1. G. Zhelyazkov*

Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6014 Stara Zagora, Bulgaria

DOI: 10.15547/ast.2018.03.039

(Manuscript received 30 May 2018; accepted for publication 15 August 2018)

Abstract. The aim of the study was to determine the effect of a monosodium glutamate dietary supplementation on the survival rate, growth performance, feed conversion ratio and economic efficiency of common carp (Cyprinus carpio L.), cultivated in net cages. Two hundred carps were allotted into two experimental variants, each of them comprising two replications (Control groups – CG and CG₁; Experimental groups – EG and EG₁), with 50 fish in a group. The average initial live weight of fish from the control and experimental groups was 1141.62±79.62g and 1129.54±71.47g, respectively (P>0.05). The carps were cultivated in net cages with a size 3.0/3.0/2.0m. The fish were fed with extruded feed Aqua garant VITAL, a product of Garant-Tiernahrung Gesellschaft m.b.H. – Austria, with 6mm size of pellets. Monosodium glutamate in amount of 1% was added to the feed of carps from the experimental groups. The fish from the control groups received no monosodium glutamate supplementation of the diet. The feed given to the fish was 2% of the total biomass. The trial period was 60 days, control catch at 30^th day were done in order to study the influence of the monosodium glutamate supplementation on the weight gain and feed conversion ratio of the common carp, cultivated in net cages. The initial (1^st day), control (30^th day) and final (60^th day) live weights (g) were determined by individual weighing. The final live weight of the fish from both replications of the experimental and the control groups was as follows: 1699.36±78.43g and 1597.27±74.66g, the differences were significant (P<0.001). The survival rate of carps from both control and experimental group replications was 100%. The average individual weight gain of fish from the two replications (supplemented with 1% monosodium glutamate) was 569.82±3.75g which was higher than that of controls by 20.04%, the differences were significant (P<0.001). At the end of the trial, the analysis of consumed feed amount showed that feed conversion ratio in the group supplemented with 1% monosodium glutamate was 1.76±0.12, i.e. by 25.57% lower than that of control carps (P<0.001). The economic efficiency in the experimental groups exhibited better economic conversion ratio (0.936), by 22.65% lower than that of the non-supplemented groups.