Fish Oil Replacement with Virgin Coconut and Corn Oil: Impact on Growth Performance, Lipogenic and Digestive Enzyme Activity, and mRNA Expression of Genes Involved in Lipid Metabolism of Nile tilapia (Oreochromis niloticus)

In relation to mRNA expressions, digestive and hepatic enzyme activity, growth performances of O. niloticus (6.07±0.07) was evaluated after feeding 56 days. Fish were fed six (6) experimental diets where fish oil (FO) supplements dietary oils; virgin coconut oil (VO) {3%FO+3%VO; FVO}, and corn oil (CO) {3%FO+3%CO; FCO}, 6%VO (VO), 6%CO (CO) and 6%VCO {3%VO+3%CO; VCO}. Those fed FCO recorded higher WG (1334.10±5.53) and SGR (4.76±0.01). Muscle lipid was significantly higher in group VO than CO and VCO whereas, it was significantly lower in the liver than the control group (P˂0.05). Dietary alternatives influenced digestive activities (amylase, lipase and trypsin) of which significant differences were not obtained between sections. Digestive enzymes lipase and pepsin were not significantly different at the posterior intestine. Liver receptors (FABP4 and PPAR-α) involved in fatty acid (FA) transport was not influenced, unlike CD36, G6PD and 6PGD. Although, the expression of PPAR-α gene was not different between groups, with the exception of group VCO, all other groups had no significant difference in expression levels of CD36, G6PD and 6PGD unlike FABP4. The study confirms that dietary vegetable lipids in partial replacement improve growth performances and maintain fish physiological functioning with preferences for utilization of 18: 3n-3 and 18: n-n9. Enzyme activity also positively correlates with growth rates and indicates good lipid metabolic activities and retention. As such, dietary alternatives influence liver enzyme activity and their mRNA expressions.