Across large swaths of the United States, powerful winter storms are bringing heavy snow, ice, and dangerously cold conditions , prompting warnings for people and animals alike to prepare and stay safe through the weekend and beyond. Veterinarians and animal-welfare groups are urging pet owners to protect animals from frostbite, hypothermia, and exposure to hazards like road salt and antifreeze. In these trying conditions, backyard chickens the long symbols of self-sufficienc