Security firm: thieves fed to dogs so much sleeping pill that it affected on their health

Perhaps, each of us ever passed by a fence with the plate" Here I protect", meaning that the house is guarded by a dog. Unfortunately, one only the plate will not prevent theft, and can be endangered both your house, and animals. Why it is important to protect the house even if it is protected by a dog? How it can rescue an animal and prevent the thief? .