Abstract
Nile tilapia of an initial average weight of 36.55 ± 0.15 g were stocked in 15 tanks at 20 fish per tank. Five isonitrogenous and isolipidic experimental diets (31.5% crude protein, 7.45% crude lipid) were formulated to replace 0% (D-0 diet), 25% (D-25 diet), 50% (D-50 diet), 75% (D-75), and 100% (D-100 diet) of fish meal (FM) with cottonseed meal (CSM) and blood meal (BM). After 60 days of rearing experiment, results showed that final body weight (FBW), specific growth rate (SGR), feed conversion ratio (FCR), weight gain rae (WGR), protein efficiency ratio (PER), the whole-body crude proteins and ash content exhibited no significant change at D-25, D-50, and D-75 group (p > 0.05) compared to the control. FBW, WGR, PER, SGR, crude protein, and ash were significantly lower, while FCR was significantly higher in D-100 compared to control (p < 0.05). Serum biochemical activities indicated that albumin (ALB), triglycerides (TGs), and total cholesterol (TC) exhibited no significant change (p > 0.05) among all treatments. However, glucose (GLU) concentration was significantly increased in the D-50 and D-75 groups compared with the control group. Meanwhile, alanine aminotransferase (ALT) was significantly lower in the D-100 group, aspartate transaminase (AST) was significantly higher in D-25, D-50, D-75, and D-100 groups, superoxide dismutase (SOD) activity was higher in D-75 group, and glutathione-peroxidase (GSH-Px) was lower in D-25 compared to the control group. These results suggest that D-75 is the optimal substitution level without adverse effects on GIFT tilapia juveniles.