Effects of different co-feeding strategies on growth, body chemical composition, digestive enzymes, and expression of gh and igf-1 genes in Beluga sturgeon (Huso huso) larvae

This study evaluates the effect of different feeding regimes on the growth performance, body composition, digestive enzyme activity, and the expression of growth-related genes of Beluga sturgeon (Huso huso) larvae. A total of 1200 larvae (mean weight 0.44 ± 0.01 g) were divided into four treatments and fed either with formulated diet only (FD) or a combination of formulated diet and live food including chironomids (CHFD), Artemia (ABFD), or both (MFD) for 42 days. The results indicated that, despite the higher weight gain (WG) and protein content of the FD group, it had the lowest survival rate (SR) as compared to other treatments (P < 0.05). The CHFD treatment had the highest SR, condition factor, and higher WG than ABFD and MFD groups (P < 0.05). The protein and lipid content increased significantly in FD and ABFD groups, respectively (P < 0.05). The total fatty acids, MUFA, EPA/ARA, and n-3/n-6 ratios were also increased in all treatments at the end of the trial (P < 0.05). DHA levels were also higher in CHFD and FD groups with no significant difference in PUFA between the groups (P > 0.05). The results of digestive enzymes showed higher trypsin activity in CHFD and ABFD groups, which may suggest the adaptation of the fish to the formulated diet. Gene expression analysis revealed that gh levels were higher in FD and ABFD groups while igf1 was up regulated in CHFD group (P < 0.05). These findings suggest that using chironomids during the transition to a formulated diet in Beluga sturgeon larvae can significantly enhanced growth performance and survival, body composition, enzyme activity, and the expression of growth-related genes.