Our Virgil was rough with the cats when he was 3 1/2 months. For maybe a month I kept him on a leash while walking with treats in my pocket and when he wanted to chase I said NO KITTY and gave a treat when he listened. After a month I did the same thing with out a leash. He still occasionally wants to chase one cat in paticular, but NO KITTY seems to stop it pretty fast. I also have chickens loose and he has never bothered them. We now have 5 kittens 2 mos old and he never bothers them, even when they were 1 month old. I watched close cause sometimes they acidentally step on a kitten, but hes been real careful. Our fist V had 1 cat & 4 kittens sleep in his bed with him for a long time.