From another trapping forum:
1) take a handfull of horses hooves, the closer to the frog (middle of the hoof) the better.
2) cut it up if you want or leave them in larger pieces.
3) Take hooves and put them in a 1 gallon jar and add water and let set in the sun. Don't put the lid on tight or you will have a mess, it will make some gas and blow the jar up. wait the longer the better (weeks)
4) If you want to speed this process up, take your hooves and water and boil them together for about an hour, allow to cool and then put it in the jar.
Always put the hooves in the jar with the water after boiling.
Put the bait/lure in a squirt bottle and give a good squirt then cover the dirt hole with a plug of grass.
If you have an unlimited supply of hooves, put a piece in the dirthole, it makes the set better.
Fox, Badger, and yes, Coyotes love it, but so do town dogs, so be careful, you may catch Fido.
This stuff will last forever, once you take some out for use on your trapline just fill your jug back to the top with water.