The player should receive a bounty of 5 gold for attacking farm animals. This is the case for all farm animals in Skyrim (cows, goats...)
However, when attacking a farm animal in Rorikstead, no bounty is received.
I've included a possible fix.
This fix also stops farm animals (members of the 'FarmAnimalsFaction') from reporting crimes committed against members of their own faction.
For example: when attacking a chicken in Riverwood (in Vanilla Skyrim and USSEP) the player gets a bounty of 5 gold. But when you attack the cow in Riverwood the player receives a bounty of 5 gold and a bounty of 40 gold for assault.
I think this is incorrect. But I guess it's open for debate.
Happy modding,
J.