Goosy is absolutely write aminopyralid can be fatal for plants that's why we stack our horse manure for 12 months before using it we have been using horse manure for a number of years now without any problems its just making sure you don't use fresh horse manure
You should always rot down manure otherwise it will deplete nitrogen from the soil, which is the opposite of what you want and can burn plants.
Aminopyralid in manure is a different matter altogether and can persist for long periods in stored manure. This is the RHS advice:
"Unfortunately, residues in manure can remain for extended periods, even up to two years.
Long term storage is an option. The manure must be fully rotted down over several years before use."