I'm kind of in the same boat, but I don't YET have a some experience with coyotes around pig farms. I became acquainted with the manager of a pig form here in Wyoming and he was telling me how the coyotes near the farm have become numerous and somewhat brave, so he's going to allow me to set up near the feeder bins and call coyotes. I'm planning on going out this weekend and trying the property out.
This manager was telling me how the pig farm will have a sow die giving birth or have still born piglets, so they have a carcass pile that usually gets fed on by coyotes, fox, crow etc...
The farm doesn't have any trouble with coyotes coming into the pens because the hogs are kept and fed inside a temperature regulated building. Their biggest problem is the raccoons that are getting into the feed bunks and barns night. Currently they're using live traps and cat food to rid them, but they are having more success catching feral cats...a win in my book because I have a hate-hate relationship with cats.
On an interesting side note.
He was also telling me about a time some years ago when the farm had scientists come out who were researching different methods of sterilizing coyotes. They had a dozen or so pens of coyotes right there on the pig farm where they were doing their research. The coyotes had tracking devices implanted in them and apparently a couple got out and were shot by a few local fellas. After this incident the coyotes were released throughout the region. True or not, its an interesting story.
I don't know if this helps you or not, but thought I'd give some you some info I found interesting. Hopefully after this weekend I'll have a better idea on how to hunt pig farms.
Best of luck!