Enhancement of the innate immune system and disease-resistant activity in Cyprinus carpio by oral administration of β-glucan and whole cell yeast

The effects of dietary beta- (1,3) glucan and whole cell yeast (Sacharomyces uvarum) on the immune response and disease resistance to Aeromonas hydrophila were investigated in Cyprinus carpio. beta-(1,3) glucan was extracted from the yeast. Both beta-(1,3) glucan and whole yeast were incorporated into the diet at 1% level and fed to common carp C. carpio for a period of 60 days. Control and treated fish were exposed to A. hydrophila on the 30th and the 60th day of the experimental period. Dietary supplementation of glucan significantly increased the white blood cell count in fish on the 60th day (2.91 +/- 0.04 x 104), and the highest nuetrophil nitro blue tetrazolium (NBT) activity was also observed in glucan-fed fish (30th day). A consistent increase in neutrophil (NBT) activity was also observed in whole cell fed fish until the end of the experiment. Similarly, beta-(1,3) glucan and whole cell yeast enhanced the serum lysozyme activity from the 15th day onwards but higher activity was reported on the 30th day in glucan and the 60th day in whole cell yeast-fed fish. Suplementation of beta-(1,3) glucan protected the fish from A. hydrophila infection. Nearly 75-80% of the fish survived pathogen exposure (relative percentage survival). However, only 54-60% survival was observed in the whole cell-fed fish. beta-(1,3) glucan and whole cell yeast protect the fish from pathogens by enhancing the cellular and humoral immune response in C. carpio.