Apparently, fat roosters aren't very good at making chicks. The world's largest chicken breeder has discovered that a key breed of rooster has a genetic issue that is reducing its fertility, and that's raising prices for poultry even as beef and pork prices hit record highs. The breed, Aviagen Group's standard Ross male, is sire through its offspring to as much as 25 percent of the nation's chickens raised for slaughter, said Aviagen spokeswoman Marla Robinson. Sanderson Farms, the third-largest U.S. poultry producer and one of Aviagen's largest customers, said it and Aviagen systematically ruled out other possible causes for a decline in fertility before determining a genetic issue was at the root of the problem. The issue is hitting an industry that is already suffering from a short supply of breeder birds. A team of scientists from Aviagen studied the issue and found that the breed's genetics made it sensitive to being overfed, and when the bird got big, he didn't breed as much.