Thyroxine and triiodothyronine concentrations in juvenile <i>Oncorhynchus mykiss</i> when supplementing the diet with organomineral chelate complexes

The paper presents data on the concentration of thyroxine and triiodothyronine in juvenile golden trout when enriching their diet with organomineral chelate complexes. The objective of the work was to evaluate the effect of enriching fish diet with iodine-containing organomineral complexes on the concentration of thyroid hormones (total thyroxine and total triiodothyronine). The study was conducted at a fish farm in the Leningrad Region. The fish in the experimental groups (n=10) were given a biologically active supplement with their feed (at a concentration of 0.5 g/kg, based on the feed weight) for 30 days. The data were compared with the control group (n=10) that received standard feed. The amount of thyroid hormones in the studied fish was determined using enzyme-linked immunosorbent assay (ELISA). It was found that the use of the organomineral chelate complex in the studied dosage contributed to an increase in the concentration of thyroid hormones. It is suggested that enrichment of feed with organomineral complex can be recommended for prevention of hypothyroidism in fish. Reducing the probability of hypothyroidism in fish farms will contribute to decreasing mortality and frequency of detection of developmental anomalies.