From my own experience, which is admittedly limited, I have found that pigs dont eat anything harmful to them. I understand that bracken can be poisonous, ours rooted it out, leaving it to die, whilst disposing of the bramble roots very enthusiastically. Now they are into sedge. I dont know if Hilary actually ate the bullrushes, but they disappeared when she got into the nearly dry pond. I should go for it.
HM