While African and Asian cattle continue to produce only A2 beta-casein, the A1 version of the protein is common among cattle in the western world. [9] The A1 beta-casein type is the most common type found in cow's milk in Europe (excluding France), the USA, Australia and New Zealand. [1] :20 On average, more than 70 percent of Guernsey cows produce A2 milk, while among Holsteins and Ayrshires between 46 and 70 percent produce A1 milk.