Performance of genetically improved Nile tilapia compared with red hybrid tilapia fed diets containing two protein levels

Abstract

A 10-week feeding trial was conducted to investigate the interaction between tilapia genotype and dietary protein level on the growth, feed utilization efficiency and body composition of Nile tilapia [Oreochromis niloticus L., F9 generation of genetically improved farmed tilapia (GIFT) strain] and red hybrid tilapia (Oreochromis sp.). Two isoenergetic diets (15.5 kJ g−1 diet) containing 25% or 35% crude protein were formulated and fed to triplicate groups of tilapia (12.8±0.2 g) at a fixed daily ration of 4% of their body weight. The growth performance of the GIFT tilapia fed 25% or 35% dietary protein was significantly higher (P<0.05) compared with red tilapia at either protein level. Increasing the dietary protein level by 10% led to a further 10% increase in the final weight of GIFT tilapia but no further increase was observed in the weight gain of red tilapia. Growth was influenced by the interaction between diet and tilapia genotype. Feed conversion ratios were 14% and 33% better in GIFT tilapia compared with red tilapia fed the 25% or 35% protein diet respectively. Protein efficiency ratio and net protein utilization were influenced by both diet and tilapia genotype, but not the interaction between the two. The apparent digestibility coefficients of dry matter and protein did not differ significantly between the two diets and tilapia genotypes but lipid digestibility was 1.2–4.7% higher for the GIFT tilapia. Tilapia whole-body protein content was significantly influenced by both diet and tilapia genotype. The higher growth potential, better feed utilization efficiency and higher body protein content of GIFT tilapia compared with red tilapia should have a positive impact on tilapia farming in terms of production costs.