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Effects of soybean curd residue silage on the
growth performance, meat quality, and cecal
microbial population in finishing pigs
Dang, Huy Quang; Kawahara, Satoshi; Tsugeta, MasaAki; Niimi, Mitsuhiro; Horinouchi, Shojiro;
Iwakiri, Masayoshi; Muguruma, Michio
日本暖地畜産学会報, 53(2): 145-155
http://hdl.handle.net/10458/3764
Date of Issue 2010-09
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Copyright © 2010 日本暖地畜産学会
JWARAS 53(2): 145-155, 2010
Original Article (Full Paper)
Effects of Soybean Curd Residue Silage on the Growth Performance,
Meat Quality, and Cecal Microbial Population in Finishing Pigs
Huy Quang DANG1, Satoshi KAWAHARA2,
Masa-aki TSUGETA3, Mitsuhiro NIIMI2, Shojiro HORINOUCHI4,
Masayoshi IWAKIRI4 and Michio MUGURUMA1,2
1
Interdisciplinary Graduate School of Agriculture and Engineering, University of Miyazaki, Japan
2
Faculty of Agriculture, University of Miyazaki, Japan
3
Yoghurt Feed Inc., Japan
4
Miyzaki Livestock Research Institute, Kawaminami br., Japan
(Received: 26 June 2010 / Accepted: 9 August 2010)
ABSTRACT
Soybean curd residue silage (SCRS) was incorporated into the diet of 24 crossbred (Landrace
× White × Duroc) finishing pigs at levels of 0 (control), 15, 30, and 60% for an experimental period of
60 days. The estimated total digestible nutrient intakes (TDN) did not differ among any treatments. The
growth performance of pigs did not differ significantly between the control and the 30% or 60% SCRS
groups, but growth decreased in the 15% SCRS group (P < 0.05). Pork derived from the pigs fed with 30%
or 60% SCRS showed a higher fat content (P < 0.05) and relatively lower shear force values. SCRS feeding
generally did not affect fatty acid composition of the pork, and consequently those melting points did not
differ among the dietary groups. Feeding SCRS to pigs positively impacted cecal microbiology by reducing
coliform, Enterobacteriaceae, and Escherichia coli numbers (P < 0.05). Thus, feeding of 30% and 60%
SCRS may contribute considerably to pig safety and pork quality.
Journal of Warm Regional Society of Animal Science, Japan 53(2): 145-155, 2010
Key words : cecal bacteria, finishing pig, meat quality, silage, soybean curd residue
Introduction
has developed a method for ensilage and preservation of
SCR (Tsugeta and Tsugeta 2007). Soybean curd residue
silage (SCRS) mixed with other dry feeds is successfully
resistant to aerobic deterioration and some pathogenic
microbe as Clostridium spp.
The contribution of SCRS to animal growth
performance and product quality must be evaluated. Some
researchers have reported that feeding of tofu cake silage
to swine did not affect the pig growth, and increased the
unsaturated fatty acid concentration in body fat (Niwa
and Nakanishi 1995). Osawa et al. (2004) have reported
that the meat from pigs fed fermented tofu cakes has
higher amounts of inter-muscle fat and tends to be tastier
compared with the meat from pigs fed conventional diets.
In addition, animal safety aspects of feeding materials
should be carefully considered, particularly in the context
of food-borne disease concerns. To the best of our
Approximately 700 thousand tons of soybean curd
residue (SCR), wastes from tofu industries, are generated
a year in Japan (Amaha et al. 1996). Since the act
concerning the promotion of utilization of recyclable
food waste, known as the food-recycle law, has become
effective in 2000, recycling of SCR has been of increasing
importance. Preparation of animal feeds with SCR is one
of the possible ways for its utilization (Barroga et al. 2000;
Tarachai and Yamauchi 2001).
Because raw SCR spoils quickly, it should be
preserved with appropriate means. While drying process
by heating is one of the solutions to the spoilage problem,
thermal drying of SCR results in loss of its nutrients
and huge energy costs. On the other hand, fermentation
strategy would be another method that has nutritional and
economical benefits (Martin 1996). Actually our colleague
Correspondence: Satoshi KAWAHARA(tel・fax: +81-(0)985-58-7204, e-mail: [email protected])
145
Dang HQ, Kawahara S, Tsugeta M, Niimi M, Horinouchi S, Iwakiri M, Muguruma M
knowledge, the bio-safety of SCRS to swine has not been
examined. Therefore, we investigated the effects of SCRS
feeding on growth performance, meat quality, and cecal
microbial populations in finishing pigs.
this experiment are shown in Table 2. At the end of the
designated experimental period, all pigs were slaughtered
over 14 days at a local commercial slaughterhouse. The
carcasses were assessed and graded according to the
standard of the Japan Meat Grading Association (Japan
Meat Grading Association 1988), and then the marbling
score was visually determined as specified by the National
Pork Board (National Pork Board 1999). After dressing
of the carcasses, meat samples (approximately 200 g each)
were collected from loin cuts. The meat samples were
vacuum-packed and stored at –30˚C until further analysis.
Shear Force Measurement
Cubic cuts of meat (approximately 30 g) were
enclosed in polyethylene bags and cooked in boiled
water to an internal temperature of 70˚C. Then, the cuts
were cooled for 30 min at room temperature (22˚C), and
the cooked meats were weighed on an electronic scale.
Cooking loss was calculated as the difference in sample
weight before and after cooking. Then, the shear force
of the meat cuts was measured with an Instron Universal
Testing Machine (Instron Japan Company Ltd., Kawasaki,
Japan) in which a Warner–Bratzler meat shear fixture was
installed.
Measurement of Fat Content and Fatty Acid Composition
Lipid extraction from meat samples was carried out
using the method described by Folch et al. (1957). The
lipid content of the total extracted lipid was determined
gravimetrically. Fatty acid methyl esters were prepared
using HCl/methanol as described (Takenoyama et al.
1999), and the resulting methyl esters were analyzed on
a GC–2010 gas chromatograph (Shimadzu Corporation)
equipped with a flame-ionization detector using a capillary
column (Supelcowax™ 10, 60 m × 0.32 mm i.d.; Supelco,
Inc., Bellefonte, PA, USA). The operating conditions of
the gas chromatograph were as follows: oven temperature
was held at 195˚C for 8 min, increased to 220˚C at a rate of
2˚C/min, and then held at this temperature for 40 min. The
temperature of the injector was 240˚C and of the detector
was 250˚C. The carrier gas (helium) was maintained at a
constant flow of 2.0 mL/min.
Melting Point Measurement of Subcutaneous Fat
To t a l f a t t h a t w a s p r e p a r e d b y h e a t i n g t h e
subcutaneous fat removed from the loin region to 80˚C was
used to measure the melting point. The sliding point of the
resulting fat was determined as the melting point by using
the method of the Japan Oil Chemists’ Society (2003).
Counting of Bacteria from Cecal Content
Samples from the cecum of the carcasses after
evisceration at the slaughterhouse were collected into
a sterilized polyethylene pouch. The pouch containing
Materials and Methods
Preparation of Soybean Curd Residue Silage
The SCR used in this study was provided by a
local tofu producer. The SCRS was prepared by mixing
wheat bran, barley, lucerne, and the SCR with fermented
tuberous taro as a starter culture (Tsugeta and Tsugeta
2007). The composition of the SCRS is shown in Table 1.
This mixture was stuffed in a polyethylene bag, protected
from the sun, and allowed to ferment for 1 month at room
temperature. Random samples of SCRS were collected
and subjected to chemical composition analysis of VFA,
volatile basic nitrogen (VBN), and pH. The chemical
composition, including concentrations of DM, crude
protein, crude fat, ash, and nitrogen-free extracts (NFE),
was determined according to the methods of the Fertilizer
and Feed Inspection Services of Japan (1983). The
concentrations of VFA such as acetic acid, lactic acid, and
butyric acid were determined with a GC–14B gas–liquid
chromatograph (Shimadzu Corporation, Kyoto, Japan)
equipped with a flame-ionization detector using a glass
column (160 × 0.3 cm) packed with polyethylene glycol
6000 according to a method of Kageyama et al. (1973).
The VBN was analyzed with the steam-distillation method,
which was followed by titration with 0.01 mol/L H2SO4.
To determine the pH, the silage was suspended in degassed
distilled water at 10% (w/v), and the pH was measured
with a pH meter (HM–30S; DKK–TOA Corporation,
Tokyo, Japan).
Animals and Diets
Twenty-four castrated pigs (Landrace × White ×
Duroc) were used to determine the effects of SCRS
feeding on animal growth performance, meat quality, and
characteristics of cecal microbes. The pigs were randomly
assigned to 1 of 4 treatment groups, i.e., 0% (control),
15%, 30%, and 60% SCRS-fed groups, and each treatment
group consisted of 2 pens (approximately 5.25 m2 each) of
3 pigs. The average age of the pigs at the beginning of the
experiment was 118 ± 1.8 days SD, and the average body
weight was 67.8 ± 1.1 kg SD. The animals were given
free access to experimental diets and to water ad libitum
for approximately 60 days. Treatment and management
of the animals were carried out according to the guidelines
for the care and use of experimental animals of the
Miyazaki Livestock Research Institute. The ingredients
and chemical composition of the finishing diets used in
146
Soybean curd residue silage feeding
Table 1 Composition of SCRS †
the sample was immediately placed into an oxygenimpermeant bag with an oxygen absorber (AneroPouch;
Mitsubishi Gas Chemical Company, Inc., Tokyo, Japan),
and the bags were closely sealed with an electric sealer.
All samples were then stored in an ice-cooled box until
further laboratory analysis.
A wet cecal sample (1 g) was suspended in a
stomacher bag containing 9 mL of 0.1% peptone water
containing 0.05 M sodium phosphate buffer, pH 7.2.
Multiple dilutions of the suspension were prepared with
0.1% buffered peptone water, and aliquots (0.1-1.0 mL)
of the dilutions were spread onto MRS agar (Oxoid Ltd.,
Hampshire, UK) for Lactobacilli, modified CCDA agar
(Oxoid Ltd.) for Campylobacter spp., TSC agar with egg
yolk (Oxoid Ltd.) for Clostridium spp., Pro-media Agar
Tricolor (Elmex Co., Ltd., Tokyo, Japan) for Escherichia
coli and coliform, Petrifilm™ EC for Enterobacteriaceae,
and EL Plates (Sumitomo 3M Ltd., Tokyo, Japan) for
Listeria spp. Pro-media Agar Tricolor plates, Petrifilm,
MRS agar plates and TSC agar plates were aerobically
incubated at 37˚C for 1–2 days (depending on colony
growth). Modified CCDA agar plates were incubated
37˚C for 1 day in a microaerophilic atmosphere with an
oxygen absorber (Anearo Pack–MicroAero; Mitsubishi
Gas Chemical Company, Inc.). The number of colonies
that grew on the plates was counted after cultivation, and
bacterial counts were determined.
Statistical Analysis
All data obtained in this study were analyzed with
analysis of variance (ANOVA). When significant effects
were observed from the F–test, we carried out a post–hoc
t–test (Tukey–Kramer’s test) to compare the means.
Parameters
Ingredient, % ‡
SCR
Fermented tuberous taro
Wheat bran
Barley
Lucerne
Chemical analysis
DM, %
NFE, % DM
Crude protein, %
Ash, % DM
Crude fat, % DM
Crude fiber, % DM
Lactic acid, %
Acetic acid, %
Butyric acid, %
pH
V score
Frieg score
35
25
20
10
10
46.9
60
19.1
5.3
4.2
11.5
1.89
0.09
0.04
< 4.7
97
100
† SCRS(soybean curd residue silage).
‡ As-fed basis.
< 0.05) observed between the C and the T2 or T3 diet.
Feed intake differed significantly between the T1 and T3
diets. Feed conversion was significantly higher (P < 0.05)
with the T1, T2, and T3 diets than with the C diet. Total
digestible nutrient intake and TDN conversion did not
differ significantly among the treatments. Similar results
have been noted in certain previous studies. For example,
Niwa and Nakanishi (1995) observed no difference in feed
conversion ratio or growth performance in fattening pigs
between control and groups fed 47% or 66% tofu cake
silage. Pigs fed a conventional diet showed greater weight
gain compared with pigs fed 100% tofu cakes (Osawa et
al. 2004).
The above findings suggest that SCRS does not
improve growth performance. The inferior growth
performance in pigs fed SCRS was probably due to the
nutritional imbalance of the diets, including the absence of
tryptophan in SCR as described by Tarachai et al. (1999).
However, a trend toward improved growth performance
with the levels of SCRS was observed. This improvement
may be due to fermented feed containing beneficial
bacteria that alter the gut environment of pigs (Hong and
Lindberg 2007), the organic acids in feed (Bach Knudsen
et al. 1991; Jensen 2001), the properties of the diet, and
the fraction of dietary fiber (Pedersen and Lindberg 2003).
The observation that the pigs consumed more feed with
Results and Discussion
As shown in Table 1, SCRS quality was assessed
based on the Frieg score (score = 100) and the V–score
(score = 97) (Takahashi et al. 2005), which indicated that
the SCRS has comparable quality as silage. Diets into
which SCRS was incorporated had lower crude protein
and ash than the conventional diet (Table 2). Dry matter,
TDN, and NFE decreased with the increasing proportion
of SCRS in the diets, whereas crude fat and crude fiber
increased with increasing levels of SCRS.
The effect on the growth performance of finishing
pigs fed SCRS is shown in Table 3. The daily gain (g/
day) was higher (P < 0.05) in pigs fed the C diet than in
those of both the T1 and T2 diets. The T3 group showed
an intermediate value between those dietary groups. Feed
intake was lowest with the C diet and increased with
the T1, T2, and T3 diets, with significant differences (P
147
Dang HQ, Kawahara S, Tsugeta M, Niimi M, Horinouchi S, Iwakiri M, Muguruma M
Table 2
Ingredient proportion and chemical composition of experimental diets
Parameters
Treatment †
C
T1
T2
T3
100
–
–
–
–
–
–
–
15.0
51.2
30.0
2.7
0.1
1.0
–
30.0
46.5
20.0
2.4
0.1
1.0
–
60.0
37.0
–
1.9
0.1
1.0
88.2
88.4
77.1
14.7
5.7
2.8
5.7
80.6
81.3
74.0
13.4
3.3
3.6
5.8
74.4
81.2
73.3
13.4
3.3
3.8
6.2
60.2
80.9
71.7
13.4
3.5
4.3
7.1
‡
Ingredient, %
Concentrate mixture
SCRS §
Corn
Wheat bran
Lucerne
Vitamin mix
Mineral mix
Chemical composition
DM, %
TDN, % DM
NFE ¶ , % DM
Crude protein, %
Ash, % DM
Crude fat, % DM
Crude fiber, % DM
† C(0% SCRS)
,T1(15% SCRS),T2(30% SCRS),T3(60% SCRS).
‡ As-fed basis.
§ SCRS(soybean curd residue silage).
¶ NFE(nitrogen-free extract).
Table 3
The effect on the growth performance of nishing pigs fed SCRS †
Treatment ‡
Parameters
Initial body weight(kg)
Final body weight(kg)
Daily gain(g/day)
Feed intake(kg of feed)
Feed conversion(kg intake /kg gain)
TDN intake(kg)
TDN conversion(kg intake/kg gain)
67.1
118.5
923
162.2
3.2
126.3
2.46
C
±
±
±
±
±
±
±
2.3
5.9a
97a
11.7a
0.3a
9.1
0.3
68.1
102.6
560
194.8
6.1
127.7
4.03
T1
±
±
±
±
±
±
±
2.1
8.3b
173b
20.0ab
2.3b
13.1
1.5
68.3
107.0
643
224.7
6.0
135.6
3.60
T2
±
±
±
±
±
±
±
2.9
9.5ab
175b
28.0bc
1.3b
16.9
0.8
67.6
112.2
764
254.6
5.8
127.7
2.9
T3
±
±
±
±
±
±
±
2.4
7.4ab
145ab
50.3c
1.3b
25.2
0.7
Values are means ± standard deviations of the means.
† SCRS(soybean curd residue silage).
‡ C(0% SCRS)
,T1(15% SCRS),T2(30% SCRS),T3(60% SCRS).
a,b,c Within a row, means without a common superscripts differ statistically(P<0.05).
increasing SCRS levels could be explained in several
ways: (i) an improvement in physical characteristics and
palatability of the SCRS diet (Niwa and Nakanishi 1995),
(ii) the low CP and TDN of the diet (Ikeda et al. 2005),
and (iii) the higher dietary fiber, resulting in decreased
digestibility and metabolic energy of the diet. Pigs may
consequently attempt to consume more feed to maintain
the digestible energy intake (Baird et al. 1975; Kennelly
and Aherne 1980; Low 1985; García et al. 1999). Thus,
our data suggest that diets containing 30% or 60% SCRS
could be fed to finishing pigs.
Feeding of SCRS to pigs altered both the carcass
traits and the pork quality (Table 4). The carcass weight
was significantly lower (P < 0.05) with the T1 and T2
diets compared to the C diet, but this was not the case
with the T3 diet. However, SCRS feeding did not affect
carcass yield (%) or subcutaneous fat thickness (cm)
in either the outer or inner levels. For pork quality, no
noticeable differences were observed in the pork color
standard number (PCS No.), pork-fat color standard
number (PFS No.), marbling score, or cooking loss (%)
among the groups. The shear force value was significantly
148
Soybean curd residue silage feeding
Table 4
The effect on carcass traits and pork quality of nishing pigs fed SCRS †
Parameters
Carcass weight(kg)
Carcass yield(%)
Subcutaneous fat(cm)
Outer layer thickness
Inner layer thickness
PCS No(1 – 6)§
PFS No(1 – 4)¶
Marbling score(1 – 6 & 10)
Cooking loss(%)
Shear force(kg)
Treatment ‡
C
81.4 ± 6.1a
63.0 ± 2.7
T1
64.7 ± 7.1b
64.5 ± 1.6
T2
68.9 ± 4.9b
64.8 ± 4.9
T3
72.7 ± 6.7ab
68.5 ± 1.8
3.6
2.7
2.7
1.0
1.8
32.7
6.8
3.0
2.2
2.9
1.3
2.2
30.1
5.3
3.1
2.3
3.1
1.1
2.7
32.7
5.1
3.2
2.3
2.8
1.3
2.1
32.7
5.9
±
±
±
±
±
±
±
0.4
0.4
0.8
0.1
0.8
1.3
0.6a
±
±
±
±
±
±
±
0.5
0.5
0.2
0.5
0.6
2.2
1.2ab
±
±
±
±
±
±
±
0.3
0.3
0.4
0.2
0.8
1.8
1.2b
±
±
±
±
±
±
±
0.5
0.3
0.3
0.4
0.4
2.4
0.7ab
Values are means ± standard deviations of the means.
† SCRS(soybean curd residue silage).
‡ C(0% SCRS)
,T1(15% SCRS),T2(30% SCRS),T3(60% SCRS).
§ PCS No(pork color standard number).
¶ PFS No(pork fat color standard number).
a,b Within a row, means without a common superscripts differ statistically(P<0.05).
lower (P < 0.05) with the T2 diet and marginally but not
significantly lower (P > 0.05) for the T1 and T3 diets when
compared with the C diet. Oshawa et al. (2004) observed
no significant differences in the fat color of meat from pigs
fed tofu cake when compared with the control group, in
agreement with our current results. They also noted that
the meat from pigs fed tofu cake tended to be tastier.
Because our data indicated a decrease in the amount
of meat (carcass weight) as a consequence of weight
gain, the quality parameters of the meat appeared to be
improved with a tendency toward less subcutaneous fat,
increased carcass yield, increased PCS No., increased PFS
No., and in particular, a greater marbling score and lower
shear force value in pigs fed SCRS compared with those
fed the normal diet. Nevertheless, those parameters were
not statistically significant except for the shear force value.
Thus, we suggested that a diet containing SCRS improves
pork quality.
The fat and fatty acid characteristics of the meat
from finishing pigs fed SCRS are shown in Table 5. No
significant differences in both saturated fatty acids (SFA)
and monounsaturated fatty acids (MUFA) were observed
among the diets. On the other hand, total polyunsaturated
fatty acids (PUFA) was lower (P < 0.05) in pigs fed the
T2 or T3 diet as compared to those fed the C or T1 diet.
Consequently, the PUFA/SFA ratio was less (P < 0.05) in
pigs fed the T2 or T3 diet than in those fed the C or T1
diet. The PUFA mainly decreased in the T2 and T3 groups
was n-6 fatty acids such as linoleic and arachidonic acids.
The ratio of n–6/n–3 was slightly lower in pigs fed the T2
or T3 diet compared with those fed the C or T1 diet. The
fat content (g/100 g meat) was higher (P < 0.05) in pigs
fed the T2 or T3 diet than in those fed the C or T1 diet. In
addition, there was no significant difference among the
groups with respect to the melting point of fat.
Niwa and Nakanishi (1995) reported that tofu cake
silage led to increased unsaturated fatty acids and lower
body fat melting points in fattening pigs. Surprisingly,
Osawa et al. (2004) indicated that meat from pigs fed
tofu cake had higher inter-muscle fat and higher body fat
melting points. On the other hand, the melting point of
the fat in our experiment did not differ among pigs fed the
various treatments, although we observed a lower total
PUFA and PUFA/SFA ratio in pigs fed diets containing
30% or 60% SCRS than in those fed diets with 15% SCRS
or a conventional diet. The differences in fat melting
points between previous reports and our findings may be
due to differences in fatty acid composition because fats
containing different fatty acids have different melting
points (Wood et al. 2008). The meat from pigs fed 30%
or 60% SCRS had a higher fat content compared with
diets containing 15% SCRS or the commercial ration.
Huff-Lonergan et al. (2002) reported that increased lipid
content in pork improves its firmness and the sensory
characteristics involved in flavor. Furthermore, Brewer
et al. (2001) reported that consumers evaluated highly
marbled pork with fat, i.e., more fatty pork, to be more
tender, juicy, and flavorful. Therefore, inter-muscle fat
content is a remarkable characteristic of pork.
It is well known that dietary nutrition for animals
149
Dang HQ, Kawahara S, Tsugeta M, Niimi M, Horinouchi S, Iwakiri M, Muguruma M
Table 5
The effect on fat and fatty acid proles in meat from nishing pigs fed SCRS †
Treatment ‡
Parameters
Fatty acid composition(wt %)
C14:0
C16:0
C16:1 n-7
C18:0
C18:1 n-9
C18:2 n-6
C18:3 n-3
C20:4 n-6
Total SFA
Total MUFA
Total PUFA
PUFA/SFA
n–6/n–3
Fat content(g/100g meat)
Melting point(˚C)
C
1.1
25.0
2.4
14.1
46.3
6.6
0.15
0.85
40.6
51.5
7.9
0.195
54.2
5.3
33.4
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
T1
0.3
1.3
0.3
0.7
2.2
0.6a
0.02
0.08ab
1.3
1.2
0.7a
0.020a
3.4a
0.6a
1.1
1.1
25.4
2.9
13.8
46.1
6.4
0.14
0.89
40.8
51.5
7.8
0.191
53.8
5.4
33.3
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
T2
0.1
0.4
0.4
1.1
1.7
1.1a
0.03
0.15a
0.7
1.8
1.3a
0.031ab
5.4a
1.1a
0.7
1.1
25.5
2.6
14.1
47.7
5.0
0.15
0.68
41.2
52.7
6.1
0.149
39.6
7.8
32.7
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
T3
0.1
0.8
0.3
0.8
1.2
0.5b
0.01
0.13b
1.6
1.2
0.7b
0.022b
2.4b
1.2b
1.5
1.2
25.9
2.8
13.2
47.7
5.0
0.20
0.67
40.7
53.1
6.2
0.152
30.8
7.3
32.7
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
0.2
0.9
0.4
0.6
1.2
0.8b
0.05
0.12b
1.1
1.5
1.0b
0.024b
4.3b
1.1b
0.7
Values are means ± standard deviations of the means.
† SCRS(soybean curd residue silage).
‡ C(0% SCRS)
,T1(15% SCRS),T2(30% SCRS),T3(60% SCRS).
a,b Within a row, means without a common superscripts differ statistically(P<0.05).
affects their meat quality. A number of studies have shown
substantial increase in intramuscular fat from feeding
protein-deficient diets to pigs (Ellis and McKeith 1999).
Da Costa et al. (2004) indicated that restriction of dietary
proteins results in the accumulation of significantly more
intramuscular fat in both longissimus thoracis muscle and
psoas major muscle in growing pigs. They supposed that
low protein intake restricts muscle growth, resulting in
surplus energy being converted into intramuscular lipids.
In our study, the levels of crude protein as-fed basis in
the experimental diets were 13.0% (C diet), 10.8% (T1
diet), 9.97% (T2 diet), and 8.09% (T3 diet), respectively.
The decreased protein level in the SCRS-contained diets
seems to be one of possible explanation for significant
increase of intramuscular fat in the pigs. In addition,
feeding of reduced protein diet to growing/finishing pigs
have increased protein expression level of stearoyl-CoA
desaturase in longissimus thoracis muscle, resulting in
elevating level of MUFA in the muscle (Doran et al. 2006).
In the present study, the SCRS feeding tended to increase
the level of MUFA in pork loin. This modification of
MUFA level in meat may ease a drastic alteration in
melting point of the fat.
The ratio of n-6 to n-3 essential fatty acids is an
important indicator for evaluating the nutritional quality
of food lipids, and an n-6/n-3 ratio less than 4:1 is
generally preferred (Loh et al. 2009). In the current study,
feeding SCRS (30% or 60%) to finishing pigs resulted
in a decreased n-6/n-3 ratio in the meat lipids, although
the value of 30.8 ± 4.3 (T3 diet) was still higher than
that of the recommended value. If the balance of n–6
and n-3 fatty acids in pork was improved, which could
lead to greater nutritional profiles of the meat. Further
investigation involved in lipid nutrition of pork is needed
to enhance marketable value of the pork.
The bacteriological profile of the cecal content of
finishing pigs was modified by dietary SCRS (Figure
1). Both coliform and E. coli numbers (log CFU/g)
decreased dramatically (P < 0.05) in pigs fed the T1,
T2, or T3 diet compared with those fed the C diet. The
Enterobacteriaceae counts (log CFU/g) were significantly
lower (P < 0.05) in pigs fed the T1 diet, but not statistically
lower in pigs fed the T2 or T3 diet compared to those
fed the C diet. There were no significant differences
in the numbers of other bacteria (log CFU/g) such as
Campylobacter spp. However, Lactobacilli counts (log
CFU/g) were slightly higher in pigs fed the T1, T2, or
T3 diet compared to pigs fed the C diet. Meanwhile,
Clostridium spp. and Listeria spp. were not detected in all
the dietary groups.
There are no published reports on the effects of
SCRS feeding to pigs on the bacterial population in the
150
Mean of bacterial number (logCFU/g)
Soybean curd residue silage feeding
Figure 1 Bacterial numbers in the cecal content of pigs fed SCRS. From left to right, each group of 4 bars
represents C (Control), T1 (15% SCRS), T2 (30% SCRS), and T3 (60% SCRS) diets. Within groups, means
without a common superscript differ statistically (P < 0.05).
Table 6
The approximate estimate of economic aspects of pork production by means of SCRS † feeding
Parameters
§
Price of feed(yen/kg)
¶
Feed cost per animal(yen/head)
Carcass price(yen/carcass)
Unit price of carcass(yen/kg)
Percentage of feed cost in carcass price
Treatment ‡
C
60.17
9748 ± 705
28081 ± 3423
348 ± 58
35.1 ± 4.3
T1
52.37
10203 ± 1047
23810 ± 5646
364 ± 56
45.6 ± 14.9
T2
48.47
10890 ± 1359
28466 ± 2028
413 ± 10
38.5 ± 6.4
T3
40.67
10356 ± 2046
28436 ± 2521
393 ± 58
36.4 ± 6.3
Values are means ± standard deviations of the means.
† SCRS(soybean curd residue silage).
‡ C(0% SCRS)
,T1(15% SCRS),T2(30% SCRS),T3(60% SCRS).
§ Values are prices in fiscal year 2007.
¶ Values show only costs of the experimental feeds during experiment.
gastrointestinal tract (GIT). However, numerous works
on feeding fermented feed to pigs have noted changes
in GIT microbial ecology, including a reduction in
Enterobacteriaceae, coliform, E. coli numbers, and/or an
increase in lactic acid bacteria (LAB) counts (Prohaszka et
al. 1990; Ravindran and Kornegay 1993; du Toit et al. 1998;
van Winsen et al. 2001, 2002; Demecková et al. 2002). A
reduction in the amount of enteropathogenic bacteria of the
Enterobacteriaceae family may be due to events that occur
during the fermentation process as follows: (i) competition
for receptor sites of lactobacilli ingested from fermented
feed (Mulder et al. 1997), (ii) lactic acids and VFAs created
by LAB and fermented feed (Prohaszka et al. 1990), (iii)
antimicrobial compounds produced by LAB (Apella et al.
1992; Olsen et al. 1995), (iv) low pH (Burnell et al. 1988;
Ravindran and Kornegay 1993), and (v) a combination
of these factors. In addition, the activity of bacteriocin
in fermented taro could be another factor that reduces
pathogenic bacteria (Muller et al. 2005). Therefore, the
fermentation process of SCRS in our experiment may have
induced the events mentioned above and may therefore be
responsible for the changes in the cecal bacteria profile of
the pigs. The reduction in Enterobacteriaceae, coliform,
and E. coli numbers caused by feeding SCRS suggests
151
Dang HQ, Kawahara S, Tsugeta M, Niimi M, Horinouchi S, Iwakiri M, Muguruma M
that SCRS feeding is safe to swine and produces a lower
contamination level of enteropathogenic bacteria in the
GIT.
Unit price of the SCRS used in this study was
approximately half of the C diet. Thus, the prices of the
experimental feeds fell with increasing amounts of added
SCRS to feed (Table 6). However, the costs for each feed
during finishing were higher in the SCRS-fed groups than
in the C group because the feed intake increased in the
SCRS-fed group (Table 3). On the other hand, carcass
price were almost same between the C, T2, and T3 groups.
The feed costs of those diets represented from 35 to 40
percent of each carcass price. These results suggest that
use of the SCRS for pork production does not directly
bring in pecuniary profit, while SCRS-preparation as a
mean of food recycling could save huge energy costs.
Ellis and McKeith (1999) noted that poorly balanced feeds
reduce feed efficiencies and would be uneconomic in most
situations. Further investigations to improve nutrition of
SCRS-containing feeds are needed.
In conclusion, our results suggest that utilization of
SCRS in feed for finishing pigs increases feed intake but
does not change TDN intake. The growth performance
did not differ significantly when pigs were fed 30% or
60% SCRS, but decreased when pigs were fed 15% SCRS.
Feed containing SCRS improved the quality of the meat,
as measured by a higher fat content and lower shear force,
whereas feeding of SCRS to pigs almost did not affect fatty
acid composition and melting point of the meats. Our data
particularly suggests that incorporation of SCRS, even at a
low level, had beneficial effects on cecal microbiology with
a reduction in the Enterobacteriaceae population, coliform
count, and E. coli number. Thus, SCRS may be interesting
for bio-utilization as feed for finishing pigs when animal
health and meat quality are the main objectives.
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Acknowledgement
This study was supported by a program of technological
development for recycling from the Miyazaki Prefectural
Industrial Support Foundation.
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要 約
オカラサイレージの給与が豚の発育成績,肉質,
および盲腸内微生物数に及ぼす影響
Huy Quang DANG1・河原 聡 2・告田政秋 3・新美光弘 2・
堀之内正次郎 4・岩切正芳 4・六車三治男 1,2
1
3
宮崎大学大学院農学工学総合研究科・2 宮崎大学農学部・
株式会社ヨフルトフィード・4 宮崎県畜産試験場川南支場
連絡者:河原 聡
(tel・fax: 0985-58-7204, e-mail: [email protected][email protected]、宮崎県内で発生した豆腐製造残さ(オカラ),親サトイモ
発酵物等を混合した後、バッグ内で乳酸発酵させてオカラサイレージを調製した。さらに、このオカラサイレー
ジを 15%,30% および 60% 含有し、トウモロコシ等で粗タンパク質量を調整した試験飼料を作製した。これら
の飼料を仕上期の肥育豚に 60 日間自由摂食させた。同時に市販配合飼料を給与する試験区も設け、生産性の
比較等を行った。肥育豚の発育成績はオカラサイレージ 15% 給与区のみが他の 3 区と比較して有意に低下した
(P<0.05)
。サイレージ 30% 区および 60% 区のロース肉は、他の 2 区のそれと比較して、脂肪含量が高く、剪断
力価が低くなった。また、オカラサイレージの給与はロース肉の脂肪酸組成に明確な影響を及ぼさず、脂肪融
点について試験区間で有意な差を認めなかった。また、他の 2 区と比較して、サイレージ 30% と 60%給与区で
は多価不飽和脂肪酸/飽和脂肪酸比および n-6/n-3 比が若干低下した。また、市販配合飼料を給与した豚と比較
して、オカラサイレージを給与した豚の盲腸内容物では大腸菌群,エンテロバクター科細菌,および大腸菌の
菌数が有意に減少した(P<0.05)。以上の結果から、オカラサイレージの肥育豚への給与は豚肉の品質を低下さ
せず、肥育豚の衛生状態を改善できることが示唆された。
日本暖地畜産学会報 53(2): 145-155, 2010
キーワード:オカラ,サイレージ,肉質,肥育豚,盲腸内微生物
155