MarisaG wrote:
yeah, unluckly I cannot cut off the testicles of cats which do not belong to me 

You'd be surprised.
Several local rescues trap local feral cats and bring them to me to neuter them. When we neuter feral cats, we always cut off the tip of the left ear so the cat's can be identified if they're trapped again later. Last week I had a guy come in with his cat for vaccines. I noticed the left ear was tipped and asked if he'd adopted it from one of the cat rescues.
He said. "No he got that in a cat fight. Came home with it like that one night a few months back".
He then said he wanted to schedule the cat for a neuter so it wouldn't fight like that any more. I lifted the cat's tail and had a look. Sure enough, he'd been in a fight...and I had won.

Doc