Are ridglings sterile

"Ringling" or "ridgling" is a common term for a stallion that has been partially castrated; these animals still have some testicular tissue and depending on what is left could still be fertile. This was popular for circus stallions (such as Ringling Brother's) because the stallion would still develop the secondary sex characteristics (thick neck, heavy muscling, etc.) but wouldn't be as quick to chase off after a mare in heat or have a nasty temper.