The short answer mtca, is no there is no pre or pro-biotic product I recommend. While there have been some positive research, it is very limited. For specifics see https://horseadvice.com/horse-equine/horse-care/nutrition-feeds-feeding/probiotics/ , What I do recommend is that you go through our article on Nutrition Overview, https://horseadvice.com/horse-equine/horse-care/nutrition-feeds-feeding/nutrition-overview/ ,and carefully evaluate your feeding regimen to see if it carefully follows the recommendations and, with consultation with your veterinarian, to slowly adjust your feeding regimen.
DrO