I've castrated many a boar pig which is very similar to the procedure for human beings. You realize that its permanent, excruciatingly painful and with long lasting complications don't you? Sometimes, the scrotum can become gangrenous. Even if performed under anesthesia, it will hurt for some time afterwards. Some guys that have it done opt for silicon implants to look normal.
Every time I think about a knife getting close to my cock and balls I get incredibly hard. Sometimes I hold a knife to my balls and fantasize about somebody taking them off and eating them.
You could do as we have with cattle. A special metal band is clamped on above the scrotum sack. It cuts off the circulation to the testicles and they eventually dry up and fall off. Clamping is another possibility. It ain't pretty. But it gets the job done. I'd advise people not to eat testicles unless they are properly cooked. Try dipping them in egg and cracker meal. Then deep fry them. :-)