Abstract: An in-line feed supplement additive system comprises an additive hopper which can be disconnected from the feed line of a feed system and inverted to allow for cleaning of the additive hopper. The system includes a controller which, determines the proper speed of the motor which drives the conveyor of the additive hopper based upon the dosage of the additive and the flow rate of feed through the feed line. Further, the controller monitors the load on the additive hopper motor during delivery of additive to ensure a substantial constant rate of delivery of additive to said feed.