Nutritional comparison and evaluation of two macroalgae, Sargassum ilicifulium and Padina australis, as partial substitution of fish meal in practical diets of Asian sea bass juvenile (Lates calcarifer)

Abstract

In the present study, Asian seabass (Lates calcarifer) with an initial mean body weight of 29.0 ± 1.0 g (in your materials and methods -31.0 g- which one is correct?) has been used as a model organism to establish the effects of dietary of Sargassum ilicifulium 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 gradually replaced by S. ilicifolium (SIM) and P. australis meal (PAM) at 6% (S6 & P6, 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 P6 group were significantly higher than those of the control group (P < 0.05). The P. australis dietary supplementation showed differences significantly in RBC, Hb, Hct, WBC to write in full during 1st mention, lymphocytes, neutrophils, and cholesterol contents (P < 0.05). It was observed that the levels of total protein and triglyceride in fish fed S. ilicifulium diet significantly increased compared to the other groups (P < 0.05). The skin mucus total immunoglobulin (Ig) and mucus lysozyme in the group fed on P6 were significantly higher than the control group (P < 0.05). The serum total Ig in the group fed on S6 was significantly higher with respect to the control group (P < 0.05). No significant differences were recorded in the contents of ACH50 in full during 1st. mention 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 P6 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.