Transcriptomic and Histological Responses to Fish Meal Substitution with Soy Protein Concentrate in Formulated Feed in Totoaba (Totoaba macdonaldi) Juveniles.

In the present study, we report the effects of soy protein concentrate (SPC) on growth parameters, liver morphology and hepatic transcriptomic response on totoaba (Totoaba macdonaldi) (153 ± 0.84 g). Two experimental isoenergetic diets (IDs), each containing 44% protein and 11% lipids, were formulated by replacing 30% (SPC30) and 60% (SPC60) of fish meal with SPC and compared to a commercial diet (CD) containing fishmeal. Treatments were performed in triplicate (n = 12 per replicate) over a period of 90 days. Fish fed the CD or SPC30 diets showed no significant differences in final weight (fW: 618.4 ± 20.13 and 624.4 ± 16.97 respectively). Conversely, fish fed the SPC60 diet exhibited the lowest growth performance (fW: 260.10 ± 57.65 g, weight gained: 68.84 ± 0.94 g and specific growth rate: 0.36 ± 0.22%). Liver from totoaba fed the CD showed a typical, uniform hepatic organization. In contrast, livers from SPC30 and SPC60 groups displayed lipid vacuole infiltration in hepatocytes and central displacement of the nuclei. Functional gene enrichment analysis of transcripts revealed that biological processes (BP), such as protein catabolism (ctra, ctrb, ela1, cbpb1, cbpa1), stress responses (bfar, dab, casp8, pawr), anatomical structure development (stml2, lrig2, hgf, ret), bile acid biosynthesis (s27a2, ntcp7, nr1h4) and lipid transport (s27a2, lipe4, fabpi), were the molecular mechanisms most affected by SPC supplementation. Collectively, these BPs suggest negative effects of SPC60 supplementation in totoaba.