A supplement that actually alters the metabolism of a horse is a drug. Before you drug your horse you should have a reason you’re doing it and that reason should be supported by a SOAP
Subjective
Objective
Assessment
Plan
In selecting the drug you should know what it’s properties are, what it does, how it does it, and the proper dosage.
Then when you start you should have a record of what you had before the drug was used and how physical or mental state of the horse has changed. By “record” I mean a “physical record.” Since most of us have smart phones it’s easy to create a photographic or video record. Even a text record is pretty simple.
The minimum for any drug is that it is efficacious (for the condition it’s being used to treat) and is safe in the proper dosage and manor of use.
Drugs that have gone through a formal approval process (like Adequan and Consequin) have been proven on both counts. Any other drug that has met the same standards would be the same. I don’t know of any formal approval process of any kind for “supplements.” The industry that makes these things has fought regulation “hammer and tong” for years to ensure that such a process does NOT EXIST! So when you use one of these unregulated substances you are are a veterinary experimenter using your horse as a “guinea pig.”
If folks are cool with using their own horses as experimental animals then that’s fine. I’m not.
G.