Having fed cattle (NOT something I ever imagined myself doing), the cattle all snorting around the trough makes sense. It wouldn't be a big trough, just the first one. He's going to be putting feed in other troughs, but trust me, ALL the cows are going to head for the first one, and yes, it can be dangerous. The cows, in my experience, are way worse than the bulls.
You do have to open the thing as quickly as possible. They don't give you time to muck around, so while it's not a simultaneous pair of events, hefting the bag and cutting it open happen pretty close together -- if you know what you're doing. This I learned the hard way.