Effect of dietary protein and protein energy ratio on the growth performance of lemon fin barb hybrid (Hypsibarbus wetmorei X Puntius gonionotus) larvae

A series of two experiments was conducted to study the optimum dietary protein level and protein to energy ratio of lemon fin barb hybrid larvae. In Experiment ۱, five isocaloric diets (۴۷۰۰ kcal per kg) ranging from ۴۰ to ۶۰% protein in ۵% increments were fed to triplicate groups of lemon fin barb hybrid larvae (initial weight: ۰.۱۰ ± ۰.۰۱ mg per fish) for ۲۱ days. Weight gain of fish was proportional to the protein content of the diet up to an incorporation rate of ۵۰%. Among formulated diets, the diet with ۵۰% protein produced the highest weight gain (۴.۲۶ ± ۰.۰۳ mg). The dietary protein level that yielded maximum growth was ۵۲.۱% based on a broken-line model estimation of weight gain. Based on these results, two dietary protein levels (۵۰% and ۵۵%) were used along with three energy levels (۴۵۰۰, ۴۷۰۰ and ۴۹۰۰ kcal per kg diet) at each protein level in Experiment ۲. The survival of fish fed diets containing ۵۵% protein was significantly lower (p<۰.۰۵) than that of fish fed diets containing ۵۰% protein regardless of the energy level. Weight gain of fish was significantly (p<۰.۰۵) different at all dietary protein and energy levels. The best growth was observed in larvae fed diet ۳ containing ۵۰% protein with ۴۹۰۰ kcal/kg energy with the highest weight gain (۳.۱۲ ± ۰.۰۰ mg), feed conversion ratio (۰.۸۷ ± ۰.۰۲) and protein energy ratio (۹۷.۳۵ mg/kcal).