I remember many years ago, my late uncle was telling me that he received a donation letter from one of the several humane societies here in the US. They were asking for some amount, $15 or $25 dollars which would be used in catching a feral cat, sterilizing it, and then releasing it. He said the wrote back to them offering to send them $1 which would take care of 50 cats if they would use it to buy a box of 50 .22 bullets (that was the price at the time) which they could use to shoot each in the head after they went to the trouble of trapping them.
He was a farmer, so he was no stranger to getting rid of pest animals around the farm.
Still, spreading poisoned bait sounds like a bad idea. Too much potential for an unintended outcome. They should just trap them and kill them.