No, technically, they have no adverse impact on the pets. The electric dog fences come with a dog collar that slightly shocks when the pet tried to cross the boundary. These collars have around seven levels of shock. You can adjust it according to the dog’s nature and how much shock you want to give them. Even with the highest level of shock, there is no negative impact on your beloved pet. However important is to ensure that the collar is in good condition and is a high-quality, guaranteed product.