




































In ternationa l
Scholars
Journa ls

 

African Journal of Pig Farming ISSN 2375-0731 Vol. 4 (12), pp. 001-010, December, 2016. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 

 

Review 

 

Potential of bacterial fermentation as a biosafe 

method of improving feeds for pigs and poultry 
 

A. T. Niba1*, J. D. Beal2, A. C. Kudi2 and P. H. Brooks2
 

 
1
Department of Animal Production, University of Dschang, P. O. Box 447, Dschang, Cameroon. 

2
Faculty of 

Science, School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth, Devon PL 4 8AA, 
United Kingdom. 

 

Accepted 6 February, 2009 
 

The use of fermented liquid feeds in monogastric animal nutrition is regarded as one of the biosafe methods of animal 
production. This paper examines bacterial fermentation of feed substrates for production of fermented liquid feeds for 

pigs and moist feeds for poultry. Emphasis is placed on the interplay of factors affecting feed fermentation and their 
relationship to feed quality. The resistance of fermented feeds to enteropathogenic contamination prior to feeding and 

their potential contribution to African agriculture is highlighted. 
 

Key words: Fermented liquid feed technology, pigs, poultry. 

 
INTRODUCTION 

 
There is considerable concern over the use of antibiotic 
growth promoters (AGPs) in animal production. Their 
extensive usage has resulted in the selection for survival of 
resistant bacteria species or strains (Doyle, 2001; Montagne 
et al., 2003; Khaksefidi and Rahimi, 2005). This resistance 
can be transferred to other previously susceptible bacteria 
and can be hazardous to both animal and human health 
(Montagne et al., 2003).  

The use of in-feed AGPs has been banned in the 

European Union (Wilkie et al., 2005; Williams et al., 2005) 

and there are further attempts to reduce or remove in-feed 

AGPs worldwide (Jin et al., 1998; Yegani and Korver, 2008) 

. This would have significant implications on gut microbial 

profiles (Yegani and Korver, 2008) as well as increase 

competition between gut microflora and the host for 

available nutrients (Dibner and Richards, 2005).  
However, there is an active search for alternatives to AGPs 

in animal feeding. This includes the use of probiotics, organic 

acids, prebiotics, minerals, enzymes, herbs, phenolic 
aromatic components and fermented feeds (FF) 
(Knarreborg et al., 2002; Reid and Friendship, 2002; 
Verstegen and Williams, 2002; Dahiya et al., 2006; 
Steiner, 2006; Missotten et al., 2007). FF is considered  
 
 
*Corresponding author. Email: at_niba@hotmail.com or 
atniba@yahoo.fr. 

 
 
 
 
 
as a biosafe method for replacing AGP in pigs (Knarreborg 
et al., 2002; Kobashi et al., 2008) and poultry (e.g. Heres et 
al., 2003a; Heres et al., 2003b; Heres et al., 2003d; Niba, 
2008). FFs are characterised by high numbers of lactic acid 
bacteria (LAB) (approximately 10

9
 cfu/ml of feed) and high 

concentrations of lactic acid (>150 mM) (Heres et al., 2003a; 
Niba, 2008). In chickens, the organic acid content of 
fermented feeds has been reported to improve foregut 
barrier function against pathogens by increasing acidity and 
lowering the pH (Heres et al., 2003d; Engberg et al., 2006). 
The proportion of chlortetracycline-resistant Escherichia coli 
strains was significantly reduced in the gut of weaned piglets 
fed fermented liquid feed (FLF) (22.2%) compared with dry 

feed (88.9%) (Kobashi et al., 2008). This review, 
examines the potential of bacterial fermentation of feeds 
as a means of improving feeds for pigs and poultry. 
Emphasis will be placed on the interplay of factors 
affecting feed fermentation and their relationship to feed 
quality. 
 
FERMENTED LIQUID FEED TECHNOLOGY 

 
Man has known the use of microbes for preparation of 
food products for thousands of years and all over the 

world a wide range of fermented foods and beverages 
contribute significantly to the diet of many people (Achi, 
2005). The use of liquid feeds in animals has created an 



 
 
 

 

opportunity for recycling of liquid co-products from the 
human food industry especially in the European pig 
industry (Scholten et al., 1999; Brooks et al., 2003a). This 
has considerably reduced the need for alternative 
methods of disposal of these products, like drying, 
disposal to land fill or burning (Scholten et al., 1999). 

However, liquid feeds have the potential to serve as 
potent reservoirs of enteropathogens unless steps are 
taken to prevent their introduction and proliferation during 
storage and feeding (Beal et al., 2002). Brooks et al. 
(2001) also stated that liquid- feeding systems can easily 
become contaminated. They further observed that the 
development of computerised liquid-feeding systems 
capable of feeding pigs ad libitum has rekindled interest 
in the possibility of liquid feeding for weaner pigs. This, in 
addition to recent developments in the use of lactic acid 
bacteria in the accelerated fermentation of feed 
substrates for animal feeding as well as reducing the 
possibility of contamination by enteropathogens (Beal et 
al., 2002; Beal et al., 2005), has provided a good basis 
for improvement in pig nutrition. It is also having much 
promise in other farm animal species especially poultry 
(Heres et al. , 2003b; Skrede et al., 2003; Niba, 2008) 
and aquaculture (Refstie et al., 2005) . Fermented liquid 
feed technology could make important contributions to 
African agriculture especially in semi-arid and hot areas 
(Niba et al., 2008b). In such areas, ambient temperatures 
(appro-ximately 30°C) could support efficient lactic acid 
fermentation of feeds (Beal et al., 2002; Niba, 2008). 
Furthermore, wet feeding in hot climates has been shown 
to improve feed intake and growth rates in poultry 
(Forbes, 2003).  

According to Beal et al. (2002), lactic acid bacterial 
fermentation of feeds provides a feed that has a pH of 3.8  
- 4.0 and contains 150 - 250 mmol/L lactic acid. A similar 
range of fermented feed pH has been reported by Geary 
et al. (1996) (3.8 - 4.2), Christensen et al. (2007) (3.6 - 
4.2), Scholten et al. (1999) (3.5 - 4.5) and Moran et al. 
(2006) (<3.8). The synergistic effect of a high lactic acid 
concentration and low pH is believed to act in concert to 
give fermented feeds their antimicrobial activity. This 
enables them to withstand contamination by pathogens 
like Salmonella spp. (Geary et al., 1996; van Winsen et 
al., 2001a; Beal et al., 2002; van Winsen et al., 2002), 
Campylobacter spp. (Heres et al., 2004), and coliforms 
(Russell et al., 1996). 

The mechanism of action of fermented feeds and 
fermented co-products in controlling enteropathogens 
both in vitro and in vivo has been reviewed extensively 
(Brooks et al., 1996; Scholten et al., 1999; Hansen et al., 

2000; van Winsen et al., 2001a; Beal et al., 2002; 
Demeckova et al., 2002; Hojberg et al., 2003; Boesen et 
al., 2004; van Immerseel et al., 2004; Beal et al., 2005; 
Moran et al., 2006). The antimicrobial effects of lactic acid 
are believed to be exerted by the ability of the undissociated 

acid to gain entry into the cell, disrupt pH homeostasis and 

consequently cause nucleic acid and protein damage (Beal 
et al., 2002). According to Moran (2001), the low 

  
  

 
 

 

pH, dissociation constant (pKa value),and the molar 
concentration are factors that determine the inhibitory 
activity of lactic and acetic acid in fermented feed. While 
inside the cell, the acid dissociates and causes a drop in 
pH. This stops enzymatic processes and causes the 
proton motive force to collapse. The anion may also 
destroy the cell wall resulting in cell death (van Winsen et 
al., 2001a; van Winsen et al., 2001b). However, Alakomi 
et al. (2000) earlier stated that disruption of the outer 
membrane by acids could involve both dissociated and 
undissociated forms. As indicated, the likely action on the 
outer membrane of Salmonella could be protonation of 
anionic components such as carboxyl and phosphate 
groups. This consequently weakens the molecular 
interactions between outer membrane components thus 
increasing its permeability.  

In a recent review by Brooks (2008) on fermented 
liquid feeds for pigs, increasing feed cost, withdrawal or 
reduction of antimicrobial growth promoters (AGP) in 
feeds and quality assurance programmes related to 
Salmonella in pig meat were given as reasons why 
producers should adopt liquid feeding. However, he 
indicated that the success of liquid feeding depended on; 
 

i.) Microbial fermentations and selection of LAB capable 
of generating lactic acid levels above 100 mmol/L that 
can significantly reduce numbers of enteropathogens and 
the incidence of Salmonella.  
ii.) Batch fermentation of the cereal portion of feeds with 
inoculants capable of generating high lactic acid concen-
trations to give more consistent results of fermentation. 
iii.) Fermentations that could preserve the feed, improve 
the availability of nutrients, reduce the level of anti-
nutrients and have LAB with probiotic properties. 
 

Meanwhile, the three principal components involved in 

the fermentation process are the fermenting micro-

organisms, the feed substrate and the enabling 
environment for fermentation (Figure 1). 

 

INFLUENCE OF MICRO-ORGANISM AND FEED 

SUBSTRATE ON FERMENTATION 
 
The selection of LAB for feed fermentation to meet 
desired feed and production objectives has been 
highlighted in previous reviews (Brooks et al., 2003b; 
Brooks, 2008) . The choice of feed substrates to obtain 

high numbers of LAB (10
9
 cfu/g feed) and levels organic 

acids (>150 mmol/L) or a consistent fermentation product 
has also been researched (Canibe et al., 2007a; Niba et 
al., 2007; Lyberg et al., 2008; Niba, 2008; Niba et al., 
2008b; Olstorpe et al., 2008) or reviewed (Brooks, 2008). 
Fermentation objectives that have influenced the use of 
LAB have centred on; 
 

i.) Selection for rapid production of organic acids (mainly 

lactic acid) to ensure biosafety (e.g. Missotten et al., 



     
 
 
 
 

 

Micro-organism  
-LAB  
-Yeasts and fungi 

 
 
 
 

 
Environment  

 

-Time (hours) 
Substrate  

-Temperature  

-Carbohydrates  

-Moisture content  

-Proteins  

-Air Composition  

-Fibres  

 
 

 -Feathers 
 

 
 

 
Figure 1. Interactions in the fermentation medium. Fermentation conditions influence rate 

of fermentation, type of microbe and substrate quantity and quality affects the medium. 
 

 

2007; Missotten et al., 2008).  
ii.) Selection for homolactic fermentation to improve feed 
palatability. 
iii.) Breakdown of anti-nutrients and increased bioavai-
lability of nutrients (e.g. Bertsch et al., 2003; Brooks et al., 

2003a; Oboh, 2006; Skrede et al., 2007; Lyberg et al., 

2008; Okpako et al., 2008). 
 

A summary of how some of these objectives relate is 

shown in Table 1. 
 

The advantages of fermenting feeds can be summarised 

from the table as follows; 
 
i.) Reduction in the level of anti-nutrients within the feed. 
ii.) Improved bioavailability of minerals (e.g. P, Ca, Mg 
and Cu).  
iii.) Increase in protein contents (lysine, histidine and 
methionine). 
iv.) Breakdown of indigestible carbohydrates. 
 

 

INFLUENCE OF FERMENTATION LENGTH AND 

CONDITIONS 
 
The length of steeping feed ingredients, the type of feed 
substrates and fermentation conditions influence the 
quality of the fermentation product. Steeping time has 
been related to its effects on the activity of endogenous 
enzymes and the breakdown of anti-nutrients within the 
grain. According to Choct et al. (2004a) the effects on 
growth and feed intake for weaner pigs resulting from 
steeping of feed for 15 h might be related to the release 
and activation of endogenous enzymes in the grain. The 
activation of these enzyme systems within the grain can 

 
 

 

act on cell wall structures in a similar way to exogenous 
feed enzymes (Choct et al., 2004b). In reviewing the 
effect of steeping in liquid feeding systems, Brooks et al. 
(1996) indicated that phytases that were naturally present 
in the pericarp of some grains (like cereals) could be 
activated by soaking. They also stated that soaking feed 
for 8 - 16 h before feeding increased the bioavailability of 
phosphorus, calcium, magnesium and copper. In another 
study (Lyberg et al., 2008), the phytase activity for a 
cereal grain mix of wheat, barley and triticale was 1382 
FTU /kg DM and inositol hexaphosphate bound-
phosphorus and total phosphorus were 2.2 and 3.7 g/kg 
DM. After fermentation, dietary inositol hexaphosphate 
was completely degraded to release phosphorus.  

Fermentation of the carbohydrate-rich cereal compo-
nents of the diet separately and combining them with the 
protein-rich components just before feeding has some 
practical and nutritional advantages (Beal et al., 2002; 
Brooks et al., 2003b; Beal et al., 2005; Moran et al., 2006; 
Canibe et al., 2007a; Brooks, 2008). Fermenting the 
protein rich components produces undesirable end-
products, such as biogenic amines, which could affect the 
palatability of fermented liquid feed (Canibe et al., 
2007a). Furthermore, some studies have reported the 
degradation of free amino acids added to diets during 
fermentation (Handoyo and Morita, 2006; Canibe et al., 
2007b). However, Niven et al. (2006) demonstrated that 
the loss of lysine from fermented liquid pig feed was due 
to metabolism of lysine by E. coli present in the feed 
rather than its utilisation as an energy source by LAB. It 
was observed that inoculation of feed with LAB and 50 
mmol/L lactic acid at the beginning of fermentation 
resulted in lysine levels remaining unaltered after 72 h 
fermentation. The addition of acid reduced or eliminated 
the E. coli and allowed the lysine to remain intact during 



  
 
 

 
Table 1. Effect of micro-organisms and feed substrates on feed fermentation. 

 

Fermentation type Substrate  pH Lactic acid  Acetic acid Ethanol or Source  
         or effects  or effects effects on    

         on diet  on diet diet    

L. plantarum, P. Wheat  and  wheat  by- <3.8 <60
†
  <10

†
 <10

†
 (Moran   et   al., 

pentosaceus, Yeasts products        2006)   

        4.53 22.21*  22.42* 9.12* (Beal   et   al., 
             2005)   
             

Spontaneous   Barley    4.30 34.43*  27.34* 10.74* (Beal   et   al., 
fermentation.            2005)   

(LAB and Yeasts)              

Lactobacillus brevis Soybean white flakes 4.8 Elimination of  indigestible carbohydrates (Refstie  et  al., 
         and lowered trypsin inhibitor activity 2005)   

Lactobacillus sp. (strain Barley and wheat and - Significant reduction in phytic acid, dietary (Skrede  et  al., 
AD2), L. plantarum barley whole meal flours  fibre  and   -glucans  (33.5-18.4  g/kg  in 2001; Skrede et 
(AM4).         barley), alpha-amylase activity in barley al., 2002; Skrede 

             et   al.,   2003; 
             Skrede  et  al., 
             2007)   

Lactobacillus acidophilus Sesame seed meal  - Phytic  acid  reduced  to  below  detectable (Mukhodhyay  
         limits and tannin contents reduced from 20 and Ray, 1999) 
         to 10 g/Kg       

Lactobacillus plantarum Complete diets of 3.6 Reduction in feed dry matter and insoluble (Christensen et 
    cereals and  soybean  non-starch   polysaccharides,   increased al., 2007)  

    meal     viscosity of feed     

Unspecified in vitro Pig grower diet  4.9-5.3 Reduced contents of total and free lysine (Canibe  et  al., 
fermentation        (g/kg   crude   protein,   threonine   and 2007c)   

(LAB and yeasts)       methionine       

LAB fermentation  Phytic acid in cereals - Increase  in  apparent  bioavailability  of (Brooks  et  al., 
         Phosphorus,  Calcium,  Magnesium  and 2001; Brooks, 
         Copper    2008)   

    Fermented fish  silage  Increase  in  egg  production  and  quality (Zynudheen et 
    supplementation in quail  (Haugh unit)    al., 2008)  

    diet            

Kocuria rosea   Poultry feathers  - Improved content and availability of amino (Bertsch  et  al., 
    (fermented feather  acids,   lysine   3.46%,   histidine   0.94%, 2003; Bertsch 
    meal)     methionine 0.69%.  and Coello, 
             2005)   

Aspergillus nigeir and L. Cassava peel meal  - Increase in proteins (24.4%), ash (7.52%), (Okpako  et  al., 
rhamnosus        crude  fibre  (10.62%)  and  decrease  in 2008)   

         cyanide (7.35 mg/kg)     

Saccharomyces  Cassava peel meal  - Increase  in  protein  content  (21.5%)  and (Oboh, 2006)  
cerevisae  and      decrease  in  cyanide  (6.2  mg/kg),  and    

Lactobacillus spp.       phytate (789.7 mg/100 g).     
 

†
 g/kg dry matter, *mmol/L, WDG-wet wheat distiller’s grain.

 

 

 

the fermentation process. 
The main goal of fermentation is a high lactic acid 

concentration (>150 mmol/L) and a low pH (<4.5). Tem-
perature affects fermentation rate and low temperatures 
may yield insufficient quantities of fermentation end-
products. According to Carlson and Poulsen (2003) an 
increase in fermentation temperature from 10 to 20°C 
improved the proportion of total barley phytate that was 

 
 

 

degraded during an 8 h fermentation from 48 to 55%. 
Corresponding values for total wheat phytate degraded 
were 52 and 62%. At 38°C it required 2 h for 72% of the 
total phytate to be degraded. Fermentation of a cereal 

grain mix at 10°C produced 8.6 gl
-1

 of lactic acid 

compared with 13.6 gl
-1

 at 20°C (Lyberg et al., 2008). At 
low temperatures yeast predominates and produces 
ethanol (Brooks, 2008). Insufficient lactic acid concentra- 



 
 
 

 

tion with 24 h fermentation cycles which are more 
practical on farms may be the case at low temperatures. 
Furthermore, spontaneous fermentation of a cereal grain 
mix at 10°C required 7 days for the pH to drop to 4.0 
compared with 5 days for 15 and 20°C. Prolonged 
fermentation also results in considerable variation in 
species composition of fermented pig feed (Olstorpe et 
al., 2008). Fermentation at 30°C seems ideal as at 35 

and 40°C there was no significant effect on lactic 
utilisation of feed nutrients like added synthetic lysine by 
and acetic acid concentrations (Table 2) while butyric 
acid and ethanol concentrations were significantly 
increased (Beal et al., 2005). Lactic acid fermentation of 
sorghum and maize at 30°C produces high levels of lactic 
acid (>150 mmol/L) as fermented cereal-base for moist 
chicken feed (Niba, 2008; Niba et al., 2008a; Niba et al., 
2008b). 

 

LIQUID TO FEED RATIOS 

 

An important aspect of a successful liquid feeding regime 
is the liquid to feed ratio of the diet. This affects the dry 
matter content of diet and may also have implications for 
the intake and organic acid concentration of the feed. 
Research to confirm the ideal dry matter content of liquid 
diets is limited (Choct et al., 2004a). In pigs, a wide range 
of liquid to feed ratios (3:1, 4:1) (Choct et al., 2004a), 
(2:1) (Demeckova et al., 2002; Choct et al., 2004a; Xuan 
Dung et al., 2005), (2.5:1)(Russell et al., 1996; Boesen et 
al., 2004), (3.5:1) (Geary et al., 1996) have been used. In 
chickens, these ratios have been reduced to 1.3:1 (Yasar 
and Forbes, 1999) and 1.4:1 (Heres et al., 2003a; Heres 
et al., 2003b; Heres et al., 2003c; Heres et al., 2003d; 
Heres et al., 2004). With lower liquid to feed ratios, 
fermented chicken feeds could be considered as 
fermented moist feeds rather than liquid feeds (Niba, 
2008). However, the DM concentration of feed has been 
shown to have little overall effect on the pattern of 
microbial activity (Geary et al., 1996). Meanwhile, 
increasing water to feed ratios improved both DM and 
energy digestibility of diets for pigs. However, since in 
commercial practice with pigs liquid to feed ratios can 
vary from 2:1 to 7:1 (Choct et al., 2004a), performance is 
likely to be affected by DM intake (Table 3). 
 

 

CONTROLLED FERMENTATION USING STARTER 

CULTURES 
 
Successful fermentation results have also been found to 
be dependent on the type of fermentation adopted. A 
brief definition of the methods of fermentation is given in 
Table 4. Spontaneous (Beal et al., 2005), backslopping 
(Moran et al., 2006), inoculated or controlled fermenta-
tions (e. g. Christensen et al., 2007; Canibe et al., 2008) 

have been investigated as methods that could be used 
for production of fermented liquid feeds. Spontaneous 

 
 
 
 

 

fermentation has been discouraged (Brooks et al., 2003b; 
Brooks, 2008) because in this system yeast, which can 
tolerate low pH and a low temperature, can predominate. 
Yeast fermentation of starch will result in alcohol and 

carbon dioxide production. The production of CO2 

represents a loss of feed dry matter and energy value. 
Such feeds could be unpalatable due to ‘off’ flavours 
resulting in reduced feed intake. Secondly, spontaneous 
fermentation may not guarantee a rapid build-up of lactic 
acid in the feed, which is necessary for biosafety of the 
feed and to limit the pathogens (Niven et al., 2006). 
Lastly, since feed ingredients differ in their load of natural 
microflora, spontaneous fermentation of the same raw 
material at different times results in inconsistent end-
products.  

Backslopping has been practiced on many farms (Beal 
et al., 2002). The limitations of this method have recently 
been highlighted in the review by Brooks (2008). In 
addition to these limitations, additions of fresh feed to a 
dynamic fermenting medium could have adverse impli-
cations on microbial balance and the ability of the feed to 
resist enteropathogens. Temperature shifts during 
addition that are outside the optimal range of particular 
pathogens could provoke the secretion of cold-shock 
proteins (Beal et al., 2002). Such cold shock proteins 
could increase pathogen tolerance to lactic acid in feed 
fermented at 20°C compared with 30°C. 

Controlled fermentation or inoculated fermented liquid 
feed would appear preferable for production of fermented 
liquid feeds for pigs or fermented moist feeds for chick-
ens because more predictable results could be obtained. 
Selection for LAB that produce lactic acid rapidly, with 
high 24 h lactic acid (>150 mmol/L) contents (Brooks, 
2008), should be the primary objective. The selection of 
LAB for other factors, such as probiotic properties is 
beyond the scope of this review. 
 
 
EFFECTS OF FERMENTED FEED ON PERFORMANCE 

OF PIGS 
 
In growing pigs, the daily weight gains (kg/day) of FLF fed 
groups (0.572) and acidified feed (AF) fed groups (0.567) 
were significantly higher (P < 0.05) than pigs on a dry diet 
(DF) (0.515) and non-fermented liquid feed (NFLF) 
(0.498) (Xuan Dung et al., 2005). Plasma urea nitrogen 
was also significantly lower (P < 0.05) in FLF fed pigs 
than the dry diet, non- FLF and AF. As observed by 
Demeckova (2003), piglets from gilts fed FLF were 300 
and 450 g heavier than piglets from the gilts fed NFLF (P 
< 0.01) and DF fed gilts (P < 0.001).  

Demeckova et al. (2002) reported that faeces from 
sows fed FLF feed had significantly (P < 0.001) lower 
numbers of coliforms than sows fed NFLF or DF. They 
also reported that piglets from sows fed FLF excreted 

faeces that were higher in LAB (7.7 vs 7.3 log10 cfu/g, P < 

0.01) and lower coliforms (7.5 vs 8.1 log10 cfu/g, P <  
0.001) than faeces from piglets of DF-fed dams. Further- 



  
 
 

 
Table 2. Effect of incubation time and fermentation temperature on feed fermentation. 
 

Incubation Temperature pH Lactic acid or Acetic acid or Ethanol or effects Source 
 

time (h) (°C)  effects on diet effects on diet on diet   
 

24 - 3.75 54.5
†
   Yeast population Yeast population (Moran et al., 

 

      increases 10- fold increases 10- fold 2006) 
 

          

48 - 3.65 Yeasts  population Yeasts population Yeasts population  
 

   stabilizes  and stabilizes  and stabilizes  and  
 

   coliforms   coliforms eliminated coliforms eliminated  
 

   eliminated mainly mainly  by mainly  by  
 

   by backslopping backslopping  backslopping   
 

           
 

24 - 4.69 11.68*   17.22*  6.81*  (Beal  et  al., 
 

48 - 4.34 31.92*   27.55*  10.62*  2005) 
 

72 - 4.21 46.14*   30.75*  12.79*   
 

- 30 4.47 30.16*   16.42*  11.69*   
 

- 35 4.41 25.29*   26.57*  9.78*   
 

- 40 4.36 28.64*   32.89*  8.42*   
 

48 20 4.2 115*     Dvalue (min)-250   (Beal  et  al., 
 

72 20 3.9 164*     Dvalue (min)-164   2002) 
 

96 20 3.8 167*     Dvalue (min)-137    
 

48 30 3.8 161*     Dvalue (min)-45    
 

72 30 3.8 196*     Dvalue (min)-38    
 

96 30 3.8 203*     Dvalue (min)-34    
 

0
a
 10 - ND

b
   5.5

c
     (Olstorpe   et 

 

0
a
 15 - ND

b
   5.5

c
     al., 2008) 

 

0
a
 20 - ND

b
   5.5

c
      

 

3
a
 10 - ND

b
   ND

c
      

 

3
a
 15 - ND

b
   5.3

c
      

 

3
a
 20 - 2.1

b
   5.6

c
      

 

5
a
 10 - ND

b
   3.8

c
      

 

5
a
 15 - 2.1

b
   4.6

c
      

 

5
a
 20 - 3.1

b
   4.9

c
      

 

7
a
 10 - 2.0

b
   4.5

c
      

 

7
a
 15 - 2.1

b
   6.2

c
      

 

7
a
 20 - 2.1

b
   5.7

c
      

 

0 20 - <3.0±0.00
c
 5.0±1.27

d
 3.9±0.00

b
 (Canibe et al., 

 

6 20 - <3.0±0.00 c 6.0±0.12 d <3.2±0.21 b 2007c) 
 

    
 

24 20 - 8.1±0.75
c
 7.1±0.56

d
 3.6±0.16

b
  

 

48 20 - 9.5±0.34
c
 6.7±0.87

d
 3.7±0.95

b
  

 

0 20 - ND   4.7±0.03 ND   
 

6 20 - ND   4.9±0.16 1.9±0.11   
 

24 20 - ND   5.9±0.42 6.8±0.14   
 

48 20 - 91.2±27.66 20.9±6.21 15.5±1.31  
 

17-19
a
 10  1.8   10.4  1.2  (Lyberg et al., 

 

17-19
a
 15  1.9   10.4  1.2  2008) 

 

17-19
a
 20  2.2   10.5  1.1   

 

17-19
a
 10  3.3

b
   7.2

c
  2.4

d
   

 

17-19
a
 15  3.2

b
   5.9

c
  2.3

d
   

 

17-19
a
 20  4.8

b
   7.4

c
  2.0

d
   

  
†
g/kg dry matter, *mmol/L, Dvalue (min)-decimal reduction time (minutes) of Salmonella in fermented feed, 

a
days, 

b
yeasts counts (cfu/g feed), 

c
LAB counts 

(cfu/g feed), 
d
Enterobacteriaceae counts (cfu/g feed), 

d
moulds, ND-not detected. 



 
 
 

 
Table 3. Effect of liquid to feed ratios of diets on performance. 

 

Liquid to feed ratio Type of operation Remarks Source 

2:1, 3:1,4:1 Experimental trial No   significant   effect   on   growth   and (Choct et al., 2004b) 
  performance  parameters  but  FCR*  of  liquid  

  diets higher (P<0.05) than dry weaner pig diets.  

1.63: 1 to 3.25:1 Experimental trial Digestibility coefficient increase from 0.791 to (Barber et al., 1991) 
  0.829 with increase in liquid to feed ratio in  

  pigs.  

1.5:1 to 2.25:1 Experimental trial Feed intake, weight gain and carcass weights (Yalda and Forbes, 1995) 
  of chickens not significantly affected.  

2.1:1 to 5:1 Commercial farms Good results with pigs. (Choct et al., 2004b) 

1.5:1 to 3:1 Experimental trial No significant effect on pig performance (Hurst, 2002) 
†
DM 149 to DM 255 Experimental trial Little effect on microbial activity, DM intake, (Geary et al., 1996) 

  weight gain or DM FCR of pigs  
 

*FCR- feed conversion ratios; 
†
Diet dry matter concentrations (g/kg diet). 

 

 
Table 4. Definitions of types of fermentation. 

 

Type of Definition Source 
fermentation   

Spontaneous Fermentation through the action of indigenous microflora present in the (Brooks, 2008) 
 feed  

Backslopping A proportion of a previous fermentation is retained as an inoculum for (Moran et al., 2006). 
 fresh feed  

 Consecutive microbial re-inoculation with micro-organisms from the (Häggman and Salovaara, 2008) 
 previous batch  

Inoculated Fermentation resulting from inoculation of feed with selected lactic acid (Brooks, 2008) 
 bacteria  

Controlled Fermentation resulting from inoculation of feed with selected lactic acid (e.g. Beal et al., 2002) 
 bacteria under controlled environmental conditions (e.g. temperature)  

 

 
Table 5. Economic analysis of fermented liquid feed for pigs (Nguyen Nhut Xuan Dung et al. 2005). 

 

Parameter DF NFLF AF FLF 

Feed cost, VND/kg 3528 3528 5202 3528 

Total feed intake, kg 220 213 216 195 

Live weight gain, kg 50.9 49.6 55.4 55.0 

Feed cost/gain, VND* 15.222 15.182 20.239 12.477 
 

*Vietnamese dong (currency), DF- dry feed, NFLF-non-fermented liquid feed, AF-acidified feed, FLF-

fermented liquid feed. 
 

 

more, Xuan Dung et al. (2005) (Table 5) has indicated 

that feeding FLF to growing pigs is associated with the 

lowest feed cost/gain ratios compared with DF, NFLF and 

AF for growing-finishing pigs in Vietnam. 
 

 

EFFECTS OF FERMENTED FEED ON PERFORMANCE 

POULTRY 
 

Research on the use of fermented moist feeds on the 

performance of chickens is limited. However, some stu- 

 
 

 

dies have shown that wet feeding increases the feed 
intake and growth rate of chickens (Yalda and Forbes, 
1995; Yasar and Forbes, 1999; Mai, 2007). Pre-soaking 
of broiler feeds for 12 and 24 h significantly increased dry 
matter digestibility and body weight gain in male broilers 
(25 - 40 days of age) compared with dry feed (Yalda and 
Forbes, 1996). Bacterial fermentation of barley and wheat 
whole meal flours with -glucan-degrading LAB has 
improved growth and early feed:gain ratio in broiler 
chickens (Skrede et al., 2003). A 10% inclusion of 
fermented fish waste silage in poultry feed increased egg 



 
 
 

 

quality and production in Japanese quails (Zynudheen et 
al., 2008).  

Early access to semi-moist diets for day- old chicks 
stimulates gastrointestinal (GI) development and pre-
vents dehydration during transport from the hatchery (van 
den Brink and van Rhee, 2007) . Rapid GI tract 
development after hatch is essential for optimisation of 
digestive function and underpins efficient growth and 
development as well as a full expression of the genetic 
potential for production traits (Mitchell and Moreto, 2006; 
Mai, 2007). Furthermore, the moistening capacity of the 
crop of chicks during the first weeks of life is also 
believed to be a limiting factor for the optimal functioning 
of the gut when standard solid diets are fed (Mai, 2007). 
Yasar and Forbes (1999) attributed the beneficial effects 
of wet feeding to decreased viscosity of gut contents, 
greater development of the layer of villi in the digestive 
segments and reduced crypt cell proliferation in the crypts 
of the epithelium. However, more research is required to 
provide a better understanding of the contribution of 
fermented moist feeds in poultry nutrition. 

 

CONCLUSION 
 
A successful application of fermented liquid feeds in pig 
or moist feeds in chicken feeding systems depends on 
the ability to select the right balance of LAB, feed 
substrates and fermentation conditions capable of pro-
ducing repeatable fermentation results. Meanwhile, the 
resistance of such feeds to enteropathogen contamina-
tion during short storage, and their capability to reduce 
pathogen colonisation in the gut of pigs and poultry, could 
have far-reaching implications for improved food and 
environmental safety in warm wet regions of the African 
continent. 

 
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