PRRS vaccination is widely used to induce humoral and cell-mediated protective immune (CMI) responses. However, vaccination alone is often insufficient to induce protective immunity. Mannan oligosaccharide (MOS), the outer cell wall of yeast, is known to potentiate both cell-mediated and humoral immunity. This study aimed to evaluate the potentiating effect of MOS on the PRRS-specific antibody production in the sows and subsequent antibody transfer to their offspring.  Thirsty seven sows were randomly assigned to 3 experimental groups: control, supplementation of 400 and 800 ppm MOS in feed during gestation. The PRRS-specific antibody in the sera of sows and their piglets were measured one day before and after parturition, respectively. The results showed that at 400 ppm MOS as feed additive for sows were effectively enhance PRRS-specific antibodies (by ELISA S/P ratio) but not for neutralizing antibody. At 800 ppm MOS in sows’ feed, significantly increase of neutralizing antibody was showed. In conclusion, supplementation of MOS in sows’ feed would be helpful to strengthen the effect of PRRS vaccination.

Key words: Humoral immunity, Mannan oligosaccharide, PRRS