Replacement of fish oil by camelina and black soldier fly larvae oils in diets for juvenile Totoaba macdonaldi and their effect on growth, fatty acid profile, and gene expression of pancreatic lipases

Abstract

The present study evaluated the use of camelina (CO) and black soldier fly larvae (BSFLO) oils as replacements of fish oil (FO) in diets for juvenile Totoaba macdonaldi, and their effect on growth, proximate composition, fatty acid (FA) profile of tissues, and gene expression of bile salt-dependent (BSDL) and colipase-dependent (CDPL) pancreatic lipases. Four isoproteic (51% crude protein) and isolipidic (14% crude fat) diets were formulated based on a 2 × 2 factorial design with two lipid sources, CO and BSFLO, each tested at two levels of replacement of FO, 30 and 60%. A control diet containing 100% FO was included as a reference. Fish with an overall initial weight (mean ± standard deviation, S.D.) of 3.0 ± 0.1 g were stocked at a density of 100 fish m−3. Each diet was randomly assigned to five replicate tanks, and four tanks for the control. After 7 weeks, weight gain (WG, P = 0.0302) and thermal growth coefficient (TGC, P = 0.0408) were significantly reduced in fish fed the 60% FO replacement level in comparison to the 30% level; fish fed diets containing 30% BSFLO were the only ones achieving statistically similar WG (59.40 g) and TGC (0.175) as fish fed the control diet (WG of 60.68 g and TGC of 0.177). Muscle and liver tissues of fish reflected the FA profiles of experimental diets; fish fed BSFLO showed greater content of lauric acid (12:0) in muscle (0.14–0.17 mg g−1), while alpha-linolenic acid (18:3n-3) was higher in those fed CO (0.25–0.51 mg g−1). Docosahexaenoic acid (22:6n-3) content was statistically similar in fillets from all different treatments, demonstrating selective retention of this biologically important FA, but eicosapentaenoic acid (20:5n-3) decreased as the level of FO replacement by CO or BSFLO in diets increased. The presence of BSDL and CDPL in the digestive tract of T. macdonaldi was confirmed for the first time, but regulation of their gene expression was not significantly affected at a transcriptional level by the progressive replacement of FO by CO or BSFLO under these experimental conditions. These findings suggest that 30% of FO can be successfully replaced by BSFLO in diets for juvenile T. macdonaldi, and a 100 g fillet from fish fed this diet would provide 284 mg of DHA + EPA, satisfying the daily intake recommended for adult consumers.