Evaluation of Sargassum ilicofolium and Padina australis macroalgae dietary supplementation in juvenile Asian bass (Lates calcarifer).

The importance of seaweed as a possible supplement or an alternative protein source for Asian seabass (Lates calcarifer) has been recently recognized by several studies. In the present study, Asian seabass with an initial mean body weight of 29.00 ± 1.00 g has been used as a model organism to establish the effects of dietary Sargassum ilicifolium and Padina australis, as partial substitution of fish meal on growth performance, body composition, hemato-immunlogical response, digestive enzymes and immune and growth-related genes. Three diets were formulated in which fish meal (FM) was replaced by S. ilicifolium (SIM 6) and P. australis meal (PAM 6) at 6% (SIM 6 & PAM 6, respectively) whereas in the control diet (C), FM was not replaced with macroalgae. Asian seabass juveniles were fed for six weeks with experimental diets. At the end of the experiment, growth and feed utilization parameters in PAM 6 were significantly higher than those of the control group (p < 0.05). The P. australis dietary inclusion showed differences significantly in red blood cell (RBC), hemoglobin (Hb), hematocrit (Hct), white blood cell (WBC), lymphocytes, neutrophils, and cholesterol contents (p < 0.05). It was observed that the levels of total protein and triglyceride in fish fed SIM 6 significantly increased compared to the other groups (p < 0.05). The skin mucus total immunoglobulin (Ig) and mucus lysozyme in the group fed on PAM 6 were significantly higher than the control group (p < 0.05). The serum total Ig in the group fed on SIM 6 was significantly higher with respect to the control group (p < 0.05). No significant differences were recorded in the contents of the alternative complement pathway hemolytic activity (ACH50) and serum lysozyme among all treatment groups (p > 0.05). There was no significant difference in the contents of protease, lipase, and amylase among all treatments (p > 0.05). At the end of the experiment, the insulin-like growth factor I (IGF-I), lysozyme (LZ), and interleukin-1β (IL-1β) in liver organ in PAM 6 were significantly higher than other treatments (p < 0.05). The results obtained in the present study showed that P. australis as a partial replacement for fishmeal in the diet of Asian sea bass juveniles is beneficial for its immune system and growth performance stimulatory effects. [ABSTRACT FROM AUTHOR]