Effects of different feeds on growth performance parameters, histology of liver, distal intestine, and erythrocytes morphology of common carp (Cyprinus carpio L.)

In the last 60 years, pond farming of common carp (Cyprinus carpio) in Europe has gradually intensified, which has increased the stocking density and amount of supplementary feed, resulting in higher yields. Additionally, compound feed has been introduced to semi-intensive farming to increase the growth of farmed fish. Feed quality affects growth directly through conversion efficiency and indirectly by influencing fish physiology. In the present study, juvenile common carp were grown in net cages in a fishpond for 80 days and fed the same amount of different supplementary feed: wheat, pelleted, or extruded feeds or fish relied only on the available natural food (control group). Growth, microanatomy of the liver and distal intestine, and morphology of erythrocytes were evaluated. Compound feed had beneficial effects on the growth and histological parameters compared to the control group and fish fed wheat. This included higher surface areas of erythrocytes and hepatocytes` nuclei, longer intestinal folds, and thicker tunica muscularis in the distal intestine. The study showed that increased growth and use of compound feeds did not cause any physiological trade-offs that would be depicted in quantitative histomorphometry, and there was an absence of histopathological changes.