1. IN law, the onus is on a farmer to keep his stock in. A farmer cannot rely upon a neighbour fencing his portion of a field so as to keep his stock in the field. The farmer is the one at fault if his stock stray. Accordingly, here, your neighbour is liable for any animals which trespass upon your property. He cannot call in aid the fact you haven't fenced your portion of the field. If he wishes to put in animals into the field, then he must ensure they are kept in, whether by electric fencing or some other means, as he is liable if they stray from his ground.
Hi, Thank you very much for your help, it puts our mind at ease, and we will get it done we just wanted to know the law on the issue, we would rather do it when we are ready and have it done properly and not just a rushed job that will have to be redone again, you have been a great help, much appreciated.