It's for puppies. They just inject something into the testes and they die.
There are many non-surgical ways to sterilize farm animals. Some put a tight
rubber band on the scrotom and it falls off in a few weeks. There are many more
ways. So far I don't believe there is a non-surgical spay yet though they do
have hormones for female cats call Ovarid. It keeps them from going into heat
so I'd assume they wouldn't get pregnant. I'm not sure though.