One other thing I worked @ a packing house when I was 20. Every now and then a bull would come into the knocking shute that didn't get phased by that knocking hammer with the retractible bolt. Guess what they used then?
An old H&R single shot with ,you guessed it ,low brass bird shot. Of course it was shot from only 2-3 feet away but it dropped em like a ton of bricks. Also scared the hell out everyone in the kill room because they never warned anyone first.