Round here, a couple of years ago, there was a problem with - and now I must be PC - travelling people, whose arrival in the neighbourhood coincided with the disappearance, at night, of numbers of lambs which were within relatively small enclosures and outlying buildings. Nothing could be proved, so it might just have been a coincidence. However for so long as there are people who will buy cheap meat, consciously avoiding the asking of the questions why it is so cheap and what is its provenance, in the current economic climate such circumstances will continue to occur. Sadly, I fear that there's no solution to this problem - save to keep the animals in fields large enough that the b****rs can't catch them or that such a din is made that neighbours are alerted or the would be thieves decide that the effort and/or risk is so great that they'll give up and - sad to say - go elsewhere!