Angela, if you have trapped, S/N & released feral cats then you know they can be given a needle for sedation so they can be handled before putting them under for surgery.
The exact same thing is done when a feral cat needs to be Euthanized.
No one wants these cats to die - but if that is the only option their lives should not be ended in one of the cruelest forms of torturous deaths out there.
Does your store sell animals?