Ornery

Stubborn is a pet trait featured in The Sims 3: Pets. It's only available for horses.

''Stubborn horses are stubborn and do not mix well with Sims. You do not even need contact with foreign Sims or be touched by them and may even occur Sims who do not like. So repugnant these properties may be, have stubborn horse by a strange affinity for evil and vile Sims.''