Before melamine-laced milk killed and sickened Chinese babies and led to recalls around the world, the routine spiking of milk with illicit substances was an open secret in China's dairy regions, according to the accounts of farmers and others with knowledge of the industry. Farmers here in Hebei province say in interviews that "protein powder" of often-uncertain origin has been employed for years as a cheap way to help the milk of undernourished cows fool dairy companies' quality checks. When the big companies caught on, some additive makers switched to toxic melamine