Yup, explain that you will need to use barbed wire so suggest they run an electric wire on their side of it.
But alternatively, yes you can put a strand of barbed wire a couple of feet in front of the main fence, at cattle chest height. We used to do this in places in Cumbria, cheaper and quicker than a complete refence when the main fence wasn't wholly reliable any more and we didn't want to do a complete refence just yet.