We have previously shown that a 2.5:2.5 (% over 100) ratio of soybean oil and Coconut oil is a superior replacement to a diet utilizing 5% soybean oil as the main source of lipids in a saline-tolerant Nile tilapia Oreochromis niloticus. In this study we explore the effects of a low-fat diet utilizing the same ratio of soybean oil to coconut oil. Three experimental diets were formulated with varying coconut oil:soybean oil ratio - Control (0:5); TrtB (2.5:2.5); and a low-fat diet TrtC (1:1). Overall growth performance and survival in response to the formulated diets were assessed after 56 days of culture. Survival rate among treatments were high and were not influenced by the different inclusion levels of coconut oil in the formulated diets. Growth performance values indicated significant differences (P>0.05) between Control and TrtB and TrtC (Figure 1).
The effect of coconut oil supplementation and low-fat diet on the expression and efficiency of growth-related genes was also investigated. Findings showed that inclusion of coconut oil in the diet produced statistically significant results on the expression of FADS2, ELOVL5, IGF, and Ghrelin genes. Body lipid composition and tissue morphology was also observed. The n-3 and n-6 levels were statistically different among treatments (P<0.05). Improved intestinal structure was observed on tilapia fed with coconut oil and growth in the dorsal muscle was observed in treatments that are enhanced by coconut oil. Overall, the low-fat diet (TrtC) seemed to exhibit similar beneficial properties as TrtB over the control diet.