Last time I checked , there are very few to no geldings in the wild. Unless of course that they are feral or the BLM rounds up bacheler groups and gelds them to manage the rangelands from overpopulation. As for stallions that have dirty sheaths, they don't have many foals and/ or get their mares uterine infections then they can't have live births due to bacterial infections. This is prety rare in the wild as proof is in the pudding... the open range is very overpopulated and overgrazed as the bleeding hearts always know better in the best method to manage public lands. Resulting in Feral horse overpopulations while other wild species starve and suffer.