Increasing the efficiency of commercial rearing of the common carp (Cyprinus carpio Linnaeus, 1758) with the use of milk thistle (Silybum marianum (L.) Gaertn) in the ration composition

Purpose. The purpose of the study was to investigate the feasibility and efficiency of the use of milk thistle in the process of commercial cultivation of the common carp in terms of productive and economic indicators. Methodology. The study was conducted in two experimental and control ponds, which were stocked with carp yearlings at a density of 1000 ind./ha. The carp of the first experimental group during the growing season were additionally fed with a diet containing 1% of milk thistle, while the second experimental group – 5%. During the work, optimal conditions of carp cultivation were maintained. The dissolved oxygen, temperature hydro-chemical and hydro-biological regimes of the aquatic environment were monitored and the efficiency of cultivation at the end of the growing season was analyzed by conventional methods. Findings. In general, the conditions of fish cultivation in the experimental and control ponds were satisfactory. No relationship was observed between the hydro-chemical regime of the experimental ponds and the diet composition. The average seasonal biomass of feed organisms of zooplankton and zoobenthos during the growing season were 4.22 – 5.11 g/m3 and 1.37 – 1.62 g/m2 respectively, and equally contributed to the process of carp cultivation both in experimental variants and in the control. It was found that the average weight of carps fed with diets contained 1% and 5% of ground milk thistle was higher by 7.3% and 5.6%, respectively, fish productivity – by 9.8% and 7.2%. At the same time feed costs per kilogram of production decreased by 5.9% and 8.8% compared to the control. The cost of additionally obtained fishery products when supplementing the diet with 1% of milk thistle amounted to 11849 UAH/ha, 5% – 10217 UAH/ha. The attributable profit, including costs of feed and fish seeds, when using 1% of milk thistle was 13.1% higher than in the control, 5% – 0.7% higher in the control group. Scientific novelty. According to a wide range of biologically active properties of milk thistle, the effect of this additive on the productive and economic indicators in the process of age-2 carp has been studied for the first time. The implementation of this practice provided an opportunity to increase fish productivity by feeding fish with artificial feeds of improved composition. Practical value. Reducing the cost and obtaining additional weight gains during the cultivation of aquaculture products can be ensured by improving the quality characteristics of fish feeds, and, accordingly, the physiological parameters of age-2 carp organism.