It has been suggested that colostrum is important not only for direct protection from pathogens but also for proper development
of immune systems in piglets. In this study, we focused on the effect of colostrum ingestion during the first 24 h of life on early
postnatal development of piglet immune systems. Thirty-six piglets from five litters were divided into colostrum-fed (CoF) and
colostrum-deprived (CoD) groups. The former group was allowed to suckle normally while formula milk was fed to the latter
group during the first 24 h of life. At the weaning period, the concentrations of fecal immunoglobulin (Ig) A and plasma IgG
as well as the number of blood leukocyte subsets were analyzed. Fecal IgA and plasma IgG concentrations in the CoF group
were more than twice as high as those in the CoD group (P < 0.01). In addition, the number of blood B cells was significantly
higher in the CoF group than that in the CoD group (P < 0.05). This study demonstrates that colostrum ingestion during the first
24 h plays a significant role in early postnatal development of both mucosal and systemic immunity of piglets.