Dairy cows infected with mastitis are generally diagnosed when they are mature, around two and a half years old. Studies have shown that cows can become infected as early as six months old, going 45% of their life untreated. It is suggested that producers look for mastitis at the time of preg check or AI when the animal is being handled anyway. Infected heifers should be separated from non-infected heifers to avoid comprimising the dairy herd.