Male Behaviour

Question
I have a three year old neutered male PBP that stays in a house at night, and freely roams our ranch during the day.  (Also have a 2 year old spayed female for companionship) He's recently been showing really aggressive behaviour towards a small group of cattle I have in the small pasture near the house.  He'll grind his teeth and "shoulder" at them, and when they're laying down, he'll either mount them or bite at them until they get up.  He picks on one of my Brahmans particularly, and will run half way across the pasture to get her when she lays down.  She's very docile, and has never threatened him.  

He's never done this before, and I'm not sure how to stop him.  I don't want him hurting my cows, but short of penning him up, I don't know what else to do.

Thanks in advance for your help!

Answer
I cannot explain this behavior.
When a pb roams freely on a farm, they often do things we don't want them to! Pigs are curious, intelligent animals that get bored. Some will interact with bigger animals, or smaller animals, inappropriately!
(I assume BOTH testicles were removed, and he does not have an undescended one)!
I worry about his safety....the chances of him being hurt are high.
We suggest confining/separating him.
Or, motivating him to stay inside .
Good luck,
Priscilla Valentine