The dietary protein requirement of the Malaysian mahseer, Tor tambroides (Bleeker), and the lack of protein-sparing action by dietary lipid

Abstract

Two sequential feeding trials were conducted, firstly, to determine the optimal protein requirement for Tor tambroides (Bleeker) fingerlings, and secondly, to investigate the potential protein-sparing effect of dietary lipid when dietary protein is below the requirement. In Experiment 1, triplicate groups of hatchery-raised F 1 generation of T. tambroides were fed semi-purified diets containing one of five dietary protein levels (30 to 50%) for 8 weeks. Fish of initial weight 20.9 ± 0.1 g were fed close to apparent satiation in two equal feedings per day. Growth performance and feed conversion ratio generally improved with increasing dietary protein ( P < 0.05) and polynomial regression analysis revealed a maximum specific growth rate at 48% dietary protein. This corresponded to a protein to energy ratio of 26 mg protein per kJ gross energy. In Experiment 2, a 3 × 2 factorial design was employed in which six diets with 30, 35 or 40% protein and 10 or 15% lipid, respectively, were fed to triplicate groups of T. tambroides (initial weight 0.67 ± 0.15 g) at close to apparent satiation for 12 weeks. No interaction ( P > 0.05) between dietary protein and lipid levels was observed for all growth parameters determined indicating a lack of protein-sparing action by dietary lipid. Daily feed intake was slightly lower in fish fed higher protein diets but dietary lipid level had no apparent effect. Hematocrit and body-organ indices were not significantly affected by diet. Whole-body proximate composition and tissue lipid and protein content were generally not affected by diet even though high fat deposition was observed in the visceral cavity and liver of fish possibly indicating the excess energy content present in all the experimental diets. This study provided the first reported data on the nutrient requirement and body composition of T. tambroides, a mahseer species with aquaculture potential.