They Shoot Horse-Poisoners, Don't They?

Who would intentionally poison a horse? And not just one, a bunch of horses. Even the pregnant mares! WTF?

Ranch owner Debbie Tomin says they discovered the sick horses on Thursday morning, along with "a feed mix of sliced apples and carrots, which disguised the bitter oleander." So it wasn't just someone walking up to the horses with a bunch of flowers. This was intentional, and they meant to really mess with the horses.

Considering these were show horses and not just your average ponies, I'm guessing it was a competitor. Because otherwise, someone was just targeting horses, and that's messed up. What did ponies every do to you?