Assessment of nutritional contents and microbial community of three populations of cultured Beluga sturgeon (Huso huso) broodfish

Beluga sturgeon (Huso huso) is a valuable fish all over the world to produce caviar and meat. It is a good candidate for aquaculture due to its acceptance of formulated diets and high resistance to stressors from increased density during farming. This study evaluated three groups of sexually unknown farm-raised Beluga sturgeon populations that differed by age to understand differences in growth rate, nutrient utilization and microbial community by gut sections. Weight, length, and liver samples were collected to determine growth parameters. Proximate compositional and histopathological analyses were conducted. Luminal samples from the stomach and midgut and hindgut sections were collected for 16S rRNA gene characterization. The results showed that fish weight differed by age group (p < 0.05). The condition factor ranged from 0.61 to 0.78 for all the age groups. Fillet fatty acid compositions showed that erucic acid (monounsaturated) was significantly different (p < 0.005) between the three age groups, but not for other fatty acids and amino acids. The gastrointestinal section was a stronger factor than age modulating the microbial compositions in beluga (p < 0.05), and their compositions and diversity varied between stomach, midgut, and hindgut sections. The abundance of Lactococcus and Lactobacillus genera increased in the hindgut section of the gastrointestinal tract and differed by age group. Proteobacteria correlated positively and significantly with the essential amino acids (p < 0.05). The genus Haloimpatients from phylum Firmicutes showed a positive correlation with phenylalanine and threonine in the Beluga stomach (p < 0.05). A similar trend was found between Staphylococcus and histidine in the hindgut. More studies should be directed to address the functionality of the microbiota highlighted in the gut sections in this study and their involvement in the metabolism of essential amino acids to improve the conditions and optimal nutrient requirements of farm-raised Beluga sturgeon.