Abstract:
Objective The study aimed to investigate the impact of dietary lipid levels on the growth performance, body composition, and biochemical indices of juvenile Epinephelus fuscoguttatus ♀ × E. polyphekadion ♂ hybrid (approximately 7.16 g).
Methods An 8-week feeding trial was conducted, during which five isonitrogenous experimental diets containing 5.86%, 7.74%, 9.72%, 11.74%, and 13.68% dietary lipid (referred to as L1, L2, L3, L4, and L5, respectively) were formulated using fish oil as the primary lipid source.
Results 1) The optimal growth performance of juvenile E. fuscoguttatus ♀ × E. polyphekadion ♂ was observed at a dietary lipid level of 9.72%−11.74%. At this level, weight gain rate (WGR) and condition factor (CF) significantly increased (P<0.05), while feed conversion ratio (FCR) decreased significantly (P<0.05). 2) Dietary lipid levels did not significantly affect whole body and muscle moisture content (P>0.05). However, increasing dietary lipid levels led to a gradual increase in crude lipid content in both whole body and muscle, accompanied by a decrease in crude protein content in the whole body. 3) As dietary lipid levels increased, the levels of serum total protein (TP), albumin (ALB), and low-density lipoprotein (LDL) decreased, while serum glucose (GLU), triglycerides (TG), total cholesterol (TC), high-density lipoprotein (HDL), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activities increased. 4) Liver superoxide dismutase (SOD), catalase (CAT), and lysozyme (LZM) activities increased gradually with increasing dietary lipid levels up to 9.72%. However, CAT levels decreased when dietary lipid levels exceeded 9.72%, and SOD levels decreased when dietary lipid levels exceeded 11.74%. 5) Second-order polynomial regression analysis of WGR and FCR indicated that the optimal dietary lipid level for juvenile E. fuscoguttatus ♀ × E. polyphekadion ♂ were 9.77% and 10.39%, respectively.
Conclusion Under the conditions of this practical test, the recommended amount of fat in the diet of juvenile E. fuscoguttatus ♀ × E. polyphekadion ♂ was 9.77% − 10.39%.
Significance These results will be beneficial for the development of precise and efficient compound feed for juvenile E. fuscoguttatus ♀ × E. polyphekadion ♂.