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

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.