The animal’s digestive system has an extremely important role in providing the necessary nutrients and their assimilation from the organism. It is known that only a healthy digestive tract can ensure the successful realization of the genetic potential in animals. The tendency is that from now on the role of the antibiotics in maintaining the gut health will be even more reduced. That imposes the need of future optimization of the biosecurity and animal nutrition, as well as the application of the most modern technologies in the production and application of feed additives.
The animal feeding schedule needs to be optimized and balanced in such a way that they can maintain a stable microflora and good health status of the intestinal tract. Whether antibiotics are supplied as growth promoters or for the treatment of intestinal infections, their use should be severely restricted in the coming years, while not compromising with intestinal health. Probiotics, prebiotics, synbiotics, phytobiotics, enzymes, organic acids, nucleotides, bioactive proteins and peptides, amino acids and some microelements are all feed additives, which have proven positive effect as modulators of the gut microecology. Their mechanisms of action on the gastrointestinal microbiota are complicated, diverse and can be direct or indirect.
E. Barba (2019) classifies the main mechanisms of action of feed additives, used for gut health improvement, in four groups:
Probiotics. The term probiotic is relatively new and Salminen S. (1996) determines them as foods, containing alive bacteria, beneficial for the health. Subsequently, many definitions appear, and they all come together to the understanding that probiotics, as preparations of living microorganisms, enhance the endogenous microflora. In 2002 The World Health Organization officially accepts the following definition for the probiotics: “live microorganisms which when administered in adequate amounts confer a health benefit on the host” (WHO, 2002).
Currently, this is the most widely used and accepted definition, as it includes all of the applications of probiotics as live microorganisms, and is not restricted only to the intestinal homeostasis benefits. Thus, two main points are considered of highest importance: 1. Probiotic preparations should include live microorganisms; and 2. The desired health benefits are related to the amounts of the preparation administered.
The probiotics are living microorganisms, which are administered to the animals in order to settle in the digestive system, thus beneficially altering the intestinal microflora. The mechanism of action relies on the competitive exclusion effect – limiting the attachment surface of unwanted microorganisms (salmonella, clostridia, colibacteria, etc.) and/or the antagonistic properties of probiotics against them. The effect of probiotics is somewhat similar to that of antibiotics, since in both cases it results in a favorable change in the gut microflora. In antibiotics, this is achieved by directly suppressing the unwanted microorganisms, while probiotics have more of an indirect effect via stimulation of the beneficial bacteria. Currently, the most commonly used probiotics in the animal breeding industry belong to the genera Bacillus, Lactobacillus, Bifidobacterium, Enterococcus and Saccharomyces. These probiotics have been shown to have the ability to enhance the immune response, reduce populations of pathogenic bacteria, stimulate the beneficial microbiota, and aid digestion.
Although probiotic bacteria can survive passage through the stomach, they do not form permanent colonies in the body and need to be renewed. Therefore, they should be taken regularly in order to maintain the health benefits. In addition, if necessary, the bacteria must be in a capsule to protect them from the stomach acids in order to reach the intestines alive and ready to fulfill their purpose - boosting immunity, especially after infections and antibiotic intake, inhibiting the development of harmful bacteria, regulation of the intestinal microflora, etc.
Prebiotics. Prebiotics are defined as indigestible nutrients that favorably affect the host by selectively stimulating growth, activity or both of one or more beneficial bacteria in the gastrointestinal tract. Prebiotics are the food of probiotics. Prebiotics are nutrients that are not digested by digestive enzymes and are not utilized in the upper digestive tract. Thus, they reach the large intestine, where they ferment to short-chain fatty acids and stimulate the development and survival of beneficial microorganisms, that are normally present there, or alternatively - provided with the feed. The most commonly used prebiotics in animal husbandry are mannan-oligosaccharides, fructo-oligosaccharides, inulin and lignocellulose. Prebiotics are used in birds and pigs because in ruminants they break down in the abdomen and do not reach the large intestine.
Synbiotics. Synbiotics are a combination of probiotics and prebiotics, which produces a better effect than administering the two products alone.
Phytobiotics. These include aromatic plants (herbs and spices), plant extracts and volatile fatty acids. The main principle of action is based on the volatile fatty acids (thymol, carvacrol, etc.) and the polyphenols. Phytobiotics have been shown to be able to modulate the immune response as well as the intestinal microbiota (via antimicrobial action against pathogenic bacteria).
Enzymes. There can be no nutrients digestion and good absorption without enzymes. Enzymes are complex proteins produced by living cells that trigger chemical reactions in the body. Exogenous enzymes are added to the rations because they improve the utilization of the nutrients contained in the feed, as well as positively affect the gut microbiota profile. The feed contains cellulose, pectin substances, beta-glucans, oligosaccharides and other substances that are not digested in the animal body by endogenous enzymes. The most commonly used enzymes are phytase, xylanase, beta-glucanase and protease. Scientists have found that the mannanase enzyme increases the production of butyrate and maintains gut health. Butyrate is short-chain fatty acid, an indispensable source of energy for cells in the gastrointestinal tract and is involved in maintaining the health of the intestinal epithelium. Thus, Vemo 99 Ltd. has developed a series of high-quality enzyme-based feed additives, ensuring for the proper feed digestion, and providing for the healthy gut microbiota:
It is clear that probiotics, prebiotics, synbiotics and enzymes stimulate the beneficial microbiota and have a positive effect on gut health, however with various complex mechanisms of action. Short-chain polysaccharides and oligosaccharides obtained by enzymatic degradation may also exhibit prebiotic properties. The use of digestive enzymes is often associated with increased length of the intestinal villi, leading to better absorption and utilization of nutrients. This increases the absorption surface of the intestinal tract, leading to increased feed efficiency and hence growth performance. Therefore, when considering the effects of enzymes on the digestive processes in the animal body, it is important to consider their effects on gut health.
Prof. Sabka Surdjiska