Effect of feeding carp with fat-supplemented pelleted diets on histological appearance of the intestine and hepatopancreas

Sixty two-year-old carps, Cyprinus carpio L. were kept in a closed water circulation system for five months. Fish were assigned to five groups (12 fish per group) and fed ad libitum on Aller Classic pelleted feed for carp: standard or standard pelleted mixture supplemented with 6% oils. The control group (IK) received standard pellets, group IIS+Rz - sunflower oil + rapeseed oil (50% : 50%); group IIIS+L - sunflower oil + linseed oil (80% : 20%); group IVR - fish oil; and group VSK - pork scratchings at the level of 6%. At the end of the experiment, 10 carps from each group were slaughtered and their body length and weight were measured to calculate mean body weight gains and mean individual gains. Fragments of intestine and hepatopancreas were histologically and morphometrically analyzed. The mean weight gains of fish at the end of the experiment, which were the highest for diet IIIS+L, and the lowest for VSK and IK diets, were fully confirmed by histological analysis, which showed that the lowest gains in biomass and mean individual weight were due to digestive disturbances associated mainly with lipid metabolism. These disturbances did not occur in groups IIS+Rz, IIIS+L and IVR.