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Probiotics

Probiotics

Support birds’ health, performance and growth

Probiotics, or beneficial bacteria, for chickens and other avian species are commonly added to poultry feed or drinking water in order to help support birds’ health, performance and growth. 

This is particularly important in young animals in which stable intestinal bacteria have not yet been established. By adding probiotics to feed or water the intestine is populated with beneficial bacteria avoiding or decreasing the extent of pathogen colonization (Nurmi and Rantala, 1973).  

Types of commercial probiotics for chickens include: 

  • Single strain 
  • Multi-strain 
  • Multi-strain / multi-species 
  • Synbiotics (prebiotics + probiotics) 

Poultry probiotics or direct fed microbials (DFM) are live microorganisms that can be incorporated in diets in order to:

Populate the intestine with beneficial bacteria

Modulate the conditions within the gastrointestinal tract

What is a Poultry Probiotic?

Definitions

Poultry probiotics are defined as live microorganisms causing no pathological disorders and promoting enteric microbiota balance (Ohimain and Ofongo, 2012), optimizing function of enteric epithelia and mucosal immunity, which is an important first line of defense against the intrusion of enteric pathogens (Fagarasan, 2006). Watch this video to learn more about the definition of poultry probiotics. 

Prebiotics can be included together with probiotics or alone in order to promote beneficial bacteria survivability (lawska et al., 2017). 

Synbiotics compounds are composed of combined probiotics and prebiotics that work synergistically, these compounds together benefit from each other and enhance their biological activity (lawska et al., 2017). 

Synbiotics can be a useful scientific development to diminish the impact of common gastric issues that impair birds’ performance (Kabir SML, 2004) and to reduce the incidence of antibiotics as growth promoters or even the frequency of antibiotic treatments.
 

Application of probiotics for chickens

Feed

Drinking water

Post-pelleting or extrusion

Probiotics and synbiotics can be delivered to flocks via feed or drinking water (soluble) application. Post-pelleting application is also possible.

Categories of commercial probiotics

Currently, there is a range of probiotic products available globally. These products fall into several categories:

  • Single strain
  • Multi-strain
  • Multi-strain / multi-species
  • Synbiotic products.

There are also a few multi-genus products available, but due to the complexity of cultivation and stabilization, these products are rare. Table 1 provides an overview of the major probiotic bacteria species used. The modes of action of the various probiotic species differ between performance enhancement and gut health improvements, including competitive exclusion of pathogens.

Main species of probiotic bacteria

BacillusB. subtilis, B. licheniformis
LactobacillusL. acidophilus, L. bulgaricus, L. reuteri, L. salvarus, L. sobrius
EnterococcusE. faecium
BifidobacteriumB. animalis, B. bifidum
PediococcusP. acidilactici 
ClostridiumC. butyricum
StreptococcusS. thermophilus

 

Two major categories of probiotics

Most commercial probiotic products fall into two major categories.

  1. Sporulated Bacillus spp.
  2. Lactic acid producing bacteria

Sporulated Bacillus spp., both single and multi-species, remain in the lumen or outer mucus layer  are are shown in dark green. Lactic acid producing bacteria shown in light green, depending on their origins and mucus attaching capabilities, are either able to colonize the firmly attached mucus and the underlying epithelial wall itself like most Bifidobacterium animalis strains, or they are transient organisms like most Lactobacillus acidophilus strains, which are not colonizing said areas, similar to Bacillus spp.

Adapted from Atuma et al., 2001.

Understanding Bacillus spp.

Starting with the small intestine, many of the Bacillus species remain in the lumen or the upper layer of the loosely adhering mucus layer of the gut, and excrete proteases or non-starch polysaccharide enzymes, thereby increasing nutrient digestibility.

This reduces the availability of easily fermentable nutrients to pathogenic bacteria, especially in the hindgut. Bacillus species also have the ability to secrete some bacteriocins (metabolites that selectively inhibit bacterial growth), which has a positive effect in modulating pathogenic bacteria like Clostridium perfringens coming from the feed.

Bacillus spp. are not colonizing bacteria but transient microorganisms. This means they are unable to attach to the epithelial layer of the gastrointestinal tract, thereby inherently limiting any direct immune modulation in the bird.

In addition, many Bacilli are isolated from soil, not poultry, limiting the host immune interaction further. However, the increase in protein digestibility combined with the bacteriocin production reduces the risk of gut inflammation from C. perfringens, thereby improving the bird’s health and performance, and reducing the need for therapeutic antibiotic treatments in an indirect fashion.

Although Bacillus spores provide the natural protection of a probiotic, the spores are not metabolically active. Consequently, they need to be activated throughout the digestive process in the chicken, which is done with temperature over time and through the presence of free amino acids in the small intestine.

There are ongoing debates as to the time it takes for spores to germinate in order for their protective and digestive capabilities to take effect in a bird’s gastrointestinal tract.

  • Scientific studies indicate that spore germination is triggered by moisture (here saliva), temperature over time and free amino acids, as well as a sensitivity to acid of the viable Bacillus. This indicates that most activity can be expected past the gizzard, when the pH of the digesta is close to neutral, starting in the duodenum.

Lactic acid producing bacteria (LAB)

The lactic acid producing bacteria (LAB), for example Lactobacillus spp.Pediococcus spp. and Enterococcus spp., can be derived from various sources, which may not be particularly poultry. This may have an impact on the ability of the individual bacteria species to adhere to the firmly attached mucus layer (light green in Figure 1) and intestinal cell lining, and therefore reducing the ability of the bacteria to competitively exclude pathogenic bacteria from attachment sites.

This attachment is important for the early development of the immune system as it is a time when the system is being imprinted in regard to its function. With 70% of the chicken’s immune system in the intestine, rapid development of this system is important to the future gut health of the bird.

As the name indicates, lactic acid producing bacteria have the ability to produce organic acids, primarily acetic and lactic acid, but in a few cases butyric acid as well. They are generally produced along with a large variety of bacteriocins. Acetic acid is also used by some of the other commensal bacteria in the cecum as a food source, for example it is utilized to produce butyric acids as a metabolite. This may help explain why there is an increase in natural butyrate production with probiotics, even when no butyric acid producing bacteria are included in the probiotic mix itself.

In addition, many of the pathogenic bacteria, such as avian pathogenic E. coli or Salmonella spp., are pH sensitive, so even localized production of organic acids in the firmly attached mucus layer, along with the bacteriocin secretion of probiotic bacteria will have a modulating effect of pathogens in the gastrointestinal tract. Colonization by a beneficial Bifidobacterium strain can improve a bird’s immune development, limiting the need for immune response, thereby reducing the nutrient loss for this process.

Two key factors for prebiotics

The success of a poultry prebiotic relies on two factors:

  1. Being indigestible to pathogenic bacteria but able to stimulate the growth of beneficial bacteria, such as Bifidobacterium and Lactobacillus
  2. Being able to restrict the growth and colonization of pathogenic bacteria

The process of restricting pathogens while favoring beneficial bacteria is known as competitive exclusion, often abbreviated to CE. Competitive exclusion can only be achieved with live organisms through activity in the digestive tract. 

Contention over true synbiotics

Some companies combine probiotic bacteria with prebiotic mixtures in order to produce a synbiotic product. The prebiotics advance the rapid establishment of the probiotic strains through the provision of an additional nutrient source. However, with low inclusion levels and localization in close proximity to the probiotic, the prebiotic effects will be more limited to the probiotic bacteria rather than the general microbiota, which can also utilize them. There is ongoing discussion that immune-modulating prebiotics, e.g. those used in combination with probiotic bacteriocin producing strains, where the prebiotic (e.g. immune modulatory yeast cell walls) is not in direct support of the probiotic, is, strictly speaking, not a true synbiotic.

Extreme processing and application options

Some feed mills and farmers use exceptional heat treatments such as high temperatures and time conditioning, expansion and even extrusion. Extrusion is being utilized more and more due to increasing awareness and requirements in food safety. Under these circumstances, the viability of any probiotic, sporulated, encapsulated or not protected, is severely challenged, but the microorganism is usually not completely destroyed.

In this case, the use of water-soluble probiotics in the hatchery or on arrival at the rearing farm, can be an effective way to deliver beneficial bacteria to birds’ gastrointestinal tracts.

Heat treatment, extrusion and pelleting are common poultry feed processing methods.

Can poultry probiotics withstand the heat treatment?

One question that we often receive from customers is whether probiotics can withstand the heat treatments being used in normal feed production practices.

Some probiotic companies claim that sporulated bacteria such as Bacillus spp. and Clostridium spp. are less heat sensitive than non-sporulated bacteria such as lactic acid producing bacteria and Bifidiobacterium spp. This in itself is true, but it is not a complete answer.

Protection from oxygen sometimes required

Bifidiobacterium spp. are obligate anaerobes, meaning they cannot grow in the presence of oxygen, and therefore need to be protected from air in order for them to survive. Certain coating technologies offer protection against the normal heat and steam treatments currently used in feed manufacture, which can have additional stabilizing effects for survivability of obligate anaerobic bacteria. However, these protective coatings need to be adapted to the species, and even the specific strain’s needs, in order to warrant proper protection during the pelleting process.

  • PoultryStar® is available in both water application and a microencapsulated form for feed application which allows the product to withstand high temperatures used in pelleted feed.

Use cases

Probiotics delivered to chicks at an early age can help establish a beneficial gut microbiota and set birds on the right path for development. Application of probiotics in adult birds also provides benefits including resistance to health challenges and better flock uniformity. 

Probiotics can be used to address several challenges in commercial poultry production, such as: 

Probiotics in chicken feed

Bacteria challenge

Bacteria, such as Salmonella, Clostridium, Escherichia coli, and other opportunistic microorganisms have the capability of causing chronic mucosal enteric damage disturbing not only gut integrity but also the overall physiology of the birds. 
The outbreak of these microorganisms bring several consequences, such as enteric epithelia cells destruction, decrease on nutrient digestion and absorption capacity (Kaldhusdal et al., 2001). In addition, Salmonella, E. coli and Campylobacter carcass contamination are negative bacteria causing enteric disorders not only in poultry but also in humans.  

Salmonella

Salmonella infection (salmonellosis) does not only affect poultry health and performance leading to an important economic impact, but also a global concern disease for its public health implications (Uzzau et al., 2000). 

One of the biggest public health concerns is to reduce the infection prevalence in humans (Cianflone, 2008). Commercial eggs and poultry meat products consumption are a common source of Salmonella infection in humans, there are evidences determining that contaminated egg consumption is one of the most important source of infection (Dhillion et al., 2001). 

Table eggs can be contaminated during egg-formation through enteric translocation, reaching the egg through the reproductive tract and transovaric pathway (Gantois et al., 2009). Poultry carcasses can also be contaminated either by bacteria translocation through the gastrointestinal tract or by cross contamination at the processing plant. 

Once Salmonella enters into the lumen of the small intestine is able to cause an acute enteritis through a short incubation process and if not controlled a systemic infection (Howard et al., 2012). These bacteria go through the enteric epithelia cells destroying the cell monolayer and negatively affecting physiological processes going on through the enteric surface, e.g., enzymes production, mucus secretion, and nutrients absorption. Many strategies, such as vaccine applications, rodent control, animal protein sources control, and in feed inclusion of organic acids (Heres et al., 2004), probiotics (Tellez et al., 2001), and other feed additives have been applied in order to avoid Salmonella dissemination. 

Salmonella Enteritidis
Salmonella Enteritidis
Source: National Institute of Allergy and Infectious Diseases (NIAID)

Synbiotics and Salmonella control

Salmonella infection destroys the host epithelia cells, promoting inflammatory processes leading to digestive and absorption disorders. Probiotics are a useful tool to diminish Salmonella proliferation in birds (Tellez et al., 2012), the reduction of Salmonella proliferation by the activity of is produced through mechanisms like immune response regulation, competitive exclusion, and production of different kinds of metabolites (Lawley and Walker, 2013). These biological effects vary and are specific to the type of probiotic bacteria strain, number of species, and concentration of beneficial microorganisms offered to the host (Lutful Kabir, 2009). 

Immune response modulation capability of probiotics (Dalloul RA, 2005) have been proven to  reduces enteric damage caused by Salmonella challenges (Lin et al., 2008), this enteric damage reduction is conducted by the regulation of cytokines secretion such as NF-κB ending up on production of anti-inflammatory cytokine IL-10 (Moreno de LeBlanc et al., 2011). Additionally, probiotics competitive exclusion activity prevents Salmonella colonization protecting enteric integrity, thus avoiding epithelia damage (Corrier et al. 1994, Mead, 2000). 

Healthy enteric epithelium develops long villi (Borsoi et al., 2011), researchers have shown how larger villi and shorter crypts are indicative of better nutrients absorption (Shang et al., 2015), enhanced enzymes secretion, active and passive transport of nutrients, and in general better gut integrity. Alternative feed additives have demonstrated a positive influence in the initiation of benefitial enteric microbiota, enteric epithelia morphology (Aliakbarpour et al. 2012), immune function and performance parameters (Panda et al., 2008). 

One of those alternative feed additives are probiotics that have also proven to reinforce Salmonella vaccination programs (Davies and Breslin, 2003; Patterson and Burkholder, 2003). Once the establishment of beneficial bacteria has taken place in the gut, the immune system is primed and anti-inflammatory pathways are activated. As a result, energy and other nutrients invested on increasing blood stream, cells defense migration, epithelia reparation, and other metabolic expensive processes are mediated, leading to improved overall performance (Pender CM, 2016). 

Coccidiosis

Some parasites can cause enteric and physiological disorders, triggering systemic dysfunction or synergies with pathogens and opportunistic bacteria (Chapman HD, 2002). Coccidia is a parasite commonly found in poultry commercial facilities, this parasite destroys epithelia cells, and facilitate the proliferation of opportunistic microbes (Dalloul RA ,2005)., leading to subclinical inflammatory processes and clinical conditions that affect poultry industry profitability (Williams, 2005).

Destruction of epithelial cells breaks down important mucosa structures affecting gut permeability, decreasing digestive enzymes secretion, and absorption of nutrients capacity. A well stablished theory that positions coccidia as predisposing factor for other microorganisms’ proliferation (Stringfellow K, 2011) is the interaction and sinergy between coccidia and Clostridium (Pedersen et al., 2008). 

Eimeria cycle destrys enterocytes (Williams, 2005) causing plasma proteins leakage into the lumen of the gastro intestinal tract (GIT) (Van Immerseel et al., 2004), this free protein is used by Clostridium as a source of nutrients. On the other hand, the inflammatory process triggered by Eimeria damage stimulates mucus secretion, which is also a source of nutrients for Clostridium growth (Collier et al., 2008). 

Once Clostridium proliferates in the lumen of the gastrointestinal tract, these bacteria is able to produce glycolytic enzymes leading to expose the external matrix of enterocytes and structural proteins placed intracellular (Olkowski et al., 2008). Once Clostridium reaches these structures, it adheres to extracellular matrix molecules; this is maybe its most important virulence factor (Wade et al., 2010). Some of these issues are not represented by clinical symptoms. However, they are present and become even more problematic when they occur as subclinical outbreaks in terms of its economic impact (Dahiya et al., 2006). Read more about coccidiosis in poultry.

Synbiotics and control of coccidian outbreak

Immune modulation (Cox CM, 2015), competitive exclusion (Ohimain and Ofongo, 2012), and enhancement of mucosal integrity (Dalloul RA, 2003) reduce the consequences of a coccidia challenge. Up-regulation of the damaged caused by the oocysts in the gastrointestinal tract is shown due to down regulation of pro-inflammatory cytokines expression, down-regulation of pro-inflammatory cytokines is the result of the mode of action derived from probiotics. Consequently, birds would have ameliorated the impact to the epithelial damage caused by coccidia. 

Synbiotics promote microbiota balance between pathogenic and beneficial bacteria (Ohimain EI, 2012) reinforcing gut integrity (Ritzi MM, 2014) by enhancing mucus production, sustaining gut epithelial protection as this is the first physical barrier found by pathogens (Kogut MH, 2012). Once this barrier and its defense mechanisms are set up properly, coccidia is not able to cause same level of damage as if the barrier function of the gut was not properly established. Many field and scientific experiences have shown amelioration of coccidia challenge in presence of probiotic bacteria, validating that the probiotics mode of action can reduce the impact of Eimeria oocysts. Beneficial activity of a balanced microbiota can mitigate intestinal damage redounding on performance improvement (Patterson JA, 2003).  

Heat stress 

Global warming has brought environmental temperature stress problems on poultry flocks around the word (Fouad et al., 2016). Birds expose to heat stress can result on poor performance in broilers, as high morbidity and mortality in layers (Mcgeehin and Mirabelli, 2001) due to impairment to their endocrine system (Rozenboim et al., 2007), electrolytic unbalance (Teeter et al., 1985) and immune system suppression (Mashaly et al., 2004). These disorders can affect microbiota eubiosis and villus morphology (Burkholder et al., 2008).

Prolonged exposure to heat stress increases corticosteroids secretions (Sapolsky et al.,2000) affecting enteric epithelia integrity. Corticosteroids secretion breaks down tight junction proteins promoting bacterial translocation and metabolic disorders. Once these anatomic structures of the enteric epithelia are affected and the physical barrier is more permeable. Therefore, bacteria and toxins can go from the lumen of the gastrointestinal tract to the blood stream. This phenomenon may lead to reduction on feed intake and digestion capability (Zhang et al., 2012) reducing performance efficiency (Azad et al., 2010). 

Synbiotics and heat stress impact control

Heat stress as any other stress stimulate corticosteroid secretion by the suprarenal gland (Shini et al., 200), then corticosteroid secretion is linked to the ratio of hetherophyls and lymphocytes, which is use as stress indicators (Gross and Siegel, 1983). The over secretion of corticosteroid induce the break down of tight junctions proteins leading to, not only, bacteria translocation, but also digestion and absorption disorders. Synbiotics can potentially reduce the impact of extreme environmental temperature, improve feed efficiency and enhance growth rate (Eckert et al., 2010) through the down-regulation of corticosteroid secretion, resulting in an enhanced intestinal barrier and positively influenced immune response (Ng et al., 2009).

Antibiotics reduction and antibiotic-free feeding 

Antibiotic-free feeding (ABF) programs is not only an antibiotics reduction or replacement strategy, but a comprehensive program that includes strengthening of  biosecurity measures and progressive inclusion of feed additives alongside pharmaceutical components, such as such as vaccines, enzymes, acidifiers, phytogenics, probiotics and prebiotics in order to enhance immune system capacity to face challenges on the field. 

The right probiotics are considered a useful tool to be included in antibiotic free production program (Gustafson and Bowen, 1997), this scientific development not only can enhance the immune response against vaccine antigens (Patterson and Burkholder, 2003), but also to decrease the impact of environmental conditions and infectious diseases  (Willis and Reid 2008).

Synbiotics are very useful alone or in combination with other antibiotic-alternatives for the control of infection due to Gram+ and – bacteria (Van Coillie et al. 2007). The use of these alternatives result not only in the control of pathogenic outbreaks but with the right approach serve as natural growth promoters and used as alternative to antibiotics as growth promoters, as well as to decrease the use of antibiotics for treatments (Willis and Reid 2008). A very important clue to determine if either synbiotics could be part of this kind of programs is a correct diagnostic and to determine if the synbiotics mode of action may contribute to diminish the impact of the most common factors modifying animal performance.

How to choose the right poultry probiotic

There are several alternatives of probiotics in the market, all with inherent advantages and disadvantages depending on the nature of the organisms and the treatment that the final product receives.

Several criteria can be used to select probiotics for chickens including: 

* Regarding the first two criteria, buyers should be aware of what they’re buying and to what extent scientific studies document the effects in birds. 

Stability vs. Efficacy

Stability

Poultry producers often have to choose between these two criteria. However, from the poultry producer's point of view it may be safer to select efficacy over stability for a simple reason: it is easy to check for stability and it can be demanded to the probiotic manufacturer. If the manufacturer claims a certain amount of viable colony-forming units (CFU) after pelleting or after 6 months of storage the producer is only a few samples away from the truth. 

Efficacy

On the other hand, there is no insurance for efficacy. There are too many factors that can compromise efficacy of a product in the field: diseases, nutrition, immune status of the flock, and stress factors in general; as a consequence it is difficult for the poultry producer to evaluate the real efficacy of a given product under field conditions.

Buyer Beware
Buyer Beware

If the poultry probiotic manufacturer claims a certain amount of viable colony-forming units (CFU) after pelleting or after 6 months of storage, the producer is only a few samples away from the truth. 

Defined vs. Undefined cultures

Precision

Undefined cultures are a collection of bacterial species. The numerically most predominant bacterial species are normally identified within these products. Undefined cultures tend to be a rapid solution to satisfy many markets. This is due to the lower cost of production when compared to defined cultures.

If the selection process is carefully conducted and bacteria from healthy birds are collected and multiplied under appropriate conditions, several key bacterial strains tend to remain stable and can be recovered after producing many batches of the original cultures. 

Consistency

One of the general concerns when using undefined probiotic cultures is the theoretical lack of consistency of the final product. It is likely that slight variations in the raw materials will change the rate in which different bacterial species multiply. This will probably result in different performance of these probiotics under field conditions.

We should always keep in mind that only a fraction of intestinal bacteria can be cultured using standard laboratory techniques and it is likely that the strains and/or proportions of the strains contained in these products will change over time. 

Pathogen risk

Probably the main factor that makes undefined probiotic culture products unacceptable in several markets is that hidden within the bulk of beneficial bacteria some pathogens could be propagating in low numbers. Favorable conditions, like application of the product in immune suppressed birds, could cause rapid propagation of these potential pathogens.

In addition, if a defined list of bacteria is missing it is impossible to determine the risk of introducing antibiotic resistance genes into bacteria of the host's intestinal tract.

Sporulated vs. Non-Sporulated Probiotics

Sporulated

Sporulation confers an excellent method to protect bacteria against physical damage. From this starting point several advantages can be surmised. For instance, the issues of shelf life and storing conditions seem irrelevant when considering that spores can remain viable for hundreds of years. One main advantage of spores is that they can be easily incorporated into feed tolerating pelleting process with minimal reductions in viability.

Similarly, passage through the stomach should not be a problem for a spore. However, all those advantages seem to pale if the natural habitat of the most currently used sporulated bacteria is considered: Bacillus sp. are well recognized as environmental bacteria. This apparently simple statement draws a question mark on most scientific evidence supporting the effect of the vegetative form of these bacteria against pathogens.

By definition, a dormant life form does not utilize a lot of environmental resources and thus not very many biochemical reactions are taking place.

Competition for available nutrients, production of antibacterial substances, direct inhibition of pathogens, and probably even active attachment and competition for binding sites are all doubtful in case spores are not able to transform into vegetative cells inside the intestinal tract. Valid scientific evidence should address possible mechanisms of action in vivo.

Non-sporulated

In contrast to spores, when considering long storing periods, pelleting, and passage through the stomach, the non-sporulated bacteria seem fragile. Some of these weaknesses can be partially solved by a coating treatment if the bacteria are to be mixed in feed that will be pelleted.

Quality of the coating will determine the cell viability after pelleting and after passage through the stomach. Despite all these weaknesses, when vegetative probiotics (of intestinal origin) reach the intestine they are "at home". If the probiotic strains originate from a compatible animal —or even better from the same animal species— there will be no better place for these bacteria to grow, replicate, compete for nutrients, attach to cellular receptors, and to interact with the host than in the intestine.

From this point of view there is a huge potential for future development of probiotics. It is very likely that in the in vitro process of screening we have lost excellent candidates due to our current inability to create a model that closely resembles the intestinal tract. It is becoming increasingly clear that interaction between bacteria and their environment is very important when analyzing the efficacy of probiotics.

Peptostreptococcus produces an antibacterial substance which is secreted as an inactive compound that requires pancreatic trypsin for activation (Ramare et al., 1993). In addition, it has been observed that the ability of B. lactis bacteria to bind mucus can be potentiated by the presence of L. bulgaricus bacteria (Ouwehand et al., 2000).

Synbiotics used in combination with other products:

A variety of novel feed additives can be used in combination in order to achieve better outcomes or to address specific challenges.

These may include:

  • Poultry acidifiers
  • Toxin binders
  • Enzymes 

Probiotics for chickens plus a poultry acidifier

This synergistic combination allows to enhance antimicrobial and anti-inflammatory activity of these additives (Hume et al. 1993). This effect reduces Gram-negative microorganisms’ proliferation. Control of Gram- microorganism, such as Salmonella and Escherichia coli can be complicated since these bacteria have shown to express resistance against some antibiotics. 

Combining synbiotic and acidifiers cause enhance the antimicrobial efficacy of the additives, and potentiates proliferation of beneficial bacteria activity, carrying on improvement of digestibility and absorption of nutrients through different mechanism of action. Beneficial microbial activity is crucial since probiotics have proved to be very effective to “competitively exclude” microorganisms such as Salmonella (Tellez et al., 2012). 

Synergism of the mode of action of these two feed additives is due to the reduction on pH of the environment by the acidifiers offering proper condition for probiotic bacteria growth. Furthermore, probiotic bacteria can produce a higher concentration of volatile fatty acids  (Ziprin et al., 1991), drop on pH of lumen environment controls proliferation of Gram- enteric pathogens (Barcellos et al., 2004) and also contribute to the competitive exclusion activity of benefitial microbiota. 

However, the benefits of using these natural strategies not only contemplate antimicrobial activity (Santos & Turnes, 2005), but also enhance digestion and absorption of nutrients, this strategy can reduce the impact of enteric pathogens on the birds’ performance (Luoma et al., 2017). 

Probiotics for chickens and phytogenic feed additives

Interaction between coccidia and Clostridium has been well documented (Pedersen et al., 2008), this interaction induce damage of enteric structures causing edematous processes between enterocytes and lamina propria, affecting integrity of important compounds of this anatomic and physiological barrier (Olkowski et al., 2006). 

These consequences can be reduced by the combination of synbiotics and phytogenics. Phytogenic feed additives (PFAs or botanicals) consisting of plant-based bioactive substances are known to enhance digestion and absorption of nutrients, thus, reducing available protein in the lumen of the gastrointestinal tract, this decreases Clostridium proliferation, minimizes gastric inflammation, and improves performance (Bravo et al., 2011) and gut health. 

Additionally, anti-inflammatory activity of synbiotics (Yang et al., 2012) and phytogenic are synergistically working together since this effect is reached by two different mode of action. Phytogenics anti-inflammatory mode of action is based on activation of NF-κβ factor resulting in an increase of anti-inflammatory cytokines (Moreno de LeBlanc et al., 2011). In contrast, probiotics mode of action is conducted by stabilization of microbiota in the GIT (Windisch et al., 2008), antimicrobial activity (Tiihonen et al., 2010), and enhancement of secretion of endogenous metabolites (Karadas et al. 2014).

Clostridium Difficile
Clostridium Difficile

When these strategies are adopted the impact of outbreaks of coccidiosis and further synergies with Clostridium known as necrotic enteritis, can be diminished. The explanation of this synergism in this particular case is due to the competitive exclusion principle (Oliveira et al., 2000) and immune modulation activity of synbiotics (Lin et al., 2008). On the other hand, phytogenics promote a better metabolism of nutrients, improved feed efficiency, multiple biological properties, such as antimicrobial, anti-oxidative and anti-inflammatory effects (Brenes and Roura, 2010).

REFERENCES

Atuma et al., 2001. The adherent gastrointestinal mucus gel layer: thickness and physical state in vivo. Am J Physiol Gastrointest Liver Physiol. 280: G922–G929. https://doi.org/10.1152/ajpgi.2001.280.5.G922

Food and Agriculture Organization of the United Nations and World Health Organization Working Groups Report (2001). Guidelines for the evaluation of probiotics in food. http://www.who.int/foodsafety/fs_management/en/probiotic_guidelines.pdf

Gibson, GR and Roberfroid, MB. Dietary modulation of the human colonic microbiota; introducing the concept of prebiotics. J. Nutr 1995 June:125 (6) 1401-12

Patterson, JA and Burkholder, KM. Application of prebiotics and probiotics in poultry production. Poultry Science, Volume 82, Issue 4, 1 April 2003, Pages 627–631, https://doi.org/10.1093/ps/82.4.627

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