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The effects of high-carbohydrate diets on endocrine status and gene expression of hepatic metabolism enzymes in genetically improved farmed tilapia (GIFT) juveniles (Oreochromis niloticus) at different sampling times were investigated. Two isonitrogenous (28% crude protein) and isolipidic (5% crude lipid) diets were formulated to contain 40% gelatinized wheat starch (WS) or glucose (GLU). Diets were assigned to triplicate groups of 30 fish (initial weight: 51 g) for 42 days. At the end of the trial, there were no significant difference in growth between WS group and GLU group. Hepatosomatic and visceral index and liver glycogen in juveniles were not significantly influenced by high-carbohydrate diets on Day 42 (P > 0.05). Plasma glucose was higher in the GLU group than the WS group from Day 7 onwards. Data on gene expression showed that G6PD, but not GK and G6Pase, were affected by high-carbohydrate diet. The levels of G6PD in the GLU group on Days 35 and 42 were significantly higher than those in the WS group. Serum IGF-I levels of both groups significantly decreased on Day 42, whereas serum insulin levels were unaltered by high-carbohydrate diet. The serum GH level decreased significantly in the GLU group compared with the WS group. Overall, our data suggest that high-glucose diets were efficiently used as an energy source by GIFT tilapia juveniles, and significantly affected liver lipogenic activity and serum GH levels.

The effects of rearing temperature on hepatic glucokinase (GK), glucose-6-phosphatase (G6Pase) and Glucose-6-phosphate dehydrogenase (G6PD) activity and gene expression were studied in GIFT (genetically improved farmed tilapia) tilapia fed a high carbohydrate diet containing 28% crude protein, 5% crude lipid and 40% wheat starch. Triplicate groups of fish (11.28 g initial body weight) were fed the diet for 45 days at 22 °C, 28 °C or 34 °C. At the end of the trial, final body weight of juvenile at 28 °C (59.12 g) was higher than that of the fish reared at 22 °C (27.13 g) and 34 °C (43.17 g). Feed intake, feed efficiency and protein efficiency ratio were also better at 28 °C. Liver glycogen levels were higher at 28 °C, while plasma glucose levels were higher in the 22 °C group. Significant (P

Stocking densities and long term zero culture water exchange rate effects, on biological performances, hematological and serum biological indices of Genetically Improved Farm Tilapia (GIFT) strain cultured in tanks were investigated. The trial was divided into four groups with three replicates each, conducted under natural photoperiods for 30 days; data were analysed using one way ANOVA. Results showed that, high stocking densities and zero water exchange rate negatively affected the biological performances, hematological and serum biochemical indices of GIFT tilapia juveniles. Feeding efficiency, specifc growth and survival rates were significantly decreased. Hematoogical indices: red blood cells, white blood cells, Hemoglobin, Hematocrit and platelet decreased as stocking density increased. Indices of liver function (Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) activities) were significant increased. Serum glucose levels, an indicator of cortisol released in blood were increased as stocking density increased. Meanwhile, total protein, triglyceride, cholesterol, triiodothyroxine, thyroxine levels in the blood serum showed downward regulation under the same experimental conditions. This paper would provide useful scientific knowledge on biological performances and physiological responses of GIFT strain tilapia to stressors like high stocking density and zero water exchange. Research with different fish sizes and water exchange rates should be further conducted.