Effects of dietary protein concentrations on growth and RNA: DNA ratio of rainbow trout (Oncorhynchus mykiss) cultured in Nuwakot district of Nepal

Abstract

The aim of this study was to determine the effects of dietary protein on growth performance of rainbow trout (Oncorhynchus mykiss) in relation to RNA: DNA ratio. Fifty days old rainbow trout larvae (weighing 0.1846±0.0055 g), were cultured in “Trout Village Fish Farm” in Doman of Nuwakot district, Nepal, during February-March, 2011. Culture of trout was done in small netted cages (50 cm X 50 cm X 50 cm) which were maintained in the raceways of fish farm and the stocking density was 320 fish/m3 i.e. 40 fish in each cage. Altogether, three raceways were used for the experimental purpose each with three cages set as three replicates for each feeding regime. Fish in three raceways were fed with three different types of feed viz.: diet containing 40% protein (D1), 50% protein (D2) and regular commercial diet considered as control (C) respectively. Size of pellet for all type of feed was 60 microns for the whole study period. Temperature, pH and dissolved oxygen were recorded at regular intervals and trout were fed twice (at 9:00 am and 4:00 pm) a day at the ratio of 3% of their body weight and for 6 weeks. Sampling was taken at weekly interval and final sampling was completed on 5th sampling of feeding trial. The effects were assessed by comparing the treated groups of rout to that of control group. The protein supplementation exerted significant (P