. J. Agric. Sci. (Camb.) 101, 603±612.
Varvikko, T., 1986. Microbially corrected amino acid composition of rumen-undegraded feed protein and amino
acid degradability in the rumen of feeds enclosed in nylon bags. Br. J. Nutr. 56, 131±140.
Volden, H., Harstad, O.M., 1995. Effect of rumen incubation on the true indigestibility of feed protein in the
digestive tract determined by nylon bag techniques. Acta Agric. Scand. Section A ± Anim. Sci. 45, 106±115.
Voragen, A.G.J., Gruppen, H., Marsman, G.J.P., Mul, A.J., 1995. Effects of some manufacturing technologies on
chemical, physical and nutritional properties of feed. In: Garnsworthy, P.C., Cole, D.J.A. (Eds.), Recent
Advances in Animal Nutrition. Nottingham University Press, UK, pp. 93±126.
Vranjes, M.V., Wenk, C., 1995. The influence of extruded vs. untreated barley in the feed, with and without
dietary enzyme supplement on broiler performance. Anim. Feed Sci. Technol. 54, 21±32.
Weisbjerg, M.R., Hvelplund, T., Hellberg, S., Olsson, S., Sanne, S., 1996. Effective rumen degradability and
intestinal digestibility of individual amino acids in different concentrates determined in situ. Anim. Feed Sci.
Technol. 62, 179±188.
Zebrowska, T., Dlugolecka, Z., Pajak, J.J., Korczynski, W., 1997. Rumen degradability of concentrate protein,
amino acids and starch, and their digestibility in the small intestine of cows. J. Anim. Feed Sci. 6, 451±470.
érskov, E.R., McDonald, I., 1979. The estimation of protein degradability in the rumen from incubation
measurements weighted according to rate of passage. J. Agric. Sci. (Camb.) 92, 499±503.
82 (1999) 157±175
Ruminal degradability and intestinal digestibility
of protein and amino acids in barley and oats
expander-treated at various intensities
Egil Prestlùkken*
Department of Animal Science, Agricultural University of Norway, P.O. Box 5025, N-1432 AÊs, Norway
Received 11 December 1998; received in revised form 23 August 1999; accepted 8 September 1999
Abstract
The objectives of the experiment were to study effects of pelleting or expander treatment at
various intensities (mild, medium, hard or maximum) prior to pelleting at two temperatures in the
mixer-conditioner (60 and 758C) on ruminal degradation and intestinal digestibility of protein and
amino acids in barley and oats, using nylon bag methods. Temperatures achieved were 85±95, 100±
110 and 115±1258C at mild, medium and hard intensity, whereas maximum temperature achieved
was 1258C for barley and 1408C for oats. Thus, temperatures higher than 130±1358C appeared
unrealistic under commercial conditions.
Pelleting decreased ruminal degradation of protein, especially at high temperature in the mixerconditioner. Expander treatment decreased ruminal degradation of protein further and the lowest
effective protein degradability (EPD) achieved was 30% for barley and 29% for oats, both obtained
at maximum temperature in the expander and high temperature in the mixer-conditioner. These
values are low compared to previous results and need to be verified. No negative effects of
treatment on digestibility of protein were observed. This indicates that the treatments shifted site of
protein digestion from the rumen to the small intestine.
Expander treatment did not alter the contents of any individual amino acid either in barley or in
oats. Expander treatment reduced ruminal degradation of total amino acids to the same extent as
protein. The variation in ruminal degradation among amino acids was considerable. Thus, ruminal
degradation of protein cannot be used for determination of ruminal degradation of all individual
amino acids. Expander treatment did not increase the content of indigestible amino acids in barley
or oats, indicating that amino acids were not heat-damaged. # 1999 Elsevier Science B.V. All
rights reserved.
Keywords: Expander treatment; Nylon bags methods; Ruminants; Protein; Amino acids
*
Tel.: 47-64-94-80-57; fax: 47-64-94-79-60
E-mail address: ihfegp@ihf.nlh.no (E. Prestlùkken)
0377-8401/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 1 1 0 - 8
158
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
1. Introduction
Cereal grains, such as barley and oats, serve as an energy constituent in diets for
ruminants. Although the content is low, protein from these grains constitutes a significant
part of the dietary protein. However, the protein in barley and oats is extensively degraded
in the rumen, resulting in a rather low protein value. Nylon bag studies have shown that
expander treatment can protect protein in barley or oats against ruminal degradation
(Weisbjerg et al., 1996; Lund, 1997; Prestlùkken, 1999) and thereby increasing their
protein value by shifting the site of protein digestion from the rumen to the small
intestine.
The major parameters affecting nutrients in thermo-mechanical processes as the
expander treatment are temperature, moisture content, residence time and mechanical
shear (Voragen et al., 1995). Of them, only the influence of temperature during the
expansion process have been discussed earlier. Moreover, the effects of the expander
treatment have not been properly verified under commercial processing conditions. In
addition, steam is usually added in the mixer-conditioner located prior to the expander. To
what extent the addition of steam in the mixer-conditioner influence effects of the
expander process has not been studied previously.
Modern systems for protein evaluation in ruminants are moving in the direction of
predicting the absorption of individual amino acids from the small intestine (Rulquin and
VeÁriteÁ, 1993). Several studies (Susmel et al., 1989; Erasmus et al., 1994; O'Mara et al.,
1997; van Straalen et al., 1997) indicate that ruminal degradability of amino acids are not
similar to protein. Thus, knowledge to ruminal degradability of individual amino acids is
required when protein value is to be expressed on the basis of individual amino acids.
Excessive heat treatment may reduce the availability of certain amino acids. Lysine, in
particular, is susceptible to heat treatment through the reaction with reducing sugars and
the formation of Maillard products (Broderick et al., 1991). The determination of
intestinal digestibility of individual amino acids is, therefore, of special importance in
heat-treated feedstuffs.
The objectives of the experiment were (1) to study effects of pelleting or expander
treatment at various intensities prior to pelleting at two temperatures in the mixerconditioner on ruminal degradation and intestinal digestibility of protein, and (2) to study
effects of the treatments on ruminal degradation and intestinal digestibility of individual
amino acids in barley and oats.
2. Material and methods
2.1. Animals and diets
Three non-lactating dairy cows fitted with a flexible rumen cannulae (Bar Diamond,
Parma, ID, USA; 100 mm i.d.) and a simple T-type PVC cannulae (20 mm i.d.) located in
the duodenum 50±60 cm distal to pylorus (distal to the bile duct entrance), were used. At
06:00 and 15:00 hours, the cows were fed equal amounts of a standardised diet consisting
of grass hay (4 kg per day; 120 g CP, 60 g ash, 25 g fat, 600 g neutral detergent fibre
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
159
(NDF), g kgÿ1 DM) and a concentrate mixture (1.8 kg per day; 175 g CP, 55 g ash, 50 g
fat, 195 g NDF and 440 g starch plus sugar, g kgÿ1 DM). The cows were housed in tiestalls in a metabolism unit. Animal care was conducted according to laws and regulations
controlling experiments with live animals and the experiment was approved by the
Norwegian Animal Research Authority.
2.2. Experimental feedstuffs and treatments
The experimental feedstuffs were barley and oats. The feedstuffs were ground on a
horizontal shaft hammer mill and a sample was taken as an untreated control.
Experimental samples were produced at 60 and 758C in the mixer-conditioner. After the
mixer-conditioner, the feedstuffs were either subjected to traditional pelleting (75±808C)
or heat treatment with a Kahl OE 23 Expander (A. Kahl GmbH, Reinbek, Germany) at
various intensities (mild, medium, hard or maximum) prior to pelleting. In the samples
only pelleted, the expander acted as a screw feeder from the mixer-conditioner to the
pellet press. In the samples expander-treated prior to pelleting, treatment intensity was
regulated by adjusting the hydraulic pressure on the conical-shaped resistor in the outlet
of the expander, and at highest temperature stage in the mixer-conditioner, also through
addition of steam in the expander. Monitored treatment conditions are listed in Table 1.
2.3. Nylon bag measurements
Ruminal degradation and intestinal digestibility measurements were carried out using
nylon bag methods mainly as described by Madsen et al. (1995) and Prestlùkken (1999).
In the mobile bag experiment, original feed and residues after 16 h rumen incubation
were used. Except for 16 h residues for determination of intestinal digestibility, all
residues were milled for 1 min at frequency 80 with the MM2000 Mixer Mill (RETCH
GmbH & Co. KG, Haan, Germany).
2.4. Chemical analysis
The feedstuff samples were milled through a 1 mm screen before analysis. In all
samples, nitrogen (Kjeldahl-N) and dry matter were determined as described by AOAC
(1990). Within feedstuff, four samples were selected for additional chemical analysis.
Ash and fat (acid hydrolysis with petroleum ether extraction) were determined using
AOAC (1990) methods. Acid detergent fibre (ADF) and NDF were determined according
to van Soest et al. (1991) using the ANKOM220 Fiber Analyzer (ANKOM Technol.,
Fairport, NY). Starch was analysed according to the method of McCleary et al. (1994)
without correction for sugar. Amino acid analysis was performed according to Directive
98/64/EC (EEC, 1998), using acid hydrolysis. The amino acids were separated with ionexchange chromatography and quantified by UV-detection at 570 nm (440 nm for
proline) after post-column derivatisation with ninhydrin using the Biochrom 20 Amino
Acid Analyser (Pharmacia Biotech, Cambridge, UK). Tyrosine was analysed in oxidised
samples although oxidation reduces the content of tyrosine (Mason et al., 1980). Based on
unpublished results from our laboratory, tyrosine was increased by 10% to compensate
160
Treatmenta
Pelleted
Mild
Medium
Hard
Max
608C in mixer-conditioner
Barley, Sample No.
Capacity, expander (t, hÿ1)
Pressure, expander (bar)b
Temp., mixer (8C)
Temp., expander (8C)
H2OFeed (%)c
Oats, Sample No.
Capacity, expander (t, hÿ1)
Pressure, expander (bar)b
Temp., mixer (8C)
Temp., expander (8C)
H2OFeed (%)c
a
2
±
±
60
±
14.4
13
±
±
59
±
12.9
3
2.0
15
60
80
14.4
14
3.3
20
63
86
13.2
Pelleted
Mild
Medium
Hard
Max
9
3.0
25
76
102
16.9
20
2.9
33
75
108
15.5
10
3.0
33
75
114
16.9
21
2.8
45
74
126
15.5
11
3.0
33
75
125
16.9
22
2.7
50
75
140
15.5
758C in mixer-conditioner
4
2.0
25
60
95
14.4
15
2.7
42
62
105
13.2
5
2.0
42
62
116
14.5
16
2.1
46
59
120
12.9
6
2.0
42
62
125
14.5
17
2.1
50
60
135
13.0
7
±
±
74
±
15.4
18
±
±
74
±
14.0
8
2.8
10
72
90
16.4
19
2.6
10
76
92
15.5
Ordinary pelleting and expander treatment at mild, medium, hard or maximum treatment intensity.
Hydraulic pressure required to keep the cone in position.
c
Calculated water content in the feed samples based on 10.9 and 9.5% water in untreated barley and oats (Table 2), assuming a 0.7% increase in feed moisture
content for every 108C increase in temperature (A. Kahl, pers. commun.).
b
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Table 1
Processing conditions
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
161
for losses during oxidation. The content of serine, valine and isoleucine was increased by
6% for incomplete recovery after hydrolysis (Rudemo et al., 1980). Nitrogen in residues
after ruminal and intestinal incubation was determined according to Dumas method
(AOAC, 1990) using the EA 1108 Elemental Analyser (Fison Instruments S.p.A, Rudano
Milan, Italy).
2.5. Calculations and statistical analysis
Amino acid protein (AA-protein) was calculated using water-corrected molecular
weights. Ruminal degradation characteristics of CP were calculated as described by
érskov and McDonald (1979) using the PROC NLIN procedure in the statistical analysis
systems (SAS, 1990). Effective rumen degradability of protein (EPD) was calculated
assuming a rumen outflow rate of 8% hÿ1. Disappearance of amino acids from the rumen
nylon bag was calculated on animal basis as the mean of disappearance after 8, 16 and
24 h incubation time. Digestibility of rumen undegraded protein (dUDP) was calculated
according to Hvelplund et al. (1992). True indigestible residue of protein and amino acids
after intestinal incubation was calculated as a percentage of intact feed. Increase in the
moisture content of the feedstuffs during processing (H2OFeed) was calculated assuming
that 108C increase in temperature by the steam addition increased the water content with
0.7% units (A. Kahl GmbH, pers. commun.).
Analysis of variance (ANOVA) was performed with the GLM procedure in SAS (1990)
with effect of treatment and cow in the model. Means were separated with the PDIFF
statement. Means among treatments and among amino acids within treatment were
separated with the Duncan multiple range comparison statement. The significance level
was P < 0.05 unless stated otherwise.
3. Results and discussion
3.1. Effect of treatment on chemical composition and amino acids
In general, the chemical composition of the feedstuff samples was within expected
ranges (Table 2). The expander treatment did not appear to severely affect the
composition of feedstuffs except for a tendency to reduced NDF and ADF content. Heat
treatment increases the solubility of fibres (Shinnick et al., 1988; Vranjes and Wenk,
1995). Thus, the observed effect might be analytical rather than nutritional. Compared to
the Danish amino acid table (Kristensen et al., 1996), the content of amino acid nitrogen
in barley and oats was high (Table 3). However, the proportions of individual amino acids
were within the expected range in all samples. Furthermore, the expander treatment did
not influence the proportion of lysine or other essential amino acids relative to nonessential amino acids (Table 3). This indicates that amino acids, and lysin in particular,
were not heat damaged as might expected (Broderick et al., 1991; Schwab, 1995; Voragen
et al., 1995). However, the amino acid analysis may hydrolyse bonds that are not
hydrolysed by intestinal enzymes (Dworschak, 1980; Mauron, 1990). If this happens,
amino acid analysis will overestimated bioavailability of e.g., lysine.
162
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Table 2
Chemical composition (g kgÿ1 DM if not stated otherwise) and content of amino acid protein (AA-protein)a in
samples of barley and oats
Barley
Sample No.
b
Treatments
ÿ1
DM (g kg )
Ash
Fat
NDF
ADF
Starch
CP
AA-proteina
Oats
1
6
8
11
12
17
19
22
Untreated
62/125
72/90
75/125
Untreated
60/135
76/92
75/140
891
27
26
196
49
578
107
95
930
26
19
173
43
585
109
92
910
27
26
195
40
589
114
100
905
26
23
172
46
585
110
96
905
32
41
308
136
478
109
89
924
29
39
271
114
523
108
88
910
29
44
279
115
490
106
90
912
29
43
245
100
495
108
87
a
AA-protein calculated using water-corrected molecular weights.
Processing conditions: Untreated control and temperatures monitored in mixer-conditioner/expander (8C).
See also Table 1 for explanation.
b
Table 3
Amino acid N (g AAN 100 gÿ1 N), amino acid profile (g AA 100 gÿ1 AA) of barley and oatsa
Barley
Sample No.
b
Treatments
1
6
Control 62/125
Total AAN
83.3
Essential AA (EAA)
Arginine
5.4
Histidine
2.5 a
Isoleucine
3.9 ab
Leucine
7.2
Lysine
3.9 ab
Methionine
1.7
Phenylalanine 5.6
Threonine
3.7
Tyrosine
3.0
Valine
5.4
Sum EAA
42.3
Non essential AA (NEAA)
Alanine
4.3
Aspartic acid 6.2
Cystein
2.5
Glutamic acid 24.6 a
Glycine
4.2 b
Proline
11.3
Serine
4.6
Sum NEAA 57.7
a
Oats
78.5
8
12
c
17
22
75/125
SEM
Control 60/135
76/92
75/140
SEMc
84.7
82.2
1.58
80.3
82.5
79.9
1.25
5.4
2.5 ab
3.9 ab
7.2
3.8 ab
1.6
5.7
3.6
3.3
5.4
42.4
0.04
0.02
0.03
0.05
0.02
0.08
0.06
0.10
0.11
0.07
0.15
7.1
7.2
2.4 b
2.5 a
4.1 a
4.0 b
7.6
7.5
4.1
4.1
1.7
1.8
5.4
5.4
3.8
3.9
3.4
3.5
5.9 ab 5.8 abc
45.5
45.6
4.3
4.4
6.4
6.1
2.4
2.5
24.3 ab 24.2 ab
4.4 a
4.4 a
11.3
11.3
4.8
4.6
57.8
57.6
0.07
0.13
0.03
0.10
0.03
0.07
0.13
0.15
5.2
5.0
4.8
8.4
8.3
8.3
3.2 ab 3.1 b
3.3 a
21.5
21.2
21.3
5.4
5.4
5.2
5.5 c
6.3 ab 6.5 a
5.2
5.3
5.3
54.5
54.4
54.7
80.0
Different letters within grain type indicates statistical differences (p < 0.05).
See Tables 1 and 2 for explanation.
c
SEM: standard error mean.
b
19
72/90
5.4
5.4
2.5 ab 2.4 b
4.0 a
3.8 b
7.2
7.1
3.8 b
3.9 a
1.7
1.9
5.6
5.5
3.7
3.8
3.0
3.0
5.5
5.4
42.4
42.2
4.3
6.2
2.5
24.2 b
4.4 a
11.5
4.7
57.6
11
7.1
7.1
2.4 ab 2.5 ab
3.9 b 4.1 a
7.3
7.6
4.2
4.1
1.8
1.7
5.4
5.3
3.9
3.9
3.7
3.5
5.5 c
6.0 a
45.3
45.7
5.3
8.2
3.2 ab
20.9
5.4
6.0 bc
5.3
54.3
0.15
0.01
0.02
0.14
0.14
0.05
0.03
0.08
0.18
0.08
0.14
0.14
0.15
0.05
0.24
0.11
0.11
0.09
0.14
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
163
Fig. 1. Effective protein degradability (EPD) in untreated (Untr.), pelleted (Pell.) and different intensities of
expander treatment of barley at two temperatures in the mixer-conditioner. Different letters indicate statistical
differences between treatments (p < 0.05, MSE 3.9).
3.2. Effect of treatment on ruminal degradation of protein
It is well known that unfolding and denaturation of proteins at moderate heat can
increase digestibility of protein by making anti-nutritional proteins inactive. When heat is
added, bonds that stabilise the three-dimensional structure of proteins will break. If
hydrophobic groups are exposed, this will result in reduced solubility of proteins
(Voragen et al., 1995), and consequently reduced ruminal degradation of protein.
Consistent with Weisbjerg et al. (1996), Lund (1997) and Prestlùkken (1999), the
expander treatment, and even ordinary pelleting, reduced EPD markedly in barley (Fig. 1)
and oats (Fig. 2). Except for the ordinary pelleted samples, increased temperature in the
mixer-conditioner had no effect on EPD. In fact, in oats, EPD tended to be lower at the
low temperature in the mixer-conditioner (Fig. 2). This observation indicates that input of
mechanical energy is the main factor determining the effect of the expander treatment.
Thus, addition of thermal energy as steam probably plays a role only when input of
mechanical energy is low. Expander treatment of barley beyond mild intensity had only a
minor effect on EPD, whereas increased treatment intensity gradually decreased EPD in oats.
These findings are in agreement with Prestlùkken (1999), and have also been shown for
barley by Lund (1997). McNiven et al. (1995) and Prestlùkken (1999) have discussed
mechanisms for the different response of barley and oats to heat treatments. Differences in
morphologic configuration of the starch-protein matrix probably play an important role.
3.3. Effect of treatment on ruminal degradation of amino acids
Numerous publications exist on the effect of ruminal exposure on degradation of amino
acids in feedstuffs for ruminants (Varvikko et al., 1983; Mir et al., 1984; Varvikko, 1986;
164
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Fig. 2. Effective protein degradability (EPD) in untreated (Untr.), pelleted (Pell.) and different intensities of
expander treatment of oats at two temperatures in the mixer-conditioner. Different letters indicate statistical
differences between treatments (p < 0.05, MSE 4.4).
Crooker et al. (1986, 1987); Susmel et al., 1989; Erasmus et al., 1994; Weisbjerg et al., 1996;
Lund, 1997; O'Mara et al., 1997; van Straalen et al., 1997; Zebrowska et al., 1997) and
rapeseed meal, soybean meal and fish meal seem to be the most commonly studied. Of the
literature studied, only three references determined ruminal degradation of individual amino
acids of barley or oats (Weisbjerg et al., 1996; Lund, 1997; Zebrowska et al., 1997), and only
Weisbjerg et al. (1996) and Lund (1997) included heat-treated barley in the study.
Ruminal degradation of individual amino acids in the untreated and the expandertreated samples of barley and oats are shown in Figs. 3 and 4, respectively. In general, the
expander treatment reduced ruminal degradation of total amino acids to the same extent
as protein, indicating that ruminal degradation of protein can be used for the
determination of ruminal degradation of total amino acids. However, among the
individual amino acids there was considerable variation in ruminal degradation. Thus,
ruminal degradation of protein or total amino acids cannot be used for determination of
ruminal degradation of the individual amino acids. In the present experiment, arginine,
glutamic acid, cysteine and, to some extent, histidine were degraded to a relatively high
degree, whereas isoleucine, leucine, methionine, tyrosine, valine, and to some extent,
phenylalanine and alanine were degraded to a relatively low degree. In general, these
observations are in agreement with the literature referred earlier. However, considerable
variation among studies, and among feedstuffs within study, make it difficult to make
unambiguous conclusions on ruminal degradation of individual amino acids. Romagnolo
et al. (1994) suggested that hydrophobicity of proteins might be associated with reduced
degradability in the rumen. Although that study was on protein fractions, it is interesting
to observe that hydrophobic amino acids as leucine, isoleucine, phenylalanine,
methionine, valine, alanine and tyrosine, in the present study in general were degraded
to a lower extent than more hydrophilic amino acids as histidine, arginine, lysine,
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Fig. 3. Ruminal degradation of protein (N), amino acids (AA), essential AA (EAA), none essential AA (NEAA) and individual amino acids in untreated and expandertreated barley. Within sample, mean value for AA is shown as a horizontal line. Different letters indicate significant differences (p < 0.05) among AA within treatment.
MSE mean square error.
165
166
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Fig. 4. Ruminal degradation of protein (N), amino acids (AA), essential AA (EAA), none essential AA (NEAA) and individual amino acids in untreated and expandertreated oats. Within sample, mean value for AA is shown as a horizontal line. Different letters indicate significant differences (p < 0.05) among AA within treatment.
MSE mean square error.
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
167
cysteine, glutamic acid, glycine and serine (Figs. 3 and 4). Thus, their suggestion may be
of some relevance for individual amino acids as well.
As mentioned earlier, heat treatment may create Maillard products. If Maillard
products are formed, a reduced ruminal degradation of lysine might be expected. Lund
(1997), studying barley and seven other feedstuffs, concluded that the expander treatment
had no specific effect on ruminal degradation of lysine compared to total amino acids. In
the present study, the expander treatment tended to reduce ruminal degradation of lysine
relative to the mean for amino acids in barley (Fig. 3), whereas in oats, the opposite was
observed with a tendency to increased degradation of lysine compared to the mean of
amino acids (Fig. 4). Thus, treatment effects may vary among feedstuffs. However, the
expander treatment tended to reduce ruminal degradation of total essential amino acids
both in barley and in oats compared to total non-essential amino acids. If the decrease in
ruminal degradation is not followed by reduced intestinal digestibility of essential amino
acids, the expander treatment may improve the amino acid profile of escape protein.
3.4. Effect of treatment on intestinal digestion of protein
Hvelplund et al. (1992) proposed that feedstuffs contain a constant amount of
indigestible protein and that intestinal digestibility of rumen undegraded protein can be
calculated from nylon bag studies with intact feed. However, in barley, oats and several
other feedstuffs, the hypothesis of a constant indigestible protein residue does not seems
to be true (Volden and Harstad, 1995). Thus, digestibility of rumen undegraded protein
should be calculated on the basis of residues pre-incubated in the rumen (Madsen et al.,
1995). In the present experiment, indigestible protein was measured on intact feed and on
residues pre-incubated in the rumen for 16 h. In agreement with Volden and Harstad
(1995) and Prestlùkken (1999), rumen pre-incubation reduced indigestible protein,
especially in barley (Table 4). Furthermore, for intact barley, the content of indigestible
protein decreased in all expander-treated samples compared to the untreated. Since the
indigestible content of protein in the untreated sample was in agreement with that
determined by Volden and Harstad (1995), a positive effect of treatment on digestibility
of protein in intact barley cannot be excluded. However, this was not confirmed in the
study of Prestlùkken (1999). In oats, there was a tendency for treatment intensity to
increase the content of indigestible protein. Prestlùkken (1999) also observed this. The
increase was, however, marginal even at the highest treatment intensity. In fact, due to the
considerable reduction in ruminal degradation of protein, the expander treatment
increased digestibility of rumen undegraded protein, especially in oats (Table 4).
Therefore, as described by Satter (1986), the expander treatment seems to maximise the
amount of protein that can escape rumen degradation and still be digested in the intestine.
However, as shown by McNiven et al. (1994), with oats roasted at 1688C, the risk for
reducing digestibility of protein by heat treatment cannot be ignored.
3.5. Effect of treatment on intestinal digestion of amino acids
Although the mobile nylon bag experiment indicates that the expander treatment does
not decrease intestinal digestibility of protein (Table 4), severe heat treatment may have
168
Treatmentsc
Untr.
Pell.
Mild
Medium
Hard
Max
Pell.
608C in mixer-conditioner
Barley, No.
IF
IF16
dUDP
Oats, No.
IF
IF16
dUDP
a
1
6.07
1.73
95.8
12
2.42
1.88
87.8
a
b
b
cd
e
2
3.35
1.97
96.1
13
2.92
1.83
90.1
d
ab
ab
d
d
3
3.28
1.81
97.2
14
2.91
1.93
95.9
d
a
ab
cd
ab
4
4.52
2.08
96.8
15
2.87
2.07
96.9
Mild
Hard
9
4.10
2.07
97.0
20
3.70
2.01
96.7
10
4.93
2.29
96.5
21
3.40
2.32
96.5
MSEd
Max
758C in mixer-conditioner
bcd
ab
ab
abcd
a
5
3.92
2.22
96.6
16
3.12
2.18
96.8
cd
ab
ab
abc
a
6
4.31
1.98
97.2
17
2.98
2.29
96.7
bcd
a
ab
ab
a
7
4.72
1.92
96.5
18
3.14
1.87
93.8
abcd
ab
ab
d
c
8
4.15
2.07
96.7
19
2.79
1.96
95.4
Estimated according to Hvelplund et al. (1992) using indigestible residues after 16 h rumen pre-incubation.
Different letters within row indicates statistical differences (p < 0.05).
c
See Table 1 for explanation.
d
MSE: mean square error.
b
Medium
bcd
ab
ab
cd
b
bcd
ab
a
bcd
a
abc
ab
ab
a
a
11
5.47
2.08
97.0
22
3.79
2.18
96.8
ab
a
0.59
0.11
0.38
a
abc
a
0.30
0.03
0.30
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Table 4
Indigestible protein in intact feed (IF) and residues after 16 h rumen pre-incubation (IF16). Values in % of intact feed. Digestibility (%) of rumen undegraded proteina,b
(dUDP)
169
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
Table 5
Indigestible protein and amino acids (AA) measured in residues after 16 h rumen pre-incubation. Values in % of
intact feeda
Barley
Sample No.
b
Treatments
1
Oats
6
8
Control 62/125 72/90
Protein
2.28
Amino acids
1.72
Essential AA (EAA)
Arginine
1.50
Histidine
1.59
Isoleucine
1.83
Leucine
1.83
Lysine
2.03
Methionine
1.65
Phenylalanine 1.70
Threonine
2.27
Tyrosine
1.87
Valine
1.98
Sum EAA
1.78
Non essential AA (NEAA)
Alanin
2.69
Aspartic acid 2.69
Cystein
2.01
Glutamic acid 0.75
Glysin
3.03
Prolin
1.14
Serin
2.09
Sum NEAA
1.65
11
12
17
19
22
75/125 SEM
Control
60/135
76/92
75/140 SEMc
c
2.04
1.75
2.08
1.73
2.16
1.71
0.08
0.06
2.07 b
1.47 bc
2.42 a
1.57 ab
2.10 b
1.32 c
2.42 a
1.66 a
0.10
0.05
1.54
1.67
1.84
1.86
1.90
1.65
1.72
2.38
1.64
2.05
1.77
1.64
1.65
1.84
1.88
2.09
1.51
1.73
2.16
1.84
1.88
1.81
1.53
1.62
1.92
1.81
2.03
1.67
1.67
2.15
1.74
1.88
1.76
0.06
0.05
0.07
0.07
0.09
0.11
0.06
0.12
0.06
0.09
0.07
0.84
1.66
1.32
1.65
1.70
1.56
1.28
1.68
1.26
1.54
1.36
ab
bc
0.91
1.87
1.65
1.75
1.69
1.40
1.53
1.53
1.74
1.70
1.43
a
ab
0.73
1.60
1.26
1.54
1.52
1.33
1.32
1.50
1.30
1.49
1.22
b
c
1.05
1.92
1.74
1.78
1.86
1.57
1.69
1.88
1.58
1.80
1.52
a
a
0.06
0.07
0.11
0.06
0.09
0.04
0.08
0.10
0.17
0.07
0.05
2.80
2.78
1.83
0.82
3.04
1.15
2.18
1.71
2.72
2.53
1.95
0.80
2.88
1.12
2.19
1.65
2.77
2.60
1.91
0.77
3.00
1.11
2.08
1.66
0.09
0.10
0.07
0.03
0.09
0.04
0.08
0.06
1.93
1.51
1.55
0.86
2.40
1.99
2.06
1.62
bc
b
ab
ab
a
a
ab
2.29
1.70
1.96
0.97
2.58
1.95
1.90
1.73
ab
a
a
a
a
ab
ab
2.03
1.39
1.57
0.78
2.26
1.44
1.50
1.43
c
b
b
b
b
b
b
2.26
1.78
2.07
1.07
2.61
2.11
1.82
1.80
a
a
a
a
a
ab
a
0.12
0.07
0.10
0.04
0.07
0.12
0.13
0.05
ab
bc
bc
ab
ab
a
b
ab
ab
ab
ab
a
ab
b
ab
b
b
c
c
b
b
b
b
b
a
a
a
a
a
a
a
a
a
Different letters within grain type indicates statistical differences (p < 0.05).
See Tables 1 and 2 for explanation.
c
SEM: standard error mean.
b
specific effects on certain amino acids (Broderick et al., 1991; Schwab, 1995; Voragen et
al., 1995). In agreement with Lund (1997), the results presented do not indicate that heat
treatment with an expander decreased the content of digestible lysine or any other amino
acid. However, the indigestible residues among amino acids varied considerably and
among the essential amino acids, lysine was one with a relatively high indigestible
residue (Table 5). Consequently, digestibility of lysine probably was low compared to
most other amino acids. A relative low digestibility of lysine was also observed by
Weisbjerg et al. (1996), studying 15 feedstuffs. However, as shown in Table 5,
indigestible residues were in general low. Thus, in practice, digestibility of dietary amino
acids was high both in untreated and treated barley and oats.
3.6. Amino acid profiles of ruminal and intestinal residues
Intestinal incubation markedly reduced the content of amino acids nitrogen both in
untreated and expander-treated barley (Table 6) and oats (Table 7). Reduced
170
Table 6
Amino acid N (g AAN 100 gÿ1 N), amino acid profile (g AA 100 gÿ1 AA) of intact feed (IF), residues after washing in machine (W), residues after 16 h rumen
incubation (R) and residues after intestinal incubation of 16 h rumen residues (I) in untreated and expander-treated barleya
Untreated barley
IF
Aamino acid N
83.6 a
Essential AA (EAA)
Arginine
5.4 a
Histidine
2.5 a
Isoleucine
4.0 c
Leucine
7.3 bc
Lysine
3.9 bc
Methionine
1.8
Phenylalanine
5.7 b
Threonine
3.7 b
Tyrosine
3.0 abc
Valine
5.4 b
Sum EAA
42.6 b
Non essential AA (NEAA)
Alanine
4.2 b
Aspartic acid
6.0 b
Cysteine
2.5 b
Glutamic acid
24.6 b
Glycine
4.2 b
Proline
11.2 b
Serine
4.6 b
Sum NEAA
57.4 b
Untreated vs. expanded
Expander-treated barley
R
I
IF
W
R
I
81.6 a
78.2 a
62.9 b
78.8 a
79.8 a
81.7 a
68.0 b
5.2
2.4
4.0
7.1
3.6
1.7
5.7
3.5
2.9
5.3
41.4
4.5
2.2
4.8
7.6
4.0
1.8
6.1
3.7
3.5
5.4
43.5
4.9
2.4
4.5
8.2
4.9
1.8
5.9
5.1
3.3
6.5
47.5
5.4
2.5
4.0
7.3
3.8
1.8
5.6
3.7
3.0
5.5
42.6
5.3
2.5
4.1
7.1
3.9
1.8
5.6
3.7
3.4
5.6
42.9
5.3
2.5
4.3
7.9
3.8
1.9
5.6
3.7
3.6
5.9
44.5
4.9
2.5
4.4
8.1
4.4
1.8
5.8
5.1
3.3
6.6
47.0
W
a
a
c
c
c
b
b
bc
b
c
4.1 b
5.5 c
2.2 c
25.8 a
4.1 b
12.5 a
4.5 bc
58.6 a
c
b
a
b
b
a
b
a
b
b
4.4 b
6.4 b
1.7 d
24.7 b
3.6 c
11.4 b
4.3 bc
56.4 b
b
a
b
a
a
ab
a
ab
a
a
7.0 a
10.1 a
2.9 a
11.2 c
7.7 a
7.7 c
5.9 a
52.5 c
a
b
b
b
b
b
c
c
4.2 c
6.2 b
2.4 b
24.2 a
4.3 b
11.4 a
4.7 b
57.4 a
a
b
b
b
b
ab
bc
c
4.4 bc
5.6 c
2.3 b
23.9 ab
4.3 b
11.7 a
4.7 b
57.2 a
Contrasts
a
a
a
b
b
a
b
b
4.6 b
6.4 b
2.2 c
22.9 b
4.1 b
10.5 b
4.8 b
55.5 b
b
a
a
a
a
ab
a
a
7.0 a
10.1 a
2.7 a
11.7 c
7.8 a
7.7 c
6.1 a
53.0 c
IF
W
R
I
2.46
n.s.
n.s.
n.s.
n.s.
0.05
0.06
0.05
0.11
0.14
0.09
0.09
0.10
0.15
0.1 3
0.36
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.02
n.s.
0.01
0.01
0.01
0.01
n.s.
n.s.
n.s.
0.01
n.s.
n.s.
0.03
0.08
n.s.
n.s.
n.s.
n.s.
0.02
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.10
0.18
0.04
0.33
0.09
0.22
0.10
0.36
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.06
0.09
0.05
0.01
n.s.
0.02
n.s.
0.01
0.10
n.s.
0.01
0.01
0.01
0.01
0.01
0.08
n.s.
n.s.
0.01
n.s.
n.s.
n.s.
n.s.
n.s.
a
Different letters within treatment indicates statistical differences (p < 0.05). Significance level in contrasts P < 0.10. SEM: standard error mean; n.s.: indicates not
significant.
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
SEM
Table 7
Amino acid N (g AAN 100 gÿ1 N), amino acid profile (g AA 100 gÿ1 AA) of intact feed (IF), residues after washing in machine (W), residues after 16 h rumen
incubation (R) and residues after intestinal incubation of 16 h rumen residues (I) in untreated and expander-treated oatsa
Untreated oats
IF
Amino acid N
80.3 a
Essential AA (EAA)
Arginine
7.1 a
Histidine
2.4 bc
Isoleucine
4.1 b
Leucine
7.6 b
Lysine
4.1 b
Methionine
1.7 b
Phenylalanine
5.4 ab
Threonine
3.8 b
Tyrosine
3.4 a
Valine
5.9 c
Sum EAA
45.5 c
Non essential AA (NEAA)
Alanine
5.2 c
Aspartic acid
8.4 c
Cystein
3.2 a
Glutamic acid
21.5 a
Glycine
5.4 bc
Proline
5.5 b
Serine
5.2 b
Sum NEAA
54.5 a
Untreated vs. expanded
Expander-treated oats
R
I
IF
W
R
I
78.5 a
71.4 b
57.4 c
80.0 a
79.7 a
75.0 b
52.5 c
7.5
2.5
4.4
7.7
4.1
1.8
5.6
3.8
3.3
6.5
47.2
6.1
2.3
5.1
8.2
5.2
2.1
5.7
4.7
2.8
6.7
49.3
3.9
2.9
4.0
8.2
5.0
1.6
5.2
4.6
3.3
6.2
44.8
7.2
2.5
4.0
7.5
4.1
1.8
5.4
3.9
3.5
5.8
45.6
6.9
2.5
4.3
7.5
4.4
1.9
5.3
4.0
3.7
6.1
46.6
7.0
2.5
4.4
8.1
3.9
1.9
5.7
3.9
3.7
6.3
47.4
4.2
2.8
4.3
8.2
4.3
1.5
5.4
4.2
3.5
6.4
44.7
W
a
b
b
b
b
b
a
b
a
ab
b
5.1 c
8.0 c
2.5 b
21.6 a
5.2 c
5.5 b
5.0 b
52.8 b
b
c
a
a
a
a
a
a
b
a
a
6.3 b
9.8 a
1.9 c
16.7 b
5.6b
5.3 b
5.2 b
50.8 c
c
a
b
a
a
c
b
a
a
bc
c
7.0 a
9.1 b
3.4 a
12.4 c
8.7 a
7.6 a
7.0 a
55.2 a
a
b
b
b
b
b
b
bc
5.0 b
8.3 b
3.1 b
21.2 a
5.4 b
6.3 b
5.3 b
54.4 ab
a
b
ab
b
ab
b
ab
ab
5.2 b
8.2 b
3.0 b
20.4 a
5.3 b
6.1 b
5.3 b
53.4 bc
Contrasts
a
b
a
a
a
a
a
a
5.2 b
8.1 b
2.4 c
21.4 a
4.8 c
5.9 b
4.9 b
52.6 c
IF
W
R
I
2.10
n.s.
n.s.
0.08
0.09
a
c
0.26
0.08
0.10
0.16
0.17
0.04
0.08
0.19
0.13
0.19
0.38
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.08
0.04
n.s.
n.s.
n.s.
n.s.
0.01
0.02
0.01
n.s.
0.01
0.01
n.s.
0.01
0.01
0.03
0.01
n.s.
n.s.
0.04
n.s.
0.01
n.s.
0.06
0.09
n.s.
n.s.
n.s.
7.3 a
8.9 a
3.5 a
13.1 b
8.7 a
7.7 a
6.2 a
55.3 a
0.16
0.21
0.06
0.45
0.14
0.13
0.34
0.38
n.s.
n.s.
n.s.
n.s.
n.s.
0.01
n.s.
n.s.
n.s.
n.s.
0.01
n.s.
n.s.
0.02
n.s.
n.s.
0.01
0.01
0.01
0.01
0.01
0.01
n.s.
0.01
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
0.06
n.s.
b
a
a
a
c
b
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
SEM
a
Different letters within treatment indicates statistical differences (p < 0.05). Significance level in contrasts P < 0.10. SEM: standard error mean; n.s. indicate not
significant.
171
172
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
concentration of amino acids shows that digestibility of amino acids was high relative to
other nitrogen components. The amino acid profile after intestinal incubation differed to a
great extent from the profile of the intact feed as well as the residues after washing and
ruminal incubation. This observation confirm that digestibility varied among individual
amino acids. No major differences between the amino acid profile of residues after
intestinal incubation of untreated and expander-treated samples was found, supporting the
statement that expander treatment does not decrease digestibility of specific individual
amino acids.
To obtain true ruminal degradation of protein and amino acids, correction for microbial
contamination of nylon bag residues are recommend (Varvikko, 1986; Nocek, 1988;
Erasmus et al., 1994). Since amino acid profile of the rumen microbes differs from that of
barley and oats, severe microbial contamination would alter amino acid profile of the
rumen nylon bag residues. Thus, differences in amino acid profile between intact feed and
the rumen nylon bag residues might be explained by microbial contamination. However,
except for untreated oats, ruminal incubation did not increase the relative proportion of
e.g., lysine compared to intact feed. The concentration of lysine in protein from particle
adherent bacteria is almost twice the concentration found in protein from barley and oats.
Erasmus et al. (1994), washing the nylon bags for 10 min in a washing machine, found on
average only 3.9% microbial contamination in residues after 16 h rumen incubation for
12 feedstuffs. In the present study, the bags were washed for 10 min three times in a
washing machine. Thus, microbial contamination was probably not severe in the present
study either. Consequently, the difference in amino acid profile between intact feed and
nylon bag residues most likely was attributed to different ruminal degradation among
dietary amino acids. Moreover, the similarity in amino acid profile between intact feed
and residues after ruminal incubation was greater for expander-treated samples than for
untreated samples. This shows that dietary protein was protected from being degraded in
the rumen, confirming that increased rumen escape of dietary amino acids can be
expected when expander-treating barley and oats.
3.7. Processing conditions
In a previous experiment conducted at the A. Kahl pilot plant, the expander
temperatures ranged from 1308C at mild to 1708C at hard treatment intensity
(Prestlùkken, 1999). In the present experiment conducted at a commercial production
plant, the expander temperatures ranged from 85±95, 100±110 and 115±1258C at mild,
medium and hard treatment intensity, respectively (Table 1). The maximum temperature
achieved was 1258C for barley and 1408C for oats. However, increasing the temperature
above 1208C was dependent on the skill of the operator. In addition, to achieve these high
temperatures, the expander must be well maintained with low mechanical wear.
Therefore, in agreement with the experience of the Norwegian compound feed industry,
which has used expanders for many years, processing temperatures above 130±1358C
usually are unrealistic under commercial conditions.
With 108C as a start temperature, the addition of steam increased the temperature by
about 50 and 658C at low and high temperature in the mixer-conditioner, respectively.
This accounted for a 3.5 and 4.5% increase of water in the feed material. Thus, at the low
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
173
temperature in the mixer-conditioner, the water content was around 14.5% in barley and
13.0% in oats during the expander processing (Table 1). The increase in temperature
caused by the addition of steam in the expander was not monitored. Assuming that the
temperature increased from 75 to 958C, 1.4% water was added in the expander as steam.
Consequently, content of water in the feed material were around 2.5% units higher during
the expander treatment at the high compared to the low temperature in the mixerconditioner. Since the presence of water is important in hydrothermal reactions (Voragen
et al., 1995), increased water content was expected to increase the treatment effects of the
expander process. However, this seemed not to be the case in the present study. Moreover,
with respect to the parameters studied, shifting the administration of energy in the
expander process from mainly mechanical energy at low temperature in the mixerconditioner to more hydrothermal energy at high temperature in the mixer conditioner,
seemed not to be crucial for the treatment effects. The through-put of the expander
increased from around 2.0 tonnes hÿ1 at the low temperature to around 3.0 tonnes hÿ1 at
the high temperature in the mixer-conditioner, indicating that the water content of the
feed material is important for the through-put of the expander. However, increased
through-put resulted in decreased residence time, which again affects time dependent
reactions. Thus, the effects caused by reduced residence time may confound the expected
increase in treatment effects caused by addition of water. Nevertheless, the results
confirm that expander treatment is an excellent method to alter the site and extent of
digestion of protein and amino acids in ruminants. It must, however, be emphasised that
the values observed for EPD at the medium, hard and maximum treatment intensities are
lower than previous results (Prestlùkken, 1999). The values need to be verified in
additional experiments before implementing the results in commercial feed production.
4. Conclusions
Expander treatment and even ordinary pelleting reduced ruminal degradation of protein in
barley and oats considerably. In general, the treatments reduced ruminal degradation of total
amino acids to the same extent as protein, indicating that ruminal degradation of protein can
be used for the determination of total amino acid degradation. However, among the individual
amino acids there was considerable variation in ruminal degradation. Thus, ruminal
degradation of protein cannot be used for determination of ruminal degradation of all of the
individual amino acids. Expander treatments did not increase the indigestible residue of
protein or individual amino acids. Thus, the risk that expander treatment thereby reduces
digestibility of protein or amino acids seems to be slight in practice. Consequently, the
treatments seemed to shift site of protein and amino acid digestion from the rumen to the
intestine. The observed values for EPD in expander-treated samples were low and need to be
verified in additional experiments. Expander processing at temperatures above 130±1358C is
probably unrealistic under commercial conditions.
Acknowledgements
The author gratefully acknowledges the staff at Eiker Mùlle Inc., Hokksund, Norway,
for production of experimental feedstuff samples, O.M. Harstad and H. Volden for taking
174
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
part in the planning of the experiment, K. Hove for surgery of animals, M. Bratberg, M.
Henne and R. évstegaÊrd for assistance in nylon bag experiments and care-taking of
animals, L.T. Mydland and W. Eckhardt for help with the amino acid analysis, and,
finally, N.P. Kjos and M.A. McNiven for critical review of the manuscript. The research
was financed by the Norwegian Research Council, Statkorn AS, Denofa AS, Felleskjùpet
FoÃrutvikling, Stormùllen AS, Norkorn and the Department of Animal Science, NLH.
References
AOAC, 1990. Official Methods of Analysis, 15th edn. Association of Official Analytical Chemists, Washington,
DC.
Broderick, G.A., Wallace, R.J., érskov, E.R., 1991. Control of rate and extent of protein degradation. In: Tsuda,
T., Sasaki, Y., Kawashima, R. (Eds.), Physiological Aspects of Digestion and Metabolism in Ruminants.
Academic Press, San Diego, pp. 541±592.
Crooker, B.A., Clark, J.H., Shanks, R.D., Hatfield, E.E., 1986. Effects of ruminal exposure on the amino acid
profile of heated and formaldehyde-treated soybean meal. J. Dairy Sci. 69, 2648±2657.
Crooker, B.A., Clark, J.H., Shanks, R.D., Fahey Jr., C., 1987. Effects of ruminal exposure on the amino acid
profile of feeds. Can. J. Anim. Sci. 67, 1143±1148.
Dworschak, E., 1980. Nonenzyme browning and its effect on protein. Crit. Rev. Food Sci. Nutr. 13, 1±40.
European Communities (EEC), 1998. Commission directive 98/64/EC Part A. Determination of amino acids.
Official J. Eur. Communities, OJ L 257, pp. 14±23.
Erasmus, L.J., Botha, P.M., Cruywagen, C.W., Meissner, H.H., 1994. Amino acid profile and intestinal
digestibility in dairy cows of rumen-undegraded protein from various feedstuffs. J. Dairy Sci. 77, 541±551.
Hvelplund, 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. Section A
± Anim. Sci. 42, 34±39.
Kristensen, M.B., Weisbjerg, M.R., Flye, J.C., Hvelplund, T., 1996. Aminosyretabel. Indhold af aminosyrer
AATmetionin and AATlysin i fodermidler til kvñg (Amino acid table. Contents of amino acids AATmethionine
and AATlysine in feedstuffs for ruminants). Landbrugets RaÊdgivningscenter, Denmark, Report No. 60, 40 pp.
Lund, P., 1997. Varmebehandling av kraftfoder til kvñg - Effekt paÊ omsñtning af protein, individuelle
aminosyrer og stivelse (Heat treatment of concentrated feedstuffs for cattle ± effects on utilisation of protein,
individual amino acids and starch), M.Sc. Thesis. The Royal Veterinary and Agricultural University of
Denmark, 146 pp.
Madsen, J., Hvelplund, T., Weisbjerg, M.R., Bertilsson, J., Olsson, I., SpoÈrndly, R., Harstad, O.M., Volden, H.,
Tuori, M., Varvikko, T., Huhtanen, P., Olafsson, B.L., 1995. The AAT/PBV protein evaluation system for
ruminants, A revision. Norwegian J. Agric. Sci. (Suppl. No. 19), 33 pp.
Mason, V.C., Bech-Andersen, S., Rudemo, M., 1980. Hydrolysate preparation for amino acid determination in
feed constituents 8. Studies of oxidation conditions for streamline procedures. Z. Tierphysiol. Tierernaehr.
Futtermittelk. 43, 146±164.
Mauron, J., 1990. Influence of processing on protein quality. J. Nutr. Sci. Vitaminol. 36, 57±69.
McCleary, B.V., Solah, V., Gibson, T.S., 1994. Measurement of total starch in cereal flours and products. J.
Cereal Sci. 20, 51±58.
McNiven, M.A., Hamilton, R.M.G., Robinson, P.H., de Leeuw, J.W., 1994. Effect of grain roasting on the
nutritional quality of common cereal grains for ruminants and non-ruminants. Anim. Feed Sci. Technol. 47,
31±40.
McNiven, M.A., Hvelplund, T., Weisbjerg, M.R., 1995. Influence of roasting or sodium hydroxide treatment of
barley on digestion in lactating cows. J. Dairy Sci. 78, 1106±1115.
Mir, Z., MacLeod, G.K., Buchanan-Smith, J.G., Grieve, D.G., Grovum, W.L., 1984. Methods for protecting
soybean and canola proteins from degradation in the rumen. Can. J. Anim. Sci. 64, 853±865.
Nocek, J.E., 1988. In situ and other methods to estimate ruminal protein and energy digestibility: a review. J.
Dairy Sci. 71, 2051±2069.
E. Prestlùkken / Animal Feed Science and Technology 82 (1999) 157±175
175
O'Mara, F.P., Murphy, J.J., Rath, M., 1997. The amino acid composition of protein feedstuffs before and after
ruminal incubation and after subsequent passage through the intestines of dairy cows. J. Anim. Sci. 75,
1941±1949.
Prestlùkken, E., 1999. In situ ruminal degradation and intestinal digestibility of dry matter and protein in
expanded feedstuffs. Anim. Feed Sci. Technol. 77, 1±23.
Rulquin, H., VeÁriteÁ, R., 1993. Amino acid nutrition of dairy cows: production effects and animal requirements.
In: Garnsworthy, P.C., Cole, D.J.A. (Eds.), Recent Advances in Animal Nutrition. Nottingham University
Press, UK, pp. 55±77.
Romagnolo, D., Polan, C.E., Barbeau, W.E., 1994. Electrophoretic analysis of ruminal degradability of corn
proteins. J. Dairy Sci. 77, 1093±1099.
Rudemo, M., Bech-Andersen, S., Mason, V.C., 1980. Hydrolysate preparation for amino acid determinations in
feed constituents 5. The influence of hydrolysis time on amino acid recovery. Z. Tierphysiol. Tierernaehr. u.
Futtermittelkde 43, 27±34.
SAS, 1990. Statistical Analysis System User's Guide, vols. 1 and 2, Version 6, 4th edn. SAS Institute Inc., Cary,
USA
Satter, L.D., 1986. Protein supply from undegraded dietary protein. J. Dairy Sci. 69, 2734±2749.
Schwab, C.G., 1995. Protected proteins and amino acids for ruminants. In: Wallace, R.J., Chesson, A. (Eds.),
Biotechnology in Animal Feeds and Animal Feeding. VCH Verlagsgesellschaft mbH, Weinheim, pp. 115±
141.
Shinnick, F.L., Longacre, M.J., Ink, S.L., Marlett, J.A., 1988. Oat fiber: composition versus physiological
function in rats. J. Nutr. 118, 144±151.
Susmel, P., Stefano, B., Mills, C.R., Candido, M., 1989. Change in amino acid composition of different protein
sources after rumen incubation. Anim. Prod. 49, 375±383.
van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fiber, neutral detergent fiber, and
nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583±3597.
van Straalen, W.M., Odinga, J.J., Mostert, W., 1997. Digestion of feed amino acids in the rumen and small
intestine of dairy cows measured with nylon-bag techniques. Br. J. Nutr. 77, 83±97.
Varvikko, T., Lindberg, J.E., Setala, J., Syrjala-Qvist, L., 1983. The effect of formaldehyde treatment of soyabean meal and rapeseed meal on the amino acid profiles and acid-pepsin solubility of rumen undegraded
protein. J. Agric. Sci. (Camb.) 101, 603±612.
Varvikko, T., 1986. Microbially corrected amino acid composition of rumen-undegraded feed protein and amino
acid degradability in the rumen of feeds enclosed in nylon bags. Br. J. Nutr. 56, 131±140.
Volden, H., Harstad, O.M., 1995. Effect of rumen incubation on the true indigestibility of feed protein in the
digestive tract determined by nylon bag techniques. Acta Agric. Scand. Section A ± Anim. Sci. 45, 106±115.
Voragen, A.G.J., Gruppen, H., Marsman, G.J.P., Mul, A.J., 1995. Effects of some manufacturing technologies on
chemical, physical and nutritional properties of feed. In: Garnsworthy, P.C., Cole, D.J.A. (Eds.), Recent
Advances in Animal Nutrition. Nottingham University Press, UK, pp. 93±126.
Vranjes, M.V., Wenk, C., 1995. The influence of extruded vs. untreated barley in the feed, with and without
dietary enzyme supplement on broiler performance. Anim. Feed Sci. Technol. 54, 21±32.
Weisbjerg, M.R., Hvelplund, T., Hellberg, S., Olsson, S., Sanne, S., 1996. Effective rumen degradability and
intestinal digestibility of individual amino acids in different concentrates determined in situ. Anim. Feed Sci.
Technol. 62, 179±188.
Zebrowska, T., Dlugolecka, Z., Pajak, J.J., Korczynski, W., 1997. Rumen degradability of concentrate protein,
amino acids and starch, and their digestibility in the small intestine of cows. J. Anim. Feed Sci. 6, 451±470.
érskov, E.R., McDonald, I., 1979. The estimation of protein degradability in the rumen from incubation
measurements weighted according to rate of passage. J. Agric. Sci. (Camb.) 92, 499±503.