Relative to the Whey Protein Isolatw (WPI) that is the key ingredient for Hammer Whey and Recoverite, the milk source is grass-fed cows that do not have antibiotics. Every load that is taken into the plant for processing is tested for antibiotics/hormones and rejected if it contains said. As a result, both Hammer Whey and Recoverite contain the purest form of WPI.