Introduction: Introduction: The Siberian sturgeon (Acipenser baerii) is one of the most valuable sturgeon species in aquaculture, prized for its high-quality meat and caviar, broad environmental adaptability, and tolerance to low temperatures. With growing global demand for fishery products and declining natural stocks, artificial propagation and intensive farming of this species have become increasingly important. A major challenge in intensive sturgeon culture is meeting precise nutritional requirements, particularly regarding essential micronutrients such as vitamins and immunostimulants. Niacin (vitamin B3), as a precursor to the coenzymes NAD and NADP, plays a critical role in energy metabolism, cellular respiration, glycogen synthesis, and lipid metabolism. Barley malt extract, obtained through germination and extraction of barley grains, is rich in B-complex vitamins (B1, B2, B3, B6, B12), fermentable carbohydrates (maltose, dextrin), phenolic compounds with antioxidant properties, and prebiotic beta-glucans. These components can act as growth promoters, digestive enhancers, and immune system stimulants. Despite numerous studies on other fish species, no research has yet investigated the synergistic effects of malt extract and niacin on hematological, immune, and stress indices in Siberian sturgeon. Therefore, this study aimed to compare the effects of different dietary levels of malt extract and vitamin B3, alone and in combination, on hematological, biochemical, and stress parameters in juvenile Siberian sturgeon.
Materials and methods: In this experimental study, 300 juvenile Siberian sturgeon with an average initial weight of 50 ± 0.16 g were obtained from the Shahid Beheshti Sturgeon Propagation and Rearing Center in Rasht and transferred to the Dr. Keyvan Research Center. After 48 hours of fasting and one week of acclimation, fish were randomly distributed into 8 treatments with 3 replicates each (10 fish per tank), including: control (basal diet), 1% and 1.5% malt extract, 20 and 30 mg/kg niacin, combined diets of 1% malt extract+20 mg/kg niacin and 1.5% malt extract+30 mg/kg niacin, and a 96% ethanol treatment (solvent control). The rearing period lasted 8 weeks in 500-L tanks. Vitamin B3 powder was dissolved in 96% ethyl alcohol and distilled water and sprayed onto the basal diet. Feeding was performed daily at 2–3% of live biomass in three meals. At the end of the trial, after anesthesia with clove powder, blood samples were collected from the caudal vein. RBC and WBC counts were performed using a Neubauer hemocytometer; hemoglobin by cyanmethemoglobin method; hematocrit by microhematocrit method; and differential leukocyte counts by Giemsa staining. Biochemical parameters (glucose, cortisol, iron, cholesterol, triglycerides, sodium, potassium, and calcium) were measured using an autoanalyzer. Data were analyzed using ANOVA and Tukey's test at p < 0.05.
Results and Discussion: The results showed that experimental treatments had significant effects on most hematological and biochemical parameters (p < 0.05). The 30 mg/kg niacin treatment (B30) exhibited the highest red blood cell count (850,500 ± 10,606 vs. 774,500 ± 707 in control), white blood cell count (7,050 ± 494.97), hemoglobin (5.95 ± 0.09 g/dL), and hematocrit (30.80 ± 0.42%). The lowest mean corpuscular hemoglobin concentration (MCHC) (30.19 ± 0.28%) and mean corpuscular hemoglobin (MCH) (69.90 ± 0.28 pg) were observed in the B30 group, while the highest values for these two indices were recorded in the 96% ethanol group (Al96) at 19.80 ± 0.28% and 72.15 ± 0.92 pg, respectively. The highest mean corpuscular volume (MCV) (364 fL) was found in groups F, M1.5, and Al96, whereas the lowest MCV (361 fL) was seen in groups M1, B20, B30, M1+B2, and M2+B3. The lowest hematocrit (28.20 ± 0.0%) was recorded in groups F and M2+B3, and the highest (38.80 ± 0.43%) in group B30. The highest neutrophil percentage (17 ± 1.41%) was observed in group B30, and the lowest (9.50 ± 2.12%) in group F. The highest monocyte percentage (5.50 ± 0.071%) was recorded in the M1.5 treatment, and the highest lymphocyte percentage (87 ± 1.41%) was observed in Treatment 1. The highest glucose (65 ± 0.1 mg/dL) and cortisol (2.1 ± 0.12 mg/dL) levels were recorded in the 1.5% malt extract treatment (M1.5). The highest serum iron levels were observed in the M1.5 treatment (42.1 ± 0.8 mg/dL) and the M2+B3 combination (42.03 ± 0.7 mg/dL), which were higher than the control (37.25 ± 1.63 mg/dL). The highest cholesterol levels were found in the Al96 group (366.2 ± 0.2 mg/dL) and the M2+B3 group (365.0 ± 0.43 mg/dL), while the lowest cholesterol levels were recorded in the M1 group (351 ± 1.27 mg/dL) and the M1.5 group (365.0 ± 0.23 mg/dL). The highest triglyceride level was observed in the Al96 group (371 ± 0.23 mg/dL), and the lowest levels were recorded in the M1 group (313 ± 0.23 mg/dL) and the M1.5 group (315 ± 0.89 mg/dL). Sodium, potassium, and calcium showed no significant differences among treatments (p > 0.05).
Conclusion: The diet containing 1.5% malt extract and 30 mg/kg niacin improved hematological indices, increased serum iron, regulated glucose and cortisol within physiological ranges, and reduced adverse lipid effects without any negative impact on electrolyte balance. Therefore, it can be recommended as an effective nutritional strategy for promoting health and reducing stress in Siberian sturgeon aquaculture. Ethanol 96% is not suitable as a carrier. |
