Mad Cow Rules Hit Sperm Banks' Patrons By Rob Stein Washington Post Staff Writer Wednesday, August 13, 2008; Page A01 When Julie Peterson decided to have a baby on her own two years ago, she picked a tall, blond, blue-eyed Danish engineer as a sperm donor to match her own Scandinavian heritage. But when she went back to the sperm bank to use the same donor to have another child, she was stunned to discover that the federal government had made it impossible. "I just cried," said Peterson, 43, who lives in North Carolina. "I was in complete shock. I...