Recommended amount is 1-2 grams per once or twice per day, or at the advice of your veterinarian.
Turmeric (active compound is curcumin) has been shown to be anti-inflammatory. The amount of curcuminoids in the plant turmeric is about 3%. This is the extract, similar to what you would find in a health food store, which is 95% cucuminoids.
There is much written about curcumin on the internet. One of the websites that I like is:
Approximately 2 grams per US teaspoon.
Disclaimer: This product is not intended to diagnose, treat, cure, nor prevent any disease. If your horse experiences any adverse effects from using this supplement, discontinue use and contact your veterinarian. For use in animals only.