[Desflahd]

If you don't want him messing with chickens tie a rope to his collar and walk him close to some. Once he starts paying attention to them give him a jerk and a no. Repeat as needed even if you have to take him away. Once he knows you don't want him messing with a chicken put a shock collar on him and give him a bump with it when he starts paying attention to one. It won't happen over night but be consistent and it can happen. But either commit to it and do it right or don't bother.