Based on a 2007 study representing 79.5% of US dairy operations and 82.5% of US dairy cows; antibiotics were used therapeutically by ~85% of US dairy operations to treat cow mastitis and by over 50% to treat respiratory, reproductive and lameness issues. More than 60% of dairies used antibiotics to treat respiratory problems in weaned calves and heifers, and to treat respiratory problems and diarrhea in unweaned calves[3]. To prevent disease and promote healthy growth, 90.1% of US dairy operations practiced dry cow therapy, 18.2% fed antibiotics in heifer rations, and 57.5% fed medicated milk replacer to unweaned calves.