Department of Agricultural Technology, Faculty of Technology, Mahasarakham University, Maha Sarakham 44150, Thailand
The growth performance, body composition and blood chemistry of Nile tilapia (Oreochromis niloticus) reared under different salinities (0 ppt, 5 ppt, 10 ppt and 20 ppt) and different diets (0.5% yeast (Saccharomyces cerevisiae) supplement diet and basal diet) were investigated during 90 days. Fish fed with yeast supplement diet and reared at 5 ppt water salinity showed significantly improved (p<0.05) growth performances as weight gain (WG), specific growth rate (SGR) and average daily growth gain (ADG) compared to fish fed with basal diet. Feed conversion ratio (FCR) of fish fed with yeast supplement diet reared at all salinity levels (0, 5 and 10 ppt) was significantly lower than fish fed with basal diet (p<0.05). Cortisol levels of fish fed with yeast supplement diet were significantly lower than those of the basal diet group at 10 ppt (p<0.05). Both fish groups showed significant increases in cortisol and malondialdehyde (MDA) levels at salinity of 10 ppt compared to fish reared at 0 and 5 ppt (p<0.05). Crude protein content of fish fed with yeast supplement diet and reared at salinity levels of 0 and 10 ppt was higher than those fed with basal diet (p<0.05). Fish fed with yeast supplement diet showed a decrease in crude lipid content under salinity regime up to 10 ppt (p<0.05). Thus, Nile tilapia fed with yeast supplement diet at 0.5% showed improved growth performance, body composition and blood chemistry under salinity treatments (0 ppt and 5 ppt).