To investigate the factors influencing the passive, innate, and adaptive immune system and their effects in beef cattle, three experiments (exp.) were completed. Results from Exp. 1 indicate that there is some influence of birth weight and incidence of dystocia on the passive transfer of immunity from dam to offspring. Results from Exp. 2 indicated that supplemented dams had lower calving ease scores and tended to have greater colostrum production while their calves showed less evidence of mixed acidosis based on blood parameters of pCO2, lactate, and base excess. In Exp. 3, vaccine treatments initiated an inflammatory response with subcutaneous MLV vaccine for IBR and BRSV having greater serum antibodies than the intranasal vaccine. Feed intake and ADG were unaffected by the use of vaccines compared to a sterile saline injection. In well-managed, properly-immunized herds, vaccination can stimulate antibody production without negative effects on feedlot performance.