From this source:
What about the “pour-on” form?
NO. The pour-on form is designed as a fly repellant to be poured onto and stick for many weeks to the haircoat of livestock. The liquid medium of the pour-on is NOT INGESTIBLE. If you buy and drink the pour-on after reading this, you are stupid. ONLY THE 1% INJECTABLE solution or the horse paste may be ingested. Period.
Hope this helps
I stand corrected, and retract my previous post regarding pour-on Ivermectin. It’s for pouring onto cattle, not for pouring onto their feed.