Newborn calves are very susceptible lo disease, as their immune system is functional, but not fully developed. The most frequently diagnosed diseases of prc-weaned dairy calves arc diarrhea or respiratory disease. Most pathogens (Rotavinis, Coronavirus, Cryptosporidium, Escherichia coli, Salmonella, bovine herpes virus 1, bovine respiratory syncytial virus, parainfluenza 3 virus, Mycoplasma bovis, Pasteurella multocida, Mannheimia haemolytica, etc.) become infective through inhalation or fccal-ora! contact. Biosecurity refers to management practices designed to prevent the introduction of pathogens into herds or the spread of pathogens within a herd that could harm the health of the herd