Ayoub Yousefi Jourdehi

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 levels of NTs (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 the fish (initial weight: 95.33 ± 1.23 g) in a flow-through system. The results indicated that final weight and relative growth rate reached the highest values in fish fed with the 5.0 g/kg NTs supplemented diet (p < 0.05). The fish fed NTs-supplemented diets also had lower feed conversion ratios than those fed the basal diet (p < 0.05). While total leukocytes were increased by increasing the dietary NTs supplementation to the highest value in the fish fed with 3.5 g/kg NTs, no significant differences were obtained in RBC, Hb, MCHC, HCT, and eosinophil values among the experimental groups (p > 0.05). The highest WBC count was seen in the fish fed with 3.5 g/kg NTs compared to the control group (p < 0.05). The serum hepatic enzyme levels generally decreased with higher NTs supplementation, although alanine transaminase significantly increased at the 5.0 g/kg level (p < 0.05). The antioxidant capacity was improved in the fish fed with NTs at 0.25 and 0.35 g/kg (p < 0.05), while the serum malondialdehyde level was decreased up to 3.5 g/kg NTs but it was increased at 5.0 g/kg (p < 0.05). The protease and amylase activities peaked in the fish receiving 3.5 g/kg NTs (p < 0.05), with the highest lipase activity obtained in 2.5 g/kg NTs (p < 0.05). The intestinal histology revealed that the fish fed with NTs at 3.5 g/kg exhibited the greatest villus height and width, along with more goblet cells (p < 0.05). Based on the second-order polynomial regression analysis, the optimum dietary levels 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.

Six different feeding regimes (FR) were tested from 7 to 38 days post hatching (dph). Five thousand four hundred larvae (7 dph, 0.048 g) were randomly stocked in 18 fiberglass tanks contained 100 L fresh water (300 larvae per each tank). In larvae fed with FR-B, includes Artemia nauplii (AN) + Artemia biomass (AB) + microdiet (MD), the body weight (BW) at the end of trail (38 dph) similar the FR-D (AN + CHL + AB + MD), and E (AN + CHL + AB), was at high level. Survival rate was higher in larvae fed FR-A includes AN + chironomid larvae (CHL) + MD, but had a lower BW ( ). Moderate BW and survival rate were detected in larvae fed FR-C (AN + DP + MD). Larvae fed only MD (FR-F), had the lowest survival and the highest BW ( ). Different FR had a significant effect on crude protein (CP), crude fat (CF), ash, and dry weight ( ). The larvae fed FR-C and D had the highest CP ( ). The highest CF and ash in larvae were detected in FR-F and C, respectively ( ). Larvae from FR-A and B had higher levels of n−3 long chain polyunsaturated fatty acids in comparison with others FR ( ). The use of AB and CHL can increased the weight and survival rate of larvae, respectively. At the end of trail, the activity of pepsin, trypsin, lipase and α-amylase enzyme levels were lower in FR-B and F than others FR. Totally, by using a combination of AN + CHL + AB + MD had better results than others and ordered to H. huso larvae feeding. Using MD alone, can cause lesser development of the digestive system and little attractiveness, therefore it can cause starvation, and the empty digestive tract of larvae.

Oocyte maturation in fish is a hormonally regulated process. In the light of long-term oocyte maturation in beluga, the aim of this research was to study the estrogenic effects of different concentrations of soy dietary genistein (GE) and equol (EQ) on the growth performance and ovary development in farmed female Huso huso. Fish were fed with concentrations 0 (control), 0.2, 0.4, 0.8 and 1.6 g of EQ and GE per kg of isoproteic (CP 45 %) and isoenergetic (19.5 MJ/kg) diets during a year. Blood samples and ovary biopsies were collected from each fish seasonally. The main results of the present experimentation are that growth performance was not affected significantly both in GE and EQ (P > 0.05). EQ at concentration 0.4 g/kg had more estrogenic effects than other concentrations of EQ and GE in beluga so that 64 % of fish were matured sexually. Some reproductive indices such as oocyte diameter, testosterone (T) and 17β-estradiol (E₂) increased significantly at EQ 0.4 g/kg at the end of experiment (P < 0.05), while 17α-hydroxy progesterone level (17α-OHP) showed no significant changes at all concentrations. Biochemical indices such as calcium, phosphorous and cholesterol increased at GE concentrations, but decreased at EQ concentrations similarly at the end of experiment. There was a negative relationship between plasma phosphorous and alkaline phosphatase enzyme levels. Based on results, EQ at concentration 0.4 g/kg improved oocyte development more than the other concentrations of GE and EQ, and therefore, it can be used as an additive to diets for inducing ovary development in this species.