An effective way of ensuring built-in resistance to disease in calves is to

The most effective way of ensuring built-in resistance to disease in calves is to allow them access to colostrum. Colostrum is the first milk produced by the mother cow immediately after calving. It is rich in antibodies, which are transferred to the calf and help to build its immune system. Without colostrum, the calf's immune system is weakened, making it more vulnerable to diseases. Vaccination, regular veterinary check-ups, proper quarantine, and a balanced ration are also important measures in ensuring the health of calves, but access to colostrum is critical for building resistance to disease.