Intestinal microflora: a very delicate balance among many different microorganisms

The usefulness of the intestinal microbiota

Gut microbiota is one of the most important players in poultry intestinal and general health. During the last years, researchers increasingly focused on this microflora using cutting-edge techniques to detect the composition of the chicken gut microbiota: it is composed of Bacteria, fungi, Archea, protozoa, and virus with the bacterial compartment as the predominant one. These microbes, especially in the upper intestine, use part of the ingested diet as a livelihood but they are extremely useful for the animal. Commensal bacteria compete against pathogens and non-indigenous microbes for the intestinal environment: animals with normal microflora are proved to be more resistant to pathogens infections than germ-free ones. At the same time, these commensal bacteria stimulate the immune system both in its cellular (T cells, immunoglobulin producing cells, and phagocytic cells) and non-cellular (the mucus layer and the epithelial monolayer) component. Furthermore, the microbiota helps the animals as nutritional support, producing energy and nutrients (vitamins, amino acids, and fatty acids) from the ingested feed.

There are associated risks

Among the microbiota bacteria, there are also potential pathogens such as E. coli, as well as pathogenic bacteria that can be present in the environment and can be ingested by the birds. The unbalancing of microbiota equilibrium is called dysbiosis: every kind of stressor can lead to this condition. Intestinal dysbiosis causes low nutrient digestibility, reduced intestinal barrier function, mucosal inflammation, and facilitates bacterial translocation to the bloodstream. In the case of bacterial infections, antibiotic treatments may help but more and more bacterial species developed resistance against commonly used molecules.

Nutrition and feed additives are powerful allies

Prevention is the key: we can help animals maintaining their intestinal microbiota balance through nutrition and feed additives. There are numbers of feed additives with proved antimicrobial activity: organic acids (OA) and nature identical compounds (NIC) are among the most studied and used in poultry feed. These molecules have different modes of action against pathogens. OA passively pass the cellular membrane in the undissociated form. The percentage of molecules in this form is highly dependent on the medium pH. Each OA has a dissociation constant (pKa) indicating the pH at which 50% of the molecule concentration is in the undissociated and 50% in the dissociated form. The lower is the environmental pH compared to the molecule pKa, the higher is the amount of the undissociated form of the OA that enters bacterial cells. Once inside, the molecules dissociate liberating hydrogen ions because of the different pH. These ions lower the cytoplasm pH and the pathogen spends energy to pump them out trying to restore its physiological status. The result is a bacteriostatic activity against pH-sensitive bacteria. At the same time, the anionic part of the OA has a direct bactericidal effect due to its toxicity to the nucleic acids. The vast majority of pathogenic bacteria are pH-sensitive bacteria, while commensal and useful bacteria of the intestinal microflora are part of the pH non-sensitive bacteria. This means that OA have strong antimicrobial activity against pathogens but the commensal ones can deal with the internal pH changing and their growth and function are not affected by the acid.

NIC are phenolic molecules that can form pores in the bacterial membranes: they are the so-called pore-forming agents and have a direct bactericidal activity due to the loss of bacterial cytoplasm and cellular integrity.

The different activities of OA and NIC are extremely useful once combined. They work synergistically: the membrane disruption caused by the NIC facilitates the entrance of the OA and its activity. Different studies demonstrated this synergistic activity showing an extremely stronger antimicrobial effect of these molecules once in combination compared to their activity alone. The combination of OA and NIC can also reduce antimicrobial-resistant (AMR) bacteria growth; furthermore, the combination of OA and NIC together with conventional antibiotics enhances the efficacy of these against AMR pathogens.

Obstacles: how to overcome them?

Both OA and NIC are extremely useful in animal nutrition to modulate the intestinal microflora and face and prevent pathogen infections. On the other hand, they almost completely disappear in the stomach and cannot reach the intestine after the ingestion. In the free form, they can prevent feed degradation as feed preservatives and they are flavoring compounds, but completely unuseful for the intestinal microflora modulation. The active ingredients microencapsulation overcome this problem, bypassing the stomach and liberating OA and NIC directly at the intestinal level. The microencapsulation technology of AviPlus® is studied to release the included active ingredients along the entire poultry intestinal tract.

To take advantage of the synergistic effect of the combination of OA and NIC is necessary the contemporary presence of these molecules in the same intestinal tract. It is important to have both OA and NIC in the same product, but this is not enough: if each particle of the product contains only OA or NIC they will be released at the intestinal level at different points, reducing the combined activity of the active principles. AviPlus® contains all the active ingredients in the same microcapsule that release them together along the intestine, exploiting in the best way possible the synergistic effect. Different in vivo studies demonstrate that AviPlus® can reduce pathogens load along the whole intestine up to the ceca. At the same time, this product can modulate the intestinal microflora increasing the beneficial bacterial species load. Compared to the control groups, treated animals had improved intestinal health and reduced pathology risk. AviPlus® can be a useful tool to maintain the physiological status of the intestinal microbiota and to prevent hazardous dysbiosis.For more information: