Colostrum was collected and pooled from each of five cows in three experimental groups: group I cows received intramuscular and intramammary inoculations of adjuvanted modified live Ohio Agricultural Research and Development Center rotavirus vaccine; group II cows were injected intramuscularly with a commercial modified-live rota-coronavirus vaccine; and group III cows were uninoculated controls. Pooled colostrum from group I cows had higher (P less than 0.05) enzyme-linked immunosorbent assay (ELISA) immunoglobulin G (IgG1) and virus neutralization (VN) rotavirus antibody titers (ELISA IgG1 = 2,413,682; VN = 360,205) than did colostrum from group II (ELISA IgG1 = 8,192; VN = 4,395) or group III cows (ELISA IgG1 = 5,916; VN = 2,865). The antibody titers of these last two colostrum pools did not differ (P greater than 0.05). Samples of these colostrum pools were fed as daily supplements (percent [vol/vol] in cow's milk infant formula) to 28 newborn, unsuckled, antibody-seronegative, male Holstein calves. Eight calves received no supplemental colostrum. The calves were orally challenged with virulent bovine rotavirus and monitored daily for diarrhea and fecal rotavirus shedding. Diarrhea and rotavirus shedding occurred in the eight calves fed no supplemental colostrum and persisted longest in this group. The pooled colostrum from group I cows protected eight of eight calves from both rotavirus diarrhea and shedding when fed as a 1% supplement. The pooled colostrum from neither group II nor group III cows protected 12 other calves against rotavirus diarrhea or shedding when fed at the same concentration (1%). Six rotavirus-challenged calves fed 0.1% supplemental colostrum from group I cows and two calves fed 10 and 50% supplemental colostrum from control cows displayed partial passive immunity, exemplified by delayed onset and shortened duration of rotavirus-associated diarrhea and virus shedding.