Akademik Veri Yönetim Sistemi
JOURNAL OF APPLIED PHYCOLOGY, 2026 (SCI-Expanded, Scopus)
High-lipid diets are widely implemented in aquaculture as energy-dense formulations to promote growth and feed efficiency; however, excessive dietary lipid levels may induce metabolic dysregulation, undesirable fat deposition, and impaired flesh quality in fish. Seaweed-derived bioactive compounds have recently gained attention as functional feed additives that can improve lipid metabolism, nutrient utilization, and overall fish health. This study investigated the effects of dietary supplementation with seaweed extracts (Ulva sp. and Solieria chordalis) in high-lipid diets on the growth performance, digestive enzyme activity, and lipid metabolism of rainbow trout (Oncorhynchus mykiss). Over an eight-week feeding trial, fish were randomly assigned to three dietary groups: a control diet with 20% lipid (20L), a high-lipid diet with 23% lipid (23L), and a high-lipid diet supplemented with seaweed extracts (23L + SE). While growth performance parameters, such as final weight and specific growth rate (SGR), were numerically improved in the 23L + SE group, these differences were not significant (P > 0.05), highlighting a potential disconnect between molecular and phenotypic responses. However, the feed conversion ratio (FCR) was optimized with seaweed supplementation, indicating better nutrient assimilation. Feed intake remained comparable across groups, suggesting that the seaweed-supplemented diets were well accepted, although palatability was not directly assessed. The 23L + SE group exhibited significantly higher whole-body lipid content (P < 0.05) while simultaneously showing a reduced mesenteric fat index (MFI), suggesting more efficient lipid mobilization and utilization. Digestive enzyme analysis revealed increased stomach lipase activity in the 23L + SE group, whereas amylase activity was lower, reflecting a metabolic shift favouring lipid utilization. Additionally, the expression of growth-related genes (GH and IGF-I) in muscle tissue was significantly upregulated in the 23L + SE group (P < 0.05), further supporting the role of seaweed extracts in stimulating growth at the molecular level.. Furthermore, dietary seaweed supplementation significantly increased the expression of cpt1b1 and elovl2 (P < 0.05), suggesting enhanced fatty acid oxidation and elongation. Histological examination of liver tissues demonstrated reduced hepatic lipid accumulation in the 23L + SE group, indicating potential benefits for liver health. These findings suggest incorporating seaweed extracts into high-lipid diets improves lipid metabolism, promotes nutrient utilization, and contributes to sustainable aquafeed development. Further research is warranted to explore seaweed-derived functional additives' long-term impacts and economic feasibility in aquaculture.