Addition of 5% freeze-dried IBD virus (IBDV)-immune bovine colostrum to the diet of chickens prevented infection when housed in an IBDV-contaminated environment. Four of five chickens receiving 2.5%, and all chickens receiving 0.5% or no IBDV-immune colostrum were infected. No interference with development of an active immunity was found in chickens receiving 5% IBDV-immune colostrum in their diet and vaccinated intramuscularly with modified IBDV.