Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol85.Issue3-4.Jun2000:
Animal Feed Science and Technology
85 (2000) 195±214
Estimating ruminal crude protein degradation with
in situ and chemical fractionation procedures
S. Shannak, K.-H. SuÈdekum*, A. Susenbeth
Institut fuÈr TierernaÈhrung und Stoffwechselphysiologie, Christian-Albrechts-UniversitaÈt,
D-24098 Kiel, Germany
Received 28 September 1999; received in revised form 17 March 2000; accepted 24 March 2000
Abstract
The objective of this study was to utilize the fractionation of feed crude protein (CP) of the
Cornell net carbohydrate and protein system (CNCPS) as a basis for estimating undegraded dietary
protein (UDP) values of feedstuffs obtained from in situ trials. In addition, the experiments
comprised a comparison between in situ UDP values of feedstuffs and CP solubility estimated from
the protein dispersibility index. Eleven dairy compound feeds and 21 feedstuffs were inserted in
polyester bags and incubated in the rumen of three steers. Values for in situ UDP at assumed
ruminal passage rates of 2, 5, and 8% hÿ1, respectively, ranged from 63 to 616, 129 to 785, and 167
to 842 g kgÿ1 of CP. When ®sh meal data (n2) were excluded from the data set, multiple
regression equations that were based on concentrations of CP and cell wall, and on the A, B, and C
fractions of the CNCPS fractionation schedule, explained 87, 93, and 94%, respectively, of the
variation in UDP values at assumed ruminal passage rates of 2, 5, and 8% hÿ1. We conclude that in
situ UDP values, which serve as one key variable in many protein evaluation systems for dairy
cattle, may be reliably and accurately predicted from chemical fractionation of feed CP according to
the CNCPS. The coef®cients of determination of estimating UDP values at assumed ruminal
passage rates of 2, 5, and 8% hÿ1, respectively, from the protein dispersibility index were only 0.30,
0.29, and 0.33. Hence, the protein dispersibility index was not suitable as a predictor of UDP values
for the feedstuffs used in the present study. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Rumen; Protein degradation; Methods; Compound feeds; Feedstuffs
*
Corresponding author. Tel.: 49-431-880-2538; fax: 49-431-880-1528.
E-mail address: [email protected] (K.-H. SuÈdekum)
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 4 6 - 2
196
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
1. Introduction
A new system for the estimation of the protein value of feedstuffs for dairy cattle was
recently introduced in Germany (Gesellschaft fuÈr ErnaÈhrungsphysiologie, 1997). Key
variable in the system is the amount of total crude protein (CP) reaching the duodenum
(`nutzbares Rohprotein', nXP), which was estimated from in vivo trials on duodenally
cannulated dairy cows (Lebzien et al., 1996). The CP in the digesta at the beginning of
the small intestine consists of both the ruminally synthesized microbial CP and the feed
CP that has escaped ruminal degradation, i.e. undegraded dietary protein (UDP), besides a
varying proportion of endogenous CP. Although UDP values for a large number of feeds are
existing, there are considerable gaps in regard to reliable data, in particular for concentrate
ingredients. The German feed tables for ruminants (UniversitaÈt Hohenheim-Dokumentationsstelle, 1997) contain values that were obtained by three different approaches:
(a) In vivo from experiments using duodenally cannulated dairy cows; (b) in situ using
ruminally cannulated animals, and (c) for feedstuffs where no UDP values were available,
these values were estimated from feeds of the same feed class that were similar in
chemical composition with known values of UDP.
In vivo measurement of nutrient digestion requires that animals be surgically prepared
with cannulas in the rumen and abomasum or duodenum. In addition, suitable markers
are required for calculating ¯ow rate of digesta and for differentiation between microbial
and dietary nutrients ¯owing to the small intestine (Stern and Satter, 1982). Endogenous
contributions of nutrients are dif®cult to measure but they should be assessed to obtain
accurate values of digestion; however, these data are limited. In vivo measurement of
nutrient digestion is expensive, labour-intensive, time-consuming, and subject to error
associated with use of digesta ¯ow rate markers, microbial markers, and inherent animal
variation (Stern et al., 1997). In addition, the use of invasive surgical procedures for
nutritional research in general is becoming increasingly unacceptable to the public on
animal welfare grounds. Therefore, invasive techniques are not suitable for routine
estimation of UDP values on a wide range of feeds (Tamminga, 1979).
In situ procedures, often based on or similar to the basic studies conducted by érskov
and McDonald (1979), are well accepted in many countries for estimating the degree of
ruminal CP degradation of feedstuffs (Van der Koelen et al., 1992; Cottrill, 1993;
Broderick, 1994; Huntington and Givens, 1995; Michalet-Doreau and NozieÁre, 1998). In
situ measures can be used to obtain estimates of UDP values of feedstuffs within a
relatively short period of time but still this method requires cannulated animals and there
is a continuing need for simpler laboratory methods to estimate the protein value of feeds.
There is a revived intensive discussion about the accuracy and relevance of the
measurement of soluble CP fractions to predict the rumen CP degradation of feedstuffs.
The solvent used must simulate solubilization and degradation in the rumen as closely as
possible. The protein degradation in the rumen depends not only on the soluble and
insoluble proteins but also on the extent of the slowly digestible and indigestible proteins.
Many different procedures to determine soluble and insoluble nitrogen or CP in feedstuffs
have been published (e.g. Crawford et al., 1978; Crooker et al., 1978; Krishnamoorthy
et al., 1982), yet no single method has so far been accepted as being reliably accurate for
predicting the rumen CP degradation in feedstuffs.
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
197
The primary objective of this study, therefore, was to utilize the fractionation of feed
CP of the Cornell net carbohydrate and protein system (CNCPS; Russell et al., 1992;
Sniffen et al., 1992) as a basis of estimating UDP values of feedstuffs. Unlike the CNCPS,
our approach aimed at determining one single UDP value for each feedstuff from multiple
linear regression equations instead of estimating single UDP values for four different feed
CP fractions, which are then summed to provide a single UDP value. In addition, our
experiments comprised a comparison between in situ UDP values of feedstuffs and CP
solubility measured with the protein dispersibility index (PDIS; American Oil Chemists'
Society, 1989), one of the simpler, yet standardized and recently more intensively
discussed solubility methods to predict the rumen CP degradation of feedstuffs in
practice. A preliminary report including parts of the study has been published previously
(Shannak et al., 1999).
2. Materials and methods
2.1. Animals
Five 8-year old Angler Rotvieh steers, ranging in weight from 740 to 940 kg, and one
7-year old HinterwaÈlder steer weighing 660 kg were utilized in the experiment. Each of
the six steers was ®tted with a 10 cm i.d. ruminal cannula (Model 1C, Bar Diamond,
Parma, ID, USA) and housed indoors in individual tie stalls in a temperature controlled
room (188C) under continuous lighting. The steers received a mixed diet consisting of
two-thirds of long mixed grass-legume hay and one-third of mixed concentrates. The diet
was supplemented with a commercial mineral and vitamin mix. Animals were fed the
diets according to the Agricultural Research Council (1980) values for maintenance. The
daily allotment of feed was offered in two equal meals at 07:00 and 19:00 hours. The
steers had continuous access to water. Prior to the experiment, a period of 2 weeks was
allowed for dietary adaptation.
2.2. Feedstuffs
Eleven dairy compound feeds and 21 feedstuffs were selected which should re¯ect a
typical range of dairy compound feeds and protein-rich ingredients of commercial dairy
compounds in Central Europe. Thus, the ingredients listed below were also components
of the selected 11 dairy compound feeds (confer Table 1). Ingredients and compound
feeds were obtained from different commercial feed mills and feed suppliers. In addition,
three samples of one of the main forages used as a winter feed for dairy cows in major
parts of Europe, i.e. wilted grass silage, were used for in situ and laboratory evaluations of
ruminal CP degradation (alphabetical order; number of feeds per feed group in
parentheses):
commercial dairy compound feeds (11; for ingredient composition see Table 1);
fish meal (2);
grass silage (3);
maize gluten feed (2);
198
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
Table 1
Ingredient composition (g kgÿ1) of dairy compound feedsa
Wheat
Barley
Oats
Rye
Molasses
Dried beet pulp
Palm kernel meal
Palm kernel expeller
Maize gluten feed
Maize feed meal
Wheat gluten meal
Sun¯ower seed meal
Fish meal
Rapeseed meal
Rapeseed meal, protected
Rapeseed expeller
Soybean hulls
Soybean oil
Soybean meal
Soybean meal, protected
Grass meal, dehydrated
Citrus pulp
Mineral±vitamin mix
a
1
2
3
4
5
6
7
8
9
10
11
80
±
±
80
60
±
±
150
372
±
±
25
±
±
±
±
±
±
±
±
±
200
33
±
135
±
±
60
100
±
140
115
±
±
±
30
±
±
±
220
±
110
±
±
80
10
±
260
±
120
60
±
±
±
85
±
±
±
160
75
±
±
30
±
±
±
55
150
5
220
±
±
±
40
100
80
80
180
±
±
30
±
±
±
90
±
±
50
100
±
±
30
180
±
±
±
30
85
80
80
190
±
50
±
±
90
±
140
±
±
60
±
±
±
15
±
200
±
±
30
250
±
±
170
±
±
±
±
100
±
±
134
±
100
±
±
±
16
±
200
±
±
45
216
±
35
100
±
±
±
±
45
99
±
100
±
150
±
±
±
10
230
120
±
±
26
350
±
±
±
±
±
±
±
±
±
±
±
5
250
±
±
±
18
204
105
±
±
31
305
±
±
±
±
±
±
±
339
±
±
±
5
±
±
±
±
9
±
±
190
192
30
±
±
±
±
225
±
±
±
344
±
±
±
±
±
±
±
±
18
±
±
221
230
30
±
±
±
±
240
±
±
±
±
±
±
±
±
250
±
±
±
25
The sum of ingredient concentrations in each row may not equal 1000 g kgÿ1 due to rounding off numbers.
palm kernel meal (2);
rapeseed products (4; rapeseed meal, formaldehyde-treated rapeseed meal, rapeseed
expeller, and lignosulphonate-treated rapeseed expeller). The formaldehyde-treated
rapeseed meal has been previously studied in situ by SuÈdekum and Andree (1997);
soybean meal (4; two soybean meals, formaldehyde-treated soybean meal, and
lignosulphonate-treated soybean meal);
soybeans, crushed (3; untreated soybeans, dry-heat-treated soybeans and moist-heattreated soybeans);
sunflower seed meal (1).
The chemical composition of the 11 compound feeds and 21 feedstuffs is presented in
Table 2. Characteristics of rate and extent of ruminal degradation of CP and organic
matter of the feeds as related to degree of synchrony of ruminal CP and carbohydrate
degradation will be published elsewhere.
2.3. In situ procedure
Ruminal CP degradability was determined using polyester bags (R510, Ankom
Technology, Fairport, NY, USA) with a pore size of 5015 mm. Triplicate samples of
each feed were incubated in the rumen of three steers. About 1.3 g of feed ground to pass
199
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
Table 2
Chemical composition of 11 dairy compound feeds and 21 feedstuffs incubated in situ in the rumen of steersa
DM
Ash
CP
ADF
Starch
PNDF
(g kg±1) (g kg±1 DM) (g kg±1 DM) (g kg±1 DM) (g kg±1 DM) (g kg±1 DM)
Dairy compound feedb
1
2
3
4
5
6
7
8
9
10
11
889
880
879
902
906
899
889
918
915
917
918
79
73
79
81
82
68
71
64
62
60
61
160
182
230
218
220
187
217
217
194
205
212
189
262
165
188
199
177
177
134
185
151
113
140
110
200
139
142
137
137
199
179
280
310
406
554
423
491
410
364
370
323
361
267
212
Grass silage 1
Grass silage 2
Grass silage 3
361
639
550
103
178
157
167
178
157
166
178
171
NAc
NA
NA
597
554
464
Palm kernel meal 1
Palm kernel meal 2
Maize gluten feed 1
Maize gluten feed 2
Sun¯ower seed meal
Fish meal 1
Fish meal 2
901
890
887
889
911
923
923
53
53
67
69
77
172
202
172
173
210
247
334
679
766
469
475
91
99
312
NA
NA
1
2
209
149
4
NA
NA
823
854
375
404
458
202
574
Rapeseed meal
Rapeseed meal,
formaldehyde-treatedd
Rapeseed expeller
Rapeseed expeller,
lignosulphonate-treatede
Soybeans
Soybeans, dry-heat-treated
Soybeans, moist-heat-treated
Soybean meal 1
Soybean meal 2
Soybean meal,
lignosulphonate-treatedf
Soybean meal,
formaldehyde-treatedg
920
904
73
78
344
353
220
236
56
12
331
524
916
896
68
67
358
322
257
273
7
11
321
538
912
932
922
907
916
893
59
57
57
74
69
69
398
398
397
546
512
504
163
157
162
62
102
92
4
6
5
7
6
10
217
207
202
140
166
491
910
81
386
151
32
260
a
DM, dry matter; CP, crude protein; ADF, acid detergent ®bre; PNDF, neutral detergent ®bre determined by
manual ®ltration on paper according to the recommendations of Licitra et al. (1996).
b
For ingredient composition of dairy compound feeds see Table 1.
c
NA: not analysed.
d
Biopro®n1 R (Biopro®n sales of®ce, Bramsche, Germany).
e
RaPass1 (Borregaard LignoTech, Sarpsborg, Norway).
f
SoyPass1 (Borregaard LignoTech, Sarpsborg, Norway).
g
Biopro®n1 S (Biopro®n sales of®ce, Bramsche, Germany).
200
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
a 2 mm screen were placed in each bag, which was anchored with a 20 cm length of cable
binder. Prior to incubation, the bags were soaked in warm water (408C) for 10 min. On
Day 1 of incubation, the bags were clamped to an 800 g cylindrical plastic weight, which
was tied to an 80 cm long main line tied outside the ®stula. All bags were inserted into the
ventral sac of the rumen at 07:00 hours immediately before the morning feeding.
Incubation periods were 2, 4, 8, 16, 24, and 48 h. Immediately after removal from the
rumen, bags were immersed in ice-water to stop or minimize microbial activity and then
washed with cold water in a washing machine for 35 min. Zero time disappearance values
(0 h) were obtained by washing pre-soaked, unincubated bags in quadruplicate in a
similar fashion. Water-soluble material (WS) was estimated by washing duplicate
samples through a folded ®lter paper (No. 5951/2, Schleicher and Schuell, Dassel,
Germany). All washed bags and ®lter paper residues were freeze-dried. Water-insoluble
CP escaping in small particles (SP) from the bags during washing were estimated by
subtracting water-soluble CP from 0 h values. The single values obtained for CP
disappearance (DIi) were then corrected (c) for SP by the equation (Weisbjerg et al.,
1990):
1 ÿ DIi ÿ SP WS
:
CDIi DIi ÿ SP
1 ÿ SP WS
Degradation of CP (CDEG) was calculated using the equation of McDonald (1981):
CDEG a b 1 ÿ eÿc tÿL
for t > L;
where CDEG is the disappearance at time t corrected for SP, a an intercept representing
the proportion of CP solubilized at initiation of incubation (time 0; soluble fraction), b the
fraction of CP insoluble but degradable in the rumen, c the rate constant of disappearance
of fraction b, t the time of incubation, and L is the lag phase. The non-linear parameters a,
b, c, and L were estimated by an iterative least squares procedure (SAS, 1988). The
effective degradability (ED) of CP was calculated using the following equation
(McDonald, 1981):
ED a
bc ÿkL
e ;
ck
where k is the estimated rate of out¯ow from the rumen and a, b, c and L are the same
parameters as described earlier. The ED of CP was estimated as ED2, ED5 and ED8
assuming rumen solid out¯ow rates of 2, 5, and 8% hÿ1, which is representative for low,
medium, and high feeding amounts (Agricultural Research Council, 1984). Correspondingly, values for UDP2 (UDP5, UDP8) (g kgÿ1 of CP) were then calculated as 1000-ED2
(ED5, ED8).
2.4. Analytical procedures
2.4.1. General methods
The dry matter of the grass silages and the residues after ruminal exposure was
estimated by freeze-drying and subsequent oven-drying at 1058C overnight. The dry
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
201
matter of all other feeds was estimated by oven-drying at 1058C overnight. All feedstuffs
and freeze-dried residues after ruminal incubation were successively ground in mills with
3 and 1 mm screens and, for starch analysis, with a 0.2 mm screen. Nitrogen was
determined using the standard Kjeldahl procedure with Cu2 as a catalyst. Ash was
determined by ashing at 5508C overnight. The ADF was analysed according to the
Association of Of®cial Analytical Chemists (1990). Starch content was determined by
enzymatic hydrolysis of starch to glucose as described by Brandt et al. (1987). The PDIS
was analysed on all samples except the three grass silages as described by the American
Oil Chemists' Society (1989).
2.4.2. Fractionation of crude protein
The CP of all feedstuffs was partitioned into ®ve fractions (A, B1, B2, B3, and C;
Table 3) according to the CNCPS (Russell et al., 1992; Sniffen et al., 1992), using
standardisation and recommendations published by Licitra et al. (1996) except that aamylase (bacterial crude type XI-A from Bacillus subtilis; Sigma, St. Louis, MO) was
used on all feeds in the NDF procedure to facilitate ®ltration through the ®lter paper with
the exception of the three silage samples. As neutral detergent ®bre (NDF) values of the
feed samples that were determined within the CP fractionation schedule by manual
®ltration on paper according to the recommendations of Licitra et al. (1996) may deviate
from those obtained with the conventional NDF method, the cell-wall fraction obtained as
a residue on ®lter paper was named PNDF. All analyses of CP, CP fractions and PNDF
were carried out at least in duplicate.
2.5. Statistical methods
Linear and non-linear regression equations and r2 values for in situ UDP2, UDP5 and
UDP8 values versus PDIS values were determined by SAS (1988). Signi®cant
relationships were declared at p
85 (2000) 195±214
Estimating ruminal crude protein degradation with
in situ and chemical fractionation procedures
S. Shannak, K.-H. SuÈdekum*, A. Susenbeth
Institut fuÈr TierernaÈhrung und Stoffwechselphysiologie, Christian-Albrechts-UniversitaÈt,
D-24098 Kiel, Germany
Received 28 September 1999; received in revised form 17 March 2000; accepted 24 March 2000
Abstract
The objective of this study was to utilize the fractionation of feed crude protein (CP) of the
Cornell net carbohydrate and protein system (CNCPS) as a basis for estimating undegraded dietary
protein (UDP) values of feedstuffs obtained from in situ trials. In addition, the experiments
comprised a comparison between in situ UDP values of feedstuffs and CP solubility estimated from
the protein dispersibility index. Eleven dairy compound feeds and 21 feedstuffs were inserted in
polyester bags and incubated in the rumen of three steers. Values for in situ UDP at assumed
ruminal passage rates of 2, 5, and 8% hÿ1, respectively, ranged from 63 to 616, 129 to 785, and 167
to 842 g kgÿ1 of CP. When ®sh meal data (n2) were excluded from the data set, multiple
regression equations that were based on concentrations of CP and cell wall, and on the A, B, and C
fractions of the CNCPS fractionation schedule, explained 87, 93, and 94%, respectively, of the
variation in UDP values at assumed ruminal passage rates of 2, 5, and 8% hÿ1. We conclude that in
situ UDP values, which serve as one key variable in many protein evaluation systems for dairy
cattle, may be reliably and accurately predicted from chemical fractionation of feed CP according to
the CNCPS. The coef®cients of determination of estimating UDP values at assumed ruminal
passage rates of 2, 5, and 8% hÿ1, respectively, from the protein dispersibility index were only 0.30,
0.29, and 0.33. Hence, the protein dispersibility index was not suitable as a predictor of UDP values
for the feedstuffs used in the present study. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Rumen; Protein degradation; Methods; Compound feeds; Feedstuffs
*
Corresponding author. Tel.: 49-431-880-2538; fax: 49-431-880-1528.
E-mail address: [email protected] (K.-H. SuÈdekum)
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 4 6 - 2
196
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
1. Introduction
A new system for the estimation of the protein value of feedstuffs for dairy cattle was
recently introduced in Germany (Gesellschaft fuÈr ErnaÈhrungsphysiologie, 1997). Key
variable in the system is the amount of total crude protein (CP) reaching the duodenum
(`nutzbares Rohprotein', nXP), which was estimated from in vivo trials on duodenally
cannulated dairy cows (Lebzien et al., 1996). The CP in the digesta at the beginning of
the small intestine consists of both the ruminally synthesized microbial CP and the feed
CP that has escaped ruminal degradation, i.e. undegraded dietary protein (UDP), besides a
varying proportion of endogenous CP. Although UDP values for a large number of feeds are
existing, there are considerable gaps in regard to reliable data, in particular for concentrate
ingredients. The German feed tables for ruminants (UniversitaÈt Hohenheim-Dokumentationsstelle, 1997) contain values that were obtained by three different approaches:
(a) In vivo from experiments using duodenally cannulated dairy cows; (b) in situ using
ruminally cannulated animals, and (c) for feedstuffs where no UDP values were available,
these values were estimated from feeds of the same feed class that were similar in
chemical composition with known values of UDP.
In vivo measurement of nutrient digestion requires that animals be surgically prepared
with cannulas in the rumen and abomasum or duodenum. In addition, suitable markers
are required for calculating ¯ow rate of digesta and for differentiation between microbial
and dietary nutrients ¯owing to the small intestine (Stern and Satter, 1982). Endogenous
contributions of nutrients are dif®cult to measure but they should be assessed to obtain
accurate values of digestion; however, these data are limited. In vivo measurement of
nutrient digestion is expensive, labour-intensive, time-consuming, and subject to error
associated with use of digesta ¯ow rate markers, microbial markers, and inherent animal
variation (Stern et al., 1997). In addition, the use of invasive surgical procedures for
nutritional research in general is becoming increasingly unacceptable to the public on
animal welfare grounds. Therefore, invasive techniques are not suitable for routine
estimation of UDP values on a wide range of feeds (Tamminga, 1979).
In situ procedures, often based on or similar to the basic studies conducted by érskov
and McDonald (1979), are well accepted in many countries for estimating the degree of
ruminal CP degradation of feedstuffs (Van der Koelen et al., 1992; Cottrill, 1993;
Broderick, 1994; Huntington and Givens, 1995; Michalet-Doreau and NozieÁre, 1998). In
situ measures can be used to obtain estimates of UDP values of feedstuffs within a
relatively short period of time but still this method requires cannulated animals and there
is a continuing need for simpler laboratory methods to estimate the protein value of feeds.
There is a revived intensive discussion about the accuracy and relevance of the
measurement of soluble CP fractions to predict the rumen CP degradation of feedstuffs.
The solvent used must simulate solubilization and degradation in the rumen as closely as
possible. The protein degradation in the rumen depends not only on the soluble and
insoluble proteins but also on the extent of the slowly digestible and indigestible proteins.
Many different procedures to determine soluble and insoluble nitrogen or CP in feedstuffs
have been published (e.g. Crawford et al., 1978; Crooker et al., 1978; Krishnamoorthy
et al., 1982), yet no single method has so far been accepted as being reliably accurate for
predicting the rumen CP degradation in feedstuffs.
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
197
The primary objective of this study, therefore, was to utilize the fractionation of feed
CP of the Cornell net carbohydrate and protein system (CNCPS; Russell et al., 1992;
Sniffen et al., 1992) as a basis of estimating UDP values of feedstuffs. Unlike the CNCPS,
our approach aimed at determining one single UDP value for each feedstuff from multiple
linear regression equations instead of estimating single UDP values for four different feed
CP fractions, which are then summed to provide a single UDP value. In addition, our
experiments comprised a comparison between in situ UDP values of feedstuffs and CP
solubility measured with the protein dispersibility index (PDIS; American Oil Chemists'
Society, 1989), one of the simpler, yet standardized and recently more intensively
discussed solubility methods to predict the rumen CP degradation of feedstuffs in
practice. A preliminary report including parts of the study has been published previously
(Shannak et al., 1999).
2. Materials and methods
2.1. Animals
Five 8-year old Angler Rotvieh steers, ranging in weight from 740 to 940 kg, and one
7-year old HinterwaÈlder steer weighing 660 kg were utilized in the experiment. Each of
the six steers was ®tted with a 10 cm i.d. ruminal cannula (Model 1C, Bar Diamond,
Parma, ID, USA) and housed indoors in individual tie stalls in a temperature controlled
room (188C) under continuous lighting. The steers received a mixed diet consisting of
two-thirds of long mixed grass-legume hay and one-third of mixed concentrates. The diet
was supplemented with a commercial mineral and vitamin mix. Animals were fed the
diets according to the Agricultural Research Council (1980) values for maintenance. The
daily allotment of feed was offered in two equal meals at 07:00 and 19:00 hours. The
steers had continuous access to water. Prior to the experiment, a period of 2 weeks was
allowed for dietary adaptation.
2.2. Feedstuffs
Eleven dairy compound feeds and 21 feedstuffs were selected which should re¯ect a
typical range of dairy compound feeds and protein-rich ingredients of commercial dairy
compounds in Central Europe. Thus, the ingredients listed below were also components
of the selected 11 dairy compound feeds (confer Table 1). Ingredients and compound
feeds were obtained from different commercial feed mills and feed suppliers. In addition,
three samples of one of the main forages used as a winter feed for dairy cows in major
parts of Europe, i.e. wilted grass silage, were used for in situ and laboratory evaluations of
ruminal CP degradation (alphabetical order; number of feeds per feed group in
parentheses):
commercial dairy compound feeds (11; for ingredient composition see Table 1);
fish meal (2);
grass silage (3);
maize gluten feed (2);
198
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
Table 1
Ingredient composition (g kgÿ1) of dairy compound feedsa
Wheat
Barley
Oats
Rye
Molasses
Dried beet pulp
Palm kernel meal
Palm kernel expeller
Maize gluten feed
Maize feed meal
Wheat gluten meal
Sun¯ower seed meal
Fish meal
Rapeseed meal
Rapeseed meal, protected
Rapeseed expeller
Soybean hulls
Soybean oil
Soybean meal
Soybean meal, protected
Grass meal, dehydrated
Citrus pulp
Mineral±vitamin mix
a
1
2
3
4
5
6
7
8
9
10
11
80
±
±
80
60
±
±
150
372
±
±
25
±
±
±
±
±
±
±
±
±
200
33
±
135
±
±
60
100
±
140
115
±
±
±
30
±
±
±
220
±
110
±
±
80
10
±
260
±
120
60
±
±
±
85
±
±
±
160
75
±
±
30
±
±
±
55
150
5
220
±
±
±
40
100
80
80
180
±
±
30
±
±
±
90
±
±
50
100
±
±
30
180
±
±
±
30
85
80
80
190
±
50
±
±
90
±
140
±
±
60
±
±
±
15
±
200
±
±
30
250
±
±
170
±
±
±
±
100
±
±
134
±
100
±
±
±
16
±
200
±
±
45
216
±
35
100
±
±
±
±
45
99
±
100
±
150
±
±
±
10
230
120
±
±
26
350
±
±
±
±
±
±
±
±
±
±
±
5
250
±
±
±
18
204
105
±
±
31
305
±
±
±
±
±
±
±
339
±
±
±
5
±
±
±
±
9
±
±
190
192
30
±
±
±
±
225
±
±
±
344
±
±
±
±
±
±
±
±
18
±
±
221
230
30
±
±
±
±
240
±
±
±
±
±
±
±
±
250
±
±
±
25
The sum of ingredient concentrations in each row may not equal 1000 g kgÿ1 due to rounding off numbers.
palm kernel meal (2);
rapeseed products (4; rapeseed meal, formaldehyde-treated rapeseed meal, rapeseed
expeller, and lignosulphonate-treated rapeseed expeller). The formaldehyde-treated
rapeseed meal has been previously studied in situ by SuÈdekum and Andree (1997);
soybean meal (4; two soybean meals, formaldehyde-treated soybean meal, and
lignosulphonate-treated soybean meal);
soybeans, crushed (3; untreated soybeans, dry-heat-treated soybeans and moist-heattreated soybeans);
sunflower seed meal (1).
The chemical composition of the 11 compound feeds and 21 feedstuffs is presented in
Table 2. Characteristics of rate and extent of ruminal degradation of CP and organic
matter of the feeds as related to degree of synchrony of ruminal CP and carbohydrate
degradation will be published elsewhere.
2.3. In situ procedure
Ruminal CP degradability was determined using polyester bags (R510, Ankom
Technology, Fairport, NY, USA) with a pore size of 5015 mm. Triplicate samples of
each feed were incubated in the rumen of three steers. About 1.3 g of feed ground to pass
199
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
Table 2
Chemical composition of 11 dairy compound feeds and 21 feedstuffs incubated in situ in the rumen of steersa
DM
Ash
CP
ADF
Starch
PNDF
(g kg±1) (g kg±1 DM) (g kg±1 DM) (g kg±1 DM) (g kg±1 DM) (g kg±1 DM)
Dairy compound feedb
1
2
3
4
5
6
7
8
9
10
11
889
880
879
902
906
899
889
918
915
917
918
79
73
79
81
82
68
71
64
62
60
61
160
182
230
218
220
187
217
217
194
205
212
189
262
165
188
199
177
177
134
185
151
113
140
110
200
139
142
137
137
199
179
280
310
406
554
423
491
410
364
370
323
361
267
212
Grass silage 1
Grass silage 2
Grass silage 3
361
639
550
103
178
157
167
178
157
166
178
171
NAc
NA
NA
597
554
464
Palm kernel meal 1
Palm kernel meal 2
Maize gluten feed 1
Maize gluten feed 2
Sun¯ower seed meal
Fish meal 1
Fish meal 2
901
890
887
889
911
923
923
53
53
67
69
77
172
202
172
173
210
247
334
679
766
469
475
91
99
312
NA
NA
1
2
209
149
4
NA
NA
823
854
375
404
458
202
574
Rapeseed meal
Rapeseed meal,
formaldehyde-treatedd
Rapeseed expeller
Rapeseed expeller,
lignosulphonate-treatede
Soybeans
Soybeans, dry-heat-treated
Soybeans, moist-heat-treated
Soybean meal 1
Soybean meal 2
Soybean meal,
lignosulphonate-treatedf
Soybean meal,
formaldehyde-treatedg
920
904
73
78
344
353
220
236
56
12
331
524
916
896
68
67
358
322
257
273
7
11
321
538
912
932
922
907
916
893
59
57
57
74
69
69
398
398
397
546
512
504
163
157
162
62
102
92
4
6
5
7
6
10
217
207
202
140
166
491
910
81
386
151
32
260
a
DM, dry matter; CP, crude protein; ADF, acid detergent ®bre; PNDF, neutral detergent ®bre determined by
manual ®ltration on paper according to the recommendations of Licitra et al. (1996).
b
For ingredient composition of dairy compound feeds see Table 1.
c
NA: not analysed.
d
Biopro®n1 R (Biopro®n sales of®ce, Bramsche, Germany).
e
RaPass1 (Borregaard LignoTech, Sarpsborg, Norway).
f
SoyPass1 (Borregaard LignoTech, Sarpsborg, Norway).
g
Biopro®n1 S (Biopro®n sales of®ce, Bramsche, Germany).
200
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
a 2 mm screen were placed in each bag, which was anchored with a 20 cm length of cable
binder. Prior to incubation, the bags were soaked in warm water (408C) for 10 min. On
Day 1 of incubation, the bags were clamped to an 800 g cylindrical plastic weight, which
was tied to an 80 cm long main line tied outside the ®stula. All bags were inserted into the
ventral sac of the rumen at 07:00 hours immediately before the morning feeding.
Incubation periods were 2, 4, 8, 16, 24, and 48 h. Immediately after removal from the
rumen, bags were immersed in ice-water to stop or minimize microbial activity and then
washed with cold water in a washing machine for 35 min. Zero time disappearance values
(0 h) were obtained by washing pre-soaked, unincubated bags in quadruplicate in a
similar fashion. Water-soluble material (WS) was estimated by washing duplicate
samples through a folded ®lter paper (No. 5951/2, Schleicher and Schuell, Dassel,
Germany). All washed bags and ®lter paper residues were freeze-dried. Water-insoluble
CP escaping in small particles (SP) from the bags during washing were estimated by
subtracting water-soluble CP from 0 h values. The single values obtained for CP
disappearance (DIi) were then corrected (c) for SP by the equation (Weisbjerg et al.,
1990):
1 ÿ DIi ÿ SP WS
:
CDIi DIi ÿ SP
1 ÿ SP WS
Degradation of CP (CDEG) was calculated using the equation of McDonald (1981):
CDEG a b 1 ÿ eÿc tÿL
for t > L;
where CDEG is the disappearance at time t corrected for SP, a an intercept representing
the proportion of CP solubilized at initiation of incubation (time 0; soluble fraction), b the
fraction of CP insoluble but degradable in the rumen, c the rate constant of disappearance
of fraction b, t the time of incubation, and L is the lag phase. The non-linear parameters a,
b, c, and L were estimated by an iterative least squares procedure (SAS, 1988). The
effective degradability (ED) of CP was calculated using the following equation
(McDonald, 1981):
ED a
bc ÿkL
e ;
ck
where k is the estimated rate of out¯ow from the rumen and a, b, c and L are the same
parameters as described earlier. The ED of CP was estimated as ED2, ED5 and ED8
assuming rumen solid out¯ow rates of 2, 5, and 8% hÿ1, which is representative for low,
medium, and high feeding amounts (Agricultural Research Council, 1984). Correspondingly, values for UDP2 (UDP5, UDP8) (g kgÿ1 of CP) were then calculated as 1000-ED2
(ED5, ED8).
2.4. Analytical procedures
2.4.1. General methods
The dry matter of the grass silages and the residues after ruminal exposure was
estimated by freeze-drying and subsequent oven-drying at 1058C overnight. The dry
S. Shannak et al. / Animal Feed Science and Technology 85 (2000) 195±214
201
matter of all other feeds was estimated by oven-drying at 1058C overnight. All feedstuffs
and freeze-dried residues after ruminal incubation were successively ground in mills with
3 and 1 mm screens and, for starch analysis, with a 0.2 mm screen. Nitrogen was
determined using the standard Kjeldahl procedure with Cu2 as a catalyst. Ash was
determined by ashing at 5508C overnight. The ADF was analysed according to the
Association of Of®cial Analytical Chemists (1990). Starch content was determined by
enzymatic hydrolysis of starch to glucose as described by Brandt et al. (1987). The PDIS
was analysed on all samples except the three grass silages as described by the American
Oil Chemists' Society (1989).
2.4.2. Fractionation of crude protein
The CP of all feedstuffs was partitioned into ®ve fractions (A, B1, B2, B3, and C;
Table 3) according to the CNCPS (Russell et al., 1992; Sniffen et al., 1992), using
standardisation and recommendations published by Licitra et al. (1996) except that aamylase (bacterial crude type XI-A from Bacillus subtilis; Sigma, St. Louis, MO) was
used on all feeds in the NDF procedure to facilitate ®ltration through the ®lter paper with
the exception of the three silage samples. As neutral detergent ®bre (NDF) values of the
feed samples that were determined within the CP fractionation schedule by manual
®ltration on paper according to the recommendations of Licitra et al. (1996) may deviate
from those obtained with the conventional NDF method, the cell-wall fraction obtained as
a residue on ®lter paper was named PNDF. All analyses of CP, CP fractions and PNDF
were carried out at least in duplicate.
2.5. Statistical methods
Linear and non-linear regression equations and r2 values for in situ UDP2, UDP5 and
UDP8 values versus PDIS values were determined by SAS (1988). Signi®cant
relationships were declared at p