Can you ride a horse if your on your period?

Not exactly. If you're in the habit of wearing pads instead of tampons and have to work with stallions, yes this is true. But if you're wearing tampons and/or working with geldings, no this is not true. With stallions, if you're wearing pads, it's possible they may try to court and mount you from getting "turned on" from the pheromones they smell from the pads you're wearing. So to prevent this, just switch to tampons.