Effect of supplemental feeds on liver and intestine of common carp (Cyprinus carpio) in semi-intensive rearing system: histological implications

In order to determine effects of different types of supplementary feed on the histology of liver and intestine of carp reared in a semi-intensive system, a six-month field experiment was carried out. Carp yearlings were fed different supplemental feeds: cereals (CF), pelleted (PF) and extruded (EF) compound feeds. Hepatocytes histomorphometry revealed larger nuclear profile area of EF-fed fish compared to other two groups, while cytoplasmic profile area of the hepatocytes decreased in following sequence: CF > EF > PF. Lower nucleus/cytoplasm ratio was found in CF-fed fish compared to EF- and PF-fed fish. Striking, season dependant finding, was that regardless of the type of supplementary feed the number of lipid droplets in hepatocytes was highest in July and August, lipid depletion occurred in September and October, while glycogen was present in hepatocytes throughout the study. No size difference between groups was observed for enterocytes height, absorptive surface height and number of goblet cells in tunica mucosa, but a strong relationship between length of intestinal folds and fish weight was found. Histological analysis revealed a difference among three types of supplemental feed used in this field study: extruded or steam-pelleted feed induced better nutritional status of common carp in comparison to cereals. At the same time, histomorphometry indicated some differences between EF-and PF-fed fish