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Abstract
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This study investigated the effect of Sargassum angustifolium and Gracilaria pulvinata extracts as immunostimulant on the growth performance, blood index, chemical composition, antioxidantstatus and gut microbiota of rainbow trout (Onchorhynchus mykiss) fry. For this purpose, 540 fryof rainbow trout (mean initial weight 0.23±0.04 g) were distributed in 12 fiberglass tanks (20-l).The treatments were feeding trouts with experimental diets containing levels (500 mg kg-1) of extract Sargassum (SA), (500 mg kg-1) of extract Gracilaria (GL) and 250 mg kg-1of Sargassum 250 mg kg-1 Gracilaria (SA GL). The control diet was a commercial trout diet without seaweed extract. At the end of the 42 days no significant difference in growth parameters,protein, ash and moisture between treatments and control group (P > 0.05). However, lipid was significantly higher in fish fed of extract Gracilaria and Sargassum compared to control (P > 0.05). The seaweed extract-fed fish utilized efficiently the body lipid and suppressed bodyweight loss during starvation. No significant difference (P > 0.05) in serum total protein,creatinine alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase(ALP) and blood superoxide dismutase (SOD) activity were observed in all treatments. Whereas serum albumin, glutathione peroxidase (GPX) and catalase specific activity was higher in SA,GL and SA GL treatments compared to the control group (P > 0.05). The serum glucose and triglyceride level were significantly (P > 0.05) decreased in fish fed diets containing Sargassum and Gracilaria. ACH50 level was significantly (P > 0.05) increased in GL and SA GL treatments as compared SA and control group. Addition of Sargassum and Gracilaria extracts tofeed did not affecte total bacterial population, but increased lactobacillus bacteria levels (P > 0.05) in the intestine.Histological studies showed the natural structure of the intestinal tissue and liver cells in all treatments. These results r
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