Dietary Protein Requirement of Juvenile Ide, Leuciscus idus in Relation to Growth Performance, Whole-body Composition and Plasma Parameters

Abstract

A 60-day feeding trial was conducted to determine the dietary protein requirements of juvenile ide, Leuciscus idus. Six iso-energetic experimental diets were formulated to contain graded protein levels ranging from 26.5% to 50.9% of dry diet. At the end of feeding trial, final weight (FW), weight gain (WG), and specific growth rate (SGR) increased significantly with increasing dietary protein levels up to 36.4%, and thereafter decreased with further increase of dietary protein levels (P<0.05). Feed conversion ratio (FCR) showed a converse trend (P<0.05). Hepatosomatic index and viscerosomatic index were negatively related to dietary protein levels (P<0.05). Increase of dietary protein levels significantly improved whole-body protein content and decreased lipid content (P<0.05). White blood cell counts, red blood cell, hemoglobin, and hematocrit, were independent of dietary protein levels (P>0.05). Plasma protein content was not significantly affected by dietary protein levels (P>0.05), while plasma triglyceride and glucose concentrations were decreased significantly with increasing dietary protein levels (P<0.05). The highest aspartic transaminase activity was observed in fish fed diet 26.5% protein, and the lowest value was observed in 36.4% protein group (P<0.05). Based on SGR and FCR, the dietary protein requirement of juvenile ide was determined to be 36.9%-37.7% of dry diet. Dietary methionine and lysine levels for optimal growth was calculated to be 0.83% and 2.25% of dry diet, respectively.