Supplements can be a slow burn - it may take months, or even up to a year or more, for supplements to really start showing a noticeable difference. However, you may start to notice a difference after a month or so. Hopefully, you'll start to notice more solid droppings and a happier, more contented horse. I've noticed subtle changes in my horses within 4-6 weeks when changing supplements (but not always - it depends on the supplements and whether the ingredients work).