- Zhelyazkov*, S. Stoyanova, I. Sirakov, K. Velichkova, Y. Staykov
Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University,
6000 Stara Zagora, Bulgaria
(Manuscript received 21 December 2017; accepted for publication 16 February 2018)
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.