I had a greyhound years ago we rescued him after hed finished racing,he was due to be destroyed that week.the first time he walked through our door he grabbed our cat,i punched him on the nose and he let go,fortunatly the cat was fine.We never had any more issuses with the cats!!!!in the years that followed the dog and cats slept together.Soon after we first got him i took him onto the common,he got a little dog and started to shake it,we managed to free it and it was fine,however ben stayed on the lead for a long while after that.After a while he was ok with smaller dogs and we had no more problems.we got ben when he was 4 and he lived with us until he was 16,he was great with the kids,i would never have used a e-collar all he needed was time to adjust.