We had a mama cat come up here and we started feeding her. She was dumped. We have the same problem. We live at the very end of a private road, but there's another gated private road that crosses the T at the end of the road and people come down and drop off animals. I had to kill an injured pit bull here, had a spikey collar on. I'm sure it was a fighting dog past its prime and the injuries were severe looking cuts from dog bites.
That mama cat took up on our back porch. She started dropping kittens. In a few years we had 6. They get killed by coyotes and bobcats and even hawks and owls around here about as fast as they can multiply, now, but mama is still here. We feed 'em, but I don't do anything else for 'em. If I find one injured, I'll euthanize it, myself. A .22 bullet is about 4 cents, no biggy. They're beneficial to me, though, keep the mice population down. What ones make it past the barn cats the inside kitties (well cared for) take out.
Funny, my Lab is a trained retriever. She has a very soft mouth. I told her to get a mouse the cats had tortured and was still alive thinkin' she'd crunch it with those big teeth. Nope, she picked it up and brought it to me like it was a dove or something. ROFL! Good dog, though.