Activity of Energy and Carbohydrate Metabolism Enzymes in Rainbow Trout Fingerlings (Oncorhynchus mykiss Walb.) When Fed Two Types of Commercial Feed

We studied the activity of energy and carbohydrate metabolism enzymes (cytochrome c oxidase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, 1-glycerophosphate dehydrogenase, pyruvate kinase, and aldolase) in the muscles and liver of rainbow trout of three size groups with ages of five, ten, and 12 months under the influence of two types of commercial feeds with different composition. The levels of activity of the enzymes G6PDH, 1-GPDH, and aldolase in the liver were significantly higher in fish from the “feed no. 2” group. The identified differences in the activity of enzymes in the liver of fish suggest that feed no. 2 to a greater extent (compared to feed no. 1) promotes the use of carbohydrates in lipid biosynthesis. Differences in the activity of the enzymes COX, LDH, aldolase, G6PDH, and 1-GPDH in the liver and muscles of fish depending on the month of sampling and size group are most likely associated with changes in the metabolism of fish as their weight increases towards generative metabolism.