I live nearby several pig farms and when you drive past one, there isn't a blade of grass visible. Pigs destroy the land they live on, and as such, they should churn the grass off the blocks in their pen. Possibly creating a muck mud block.
Secondly, pig muck is used as fertiliser commonly on farms. It would be make pigs even more valuable if domesticated pigs were able to drop an item that could be turned into fertiliser using barrels or some form of composter, possibly a new 2x2 block type called muckpile, where you can store their poop. A new tool could be added which would be a muck fork, which could be used similarly to a scythe, spreading muck fertiliser onto up to six crops within reach.
Thank you for reading my ted talk.