Influence of Dietary Sorghum Starch on Growth Performance, Digestibility Coefficient and Some Hepatic Enzyme Activities in Hybrid Red Tilapia ( Oreochromis mossambicus × Oreochromis niloticus ) Fingerlings

A 120-day feeding trial was conducted to investigate the effects of dietary sorghum starch on growth performance, feed utilization, apparent digestibility coefficient (ADC) and some hepatic enzyme activities regulating glycolytic and gluconeogenic metabolic pathways of fingerlings hybrid red tilapia (Oreochromis mossambicus × O. niloticus) with mean initial body weight of 10.9 ± 0.2 g. Five diets containing graded levels of sorghum starch (15%, 20%, 25%, 30% and 35%) were formulated. The results demonstrated that weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and net protein utilization (NPU) values increased with increasing dietary sorghum starch up to 30%. Hepatosomatic index, plasma glucose, triglycerides, liver glycogen and liver lipid concentration of fish significantly increased with increasing dietary sorghum starch level (P<0.05). ADC of starch decreased significantly with increasing sorghum starch level over 30%. However, whole body compositions and ADC of protein and lipid showed no significant differences. Dietary sorghum starch supplements tended to enhance gluconokinase and pyruvate kinase activities of the liver but insignificant differences were observed in activities of hexokinase, phosphofructokinase-1, fructose-1, 6-bisphosphatase and glucose-6-phosphatase in the liver for all dietary treatments. Based on WG and FCR results, the appropriate dietary sorghum starch supplementations of fingerlings hybrid red tilapia (O. mossambicus × O. niloticus) can be incorporated up to 30% of diet.