You can get high enough voltage in ground so that livestock can feel it through their water system. Make up separate grounding field. Often a problem when not adequately built. Underground cable cannot be spliced and placed underground - will eventually short out. Place underground cable in in plastic pipe whenever it goes under a walkway or roadway.
Stones can eventually break the instillation causing a short.
Take care in not leaving long ends on finishing up electric fence wire ends - later can get bent and cause a short in the fence.