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Abstract
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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 int
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