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How to Evaluate a Probiotic

07 Jul, 2016

How to Evaluate a Probiotic

Probiotics have proven to be beneficial when used in appropriate circumstances with an effective protocol. How do you know if the specific probiotic preparation you are using is going to be effective and if it is, just how effective is it? Recent research reported by the University of Kentucky and Ohio State University has provided practical guidelines for probiotic evaluation.

Does Probiotic Strain and Dose Matter?

University of Kentucky researchers compared three Lactobacillus strains individually and a mixture of all three strains in their ability to change the microbiome in equines. Lactobacillus acidophilus, Lactobacillus reuteri and Lactobacillus buchneri were each dosed at 1 billion CFU’s in an equine in vitro trial. L. acidophilus and L. reuteri were more effective at increasing pH, increasing lactic acid utilizing bacteria and decreasing starch utilizing bacteria compared to

  1. buchneri. However, the ability of all three strains to alter the equine microbiome when combined in equal amounts to provide a total of 1 billion CFU’s was significantly less than any of the three individual strains dosed at 1 billion CFU’s. This research illustrates two major points:
  2. There is a minimum CFU’s that needs to be supplied by each individual probiotic strain in order to be effective. Products that combine multiple probiotic strains where each individual probiotic strain contributes less than 1 billion CFU’s should not be expected to effectively alter the equine microbiome even if the sum of all individual probiotic strains combined is greater than 1 billion CFU’s.
  3. Not all probiotic strains effectively change the equine microbiome even when dosed at 1 billion CFU’s or more.

Ohio State University researchers conducted a two part study to evaluate two commercial probiotics in horses. In part 1 a commercial probiotic supplying 1 billion CFU’s of Lactobacillus acidophilus was dosed to mature quarter horse mares via top dress on a standard hay and grain diet. This probiotic significantly altered the microbiome in mares as measured by microbial rRNA markers. In part 2 of the study a commercial probiotic supplying 10 million CFU’s of Lactobacillus acidophilus was dosed to growing quarter horse mares via top dress on a standard hay and grain diet. This probiotic had no effect on the microbiome as measured by microbial rRNA markers. The results of this study indicate that:

  1. Lactobacillus acidophilus can significantly alter the microbiome in mature horses.
  2. In agreement with results from University of Kentucky research, Lactobacillus acidophilus should be dosed at 1 billion CFU’s or greater in order to effectively alter the microbiome in growing or mature horses.

Does a Probiotic have to be alive?

University of Kentucky researchers investigated the effect of dosing the equivalent of 1 billion CFU’s of live Lactobacillus reuteri versus equal amounts of autoclaved or dead Lactobacillus reuteri. Both treatments significantly altered the microbiome but there was no difference between live and dead Lactobacillus reuteri. Upon further investigation the researchers determined that the “probiotic effect” of Lactobacillus reuteri was due to unique peptides found in the cellular membrane of Lactobacillus reuteri hence this particular probiotic strain could be dosed dead or alive to achieve the same benefit.

What makes a probiotic more effective?

The major points elucidated up to this point are 1) not all probiotic strains are effective at altering the microbiome, 2) Most probiotics require at least 1 billion CFU’s per day to be effective and 3) at least some probiotic strains are equally effective when dosed either dead or alive. So how can we make effective probiotic strains even more effective? Dosing probiotics in combination with prebiotics has been proven through multiple research and clinical studies to increase the beneficial effects of probiotics. For clarification: a probiotic is defined as a bacteria strain that has a beneficial effect on the health of the digestive system whereas a prebiotic is defined as a carbohydrate that serves as either a food source for probiotics and/or provides a beneficial effect on the health of the digestive system. Therefore, when evaluating commercial probiotics it is best to choose one that provides both prebiotic ingredients and probiotics.

Example Evaluation: Table 1: Probios® Equine One Oral Gel1 versus ADR™ Paste2



Probiotic Strains


1 Dose

Total CFU’s

per Dose





15 gm

150 million




30 gm

55 billion


1Product information obtained from Probios® web site as of February 15, 2016

2Product information obtained from EquiVision product label as of February 15, 2016

Based on information presented in Table 1, ADR™ Paste should be expected to provide superior performance compared to Probios® Equine One Gel for the following reasons:

  1. ADR™ provides over 55 billion CFU’s of probiotics per dose compared to a mere 150 million for Probios®. As discussed above, university research has illustrated that 150 million CFU’s may be inadequate to provide a consistent beneficial effect.
  2. ADR™ provides prebiotics in combination with probiotics whereas Probios® provides probiotics only. Research has proven that prebiotics dosed in combination with probiotics provides superior benefits compared to either prebiotics or probiotics dosed independently.


Harlow, B.E., Lawrence, L.M., Kagan, I.A. Harris, P.A. and Flythe, M.D. Exogenous lactobacilli mitigate microbial changes associated with grain fermentation in vitro. J. Eq. Vet Sci. 2015, 35:400-417 (No. 38).

Barnhart, K, Reddish, J.M., and Cole, K. Supplementation with Lactobacillus acidophilus influences microbial diversity in the gastrointestinal tracts of healthy horses. J. Eq. Vet Sci. 2015, 35:400-47 (no. 68).

Patel, R., DuPont, H.L. New Approaches for Bacterotherapy: Prebiotics, New-Generation Probiotics, and Synbiotics. 2015. Clinical Infectious Diseases 60(S2):S108-121.


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