Antibiotic use in dairying is primarily for disease treatment. The primary ailment treated with antibiotics is clinical mastitis(Ruegg 2015). Mastitis, an infection in mammary gland tissue, can take a variety of forms where some are not bacterial in origin. Inflammation can also be difficult to detect. Imperfect and costly on-farm tests are available (Merriman et al. 2014), where the California test is perhaps the best known. Bacteria-originated mastitis is contagious where antibiotics can serve the purposes of reducing the rate of spread and providing earlier eradication.