Effects of dietary lipid levels on the growth, health, gut microbiota composition and lipid metabolism of juvenile Spinibarbus caldwelli

Abstract

This study aimed to determine the optimal dietary lipid requirement and assess gut microbiota composition in juvenile Spinibarbus caldwelli. Five iso-nitrogenous diets containing graded lipid levels (L1: 2.29 %, L2: 4.54 %, L3: 6.35 %, L4: 8.07 %, L5: 10.04 %) were formulated and fed to S. caldwelli (initial body weight: 2.70 ± 0.01 g) for 56 days. A total of 450 fish were randomly allocated into 15 tanks (3 replicates per group, 30 fish per tank). The results revealed that: 1) Although no significant differences (P > 0.05) were observed in WG, SGR, and SR, these parameters exhibited a declining trend with increasing dietary lipid levels. 2) Muscle crude protein content in the L2 group was significantly higher than that in other groups (P < 0.05), accompanied by distinct variations in lipid and moisture contents. 3) The L2 group displayed markedly elevated concentrations of SFAs and PUFAs in muscle tissue compared to other dietary treatments (P < 0.05). 4) Hepatic and intestinal enzyme activities were significantly enhanced in the L2 and L3 groups (P < 0.05), with optimal performance observed at moderate lipid levels. 5) Intestinal microbiota analysis indicated that the L2 group exhibited significantly higher Shannon, Pielou E, and Simpson indices than other groups (P < 0.05). In conclusion, the L2 group demonstrated superior hepatic antioxidant capacity, enhanced intestinal digestive and lipid metabolic enzyme activities (P < 0.05), and a more diverse and abundant gut microbial community. The analysis results suggested that a 4.54 % dietary lipid level is optimal for juvenile S. caldwelli under the experimental conditions, providing critical insights for formulating species-specific aquafeeds.