Are you referring to drenching a horse with a fresh dropping. If so then it works extremely well.
I witnessed the treatment of one of the school ponies that had developed severe diahorrea and had lost so much weight he was emancipated and dehydrated.
The vet prepared a fresh dropping by liquidising it in a bucket of warm water. A nasal tube was fed down to the stomach and the liquid poured in. Pony recovered within days and lived for many, many years.