Antibody response to Influenza booster vaccination in Franches-Montagnes stallions supplemented with Equi-Strath® : a randomized trial

Vet Med Sci. 2018 May;4(2):133-139. doi: 10.1002/vms3.95. Epub 2018 Feb 27.


Bio-Strath® is a plasmolyzed yeast product enriched with herbs, malt, honey and orange juice. In this study, the effect of Equi-Strath® , the adapted product for horses, on the equine immune system was evaluated. A routine influenza booster vaccination was used as a model to study the effects of Equi-Strath® supplementation on the immune response. Twenty healthy Franches-Montagnes stallions with pre-existing antibody levels were randomly divided into a study group (SG, n = 10) receiving 0.06 mL/kg bodyweight of Equi-Strath® , and a control group (CG, n = 10), receiving the same amount of placebo, daily. The supplement and placebo were given from week 1 until week 14 of the trial. After 10 weeks, the horses were vaccinated with a commercial vaccine containing equine influenza strains of the H3N8 subtype. Antibody titres in blood were measured at day 0 before vaccination, and 14 and 32 days after vaccination. In addition, a complete blood count (CBC) was performed on day 0 and day 32. A linear increase of haemagglutination inhibition titres in both groups was observed after vaccination, but with no difference between treatment groups. CBC components remained unaffected by treatment. In conclusion, daily Equi-Strath® supplementation did not affect the adaptive immune response in stallions after a routine commercial H3N8 influenza booster vaccination.

Keywords: antibody titre; equine; influenza; plasmolyzed yeast; vaccination.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Viral / blood
  • Antibodies, Viral / immunology*
  • Hemagglutination Inhibition Tests / veterinary
  • Horse Diseases / immunology*
  • Horses / immunology*
  • Immunization, Secondary / veterinary*
  • Influenza A Virus, H3N8 Subtype / immunology*
  • Influenza Vaccines / administration & dosage
  • Influenza Vaccines / immunology*
  • Male
  • Orthomyxoviridae Infections / immunology
  • Vaccination / veterinary


  • Antibodies, Viral
  • Influenza Vaccines