Impact of Fish Meal Replacement with Meat Meal on the Growth and Fillet Nutritional Quality of Chum Salmon (Oncorhynchus keta)

Rendered animal by-products such as meat meal are promising fish meal alternatives owing to their high protein content; however, they contain little n-3 long-chain polyunsaturated fatty acids (LC-PUFA), whose effects on fillet fatty acid quality and endogenous LC-PUFA biosynthesis in chum salmon (Oncorhynchus keta) remain unclear. We evaluated the growth, fillet fatty acid composition, and hepatic gene expression of chum salmon fed four diets—a control with 50% fish meal (D1), diets with 35% or 20% fish meal and the remainder replaced by meat meal (D2 and D3), and a D3-like diet with reduced fish oil (D4). Growth performance and feed utilization were unaffected, whereas the hepatosomatic index decreased as meat meal inclusion increased. Muscle n-3 LC-PUFA decreased with fish meal replacement but did not differ between D3 and D4. Serum non-specific immune parameters were unaffected, whereas serum GPx and catalase activities were lowest in fish fed D3. Although srebf1 (sterol regulatory element-binding transcription factor 1) expression increased at the highest replacement level, fads2 (fatty acid desaturase 2) and elovl5 (elongation of very long-chain fatty acids protein 5) were not upregulated, indicating that the reduced n-3 LC-PUFA supply was not compensated by endogenous biosynthesis. Overall, meat meal can replace up to 60% of fish meal without compromising growth, but adequate dietary n-3 LC-PUFA should be maintained to preserve fillet quality.