thanks everyone for the interesting discussion and advice. I've been using blocks in bait boxes and the volume of poison taken has reduced drastically, I'll keep these regularly maintained as prevention of future problems.
As many of you have said, this is not something any of us really want to do, however, I am always trying to cause the least harm, but we do raise animals for meat and that life and death are part of the cycle for all things on the smallholding, we are always wanting to therefore ensure its as quick and painless as possible.
Again thank you all for your thoughts