Prebiotics and probiotics in horse diet

Undoubtedly one of the fundamental objectives to keep in mind when preparing a diet for horses of any age, sex or work intensity, is maintaining a physiological balance of the so-called microbiota.

What is the microbiota? The microbiota is nothing more than the set of the symbiotic population consisting of bacteria, fungi and protozoa present in the gastrointestinal tract, mainly in the cecum. The microbiota is therefore a complex and changing ecosystem interdependent with the host organism, which by its nature is able to influence the health of the horse and in turn be influenced by it.

The simple variation of the ratios between the different nutrient compartments of the diet, proteins, carbohydrates, lipids and fiber, already in itself influences the composition of the microbiota. However, for many years scientists have identified additives that are particularly effective in optimizing the intestinal flora. We are talking about probiotics and prebiotics.

PROBIOTICS: what they are and what they are for

There are many definitions for probiotics, however probably the best is that of the FAO (2008) which says: probiotics are defined as living organisms, which administered orally at adequate concentrations, provide beneficial effects regardless of their mere nutritional value.

There are many types of organisms on the market that can be classified as probiotics, some are yeasts (a type of fungi) others are lactobacilli (a type of bacteria), however, certainly among all the famous Saccharomyces cerevisiae dominates in terms of diffusion in all areas of animal husbandry, which is a yeast. Not surprisingly, S. cerevisiae is abundantly present in feeds produced by HorseNutrition.

Probiotics exert their beneficial effects in several ways:

• Immunostimulant
  They improve the host's immune defenses by increasing the intestinal barrier, antibody response and cell-mediated response.
• Antimicrobial effect
  They produce various metabolites which are toxic to various pathogenic bacteria.
• Competitive adherence
  Probiotics compete with some species of pathogenic bacteria for the same receptors expressed on the external surface of intestinal cells. In simple words, they reduce the anchoring space and consequently the colonization of the mucosa by potentially dangerous bacteria.
• Inhibition of bacterial toxins
  Probiotics interfere, both directly and indirectly, with the production of various bacterial toxins. In fact, they act both by reducing the production of toxins (inhibition of gene expression) and by limiting the absorption of toxins by binding to them.
• Reduction of lactic acid accumulation
  Probiotics reduce the accumulation of lactic acid, thus limiting the dangerous effects of acidification of the cecal lumen, which in turn can cause laminitis and colic.

PREBIOTICS: what they are and what they are for

Prebiotics are defined as "non-digestible components of foods, which positively influence the development and metabolic activities of some specific intestinal bacteria".

The working principle of prebiotics is not based on the idea of colonizing the gastrointestinal tract with healthy organisms, but rather of favoring the development conditions for the part of the microbiota that interests us.

Chemically, prebiotics are polysaccharides (such as beta-glucans) or oligosaccharides (such as fructo-oligosaccharides, manno-oligosaccharides and galacto-oligosaccharides), and as such, they pass completely undigested in the horse's small intestine, but are then rapidly fermented, i.e. "digested", by the flora present in the large intestine (mainly in the cecum).

The direct and indirect benefits of prebiotics are various and significant:

• Slowing transit and glucose absorption
  Beta-glucans in the intestinal lumen hydrate forming a sort of gel that slows down the advancement of digesta, and especially that reduces the speed of glucose absorption. This is a property of remarkable importance because it leads to a reduction of postprandial glycemic peaks which in turn determines beneficial behavioral effects (less nervous horses) and metabolic effects (normalized insulin secretion).
• Immunostimulants
  Prebiotics are able to stimulate macrophage activity and also to increase antibody production. These effects are reflected in the effectiveness of the body's actions aimed at counteracting the aggression of pathogens, but also in the generic increase of antibody titers. In fact, it has been shown that mares fed with prebiotics secrete colostrum richer in antibodies, thus improving the health status of the foal.
• Inhibitors of pathogenic bacteria
  MOS are also able to inhibit the ability of some gram-negative bacteria, to whose category many pathogens such as Salmonella spp and Escherichia coli belong, to adhere to the intestinal mucosa, thus reducing their possibilities of colonizing the intestine.

In HorseNutrition feeds, both beta-glucans and manno-oligosaccharides (MOS) are added in concentrated form. Both are extracted from the wall of S. cerevisiae, but it is interesting to note that beta-glucans are quite well represented in various foods traditionally elective in horse rationing, such as oats, barley and bran.