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Abstract. The present research aimed to examine the effect of dietary phytoextracts supplementation on the chemical composition and fatty acid profile in the meat of rainbow trout (Oncorhynchus mykiss W.), cultivated in a recirculation system. The fish were divided into 6 groups: one control (C) and five experimental groups in the food of which phytoextracts of curcumin (EC), paprika (EP), thyme (ET), oregano (EO) and garlic (EG) were added. The inclusion of phytoextracts had no significant effect on growth parameters of fish from EC, EP, ET, EO and EG groups (P>0.05). No statistical differences on water content, protein and lipids were observed in the meat of fish from the control and the experimental groups (P>0.05). Statistically significantly higher value of the dry matter was established in ET group in comparson with C, EC, EP, EO and EG groups (P≤0.001). The values of ash were significantly lower in fish from all experimental groups compared to the control group. The inclusion of phytoextracts did not affect the fatty acid profile of fish from EP, EO and EG groups (P>0.05). Exceptions are EC and ET groups, which had the lowest value of C18:3n-3 α-linolenic compared to those from the control group (P≤0.05, P≤0.001).

Abstract. The aim of the present study was to evaluate the effect of a dietary nutmeg extract supplement on the survival rate, growth performance, feed conversion ratio and economic efficiency of common carp (Cyprinus carpio L.) reared in a recirculation system. Thirty-two carps were allotted into two experimental variants, each of them comprising two replications with 8 fish in a group. The average initial live weight of carps from the control group (CG) and experimental group (EG) was 866.56±113.99g and 868.50±111.18g, respectively (P>0.05). Fish were reared in concrete tanks with efficient volume of 0.8m3, elements of the recirculation system. They were fed pelleted carp feed with 25% crude protein produced by “Top mix” company, with pellet size of 6mm. The feed of fish from the EG was supplemented with 1% powdered nutmeg extract after lubricating the pellets with 5ml sunflower oil per 100g feed. Control carps received the same amount of sunflower oil-lubricated feed. The daily ration of fish from both replications was 1.8% of their live weight. The experiment duration was 45 days. The initial and final live weights were determined by individual weighing. By the end of the experiment, there was a tendency towards statistically insignificant higher average live weight in fish supplemented with 1% nutmeg extract – 986.44±125.91g vs 964.94±92.04g in non-supplemented controls (P>0.05). The survival rate of carps from both control and experimental group replications was 100%. The average individual weight gain of carps from the two EG replications (supplemented with 1% nutmeg extract) was 117.94±31.24g which was higher than that of controls by 16.58% but the differences were not statistically significant (P>0.05). At the end of the trial, the analysis of consumed feed amount showed that feed conversion ratio in the group supplemented with 1% nutmeg extract was 3.05±0.78, i.e. by 23.28% lower than that of control carps (P>0.05). The group that received 1% nutmeg extract exhibited better economic conversion ratio (2.71), by 4.06% lower than that of the non-supplemented group.

Abstract. Water pollution from industrial production and developing agriculture is a serious problem in aquaculture. The aim of this study was to determine the content of heavy metals Zn (zink), Pb(lead), Ni (nickel) and Cd (cadmium) in the muscles of common carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss W.), grown under different technologies. In the current study were investigated common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss), cultivated in net cages, earthen ponds and raceways. The concentration of heavy metals in the muscles of fish was determined by the methods of AAS in the Scientific laboratory of the Faculty of Agriculture. The influence of different production technologies on the bioaccumulation of Zn, Pb, Ni and Cd (in the flesh of common carp and rainbow trout) was found. The Ni content in muscles was 31.25% higher in common carp, cultured at earthen ponds, compared with its content in the flesh of the fish raised in net cages. The concentration of Pd and Ni in rainbow trout, raised in raceways was higher than that determinated for rainbow trout cultivated in net cages, by 25.0% and 7.14%, respectively. The concentration of Cd and Zn of these species, grown in raceways were lower by 33.33% and 2.14%, respectively, compared with their concentration in rainbow trout, cultivated in net cages.