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African Journal of Pig Farming ISSN 2375-0731 Vol. 2 (2), pp. 001-004, February, 2014. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 

 

Full Length Research Paper 

 

Comparative utilization of two sources of expeller-

extruded soybean meal as a replacement for on-farm 

processed soybean in diets of growing-finishing pigs 

 
Adesehinwa A. O. K. 

 
Institute of Agricultural Research and Training, Obafemi Awolowo University, P.M.B. 5029, Moor Plantation, 

Ibadan. Nigeria. E-mail: aokadesehinwa@gmail.com 
 

Accepted 03 October, 2013 
 
Thirty pigs averaging 30 ± 1.1 kg were randomly assigned by origin and weight to one of three dietary treatments in a 
randomized complete block to determine the comparative utilization of two sources of expeller-extruded soybean 
meal as a replacement for on-farm processed soybean in diets of growing-finishing pigs. The result revealed that 
pigs fed diets containing the expelled soybean meal (ESM) had decreased (P<0.05) average daily gain (ADG) 
compared to pigs fed the on-farm processed soybean resulting in between 13-17% reduction in the ADG. The 
expelled soybean meal samples resulted in comparable (P>0.05) gains even though slight numerical differences were 
observed. Feed efficiency was 18 to 24% significantly (P<0.05) poorer for pigs fed the expelled soybean meal diets 
compared to the improvement observed in the feed conversion of pigs when fed the on-farm processed soybean. 
Conclusively, the gains as well as the efficiency of feed utilization obtained with the on-farm processed soybean 
were significantly (P<0.05) superior compared to the expeller- extruded soybean but the serum metabolites of the 
pigs were observed to be unaffected by the different processing methods. 
 
Key word: Expeller-extruded soybean, On-farm processed soybean, pigs, soybean processing, performance, serum 

metabolites 

 
INTRODUCTION 

 
Fish meal (FM) is presently the most expensive animal 
protein source in animal feeds (Tacon, 1993). The 
increasing costs and unpredictable availability of FM 
necessitates the search for its replacement with cheaply 
and abundantly available plant protein feed stuffs 
(Robinson and Menghe, 2007). Recent research trends 
indicate that there is an increased interest towards the 
search for alternative/additional protein source to meet 
the increasing requirements for protein source for the 
expanding livestock industry, especially in the developing 
countries (Janardhanan et al., 2003). Even though 
soybean and other common legume grains play a key 
role as protein source for human beings and animals 
alike, their production is not sufficient to meet the protein 
requirements of the increasing population and expanding 
livestock industries (Vijayakumari et al., 2007). The heavy 
demand for these common legumes has given rise to a 
disproportionate increase in their prices, and conse-
quently, the cost of the food and feedstuffs into which it is 

 
 
 
 
incorporated. 

Use of raw soybean is limited due to the presence of 
endogenous and heat-labile anti-nutritional factors 
(ANFs) that is, lectin, phyto-haemoglutinin, anti vitamins 
and protease (trypsin) inhibitors (Liener, 1980). The most 
important of which are trypsin inhibitors, which seriously 
impair protein digestibility (Balloun, 1980). There are both 
heat stable (saponins, tannins, estrogens, phytate) and 
heat-labile (protease inhibitors) in soy. Protease inhibitors 
in soy are destroyed by heating but other factors also 
play a role, such as duration of heating, particle size and 
moisture conditions. Thus, how soy products are 
processed will dictate how much of the protease inhibitor 
(also known as trypsin inhibitor) remains. The nutritive 
value of the protein in soybean actually increases with 
heating which destroy trypsin inhibitors (Weingartner, 
2008). Roasting or cooking of raw soybean to a tempe-
rature of 240-260 degrees Fahrenheit for 3 to 5 min 
destroys this inhibitor and ensures the utilization of soy- 



     

Table 1. Diet Composition.      
      

 On-Farm Processed Expelled Soybean Expelled Soybean   

Ingredient % Soybean meal a(43%) meal b(41%)   

Maize 30.00 29.30 28.54   

Maize Offal 12.00 12.00 12.00   

Soybean meal (45%) 15.00 - -   

Expelled soybean meal - 15.70 16.46   

Palm kernel Cake 20.00 20.00 20.00   

Wheat Bran 20.00 20.00 20.00   

Bone meal 2.25 2.25 2.25   

Vit-Min. premix 0.25 0.25 0.25   

Salt 0.50 0.50 0.50   

Total 100.00 100.00 100.00   

Calculated: Crude Protein 17.95 17.95 17.95   

ME Kcal/Kg 2773 2738 2735   

 

 

bean as a protein supplement (Vijayakumari et al., 2007). 
Development of new processing technologies for the 
removal of ANFs has facilitated its increased use as 
protein source in feeds (Garg et al., 2002) . Therefore, for 
the elimination of ANFs, soybean seeds ( Glycine max) 
could be hydrothermically processed before incorporating 
in diets. Soybean meal (SBM) can be produced either by 
solvent extraction or expeller-extrusion. Expeller-extruded 
SBM (EE-SBM) contains more oil but less crude protein 
than solvent extracted SBM (SE-SBM) (Powell et al., 
2007). However, results of experiments indicate that EE-
SBM had similar feeding value to SE-SBM when the 
differences  in  nutrient  values  are  considered  in  diet  
formulation. 

Presently, solvent extraction is the most common 
method of extracting soybean oil today; leaving less than 
1% fat, but, the expeller process is still the most 
commonly used industrial method in Nigeria (Fashina, 
1991). This experiment was therefore conducted to deter-
mine the replacement value of expeller-extruded soybean 
meal for on-farm processed soybean in diets of growing-
finishing pigs. 
 

 
MATERIALS AND METHODS 
 
Expeller-extruded soybean meal was purchased at two local 
industrial sales outlets in Ibadan, Nigeria. The two samples of 
expelled soybean meal and the on-farm processed soybean were 
analyzed for percentage protein (AOAC, 1990) and diets formulated 
to be isonitrogenous and isocaloric (Table 1). In the expeller pro-
cess, the soybean are cracked, dried, and transported to a tempting 
device, which stirs them for uniform heat processing. The soybeans 
are then fed into an expeller barrel, which presses the oil from the 
beans. The soybeans leave the barrel and are ground. The expell-
er process leaves the beans with approximately 5% fat. However, 
boiling of soybean is the most conventionally and commonly used 
farm-adaptable processing method in Nigeria (Awosanmi, 1988). 
Raw soybean packed in jute bags is lowered into half-drum of 
boiling water and allowed to boil for a time-period. The boiled seeds 
are then drained of water and sun-dried to less than 10% moisture 

 

 
content before being ground and stored (Fanimo, 1996). 

The metabolisable energies were also determined with the 
equation predicted by Morgan et al. (1975). ME = 0.416CP + 

0.605EE + 0.367NFE – 20.06 (R
2
 = 0.94) where ME is the 

metabolizable energy, CP is the crude protein, EE is the ether 
extract and NFE is the nitrogen free extract. Lysine was assumed to 
be a fixed percentage of total protein in both soybean meals. The 
arrangement of treatments allowed for a direct comparison of the 
protein quality of the two expelled-soybean meal sources to the on-
farm processed soybean, as well as assessing the effect of the 
potential variation in protein on pig performance. Thirty pigs 
averaging 30 ± 1.1kg were assigned randomly by origin and weight 
to one of three dietary treatments in a randomized complete block. 
In each of the treatment groups, there were five replicates of two 
pigs per replicate. The pigs were allowed assess to feed and water 
ad libitum for a 42-day period.  

Five of the ten experimental grower pigs in each of the three 
dietary treatments were randomly selected and bled at the end of 
the feeding trial. The bleeding was done in the morning before 
feeding and 10ml of the blood was obtained from the jugular vein 
into a sample bottle using a sterilized needle and syringe as 
described by Adesehinwa (2007). The samples were allowed to clot 
before centrifuging to obtain the serum used in the determina-tion of 
some serum metabolites (Total protein, Albumin, Globulin, Urea 
nitrogen, Creatinine, Cholesterol and Glucose) using methods 
described by Toro and Ackermann (1975) and Kaneko (1989).  

All the data obtained were subjected to analysis of variance and 
where statistical significance were observed, the means were 
compared using the Duncan’s Multiple Range (DMR) test. The SAS 
Computer software package (1988) was used for all statistical 
analyses. 
 

 

RESULT AND DISCUSSION 

 

Pigs fed diets containing the expelled soybean meal 
(ESM) had decreased (P<0.05) average daily gain (ADG) 
compared to pigs fed the on-farm processed soybean 
(Table 2) resulting in between 13 - 17% reduction in the 
ADG. This could be attributed to a suspected higher fat 
content of the on-farm-processed soybean, which may 
have resulted in the higher caloric density of the diet, 
since, it was not defatted. The expelled soybean meal 



           
 

   Table 2. Effect of expelled soybean meal on pig performance.      
 

              
 

      On-Farm Processed Expelled Soybean Expelled Soybean   
 

   Ingredient, %   Soybean  meal a(43%CP)  meal b(41% CP) CV  
 

   Daily gain, kg   0.76
a
  0.66

b
  0.63

b
 6.7  

 

   Daily feed intake, kg  2.43  2.48  2.51  8.7  
 

   Feed efficiency   3.27
b
  3.59

a
  3.73

a
 9.0  

 

   a,b: Means along the same row having different subscripts differ significantly at P<0.05   
 

  Table 3. Serum Metabolites of growing Pigs fed two sources of expeller-extruded soybean.   
 

          
 

  Metabolites  On-Farm Processed Expelled Soybean Expelled Soybean meal 
b
  ±SEM 

 

     
Soybean 

 

meal a (43%CP) 
 (41%)    

 

           
 

  Total Protein (g/dl)    6.49  6.30  6.36  0.05  
 

  Albumin (g/dl)    3.75  3.99  3.68  0.02  
 

  Globulin (g/dl)    3.35  3.31  3.29  0.03  
 

  Urea N (mg/dl)  44.13  41.25  43.38  1.84  
 

  Creatinine (mg/dl)    1.49  1.57  1.44  0.05  
 

  Cholesterol (mg/dl)  277.00  266.62  263.5  6.06  
 

  Glucose (mg/dl)  85.13  84.46  90.13  2.75  
 

 

 

samples resulted in comparable (P>0.05) gains which 
was significantly inferior to gains obtained with the on-
farm soybean. The average daily fed intake was not 
significantly influenced by the different soybean samples, 
in accordance with the findings of Awosanmi (1988) and 
Bamgbose (1988), that processing of soybean may not 
affect the feed intake. Hayward et al. (1953) had earlier 
reported inability of processed oilseed meals to promote 
good growth as not due to a lack of feed intake but 
difference in the nutritional value of their protein as a 
result of methionine deficiency. Hence, it could be 
inferred that the nutritional value of the resultant protein 
contained in the on- farm processed soybean used in this 
study was superior to the expelled soybean taking into 
consideration the superior gains observed. Balogun 
(1979) reported methionine deficiency in the rations of 
pigs to cause amino acid imbalance with consequent 
adverse effect on performance. Feed efficiency was 18 to 
24% significantly (P<0.05) poorer for pigs fed the 
expelled soybean meal diets compared to the improve-
ment observed in the feed conversion of pigs when fed 
the on-farm processed soybean. However, the replace-
ment of the on-farm processed soybean with the expeller-
extruded soybean resulted in neither beneficial nor 
adverse effect on the serum parameters. These results 
indicated that the expelled soybean meal used in this 
experiment was an inferior protein source compared to 
the on-farm-processed soybean due to the comparative 
adverse animal performance in terms of feed efficiency 
and weight gains.  
The effect of expeller-extruded soybean protein sources 

on the serum metabolites of the pigs is shown in Table 3. 

 

 

The serum total protein, albumin and globulin of the pigs 
were observed to be unaffected by the different 
processing methods. These parameters are indications of 
protein reserves in animals (Adesehinwa, 2007) and can 
be specifically influenced by protein shortage indicated by 
alterations in albumin content (Gouache et al., 1991). The 
result of this study showed that the protein levels and the 
amino acid profiles of the isonitrogenous diets were able 
to support normal protein reserves in the experimental 
pigs. The influence of diets on haematological and serum 
biochemical variables have been established (Ologhobo 
et al., 1993; Otesile et al., 1991). 

The observed values were within the range reported by 
Kaneko (1989) for this class of pigs. This could have 
been brought about by the efficient utilization of the 
soybean proteins contained in the diets thereby resulting 
in comparable (P>0.05) values. However, the gains as 
well as the efficiency of feed utilization obtained with the 
on-farm processed soybean were significantly (P<0.05) 
superior compared to the expeller-extruded soybean. It 
should be noted that the crude protein content of cakes 
have been reported to be dependent on the extent of 
dehulling and the efficiency of the oil extraction process 
(Villamide and San Juan, 1998). The efficiency of 
utilization of any protein source is affected by the level of 
protein in the diet, the digestibility of the protein, and the 
levels of essential amino acids, particularly the first 
limiting amino acid - lysine (Maina et al. 2002).  
The economic feasibility of feeding extruded soybeans to 

swine is affected by the differences in nutrient content 

compared to soybean meal, the need to increase the 

protein in diets containing whole soybeans, the value of 



 
 
 

 

extra fat and the cost of processing (Hollis, 2008). 
 

 
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