Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol87.Issue1-2.Sept2000:
Animal Feed Science and Technology
87 (2000) 71±83
Effect of dietary ®bre source on total tract
digestibility, caecum volatile fatty acids and
digestive transit time in the weaned piglet
J.P.B. Freirea,*, A.J.G. Guerreiroa, L.F. Cunhaa, A. Aumaitreb
a
Dpto. de Producao Agricola e Animal, Seccao de Producao Animal, Instituto Superior de Agronomia,
Tapada da Ajuda, 1349-017 Lisbon, Portugal
b
Unite Mixte de Recherches sur le Veau et le Porc, 35590 St. Gilles, France
Received 20 October 1999; received in revised form 25 April 2000; accepted 5 July 2000
Abstract
Effects of the use of 200 g of either wheat bran, sugar beet pulp, soya bean hulls or alfalfa meal
per kilogram diet on the digestive process of the weaned piglet were studied on
24 Duroc Landrace male piglets, weaned at 28 days of age. Piglets had an initial mean live
weight of 7.92(1.1) kg and were randomly distributed in six successive blocks of four animals.
The total tract apparent digestibility (TTAD) was 0.872, 0.887, 0.815 and 0.824 for energy and
0.847, 0.833, 0.665 and 0.795 for nitrogen for the wheat bran, sugar beet pulp, soya bean hulls and
alfalfa meal diet, respectively P < 0:01. The TTAD values for NDF were 0.615, 0.861, 0.721 and
0.593, and for ADF were 0.390, 0.779, 0.708 and 0.457 in diets based on wheat bran, sugar beet
pulp, soya bean hulls and alfalfa meal, respectively P < 0:01. The level of volatile fatty acids
(VFAs) in the caecum contents changed from 3.80 to 4.96 mg gÿ1 when sugar beet pulp replaced
soya bean hulls, respectively, the later producing a higher proportion of acetic acid P < 0:05. The
average molar proportions were 0.635, 0.245 and 0.10 for acetic, propionic and butyric acid,
respectively. Soya bean hulls in the diet increased the level of total VFA by 15 or 30% when
compared with the wheat bran or with the sugar beet pulp and the alfalfa meal, respectively
P < 0:05. For a constant nitrogen intake, the diet containing soya bean hulls supported the lowest
nitrogen retention. The mean retention time was 51.5, 49.9, 56.9 and 37.7 h for diets based on wheat
bran, sugar beet pulp, soya bean hulls and alfalfa meal, respectively P < 0:01. In contrast to
alfalfa meal, the soya bean hulls reduced the chromium excretion rate by 40% and delayed the
in¯exion point of the excretion curve by 11 h, and consequently the digestive transit time. In
conclusion, sugar beet pulp has the highest degradation rate of NDF and ADF fractions. The
inclusion of soya bean hulls leads to a decrease in the energy and nitrogen digestibility of the
*
Corresponding author. Tel.: 351-21-3653408; fax: 351-21-3630734
E-mail address: jpfreire@isa.utl.pt (J.P.B. Freire).
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 8 3 - 8
72
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
weaning diet. Finally, alfalfa meal was the most effective ®bre source to regulate the digestive
transit time. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Piglets; Dietary ®bre; Digestibility; Volatile fatty acids; Transit time
1. Introduction
The bene®cial effect of using non-starch polysaccharides (NSPs) in the diet of the
weaning piglet is based on the improvement of their health status (Aumaitre, 1969). In
fact, dietary ®bre can stimulate the digestive compartments (Longland et al., 1994) and
regulate the digestive transit time by an increase of the faecal volume (Knudsen and
Hansen, 1991).
Nevertheless, in the growing pig, the digestibility of energy is negatively affected by
the neutral detergent ®bre content of the diet (Noblet et al., 1993). In the piglet, the use of
NSP from wheat and barley in the weaning diet is generally associated with a reduction of
the total tract apparent digestibility (TTAD) of dry matter (DM) and energy (Bengala
Freire et al., 1990; Freire et al., 1998).
However, this depressive effect of dietary ®bre source on TTAD depends on its
composition due to different degradation rates in the hindgut (Chabeauti et al., 1994) and
to differences in the digestive transit time (Aman and Graham, 1991; Chesson, 1991). In
fact, the ability of 4-week old piglets to digest particular ®bre sources such as sugar beet
pulp without the depressive effects on TTAD of other dietary components has been
clearly demonstrated (Lizardo et al., 1997).
In the growing pig, digestive contents remain in the large intestine for more than 40 h,
mostly depending on the bulk capacity of the dietary ®bre (Knudsen and Hansen, 1991).
In the case of soluble and easy to ferment ®bre, the increase of faecal volume is small. In
contrast, ®bre sources with more ligni®ed cell walls have low water holding capacity but
are more resistant to the micro¯ora activity, and more effective in increasing the faecal
volume and reducing the digestive transit time (Chesson, 1991). Moreover, in contrast to
the digestive transit time measurements performed with growing pigs (Pond et al., 1986)
or peccary species (Comizzoli et al., 1997), the mean retention time (MRT) of the
undigested material in the digestive tract has never been determined in 4-week old
piglets.
Acetic, propionic and butyric acids are the major end products of ®bre degradation in
the hindgut of pigs (Ratcliffe, 1991). Therefore, the level of the volatile fatty acids
(VFAs) in the caecum contents can provide good prediction of the degree of fermentation
of the dietary ®bre. In the growing pig, this level ranges between 80 and 140 mmol lÿ1,
varying with the contents and composition of the dietary ®bre (Sauer et al., 1991;
Knudsen et al., 1993). The VFAs are known as an energy source for pigs (Dierick et al.,
1989), in particular butyric acid can be used by the intestinal epithelium as an energy
source (Argenzio and Southworth, 1974) and can support the development of the
digestive intestinal enzymes (Lizardo et al., 1997).
The current experiment was performed to evaluate the effects of wheat bran, sugar beet
pulp, soya bean hulls and alfalfa meal, used as the main dietary ®bre source, on the
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
73
caecum VFAs concentration and the digestive transit time of the weaned piglet in order to
explain differences in the TTAD values of the diets.
2. Materials and methods
2.1. Animals and diets
The effect of NSPs on the digestive process of the weaned piglet was studied using
24 Duroc Landrace male piglets, weaned at 28 days of age and with an initial average
live weight of 7:92 1:1 kg. The piglets, housed individually in metabolism cages, were
from six sows (four pigs per sow) and those within each litter were allotted, according to
their liveweight, to four groups. Each group received, on a pair feeding basis, one of four
experimental diets, presented as 3 mm diameter pellets. The diets contained similar crude
protein contents and total amino acids, calcium and phosphorus levels. Wheat bran, sugar
beet pulp, soya bean hulls and alfalfa meal commercially available were incorporated at
200 g kgÿ1 diet as the major ®bre sources in diets 1, 2, 3 and 4, respectively (Table 1).
The chemical composition of the ®bre sources is presented in Table 2.
After a short adaptation period of 4 days, individual measurements were performed
during three consecutive periods of 7 days. Faeces and urine were individually collected
on the ®rst and third period for determination of TTAD and nitrogen balance.
Subsequently, the digestive transit time was controlled during a subsequent period of 5
days. For this purpose, the four sources of ®bre were ®rst marked with 123, 158, 119 and
133 mg of Na2Cr2O7 per gram of wheat bran, sugar beet pulp, soya bean hulls and alfalfa
meal, respectively, and then incorporated in each experimental diet replacing 50% of the
non-marked ®bre, respectively. The marked ®bre sources were prepared according to
Uden et al. (1980), the quantity of Na2Cr2O7 was adjusted to obtain a concentration of
120 mg Cr gÿ1 of NDF. In the ®rst day of this period, the piglets received 300 g of the
marked diets in the morning, and 300 g of the non-marked diets in the afternoon. On the
following days, each piglet received 600 g of non-marked diets offered in two meals. The
faeces were collected every 2 h during the ®rst and second day, every 4 h during the third
day and the ®rst half of the fourth day, and every 12 h afterwards. Faeces were weighed and
stored at ÿ208C for analysis of DM and chromium. At the end of the experiment, the 58-days
old piglets were slaughtered under general anaesthesia, after a 16 h-fasting period, the
digestive tract was weighed, emptied and the caecal content was collected for analysis.
2.2. Analysis
At the end of each collection period, a representative sample of faeces and urine was
individually prepared. Samples of faeces were freeze dried and ground in a hammer mill
through a mesh of 1 mm. Similarly, samples of diets were ground to 1 mm before
analysis. DM was analysed by oven-drying at 1058C and ash by incineration at 5508C.
Gross energy was measured with a peribol calorimeter (Parr 1261, Moline Illinois, USA).
The cell wall constituents were analysed for NDF, ADF and ADL determination in a
Fibertec apparatus (Tecator 1020, Hogonas, Sweden) according to Van Soest et al. (1991).
74
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Table 1
Composition of the experimental diets (g kgÿ1) and chemical composition (g kgÿ1 fresh weight)
Diets
Wheat bran
Sugar beet pulp
Soya bean hulls
Alfalfa meal
Corn starch
Wheat bran
Sugar beet pulp
Soya bean hulls
Alfalfa meal
Dry milk
Fish meal
Potato protein
Soya bean oil
DL-Methionine
L-Tryptophan
Calcium carbonate
Dicalcium phosphate
Sodium chloride
Vitamin trace mineral mixa
408.0
200.0
±
±
±
100.0
100.0
100.0
50.0
1.0
±
10.0
16.0
5.0
10.0
403.2
±
200.0
±
±
100.0
100.0
100.0
50.0
1.5
0.3
±
30.0
5.0
10.0
403.8
±
±
200.0
±
100.0
100.0
100.0
50.0
1.0
0.2
±
30.0
5.0
10.0
404.0
±
±
±
200.0
100.0
100.0
100.0
50.0
1.0
±
±
30.0
5.0
10.0
Chemical composition
DM
Ash
Crude protein (N 6:25)
NDF
ADF
ADL
Starch
Gross energy (MJ kgÿ1)
920.4
64.2
200.8
128.0
34.5
12.1
411.2
17.87
926.6
75.3
202.3
159.7
71.3
6.1
349.7
17.47
952.4
68.4
207.8
130.4
81.1
8.0
337.8
17.86
956.7
73.6
199.7
155.9
87.0
29.1
376.9
17.72
a
Mineral and vitamin mixture supplied per kilogram of diet Ð Vit. A: 12,000 IU, Vit. D3: 2000 IU, Vit. E:
20.0 mg, Vit. B1: 1.0 mg, Vit. B2: 4.0 mg, Vit. B6: 1.50 mg, Vit. B12: 0.020 mg, Vit. K3: 2.0 mg, Vit. H2:
0.10 mg, nicotinic acid: 25.0 mg, folic acid: 0.50 mg, panthotenic acid: 15.0 mg, choline chloride: 400.0 mg,
calcium iodate: 0.60 mg, manganese (oxide): 40.0 mg, ferrous sulphate (5H2O): 125.0 mg, zinc (oxide):
100.0 mg, copper sulphate (5H2O): 160.0 mg, sodium selenite: 0.150 mg, cobalt sulphate: 0.400 mg, Bacillus
toyoi: 100.0 mg, carbadox: 50.0 mg, ¯avours: 500.0 mg, antioxidant (BHT): 60.0 mg, phosphoric acid:
1050.0 mg, citric acid: 150.0 mg.
Table 2
Chemical composition of the ®bre sources (g kgÿ1 fresh weight)
DM
Crude protein (N 6:25)
NDF
ADF
ADL
Wheat bran
Sugar beet pulp
Soya bean hulls
Alfalfa meal
886.3
150.9
406.9
118.8
37.7
914.7
116.2
526.5
224.1
18.4
901.0
147.0
396.4
303.0
24.1
898.3
148.2
442.6
322.8
86.5
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
75
Nitrogen of feeds, faeces and urine was analysed by the Kjeldahl method. Starch of feeds
was determined enzymatically (Bengala Freire et al., 1990). At slaughter, the caecal
content was immediately diluted (in a 10:1 proportion) with an additive prepared with a
1% (w/w) solution of mercuric chloride and 5% (v/v) orthophosphoric acid in distilled
water for preservation, according to the methodology of Jouany (1982). Afterwards, the
samples were centrifuged at 5000g for 5 min and the VFAs analysed in the supernatant by
gas chromatography in a Perkin Elmer (Model Sigma 3) chromatograph using a Capilar
Column Chromopack 7486. Only the three major VFAs were recorded and iso acids were
not determined. Chromium in feeds and faeces was analysed by atomic absorption
spectrophotometry after digestion of the samples for 2 h at 1408C in 15 ml of
concentrated HCl and 5 ml of concentrated nitric acid (Berrow and Stein, 1983).
2.3. Computations and statistic analysis
The TTAD and nitrogen balance results were compared by analysis of variance
according to a split-plot design, considering the mean square associated to the interaction
litter diet as the residual error to test the effect of the diet. Data concerning growth
performance, weight of the digestive organs and VFA level (expressed by g of cascal
content) were compared by an analysis of variance according to a complete block design
with the effect of the litters confounded with the effect of blocks.
The cumulative percentage of the marker recovered in faeces was plotted to the time
after feeding. These curves expressed a delay in the ®rst appearance of the marker in the
faeces and an in¯exion point, so chromium excretion was adjusted according to a nonlinear equation (Dagnelie, 1975). The function that better ®tted the excretion of the
chromium was the non-linear logistic equation:
Y A 1 eÿKt ÿM
where Y is the cumulative chromium excreted expressed as a percentage of the chromium
intake, A the chromium excreted during the time 0 to 1 expressed as a percentage of
intake, K the chromium excretion rate (% hÿ1), t the time after the intake of the marked
feed (h), and M a parameter related with the time of occurrence of the in¯exion point.
The MRT
was
P calculated according to the formula of Faichney (1975):
P
MRT
mi ti = mi , where mi is the fraction of the marker excreted at time ti. The
digestive transit time was analysed by analysis of variance of the MRT and the parameters
(A, K, M) of the logistic equation. When the F value in the analysis of variance was
signi®cant, the means were compared by a Duncan's multiple range test (Dagnelie, 1975).
All the analysis of variance and the Duncan's test were performed by the SAS program,
procedure GLM (SAS, 1991). The computation of the chromium excretion curves was undertaken by the SAS program, procedure NLIN, using the DUD adjustment method (SAS, 1989).
3. Results
The nature of the dietary ®bre signi®cantly changed both growth rate and feed
conversion of the weaned piglets. For a constant feed intake, the addition of soya bean
76
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Table 3
Effect of dietary ®bre source on performance of piglets between 32 and 53 days of age
Dietsa
Initial weight (kg)
Final weight (kg)
Feed intake (kg per day)
Average daily gain (kg per day)
Feed conversion
Statistical analysisb
Wheat
bran
Sugar beet
pulp
Soya bean
hulls
Alfalfa
meal
L
D
RSD
8.03
15.85
0.444
0.372 a
1.20 a
8.05
15.67
0.434
0.362 a
1.20 a
7.67
13.88
0.424
0.295 b
1.45 b
7.92
15.80
0.445
0.375 a
1.19 a
*
NSc
NS
NS
1.15
1.55
0.02
0.03
0.09
NS
NS
NS
NS
**
**
a
Means with the same letters on the same line are not signi®cantly different.
L: litter, D: diet, RSD: residual standard deviation.
c
NS: nonsigni®cant.
*
P < 0:05.
**
P < 0:01.
b
hulls to the diet reduced the daily growth rate by 20% and increased the feed conversion
by 17% when compared with the other ®bre sources (Table 3). The sugar beet pulp diet,
in comparison with the wheat bran, increased the TTAD of DM and energy (E) by 2.4 and
1.7%, respectively (Table 4). In contrast, the replacement of wheat bran by soya bean
hulls or alfalfa meal decreased P < 0:01 the TTAD values of DM by 4.5 and 4.2% and
the TTAD of nitrogen by 21.5 and 6.1%, respectively. Among the four cell wall sources,
the sugar beet pulp-based diet showed the highest digestibility for NDF, ADF,
hemicellulose (NDF±ADF) and cellulose (ADF±ADL) fractions. Fibre from wheat bran
was generally less degraded by the young piglet. In general, TTAD of hemicellulose was
high, particularly in the case of the sugar beet pulp-based diet. TTAD of cellulose was
also high and similar for sugar beet pulp and soya bean hulls diets but was considerably
lower for both wheat bran and alfalfa diets P < 0:01. With the exception of the
hemicellulose and cellulose fractions, the TTAD was signi®cantly increased between the
®rst and the third experimental period.
The source of ®bre in the weaning diet changed signi®cantly the relative weight of the
gut compartments (Table 5). Soya bean hulls increased P < 0:05 the relative weight of
the total and empty small intestine by 15 and 13%, and the weight of the total and empty
large intestine by 35 and 16%, respectively P < 0:01. The presence of soya bean hulls
almost doubled the weight of the large intestine contents when compared with sugar beet
pulp.
The concentration of the total VFA levels in the caecum contents at slaughter (Table 6)
depended signi®cantly on the source of dietary ®bre. The use of soya bean hulls in the
weaning diet increased P < 0:05 the concentration of total VFA by 11.2, 30.5 and
27.2% when compared with the wheat bran, the sugar beet pulp and the alfalfa diets,
respectively. This effect was associated with an increase in the level of acetic acid, and of
the ratio acetate:propionate and acetate:butyrate, which were signi®cantly higher in
animals fed with the soya bean hulls diet P < 0:01.
For a constant nitrogen intake, soya bean hulls reduced P < 0:01 the daily nitrogen
retention by 25%, when compared with the other ®bre sources (Table 4). Likewise, in
77
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Table 4
Effect of dietary ®bre source and experimental period on total tract apparent digestibility (TTAD) of dietary
components, digestible and metabolizable energy and nitrogen balance
Dietsa
Periodsb
Wheat
bran
Sugar beet Soya bean Alfalfa
pulp
hulls
meal
NDF (g kgÿ1)
ADF (g kgÿ1)
ADL (g kgÿ1)
128.0
34.0
12.1
160.0
71.0
6.1
TTAD
DM
Nitrogen
NDF
ADF
Hemicellulosed
Cellulosed
Gross energy
0.867
0.847
0.615
0.390
0.698
0.317
0.872
DE (MJ kgÿ1)f
ME (MJ kgÿ1)g
16.87 a
14.91 a
16.72 a
14.78 a
15.44 b
12.95 b
15.24 b
13.23 b
15.80
13.90
13.68
13.95
13.79
13.99
10.13 a
2.99 a
85.6 ab
72.3 a
10.70 a
4.24 b
90.4 a
75.4 a
7.58
5.60
78.4
52.5
9.93
4.04
88.0
70.0
N balance
N intake (g per day)
N retention
(g per day)
(% of daily gain)
(% of N absorbed)
(% of N intake)
a
a
a
a
a
a
a
0.888
0.833
0.861
0.779
0.927
0.755
0.887
130.0
81.0
8.0
b
ab
b
b
b
b
a
0.828
0.665
0.721
0.708
0.742
0.688
0.815
1
Statistical analysisc
3
D
P
RSD
**
**
**
**
**
*
**
*
**
NSe
NS
0.01
0.05
0.04
0.06
0.02
0.08
0.02
156.0
87.0
29.1
c
c
c
c
c
b
b
b
c
b
b
0.831
0.795
0.593
0.457
0.764
0.341
0.824
a
b
a
a
c
b
a
d
c
a
b
0.843
0.763
0.686
0.569
0.678
0.773
0.837
0.864
0.807
0.709
0.598
0.689
0.792
0.862
**
**
**
16.31
14.10
**
**
**
NS
10.43
17.46
NS
**
0.36
6.43
4.88
80.3
61.5
12.92
3.56
91.3
74.1
**
**
**
**
*
**
**
**
0.95
0.82
8.52
8.54
0.42
0.95
a
For diet effects, means with the same letters on the same line are not signi®cantly different.
Period 1: 32±39 days of age, period 3: 46±53 days of age.
c
D: diet, P: period, D P: interaction diet period, RSD: residual standard deviation. Interaction D P
was only signi®cant (P < 0:01) for N retention expressed in % of daily gain.
d
Hemicellulose and cellulose are NDF±ADF and ADF±ADL, respectively, according to Van Soest et al.
(1991).
e
NS: nonsigni®cant.
f
Digestible energy.
g
Metaboilizable energy.
*
P < 0:05.
**
P < 0:01.
b
animals fed with the diet containing soya bean hulls the amount of retained nitrogen,
expressed as a percentage of intake or absorbed, was reduced by 14 and 10 percentage
units, respectively.
The analysis of the parameters used to control the digestive transit time (Table 7, Fig. 1)
shows a decrease in the transit time with the inclusion of 200 g of alfalfa per kilogram
diet. In mean terms, alfalfa almost doubled the chromium excretion rate (K). As a
consequence, the excretion time for 25 and 50% of the total chromium intake was
reduced by 13 and 22 h, respectively and the MRT was reduced by 15 h P < 0:01. In
78
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Table 5
Effect of dietary ®bre source on the fresh weight of the stomach, the small and large intestine and the intestinal
contents (g kgÿ1 live weight)
Dietsa
Statistical analysisb
Wheat
bran
Sugar beet
pulp
Soya bean
hulls
Alfalfa
meal
L
D
RSD
Stomach
Total
Empty
10.04
7.80 a
10.73
9.12 b
10.40
8.52 ab
10.21
7.79 a
NSc
NS
NS
1.44
0.76
Small intestine
Total
Empty
36.34 a
30.24 a
37.88 a
32.20 ab
42.37 b
35.02 b
36.33 a
30.34 a
*
*
NS
*
Large intestine
Total
Empty
32.28 a
15.68 a
31.77 a
18.42 b
43.33 b
18.51 b
32.35 a
13.76 a
NS
NS
**
Stomach content
Small intestine content
Large intestine content
Caecum content
2.24
6.11
16.60 a
2.63
1.61
5.68
13.35 a
1.87
1.88
7.35
24.82 b
2.96
2.41
6.00
18.59 a
1.20
NS
NS
NS
*
NS
NS
*
**
**
NS
3.33
2.56
5.53
2.19
0.99
2.01
4.94
1.05
a
Means with the same letters on the same line are not signi®cantly different.
L: litter, D: diet, RSD: residual standard deviation.
c
NS: nonsigni®cant.
*
P < 0:05.
**
P < 0:01.
b
addition, the soya bean hulls reduced the chromium excretion rate by 40% and delayed
the in¯exion point of the excretion curve by 11 h.
4. Discussion
4.1. Digestibility
The decrease in the daily growth rate and the increase in feed conversion veri®ed with
the incorporation of soya bean hulls in the weaning diet is associated with the decrease of
the digestible energy content of the diet (Table 4), which is in agreement with data
reported with the growing pig (Quiniou et al., 1999). Furthermore, once the diets were
balanced in total essential amino acids, the increase in the urinary nitrogen excretion with
the incorporation of soya bean hulls may be the result of a higher microbial production of
ammonia in the large intestine, which is then excreted as urinary urea (Ratcliffe, 1991).
The increase in DM digestibility with the use of sugar beet pulp may be a consequence of
its high level of digestible NDF, ADF, pectins and their constituent monosaccharides and
uronic acids (Longland et al., 1994). This result is in accordance with the high
fermentation level of this ®bre source, found not only in the growing pig (Graham et al.,
1986; Chabeauti et al., 1994) but also in the 6-week old piglet (Lizardo et al., 1997).
Table 6
Effect of dietary ®bre source on the concentration of VFAs and pro®le in the caecal contents at slaughter
Dietsa
Hemicellulose (NDF±ADF) (g kgÿ1)
Cellulose (ADF±ADL) (g kgÿ1)
Statistical analysisb
Wheat
bran
Sugar beet Soya bean
pulp
hulls
Alfalfa
meal
93.5
22.4
88.4
65.2
68.9
57.9
49.3
73.1
L
D
RSD
*
0.29
*
0.49
0.26
0.14
0.82
6.17 a
6.55 bc
6.28 ab
6.74 c
NSc
Concentration (mg g )
Acetic Ð C2
Propionic Ð C3
Butyric Ð C4
Total (C2 C3 C4 )
2.36 a
1.35
0.74 a
4.46 ab
2.11 a
1.09
0.60 ab
3.80 a
3.03 b
1.38
0.56 b
4.96 b
2.19 a
1.28
0.43 b
3.90 a
NS
NS
NS
NS
Molar proportions
C2/C3
C2/C4
C2/(C3 C4 )
C2/(C2 C3 C4 )
C3/(C2 C3 C4 )
C4/(C2 C3 C4 )
2.24 ab
4.91 a
1.53 a
0.604 a
0.272 ab
0.125 a
2.53 bc
5.46 a
1.71 a
0.631 a
0.252 bc
0.117 a
2.81 c
8.49 b
2.10 b
0.674 b
0.244 c
0.082 b
2.19 a
8.32 b
1.72 a
0.630 a
0.290 a
0.080 b
*
**
NS
NS
NS
**
*
**
NS
**
pH
ÿ1 d
NS
**
*
**
**
0.26
1.65
0.20
0.02
0.02
0.02
a
Means with the same letters on the same line are not signi®cantly different (n 6 piglets per diet).
L: litter, D: diet, RSD: residual standard deviation.
c
NS: nonsigni®cant.
d
VFA concentration (mg gÿ1 of caecal content).
*
P < 0:05.
**
P < 0:01.
b
Table 7
Effect of dietary ®bre source on the parameters of the mathematical model of chromium excretion
Dietsa
A (% of Cr intake)c
K (% Cr excreted per hour)e
In¯exion point (h)f
Cr 25% (h)g
Cr 50% (h)h
MRT (h)i
a
Statistical analysisb
Wheat
bran
Sugar beet
pulp
Soya bean
hulls
Alfalfa
meal
D
RSD
67.9
0.072 a
41.3 a
41.8 a
67.3 a
51.5 a
79.8
0.074 a
41.5 a
39.7 a
53.0 ab
49.9 a
79.9
0.056 a
49.0 b
46.2 a
61.3 a
56.9 a
75.7
0.123 b
30.3 c
29.8 b
36.8 b
37.7 b
NSd
14.0
0.02
6.91
7.04
16.33
6.38
Means with the same letters on the same line are not signi®cantly different.
D: diet, RSD: residual standard deviation.
c
Chromium recovered during the period 0 to 1.
d
NS: nonsigni®cant.
e
Chromium excretion rate.
f
In¯exion point of the chromium excretion curve.
g
Time (h) for recovery of 25% of the chromium intake.
h
Time (h) for recovery of 50% of the chromium intake.
i
Mean retention time.
*
P < 0:05.
**
P < 0:01.
b
**
**
**
*
**
80
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Fig. 1. Effect of dietary ®bre source on the chromium excretion curves according to the prediction of the
mathematical model.
The lower TTAD of nitrogen (Table 4) for the soya bean hulls diet may be explained by
the presence of residual antitrypsin factors (Bengala Freire et al., 1991; Fan et al., 1995)
or by an increase in the microbial nitrogen faecal excretion (Stanogias and Pearce,
1985a). In fact, the presence of 50 g a-galactosides per kilogram soya bean hulls can be
used as an energy source by the gut micro¯ora with an increase in its fermentative activity
(Bengala Freire et al., 1991). Furthermore, the relatively low digestibility of cell walls
fractions of the wheat bran or alfalfa diets might be explained by their higher level of
lignin (Graham et al., 1986; Kass et al., 1980a). The signi®cant increase in the TTAD of
energy and ®brous components with the age of piglets seems to demonstrate a progressive
maturation of the digestive tract, which is in agreement with Longland et al. (1994).
4.2. Fermentative activity in the caecum
Considering the mean value for all diets, the levels of acetic, propionic and butyric acid
corresponded to 65, 25 and 10% of the total VFA, respectively. These values are in
accordance with previous data presented by Kass et al. (1980b) and Sauer et al. (1991).
The maximum level of total VFA was observed for soya bean hulls-based diet. This result
suggests a high degradation rate in the caecum, and is in agreement with the high
digestibility values of the NDF and ADF fractions. The relatively lower values of VFA
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
81
measured in the sugar beet pulp diet could also be associated with a higher absorption
rate of its metabolites in the caecum. The higher level of butyric acid found in the caecum
content of the piglets fed with the wheat bran diet may be generated by small quantities of
endosperm that escape digestion in the small intestine and are fermented in the large
intestines, lowering the pH in the caecum. The VFA may also stimulate the epithelial
mucosa, changing the fresh weight of the small and the large intestine, particularly for the
diet based on soya bean hulls (Stanogias and Pearce, 1985b).
4.3. Digestive transit time
The mathematical model describing the chromium excretion ®ts the model reported by
Pond et al. (1986) comparing the use of different markers to describe the transit of
undigested materials in the growing pig. The alfalfa diet decreased not only the digestive
transit time but also the digestibility of the NDF and ADF fractions. These results
corroborate the hypothesis of Knudsen and Hansen (1991) that indicated an increase in
the transit passage with less degradable ®bres, due to their higher water holding capacity.
The delay in the in¯exion point of chromium excretion curve represented a slower
digestive transit. According to Knudsen and Hansen (1991), the use of soluble ®bres in
the diet such as sugar beet pulp may increase the viscosity of the intralumen contents of
the gut, delaying the digestive transit in the small intestine and completing the digestive
process in the piglet.
In conclusion, the effect of the sugar beet pulp on the digestible energy of the weaning
diet is minimized by the high degradation rate of its NDF and ADF fractions. On the other
hand, the soya bean hulls seemed to be less appropriate to the low digestive capacity of
the young pig, probably due to the presence of antitrypsin factors and a-galactosides.
Finally, among the four ®bre sources studied, the alfalfa meal was the most effective in
regulating the digestive transit time. However, its negative effect on the digestible energy
of the weaning diet must be considered before recommending its incorporation in the
starter diet of piglets.
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87 (2000) 71±83
Effect of dietary ®bre source on total tract
digestibility, caecum volatile fatty acids and
digestive transit time in the weaned piglet
J.P.B. Freirea,*, A.J.G. Guerreiroa, L.F. Cunhaa, A. Aumaitreb
a
Dpto. de Producao Agricola e Animal, Seccao de Producao Animal, Instituto Superior de Agronomia,
Tapada da Ajuda, 1349-017 Lisbon, Portugal
b
Unite Mixte de Recherches sur le Veau et le Porc, 35590 St. Gilles, France
Received 20 October 1999; received in revised form 25 April 2000; accepted 5 July 2000
Abstract
Effects of the use of 200 g of either wheat bran, sugar beet pulp, soya bean hulls or alfalfa meal
per kilogram diet on the digestive process of the weaned piglet were studied on
24 Duroc Landrace male piglets, weaned at 28 days of age. Piglets had an initial mean live
weight of 7.92(1.1) kg and were randomly distributed in six successive blocks of four animals.
The total tract apparent digestibility (TTAD) was 0.872, 0.887, 0.815 and 0.824 for energy and
0.847, 0.833, 0.665 and 0.795 for nitrogen for the wheat bran, sugar beet pulp, soya bean hulls and
alfalfa meal diet, respectively P < 0:01. The TTAD values for NDF were 0.615, 0.861, 0.721 and
0.593, and for ADF were 0.390, 0.779, 0.708 and 0.457 in diets based on wheat bran, sugar beet
pulp, soya bean hulls and alfalfa meal, respectively P < 0:01. The level of volatile fatty acids
(VFAs) in the caecum contents changed from 3.80 to 4.96 mg gÿ1 when sugar beet pulp replaced
soya bean hulls, respectively, the later producing a higher proportion of acetic acid P < 0:05. The
average molar proportions were 0.635, 0.245 and 0.10 for acetic, propionic and butyric acid,
respectively. Soya bean hulls in the diet increased the level of total VFA by 15 or 30% when
compared with the wheat bran or with the sugar beet pulp and the alfalfa meal, respectively
P < 0:05. For a constant nitrogen intake, the diet containing soya bean hulls supported the lowest
nitrogen retention. The mean retention time was 51.5, 49.9, 56.9 and 37.7 h for diets based on wheat
bran, sugar beet pulp, soya bean hulls and alfalfa meal, respectively P < 0:01. In contrast to
alfalfa meal, the soya bean hulls reduced the chromium excretion rate by 40% and delayed the
in¯exion point of the excretion curve by 11 h, and consequently the digestive transit time. In
conclusion, sugar beet pulp has the highest degradation rate of NDF and ADF fractions. The
inclusion of soya bean hulls leads to a decrease in the energy and nitrogen digestibility of the
*
Corresponding author. Tel.: 351-21-3653408; fax: 351-21-3630734
E-mail address: jpfreire@isa.utl.pt (J.P.B. Freire).
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 8 3 - 8
72
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
weaning diet. Finally, alfalfa meal was the most effective ®bre source to regulate the digestive
transit time. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Piglets; Dietary ®bre; Digestibility; Volatile fatty acids; Transit time
1. Introduction
The bene®cial effect of using non-starch polysaccharides (NSPs) in the diet of the
weaning piglet is based on the improvement of their health status (Aumaitre, 1969). In
fact, dietary ®bre can stimulate the digestive compartments (Longland et al., 1994) and
regulate the digestive transit time by an increase of the faecal volume (Knudsen and
Hansen, 1991).
Nevertheless, in the growing pig, the digestibility of energy is negatively affected by
the neutral detergent ®bre content of the diet (Noblet et al., 1993). In the piglet, the use of
NSP from wheat and barley in the weaning diet is generally associated with a reduction of
the total tract apparent digestibility (TTAD) of dry matter (DM) and energy (Bengala
Freire et al., 1990; Freire et al., 1998).
However, this depressive effect of dietary ®bre source on TTAD depends on its
composition due to different degradation rates in the hindgut (Chabeauti et al., 1994) and
to differences in the digestive transit time (Aman and Graham, 1991; Chesson, 1991). In
fact, the ability of 4-week old piglets to digest particular ®bre sources such as sugar beet
pulp without the depressive effects on TTAD of other dietary components has been
clearly demonstrated (Lizardo et al., 1997).
In the growing pig, digestive contents remain in the large intestine for more than 40 h,
mostly depending on the bulk capacity of the dietary ®bre (Knudsen and Hansen, 1991).
In the case of soluble and easy to ferment ®bre, the increase of faecal volume is small. In
contrast, ®bre sources with more ligni®ed cell walls have low water holding capacity but
are more resistant to the micro¯ora activity, and more effective in increasing the faecal
volume and reducing the digestive transit time (Chesson, 1991). Moreover, in contrast to
the digestive transit time measurements performed with growing pigs (Pond et al., 1986)
or peccary species (Comizzoli et al., 1997), the mean retention time (MRT) of the
undigested material in the digestive tract has never been determined in 4-week old
piglets.
Acetic, propionic and butyric acids are the major end products of ®bre degradation in
the hindgut of pigs (Ratcliffe, 1991). Therefore, the level of the volatile fatty acids
(VFAs) in the caecum contents can provide good prediction of the degree of fermentation
of the dietary ®bre. In the growing pig, this level ranges between 80 and 140 mmol lÿ1,
varying with the contents and composition of the dietary ®bre (Sauer et al., 1991;
Knudsen et al., 1993). The VFAs are known as an energy source for pigs (Dierick et al.,
1989), in particular butyric acid can be used by the intestinal epithelium as an energy
source (Argenzio and Southworth, 1974) and can support the development of the
digestive intestinal enzymes (Lizardo et al., 1997).
The current experiment was performed to evaluate the effects of wheat bran, sugar beet
pulp, soya bean hulls and alfalfa meal, used as the main dietary ®bre source, on the
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
73
caecum VFAs concentration and the digestive transit time of the weaned piglet in order to
explain differences in the TTAD values of the diets.
2. Materials and methods
2.1. Animals and diets
The effect of NSPs on the digestive process of the weaned piglet was studied using
24 Duroc Landrace male piglets, weaned at 28 days of age and with an initial average
live weight of 7:92 1:1 kg. The piglets, housed individually in metabolism cages, were
from six sows (four pigs per sow) and those within each litter were allotted, according to
their liveweight, to four groups. Each group received, on a pair feeding basis, one of four
experimental diets, presented as 3 mm diameter pellets. The diets contained similar crude
protein contents and total amino acids, calcium and phosphorus levels. Wheat bran, sugar
beet pulp, soya bean hulls and alfalfa meal commercially available were incorporated at
200 g kgÿ1 diet as the major ®bre sources in diets 1, 2, 3 and 4, respectively (Table 1).
The chemical composition of the ®bre sources is presented in Table 2.
After a short adaptation period of 4 days, individual measurements were performed
during three consecutive periods of 7 days. Faeces and urine were individually collected
on the ®rst and third period for determination of TTAD and nitrogen balance.
Subsequently, the digestive transit time was controlled during a subsequent period of 5
days. For this purpose, the four sources of ®bre were ®rst marked with 123, 158, 119 and
133 mg of Na2Cr2O7 per gram of wheat bran, sugar beet pulp, soya bean hulls and alfalfa
meal, respectively, and then incorporated in each experimental diet replacing 50% of the
non-marked ®bre, respectively. The marked ®bre sources were prepared according to
Uden et al. (1980), the quantity of Na2Cr2O7 was adjusted to obtain a concentration of
120 mg Cr gÿ1 of NDF. In the ®rst day of this period, the piglets received 300 g of the
marked diets in the morning, and 300 g of the non-marked diets in the afternoon. On the
following days, each piglet received 600 g of non-marked diets offered in two meals. The
faeces were collected every 2 h during the ®rst and second day, every 4 h during the third
day and the ®rst half of the fourth day, and every 12 h afterwards. Faeces were weighed and
stored at ÿ208C for analysis of DM and chromium. At the end of the experiment, the 58-days
old piglets were slaughtered under general anaesthesia, after a 16 h-fasting period, the
digestive tract was weighed, emptied and the caecal content was collected for analysis.
2.2. Analysis
At the end of each collection period, a representative sample of faeces and urine was
individually prepared. Samples of faeces were freeze dried and ground in a hammer mill
through a mesh of 1 mm. Similarly, samples of diets were ground to 1 mm before
analysis. DM was analysed by oven-drying at 1058C and ash by incineration at 5508C.
Gross energy was measured with a peribol calorimeter (Parr 1261, Moline Illinois, USA).
The cell wall constituents were analysed for NDF, ADF and ADL determination in a
Fibertec apparatus (Tecator 1020, Hogonas, Sweden) according to Van Soest et al. (1991).
74
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Table 1
Composition of the experimental diets (g kgÿ1) and chemical composition (g kgÿ1 fresh weight)
Diets
Wheat bran
Sugar beet pulp
Soya bean hulls
Alfalfa meal
Corn starch
Wheat bran
Sugar beet pulp
Soya bean hulls
Alfalfa meal
Dry milk
Fish meal
Potato protein
Soya bean oil
DL-Methionine
L-Tryptophan
Calcium carbonate
Dicalcium phosphate
Sodium chloride
Vitamin trace mineral mixa
408.0
200.0
±
±
±
100.0
100.0
100.0
50.0
1.0
±
10.0
16.0
5.0
10.0
403.2
±
200.0
±
±
100.0
100.0
100.0
50.0
1.5
0.3
±
30.0
5.0
10.0
403.8
±
±
200.0
±
100.0
100.0
100.0
50.0
1.0
0.2
±
30.0
5.0
10.0
404.0
±
±
±
200.0
100.0
100.0
100.0
50.0
1.0
±
±
30.0
5.0
10.0
Chemical composition
DM
Ash
Crude protein (N 6:25)
NDF
ADF
ADL
Starch
Gross energy (MJ kgÿ1)
920.4
64.2
200.8
128.0
34.5
12.1
411.2
17.87
926.6
75.3
202.3
159.7
71.3
6.1
349.7
17.47
952.4
68.4
207.8
130.4
81.1
8.0
337.8
17.86
956.7
73.6
199.7
155.9
87.0
29.1
376.9
17.72
a
Mineral and vitamin mixture supplied per kilogram of diet Ð Vit. A: 12,000 IU, Vit. D3: 2000 IU, Vit. E:
20.0 mg, Vit. B1: 1.0 mg, Vit. B2: 4.0 mg, Vit. B6: 1.50 mg, Vit. B12: 0.020 mg, Vit. K3: 2.0 mg, Vit. H2:
0.10 mg, nicotinic acid: 25.0 mg, folic acid: 0.50 mg, panthotenic acid: 15.0 mg, choline chloride: 400.0 mg,
calcium iodate: 0.60 mg, manganese (oxide): 40.0 mg, ferrous sulphate (5H2O): 125.0 mg, zinc (oxide):
100.0 mg, copper sulphate (5H2O): 160.0 mg, sodium selenite: 0.150 mg, cobalt sulphate: 0.400 mg, Bacillus
toyoi: 100.0 mg, carbadox: 50.0 mg, ¯avours: 500.0 mg, antioxidant (BHT): 60.0 mg, phosphoric acid:
1050.0 mg, citric acid: 150.0 mg.
Table 2
Chemical composition of the ®bre sources (g kgÿ1 fresh weight)
DM
Crude protein (N 6:25)
NDF
ADF
ADL
Wheat bran
Sugar beet pulp
Soya bean hulls
Alfalfa meal
886.3
150.9
406.9
118.8
37.7
914.7
116.2
526.5
224.1
18.4
901.0
147.0
396.4
303.0
24.1
898.3
148.2
442.6
322.8
86.5
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
75
Nitrogen of feeds, faeces and urine was analysed by the Kjeldahl method. Starch of feeds
was determined enzymatically (Bengala Freire et al., 1990). At slaughter, the caecal
content was immediately diluted (in a 10:1 proportion) with an additive prepared with a
1% (w/w) solution of mercuric chloride and 5% (v/v) orthophosphoric acid in distilled
water for preservation, according to the methodology of Jouany (1982). Afterwards, the
samples were centrifuged at 5000g for 5 min and the VFAs analysed in the supernatant by
gas chromatography in a Perkin Elmer (Model Sigma 3) chromatograph using a Capilar
Column Chromopack 7486. Only the three major VFAs were recorded and iso acids were
not determined. Chromium in feeds and faeces was analysed by atomic absorption
spectrophotometry after digestion of the samples for 2 h at 1408C in 15 ml of
concentrated HCl and 5 ml of concentrated nitric acid (Berrow and Stein, 1983).
2.3. Computations and statistic analysis
The TTAD and nitrogen balance results were compared by analysis of variance
according to a split-plot design, considering the mean square associated to the interaction
litter diet as the residual error to test the effect of the diet. Data concerning growth
performance, weight of the digestive organs and VFA level (expressed by g of cascal
content) were compared by an analysis of variance according to a complete block design
with the effect of the litters confounded with the effect of blocks.
The cumulative percentage of the marker recovered in faeces was plotted to the time
after feeding. These curves expressed a delay in the ®rst appearance of the marker in the
faeces and an in¯exion point, so chromium excretion was adjusted according to a nonlinear equation (Dagnelie, 1975). The function that better ®tted the excretion of the
chromium was the non-linear logistic equation:
Y A 1 eÿKt ÿM
where Y is the cumulative chromium excreted expressed as a percentage of the chromium
intake, A the chromium excreted during the time 0 to 1 expressed as a percentage of
intake, K the chromium excretion rate (% hÿ1), t the time after the intake of the marked
feed (h), and M a parameter related with the time of occurrence of the in¯exion point.
The MRT
was
P calculated according to the formula of Faichney (1975):
P
MRT
mi ti = mi , where mi is the fraction of the marker excreted at time ti. The
digestive transit time was analysed by analysis of variance of the MRT and the parameters
(A, K, M) of the logistic equation. When the F value in the analysis of variance was
signi®cant, the means were compared by a Duncan's multiple range test (Dagnelie, 1975).
All the analysis of variance and the Duncan's test were performed by the SAS program,
procedure GLM (SAS, 1991). The computation of the chromium excretion curves was undertaken by the SAS program, procedure NLIN, using the DUD adjustment method (SAS, 1989).
3. Results
The nature of the dietary ®bre signi®cantly changed both growth rate and feed
conversion of the weaned piglets. For a constant feed intake, the addition of soya bean
76
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Table 3
Effect of dietary ®bre source on performance of piglets between 32 and 53 days of age
Dietsa
Initial weight (kg)
Final weight (kg)
Feed intake (kg per day)
Average daily gain (kg per day)
Feed conversion
Statistical analysisb
Wheat
bran
Sugar beet
pulp
Soya bean
hulls
Alfalfa
meal
L
D
RSD
8.03
15.85
0.444
0.372 a
1.20 a
8.05
15.67
0.434
0.362 a
1.20 a
7.67
13.88
0.424
0.295 b
1.45 b
7.92
15.80
0.445
0.375 a
1.19 a
*
NSc
NS
NS
1.15
1.55
0.02
0.03
0.09
NS
NS
NS
NS
**
**
a
Means with the same letters on the same line are not signi®cantly different.
L: litter, D: diet, RSD: residual standard deviation.
c
NS: nonsigni®cant.
*
P < 0:05.
**
P < 0:01.
b
hulls to the diet reduced the daily growth rate by 20% and increased the feed conversion
by 17% when compared with the other ®bre sources (Table 3). The sugar beet pulp diet,
in comparison with the wheat bran, increased the TTAD of DM and energy (E) by 2.4 and
1.7%, respectively (Table 4). In contrast, the replacement of wheat bran by soya bean
hulls or alfalfa meal decreased P < 0:01 the TTAD values of DM by 4.5 and 4.2% and
the TTAD of nitrogen by 21.5 and 6.1%, respectively. Among the four cell wall sources,
the sugar beet pulp-based diet showed the highest digestibility for NDF, ADF,
hemicellulose (NDF±ADF) and cellulose (ADF±ADL) fractions. Fibre from wheat bran
was generally less degraded by the young piglet. In general, TTAD of hemicellulose was
high, particularly in the case of the sugar beet pulp-based diet. TTAD of cellulose was
also high and similar for sugar beet pulp and soya bean hulls diets but was considerably
lower for both wheat bran and alfalfa diets P < 0:01. With the exception of the
hemicellulose and cellulose fractions, the TTAD was signi®cantly increased between the
®rst and the third experimental period.
The source of ®bre in the weaning diet changed signi®cantly the relative weight of the
gut compartments (Table 5). Soya bean hulls increased P < 0:05 the relative weight of
the total and empty small intestine by 15 and 13%, and the weight of the total and empty
large intestine by 35 and 16%, respectively P < 0:01. The presence of soya bean hulls
almost doubled the weight of the large intestine contents when compared with sugar beet
pulp.
The concentration of the total VFA levels in the caecum contents at slaughter (Table 6)
depended signi®cantly on the source of dietary ®bre. The use of soya bean hulls in the
weaning diet increased P < 0:05 the concentration of total VFA by 11.2, 30.5 and
27.2% when compared with the wheat bran, the sugar beet pulp and the alfalfa diets,
respectively. This effect was associated with an increase in the level of acetic acid, and of
the ratio acetate:propionate and acetate:butyrate, which were signi®cantly higher in
animals fed with the soya bean hulls diet P < 0:01.
For a constant nitrogen intake, soya bean hulls reduced P < 0:01 the daily nitrogen
retention by 25%, when compared with the other ®bre sources (Table 4). Likewise, in
77
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Table 4
Effect of dietary ®bre source and experimental period on total tract apparent digestibility (TTAD) of dietary
components, digestible and metabolizable energy and nitrogen balance
Dietsa
Periodsb
Wheat
bran
Sugar beet Soya bean Alfalfa
pulp
hulls
meal
NDF (g kgÿ1)
ADF (g kgÿ1)
ADL (g kgÿ1)
128.0
34.0
12.1
160.0
71.0
6.1
TTAD
DM
Nitrogen
NDF
ADF
Hemicellulosed
Cellulosed
Gross energy
0.867
0.847
0.615
0.390
0.698
0.317
0.872
DE (MJ kgÿ1)f
ME (MJ kgÿ1)g
16.87 a
14.91 a
16.72 a
14.78 a
15.44 b
12.95 b
15.24 b
13.23 b
15.80
13.90
13.68
13.95
13.79
13.99
10.13 a
2.99 a
85.6 ab
72.3 a
10.70 a
4.24 b
90.4 a
75.4 a
7.58
5.60
78.4
52.5
9.93
4.04
88.0
70.0
N balance
N intake (g per day)
N retention
(g per day)
(% of daily gain)
(% of N absorbed)
(% of N intake)
a
a
a
a
a
a
a
0.888
0.833
0.861
0.779
0.927
0.755
0.887
130.0
81.0
8.0
b
ab
b
b
b
b
a
0.828
0.665
0.721
0.708
0.742
0.688
0.815
1
Statistical analysisc
3
D
P
RSD
**
**
**
**
**
*
**
*
**
NSe
NS
0.01
0.05
0.04
0.06
0.02
0.08
0.02
156.0
87.0
29.1
c
c
c
c
c
b
b
b
c
b
b
0.831
0.795
0.593
0.457
0.764
0.341
0.824
a
b
a
a
c
b
a
d
c
a
b
0.843
0.763
0.686
0.569
0.678
0.773
0.837
0.864
0.807
0.709
0.598
0.689
0.792
0.862
**
**
**
16.31
14.10
**
**
**
NS
10.43
17.46
NS
**
0.36
6.43
4.88
80.3
61.5
12.92
3.56
91.3
74.1
**
**
**
**
*
**
**
**
0.95
0.82
8.52
8.54
0.42
0.95
a
For diet effects, means with the same letters on the same line are not signi®cantly different.
Period 1: 32±39 days of age, period 3: 46±53 days of age.
c
D: diet, P: period, D P: interaction diet period, RSD: residual standard deviation. Interaction D P
was only signi®cant (P < 0:01) for N retention expressed in % of daily gain.
d
Hemicellulose and cellulose are NDF±ADF and ADF±ADL, respectively, according to Van Soest et al.
(1991).
e
NS: nonsigni®cant.
f
Digestible energy.
g
Metaboilizable energy.
*
P < 0:05.
**
P < 0:01.
b
animals fed with the diet containing soya bean hulls the amount of retained nitrogen,
expressed as a percentage of intake or absorbed, was reduced by 14 and 10 percentage
units, respectively.
The analysis of the parameters used to control the digestive transit time (Table 7, Fig. 1)
shows a decrease in the transit time with the inclusion of 200 g of alfalfa per kilogram
diet. In mean terms, alfalfa almost doubled the chromium excretion rate (K). As a
consequence, the excretion time for 25 and 50% of the total chromium intake was
reduced by 13 and 22 h, respectively and the MRT was reduced by 15 h P < 0:01. In
78
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Table 5
Effect of dietary ®bre source on the fresh weight of the stomach, the small and large intestine and the intestinal
contents (g kgÿ1 live weight)
Dietsa
Statistical analysisb
Wheat
bran
Sugar beet
pulp
Soya bean
hulls
Alfalfa
meal
L
D
RSD
Stomach
Total
Empty
10.04
7.80 a
10.73
9.12 b
10.40
8.52 ab
10.21
7.79 a
NSc
NS
NS
1.44
0.76
Small intestine
Total
Empty
36.34 a
30.24 a
37.88 a
32.20 ab
42.37 b
35.02 b
36.33 a
30.34 a
*
*
NS
*
Large intestine
Total
Empty
32.28 a
15.68 a
31.77 a
18.42 b
43.33 b
18.51 b
32.35 a
13.76 a
NS
NS
**
Stomach content
Small intestine content
Large intestine content
Caecum content
2.24
6.11
16.60 a
2.63
1.61
5.68
13.35 a
1.87
1.88
7.35
24.82 b
2.96
2.41
6.00
18.59 a
1.20
NS
NS
NS
*
NS
NS
*
**
**
NS
3.33
2.56
5.53
2.19
0.99
2.01
4.94
1.05
a
Means with the same letters on the same line are not signi®cantly different.
L: litter, D: diet, RSD: residual standard deviation.
c
NS: nonsigni®cant.
*
P < 0:05.
**
P < 0:01.
b
addition, the soya bean hulls reduced the chromium excretion rate by 40% and delayed
the in¯exion point of the excretion curve by 11 h.
4. Discussion
4.1. Digestibility
The decrease in the daily growth rate and the increase in feed conversion veri®ed with
the incorporation of soya bean hulls in the weaning diet is associated with the decrease of
the digestible energy content of the diet (Table 4), which is in agreement with data
reported with the growing pig (Quiniou et al., 1999). Furthermore, once the diets were
balanced in total essential amino acids, the increase in the urinary nitrogen excretion with
the incorporation of soya bean hulls may be the result of a higher microbial production of
ammonia in the large intestine, which is then excreted as urinary urea (Ratcliffe, 1991).
The increase in DM digestibility with the use of sugar beet pulp may be a consequence of
its high level of digestible NDF, ADF, pectins and their constituent monosaccharides and
uronic acids (Longland et al., 1994). This result is in accordance with the high
fermentation level of this ®bre source, found not only in the growing pig (Graham et al.,
1986; Chabeauti et al., 1994) but also in the 6-week old piglet (Lizardo et al., 1997).
Table 6
Effect of dietary ®bre source on the concentration of VFAs and pro®le in the caecal contents at slaughter
Dietsa
Hemicellulose (NDF±ADF) (g kgÿ1)
Cellulose (ADF±ADL) (g kgÿ1)
Statistical analysisb
Wheat
bran
Sugar beet Soya bean
pulp
hulls
Alfalfa
meal
93.5
22.4
88.4
65.2
68.9
57.9
49.3
73.1
L
D
RSD
*
0.29
*
0.49
0.26
0.14
0.82
6.17 a
6.55 bc
6.28 ab
6.74 c
NSc
Concentration (mg g )
Acetic Ð C2
Propionic Ð C3
Butyric Ð C4
Total (C2 C3 C4 )
2.36 a
1.35
0.74 a
4.46 ab
2.11 a
1.09
0.60 ab
3.80 a
3.03 b
1.38
0.56 b
4.96 b
2.19 a
1.28
0.43 b
3.90 a
NS
NS
NS
NS
Molar proportions
C2/C3
C2/C4
C2/(C3 C4 )
C2/(C2 C3 C4 )
C3/(C2 C3 C4 )
C4/(C2 C3 C4 )
2.24 ab
4.91 a
1.53 a
0.604 a
0.272 ab
0.125 a
2.53 bc
5.46 a
1.71 a
0.631 a
0.252 bc
0.117 a
2.81 c
8.49 b
2.10 b
0.674 b
0.244 c
0.082 b
2.19 a
8.32 b
1.72 a
0.630 a
0.290 a
0.080 b
*
**
NS
NS
NS
**
*
**
NS
**
pH
ÿ1 d
NS
**
*
**
**
0.26
1.65
0.20
0.02
0.02
0.02
a
Means with the same letters on the same line are not signi®cantly different (n 6 piglets per diet).
L: litter, D: diet, RSD: residual standard deviation.
c
NS: nonsigni®cant.
d
VFA concentration (mg gÿ1 of caecal content).
*
P < 0:05.
**
P < 0:01.
b
Table 7
Effect of dietary ®bre source on the parameters of the mathematical model of chromium excretion
Dietsa
A (% of Cr intake)c
K (% Cr excreted per hour)e
In¯exion point (h)f
Cr 25% (h)g
Cr 50% (h)h
MRT (h)i
a
Statistical analysisb
Wheat
bran
Sugar beet
pulp
Soya bean
hulls
Alfalfa
meal
D
RSD
67.9
0.072 a
41.3 a
41.8 a
67.3 a
51.5 a
79.8
0.074 a
41.5 a
39.7 a
53.0 ab
49.9 a
79.9
0.056 a
49.0 b
46.2 a
61.3 a
56.9 a
75.7
0.123 b
30.3 c
29.8 b
36.8 b
37.7 b
NSd
14.0
0.02
6.91
7.04
16.33
6.38
Means with the same letters on the same line are not signi®cantly different.
D: diet, RSD: residual standard deviation.
c
Chromium recovered during the period 0 to 1.
d
NS: nonsigni®cant.
e
Chromium excretion rate.
f
In¯exion point of the chromium excretion curve.
g
Time (h) for recovery of 25% of the chromium intake.
h
Time (h) for recovery of 50% of the chromium intake.
i
Mean retention time.
*
P < 0:05.
**
P < 0:01.
b
**
**
**
*
**
80
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
Fig. 1. Effect of dietary ®bre source on the chromium excretion curves according to the prediction of the
mathematical model.
The lower TTAD of nitrogen (Table 4) for the soya bean hulls diet may be explained by
the presence of residual antitrypsin factors (Bengala Freire et al., 1991; Fan et al., 1995)
or by an increase in the microbial nitrogen faecal excretion (Stanogias and Pearce,
1985a). In fact, the presence of 50 g a-galactosides per kilogram soya bean hulls can be
used as an energy source by the gut micro¯ora with an increase in its fermentative activity
(Bengala Freire et al., 1991). Furthermore, the relatively low digestibility of cell walls
fractions of the wheat bran or alfalfa diets might be explained by their higher level of
lignin (Graham et al., 1986; Kass et al., 1980a). The signi®cant increase in the TTAD of
energy and ®brous components with the age of piglets seems to demonstrate a progressive
maturation of the digestive tract, which is in agreement with Longland et al. (1994).
4.2. Fermentative activity in the caecum
Considering the mean value for all diets, the levels of acetic, propionic and butyric acid
corresponded to 65, 25 and 10% of the total VFA, respectively. These values are in
accordance with previous data presented by Kass et al. (1980b) and Sauer et al. (1991).
The maximum level of total VFA was observed for soya bean hulls-based diet. This result
suggests a high degradation rate in the caecum, and is in agreement with the high
digestibility values of the NDF and ADF fractions. The relatively lower values of VFA
J.P.B. Freire et al. / Animal Feed Science and Technology 87 (2000) 71±83
81
measured in the sugar beet pulp diet could also be associated with a higher absorption
rate of its metabolites in the caecum. The higher level of butyric acid found in the caecum
content of the piglets fed with the wheat bran diet may be generated by small quantities of
endosperm that escape digestion in the small intestine and are fermented in the large
intestines, lowering the pH in the caecum. The VFA may also stimulate the epithelial
mucosa, changing the fresh weight of the small and the large intestine, particularly for the
diet based on soya bean hulls (Stanogias and Pearce, 1985b).
4.3. Digestive transit time
The mathematical model describing the chromium excretion ®ts the model reported by
Pond et al. (1986) comparing the use of different markers to describe the transit of
undigested materials in the growing pig. The alfalfa diet decreased not only the digestive
transit time but also the digestibility of the NDF and ADF fractions. These results
corroborate the hypothesis of Knudsen and Hansen (1991) that indicated an increase in
the transit passage with less degradable ®bres, due to their higher water holding capacity.
The delay in the in¯exion point of chromium excretion curve represented a slower
digestive transit. According to Knudsen and Hansen (1991), the use of soluble ®bres in
the diet such as sugar beet pulp may increase the viscosity of the intralumen contents of
the gut, delaying the digestive transit in the small intestine and completing the digestive
process in the piglet.
In conclusion, the effect of the sugar beet pulp on the digestible energy of the weaning
diet is minimized by the high degradation rate of its NDF and ADF fractions. On the other
hand, the soya bean hulls seemed to be less appropriate to the low digestive capacity of
the young pig, probably due to the presence of antitrypsin factors and a-galactosides.
Finally, among the four ®bre sources studied, the alfalfa meal was the most effective in
regulating the digestive transit time. However, its negative effect on the digestible energy
of the weaning diet must be considered before recommending its incorporation in the
starter diet of piglets.
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