Questions

How do probiotics work?

Definition and concept
Dr Roy Fuller defined a probiotic as: “A live microbial feed supplement, which beneficially affects the host animal by improving its intestinal microbial balance.” This definition emphasises the importance of live cells as essential components of probiotics.

The concept of probiotics applied to preventative medicine is claimed to have originated from Metchnikoff. He thought that the longevity observed in the Balkan people was due to the regular consumption of soured milk containing Lactobacillus bulgaricus.

The introduction of a probiotic supplement establishes or reinforces the gut microflora in the newborn foal or disrupted gut.

Probiotics have been shown to work by the following mechanisms:

Competition for nutrients
Within the gut, beneficial as well as pathogenic microorganisms will be using the same types of nutrients and so there will be a general competition for these nutrients to grow and reproduce. This means the more the gut is flooded with beneficial microorganisms, the more competition is created between beneficial and pathogenic bacteria.

Competition for adhesion sites
To prevent being swept away, pathogens need to adhere to sites along the gut wall and beneficial organisms will compete for these sites.

Stimulation of immunity
Probiotics encourage the stimulation of antibody production on both the local and systemic levels.

Direct antimicrobial effect
This can either operate via bacteriocins, which are produced by many species of beneficial lactic acid bacteria or by the production of organic acids, which can either have a direct effect or operate by reducing the pH.

Improvement in digestion  
Probiotic microorganisms add to the healthy microflora by producing enzymes that aid the breakdown of tough polysaccharide molecules, which form the main part of the equine diet; this helps the horse to utilise more nutrients from the food. The microflora also produces vitamins, which supply a secondary source to the horse.

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