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intestinal microflora in animals

Gastro-intestinal microflora and its influence on the host

Published: November 13, 2007
By: Michaela Mohnl - BIOMIN
Gastro-intestinal microflora and its influence on the host - Image 1

A well established intestinal microflora is crucial for the health of our animals, especially if we expect high production performance. A healthy normal microflora is the first line of defense to invading pathogens and thus it is extremely important for the ability to fight off infections with enteric pathogens. Furthermore, it is also necessary for a well functioning and effective digestion of nutrients, resulting in good growth performance parameters.

Besides nutrient absorption, the intestine plays an important role as the biggest immune organ of the body. It is hence part of the body‘s defence system and represents an important barrier against invading pathogens. In addition to general defence mechanisms, the immune system, with its unspecific and specific reactions, helps to protect against pathogenic microorganisms. The intestinal microflora also suppresses pathogens.

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Intestinal microflora

The intestinal microflora comprises all bacteria, protozoa and fungi present in the GI tract and consist of approximately 400 to 500 different species. In monogastric animals approximately 1014 microbes can be found in the intestine. The initially sterile digestive tract is colonised by microorganisms soon after birth. Diversity and total number of the microorganisms increase from the small intestine to the caecum. The microflora is subdivided into the main, the satellite and the residual flora (Gedek et al, 1993). The main flora is composed mainly of anaerobic species (Bifidobacteria, Lactobacillae, Bacteroides and Eubacteria) which produce lactic acid and other short-chain fatty acids. The satellite flora represents approximately 1% and consists mainly of Enterococci and E. coli. The residual flora is below 0.01% and is composed mainly of harmful microorganisms.

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Eubiosis vs. Dysbiosis

The composition of the intestinal microflora is a dynamic equilibrium among the various species and changes with the conditions in the digestive tract. When the microflora is in equilibrium, the proportion of the main flora is over 90%, the satellite flora is around 1% and the residual flora is below 0.01% (Figure 1). This state is called "Eubiosis“. In this situation, the host and the microflora live together in symbiosis, meaning, with mutual benefit. The host provides good living conditions. In exchange, the intestinal microflora, when in the state of eubiosis, supports the host with essential activities. If this relationship is severely disrupted, the condition is called "Dysbiosis“. Dysbiosis can have a significant negative impact on the host animal. The growth of potential pathogens, which are normally kept at a very low level, can dramatically increase. Bacterial toxins are produced which may harm the host (Figure 2).

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Possible reasons why eubiosis turns into dysbiosis

Nutrition is the most important factor influencing the composition and metabolic activity of the intestinal microflora. Feeding errors and substantial dietary changes, low-quality feed components and inadequate feed hygiene all compromise eubiosis (Figure 3). For example the change from a low protein diet to a high protein diet favors the growth of certain bacteria such as clostridia and reduces the conditions for lactobacilli or bifidobacteria. Furthermore every kind of stress can have a direct impact on the gut microflora because stress influences the release of digestive secretions and the type and frequency of intestinal movements (peristalsis).

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The feeding of probiotics can be used as a tool to favourably influence the microbial community in the gut to achieve or reestablish the state of eubiosis. In general, the following modes of action of probiotics are assumed:

  • Competition with pathogenic bacteria for space, intestinal attachment sites and nutrients
  • Change of environmental conditions in the intestine (Lowering of pH through increased production of volatile fatty acids (VFA) and lactic acid)
  • Production of antimicrobial substances (lactoferrin, lysozyme, bacteriocins... "Natural antibiotics“)
  • Modulation of intestinal immune response

Intake of probiotics should result in the creation of gut microecology conditions that suppress harmful microorganisms and favor beneficial microorganisms, and ultimately enhance gut health.

In a study which was carried out by the Department of Animal Nutrition of the Agricultural University of Athens (Mountzouris et al, 2007) the efficacy of Biomin® Poultry5Star on broiler nutrition was investigated in comparison to the AGP Avilamycin. Biomin® Poultry5Star is a well-defined, multi-strain synbiotic product which combines the beneficial effects of probiotic strains from the genera Enterococcus, Pediococcus, Bifidobacterium and Lactobacillus with prebiotics.


Treatment effects on parameters of broiler performance, cecal microflora composition, concentration of volatile fatty acids, and activities of glycolytic enzymes were determined. Overall growth performance expressed with the broiler productivity index was comparable between the Biomin® Poultry5Star group and the AGP group (Figure 4). The administration of Biomin® Poultry5Star resulted in a beneficial modulation of the cecal microflora (Figure 5). Concentrations of bacteria belonging to Bifidobacterium spp., Lactobacillus spp., and gram-positive cocci were significantly (P ≤ 0.05) higher in the Biomin® Poultry5Star group in comparison to the control and AGP group. The Biomin® Poultry5Star group had significantly higher (P ≤ 0.05) specific activity of α-galactosidase compared to the control and the AGP group and β-galactosidase activity was significantly higher (P ≤ 0.05) in comparison to AGP group (Table 1). Bacterial glycolytic enzymes play an important role in the fermentation of undigested carbohydrates.

Gastro-intestinal microflora and its influence on the host - Image 6

Gastro-intestinal microflora and its influence on the host - Image 7

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Biomin® Poultry5Star treatment displayed a growthpromoting effect that was comparable to Avilamycin treatment. In addition, administration of Biomin® Poultry5Star modulated the composition and, to an extent, the activities of the cecal microflora, resulting in improved eubiosis and enhanced gut health.

About the author

Name: Michaela Mohnl
Position: Product Manager
Education: BOKU - University of Natural Resources and Applied Life Sciences, Vienna, Spec. Food and Biotechnology
Master thesis: Medium design and Optimization of the fermentation process for a Ochratoxin A detoxifying yeast
Since 2003 Doctoral thesis: Development of the fermentation process for the production of a competitive exclusion product for poultry meeting the regulatory requirements for registration in the EC
Since March 2005: Product Manager, Biomin GmbH Austria
Address: Biomin GmbH, Industriestrasse 21, 3130 Herzogenburg, Austria
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Michaela Mohnl
K R Ranganathan Naidu
K R Ranganathan Naidu
3 de junio de 2010

The subject was good and intresting and very knowledgable for the poultry sector and the veterinary students in india

Dr. Anjum
Dr. Anjum
28 de mayo de 2010

Thanks, Its article about Gastrointestinal microflora and its influence on the host is Very Helpful

Dr. Anjum

Gobinath shanmuga sundram
Gobinath shanmuga sundram
17 de abril de 2008

Can you provide the details of probiotic supplementation per chick when we spray at probiotics at hatchery level? What is the recommeded dose of probiotic per chick or hen or broiler finisher?
Thank you.
With regards,

Dr S Gobinath

Dr S. Chandrasekar
Neospark Drugs and Chemicals Pvt.Ltd
23 de diciembre de 2007

Very interesting article about gastrointestinal microflora and its influence on the host. Can you give the details of probiotic supplementation per gram of feed?

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