Based on central composite rotatable experimental design and response surface method, the interacting
effects of temperature (20 Ce34 C) and dietary protein level (25%e50%) on hematological parameters
including red blood cell (RBC), white blood cell (WBC) and hemoglobin (Hb) of juvenile Oreochromis
niloticus were studied under laboratory conditions. The experiment lasted for 7 weeks. After the feeding
trial, fish were challenged with Streptococcus iniae and mortality was recorded for within 8 days. Results
showed that the linear and quadratic effects of temperature on RBC, WBC and Hb were highly significant
(P < 0.01). When the dietary protein level was 25%e50%, the RBC, WBC and Hb were increased firstly and
then decreased, but the linear and quadratic effects of protein level were insignificant