Siberian sturgeon is an important species in aquaculture due to its use for caviar production and high quality of meat. One of the most important factors that indicates the health of juveniles is gastrointestinal tract functionality. Scientific literature reported numerous data on the impact of fish nutrition on gut health and microbiota diversity. The following experiment was designed to, among others, evaluate the impact of partial fishmeal replacement with low-fat Hermetia illucens (BSF – black soldier fly) meal in Siberian sturgeon diets on gastrointestinal tract microbiota composition and histomophometric parameters.
The amino acid composition was analyzed to calculate the conversion factor (Cf) for BSF. Nine diets were prepared: CON – control group, H75 – group with 7.5% inclusion of BSF meal, H150 – group with 15% inclusion of BSF meal, H225 – group with 22.5% inclusion of BSF meal, H300 – group with 30% inclusion of BSF meal, HK75 – group with 7.5% inclusion of BSF meal based on calculated Cf, HK150 – group with 15% inclusion of BSF meal based on calculated Cf, HK225 – group with 22.5% inclusion of BSF meal based on calculated Cf, and HK300 – group with 30% inclusion of BSF meal based on calculated Cf. A total of 100 fish were used in each experimental group, 20 fish per tank and five replicates per group. The experiment was conducted for 60 days. Fry were maintained in a recirculating RAS system. In the last day of experiment four fish from each tank were euthanized and dissected to collect biological samples – gastrointestinal tract digesta and proximal part of intestine. Gastrointestinal tract digesta were analyzed by fluorescence in situ hybridization.
In the case of histomorphometric parameters, for the intestinal villi height , the highest values in the experimental groups were observed in fish from groups H75, H150, H300, HK225 and HK300, although these results did not differ statistically significantly from the control group, but only between other experimental groups (P< 0.001). However, higher muscle layer was observed only in fish from the HK75 group (P<0.001).
In the case of the gastrointestinal microbiota composition , an increased total number of bacteria was observed in the H150 and HK300 groups compared to the control group (P=0.010). The lowest values of pathogenic Aeromonas spp. were observed in the case of fish from groups H75, HK75 and HK150. At the same time, fish from the control group had the lowest value of Enterobacteriaceae (P=0.003). A reduced content of Lactobacillus spp. bacteria was observed in individuals from the H75 group (P=0.039). Other bacteria groups did not show nutritional effect.
This study was carried out as part of the project entitled: Innovative application of Hermetia illucens protein and fat in Acipenseridae fish aquaculture (LIDER/2/0018/L-12/20/NCBR/2021) financed by The National Centre for Research and Development