Replacement of fish oil with Tenebrio molitor larvae oil in diets for juvenile silver catfish (Rhamdia quelen)

Abstract

In this study, we aimed to evaluate the effects of Tenebrio molitor larvae oil (TO) as a replacement for fish oil (FO) on growth performance, body composition, muscle fatty acid profile, blood biochemical parameters, and digestive and antioxidant enzymatic activities of juvenile silver catfish (Rhamdia quelen). Three isoproteic (45% crude protein) and isolipidic (10% lipid) diets were tested: a control with FO, TO50 (50% replacement with TO), and TO100 (100% replacement with TO). Fish (initial weight: 2.26 ± 0.01 g) were fed the different diets to satiation for 50 days, and thereafter, blood, liver, muscle, and digestive tract samples were collected for analysis. Our findings show that total replacement with TO did not affect the growth performance, survival, physiological parameters, digestive enzymatic activity, or hepatic and plasma metabolism. Body composition (ash, protein, and fat) and protein retention showed no significant differences among the diets, although lipid retention was higher in fish fed the TO100 diet. Saturated and monounsaturated fatty acid levels in the muscle were unaffected by diet. In contrast, diets significantly influenced the levels of polyunsaturated fatty acids (PUFAs), especially omega-3 and -6 levels. The FO diet yielded the highest PUFA (22.35%) and omega-3 content (12.55%), with docosahexaenoic acid (DHA, C22:6n-3) reaching 7.63%. The TO100 diet had the highest omega-6 content (12.46%), driven by linoleic acid (C18:2n-6, 9.46%). Consequently, the omega-3/omega-6 ratio varied from 1.30 in FO to 0.40 in TO100. In conclusion, TO can completely replace FO in the diet of R. quelen at the juvenile stage evaluated in this study without negatively affecting growth performance and biochemical parameters.