Effects of fructooligosaccharides on cortisol and glucose contents of serum in Tilapia Oreochromis niloticus under two environmental stress

This study was conducted to determine effects of fructooligosaccharides on cortisol and glucose contents of serum in tilapia (Oreochromis niloticus) under two environmental stress. Different ratio of fructooligosaccharides including 0 g/kg (control group), 1 g/kg(group A), 3 g/kg (group B), 5 g/kg (group C) were mixed in basic feeds added with 6% chinese herbal formula additive. Nile tilapia were fed with these mixed feeds for 90 d and then some were conducted with bacteria stress trial and the others were exposed to crowding stress (35 g/L) for 48 h. Cortisol and glucose contents of serum were investigated at 0 h, 3 h, 12 h, 24 h, 36 h and 48 h, respectively. The results of bacteria stress showed that the cortisol and glucose contents of all groups had been elevated greatly after exposed 24 h, of which group A and group B had significantly difference compared with the control group. As time went by, the contents of all groups began to decrease, and eventually the test group had parallel to the control group. The crowding stress results showed that all of the groups had the same trend as the results of bacteria stress test. The difference between these two tests was that the cortisol and glucose contents of the latter one reached to the top level on the 12 h and 24 h, respectively. It concluded that 1~3 g/kg fructooligosaccharides could enhance the ability of resistance to harsh environment condition.