Rabbit Maintenance and Burdock

I have 3 angora rabbits: one French, Jake,  and two German crosses, Toby and Bart.  Jake is prone to what I call “poopy butt”.  He tends to have soft droppings, and then he sits in them.  I brought him inside last night to dry off, then went to clip off the soiled wool (he’s at about 2″) this morning.  That part went pretty well, then I discovered the fur under his chin/chest was one big matted mass from burdock.  Yikes! Burdock are like incredibly strong little velcro bits.  They do not go well with angora wool.  He wasn’t very happy, but I did manage to get everything clipped out.  Now I need to check the other two rabbits to see if they are hiding more of the same.  Sigh…they were all fine 2 days ago-it doesn’t take long to get messed up.  The rabbits are all due to be shorn the end of March, so I would like to keep their coats nice.  This was especially frustrating, since Jake had a really nice coat with no other matting.  The burdock is coming in with our hay.  We first noticed the problem with the sheep.  I try now to go through all the hay before putting it in the cages/feeder, but some of the burdock must have still slipped by.