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Nutrition: probiotics

ISSN 2398-2977

Podcast: Nutrition: probiotics


  • Probiotics have been defined as 'a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance'.
  • Within the EU only registered live culture strains may be fed to animals.

Equine digestive system

  • Indigenous gut microflora:
    • Composition incorporates a population of 400 bacterial species.
    • Symbiotic relationship undergoes a constant selection and fluctuation.
  • Role:
    • Digestive (fermentation of fiber and starch).
    • Protective (prevention of establishment of potential pathogenic micro-organisms).
  • Factors inducing changes of stable gut microflora are influenced by dietary and environmental conditions the most significant of which include:
    • Stress: transport, birth, parturition, castration or other surgery, performance/competition, illness or injury, fear. Within the gut the trend during stress is for Lactobacillito decrease and coliforms to increase, resulting in an alteration of the gut microflora which may   →   diarrhea.
    • Antibiotic therapy: suppression of microflora (beneficial and non-beneficial).
    • Changes in diet: type or quality.

Microbes commonly utilized in probiotics

  •  Lactobacillus acidophilusLactobacillus casei,  Lactobacillus delbrueckiisubsp bulgaricusLactobacillus plantarumBifidobacterium bifidumEnterococcus faeciumStreptococcus  thermophilusBacillus subtilisPediococcus pentosaceusSaccharomyces cerevisiae,  Saccharomyces boulardii,  Aspergillus oryzaeand Torulopsisspp, Streptococcus lactisand Lactobacillus rhamnosus.
  • Although yeasts do not become integrated into the resident intestinal microflora, their presence has been shown to increase fiber and nutrient digestibility.
  • Yeasts are also able to survive in the anaerobic environment of the hindgut while many of the bacteria above cannot. Yeast species are, therefore, able to provide support in the hindgut where much digestion in the horse takes place.

Characteristics of a quality probiotic

  • Ability of the constituent microorganisms to withstand the gastric pH and be effective throughout the gastrointestinal tract.
  • Recommended dosage of probiotics can vary but generally falls in the range 1 x 10*7 to 1 x 10*9 cfu/day.
  • A quality probiotic must remain viable in various formulations with extended shelf life.

Probiotic use

  • Re-establishment of disrupted gut microflora following antibiotic therapy, surgery or anesthesia.
  • Re-colonization of intestinal microflora during and following bacterial gut infections   Intestine: salmonellosis    Gastrointestinal: clostridiosis  or long-term parasitic burden   Strongyle infestation: large  .
  • Stabilization of the gut over a period of time when the diet is changed or re-establishment of disrupted microflora following an abrupt dietary change, in type or quality.
  • Stabilization of the gut prior to, and during, stressful periods such as transport and castration   Testis: castration - overview  , and other periods when appetite is affected.
  • A placebo-controlled study in horses with acute enterocolitis showed that the length of time diarrhea persisted was significantly shorter in those administered Saccharomyces boulardii.

Probiotic modes of action

  • Compete with pathogenic bacteria (competitive exclusion) for adhesion sites or intestinal substrates:
    • Bacterial antagonism and/or interference.
    • Bacteriocin production.
    • Alter toxic metabolites to the benefit of the horse.
  •  Saccharomyces cervisiaespecifically has been shown to maintain pH in the cecum and colon, thereby supporting microfloral balance and has been demonstrated to stimulate activity in the hindgut of fiber-digesting bacteria.
  • Promote digestibility of nutrients.
  • Support vitamin production and absorption by the "good" bacteria.
  •  Saccharomyces boulardiihas been shown in animal and human models to inhibit toxins A and B, both secreted by Clostridium difficile. The yeast may directly break down the toxins and/or modify how the body responds to them.
  • Another study (poultry) showed that colonization of Salmonellawas lessened with administration of Saccharomyces boulardii. A possible mechanism of action for this is Salmonellabinding to the Saccharomycescell wall instead of the intestinal lining and then being excreted.
  • Stimulate immunity by:
    • Humoral responses.
    • Stimulation of macrophage activity.
    • Stimulation of secretion of IgA.


  • Probiotic organisms are generally taken from library sources that are classified as GRAS (generally regarded as safe) and with their lack of toxicity do not have any contraindications at recommended dosages.
  • Variations in dosage occur with:
    • Whether being administered prophylactically to maintain microfloral balance or after clinical signs have appeared due to a disruption in microflora.
    • Regularity of administration.


  • Usually 5 days prior to, eg transport and for as long as considered necessary or as directed by a veterinarian.
  • More chronic conditions may require frequent or continuous administration.


  • As an oral dosage.
  • Probiotics are available as powders, liquids, pastes or as feed additives.

Select appropriate administrative method depending on ease and/or regularity of administration.


  • Generally 5 days prior to anticipated environmental or dietary change.
  • In young animals post-parturition, after abrupt feed changes, at castration, pre- and post-transport, at weaning, during and/or following antibiotic administration and during foal heat.
  • In adult animals for the restoration of microbial balance post-antibiotic treatment, colic   Abdomen: pain - adult  , abrupt dietary change, and laminitis   Foot: laminitis  . For maintenance of microbial balance, administer during antibiotic treatment and stressful event, eg illness/injury, perioperative period, competition.

Variations in response to probiotics

  • Factors of the probiotic include:
    • Number of colony forming units.
    • Method of preparation.
    • Storage conditions.
    • Contamination.
    • Poor viability.
    • Micro-organism taxonomy.
    • Survival within the intestinal tract.
  • Factors of the animal include:
    • Status of the gut flora.
    • Frequency of dosing.
    • Growth phase of the animal.
    • Changes in the diet.
    • Degree of stress.

Prebiotics and other digestive enhancers

  • Alternatives to antibiotic growth promoters have been sought in livestock feed industry.
  • Some are now being used for horses to enhance digestive function.
  • Often found in formulations with probiotics.
  • Useful for all horses and ponies with compromised gut function due to stress, diet change, etc.
  • Horses on a high starch, low fiber diet should also benefit.
  • Phosphorylated mannanoligosaccharides (Bio-Mos):
    • Complex carbohydrates derived from the cell walls of Saccharomyces cerevisiaestrains of yeast.
    • Bio-Mos is said to agglutinate specific pathogenic gram-negative microbes.
    • Removal of pathogenic species allows beneficial species to proliferate.
    • The specific bonds that join the Bio-Mos molecules cannot be broken by mammalian enzymes.
  • Short-chain fructo-oligosaccharides (scFOS):
    • Thought to be a specific energy source for beneficial species of bacteria, including Bifidobacteriaand Lactobacilli.
    • Beneficial species proliferate and through competitive exclusion can suppress pathogenic species.
    • The specific bonds that join the scFOS molecules cannot be broken by mammalian enzymes.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Chen X, Kokkotou E G, Mustafa N et al (2006) Saccharomyces boulardii inhibits ERK1/2 mitogen-activated protein kinase activation both in vitro and in vivo and protects against Clostridium difficile toxin A-induced enteritis. J Biol Chem 281 (34), 24449-24454 PubMed.
  • Gobert J, Bertin G & Julliand V (2006) Digestive fate of Saccharomyces cerevisise CBS 493 494, fed at 3 different concentrations to horses. Reprod Nutr Dev 4(Suppl 1), S95.
  • Desrochers A M, Dolente B A, Roy M F, Boston R & Carlisle S (2005) Efficacy of Saccharomyces boulardii for treatment of horses with acute enterocolitis. JAVMA 227 (6), 954-959 PubMed.
  • Qamar A, Aboudola S, Warny M et al (2001) Saccharomyces boulardii stimulated intestinal immunoglobulin A immune response to Clostridium difficile toxin A in mice. Infect Immun 69 (4), 2762-2765 PubMed.
  • Castagliuolo I, Riegler M F, Valenick L, LaMont J T & Pothoulakis C (1999) Saccharomyces boulardii protease inhibits the effects of Clostridium difficile toxin A and B in human colonic mucosa. Infect Immun 67 (1), 302-307 PubMed.
  • Grela E R & Semeniuk W (1999) Probiotics in animal production. Medycyna Weterynaryjna 55, 222-228.
  • Line J E, Bailey J S, Cox N A, Stern N J & Tompkins T (1998) Effect of yeast-supplemented feed on Salmonella and Campylobacter populations in broilers. Poult Sci 77 (3), 405-410 PubMed
  • Flachowsky G & Schulz E (1997) Feed supplements and their significance for performance and ecology. Arch Anim Breeding 40, 101-107.
  • Matteuzzi D & Ferrari A (1996) Gastrointestinal microbiology in human and animal. Annali di Microbiologica ed Enzimologia 46, 211-214.
  • Sedas V T P, Kubiak K N W & Lopez G R (1996) Probiotics and their future. Archivos Latinoamericanos de Nutricion 46, 6-10.
  • Art T, Votion D, Mcentee K, Amory H, Linden A, Close R & Lekeux P (1994) Cardio-respiratory, hematological and biochemical parameter adjustments to exercise - effect of a probiotic in horses during training. Vet Res 25 (4), 361-370 PubMed.
  • Moore B E & Newman K E (1994) Influence of feeding yeast culture (Yea-Sacc1026) on cecum and colon pH of the equine. J Anim Sci 72 (Suppl 1), 261.
  • Glade M J (1991) Effects of dietary yeast culture supplementation of lactating mares on the digestibility and retention of the nutrients delivered to nursing foals via milk. J Equine Vet Sci 11, 323-329.

Other sources of information

  • European Food Safety Authority (2006) Opinion of the Scientific Panel on Additives and Products or Substances used in Animal Feed on the Safety and Efficacy of the Product "Biosaf, Sc 47", a Preparation of Saccharomyces cerevisiae, as a Feed Additive for Horses. EFSA J 384, 1-9 Website:
  • Frape D (2004) Equine Nutrition and Feeding. 3rd edn. Blackwell Publishing Ltd, UK. ISBN: 1405105984.
  • Tannock G W (1999) Probiotics - A Critical Review. Horizon Scientific Press.
  • Fuller R (1997) Probiotics 2 - Application and Practical Aspects. 1st edn. Eds: Chapman & Hall.
  • Ewing W N & Cole D J A (1994) The Living Gut - An Introduction to Microorganisms in Nutrition. Context.
  • Fuller R (1992) Probiotics - The Scientific Basis. 1st edn. Eds: Chapman & Hall.