The present study was designed as a 3x2 factorial experimental design to investigate the effects of dietary lysine on growth performance, body indices, feed intake, feed efficiency, whole-body nutrient composition, and amino acid deposition in the SUZ and GIP strains of Oreochromis andersonii. Three diets with varying levels of lysine were formulated for a feeding trial involving triplicate groups of fish with an initial weight of 15 g over six weeks in a recirculating aquaculture system. The study also aimed to measure the experimental diets’ Apparent Digestibility Coefficients (ADC) of dry matter, crude protein, crude lipids, and total carbohydrates. The study results revealed that although no significant interactions were observed between dietary lysine levels and fish strains for most parameters, exceptions were noted for the condition factor (CF) and ADC of crude protein. Dietary lysine levels significantly influenced final weight, weight gain, thermal unit growth coefficient (TGC), protein efficiency ratio (PER), and ADC of dry matter, regardless of the fish strain. Fish-fed diets with the highest lysine content had superior final weight, weight gain, and TGC. PER was the lowest in fish receiving the lowest lysine level. Moreover, the fish strain significantly influenced the final weight and accumulation of isoleucine, phenylalanine, and alanine, with the GIP strain exhibiting better performance. These findings suggest increased growth and higher lysine requirements in the improved GIP strain compared to the SUZ strain during the juvenile phase, potentially indicating a change in dietary lysine needs due to genetic enhancements.
Keywords: Growth performance, Lysine, Nutrients, Strain, Tilapia.