Abstract
The aim of the study was to identify the impact of feeding juvenile tench commercial feed supplemented with fish oil, linseed oil, arachide oil, and rapeseed oil on the hematology, cytology, and histology indexes of the liver. The fish were reared in a recirculating system and fed feed containing 470 g protein kg-1 feed and 120 g fat kg-1 feed (1000 g of base feed containing 70 g fat kg-1 feed was supplemented with 50 g of additional fat, i.e., fish oil (FO) or vegetable oils - linseed oil (LO), arachide oil (AO), or rapeseed oil (RO)). Statistically significant inter-group differences were noted for hematocrit (Ht), hemoglobin (Hb), red blood cell (RBC) counts, and other red blood cell indexes, including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) (P < 0.05). The lowest Ht and Hb values were noted in fish fed feed supplemented with fish oil (group FO), while the highest was noted in the tench from group AO. These differences were mainly caused by the occurrence of smaller erythrocytes in the peripheral blood of the fish from the FO group. No pathological changes were observed in the blood cells, which was in contrast to the parenchymal cells of the liver. Congestion, lipid vacuolization in hepatocytes, regressive changes in cytoplasm density, nuclear chromatin, and nucleus disintegration were observed in all fish. These changes were more pronounced in groups LO and AO. The fish from these groups were characterized by smaller hepatocytes and significantly higher nucleocytoplasmic ratios (P < 0.05).