Vis a vis keeping the ram away from the ewes until you want him to go about his business, but keeping him close enough to ensure that all parties remain interested, would a river suffice? The field into which I will turn out my ewes is on the opposite side of the river to that in which Roger the Ram resides. The river is about 7 metres wide and the fields on either side are fenced with 0.8 metre stock proof fencing, a strand of barbed wire and an electric top wire (at 1 metre high). Is this likely to be effective in keeping them apart?