Originally Posted by Ladytrails
Dreamcatcher is right - in fact, if this is partly cow feed, there can be antibiotic in there which is truly deadly poisonous for horses. Don't feed it until you figure out whether it's tainted with cow feed or just a mechanical problem with the pellet size.
I do believe you are refering to Rumensin or Bovatec used in milking cow feeds. You would need large amounts of either drug to effect your horse. Im not saying to give your horse the feed in question, but if you did, there shouldnt be reason to hit the panic button if either drug is in the feed.