The course of oxidative processes in the hepatopancreas of age-2 carp after supplementing the feeds with thistle (Siliybum marianum) seeds

Purpose. To study the effect of thistle seeds introduced into the basic diet of carp, the functional state of antioxidant protection (AOP) and the formation of lipid peroxidation products (LPP) in fish hepatopancreas. Methodology. The study has been carried out at the Lviv Research Station of the Institute of Fisheries in duplicate. The first replication was done in 2013, the second one in 2014 at industrial conditions of ponds with similar areas and with the same source of water supply. The object of the study were age-2 Lubin scaled carp. The experiment consisted of four variants and lasted 60 days. The control group of carp received a complete combined feed without additives during the entire growing season, while the experimental groups 1, 2 and 3 received feeds supplemented with 1, 5 and 10% of milled thistle. Thistle was introduced into the feed composition by granulation method. At the end of the experiment, tissue samples of the experimental groups of fish were taken for biochemical analysis. We used 10% tissue homogenates of carp hepatopancreas. We investigated the concentration of diene conjugates using a method based on the reaction of optical density of lipid heptanizopropanol extract. The determination of TBA-active products was carried out spectrophotometrically based on the color reaction with tiobarbitur acid. The activity of superoxide dismutase (SOD) was studied by determining the percentage inhibition of nitroblue tetrazolium reduction reaction in the presence of fenazynmetasulfate. The activity of catalase was analyzed based on the concentration of H2O2. The determination of protein content was performed by Bradford method. The processing of experimental results was performed by variational statistics. Statistically significant difference was assessed using a Student t-test. Findings. As a result of experimental studies in industrial conditions in duplicate, we detected AOP activation and reduction in LPO process intensity in hepatopancreas of all three experimental groups of carp, which received the feed supplemented with 1, 5 and 10% of milled thistle as compared to the control. This trend was more pronounced when using 1 and 5% of this additive in feed composition. In particular, the SOD content significantly increased (P<0.001) in the first replicate and there was a trend for its increase by 13.8–58.2% in the second replicate as well as a reduction in the concentration of the end lipid peroxidation products of LPO (MDA) by 19.9–73.7%. Thus, the use of thistle has a positive effect on antioxidant system on age-2 carp, which in turn will have a positive effect on the functional state of their organism. Originality. The problem of finding the means to mitigate the impact of stress factors on carp, which arise during their rearing, is relevant in today's conditions, since they adversely affect the functional state of fish organism as a whole. An effective way to solve this problem is to use feed supplemented with substances with antioxidant properties. Taking into account the positive results in animal husbandry and some experience in fish farming, the studies of the efficiency of the use of thistle in feeding carp and the determination of norms and methods of its prolonged addition to the diet of carp is an urgent task that has both scientific and practical importance. Practical value. The determination of a positive effect of the use of thistle seeds in carp feeding on the activity of the course of oxidative processes in fish body will allow fish farmers to obtain a cost-effective and environmentally safe mean of levelling the stress factors that have a negative effect on fish during their rearing, at the same time directly influencing on the productivity of fish ponds.