Changes in the hematological profile, hepatic biomarkers, antioxidant capacity, and digestive functions of Sterlet sturgeon (Acipenser ruthenus) fed diet supplemented with dietary nucleotides

This study investigated the effects of dietary nucleotides (NTs) on hematological indices, hepatic biomarkers, antioxidant capacity, digestive functions, and intestinal histomorphology of Sterlet sturgeon ( Acipenser ruthenus ). Over 10 weeks, five diets with varying NT levels (0 g/kg, 1.5 g/kg, 2.5 g/kg, 3.5 g/kg, and 5.0 g/kg) were fed to triplicate groups of fish (initial weight: 95.33 ± 1.23 g) in a flow-through system. Results indicated no significant differences in RBC, Hb, MCHC, HCT, and EOS among groups (p > 0.05). The highest WBC count was seen in fish on the 3.5 g/kg NT diet compared to the control (p < 0.05). Serum hepatic enzyme levels generally decreased with higher NT supplementation, although ALT increased significantly at the 5.0 g/kg level (p < 0.05). Antioxidant capacity improved in fish fed 0.25 and 0.35 g/kg NTs (p < 0.05), while serum MDA decreased with up to 3.5 g/kg NTs but increased at 5.0 g/kg (p < 0.05). Protease and amylase activity peaked in fish receiving 3.5 g/kg NTs (p < 0.05), with lipase activity highest at 2.5 g/kg NTs (p < 0.05). Intestinal histology revealed that fish on the 3.5 g/kg NT diet exhibited the greatest villi height and width, along with more goblet cells (p < 0.05). In conclusion, the present study indicated the optimum dietary level of NTs for positive effects on physiometabolic responses and intestine functions of the Sterlet sturgeon lies in the range of 2.2–3.6 g/kg.