Effects of inclusion of hydrolyzed yeast on the immune response and performance of piglets after weaning

The aim of this study was to examine whether yeast derivative (YD) based on brewery yeast hydrolyzate added to a post-weaning diet affected performance and immune responses in weaning pigs. One hundred and twenty pigs were allocated to 20 pens, taking initial body weight into account, and were distributed into two groups as follows: a negative control diet and the same diet supplemented with 2 g YD/kg. The YD used was Progut® (Hankkija Oy/Suomen Rehu, Hyvinkää, Finland). At days 7 and 21 of the experiment, half of the piglets per group were challenged intramuscularly with 1 mL of a solution of 20% sheep red blood cells (SRBC) in sterile phosphate buffered saline (PBS). At days 0, 14, 21 and 28 of the experiment, blood samples from the challenged piglets were obtained and acute-phase proteins (Pig-MAP), natural antibodies of the IgM- and IgG-isotype binding to keyhole limpet hemocyanin (KLH), and agglutinating antibody titers to SRBC were measured. Yeast derivative inclusion improved feed conversion ratio (P=0.025) for the overall period, tended to increase IgG (P=0.087) and IgM (P=0.061) antibodies in serum-binding KLH, and increased (P=0.037) SRBC agglutination titers. Collectively, these data suggest that YD supplementation as 2 g Progut®/kg to weanling pigs triggered the immune system to a more responsive state without penalizing the animal performance which could potentially be beneficial for overcoming disease challenges. Piglets fed with 2 g Progut®/kg for 28 days after weaning also showed an improvement in feed conversion ratio.