The immunostimulatory role of an orally administered yeast cell wall preparation from Saccharomyces cerevisiae (NutrifermTM) was assessed in the Indian major carp, rohu (Labeo rohita). Fish were fed a diet containing the preparation for 15 days and then returned to the con- trol diet for 20 days. Non-specific immunity was assessed at the end of the experimental feed- ing period (day 0) and on days 10 and 20. In vitro oxidative radical production, phagocytosis of leukocytes, nitrite production, and proliferation of lymphocytes were determined. All four para- meters remained stable in control fish but, in fish fed the supplemented diet, reached a peak on day 10 and remained higher than in the control until day 20, indicating that ingestion of the diet containing the yeast cell wall preparation for 15 days had significant immunostimulatory effects
