Growth, feed utilization, and quantitative histological assessment of the distal intestine and liver of common carp (Cyprinus carpio L.) fed formulated diets containing grains of different soybean cultivars

Abstract

A 12-week feeding trial with common carp (Cyprinus carpio) was conducted to test the hypothesis that compound diets formulated on the basis of different soybean cultivars will have effects on growth parameters, feed utilization, and digestive system histology. Soybean grains were from the following cultivars: Alisa (SB-A), Balkan (SB-B), and Galeb (SB-G). The fourth tested diet contained grains from a mixture of different SB cultivars (SB-M). The results confirmed the tested hypothesis, as the fish from the group SB-A showed higher average weight gain, specific growth rates, and feed efficiency, as well as lower feed intake and feed conversion ratio, compared to the groups SB-B and SB-M. On the other hand, diets were expected to cause inflammation in the distal intestine of the fish, but this did not occur. Histological examination of the intestine and liver, performed at the end of weeks 1, 3, 6 and 12, showed no pathological changes. Most of the differences between the groups were found at the end of the trial. The group SB-A had a higher surface area of different intestinal layers compared to the groups SB-B and SB-G. The surface area of the goblet cells was greatest at most of the time points in SB-M. In the liver, the evaluation of the surface area of hepatocytes and their nuclei showed no significant differences between the groups. The differences in final body mass, which showed a maximum value of 18% between the groups, could be of significant importance for culture of this freshwater species.